I Have a Research Support System

The next morning, Xu Qiu and Chen Wanqing went to the old chemical building with samples.

Entering the room, you can see an instrument in the center, which must be the transmission electron microscope TEM.

From the appearance point of view, this TEM is not much different from Cai Yi's scanning electron microscope, it is a big lump 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.

A precision instrument like TEM with a price of seven or eight figures is tested by a dedicated teacher.

Seeing the two, the tester said:

"I made an appointment online, right? What sample?"

"Polymer film, already prepared on copper grid."

After finishing speaking, Chen Wanqing took out sample No. 1.

The tester took a look at the sample copper mesh with tweezers and said:

"This kind of sample can be tested directly."

He mounted the copper grid in a stick-shaped sample holder, which he then placed in the TEM instrument.

Operate the console, add liquid nitrogen to cool it, and evacuate it.

After a few minutes, the vacuum reaches the standard and the test begins.

The image is displayed on the screen in real time, and the initial magnification is not large.

The tester operates the joystick, moves the camera, and moves the field of view to the copper grid, and the grid can be observed.

Move the camera again to find the effective layer film on the copper grid.

Finally, he picked a flat place.

"Shoot here?"

"good."

On command, the tester began to zoom in on the image.

Xu Qiu saw the scale on the screen from 1 micron to 500 nanometers, then to 200 nanometers, and finally reduced to 5 nanometers.

Each time the tester zoomed in on the image, he took a photo or two.

After taking a set of photos, he reduced the image back to its original state and replaced it with another flat film.

Repeat it again and get another set of photos.

"Change samples?"

"good."

This No. 1 sample is the senior sister's system.

The TEM image taken is similar to the snowflake pattern when the black and white TV had no signal.

In fact, in organic photovoltaics, the TEM images of most active layers are like this, mainly because of the weak crystallinity of the polymer donor material.

It is well mixed with the acceptor material PCBM in the blend film without large crystalline domains.

It is not surprising to get such a result.

Numbers 1 to 3 are samples of the senior sister, and the images obtained are all similar.

Xu Qiu is looking forward to the TEM images based on his system, will it be different?

Chen Wanqing originally planned to take sample No. 4, but he stopped him and changed to sample No. 7, intending to test this first.

Sample No. 7 is P2FBT4T-2OD:PC[70]BM, which is the effective layer film based on the current optimal system, and the efficiency can be increased by 10%.

Load the sample, add liquid nitrogen to cool, evacuate, and wait.

The tester starts the test.

Two sets of images were also taken.

The obtained TEM pattern is completely different from the sample pattern of the senior sister.

The pattern is very beautiful, it is no longer snowflake-like.

Instead, fibrous patterns appeared, one by one, with a length of tens of nanometers and a width of several to ten nanometers.

The high probability is the aggregated 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 results of differential scanning calorimetry (DSC).

If the results of the light source GIWAXS can also show that it has high crystallinity, the consistency of the data is very good.

Afterwards, the remaining four groups of samples were tested, all exhibiting a fibrous structure similar to that of sample No. 7.

The test went very well, and the eight spare samples prepared earlier were not used.

...

Leave the TEM testing room.

"Sister, I have a question." Xu Qiu said:

"First of all, I am not targeting you, but talking about a common phenomenon."

"Tell me about it."

Hearing such a sentence from him suddenly, Chen Wanqing was also a little curious.

"The TEM images taken by my sister's sample are not much different from those in other people's literature," Xu Qiu said:

"Put them together and you can't tell which picture corresponds to which system. In this case, why do people still take TEM and put its image in the text."

"So you wanted to say this, maybe the early TEM can see some information, and this testing tradition has continued." Chen Wanqing said:

"You have to be grateful for this testing tradition, otherwise you wouldn't come to test, and you wouldn't be able to get the beautiful TEM pattern you just took."

"That's right."

Just as she was about to leave the old chemical building, Chen Wanqing stopped and said:

"I'll see if the NMR tester is open. I happen to be in this building. I made an appointment before. They said that the equipment was faulty and needed repairs. It has probably been repaired now."

The nuclear magnetic resonance NMR test room is at the other end of the corridor. From a distance, the door is open and there are lights. It seems that it is 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 to test. The NMR test is to send samples. We can prepare the samples and send them over."

"NMR, I remember that we have to prepare samples specially," Xu Qiu said.

"That's right, a dedicated NMR tube is used, and deuterated chloroform is used as the solvent." Chen Wanqing said:

"NMR tubes are used for essentials, and we have surplus deuterated chloroform in our laboratory."

On the way to the receiving place, Chen Wanqing continued to introduce:

"We want to measure the H NMR and C NMR spectra, and it is enough to prepare one sample for one material.

Among them, the signal of the hydrogen spectrum is generally relatively clear, but to measure the carbon spectrum, the concentration of the solution needs to be relatively high, otherwise there may be only the signal of the solvent.

For small molecule materials, the solubility is high, and a high concentration solution 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 per milliliter, and the carbon spectrum is likely to be unacceptable.

However, this is not a problem. If you can't measure it, just release the hydrogen spectrum data. "

...

When finished, 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 packaged in a glass bottle, which is similar to the glass bottle containing medical glucose, and its scientific name is an ampoule.

Because it is more difficult to open, it is rarely seen now.

I didn't expect to see this kind of small bottle again in the laboratory.

In theory, before opening, the bottle neck should be scratched with a grinding wheel, and then it should be broken apart.

Of course, it's not impossible to break it directly, but it's easy to hurt yourself.

Deuterochloroform is a hydrogen atom in chloroform replaced by its isotope deuterium.

Because deuterium is not radioactive, this stuff is no different from chloroform in toxicity.

However, the volume of a bottle of deuterated chloroform is only one milliliter, so it is not a big problem.