Introduction to Terahertz Spectroscopy of Amorphous Molecular Materials
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- Опубліковано 7 чер 2024
- In this video Professor Axel Zeitler gives a tutorial on the basic principles of using terahertz time-domain spectroscopy (THz-TDS) to explore the materials properties of organic molecular materials in their disordered, amorphous state.
The talk outlines the link between the spectra of organic molecular crystals, which exhibit sharp vibrational modes in the far-infrared at terahertz frequencies, and the vibrational density of states (VDOS) that is observed instead for disordered materials when such molecular crystals have been turned into amorphous glasses. By varying the temperature of the sample during terahertz spectroscopy experiments it is possible to explore the vibrational dynamics using THz-TDS. The talk shows how THz-TDS links with dielectric spectroscopy at lower frequencies and (far-)infared spectroscopy at higher frequencies.
00:00 Introduction
00:44 Vibrational Spectroscopy at Terahertz Frequencies
08:31 Relaxation Processes and Vibrational Dynamics
13:36 Measuring Molecular Mobility
25:44 Conclusions
References:
S. Capaccioli, K. L. Ngai, M. S. Thayyil, and D. Prevosto, Coupling of Caged Molecule Dynamics to JG β-Relaxation: I, J. Phys. Chem. B, 119(28):8800-8808, July 2015.
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M. Goldstein, Viscous Liquids and the Glass Transition: A Potential Energy Barrier Picture, J. Chem. Phys., 51(9):3728, 1969.
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S. Kastner, M. Köhler, Y. Goncharov, P. Lunkenheimer, and A. Loidl, High-frequency dynamics of type B glass formers investigated by broadband dielectric spectroscopy, J. Non-Cryst. Sol., 357(2):510-514, January 2011.
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E. P. J. Parrott and J. A. Zeitler, Terahertz Time-Domain and Low-Frequency Raman Spectroscopy of Organic Materials, Appl Spectrosc, 69(1):1-25, January 2015.
doi.org/10.1366/14-07707
M. T. Ruggiero, J. Sibik, J. A. Zeitler, and T. M. Korter, Examination of l-Glutamic Acid Polymorphs by Solid-State Density Functional Theory and Terahertz Spectroscopy., J. Phys. Chem. A, 120(38):7490-7495, September 2016.
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M. T. Ruggiero, M. Krynski, E. O. Kissi, J. Sibik, D. Markl, N. Y. Tan, D. Arslanov, W. van der Zande, B. Redlich, T. M. Korter, H. Grohganz, K. Löbmann, T. Rades, S. R. Elliott, and J. A. Zeitler, The significance of the amorphous potential energy landscape for dictating glassy dynamics and driving solid-state crystallisation., Phys. Chem. Chem. Phys., 19(44): 30039-30047, November 2017.
doi.org/10.1039/C7CP06664C
J. Sibik, S. R. Elliott, and J. A. Zeitler, Thermal decoupling of molecular-relaxation processes from the vibrational density of states at terahertz frequencies in supercooled hydrogen-bonded liquids, J. Phys. Chem. Lett., 5(11):1968-1972, 2014.
doi.org/10.1021/jz5007302
J. Sibik and J. A. Zeitler, Direct measurement of molecular mobility and crystallisation of amorphous pharmaceuticals using terahertz spectroscopy., Adv. Drug Del. Rev., 100:147-157, May 2016.
doi.org/10.1016/j.addr.2015.1... - Наука та технологія
Very less content in UA-cam about terahertz , thank you sir
thanks for this video, I was introduced to the THZ science around 30 Years ago.
There are endless possibilities :-)
Very interesting information. What kind of a device delivered the results you showed in this video? Thanks.
We use a TeraView spectra 4000 for our experiments shown in this video. More information is probably best found of the website by the company (www.teraview.com). If there is interest in seeing more of the equipment we can definitively make a video in due course walking through the equipment.
As others have mentioned here, there is a device out there called IteraCare. There are multiple versions of this "blow dryer" that range in price from $430US for the classic to over $4,000US for the Pro version. I would REALLY appreciate your opinion on these devices. Such as... are these devices just a scam? (a blue light for aiming, a blow dryer for heat, and I have to assume some other part of the device responsible for producing the terahertz beam.) These devices range in power from 600 watts to 1500 watts, are hand held, and plug into a normal wall outlet.
I heard positive results from testimonies. I am also interested to know if its a scam.
Can back scattered, low frequency Raman (10-2000cm-1, 0.3-60THz) give the full Vibrational Density of States curve and thus be a viable method to study materials? Perhaps the excessive laser power of the Raman method, or possibly the optical properties of the sample in the Vis/NIR range exclude Raman for these types of experiments?
That's a very good point. Raman, THz and other methods, such as neutron scattering, are absolutely complementary at this frequency range just like they are at higher energies. There have been a number of excellent studies such as the ones from Copenhagen in the late 1970s and 1980s, for example see P.A. Lund et al., Chem. Phys. 28, 167 (1978), but also many others since who have used low frequency Raman scattering methods to study these phenomena in organic molecular materials.
Each method has their own challenges and, as you noted already, fluorescence and laser induced heat transfer are additional difficulties that need to be taken into account but they can be controlled. Other aspects to consider are that the Raman signal typically is scattered from a surface and hence surface properties of a sample may dominate compared to the molecular properties from the bulk of the sample. For the same reason it can be a little difficult to make quantitative measurements with the Raman methods compared to terahertz spectroscopy, which can be acquired from films of well-defined thickness in transmission. In addition, given that the beam diameter in terahertz spectroscopy is typically a few mm, compared to the laser excitation in Raman spectroscopy which is normally focused to much smaller spots, it helps measuring the average response of a material which may have tiny cracks or minute density fluctuations over length-scales of micrometres.
There is a very good book that summarises the interesting physics of liquids and amorphous solids in a rigorous fashion: W. Schirmacher, Theory of Liquids and Other Disordered Media (Springer, 2014).
Lots of methods are useful to understand these materials and terahertz spectroscopy is one of them - it may prove to become a very powerful tool for this field of research but it certainly won't give all the answers.
@@terahertzapplicationsgroup3532 Thanks for the excellent response. This range of the spectrum seems under-explored and ripe for new discoveries. Its great work and I thank you for spending the time to share it with the world. After some reading and understanding what is required just to generate photons in the THz range really made me appreciate the investment that you and the team must have done.
It will be exciting to see what material mysteries you may uncover in your journey.
Thanks for sharing
Are there photos of this device?
We use a TeraView spectra 4000 for our experiments shown in this video. More information is probably best found of the website by the company (www.teraview.com).
Could two electrolysis units mechanically connected generate a vacuum, with one of them producing a vacuum for stabilizing a plasma field in conjunction with piezoelectric charge reversals? If these electrolysis units have been previously modified by CO2 and calcite crystals, as well as high-energy ions and hydroxyl radicals. If the absorption of photon radiation or indirect photon radiation can be improved with it. The electrolyte is liquid and consists of salt. It could be divided, and a portion of it could be used to form salt crystals. When the salt crystals are exposed to high ultraviolet radiation without a filter, could it promote photoelectric fields, static fields, in connection with the same electrolyte fluid, either attraction or plasma formation? Perhaps even unusually high proportional energy gains? Da die Farbstrucktur der Salz eingefärbt sein könnte, eventurell?
Sir, can you take apart a THz health device I possess and tell me exactly how it works so that I can learn in a simple way to explain to those of us who have this device. As well, understanding THz is one thing. Knowing that my device truly captures the 3 core technology that it says it does is yet another . Looking for truth here. Skeptics are looking for verification and viability. I don’t want to share something that is a fake.
Does your device work? Someone suggested it to recently but I don't have any reviews on it.