What is an Example of Crystal Structure?

What is an Example of Crystal Structure?

Investigation of PyBTM doped into αH-PyBTM crystals with NMR, Raman, ESR, and X-ray.

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Physics Nobel Prize Winner MIT Prof Frank Wilczek on String Theory, Gravitation, Newton & Big Bang : What is an Example of Crystal Structure?

Kimura et al.¹ investigated the (3,5-dichloro-4-pyridyl)-bis(2,4,6-trichlorophenyl)methyl radical (PyBTM), doped into αH-PyBTM crystals by magneto-luminescence and fluorescence instrument. However, there are four more instruments which are Raman, NMR, ESR, and X-ray, which NMR5 ESR, and X-ray, which can be used to test the αH-PyBTM and doped αH-PyBTM. Raman Spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules. However, when there are more doping, the bond strength becomes weak, and the Raman spectroscopy Nuclear magnetic resonance (NMR) spectroscopy, is a spectroscopic i N ^’ technique to test magnetic fields around atomic nuclei. In the crystal, there are some nuclei in it.

Electron spin resonance (ESR) spectroscopy is a method for studying materials with unpaired electrons, and is similar to NMR spectroscopy. Because of that, there must be some strong peaks in the ESR spectrum. Finally, X-ray spectroscopy is also a good instrumentation to determine doping crystals because X-ray spectroscopy could clearly show the changes when a crystal is doped. But there may be no result in the crystal because of it9s very similar. Those four different experiments may have different results, and it may show some new status in the αH-PyBTM. Metal complexes with coordinated PyBTM molecules are also expected to show interesting luminescence properties and are currently under investigation.⁶

Introduction : What is an Example of Crystal Structure? Investigation of PyBTM doped into αH-PyBTM crystals with NMR, Raman, ESR, and X-ray.

Nuclear magnetic resonance (NMR) spectroscopy, is a spectroscopic technique to test magnetic fields around atomic nuclei. The sample is placed into a strong magnetic field, and the signal is detected by excitation of nuclei sample with radio waves. NMR spectroscopy gives detailed information about the structure, dynamics, reaction state, and chemical status of molecules. The most common types of NMR are proton and ¹³C NMR spectroscopy, but in Majzoub et al. experiment, TiCl₃ was doped into NaAlH₄ crystal. They studied by ²⁷Al MAS NMR because NMR spectroscopy could test any kind of sample which has different nuclei spin. They think that when there is different % of doping, the signal of NMR spectroscopy is different. So they showed several spectra, figures and a table to explain their hypothesis.

Table 1. Measured solvent, % of doping, form and milled sample in crystal doping.

Sample	Solvent	at. %	Form	Milled
S2	THF	4	Crushed crystal	No
S3a	THF	4	Fine powder	No
S4	THF	33	Fine powder	No
S5	None	33	Fine powder	Yes

Figure 1. This spectrum shows different solvent by different % of doping. 

Table 1 describes important sample properties. Figure 1(a) shows sample S2. Figure 1(b) shows sample S3a. Figure 1(c) shows sample S4, and Figure 1(a) shows sample S5. The spectra for sample S2 is found by a peak at 94.6 ppm which is NaAlH₄.² The spectrum of sample S3a is identified by three distinct ²⁷Al NMR resonances: one at 1640ppm, assigned to metallic aluminum; one at approximately −42.6ppm, assigned to Na₃AlH₆ ; and one at 94.2 ppm, assigned to NaAlH₄.²

Those peaks are made base on pure materials. Sample S4 has two distinct peaks: metallic aluminum at 1641 ppm and a series of overlapping resonances at 8.4, 35.5, and 63.6 ppm, assigned to six, five, and four coordinate aluminum–oxygen species, respectively, in Al₂O₃.² In that case, when both THF and TiCl₃ are present, Al₂O₃ is formed because ²⁷Al NMR observed no significant narrowing of the Al₂O₃ resonances with decoupling, which observe in the NaAlH₄ peak for sample S2. When there is more and more doping, Al₂O₃ is formed, and NaAlH₄ and Na₃AlH₆ disappear. Because of that, the shape and size of peaks for NaAlH₄ is decreased. 

Raman Spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules. The sample is excited with a laser beam. Electromagnetic radiation from the illuminated point is collected with a lens and sent through a monochromator. In Prawer et al.’s research,³ they studied diamond and boron doped into diamond by Raman spectroscopy. There are some differences between the {100} diamond crystal surfaces and the {111} diamond crystal surfaces which are shown in Figure 2. There are some different Raman shifts and peaks when increasing the doping.

Figure 2. This spectrum shows boron doped into diamond between the {100} diamond crystal surfaces and the {111} diamond crystal surfaces.

In Figure 2, there are some peaks that appear at 500 cm⁻¹ and 1230 cm⁻¹,and between those two peaks, there are some huge differences as doping changes. First of all, when there is more doping, peaks become broader after B/C ratios are greater than 200 ppm. But because of different facets of crystals, broad peaks are present by different types because the monochromator detects different signals, even if it’s the same crystal structure. From the doped crystal, the results clearly showed bond strength of C-C which is 1230 cm^-1 is weaker, and bond strength of B-C  which is 500 cm^-1 is stronger. 

Electron spin resonance (ESR) spectroscopy is a method for studying materials with unpaired electrons, and it’s similar to NMR spectroscopy. ESR tests unpaired electrons, and NMR tests nuclei. In the ESR spectroscopy, an unpaired electron can move between the two energy levels by either absorbing or emitting energy. Trihi et al.⁴ described that squalene was doped into polymethylmethacrylate (PMMA), in addition, the spectra are shown in Figure 3 and 4. Those samples were radiated with gamma irradiation to create radicals.

Figure 3. This spectrum showed the ESR spectrums evolution of undoped PMMA with time.

Figure 4. This spectrum showed the ESR spectrum’s evolution of doped PMMA with time.

In Figure 3, there were no doped PMMA, and in Figure 4, there were some doped PMMA. A difference in behavior was noticed between the doped and undoped PMMA. Even though the free radical decay is faster during the first 10 days, the number of free radicals detected after 22 days remains higher in the doped PMMA. However, there is no significant difference between undoped PMMA and doped PMMA spectra.

Finally, X-ray spectroscopy is also a good instrumentation to determine doping crystals because X-ray spectroscopy could clearly show the changes when a crystal is doped. Tashiro et al.⁵ described the X-ray fiber diagrams of the uniaxially oriented P3HT samples taken before and after doping with iodine. After P3HT was doped by iodine, there are some changes in the doped spectra. 

Figure 5. This spectrum showed X-ray fiber diagrams of iodine-doped P3HT samples.

In the figure 5, some characteristic features may be picked out. The orientation of the polythiophene chain is preserved even after doping, and there are position and relative intensity of the equatorial reflections are remarkably different from those of the pristine samples.⁵

Hypothesis

(3,5-dichloro-4-pyridyl)-bis(2,4,6-trichlorophenyl)methyl radical (PyBTM) is a new kind of crystal structure in the world, and Kimura et al.¹ investigated the αH-PyBTM and doped αH-PyBTM crystals by magnetoluminescence and fluorescence instrument. Those two different instruments formed different results for doped αH-PyBTM. Because of that, Raman, NMR, ESR, and X-ray, can be used to test the αH-PyBTM and doped αH-PyBTM. 

In the ¹H NMR spectroscopy, when the PyBTM dope into αH-PyBTM, the % of crystal will be changed, then the NMR peaks are less shape and size should be smaller because there are less hydrogen in the crystal, and it will affect peak in the spectra. Besides, there should be one peak in the spectra, and chemical shift should be near around 1.5-3.0 ppm because there are three aromatic rings near the hydrogen, and chemical shift will be increased. 

What is an Example of Crystal Structure?

In the Raman Spectroscopy, there is a sample which shows a huge difference between undoped crystal and doped crystal in Figure 2, it should be a smaller difference when PyBTM is doped into αH-PyBTM because of the vibrational modes of molecules. When there is more doping, the bond strength of C-H is lower, and it will affect the peak in the spectra. Because of that, the shape and size of the peak is lower and smaller, and there should be one peak near the very low Raman shift. 

In the ESR spectroscopy, there must be a huge difference between undoped crystal and doped crystal because the ESR spectroscopy tests about unpaired electrons and radicals. Since ESR spectroscopy becomes tested on unpaired electrons, the signal in the spectra becomes bigger and sharper because there are more radicals in the αH-PyBTM. However, there shouldn’t be any signal in the pure αH-PyBTM because there’s no radical in it. 

Finally, in the X-ray spectroscopy, different chain of crystal structure becomes presented when a crystal becomes doped. So it should work for PyBTM is doped into αH-PyBTM. However, since this experiment use similar molecules, there should be a little or probably no differences between undoped and doped αH-PyBTM by many % of doping. 

Specific aim and objectives

1. Firstly, find examples of crystal doping studied with different instruments.
2. Secondly, learn X-ray and ESR instruments. Since in the instrument class in college, it doesn’t cover learning of X-ray and ESR instruments, so X-ray and ESR instruments are new challenge for this proposal.

3. Thirdly, study the αH-PyBTM crystal structure by several instruments.
4. Lastly, our final goal is to investigate PyBTM doped into αH-PyBTM crystals with NMR, Raman, ESR, and X-ray. Since the instrument class in college doesn’t cover learning of X-ray and ESR instruments, X-ray and ESR instruments are a new challenge for this proposal.

Methods

Table 2. Measured different % doping of PyBTM dope into αH-PyBTM.

sample	dopant	weight %
S1	PyBTM	0.05
S2	PyBTM	0.10
S3	PyBTM	0.90
S4	PyBTM	2.60
S5	PyBTM	5.50
S6	PyBTM	10.00
S7	PyBTM	14.00
S8	PyBTM	23.00

PyBTM crystal are doped into αH-PyBTM by different % of doping is shown in Table 2, in ¹H NMR after 4 samples are prepared, a few of sample is placed into NMR rotors, and rotors are used in the NMR instrumentation, finally, NMR spectrum is collected, in addition, the Raman Spectroscopy,  a few crystals of same samples are placed into the Raman melting point tube, and Raman spectrophotometer with an excitation beam from an argon-ion laser of wavelength 514.5 nm.⁵ Furthermore, those samples become determined by Raman instrumentation. And Raman spectrum becomes collected, in the ESR Spectroscopy. Moreover, a few of same samples become placed into the ESR test tube. And follow those parameters:⁴

1. Microwave power: 0.402 mW. 
2. Modulation amplitude: 0.88 G. 
3. Time constant: 10.24 ms. 
4. Scan range: 200 G.

Those samples are determined by ESR instrumentation, and the ESR spectrum is collected in the X-ray Spectroscopy, and the same samples are stretched on a hot plate for 5 mins. Then the

samples are taken out of the crystals and the surfaces were rinsed lightly with methanol and wiped clean with filter paper, the doped samples are sealed into glass and taken for X-ray diffraction measurement.⁵

Impact and significance

In this research, it’s a totally new research based on a new crystal, so there are many impacts in it. First of all, it may not have any results in some ways, but the only thing for sure is it must have results in the ESR, Raman and NMR spectroscopy because there’s a radical in the PyBTM. Raman and NMR, we expect to show doping will affect those spectra results. However, X-ray spectroscopy not expected to show differences.

Finally, if this research is successful, it will have a huge significance because no one has done this research before, and maybe there is some useful status in the PyBTM and doped PyBTM. It’s very helpful for future research and technologies. 

What is an Example of Crystal Structure? Written by Shawn Wang

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References

1. Kimura, S.; Kusamoto, T.; Kimura, S.; Kato, K.; Teki, Y.; Nishihara, H. Magnetoluminescence in a Photostable, Brightly Luminescent Organic Radical in a Rigid Environment. Angew. Chem. Int. Ed. 2018, 57, 12711–12715.
2. Majzoub, E. H.; Herberg, J.L. Stumpf, R.; Spangler, S.; Maxwell, R.S. XRD and NMR investigation of Ti-compound formation in solution-doping of sodium aluminum hydrides: solubility of Ti in NaAlH4 crystals grown in THF. J. Alloys. Compd. 2005, 394, 265–270.
3. Prawer, S.; Nemanich, R. J. Raman spectroscopy of diamond and doped diamond. Phil. Trans. R. Soc. Lond. A. 2004, 362, 2537–2565.
4. Trihi, M.; Duroux, J. L.; Hyvernaud, M. J.; Bernard, M. Study of Free Radicals in Irradiated PMMA (Doped or Undoped) using ESR Spectroscopy. ,Appl. Radiat. Isot. 1996, 47, 1561-1563
5. Tashiro, K.; Kobayashi, M.; Kawai, T.; Yoshino, K. Crystal structural  change in poly(3-alkyl  thiophene)s induced by iodine doping as studied by an organized combination of X-ray diffraction, infrared/Raman spectroscopy and computer simulation techniques. Polymer. 1997, 38, 2867-2879.

Hattori, Yohei; Kusamoto, Tetsuro; Nishihara, Hiroshi. Luminescence, Stability, and Proton Response of an Open-Shell (3,5-Dichloro-4-pyridyl)bis(2,4,6 trichlorophenyl)methyl Radical. Angew. Chem. Int. Ed, 2014, 53, 11845-11848.

What is an Example of Crystal Structure? Written by Shawn Wang

Science

What is an Example of Crystal Structure?