Reduction mechanism of tioglycolic acid on keratin fibers using microspectrophotometry and FT-Raman spectroscopy

In order to investigate the reduction mechanism of thioglycolic acid (TG) on the keratin fibers, cross-sectional samples of white human hair treated with TG were prepared. The heterogeneous reaction between TG and keratin fibers involving the diffusion of TG into human hair was analyzed at the molecular level using microspectrophotometry and FT-Raman spectroscopy. The diffusion of TG into human hair clearly increased by increasing the treatment time and by raising pH. The TG relative concentration and the disconnected relative concentration of disulfide (–SS–) groups at various depths of the hair samples with pH 9.0 were in good agreement, indicating that the reaction rate (the disconnection of –SS– groups) was faster than the diffusion rate of TG into human hair. From these experiments, we demonstrated that TG diffuses gradually beyond the cuticle region, and toward the inside of the cortex region along with the disconnection of –SS– groups.     

傅里叶变换拉曼光谱在食品行业的应用

人们对于食品行业历来有着很高的关注度,食品检测、食品安全等各方面都成为了企业和社会关注的焦点问题。随着检测技术的不断发展,傅里叶变换拉曼(Fourier transform Raman, FT-Raman)光谱技术作为一种能够快速、无损、准确的光谱分析方法,已经在农业、医学、考古学等领域证明了其价值,在食品行业也得到了越来越多的应用。各种研究报告表明,除了仅通过光谱的视觉差异信息进行物质判别之外,FT-Raman光谱结合化学计量工具或与其他光谱手段进行联合分析,提供了更多可以应用在食品行业的高效检测、判别手段。本文简述了有关FT-Raman光谱技术的一些基本原理,综述了近10年(2010～2019)中FT-Raman光谱在食品行业中的应用,并对其未来的发展趋势进行了展望。     

Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures

The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga_1 − xIn_xN_yAs_1 − y/GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated.     

FT-RAMAN CHARACTERIZATION OF METHYL ACRYLATE-ETHYL ACRYLATE COPOLYMERS

Vibrational spectra of a series of Methyl Acrylate/Ethyl Acrylate (MA/EA) copolymers, synthesized at 60°C and 70°C for 5 different MA/EA compositions for each temperature, were obtained by FT-Raman spectroscopy. An inversion of the symmetric and antisymmetric stretching vibrations of the CH₃ group, due to the mobility of this group, was found. By analyzing the acoustical and optical branches of the spectra, the mobility of the backbone structure was also determined. The EA homopolymer was found to posses the highest conformational order.     

Thermal, Optical, and Electrical Properties of Gel Grown ZMTC

The bimetallic thiocyanate of the group IIB divalent d¹⁰ ions Zn²⁺ and Hg²⁺ having unique characteristics: The pale color and high thermal stability—Zinc Mercury tetrathiocyanate (ZMTC) is chosen for growth and study. ZMTC is grown in silica gel by chemical reaction method and characterized by single crystal XRD, FTIR, FT-Raman, UV-Vis-NIR, NLO, TGA/DTG, DSC, AC conductivity, and dielectric studies. It has wide transparency window and possesses high second harmonic generation efficiency. Its thermal stability is very high. The dielectric permittivity of this material is very low.     

Chemical synthesis of highly stable PVA/PANI films for supercapacitor application

Polyvinyl alcohol (PVA)/polyaniline (PANI) thin films were chemically synthesized by adopting two step process: initially a thin layer (200 nm) of PVA was spin coated by using an aqueous PVA solution onto fluorine doped tin oxide (FTO) coated glass substrate, afterwards PANI was chemically polymerized from aniline monomer and dip coated onto the precoated substrate. The thickness of PANI layer was varied from 293 nm to 2367 nm by varying deposition cycles onto the precoated PVA thin film. The resultant PVA/PANI films were characterized for their optical, morphological and electrochemical properties. The FT-IR and Raman spectra revealed characteristic features of the PANI phase. The SEM study showed porous spongy structure. Electrochemical properties were studied by electrochemical impedance measurement and cyclic voltammetry. The electrochemical performance of PVA/PANI thin films was investigated in 1 M H₂SO₄ aqueous electrolyte. The highest specific capacitance of 571 Fg⁻¹ was observed for the optimized thickness of 880 nm. The film was found to be stable for more than 20,000 cycles. The samples degraded slightly (25% decrement in specific capacitance) for the first 10,000 cycles. The degradation becomes much slower (10.8% decrement in specific capacitance) beyond 10,000 cycles. This dramatic improvement in the electrochemical stability of the PANI samples, without sacrificing specific capacitance was attributed to the optimized PVA layer.     

FT－IR及联用技术在复合材料领域中的应用

概括介绍了新型傅里叶变换红外光谱仪（ＦＴ－ＩＲ）与配套装置（包括反射附件、显微镜、气相色谱、热重仪和傅里叶拉曼光谱）的特点及其在复合材料领域中的应用。     

Spectroscopic and structural studies of di-ureasils doped with lithium perchlorate

Di-urea cross-linked POE/siloxane hybrid ormolytes (di-ureasils) doped with a wide concentration range of lithium perchlorate trihydrate (LiClO₄·3H₂O) (200 ≥ n ≥ 0.5, where n expresses the salt content in terms of the number of ether oxygen atoms per Li⁺ ion) have been analysed by Fourier transform infrared and Raman (FT-IR and FT-Raman, respectively) spectroscopies and X-ray diffraction (XRD). The results obtained lead us to conclude that the xerogels with n ≥ 5 are totally amorphous. At n ≤ 1 free salt is observed. “Free” ClO₄⁻ ions appear to be the main charge carriers at the conductivity maximum located within the 25 ≤ n ≤ 8 composition range of this family of ormolytes. At n = 15 ClO₄⁻ ions coordinated in mono/tridentate (C_3v symmetry) and bidentate (C_2v symmetry) configurations were detected. In salt-rich samples with n < 15 there is a marked tendency for ionic association. The resulting decrease that occurs in the concentration of “free” ions is consistent with the observed significant decrease of the ionic conductivity. The analysis of the “amide I” and “amide II” regions provided solid proof that the Li⁺ ions bond to the urea carbonyl oxygen atoms over the entire range of salt concentration studied.     

光导纤维在傅里叶变换红外及拉曼光谱中的发展及应用

本文简要介绍了光导纤维传输光的基本原理,总结了近红外和中红外波长范围的光导纤维的实际应用状况及其近年来光导纤维材料的发展与改进,并对光导纤维在傅里叶变换近红外光谱(FT-NIR)、中红外光谱(FT-MIR)及傅里叶变换拉曼光谱(FT-Raman)中的广泛应用作了综述。