Chapter 121: Unique fibrous structure

　　 The next morning, Xu Qiu and Chen Wanqing went to the old chemical building with samples.
　　 Entering the room, you can see an instrument placed in the center, presumably a transmission electron microscope TEM.
　　 From the appearance point of view, there is not much difference between this TEM and Caiyi's scanning electron microscope. Both are a large pile of metal, plus an operating computer.
　　 In principle, TEM is similar to optical microscope, except that one uses electron imaging and the other uses light imaging.
　　 Precision instruments like TEM, which cost in seven or eight figures, are tested by a dedicated teacher.
　　 Seeing the two, the tester said:
　　 "It was reserved online, right, what sample?"
　　 "The polymer film is ready on the copper grid."
　　 After speaking, Chen Wanqing took out the No. 1 sample.
　　 The tester picked up the sample copper mesh with tweezers and glanced at it, and said:
　　 "For this kind of sample, it can be tested directly."
　　He put the copper mesh in a rod-shaped sample holder, and then put the sample holder into the TEM instrument.
　　Operation console, add liquid nitrogen to cool and vacuum.
　　 After a few minutes, the vacuum reached the standard and the test started.
　　 The image is displayed on the screen in real time, and the initial magnification is not large.
　　 The tester operates the joystick, moves the lens, and moves the field of view to the copper net, and the grid shape can be observed.
　　 Move the lens again to find the effective film on the copper net.
　　 Finally, he picked a flat area.
　　 "Shoot here?"
"it is good."
　　 Get the instruction, and the tester starts to zoom in on the image.
　　 Xu Qiu saw that the scale on the screen went from 1 micron to 500 nanometers, then to 200 nanometers, and finally reduced to 5 nanometers.
　　 Each time the tester zooms in on the image, one or two photos are taken.
After 　　 took a group of photos, he reduced the image back to its original state and replaced it with another flat film.
　　 repeated it again and got another set of photos.
　　 "Change samples?"
"it is good."
　　 This sample No. 1 is the system of senior sister.
The TEM image taken by 　　 is similar to the snowflake pattern when the black and white TV had no signal.
　　 In fact, in organic photovoltaics, most of the TEM images of the effective layer are like this, mainly because of the weak crystallinity of the polymer donor material.
　　 It mixes well with the acceptor material PCBM in the blend film, and there is no large crystalline area.
　　 It's not surprising to get such a result.
　　 1 to 3 are all samples of the senior sister, and the images obtained are all the same.
　　 Xu Qiu is looking forward to TEM images based on his system. Will it be different?
　　 Chen Wanqing originally planned to take sample No. 4, but he stopped it, replaced it with sample No. 7, and planned to test this first.
　　 The No. 7 sample is P2FBT4T-2OD:PC[70]BM, which is the effective layer film based on the current optimal system with an efficiency of 10%.
　　 Load samples, add liquid nitrogen to cool, vacuum, and wait.
　　 The tester starts the test.
　　 also took two sets of images.
The TEM pattern obtained by 　　 is completely different from the sample pattern of Senpai.
The 　　 pattern is very beautiful, no longer in the shape of snowflakes.
　　 Instead, there are fibrous patterns, one by one, with a length of tens of nanometers, and a width of a few nanometers to a dozen nanometers.
　　 High probability is the aggregation phase formed by P2FBT4T-2OD molecules with high crystallinity, which can be attributed to the high crystallinity of the polymer donor.
　　 This is consistent with the previous differential scanning calorimetry DSC results.
　　If the results of the light source GIWAXS can also show that it has high crystallinity, the consistency of the data is very good.
After 　　, the remaining four sets of samples were tested, and they all showed a fibrous structure similar to the No. 7 sample.
　　 The test went very well, and the eight spare samples prepared before did not come in handy.
　　……
　　Leave the TEM test room.
　　 "Sister, I have a question." Xu Qiu said:
　　 "First of all, I am not targeting you, but talking about a common phenomenon."
　　 "Talk about it."
　　 Chen Wanqing was also a little curious when he heard this abruptly.
　　 "The TEM image taken by the sample of the senior sister is not much different from other people's literature," Xu Qiu said:
　　 "Put them together, it is impossible to tell which picture corresponds to which system. In that case, why do people still take TEM and put its image in the text."
　　 "So you want to say this, maybe early TEM can see some information, this testing tradition will continue." Chen Wanqing said:
　　 "You have to thank this testing tradition, otherwise you will not come to the test, you will not be able to get the beautiful TEM pattern just taken."
　　 "It's also."
　　 was about to leave the old chemical building, Chen Wanqing stopped and said:
　　 "Let me see if the NMR tester has opened the door. It happens to be in this building. I came to make an appointment before. They said that the equipment is faulty and needs repair. It is estimated that it has been repaired now."
　　 The nuclear magnetic resonance NMR test room is on the other side of the corridor. Looking at it from a distance, the door is open, there are lights, and it seems to be open.
　　 The two walked to the door, Chen Wanqing entered the room, and Xu Qiu waited outside.
　　 Not long after, she came out and said happily:
　　 "It's ready for testing. The nuclear magnetic test is to send samples. We only need to prepare the samples and send them."
　　 "NMR, I remember to prepare samples specially." Xu Qiu said.
　　"Yes, a special nuclear magnetic tube is used, and the solvent is deuterated chloroform~EbookFREE.me~ Chen Wanqing said:
　　 "The essentials of nuclear magnet tubes, deuterated chloroform is left in our laboratory."
　　 On the way to the receiving office, Chen Wanqing continued to introduce:
　　"We want to measure the NMR spectrum and the carbon spectrum. It is enough to prepare one sample for one material.
　　 Among them, the signal of the hydrogen spectrum is generally clear, but if you want to measure the carbon spectrum, you need a higher concentration of the solution, otherwise there may only be the signal of the solvent.
For 　　 small molecule materials, the solubility is high, and high concentration solutions can be prepared, and the carbon spectrum is easier to measure.
　　The solubility of our polymer material in deuterated chloroform is estimated to be only 5 mg/ml, and the carbon spectrum is highly probable.
　　 However, this is not a problem. If it can’t be measured, only the hydrogen spectrum data is good. "
　　……
　　 After using up, return to the laboratory.
　　 Xu Qiu picked up an NMR tube and found that it was an ordinary, slender transparent glass tube with a diameter of 3-4 mm and a length of about 20 cm, with a plastic stopper on it.
　　 Deuterated chloroform is packed in a glass bottle, which is similar to a glass bottle containing medical glucose, and its scientific name is called an ampoule.
　　 Because it is difficult to open, it is rarely seen now.
　　 I didn't expect to see this kind of bottle in the laboratory again.
　　Theoretically, before opening, cut a scratch on the bottleneck with a grinding wheel, and then break it apart.
　　 Of course, it’s not impossible to break it directly, it’s easy to hurt yourself.
　　 Deuterated chloroform is a hydrogen atom in chloroform, which is replaced by its isotope deuterium.
　　Because deuterium is not radioactive, the toxicity of this thing is no different from that of chloroform.
　　 However, the volume of a bottle of deuterated chloroform is only one milliliter, which is not a big problem.