1 00:00:12,080 --> 00:00:18,609 so semiconductors actually have 2 00:00:18,609 --> 00:00:18,619 so semiconductors actually have 3 00:00:18,619 --> 00:00:22,089 so semiconductors actually have electrical conductance they conduct the 4 00:00:22,089 --> 00:00:22,099 electrical conductance they conduct the 5 00:00:22,099 --> 00:00:24,670 electrical conductance they conduct the electricity much less than actually - 6 00:00:24,670 --> 00:00:24,680 electricity much less than actually - 7 00:00:24,680 --> 00:00:29,130 electricity much less than actually - compared to the metal we said but the 8 00:00:29,130 --> 00:00:29,140 compared to the metal we said but the 9 00:00:29,140 --> 00:00:30,970 compared to the metal we said but the explanations of the electrical 10 00:00:30,970 --> 00:00:30,980 explanations of the electrical 11 00:00:30,980 --> 00:00:32,709 explanations of the electrical conductivity used in the band Theory 12 00:00:32,709 --> 00:00:32,719 conductivity used in the band Theory 13 00:00:32,719 --> 00:00:37,959 conductivity used in the band Theory simply explained by small energy gap 14 00:00:37,959 --> 00:00:37,969 simply explained by small energy gap 15 00:00:37,969 --> 00:00:40,750 simply explained by small energy gap between the valence band and the 16 00:00:40,750 --> 00:00:40,760 between the valence band and the 17 00:00:40,760 --> 00:00:43,540 between the valence band and the conduction band for the semiconductors 18 00:00:43,540 --> 00:00:43,550 conduction band for the semiconductors 19 00:00:43,550 --> 00:00:46,090 conduction band for the semiconductors this is again for silicon germanium and 20 00:00:46,090 --> 00:00:46,100 this is again for silicon germanium and 21 00:00:46,100 --> 00:00:49,239 this is again for silicon germanium and tin they're all similar again and only 22 00:00:49,239 --> 00:00:49,249 tin they're all similar again and only 23 00:00:49,249 --> 00:00:52,060 tin they're all similar again and only the bandgap changes but if the band gap 24 00:00:52,060 --> 00:00:52,070 the bandgap changes but if the band gap 25 00:00:52,070 --> 00:00:56,079 the bandgap changes but if the band gap is much higher than 3 and so on that 26 00:00:56,079 --> 00:00:56,089 is much higher than 3 and so on that 27 00:00:56,089 --> 00:00:59,889 is much higher than 3 and so on that means that the compound will not behave 28 00:00:59,889 --> 00:00:59,899 means that the compound will not behave 29 00:00:59,899 --> 00:01:05,500 means that the compound will not behave as a semiconductors now there are two 30 00:01:05,500 --> 00:01:05,510 as a semiconductors now there are two 31 00:01:05,510 --> 00:01:08,710 as a semiconductors now there are two kinds of semiconductors one is called 32 00:01:08,710 --> 00:01:08,720 kinds of semiconductors one is called 33 00:01:08,720 --> 00:01:12,310 kinds of semiconductors one is called simply pure element semiconductors and 34 00:01:12,310 --> 00:01:12,320 simply pure element semiconductors and 35 00:01:12,320 --> 00:01:16,749 simply pure element semiconductors and these are all group for a actually time 36 00:01:16,749 --> 00:01:16,759 these are all group for a actually time 37 00:01:16,759 --> 00:01:18,490 these are all group for a actually time when they actually not semiconductor but 38 00:01:18,490 --> 00:01:18,500 when they actually not semiconductor but 39 00:01:18,500 --> 00:01:20,260 when they actually not semiconductor but you have to think about that consider 40 00:01:20,260 --> 00:01:20,270 you have to think about that consider 41 00:01:20,270 --> 00:01:25,569 you have to think about that consider that and all have four valence electrons 42 00:01:25,569 --> 00:01:25,579 that and all have four valence electrons 43 00:01:25,579 --> 00:01:27,959 that and all have four valence electrons but the silicon is a semiconductor 44 00:01:27,959 --> 00:01:27,969 but the silicon is a semiconductor 45 00:01:27,969 --> 00:01:31,120 but the silicon is a semiconductor germanium is a semiconductor tim is not 46 00:01:31,120 --> 00:01:31,130 germanium is a semiconductor tim is not 47 00:01:31,130 --> 00:01:35,010 germanium is a semiconductor tim is not almost metal actually but there are 48 00:01:35,010 --> 00:01:35,020 almost metal actually but there are 49 00:01:35,020 --> 00:01:38,529 almost metal actually but there are inorganic semiconductors or they are 50 00:01:38,529 --> 00:01:38,539 inorganic semiconductors or they are 51 00:01:38,539 --> 00:01:41,160 inorganic semiconductors or they are called compound semiconductors like 52 00:01:41,160 --> 00:01:41,170 called compound semiconductors like 53 00:01:41,170 --> 00:01:46,690 called compound semiconductors like arsenic gallium arsenide and others now 54 00:01:46,690 --> 00:01:46,700 arsenic gallium arsenide and others now 55 00:01:46,700 --> 00:01:52,870 arsenic gallium arsenide and others now these compound semiconductors made of 56 00:01:52,870 --> 00:01:52,880 these compound semiconductors made of 57 00:01:52,880 --> 00:01:56,910 these compound semiconductors made of two different types of element but the 58 00:01:56,910 --> 00:01:56,920 two different types of element but the 59 00:01:56,920 --> 00:01:59,410 two different types of element but the when you find out the number of valence 60 00:01:59,410 --> 00:01:59,420 when you find out the number of valence 61 00:01:59,420 --> 00:02:02,770 when you find out the number of valence electrons in these compound per atom it 62 00:02:02,770 --> 00:02:02,780 electrons in these compound per atom it 63 00:02:02,780 --> 00:02:06,429 electrons in these compound per atom it becomes equal to 4 so that simply means 64 00:02:06,429 --> 00:02:06,439 becomes equal to 4 so that simply means 65 00:02:06,439 --> 00:02:09,190 becomes equal to 4 so that simply means that these compound semiconductors or 66 00:02:09,190 --> 00:02:09,200 that these compound semiconductors or 67 00:02:09,200 --> 00:02:13,600 that these compound semiconductors or inorganic semiconductors do also make 68 00:02:13,600 --> 00:02:13,610 inorganic semiconductors do also make 69 00:02:13,610 --> 00:02:17,020 inorganic semiconductors do also make four bonds to the surrounding atoms 70 00:02:17,020 --> 00:02:17,030 four bonds to the surrounding atoms 71 00:02:17,030 --> 00:02:19,780 four bonds to the surrounding atoms other atoms and all of those four bonds 72 00:02:19,780 --> 00:02:19,790 other atoms and all of those four bonds 73 00:02:19,790 --> 00:02:23,320 other atoms and all of those four bonds contains two electrons so there are four 74 00:02:23,320 --> 00:02:23,330 contains two electrons so there are four 75 00:02:23,330 --> 00:02:24,250 contains two electrons so there are four electron 76 00:02:24,250 --> 00:02:24,260 electron 77 00:02:24,260 --> 00:02:30,039 electron / methyl or actually the the elements 78 00:02:30,039 --> 00:02:30,049 / methyl or actually the the elements 79 00:02:30,049 --> 00:02:32,949 / methyl or actually the the elements atom in these inorganic semiconductors 80 00:02:32,949 --> 00:02:32,959 atom in these inorganic semiconductors 81 00:02:32,959 --> 00:02:35,500 atom in these inorganic semiconductors like gallium arsenide now the gallium 82 00:02:35,500 --> 00:02:35,510 like gallium arsenide now the gallium 83 00:02:35,510 --> 00:02:38,280 like gallium arsenide now the gallium has one less electron that means three 84 00:02:38,280 --> 00:02:38,290 has one less electron that means three 85 00:02:38,290 --> 00:02:41,619 has one less electron that means three valence electrons but arsenic has five 86 00:02:41,619 --> 00:02:41,629 valence electrons but arsenic has five 87 00:02:41,629 --> 00:02:43,420 valence electrons but arsenic has five valence electrons so when you have 88 00:02:43,420 --> 00:02:43,430 valence electrons so when you have 89 00:02:43,430 --> 00:02:45,699 valence electrons so when you have gallium arsenide as a compound that 90 00:02:45,699 --> 00:02:45,709 gallium arsenide as a compound that 91 00:02:45,709 --> 00:02:47,289 gallium arsenide as a compound that means the number of valence electrons 92 00:02:47,289 --> 00:02:47,299 means the number of valence electrons 93 00:02:47,299 --> 00:02:50,470 means the number of valence electrons per atom becomes four same as silicon 94 00:02:50,470 --> 00:02:50,480 per atom becomes four same as silicon 95 00:02:50,480 --> 00:02:51,729 per atom becomes four same as silicon and germanium and so on 96 00:02:51,729 --> 00:02:51,739 and germanium and so on 97 00:02:51,739 --> 00:02:55,360 and germanium and so on and there are other than the gallium 98 00:02:55,360 --> 00:02:55,370 and there are other than the gallium 99 00:02:55,370 --> 00:02:58,119 and there are other than the gallium arsenide in fact conductors for example 100 00:02:58,119 --> 00:02:58,129 arsenide in fact conductors for example 101 00:02:58,129 --> 00:03:04,229 arsenide in fact conductors for example you can have the cadmium and the 102 00:03:04,229 --> 00:03:04,239 you can have the cadmium and the 103 00:03:04,239 --> 00:03:07,449 you can have the cadmium and the tellurium for example right collyrium 104 00:03:07,449 --> 00:03:07,459 tellurium for example right collyrium 105 00:03:07,459 --> 00:03:10,479 tellurium for example right collyrium has six valence electrons cadmium has 106 00:03:10,479 --> 00:03:10,489 has six valence electrons cadmium has 107 00:03:10,489 --> 00:03:12,699 has six valence electrons cadmium has two valence electrons and when you 108 00:03:12,699 --> 00:03:12,709 two valence electrons and when you 109 00:03:12,709 --> 00:03:14,500 two valence electrons and when you combine one cadmium and tellurium and 110 00:03:14,500 --> 00:03:14,510 combine one cadmium and tellurium and 111 00:03:14,510 --> 00:03:16,599 combine one cadmium and tellurium and make the semiconductor cadmium telluride 112 00:03:16,599 --> 00:03:16,609 make the semiconductor cadmium telluride 113 00:03:16,609 --> 00:03:19,360 make the semiconductor cadmium telluride then per number of valence electrons per 114 00:03:19,360 --> 00:03:19,370 then per number of valence electrons per 115 00:03:19,370 --> 00:03:27,369 then per number of valence electrons per atom becomes four right and so on now it 116 00:03:27,369 --> 00:03:27,379 atom becomes four right and so on now it 117 00:03:27,379 --> 00:03:33,720 atom becomes four right and so on now it is actually possible to adjust the 118 00:03:33,720 --> 00:03:33,730 is actually possible to adjust the 119 00:03:33,730 --> 00:03:38,220 is actually possible to adjust the electrical conductivity of element 120 00:03:38,220 --> 00:03:38,230 electrical conductivity of element 121 00:03:38,230 --> 00:03:46,050 electrical conductivity of element semiconductors by introducing impurities 122 00:03:46,050 --> 00:03:46,060 semiconductors by introducing impurities 123 00:03:46,060 --> 00:03:49,960 semiconductors by introducing impurities to the pure element consider a silicon 124 00:03:49,960 --> 00:03:49,970 to the pure element consider a silicon 125 00:03:49,970 --> 00:03:58,180 to the pure element consider a silicon for example and you can simply add very 126 00:03:58,180 --> 00:03:58,190 for example and you can simply add very 127 00:03:58,190 --> 00:04:02,339 for example and you can simply add very few number of phosphorus to the silicon 128 00:04:02,339 --> 00:04:02,349 few number of phosphorus to the silicon 129 00:04:02,349 --> 00:04:06,520 few number of phosphorus to the silicon pure silicon actually in parts per 130 00:04:06,520 --> 00:04:06,530 pure silicon actually in parts per 131 00:04:06,530 --> 00:04:10,750 pure silicon actually in parts per million level you know few parts per 132 00:04:10,750 --> 00:04:10,760 million level you know few parts per 133 00:04:10,760 --> 00:04:14,440 million level you know few parts per million level now the electrical 134 00:04:14,440 --> 00:04:14,450 million level now the electrical 135 00:04:14,450 --> 00:04:17,770 million level now the electrical conductivity of the silicon changes 136 00:04:17,770 --> 00:04:17,780 conductivity of the silicon changes 137 00:04:17,780 --> 00:04:19,259 conductivity of the silicon changes dramatically 138 00:04:19,259 --> 00:04:19,269 dramatically 139 00:04:19,269 --> 00:04:22,629 dramatically almost increases billion times million 140 00:04:22,629 --> 00:04:22,639 almost increases billion times million 141 00:04:22,639 --> 00:04:27,210 almost increases billion times million times just a few atoms and this 142 00:04:27,210 --> 00:04:27,220 times just a few atoms and this 143 00:04:27,220 --> 00:04:31,000 times just a few atoms and this controlled way of adding impurities to 144 00:04:31,000 --> 00:04:31,010 controlled way of adding impurities to 145 00:04:31,010 --> 00:04:33,820 controlled way of adding impurities to another pure element particularly these 146 00:04:33,820 --> 00:04:33,830 another pure element particularly these 147 00:04:33,830 --> 00:04:38,370 another pure element particularly these semiconductor elements is called doe 148 00:04:38,370 --> 00:04:38,380 semiconductor elements is called doe 149 00:04:38,380 --> 00:04:42,960 semiconductor elements is called doe so when we say doping means that we add 150 00:04:42,960 --> 00:04:42,970 so when we say doping means that we add 151 00:04:42,970 --> 00:04:46,180 so when we say doping means that we add small amount of impurities control 152 00:04:46,180 --> 00:04:46,190 small amount of impurities control 153 00:04:46,190 --> 00:04:50,790 small amount of impurities control amount of impurities to the pure element 154 00:04:50,790 --> 00:04:50,800 amount of impurities to the pure element 155 00:04:50,800 --> 00:04:55,650 amount of impurities to the pure element semiconductor and depending on what 156 00:04:55,650 --> 00:04:55,660 semiconductor and depending on what 157 00:04:55,660 --> 00:05:00,190 semiconductor and depending on what degree of conductance we want we can 158 00:05:00,190 --> 00:05:00,200 degree of conductance we want we can 159 00:05:00,200 --> 00:05:03,250 degree of conductance we want we can adjust that by simply adjusting the 160 00:05:03,250 --> 00:05:03,260 adjust that by simply adjusting the 161 00:05:03,260 --> 00:05:06,940 adjust that by simply adjusting the dopant atoms number of dopant atoms to 162 00:05:06,940 --> 00:05:06,950 dopant atoms number of dopant atoms to 163 00:05:06,950 --> 00:05:09,460 dopant atoms number of dopant atoms to the impurities now let's think about 164 00:05:09,460 --> 00:05:09,470 the impurities now let's think about 165 00:05:09,470 --> 00:05:12,670 the impurities now let's think about here as I said for example when you 166 00:05:12,670 --> 00:05:12,680 here as I said for example when you 167 00:05:12,680 --> 00:05:17,080 here as I said for example when you simply have a pure silicon and it's very 168 00:05:17,080 --> 00:05:17,090 simply have a pure silicon and it's very 169 00:05:17,090 --> 00:05:18,730 simply have a pure silicon and it's very very important to gain again as I said 170 00:05:18,730 --> 00:05:18,740 very important to gain again as I said 171 00:05:18,740 --> 00:05:23,440 very important to gain again as I said since very very small impurities changes 172 00:05:23,440 --> 00:05:23,450 since very very small impurities changes 173 00:05:23,450 --> 00:05:27,360 since very very small impurities changes the electrical conductivity tremendously 174 00:05:27,360 --> 00:05:27,370 the electrical conductivity tremendously 175 00:05:27,370 --> 00:05:30,220 the electrical conductivity tremendously so when you're making chips from the 176 00:05:30,220 --> 00:05:30,230 so when you're making chips from the 177 00:05:30,230 --> 00:05:34,270 so when you're making chips from the silicon that silicon has to be pure 178 00:05:34,270 --> 00:05:34,280 silicon that silicon has to be pure 179 00:05:34,280 --> 00:05:38,280 silicon that silicon has to be pure silicon actually it's called nain nain 180 00:05:38,280 --> 00:05:38,290 silicon actually it's called nain nain 181 00:05:38,290 --> 00:05:42,520 silicon actually it's called nain nain silicon means that the silicon used to 182 00:05:42,520 --> 00:05:42,530 silicon means that the silicon used to 183 00:05:42,530 --> 00:05:45,910 silicon means that the silicon used to make chips is ninety nine point nine 184 00:05:45,910 --> 00:05:45,920 make chips is ninety nine point nine 185 00:05:45,920 --> 00:05:48,700 make chips is ninety nine point nine nine nine nine nine nine nine nine nine 186 00:05:48,700 --> 00:05:48,710 nine nine nine nine nine nine nine nine 187 00:05:48,710 --> 00:05:52,900 nine nine nine nine nine nine nine nine percent pure because if it is not that 188 00:05:52,900 --> 00:05:52,910 percent pure because if it is not that 189 00:05:52,910 --> 00:05:55,180 percent pure because if it is not that pure than the electrical conductivity of 190 00:05:55,180 --> 00:05:55,190 pure than the electrical conductivity of 191 00:05:55,190 --> 00:05:58,240 pure than the electrical conductivity of the silicon is not what is simply 192 00:05:58,240 --> 00:05:58,250 the silicon is not what is simply 193 00:05:58,250 --> 00:06:01,630 the silicon is not what is simply required whatever it's used for so we 194 00:06:01,630 --> 00:06:01,640 required whatever it's used for so we 195 00:06:01,640 --> 00:06:03,640 required whatever it's used for so we have to be very very careful then when 196 00:06:03,640 --> 00:06:03,650 have to be very very careful then when 197 00:06:03,650 --> 00:06:05,980 have to be very very careful then when we have that pure silicon then we can 198 00:06:05,980 --> 00:06:05,990 we have that pure silicon then we can 199 00:06:05,990 --> 00:06:08,800 we have that pure silicon then we can adjust again if we control the amount of 200 00:06:08,800 --> 00:06:08,810 adjust again if we control the amount of 201 00:06:08,810 --> 00:06:12,130 adjust again if we control the amount of impurity that we add add some basis 202 00:06:12,130 --> 00:06:12,140 impurity that we add add some basis 203 00:06:12,140 --> 00:06:18,460 impurity that we add add some basis actually then we can obtain whatever the 204 00:06:18,460 --> 00:06:18,470 actually then we can obtain whatever the 205 00:06:18,470 --> 00:06:20,710 actually then we can obtain whatever the electrical conductivity we want to get 206 00:06:20,710 --> 00:06:20,720 electrical conductivity we want to get 207 00:06:20,720 --> 00:06:23,680 electrical conductivity we want to get from that mixture again and that is 208 00:06:23,680 --> 00:06:23,690 from that mixture again and that is 209 00:06:23,690 --> 00:06:26,680 from that mixture again and that is called doped silicon for example if you 210 00:06:26,680 --> 00:06:26,690 called doped silicon for example if you 211 00:06:26,690 --> 00:06:31,090 called doped silicon for example if you add into the silicon some impurities in 212 00:06:31,090 --> 00:06:31,100 add into the silicon some impurities in 213 00:06:31,100 --> 00:06:34,590 add into the silicon some impurities in this case suppose that we add phosphorus 214 00:06:34,590 --> 00:06:34,600 this case suppose that we add phosphorus 215 00:06:34,600 --> 00:06:37,440 this case suppose that we add phosphorus to the silicon that means we dope 216 00:06:37,440 --> 00:06:37,450 to the silicon that means we dope 217 00:06:37,450 --> 00:06:40,030 to the silicon that means we dope silicon pure silicon with phosphorus 218 00:06:40,030 --> 00:06:40,040 silicon pure silicon with phosphorus 219 00:06:40,040 --> 00:06:41,560 silicon pure silicon with phosphorus what really happens in the solid state 220 00:06:41,560 --> 00:06:41,570 what really happens in the solid state 221 00:06:41,570 --> 00:06:46,360 what really happens in the solid state the some of the silicon atoms in the 222 00:06:46,360 --> 00:06:46,370 the some of the silicon atoms in the 223 00:06:46,370 --> 00:06:49,750 the some of the silicon atoms in the lattice is replaced by the phosphorus 224 00:06:49,750 --> 00:06:49,760 lattice is replaced by the phosphorus 225 00:06:49,760 --> 00:06:50,299 lattice is replaced by the phosphorus atom 226 00:06:50,299 --> 00:06:50,309 atom 227 00:06:50,309 --> 00:06:53,269 atom but still that phosphors remember there 228 00:06:53,269 --> 00:06:53,279 but still that phosphors remember there 229 00:06:53,279 --> 00:06:56,119 but still that phosphors remember there are four silicon Iran it will make four 230 00:06:56,119 --> 00:06:56,129 are four silicon Iran it will make four 231 00:06:56,129 --> 00:07:00,409 are four silicon Iran it will make four buns right but the silicon has 4 valence 232 00:07:00,409 --> 00:07:00,419 buns right but the silicon has 4 valence 233 00:07:00,419 --> 00:07:02,809 buns right but the silicon has 4 valence electrons but the phosphorus has 5 234 00:07:02,809 --> 00:07:02,819 electrons but the phosphorus has 5 235 00:07:02,819 --> 00:07:05,469 electrons but the phosphorus has 5 valence electrons but when the 236 00:07:05,469 --> 00:07:05,479 valence electrons but when the 237 00:07:05,479 --> 00:07:08,599 valence electrons but when the phosphorus replaces the silicon in the 238 00:07:08,599 --> 00:07:08,609 phosphorus replaces the silicon in the 239 00:07:08,609 --> 00:07:10,969 phosphorus replaces the silicon in the lightest it only needs four electron to 240 00:07:10,969 --> 00:07:10,979 lightest it only needs four electron to 241 00:07:10,979 --> 00:07:13,249 lightest it only needs four electron to make for a coolant four covalent bonds 242 00:07:13,249 --> 00:07:13,259 make for a coolant four covalent bonds 243 00:07:13,259 --> 00:07:15,739 make for a coolant four covalent bonds so there is one excess electron there 244 00:07:15,739 --> 00:07:15,749 so there is one excess electron there 245 00:07:15,749 --> 00:07:18,769 so there is one excess electron there now where that electron goes that 246 00:07:18,769 --> 00:07:18,779 now where that electron goes that 247 00:07:18,779 --> 00:07:21,309 now where that electron goes that electron goes since this is all full 248 00:07:21,309 --> 00:07:21,319 electron goes since this is all full 249 00:07:21,319 --> 00:07:24,889 electron goes since this is all full right that electron goes into the 250 00:07:24,889 --> 00:07:24,899 right that electron goes into the 251 00:07:24,899 --> 00:07:28,249 right that electron goes into the conduction band here free electrons and 252 00:07:28,249 --> 00:07:28,259 conduction band here free electrons and 253 00:07:28,259 --> 00:07:31,459 conduction band here free electrons and that increases the electrical 254 00:07:31,459 --> 00:07:31,469 that increases the electrical 255 00:07:31,469 --> 00:07:34,909 that increases the electrical conductivity of the silicon increasing 256 00:07:34,909 --> 00:07:34,919 conductivity of the silicon increasing 257 00:07:34,919 --> 00:07:36,469 conductivity of the silicon increasing electrical conductivity of the silicon 258 00:07:36,469 --> 00:07:36,479 electrical conductivity of the silicon 259 00:07:36,479 --> 00:07:39,350 electrical conductivity of the silicon now depending on what degree of 260 00:07:39,350 --> 00:07:39,360 now depending on what degree of 261 00:07:39,360 --> 00:07:41,749 now depending on what degree of electrical conductivity we want from the 262 00:07:41,749 --> 00:07:41,759 electrical conductivity we want from the 263 00:07:41,759 --> 00:07:43,879 electrical conductivity we want from the silicon so we adjust the number of 264 00:07:43,879 --> 00:07:43,889 silicon so we adjust the number of 265 00:07:43,889 --> 00:07:45,469 silicon so we adjust the number of phosphorous atoms accordingly right 266 00:07:45,469 --> 00:07:45,479 phosphorous atoms accordingly right 267 00:07:45,479 --> 00:07:49,549 phosphorous atoms accordingly right accordingly and now we can also dope 268 00:07:49,549 --> 00:07:49,559 accordingly and now we can also dope 269 00:07:49,559 --> 00:07:53,119 accordingly and now we can also dope silicon with another atom which has less 270 00:07:53,119 --> 00:07:53,129 silicon with another atom which has less 271 00:07:53,129 --> 00:07:55,699 silicon with another atom which has less than four valence electrons for example 272 00:07:55,699 --> 00:07:55,709 than four valence electrons for example 273 00:07:55,709 --> 00:07:59,629 than four valence electrons for example if we simply dope the silicon with 274 00:07:59,629 --> 00:07:59,639 if we simply dope the silicon with 275 00:07:59,639 --> 00:08:02,889 if we simply dope the silicon with aluminium atoms very few aluminium atoms 276 00:08:02,889 --> 00:08:02,899 aluminium atoms very few aluminium atoms 277 00:08:02,899 --> 00:08:05,839 aluminium atoms very few aluminium atoms aluminium has three valence electrons 278 00:08:05,839 --> 00:08:05,849 aluminium has three valence electrons 279 00:08:05,849 --> 00:08:08,029 aluminium has three valence electrons the aluminium again in the crystal 280 00:08:08,029 --> 00:08:08,039 the aluminium again in the crystal 281 00:08:08,039 --> 00:08:10,129 the aluminium again in the crystal lattice and the lattice will replace the 282 00:08:10,129 --> 00:08:10,139 lattice and the lattice will replace the 283 00:08:10,139 --> 00:08:12,739 lattice and the lattice will replace the silicon and the aluminium will make four 284 00:08:12,739 --> 00:08:12,749 silicon and the aluminium will make four 285 00:08:12,749 --> 00:08:15,529 silicon and the aluminium will make four bonds with other silicones around in 286 00:08:15,529 --> 00:08:15,539 bonds with other silicones around in 287 00:08:15,539 --> 00:08:18,139 bonds with other silicones around in that crystal but there's only seven 288 00:08:18,139 --> 00:08:18,149 that crystal but there's only seven 289 00:08:18,149 --> 00:08:22,100 that crystal but there's only seven electrons there right for that four 290 00:08:22,100 --> 00:08:22,110 electrons there right for that four 291 00:08:22,110 --> 00:08:23,869 electrons there right for that four bonds what does that means that means 292 00:08:23,869 --> 00:08:23,879 bonds what does that means that means 293 00:08:23,879 --> 00:08:28,309 bonds what does that means that means that the valence band in that case will 294 00:08:28,309 --> 00:08:28,319 that the valence band in that case will 295 00:08:28,319 --> 00:08:31,159 that the valence band in that case will not be all full there's going to be some 296 00:08:31,159 --> 00:08:31,169 not be all full there's going to be some 297 00:08:31,169 --> 00:08:35,540 not be all full there's going to be some empty molecular orbitals here and that 298 00:08:35,540 --> 00:08:35,550 empty molecular orbitals here and that 299 00:08:35,550 --> 00:08:39,409 empty molecular orbitals here and that empty molecular orbitals will increase 300 00:08:39,409 --> 00:08:39,419 empty molecular orbitals will increase 301 00:08:39,419 --> 00:08:42,139 empty molecular orbitals will increase the electrical conductivity of the 302 00:08:42,139 --> 00:08:42,149 the electrical conductivity of the 303 00:08:42,149 --> 00:08:45,470 the electrical conductivity of the silicon right but in this case the 304 00:08:45,470 --> 00:08:45,480 silicon right but in this case the 305 00:08:45,480 --> 00:08:47,960 silicon right but in this case the mechanism of electric conductivity will 306 00:08:47,960 --> 00:08:47,970 mechanism of electric conductivity will 307 00:08:47,970 --> 00:08:50,059 mechanism of electric conductivity will be obtained by jumping the electron from 308 00:08:50,059 --> 00:08:50,069 be obtained by jumping the electron from 309 00:08:50,069 --> 00:08:51,619 be obtained by jumping the electron from one lattice point from to the other 310 00:08:51,619 --> 00:08:51,629 one lattice point from to the other 311 00:08:51,629 --> 00:08:53,660 one lattice point from to the other lattice points as the electron jumps 312 00:08:53,660 --> 00:08:53,670 lattice points as the electron jumps 313 00:08:53,670 --> 00:08:55,429 lattice points as the electron jumps from one lattice point to the other that 314 00:08:55,429 --> 00:08:55,439 from one lattice point to the other that 315 00:08:55,439 --> 00:08:57,410 from one lattice point to the other that means that the positive hole moves in 316 00:08:57,410 --> 00:08:57,420 means that the positive hole moves in 317 00:08:57,420 --> 00:08:59,419 means that the positive hole moves in one direction right in the opposite 318 00:08:59,419 --> 00:08:59,429 one direction right in the opposite 319 00:08:59,429 --> 00:09:01,759 one direction right in the opposite directions so the electrical 320 00:09:01,759 --> 00:09:01,769 directions so the electrical 321 00:09:01,769 --> 00:09:03,540 directions so the electrical conductivity increase 322 00:09:03,540 --> 00:09:03,550 conductivity increase 323 00:09:03,550 --> 00:09:07,500 conductivity increase is due to the positive holes that form 324 00:09:07,500 --> 00:09:07,510 is due to the positive holes that form 325 00:09:07,510 --> 00:09:11,700 is due to the positive holes that form in the valence band when we dope silicon 326 00:09:11,700 --> 00:09:11,710 in the valence band when we dope silicon 327 00:09:11,710 --> 00:09:15,360 in the valence band when we dope silicon with atoms which has less than four 328 00:09:15,360 --> 00:09:15,370 with atoms which has less than four 329 00:09:15,370 --> 00:09:20,340 with atoms which has less than four valence electrons so the semiconductor 330 00:09:20,340 --> 00:09:20,350 valence electrons so the semiconductor 331 00:09:20,350 --> 00:09:23,010 valence electrons so the semiconductor which is obtained by adding phosphorus 332 00:09:23,010 --> 00:09:23,020 which is obtained by adding phosphorus 333 00:09:23,020 --> 00:09:24,810 which is obtained by adding phosphorus for example to the silicon is called 334 00:09:24,810 --> 00:09:24,820 for example to the silicon is called 335 00:09:24,820 --> 00:09:27,210 for example to the silicon is called n-type semiconductors why it's all 336 00:09:27,210 --> 00:09:27,220 n-type semiconductors why it's all 337 00:09:27,220 --> 00:09:29,550 n-type semiconductors why it's all called anti because there is excess 338 00:09:29,550 --> 00:09:29,560 called anti because there is excess 339 00:09:29,560 --> 00:09:30,810 called anti because there is excess electron that means there's a negative 340 00:09:30,810 --> 00:09:30,820 electron that means there's a negative 341 00:09:30,820 --> 00:09:34,170 electron that means there's a negative charge that's why it's called n-type now 342 00:09:34,170 --> 00:09:34,180 charge that's why it's called n-type now 343 00:09:34,180 --> 00:09:37,140 charge that's why it's called n-type now the semiconductors which is obtained by 344 00:09:37,140 --> 00:09:37,150 the semiconductors which is obtained by 345 00:09:37,150 --> 00:09:40,110 the semiconductors which is obtained by doping aluminium to the silicon and we 346 00:09:40,110 --> 00:09:40,120 doping aluminium to the silicon and we 347 00:09:40,120 --> 00:09:42,480 doping aluminium to the silicon and we have simply partially filled valence 348 00:09:42,480 --> 00:09:42,490 have simply partially filled valence 349 00:09:42,490 --> 00:09:44,760 have simply partially filled valence band here and they're positive holes and 350 00:09:44,760 --> 00:09:44,770 band here and they're positive holes and 351 00:09:44,770 --> 00:09:46,950 band here and they're positive holes and it's called p-type that means we have 352 00:09:46,950 --> 00:09:46,960 it's called p-type that means we have 353 00:09:46,960 --> 00:09:49,530 it's called p-type that means we have less electron than required that we need 354 00:09:49,530 --> 00:09:49,540 less electron than required that we need 355 00:09:49,540 --> 00:09:52,260 less electron than required that we need and it's called p-type now when we 356 00:09:52,260 --> 00:09:52,270 and it's called p-type now when we 357 00:09:52,270 --> 00:09:55,130 and it's called p-type now when we combine this n-type and p-type 358 00:09:55,130 --> 00:09:55,140 combine this n-type and p-type 359 00:09:55,140 --> 00:09:58,020 combine this n-type and p-type semiconductors make a junction then we 360 00:09:58,020 --> 00:09:58,030 semiconductors make a junction then we 361 00:09:58,030 --> 00:10:01,500 semiconductors make a junction then we can make all kinds of devices actually 362 00:10:01,500 --> 00:10:01,510 can make all kinds of devices actually 363 00:10:01,510 --> 00:10:07,590 can make all kinds of devices actually and such as the diodes light emitting 364 00:10:07,590 --> 00:10:07,600 and such as the diodes light emitting 365 00:10:07,600 --> 00:10:16,740 and such as the diodes light emitting diodes and and others actually okay now 366 00:10:16,740 --> 00:10:16,750 diodes and and others actually okay now 367 00:10:16,750 --> 00:10:21,540 diodes and and others actually okay now the next solid compound that we will 368 00:10:21,540 --> 00:10:21,550 the next solid compound that we will 369 00:10:21,550 --> 00:10:24,690 the next solid compound that we will talk about is polymers now the polymers 370 00:10:24,690 --> 00:10:24,700 talk about is polymers now the polymers 371 00:10:24,700 --> 00:10:30,060 talk about is polymers now the polymers are actually long-chain molecules and 372 00:10:30,060 --> 00:10:30,070 are actually long-chain molecules and 373 00:10:30,070 --> 00:10:32,970 are actually long-chain molecules and the molecular weight of polymer 374 00:10:32,970 --> 00:10:32,980 the molecular weight of polymer 375 00:10:32,980 --> 00:10:36,570 the molecular weight of polymer molecules is sometimes goes up to 376 00:10:36,570 --> 00:10:36,580 molecules is sometimes goes up to 377 00:10:36,580 --> 00:10:39,600 molecules is sometimes goes up to million now remember again like 378 00:10:39,600 --> 00:10:39,610 million now remember again like 379 00:10:39,610 --> 00:10:42,510 million now remember again like molecular weight of water is eighteen 380 00:10:42,510 --> 00:10:42,520 molecular weight of water is eighteen 381 00:10:42,520 --> 00:10:46,830 molecular weight of water is eighteen right imagine the million and usually 382 00:10:46,830 --> 00:10:46,840 right imagine the million and usually 383 00:10:46,840 --> 00:10:51,690 right imagine the million and usually the polymers are obtained from the 384 00:10:51,690 --> 00:10:51,700 the polymers are obtained from the 385 00:10:51,700 --> 00:10:55,110 the polymers are obtained from the monomers the smallest unit smallest 386 00:10:55,110 --> 00:10:55,120 monomers the smallest unit smallest 387 00:10:55,120 --> 00:10:57,210 monomers the smallest unit smallest molecule putting them together as a 388 00:10:57,210 --> 00:10:57,220 molecule putting them together as a 389 00:10:57,220 --> 00:11:01,530 molecule putting them together as a matter of fact now there are two primary 390 00:11:01,530 --> 00:11:01,540 matter of fact now there are two primary 391 00:11:01,540 --> 00:11:03,600 matter of fact now there are two primary types of polymers it says here that 392 00:11:03,600 --> 00:11:03,610 types of polymers it says here that 393 00:11:03,610 --> 00:11:06,420 types of polymers it says here that means addition polymers and the 394 00:11:06,420 --> 00:11:06,430 means addition polymers and the 395 00:11:06,430 --> 00:11:08,820 means addition polymers and the condensation polymers addition polymers 396 00:11:08,820 --> 00:11:08,830 condensation polymers addition polymers 397 00:11:08,830 --> 00:11:10,710 condensation polymers addition polymers are formed when bond breaks and the 398 00:11:10,710 --> 00:11:10,720 are formed when bond breaks and the 399 00:11:10,720 --> 00:11:12,870 are formed when bond breaks and the electrons in that bond make two new 400 00:11:12,870 --> 00:11:12,880 electrons in that bond make two new 401 00:11:12,880 --> 00:11:14,760 electrons in that bond make two new bonds condensation polymers are formed 402 00:11:14,760 --> 00:11:14,770 bonds condensation polymers are formed 403 00:11:14,770 --> 00:11:16,350 bonds condensation polymers are formed when a small 404 00:11:16,350 --> 00:11:16,360 when a small 405 00:11:16,360 --> 00:11:18,850 when a small remove between two large molecules 406 00:11:18,850 --> 00:11:18,860 remove between two large molecules 407 00:11:18,860 --> 00:11:21,490 remove between two large molecules actually usually this removed molecules 408 00:11:21,490 --> 00:11:21,500 actually usually this removed molecules 409 00:11:21,500 --> 00:11:23,260 actually usually this removed molecules its water molecules now the next slide 410 00:11:23,260 --> 00:11:23,270 its water molecules now the next slide 411 00:11:23,270 --> 00:11:26,200 its water molecules now the next slide shows how we have the addition and 412 00:11:26,200 --> 00:11:26,210 shows how we have the addition and 413 00:11:26,210 --> 00:11:28,840 shows how we have the addition and condensation polymers addition polymers 414 00:11:28,840 --> 00:11:28,850 condensation polymers addition polymers 415 00:11:28,850 --> 00:11:31,870 condensation polymers addition polymers monomer is ethylene double bond here so 416 00:11:31,870 --> 00:11:31,880 monomer is ethylene double bond here so 417 00:11:31,880 --> 00:11:34,600 monomer is ethylene double bond here so when we get the ethylene together this 418 00:11:34,600 --> 00:11:34,610 when we get the ethylene together this 419 00:11:34,610 --> 00:11:37,330 when we get the ethylene together this bond opens up and then this carbon bonds 420 00:11:37,330 --> 00:11:37,340 bond opens up and then this carbon bonds 421 00:11:37,340 --> 00:11:39,280 bond opens up and then this carbon bonds to this one and that carbon bonds to the 422 00:11:39,280 --> 00:11:39,290 to this one and that carbon bonds to the 423 00:11:39,290 --> 00:11:41,740 to this one and that carbon bonds to the other one and then we have a long chain 424 00:11:41,740 --> 00:11:41,750 other one and then we have a long chain 425 00:11:41,750 --> 00:11:45,880 other one and then we have a long chain of polyethylene that is a polymer right 426 00:11:45,880 --> 00:11:45,890 of polyethylene that is a polymer right 427 00:11:45,890 --> 00:11:48,160 of polyethylene that is a polymer right and what very long chain of polymer 428 00:11:48,160 --> 00:11:48,170 and what very long chain of polymer 429 00:11:48,170 --> 00:11:51,970 and what very long chain of polymer polyethylene molecule here like this now 430 00:11:51,970 --> 00:11:51,980 polyethylene molecule here like this now 431 00:11:51,980 --> 00:11:56,020 polyethylene molecule here like this now when we simply combine this is for 432 00:11:56,020 --> 00:11:56,030 when we simply combine this is for 433 00:11:56,030 --> 00:11:58,780 when we simply combine this is for example a dybbuk acid and hexamine hexa 434 00:11:58,780 --> 00:11:58,790 example a dybbuk acid and hexamine hexa 435 00:11:58,790 --> 00:12:02,950 example a dybbuk acid and hexamine hexa diamine to form nylon and here this is 436 00:12:02,950 --> 00:12:02,960 diamine to form nylon and here this is 437 00:12:02,960 --> 00:12:05,440 diamine to form nylon and here this is one end of the molecule the amine part 438 00:12:05,440 --> 00:12:05,450 one end of the molecule the amine part 439 00:12:05,450 --> 00:12:09,310 one end of the molecule the amine part and this is the carboxylic acid acid 440 00:12:09,310 --> 00:12:09,320 and this is the carboxylic acid acid 441 00:12:09,320 --> 00:12:15,400 and this is the carboxylic acid acid part and when they polymerizes this o H 442 00:12:15,400 --> 00:12:15,410 part and when they polymerizes this o H 443 00:12:15,410 --> 00:12:16,660 part and when they polymerizes this o H and that H 444 00:12:16,660 --> 00:12:16,670 and that H 445 00:12:16,670 --> 00:12:19,450 and that H simply combines to form water and that 446 00:12:19,450 --> 00:12:19,460 simply combines to form water and that 447 00:12:19,460 --> 00:12:21,640 simply combines to form water and that water comes out and then we form a bond 448 00:12:21,640 --> 00:12:21,650 water comes out and then we form a bond 449 00:12:21,650 --> 00:12:23,380 water comes out and then we form a bond between this carbon and that nitrogen 450 00:12:23,380 --> 00:12:23,390 between this carbon and that nitrogen 451 00:12:23,390 --> 00:12:25,720 between this carbon and that nitrogen and this continues like this that kind 452 00:12:25,720 --> 00:12:25,730 and this continues like this that kind 453 00:12:25,730 --> 00:12:29,670 and this continues like this that kind of polymers or called condensation 454 00:12:29,670 --> 00:12:29,680 of polymers or called condensation 455 00:12:29,680 --> 00:12:32,170 of polymers or called condensation polymers or that polymerization is 456 00:12:32,170 --> 00:12:32,180 polymers or that polymerization is 457 00:12:32,180 --> 00:12:34,030 polymers or that polymerization is called condensation polymerization that 458 00:12:34,030 --> 00:12:34,040 called condensation polymerization that 459 00:12:34,040 --> 00:12:36,790 called condensation polymerization that means we form a bond between the smaller 460 00:12:36,790 --> 00:12:36,800 means we form a bond between the smaller 461 00:12:36,800 --> 00:12:39,610 means we form a bond between the smaller molecules by removing another small 462 00:12:39,610 --> 00:12:39,620 molecules by removing another small 463 00:12:39,620 --> 00:12:41,650 molecules by removing another small molecule in this case water as a matter 464 00:12:41,650 --> 00:12:41,660 molecule in this case water as a matter 465 00:12:41,660 --> 00:12:46,720 molecule in this case water as a matter of fact now these are the examples of 466 00:12:46,720 --> 00:12:46,730 of fact now these are the examples of 467 00:12:46,730 --> 00:12:49,780 of fact now these are the examples of some common polymers that we use there 468 00:12:49,780 --> 00:12:49,790 some common polymers that we use there 469 00:12:49,790 --> 00:12:55,150 some common polymers that we use there almost everywhere in our life and this 470 00:12:55,150 --> 00:12:55,160 almost everywhere in our life and this 471 00:12:55,160 --> 00:12:57,400 almost everywhere in our life and this is the most common one again 472 00:12:57,400 --> 00:12:57,410 is the most common one again 473 00:12:57,410 --> 00:13:00,990 is the most common one again polyethylene like this and this is the 474 00:13:00,990 --> 00:13:01,000 polyethylene like this and this is the 475 00:13:01,000 --> 00:13:06,210 polyethylene like this and this is the polypropylene again and we have there 476 00:13:06,210 --> 00:13:06,220 polypropylene again and we have there 477 00:13:06,220 --> 00:13:08,710 polypropylene again and we have there there is a double bond here the monomers 478 00:13:08,710 --> 00:13:08,720 there is a double bond here the monomers 479 00:13:08,720 --> 00:13:13,720 there is a double bond here the monomers is poor polypropylene and the monomers 480 00:13:13,720 --> 00:13:13,730 is poor polypropylene and the monomers 481 00:13:13,730 --> 00:13:18,670 is poor polypropylene and the monomers is properly propene I guess 214 and this 482 00:13:18,670 --> 00:13:18,680 is properly propene I guess 214 and this 483 00:13:18,680 --> 00:13:22,390 is properly propene I guess 214 and this is another polystyrene and you got that 484 00:13:22,390 --> 00:13:22,400 is another polystyrene and you got that 485 00:13:22,400 --> 00:13:26,860 is another polystyrene and you got that like this and we have also hole even a 486 00:13:26,860 --> 00:13:26,870 like this and we have also hole even a 487 00:13:26,870 --> 00:13:29,920 like this and we have also hole even a vinyl chloride this is where we use 488 00:13:29,920 --> 00:13:29,930 vinyl chloride this is where we use 489 00:13:29,930 --> 00:13:32,860 vinyl chloride this is where we use for example polyvinyl chloride in pipe 490 00:13:32,860 --> 00:13:32,870 for example polyvinyl chloride in pipe 491 00:13:32,870 --> 00:13:34,810 for example polyvinyl chloride in pipe fitting Plumbing's and things like that 492 00:13:34,810 --> 00:13:34,820 fitting Plumbing's and things like that 493 00:13:34,820 --> 00:13:39,180 fitting Plumbing's and things like that now these are the conversation polymers 494 00:13:39,180 --> 00:13:39,190 now these are the conversation polymers 495 00:13:39,190 --> 00:13:42,760 now these are the conversation polymers most common one I guess is the nylon 496 00:13:42,760 --> 00:13:42,770 most common one I guess is the nylon 497 00:13:42,770 --> 00:13:46,930 most common one I guess is the nylon here that's poly urethane this one is 498 00:13:46,930 --> 00:13:46,940 here that's poly urethane this one is 499 00:13:46,940 --> 00:13:50,200 here that's poly urethane this one is polyurethane and polyesters nylon this 500 00:13:50,200 --> 00:13:50,210 polyurethane and polyesters nylon this 501 00:13:50,210 --> 00:13:53,320 polyurethane and polyesters nylon this is the first conversation polymers 502 00:13:53,320 --> 00:13:53,330 is the first conversation polymers 503 00:13:53,330 --> 00:13:55,960 is the first conversation polymers almost and polar carbonates and this is 504 00:13:55,960 --> 00:13:55,970 almost and polar carbonates and this is 505 00:13:55,970 --> 00:13:58,150 almost and polar carbonates and this is where we use them as a matter of fact 506 00:13:58,150 --> 00:13:58,160 where we use them as a matter of fact 507 00:13:58,160 --> 00:14:02,770 where we use them as a matter of fact now remember again the cellulose and 508 00:14:02,770 --> 00:14:02,780 now remember again the cellulose and 509 00:14:02,780 --> 00:14:07,240 now remember again the cellulose and starch which is present in particularly 510 00:14:07,240 --> 00:14:07,250 starch which is present in particularly 511 00:14:07,250 --> 00:14:10,780 starch which is present in particularly plants and the proteins which is present 512 00:14:10,780 --> 00:14:10,790 plants and the proteins which is present 513 00:14:10,790 --> 00:14:15,460 plants and the proteins which is present both in plant and the animals and human 514 00:14:15,460 --> 00:14:15,470 both in plant and the animals and human 515 00:14:15,470 --> 00:14:18,990 both in plant and the animals and human beings are also polymers they're 516 00:14:18,990 --> 00:14:19,000 beings are also polymers they're 517 00:14:19,000 --> 00:14:21,940 beings are also polymers they're long-chain big molecules very big 518 00:14:21,940 --> 00:14:21,950 long-chain big molecules very big 519 00:14:21,950 --> 00:14:24,070 long-chain big molecules very big molecules so the polymers are really 520 00:14:24,070 --> 00:14:24,080 molecules so the polymers are really 521 00:14:24,080 --> 00:14:30,580 molecules so the polymers are really very important in fact to make Goods out 522 00:14:30,580 --> 00:14:30,590 very important in fact to make Goods out 523 00:14:30,590 --> 00:14:32,370 very important in fact to make Goods out of them 524 00:14:32,370 --> 00:14:32,380 of them 525 00:14:32,380 --> 00:14:34,900 of them devices and things like that and they're 526 00:14:34,900 --> 00:14:34,910 devices and things like that and they're 527 00:14:34,910 --> 00:14:37,480 devices and things like that and they're also important biologically to because 528 00:14:37,480 --> 00:14:37,490 also important biologically to because 529 00:14:37,490 --> 00:14:41,320 also important biologically to because most of those biological molecules like 530 00:14:41,320 --> 00:14:41,330 most of those biological molecules like 531 00:14:41,330 --> 00:14:46,530 most of those biological molecules like proteins are enzymes mostly are polymers 532 00:14:46,530 --> 00:14:46,540 proteins are enzymes mostly are polymers 533 00:14:46,540 --> 00:14:50,290 proteins are enzymes mostly are polymers okay now the bulk properties of polymers 534 00:14:50,290 --> 00:14:50,300 okay now the bulk properties of polymers 535 00:14:50,300 --> 00:14:52,330 okay now the bulk properties of polymers again the molecules are not straight 536 00:14:52,330 --> 00:14:52,340 again the molecules are not straight 537 00:14:52,340 --> 00:14:54,940 again the molecules are not straight lines the longer the chain the more 538 00:14:54,940 --> 00:14:54,950 lines the longer the chain the more 539 00:14:54,950 --> 00:14:57,640 lines the longer the chain the more twists in the twisting happens it says 540 00:14:57,640 --> 00:14:57,650 twists in the twisting happens it says 541 00:14:57,650 --> 00:15:00,160 twists in the twisting happens it says chains can have variety of lengths and 542 00:15:00,160 --> 00:15:00,170 chains can have variety of lengths and 543 00:15:00,170 --> 00:15:01,930 chains can have variety of lengths and therefore a variety of molecular weights 544 00:15:01,930 --> 00:15:01,940 therefore a variety of molecular weights 545 00:15:01,940 --> 00:15:05,560 therefore a variety of molecular weights again you see when you polymerize the 546 00:15:05,560 --> 00:15:05,570 again you see when you polymerize the 547 00:15:05,570 --> 00:15:08,470 again you see when you polymerize the monomer to form polymers molecule they 548 00:15:08,470 --> 00:15:08,480 monomer to form polymers molecule they 549 00:15:08,480 --> 00:15:12,520 monomer to form polymers molecule they will not be all the same length that 550 00:15:12,520 --> 00:15:12,530 will not be all the same length that 551 00:15:12,530 --> 00:15:13,900 will not be all the same length that means they will not be all the same 552 00:15:13,900 --> 00:15:13,910 means they will not be all the same 553 00:15:13,910 --> 00:15:16,000 means they will not be all the same molecular weight so there is always you 554 00:15:16,000 --> 00:15:16,010 molecular weight so there is always you 555 00:15:16,010 --> 00:15:18,250 molecular weight so there is always you know different molecular weight polymer 556 00:15:18,250 --> 00:15:18,260 know different molecular weight polymer 557 00:15:18,260 --> 00:15:20,230 know different molecular weight polymer molecules present there and that also 558 00:15:20,230 --> 00:15:20,240 molecules present there and that also 559 00:15:20,240 --> 00:15:22,000 molecules present there and that also affects the properties of bulk 560 00:15:22,000 --> 00:15:22,010 affects the properties of bulk 561 00:15:22,010 --> 00:15:23,560 affects the properties of bulk properties of the polymers too as a 562 00:15:23,560 --> 00:15:23,570 properties of the polymers too as a 563 00:15:23,570 --> 00:15:26,680 properties of the polymers too as a matter of fact now material they can be 564 00:15:26,680 --> 00:15:26,690 matter of fact now material they can be 565 00:15:26,690 --> 00:15:29,890 matter of fact now material they can be very flexible or can be hard actually 566 00:15:29,890 --> 00:15:29,900 very flexible or can be hard actually 567 00:15:29,900 --> 00:15:34,090 very flexible or can be hard actually they're usually flexible now there are 568 00:15:34,090 --> 00:15:34,100 they're usually flexible now there are 569 00:15:34,100 --> 00:15:37,540 they're usually flexible now there are actually strong range order and can lead 570 00:15:37,540 --> 00:15:37,550 actually strong range order and can lead 571 00:15:37,550 --> 00:15:40,720 actually strong range order and can lead to crystalline ik crystallinity in solid 572 00:15:40,720 --> 00:15:40,730 to crystalline ik crystallinity in solid 573 00:15:40,730 --> 00:15:42,730 to crystalline ik crystallinity in solid now this crystallinity again has 574 00:15:42,730 --> 00:15:42,740 now this crystallinity again has 575 00:15:42,740 --> 00:15:43,689 now this crystallinity again has followed 576 00:15:43,689 --> 00:15:43,699 followed 577 00:15:43,699 --> 00:15:46,599 followed suppose that long-chain molecules 578 00:15:46,599 --> 00:15:46,609 suppose that long-chain molecules 579 00:15:46,609 --> 00:15:50,019 suppose that long-chain molecules somewhere have hydrogen bonding or some 580 00:15:50,019 --> 00:15:50,029 somewhere have hydrogen bonding or some 581 00:15:50,029 --> 00:15:53,859 somewhere have hydrogen bonding or some polarity right so when we have those 582 00:15:53,859 --> 00:15:53,869 polarity right so when we have those 583 00:15:53,869 --> 00:15:58,030 polarity right so when we have those chains of polymers they will pack in 584 00:15:58,030 --> 00:15:58,040 chains of polymers they will pack in 585 00:15:58,040 --> 00:16:00,789 chains of polymers they will pack in this fashion to get very nice packing 586 00:16:00,789 --> 00:16:00,799 this fashion to get very nice packing 587 00:16:00,799 --> 00:16:03,099 this fashion to get very nice packing like here because there's an attraction 588 00:16:03,099 --> 00:16:03,109 like here because there's an attraction 589 00:16:03,109 --> 00:16:05,889 like here because there's an attraction between the chains here through the 590 00:16:05,889 --> 00:16:05,899 between the chains here through the 591 00:16:05,899 --> 00:16:08,530 between the chains here through the intermolecular forces and these points 592 00:16:08,530 --> 00:16:08,540 intermolecular forces and these points 593 00:16:08,540 --> 00:16:10,720 intermolecular forces and these points are crystalline and this is called 594 00:16:10,720 --> 00:16:10,730 are crystalline and this is called 595 00:16:10,730 --> 00:16:13,090 are crystalline and this is called crystallinity when he increased the 596 00:16:13,090 --> 00:16:13,100 crystallinity when he increased the 597 00:16:13,100 --> 00:16:14,949 crystallinity when he increased the crystallinity that means the structures 598 00:16:14,949 --> 00:16:14,959 crystallinity that means the structures 599 00:16:14,959 --> 00:16:17,109 crystallinity that means the structures in the polymer which looks like this you 600 00:16:17,109 --> 00:16:17,119 in the polymer which looks like this you 601 00:16:17,119 --> 00:16:20,979 in the polymer which looks like this you know regional sort of regularities in 602 00:16:20,979 --> 00:16:20,989 know regional sort of regularities in 603 00:16:20,989 --> 00:16:24,759 know regional sort of regularities in orange its short-range regularities the 604 00:16:24,759 --> 00:16:24,769 orange its short-range regularities the 605 00:16:24,769 --> 00:16:27,729 orange its short-range regularities the properties of the polymer changes again 606 00:16:27,729 --> 00:16:27,739 properties of the polymer changes again 607 00:16:27,739 --> 00:16:37,629 properties of the polymer changes again dramatically now this is isoprene poly 608 00:16:37,629 --> 00:16:37,639 dramatically now this is isoprene poly 609 00:16:37,639 --> 00:16:40,960 dramatically now this is isoprene poly isoprene which is natural rubber again 610 00:16:40,960 --> 00:16:40,970 isoprene which is natural rubber again 611 00:16:40,970 --> 00:16:44,289 isoprene which is natural rubber again now natural rubber itself is very 612 00:16:44,289 --> 00:16:44,299 now natural rubber itself is very 613 00:16:44,299 --> 00:16:46,539 now natural rubber itself is very elastic is not very strong is not really 614 00:16:46,539 --> 00:16:46,549 elastic is not very strong is not really 615 00:16:46,549 --> 00:16:51,609 elastic is not very strong is not really that stable but when you simply bind the 616 00:16:51,609 --> 00:16:51,619 that stable but when you simply bind the 617 00:16:51,619 --> 00:16:55,539 that stable but when you simply bind the natural rubber polymer chains with 618 00:16:55,539 --> 00:16:55,549 natural rubber polymer chains with 619 00:16:55,549 --> 00:16:59,259 natural rubber polymer chains with cross-linking with sulfur this is called 620 00:16:59,259 --> 00:16:59,269 cross-linking with sulfur this is called 621 00:16:59,269 --> 00:17:02,919 cross-linking with sulfur this is called vulcanization actually and the rubber or 622 00:17:02,919 --> 00:17:02,929 vulcanization actually and the rubber or 623 00:17:02,929 --> 00:17:05,199 vulcanization actually and the rubber or I should say that polymer which is the 624 00:17:05,199 --> 00:17:05,209 I should say that polymer which is the 625 00:17:05,209 --> 00:17:08,610 I should say that polymer which is the rubber as a matter of fact has very very 626 00:17:08,610 --> 00:17:08,620 rubber as a matter of fact has very very 627 00:17:08,620 --> 00:17:11,769 rubber as a matter of fact has very very good properties to be used in industry 628 00:17:11,769 --> 00:17:11,779 good properties to be used in industry 629 00:17:11,779 --> 00:17:14,399 good properties to be used in industry like tires for example are all 630 00:17:14,399 --> 00:17:14,409 like tires for example are all 631 00:17:14,409 --> 00:17:18,370 like tires for example are all vulcanized rubber as a matter of fact so 632 00:17:18,370 --> 00:17:18,380 vulcanized rubber as a matter of fact so 633 00:17:18,380 --> 00:17:21,970 vulcanized rubber as a matter of fact so you simply bind the change together and 634 00:17:21,970 --> 00:17:21,980 you simply bind the change together and 635 00:17:21,980 --> 00:17:25,899 you simply bind the change together and the bulk properties changes the strength 636 00:17:25,899 --> 00:17:25,909 the bulk properties changes the strength 637 00:17:25,909 --> 00:17:27,490 the bulk properties changes the strength of those boiling points and other things 638 00:17:27,490 --> 00:17:27,500 of those boiling points and other things 639 00:17:27,500 --> 00:17:29,529 of those boiling points and other things that changes drama dramatically also - 640 00:17:29,529 --> 00:17:29,539 that changes drama dramatically also - 641 00:17:29,539 --> 00:17:32,070 that changes drama dramatically also - you get much much better stronger 642 00:17:32,070 --> 00:17:32,080 you get much much better stronger 643 00:17:32,080 --> 00:17:35,710 you get much much better stronger polymers by simply cross linking those 644 00:17:35,710 --> 00:17:35,720 polymers by simply cross linking those 645 00:17:35,720 --> 00:17:38,350 polymers by simply cross linking those polymer chains in this case why sulfur 646 00:17:38,350 --> 00:17:38,360 polymer chains in this case why sulfur 647 00:17:38,360 --> 00:17:40,440 polymer chains in this case why sulfur if you do it by sulfur it is called 648 00:17:40,440 --> 00:17:40,450 if you do it by sulfur it is called 649 00:17:40,450 --> 00:17:42,730 if you do it by sulfur it is called vulcanization actually this process is 650 00:17:42,730 --> 00:17:42,740 vulcanization actually this process is 651 00:17:42,740 --> 00:17:47,649 vulcanization actually this process is called organizations now not all 652 00:17:47,649 --> 00:17:47,659 called organizations now not all 653 00:17:47,659 --> 00:17:53,100 called organizations now not all materials these are simply the 654 00:17:53,100 --> 00:17:53,110 materials these are simply the 655 00:17:53,110 --> 00:17:56,139 materials these are simply the substances that has the particle size 656 00:17:56,139 --> 00:17:56,149 substances that has the particle size 657 00:17:56,149 --> 00:17:57,110 substances that has the particle size between 658 00:17:57,110 --> 00:17:57,120 between 659 00:17:57,120 --> 00:18:00,830 between and hundred nanometers so when the 660 00:18:00,830 --> 00:18:00,840 and hundred nanometers so when the 661 00:18:00,840 --> 00:18:04,700 and hundred nanometers so when the particle size of solids is between 1 and 662 00:18:04,700 --> 00:18:04,710 particle size of solids is between 1 and 663 00:18:04,710 --> 00:18:08,480 particle size of solids is between 1 and hundred nanometers the properties of the 664 00:18:08,480 --> 00:18:08,490 hundred nanometers the properties of the 665 00:18:08,490 --> 00:18:12,080 hundred nanometers the properties of the solid again changes drastically changes 666 00:18:12,080 --> 00:18:12,090 solid again changes drastically changes 667 00:18:12,090 --> 00:18:15,260 solid again changes drastically changes drastically and those substances are 668 00:18:15,260 --> 00:18:15,270 drastically and those substances are 669 00:18:15,270 --> 00:18:18,020 drastically and those substances are called nano materials and they're great 670 00:18:18,020 --> 00:18:18,030 called nano materials and they're great 671 00:18:18,030 --> 00:18:20,750 called nano materials and they're great research is going on these nano 672 00:18:20,750 --> 00:18:20,760 research is going on these nano 673 00:18:20,760 --> 00:18:22,700 research is going on these nano materials as a matter of fact because 674 00:18:22,700 --> 00:18:22,710 materials as a matter of fact because 675 00:18:22,710 --> 00:18:27,260 materials as a matter of fact because people are after simply trying to make 676 00:18:27,260 --> 00:18:27,270 people are after simply trying to make 677 00:18:27,270 --> 00:18:32,690 people are after simply trying to make devices that molecular size small by 678 00:18:32,690 --> 00:18:32,700 devices that molecular size small by 679 00:18:32,700 --> 00:18:36,200 devices that molecular size small by using these nano materials nano 680 00:18:36,200 --> 00:18:36,210 using these nano materials nano 681 00:18:36,210 --> 00:18:40,910 using these nano materials nano materials now uh for example if we 682 00:18:40,910 --> 00:18:40,920 materials now uh for example if we 683 00:18:40,920 --> 00:18:43,940 materials now uh for example if we consider the semiconductors and metals 684 00:18:43,940 --> 00:18:43,950 consider the semiconductors and metals 685 00:18:43,950 --> 00:18:49,370 consider the semiconductors and metals in fact as nano scale small molecules 686 00:18:49,370 --> 00:18:49,380 in fact as nano scale small molecules 687 00:18:49,380 --> 00:18:52,340 in fact as nano scale small molecules have discrete orbitals macro molecule 688 00:18:52,340 --> 00:18:52,350 have discrete orbitals macro molecule 689 00:18:52,350 --> 00:18:55,400 have discrete orbitals macro molecule materials have bends where does it 690 00:18:55,400 --> 00:18:55,410 materials have bends where does it 691 00:18:55,410 --> 00:18:59,600 materials have bends where does it switch over now the things is again as 692 00:18:59,600 --> 00:18:59,610 switch over now the things is again as 693 00:18:59,610 --> 00:19:02,840 switch over now the things is again as follow the bitch simply says when we 694 00:19:02,840 --> 00:19:02,850 follow the bitch simply says when we 695 00:19:02,850 --> 00:19:07,940 follow the bitch simply says when we have two atoms or small molecule we can 696 00:19:07,940 --> 00:19:07,950 have two atoms or small molecule we can 697 00:19:07,950 --> 00:19:11,000 have two atoms or small molecule we can simply form the molecular orbitals and 698 00:19:11,000 --> 00:19:11,010 simply form the molecular orbitals and 699 00:19:11,010 --> 00:19:13,250 simply form the molecular orbitals and these molecular orbitals are very 700 00:19:13,250 --> 00:19:13,260 these molecular orbitals are very 701 00:19:13,260 --> 00:19:16,220 these molecular orbitals are very localized only for those if it's made 702 00:19:16,220 --> 00:19:16,230 localized only for those if it's made 703 00:19:16,230 --> 00:19:17,930 localized only for those if it's made from two atoms only if on those two 704 00:19:17,930 --> 00:19:17,940 from two atoms only if on those two 705 00:19:17,940 --> 00:19:20,180 from two atoms only if on those two atoms we put the electrons in bonding 706 00:19:20,180 --> 00:19:20,190 atoms we put the electrons in bonding 707 00:19:20,190 --> 00:19:22,040 atoms we put the electrons in bonding anti-bonding molecular orbitals and so 708 00:19:22,040 --> 00:19:22,050 anti-bonding molecular orbitals and so 709 00:19:22,050 --> 00:19:28,150 anti-bonding molecular orbitals and so on now when we have a chunk of metal or 710 00:19:28,150 --> 00:19:28,160 on now when we have a chunk of metal or 711 00:19:28,160 --> 00:19:36,610 on now when we have a chunk of metal or semiconductor now we have bends right 712 00:19:36,610 --> 00:19:36,620 semiconductor now we have bends right 713 00:19:36,620 --> 00:19:39,049 semiconductor now we have bends right that means we have molecular orbitals 714 00:19:39,049 --> 00:19:39,059 that means we have molecular orbitals 715 00:19:39,059 --> 00:19:42,400 that means we have molecular orbitals which are very closely spaced 716 00:19:42,400 --> 00:19:42,410 which are very closely spaced 717 00:19:42,410 --> 00:19:45,380 which are very closely spaced energy-wise very closely spaced and we 718 00:19:45,380 --> 00:19:45,390 energy-wise very closely spaced and we 719 00:19:45,390 --> 00:19:47,360 energy-wise very closely spaced and we call them bands and the question here 720 00:19:47,360 --> 00:19:47,370 call them bands and the question here 721 00:19:47,370 --> 00:19:55,669 call them bands and the question here says when the local molecular orbital 722 00:19:55,669 --> 00:19:55,679 says when the local molecular orbital 723 00:19:55,679 --> 00:20:00,110 says when the local molecular orbital approach shifts over to the bent 724 00:20:00,110 --> 00:20:00,120 approach shifts over to the bent 725 00:20:00,120 --> 00:20:05,030 approach shifts over to the bent approach band Theory what size right 726 00:20:05,030 --> 00:20:05,040 approach band Theory what size right 727 00:20:05,040 --> 00:20:07,990 approach band Theory what size right because if you consider single molecule 728 00:20:07,990 --> 00:20:08,000 because if you consider single molecule 729 00:20:08,000 --> 00:20:10,770 because if you consider single molecule the properties of that single molecule 730 00:20:10,770 --> 00:20:10,780 the properties of that single molecule 731 00:20:10,780 --> 00:20:13,620 the properties of that single molecule is not same as the properties of the 732 00:20:13,620 --> 00:20:13,630 is not same as the properties of the 733 00:20:13,630 --> 00:20:15,930 is not same as the properties of the bulk which you have all your molecules 734 00:20:15,930 --> 00:20:15,940 bulk which you have all your molecules 735 00:20:15,940 --> 00:20:20,900 bulk which you have all your molecules together so and here it says the theory 736 00:20:20,900 --> 00:20:20,910 together so and here it says the theory 737 00:20:20,910 --> 00:20:24,450 together so and here it says the theory calculation tells you that when the size 738 00:20:24,450 --> 00:20:24,460 calculation tells you that when the size 739 00:20:24,460 --> 00:20:28,890 calculation tells you that when the size of the crystal or that particle is about 740 00:20:28,890 --> 00:20:28,900 of the crystal or that particle is about 741 00:20:28,900 --> 00:20:32,670 of the crystal or that particle is about 10 nanometers or beyond that 10 742 00:20:32,670 --> 00:20:32,680 10 nanometers or beyond that 10 743 00:20:32,680 --> 00:20:37,520 10 nanometers or beyond that 10 nanometers then we go to the bent 744 00:20:37,520 --> 00:20:37,530 nanometers then we go to the bent 745 00:20:37,530 --> 00:20:40,110 nanometers then we go to the bent structure that means we consider that as 746 00:20:40,110 --> 00:20:40,120 structure that means we consider that as 747 00:20:40,120 --> 00:20:43,860 structure that means we consider that as a bulk again right and that that range 748 00:20:43,860 --> 00:20:43,870 a bulk again right and that that range 749 00:20:43,870 --> 00:20:46,050 a bulk again right and that that range again again about 10 nanometer sized 750 00:20:46,050 --> 00:20:46,060 again again about 10 nanometer sized 751 00:20:46,060 --> 00:20:48,800 again again about 10 nanometer sized particles there are very unusual 752 00:20:48,800 --> 00:20:48,810 particles there are very unusual 753 00:20:48,810 --> 00:20:53,870 particles there are very unusual properties that those particle shows and 754 00:20:53,870 --> 00:20:53,880 properties that those particle shows and 755 00:20:53,880 --> 00:21:00,180 properties that those particle shows and very useful again in making devices - 756 00:21:00,180 --> 00:21:00,190 very useful again in making devices - 757 00:21:00,190 --> 00:21:12,620 very useful again in making devices - now let's see 758 00:21:12,620 --> 00:21:12,630 759 00:21:12,630 --> 00:21:21,870 now let's look at here one thing that is 760 00:21:21,870 --> 00:21:21,880 now let's look at here one thing that is 761 00:21:21,880 --> 00:21:27,210 now let's look at here one thing that is the determine is this when the size of 762 00:21:27,210 --> 00:21:27,220 the determine is this when the size of 763 00:21:27,220 --> 00:21:34,380 the determine is this when the size of the semiconductor nanoparticles get 764 00:21:34,380 --> 00:21:34,390 the semiconductor nanoparticles get 765 00:21:34,390 --> 00:21:39,240 the semiconductor nanoparticles get smaller and smaller the energy band gap 766 00:21:39,240 --> 00:21:39,250 smaller and smaller the energy band gap 767 00:21:39,250 --> 00:21:47,340 smaller and smaller the energy band gap becomes gets higher and higher right now 768 00:21:47,340 --> 00:21:47,350 becomes gets higher and higher right now 769 00:21:47,350 --> 00:21:49,440 becomes gets higher and higher right now what does that means when the energy 770 00:21:49,440 --> 00:21:49,450 what does that means when the energy 771 00:21:49,450 --> 00:21:51,660 what does that means when the energy band gap gets higher and higher that 772 00:21:51,660 --> 00:21:51,670 band gap gets higher and higher that 773 00:21:51,670 --> 00:21:55,520 band gap gets higher and higher that means it will not absorb for example the 774 00:21:55,520 --> 00:21:55,530 means it will not absorb for example the 775 00:21:55,530 --> 00:21:58,740 means it will not absorb for example the visible light or the visible light 776 00:21:58,740 --> 00:21:58,750 visible light or the visible light 777 00:21:58,750 --> 00:22:01,740 visible light or the visible light energy visible light photons energy will 778 00:22:01,740 --> 00:22:01,750 energy visible light photons energy will 779 00:22:01,750 --> 00:22:03,960 energy visible light photons energy will not be enough to excite the electron 780 00:22:03,960 --> 00:22:03,970 not be enough to excite the electron 781 00:22:03,970 --> 00:22:05,760 not be enough to excite the electron from the valence band to the conduction 782 00:22:05,760 --> 00:22:05,770 from the valence band to the conduction 783 00:22:05,770 --> 00:22:09,570 from the valence band to the conduction band is again now this is the example 784 00:22:09,570 --> 00:22:09,580 band is again now this is the example 785 00:22:09,580 --> 00:22:19,580 band is again now this is the example here I guess this one is the phosphides 786 00:22:19,580 --> 00:22:19,590 here I guess this one is the phosphides 787 00:22:19,590 --> 00:22:23,520 here I guess this one is the phosphides some yes cadmium phosphide 3 cadmium and 788 00:22:23,520 --> 00:22:23,530 some yes cadmium phosphide 3 cadmium and 789 00:22:23,530 --> 00:22:26,660 some yes cadmium phosphide 3 cadmium and 2 phosphorus cadmium phosphide nano 790 00:22:26,660 --> 00:22:26,670 2 phosphorus cadmium phosphide nano 791 00:22:26,670 --> 00:22:29,280 2 phosphorus cadmium phosphide nano particles again nanoparticles now 792 00:22:29,280 --> 00:22:29,290 particles again nanoparticles now 793 00:22:29,290 --> 00:22:32,730 particles again nanoparticles now remember the size here is less than 10 794 00:22:32,730 --> 00:22:32,740 remember the size here is less than 10 795 00:22:32,740 --> 00:22:35,520 remember the size here is less than 10 nanometers the size here is about 10 796 00:22:35,520 --> 00:22:35,530 nanometers the size here is about 10 797 00:22:35,530 --> 00:22:37,410 nanometers the size here is about 10 nanometers these particles even though 798 00:22:37,410 --> 00:22:37,420 nanometers these particles even though 799 00:22:37,420 --> 00:22:39,840 nanometers these particles even though they're very large seems like large but 800 00:22:39,840 --> 00:22:39,850 they're very large seems like large but 801 00:22:39,850 --> 00:22:42,900 they're very large seems like large but they're very very small now this one is 802 00:22:42,900 --> 00:22:42,910 they're very very small now this one is 803 00:22:42,910 --> 00:22:47,250 they're very very small now this one is almost black this one is sort of 804 00:22:47,250 --> 00:22:47,260 almost black this one is sort of 805 00:22:47,260 --> 00:22:52,320 almost black this one is sort of brownish and then sort of orange or red 806 00:22:52,320 --> 00:22:52,330 brownish and then sort of orange or red 807 00:22:52,330 --> 00:22:54,870 brownish and then sort of orange or red whatever this is and then yellow and 808 00:22:54,870 --> 00:22:54,880 whatever this is and then yellow and 809 00:22:54,880 --> 00:22:56,370 whatever this is and then yellow and then this becomes a white at the 810 00:22:56,370 --> 00:22:56,380 then this becomes a white at the 811 00:22:56,380 --> 00:22:59,730 then this becomes a white at the particle gets smaller the explanations 812 00:22:59,730 --> 00:22:59,740 particle gets smaller the explanations 813 00:22:59,740 --> 00:23:03,030 particle gets smaller the explanations of these color again is follow when we 814 00:23:03,030 --> 00:23:03,040 of these color again is follow when we 815 00:23:03,040 --> 00:23:07,620 of these color again is follow when we have large sized nano particles remember 816 00:23:07,620 --> 00:23:07,630 have large sized nano particles remember 817 00:23:07,630 --> 00:23:10,740 have large sized nano particles remember again it has to be between 1 and hundred 818 00:23:10,740 --> 00:23:10,750 again it has to be between 1 and hundred 819 00:23:10,750 --> 00:23:13,800 again it has to be between 1 and hundred nanometers the band gap is very small 820 00:23:13,800 --> 00:23:13,810 nanometers the band gap is very small 821 00:23:13,810 --> 00:23:18,380 nanometers the band gap is very small and all of the visible light is absorbed 822 00:23:18,380 --> 00:23:18,390 and all of the visible light is absorbed 823 00:23:18,390 --> 00:23:20,490 and all of the visible light is absorbed when all of the visible light is 824 00:23:20,490 --> 00:23:20,500 when all of the visible light is 825 00:23:20,500 --> 00:23:23,070 when all of the visible light is absorbed the color of the substance will 826 00:23:23,070 --> 00:23:23,080 absorbed the color of the substance will 827 00:23:23,080 --> 00:23:24,989 absorbed the color of the substance will be what black 828 00:23:24,989 --> 00:23:24,999 be what black 829 00:23:24,999 --> 00:23:28,309 be what black colors right because it's all absorbed 830 00:23:28,309 --> 00:23:28,319 colors right because it's all absorbed 831 00:23:28,319 --> 00:23:32,779 colors right because it's all absorbed visible light now when you go this lower 832 00:23:32,779 --> 00:23:32,789 visible light now when you go this lower 833 00:23:32,789 --> 00:23:35,699 visible light now when you go this lower the size of the particles then the 834 00:23:35,699 --> 00:23:35,709 the size of the particles then the 835 00:23:35,709 --> 00:23:38,099 the size of the particles then the energy gets get a little bit higher and 836 00:23:38,099 --> 00:23:38,109 energy gets get a little bit higher and 837 00:23:38,109 --> 00:23:40,829 energy gets get a little bit higher and higher now in this range here it 838 00:23:40,829 --> 00:23:40,839 higher now in this range here it 839 00:23:40,839 --> 00:23:44,489 higher now in this range here it observes in the visible region and for 840 00:23:44,489 --> 00:23:44,499 observes in the visible region and for 841 00:23:44,499 --> 00:23:50,899 observes in the visible region and for example this one absorbs the blue light 842 00:23:50,899 --> 00:23:50,909 example this one absorbs the blue light 843 00:23:50,909 --> 00:23:52,919 example this one absorbs the blue light complementary light it would be probably 844 00:23:52,919 --> 00:23:52,929 complementary light it would be probably 845 00:23:52,929 --> 00:23:56,719 complementary light it would be probably blue here and then we go down here and 846 00:23:56,719 --> 00:23:56,729 blue here and then we go down here and 847 00:23:56,729 --> 00:24:00,989 blue here and then we go down here and the bandgap increases increases 848 00:24:00,989 --> 00:24:00,999 the bandgap increases increases 849 00:24:00,999 --> 00:24:04,529 the bandgap increases increases increases and when it gets to here this 850 00:24:04,529 --> 00:24:04,539 increases and when it gets to here this 851 00:24:04,539 --> 00:24:10,619 increases and when it gets to here this is colorless why it's colorless because 852 00:24:10,619 --> 00:24:10,629 is colorless why it's colorless because 853 00:24:10,629 --> 00:24:14,879 is colorless why it's colorless because in this case the bandgap is so big that 854 00:24:14,879 --> 00:24:14,889 in this case the bandgap is so big that 855 00:24:14,889 --> 00:24:17,669 in this case the bandgap is so big that there will be no absorption of the 856 00:24:17,669 --> 00:24:17,679 there will be no absorption of the 857 00:24:17,679 --> 00:24:23,579 there will be no absorption of the visible light now and we simply see all 858 00:24:23,579 --> 00:24:23,589 visible light now and we simply see all 859 00:24:23,589 --> 00:24:27,509 visible light now and we simply see all the colors which is white here total 860 00:24:27,509 --> 00:24:27,519 the colors which is white here total 861 00:24:27,519 --> 00:24:31,939 the colors which is white here total absorption very small energy band gap 862 00:24:31,939 --> 00:24:31,949 absorption very small energy band gap 863 00:24:31,949 --> 00:24:35,789 absorption very small energy band gap here no absorptions very large band gaps 864 00:24:35,789 --> 00:24:35,799 here no absorptions very large band gaps 865 00:24:35,799 --> 00:24:38,369 here no absorptions very large band gaps you see again how the size of the 866 00:24:38,369 --> 00:24:38,379 you see again how the size of the 867 00:24:38,379 --> 00:24:41,789 you see again how the size of the particles in nano scale changes the 868 00:24:41,789 --> 00:24:41,799 particles in nano scale changes the 869 00:24:41,799 --> 00:24:44,219 particles in nano scale changes the properties of the substance you see in 870 00:24:44,219 --> 00:24:44,229 properties of the substance you see in 871 00:24:44,229 --> 00:24:48,209 properties of the substance you see in color now this one is again another this 872 00:24:48,209 --> 00:24:48,219 color now this one is again another this 873 00:24:48,219 --> 00:24:51,179 color now this one is again another this is a cadmium selenide I guess another 874 00:24:51,179 --> 00:24:51,189 is a cadmium selenide I guess another 875 00:24:51,189 --> 00:24:54,629 is a cadmium selenide I guess another semiconductor but we have the solutions 876 00:24:54,629 --> 00:24:54,639 semiconductor but we have the solutions 877 00:24:54,639 --> 00:24:56,459 semiconductor but we have the solutions in this case cadmium selenide solutions 878 00:24:56,459 --> 00:24:56,469 in this case cadmium selenide solutions 879 00:24:56,469 --> 00:24:59,759 in this case cadmium selenide solutions and all have different particles and we 880 00:24:59,759 --> 00:24:59,769 and all have different particles and we 881 00:24:59,769 --> 00:25:03,619 and all have different particles and we simply eliminate this by UV radiation 882 00:25:03,619 --> 00:25:03,629 simply eliminate this by UV radiation 883 00:25:03,629 --> 00:25:07,309 simply eliminate this by UV radiation this is luminescence actually when you 884 00:25:07,309 --> 00:25:07,319 this is luminescence actually when you 885 00:25:07,319 --> 00:25:11,159 this is luminescence actually when you simply eliminate this by UV radiation UV 886 00:25:11,159 --> 00:25:11,169 simply eliminate this by UV radiation UV 887 00:25:11,169 --> 00:25:12,989 simply eliminate this by UV radiation UV radiation as much higher energy than the 888 00:25:12,989 --> 00:25:12,999 radiation as much higher energy than the 889 00:25:12,999 --> 00:25:16,289 radiation as much higher energy than the visible light the electron jumps into 890 00:25:16,289 --> 00:25:16,299 visible light the electron jumps into 891 00:25:16,299 --> 00:25:19,979 visible light the electron jumps into the conduction band from valence band to 892 00:25:19,979 --> 00:25:19,989 the conduction band from valence band to 893 00:25:19,989 --> 00:25:22,409 the conduction band from valence band to the conduction band but then they drop 894 00:25:22,409 --> 00:25:22,419 the conduction band but then they drop 895 00:25:22,419 --> 00:25:26,069 the conduction band but then they drop back from the conduction band to the 896 00:25:26,069 --> 00:25:26,079 back from the conduction band to the 897 00:25:26,079 --> 00:25:28,799 back from the conduction band to the valence band again as they drop down 898 00:25:28,799 --> 00:25:28,809 valence band again as they drop down 899 00:25:28,809 --> 00:25:31,169 valence band again as they drop down from conduction to the valence band they 900 00:25:31,169 --> 00:25:31,179 from conduction to the valence band they 901 00:25:31,179 --> 00:25:33,959 from conduction to the valence band they emit light in the visible region just 902 00:25:33,959 --> 00:25:33,969 emit light in the visible region just 903 00:25:33,969 --> 00:25:36,029 emit light in the visible region just like the emission spectrum of hydrogen's 904 00:25:36,029 --> 00:25:36,039 like the emission spectrum of hydrogen's 905 00:25:36,039 --> 00:25:38,909 like the emission spectrum of hydrogen's is again but different colors tells you 906 00:25:38,909 --> 00:25:38,919 is again but different colors tells you 907 00:25:38,919 --> 00:25:42,869 is again but different colors tells you what here different colors tells you 908 00:25:42,869 --> 00:25:42,879 what here different colors tells you 909 00:25:42,879 --> 00:25:47,070 what here different colors tells you that the band gap between the conduction 910 00:25:47,070 --> 00:25:47,080 that the band gap between the conduction 911 00:25:47,080 --> 00:25:48,599 that the band gap between the conduction band and the valence band because when 912 00:25:48,599 --> 00:25:48,609 band and the valence band because when 913 00:25:48,609 --> 00:25:50,369 band and the valence band because when the electron dropped from the conduction 914 00:25:50,369 --> 00:25:50,379 the electron dropped from the conduction 915 00:25:50,379 --> 00:25:52,529 the electron dropped from the conduction band to the valence band the photon 916 00:25:52,529 --> 00:25:52,539 band to the valence band the photon 917 00:25:52,539 --> 00:25:54,899 band to the valence band the photon release will have the energy equals to 918 00:25:54,899 --> 00:25:54,909 release will have the energy equals to 919 00:25:54,909 --> 00:25:56,759 release will have the energy equals to the band gap so when the band gap 920 00:25:56,759 --> 00:25:56,769 the band gap so when the band gap 921 00:25:56,769 --> 00:25:59,489 the band gap so when the band gap changes that means particle size changes 922 00:25:59,489 --> 00:25:59,499 changes that means particle size changes 923 00:25:59,499 --> 00:26:03,090 changes that means particle size changes the color emitted also changes let's 924 00:26:03,090 --> 00:26:03,100 the color emitted also changes let's 925 00:26:03,100 --> 00:26:06,269 the color emitted also changes let's again another example how the size of 926 00:26:06,269 --> 00:26:06,279 again another example how the size of 927 00:26:06,279 --> 00:26:11,509 again another example how the size of the particles changes the properties of 928 00:26:11,509 --> 00:26:11,519 the particles changes the properties of 929 00:26:11,519 --> 00:26:16,259 the particles changes the properties of nano material again now metals on the 930 00:26:16,259 --> 00:26:16,269 nano material again now metals on the 931 00:26:16,269 --> 00:26:19,710 nano material again now metals on the nano scale also have a lot of 932 00:26:19,710 --> 00:26:19,720 nano scale also have a lot of 933 00:26:19,720 --> 00:26:21,840 nano scale also have a lot of applications one of them is known for 934 00:26:21,840 --> 00:26:21,850 applications one of them is known for 935 00:26:21,850 --> 00:26:24,840 applications one of them is known for years and years you know even thousand 936 00:26:24,840 --> 00:26:24,850 years and years you know even thousand 937 00:26:24,850 --> 00:26:27,899 years and years you know even thousand years before and that is gold if you 938 00:26:27,899 --> 00:26:27,909 years before and that is gold if you 939 00:26:27,909 --> 00:26:31,109 years before and that is gold if you take gold and dissolve it in melted 940 00:26:31,109 --> 00:26:31,119 take gold and dissolve it in melted 941 00:26:31,119 --> 00:26:33,899 take gold and dissolve it in melted glass and you get all different colors 942 00:26:33,899 --> 00:26:33,909 glass and you get all different colors 943 00:26:33,909 --> 00:26:38,090 glass and you get all different colors why because in a glass gold 944 00:26:38,090 --> 00:26:38,100 why because in a glass gold 945 00:26:38,100 --> 00:26:41,070 why because in a glass gold nanoparticles form and depending on the 946 00:26:41,070 --> 00:26:41,080 nanoparticles form and depending on the 947 00:26:41,080 --> 00:26:42,960 nanoparticles form and depending on the size of those nanoparticles we have 948 00:26:42,960 --> 00:26:42,970 size of those nanoparticles we have 949 00:26:42,970 --> 00:26:45,269 size of those nanoparticles we have different colors these are simply 950 00:26:45,269 --> 00:26:45,279 different colors these are simply 951 00:26:45,279 --> 00:26:48,889 different colors these are simply stained things and this was explained by 952 00:26:48,889 --> 00:26:48,899 stained things and this was explained by 953 00:26:48,899 --> 00:26:52,710 stained things and this was explained by Michael Faraday in 1857 actually and he 954 00:26:52,710 --> 00:26:52,720 Michael Faraday in 1857 actually and he 955 00:26:52,720 --> 00:26:56,549 Michael Faraday in 1857 actually and he prepared some gold colloidal gold 956 00:26:56,549 --> 00:26:56,559 prepared some gold colloidal gold 957 00:26:56,559 --> 00:26:58,680 prepared some gold colloidal gold particle solutions all they have 958 00:26:58,680 --> 00:26:58,690 particle solutions all they have 959 00:26:58,690 --> 00:27:00,840 particle solutions all they have different colors even they're very very 960 00:27:00,840 --> 00:27:00,850 different colors even they're very very 961 00:27:00,850 --> 00:27:03,899 different colors even they're very very stable particularly gold nanoparticles 962 00:27:03,899 --> 00:27:03,909 stable particularly gold nanoparticles 963 00:27:03,909 --> 00:27:05,639 stable particularly gold nanoparticles these solutions are very very stable 964 00:27:05,639 --> 00:27:05,649 these solutions are very very stable 965 00:27:05,649 --> 00:27:08,700 these solutions are very very stable very stable they still they say they 966 00:27:08,700 --> 00:27:08,710 very stable they still they say they 967 00:27:08,710 --> 00:27:11,369 very stable they still they say they still in a museum in London there they 968 00:27:11,369 --> 00:27:11,379 still in a museum in London there they 969 00:27:11,379 --> 00:27:14,430 still in a museum in London there they keep those in different colors now this 970 00:27:14,430 --> 00:27:14,440 keep those in different colors now this 971 00:27:14,440 --> 00:27:16,799 keep those in different colors now this is again the glass you see stained glass 972 00:27:16,799 --> 00:27:16,809 is again the glass you see stained glass 973 00:27:16,809 --> 00:27:19,080 is again the glass you see stained glass and those colors are due to the 974 00:27:19,080 --> 00:27:19,090 and those colors are due to the 975 00:27:19,090 --> 00:27:21,149 and those colors are due to the nanoparticles that present in the glass 976 00:27:21,149 --> 00:27:21,159 nanoparticles that present in the glass 977 00:27:21,159 --> 00:27:28,019 nanoparticles that present in the glass metal nanoparticles now carbon on the 978 00:27:28,019 --> 00:27:28,029 metal nanoparticles now carbon on the 979 00:27:28,029 --> 00:27:31,830 metal nanoparticles now carbon on the nano scale is also important and great 980 00:27:31,830 --> 00:27:31,840 nano scale is also important and great 981 00:27:31,840 --> 00:27:34,799 nano scale is also important and great deal of research is done on this nano 982 00:27:34,799 --> 00:27:34,809 deal of research is done on this nano 983 00:27:34,809 --> 00:27:38,159 deal of research is done on this nano tubes of carbon nano scale carbon 984 00:27:38,159 --> 00:27:38,169 tubes of carbon nano scale carbon 985 00:27:38,169 --> 00:27:39,779 tubes of carbon nano scale carbon materials as a matter of fact now 986 00:27:39,779 --> 00:27:39,789 materials as a matter of fact now 987 00:27:39,789 --> 00:27:47,539 materials as a matter of fact now remember the carbon has three isotopes 988 00:27:47,539 --> 00:27:47,549 remember the carbon has three isotopes 989 00:27:47,549 --> 00:27:52,589 remember the carbon has three isotopes one is the graphite layer structure the 990 00:27:52,589 --> 00:27:52,599 one is the graphite layer structure the 991 00:27:52,599 --> 00:27:52,920 one is the graphite layer structure the other one 992 00:27:52,920 --> 00:27:52,930 other one 993 00:27:52,930 --> 00:27:56,670 other one Dimond the allotropes actually now 994 00:27:56,670 --> 00:27:56,680 Dimond the allotropes actually now 995 00:27:56,680 --> 00:28:00,720 Dimond the allotropes actually now another one is discovered in 1985 that 996 00:28:00,720 --> 00:28:00,730 another one is discovered in 1985 that 997 00:28:00,730 --> 00:28:03,420 another one is discovered in 1985 that makes about 30 years 31 years ago and 998 00:28:03,420 --> 00:28:03,430 makes about 30 years 31 years ago and 999 00:28:03,430 --> 00:28:08,880 makes about 30 years 31 years ago and that is fullerene carbon 60 for example 1000 00:28:08,880 --> 00:28:08,890 that is fullerene carbon 60 for example 1001 00:28:08,890 --> 00:28:10,830 that is fullerene carbon 60 for example which has very different structures than 1002 00:28:10,830 --> 00:28:10,840 which has very different structures than 1003 00:28:10,840 --> 00:28:15,440 which has very different structures than the others as a matter of fact now let's 1004 00:28:15,440 --> 00:28:15,450 the others as a matter of fact now let's 1005 00:28:15,450 --> 00:28:20,370 the others as a matter of fact now let's look at here this is again now then 1006 00:28:20,370 --> 00:28:20,380 look at here this is again now then 1007 00:28:20,380 --> 00:28:25,800 look at here this is again now then another allotrope I can probably say off 1008 00:28:25,800 --> 00:28:25,810 another allotrope I can probably say off 1009 00:28:25,810 --> 00:28:30,440 another allotrope I can probably say off carbon which is one layer of the 1010 00:28:30,440 --> 00:28:30,450 carbon which is one layer of the 1011 00:28:30,450 --> 00:28:33,240 carbon which is one layer of the graphite actually if you take one layer 1012 00:28:33,240 --> 00:28:33,250 graphite actually if you take one layer 1013 00:28:33,250 --> 00:28:35,820 graphite actually if you take one layer of graphite like this all carbons are 1014 00:28:35,820 --> 00:28:35,830 of graphite like this all carbons are 1015 00:28:35,830 --> 00:28:38,370 of graphite like this all carbons are bonded to three other carbons and sp2 1016 00:28:38,370 --> 00:28:38,380 bonded to three other carbons and sp2 1017 00:28:38,380 --> 00:28:40,470 bonded to three other carbons and sp2 hybridization here and that is called 1018 00:28:40,470 --> 00:28:40,480 hybridization here and that is called 1019 00:28:40,480 --> 00:28:45,140 hybridization here and that is called graphene and this was also discovered in 1020 00:28:45,140 --> 00:28:45,150 graphene and this was also discovered in 1021 00:28:45,150 --> 00:28:48,090 graphene and this was also discovered in 1990s I guess and the Nobel Prize is 1022 00:28:48,090 --> 00:28:48,100 1990s I guess and the Nobel Prize is 1023 00:28:48,100 --> 00:28:50,190 1990s I guess and the Nobel Prize is given to the people who discover that 1024 00:28:50,190 --> 00:28:50,200 given to the people who discover that 1025 00:28:50,200 --> 00:28:55,230 given to the people who discover that physicist in 2010 I I guess the graphene 1026 00:28:55,230 --> 00:28:55,240 physicist in 2010 I I guess the graphene 1027 00:28:55,240 --> 00:28:57,000 physicist in 2010 I I guess the graphene and they have very very different 1028 00:28:57,000 --> 00:28:57,010 and they have very very different 1029 00:28:57,010 --> 00:28:58,980 and they have very very different properties very interested in different 1030 00:28:58,980 --> 00:28:58,990 properties very interested in different 1031 00:28:58,990 --> 00:29:02,180 properties very interested in different properties this is the fullerene 1032 00:29:02,180 --> 00:29:02,190 properties this is the fullerene 1033 00:29:02,190 --> 00:29:06,270 properties this is the fullerene structure this is carbon 60 I have 60 1034 00:29:06,270 --> 00:29:06,280 structure this is carbon 60 I have 60 1035 00:29:06,280 --> 00:29:09,540 structure this is carbon 60 I have 60 carbon atoms and you see again we have 1036 00:29:09,540 --> 00:29:09,550 carbon atoms and you see again we have 1037 00:29:09,550 --> 00:29:12,360 carbon atoms and you see again we have the Pentagon's regular Pentagon's and 1038 00:29:12,360 --> 00:29:12,370 the Pentagon's regular Pentagon's and 1039 00:29:12,370 --> 00:29:15,920 the Pentagon's regular Pentagon's and regular hexagons as phases this is 1040 00:29:15,920 --> 00:29:15,930 regular hexagons as phases this is 1041 00:29:15,930 --> 00:29:21,090 regular hexagons as phases this is simply I guess it has 20 hexagons and 12 1042 00:29:21,090 --> 00:29:21,100 simply I guess it has 20 hexagons and 12 1043 00:29:21,100 --> 00:29:24,960 simply I guess it has 20 hexagons and 12 Pentagon's as a face 32 faces and the 1044 00:29:24,960 --> 00:29:24,970 Pentagon's as a face 32 faces and the 1045 00:29:24,970 --> 00:29:29,120 Pentagon's as a face 32 faces and the football the ball that is play football 1046 00:29:29,120 --> 00:29:29,130 football the ball that is play football 1047 00:29:29,130 --> 00:29:33,080 football the ball that is play football also has the same structure there 1048 00:29:33,080 --> 00:29:33,090 also has the same structure there 1049 00:29:33,090 --> 00:29:38,220 also has the same structure there Pentagon's and hexagons as simply on the 1050 00:29:38,220 --> 00:29:38,230 Pentagon's and hexagons as simply on the 1051 00:29:38,230 --> 00:29:40,320 Pentagon's and hexagons as simply on the surface like this so it's called 1052 00:29:40,320 --> 00:29:40,330 surface like this so it's called 1053 00:29:40,330 --> 00:29:42,000 surface like this so it's called fullerene why it's called fullerene 1054 00:29:42,000 --> 00:29:42,010 fullerene why it's called fullerene 1055 00:29:42,010 --> 00:29:46,830 fullerene why it's called fullerene because an american engineer and 1056 00:29:46,830 --> 00:29:46,840 because an american engineer and 1057 00:29:46,840 --> 00:29:48,890 because an american engineer and architect sometimes they say philosopher 1058 00:29:48,890 --> 00:29:48,900 architect sometimes they say philosopher 1059 00:29:48,900 --> 00:29:54,230 architect sometimes they say philosopher he find out how to make Joe dezik domes 1060 00:29:54,230 --> 00:29:54,240 he find out how to make Joe dezik domes 1061 00:29:54,240 --> 00:29:59,880 he find out how to make Joe dezik domes Kubek Big Joe dezik domes and he used 1062 00:29:59,880 --> 00:29:59,890 Kubek Big Joe dezik domes and he used 1063 00:29:59,890 --> 00:30:01,890 Kubek Big Joe dezik domes and he used very similar structure there half of 1064 00:30:01,890 --> 00:30:01,900 very similar structure there half of 1065 00:30:01,900 --> 00:30:04,100 very similar structure there half of that dome will be the half of that and 1066 00:30:04,100 --> 00:30:04,110 that dome will be the half of that and 1067 00:30:04,110 --> 00:30:06,480 that dome will be the half of that and when this was discovered 1068 00:30:06,480 --> 00:30:06,490 when this was discovered 1069 00:30:06,490 --> 00:30:11,320 when this was discovered 18 1985 actually the name given these 1070 00:30:11,320 --> 00:30:11,330 18 1985 actually the name given these 1071 00:30:11,330 --> 00:30:13,930 18 1985 actually the name given these type of compounds of carbon are called 1072 00:30:13,930 --> 00:30:13,940 type of compounds of carbon are called 1073 00:30:13,940 --> 00:30:15,789 type of compounds of carbon are called fullerenes actually fullerenes 1074 00:30:15,789 --> 00:30:15,799 fullerenes actually fullerenes 1075 00:30:15,799 --> 00:30:19,210 fullerenes actually fullerenes and you can simply take the fullerenes 1076 00:30:19,210 --> 00:30:19,220 and you can simply take the fullerenes 1077 00:30:19,220 --> 00:30:22,659 and you can simply take the fullerenes and dissolve it in organic solvent you 1078 00:30:22,659 --> 00:30:22,669 and dissolve it in organic solvent you 1079 00:30:22,669 --> 00:30:23,289 and dissolve it in organic solvent you see again 1080 00:30:23,289 --> 00:30:23,299 see again 1081 00:30:23,299 --> 00:30:26,200 see again you can't dissolve graphite in organic 1082 00:30:26,200 --> 00:30:26,210 you can't dissolve graphite in organic 1083 00:30:26,210 --> 00:30:28,000 you can't dissolve graphite in organic solvent you can desire dissolved 1084 00:30:28,000 --> 00:30:28,010 solvent you can desire dissolved 1085 00:30:28,010 --> 00:30:29,980 solvent you can desire dissolved diamonds in organic solvent but you can 1086 00:30:29,980 --> 00:30:29,990 diamonds in organic solvent but you can 1087 00:30:29,990 --> 00:30:32,830 diamonds in organic solvent but you can dissolve fullerenes in organic solvents 1088 00:30:32,830 --> 00:30:32,840 dissolve fullerenes in organic solvents 1089 00:30:32,840 --> 00:30:34,659 dissolve fullerenes in organic solvents actually and then you can carry out 1090 00:30:34,659 --> 00:30:34,669 actually and then you can carry out 1091 00:30:34,669 --> 00:30:37,000 actually and then you can carry out reactions with this reaction with this 1092 00:30:37,000 --> 00:30:37,010 reactions with this reaction with this 1093 00:30:37,010 --> 00:30:41,100 reactions with this reaction with this now so we have these carbon-carbon 1094 00:30:41,100 --> 00:30:41,110 now so we have these carbon-carbon 1095 00:30:41,110 --> 00:30:45,039 now so we have these carbon-carbon minute Nano tips this is like you take 1096 00:30:45,039 --> 00:30:45,049 minute Nano tips this is like you take 1097 00:30:45,049 --> 00:30:48,130 minute Nano tips this is like you take those one layer which is called graphene 1098 00:30:48,130 --> 00:30:48,140 those one layer which is called graphene 1099 00:30:48,140 --> 00:30:51,340 those one layer which is called graphene of the graphite and then roll it up like 1100 00:30:51,340 --> 00:30:51,350 of the graphite and then roll it up like 1101 00:30:51,350 --> 00:30:55,870 of the graphite and then roll it up like this and then on to end you can cap it 1102 00:30:55,870 --> 00:30:55,880 this and then on to end you can cap it 1103 00:30:55,880 --> 00:30:59,860 this and then on to end you can cap it with half of the fullerene c60 you know 1104 00:30:59,860 --> 00:30:59,870 with half of the fullerene c60 you know 1105 00:30:59,870 --> 00:31:02,470 with half of the fullerene c60 you know you take the half of that and then cap 1106 00:31:02,470 --> 00:31:02,480 you take the half of that and then cap 1107 00:31:02,480 --> 00:31:06,370 you take the half of that and then cap it to here and here and then you have 1108 00:31:06,370 --> 00:31:06,380 it to here and here and then you have 1109 00:31:06,380 --> 00:31:09,340 it to here and here and then you have these nanotubes and these nanotubes are 1110 00:31:09,340 --> 00:31:09,350 these nanotubes and these nanotubes are 1111 00:31:09,350 --> 00:31:14,140 these nanotubes and these nanotubes are so strong and they have so unusual 1112 00:31:14,140 --> 00:31:14,150 so strong and they have so unusual 1113 00:31:14,150 --> 00:31:17,230 so strong and they have so unusual properties actually and they have lot of 1114 00:31:17,230 --> 00:31:17,240 properties actually and they have lot of 1115 00:31:17,240 --> 00:31:20,230 properties actually and they have lot of applications and that increases every 1116 00:31:20,230 --> 00:31:20,240 applications and that increases every 1117 00:31:20,240 --> 00:31:23,590 applications and that increases every day and a great amount of research as I 1118 00:31:23,590 --> 00:31:23,600 day and a great amount of research as I 1119 00:31:23,600 --> 00:31:28,380 day and a great amount of research as I said is devoted to develop these nano 1120 00:31:28,380 --> 00:31:28,390 said is devoted to develop these nano 1121 00:31:28,390 --> 00:31:32,110 said is devoted to develop these nano tube carbon nanotubes and other nano 1122 00:31:32,110 --> 00:31:32,120 tube carbon nanotubes and other nano 1123 00:31:32,120 --> 00:31:37,620 tube carbon nanotubes and other nano scale carbons now for example this is an 1124 00:31:37,620 --> 00:31:37,630 scale carbons now for example this is an 1125 00:31:37,630 --> 00:31:42,340 scale carbons now for example this is an imaginary picture which imagines that 1126 00:31:42,340 --> 00:31:42,350 imaginary picture which imagines that 1127 00:31:42,350 --> 00:31:45,580 imaginary picture which imagines that the carbon nanotube this is the carbon 1128 00:31:45,580 --> 00:31:45,590 the carbon nanotube this is the carbon 1129 00:31:45,590 --> 00:31:51,340 the carbon nanotube this is the carbon nanotube can be used as a carrier belt 1130 00:31:51,340 --> 00:31:51,350 nanotube can be used as a carrier belt 1131 00:31:51,350 --> 00:31:54,279 nanotube can be used as a carrier belt you know the carrier belt to carry one 1132 00:31:54,279 --> 00:31:54,289 you know the carrier belt to carry one 1133 00:31:54,289 --> 00:31:57,039 you know the carrier belt to carry one molecule like this you know that would 1134 00:31:57,039 --> 00:31:57,049 molecule like this you know that would 1135 00:31:57,049 --> 00:31:59,320 molecule like this you know that would be like devices in the nano scale 1136 00:31:59,320 --> 00:31:59,330 be like devices in the nano scale 1137 00:31:59,330 --> 00:32:02,529 be like devices in the nano scale actually as I said the main purpose is 1138 00:32:02,529 --> 00:32:02,539 actually as I said the main purpose is 1139 00:32:02,539 --> 00:32:06,370 actually as I said the main purpose is to use the nano scale knowledge and make 1140 00:32:06,370 --> 00:32:06,380 to use the nano scale knowledge and make 1141 00:32:06,380 --> 00:32:09,970 to use the nano scale knowledge and make devices which is in nano scale size very 1142 00:32:09,970 --> 00:32:09,980 devices which is in nano scale size very 1143 00:32:09,980 --> 00:32:12,970 devices which is in nano scale size very very small sizes you know the molecular 1144 00:32:12,970 --> 00:32:12,980 very small sizes you know the molecular 1145 00:32:12,980 --> 00:32:16,990 very small sizes you know the molecular size is it okay I guess 1146 00:32:16,990 --> 00:32:17,000 size is it okay I guess 1147 00:32:17,000 --> 00:32:21,789 size is it okay I guess this is all do I have sometimes yes but 1148 00:32:21,789 --> 00:32:21,799 this is all do I have sometimes yes but 1149 00:32:21,799 --> 00:32:25,450 this is all do I have sometimes yes but I will stop it here and that is the end 1150 00:32:25,450 --> 00:32:25,460 I will stop it here and that is the end 1151 00:32:25,460 --> 00:32:30,370 I will stop it here and that is the end of this chapter now please read it from 1152 00:32:30,370 --> 00:32:30,380 of this chapter now please read it from 1153 00:32:30,380 --> 00:32:33,370 of this chapter now please read it from the book and try to solve the problems 1154 00:32:33,370 --> 00:32:33,380 the book and try to solve the problems 1155 00:32:33,380 --> 00:32:36,760 the book and try to solve the problems at the end of each chapter please do it 1156 00:32:36,760 --> 00:32:36,770 at the end of each chapter please do it 1157 00:32:36,770 --> 00:32:41,680 at the end of each chapter please do it because those are the type of problems 1158 00:32:41,680 --> 00:32:41,690 because those are the type of problems 1159 00:32:41,690 --> 00:32:45,130 because those are the type of problems we usually ask in the exam