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Ultra-Rapid Crystallization of L-Alanine Using Monomode Microwaves, Indium Tin Oxide and Metal-Assisted and Microwave-Accelerated Evaporative Crystallization
摘要： The use of indium tin oxide (ITO) and focused monomode microwave heating for the ultra-rapid crystallization of L-alanine (a model amino acid) is reported. Commercially available ITO dots (< 5 mm) attached to blank poly(methyl)methacrylate (PMMA, 5 cm in diameter with 21-well silicon isolators: referred to as the iCrystal plates) were found to withstand prolonged microwave heating during crystallization experiments. Crystallization of L-alanine was performed at room temperature (a control experiment), with the use of two microwave sources: a 2.45 GHz conventional microwave (900 W, power level 1, a control experiment) and 8 GHz (20 W) solid state, monomode microwave source with an applicator tip that focuses the microwave field to a 5-mm cavity. Initial appearance of L-alanine crystals and on iCrystal plates with ITO dots took 47 ± 2.9 min, 12 ± 7.6 min and 1.5 ± 0.5 min at room temperature, using a conventional microwave and focused monomode microwave heating, respectively. Complete evaporation of the solvent using the focused microwaves was achieved in 3.2 ± 0.5 min, which is ~52-fold and ~172-fold faster than that observed at room temperature and using conventional microwave heating, respectively. The size and number of L-alanine crystals was dependent on the type of the 21-well iCrystal plates and the microwave heating method: 33 crystals of 585 ± 137 μm in size at room temperature > 37 crystals of 542 ± 100 μm in size with conventional microwave heating > 331 crystals of 311 ± 190 μm in size with focused monomode microwave. FTIR, optical microscopy and powder X-ray diffraction analysis showed that the chemical composition and crystallinity of the L-alanine crystals did not change when exposed to microwave heating and ITO surfaces. In addition, theoretical simulations for the binding of L-alanine molecules to ITO and other metals showed the predicted nature of hydrogen bonds formed between L-alanine and these surfaces.
关键词： ITO,Microwave heating,Silver island films,Evaporative crystallization
更新于2025-09-23 15:22:29
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Comparative Measurements of Photoelectron Emission in Bulk Samples and Island Films of Silver
摘要： The photoelectron emission has been studied of silver island films excited by a laser pulse of 10-ns duration at three wavelengths: 355, 532, and 1064 nm. It has been shown that, for wavelengths of 355 and 532 nm, the photoemission of island films significantly differs from the photoemission of a bulk sample. For an island film, dependence on the pulse energy characteristic for single-photon emission has been observed at a 355-nm wavelength. It has also been shown that the surface plasmon resonance in nanoparticles significantly affects the photoemission and character of its dependence on the energy of the laser pulse.
关键词： laser pulse,photoelectron emission,nanoparticles,silver island films,surface plasmon resonance
更新于2025-09-04 15:30:14