偏光光谱实验用聚乙烯醇膜的研制

报道了偏光光谱实验用聚乙烯醇 (PVA)膜的实验室制法 ,就我国南方湿热地区制膜的主要技术方法做了探讨。

纳米级分子取向行为的偏光光谱研究

用拉伸PVA膜法研究了属于D_(2h)、D_(3h)点群纳米级分子的取向行为,并用Tanizaki Y的解析理论给出了取向分布函数和取向角,指出可以利用取向角讨论单个纳米粒子的形状。

偏光光谱实验用高分子膜拉伸机的研制

本文介绍了一种特殊光谱实验技术--拉伸高分子膜法的基本原理,并阐述了用于该光谱实验的新研制的高分 子膜拉伸机的基本工作原理和优异结构功能。

Polarization Dependent Time-Resolved Infrared Spectroscopy and Its Applications

Polarization dependent time-resolved infrared （TRIR） spectroscopy has proven to be a useful technique to study the structural dynamics in a photochemical process. The angular information of transient species is obtainable in this measurement, which makes it a valuable technique for the investigation of electron distribution, molecular structure, and conformational dynamics. In this review, we briefly introduce the principles and applications of polarization dependent TRIR spectroscopy. We mainly focused on the following topics： （i） an overview of TRIR spectroscopy, （ii） principles of TRIR spectroscopy and its advantages compared to the other ultrafast techniques, （iii） examples that use polarization dependent TRIR spectroscopy to probe a variety of cheinical and dynamical phenomena including protein conformational dynamics, excited state electron localization, and photoisomerization, （iv） the limitations and prospects of TRIR spectroscopy.

Accurate Measurement of Raman Depolarization Ratio in Gaseous CO2

The Raman depolarization ratios of gaseous CO2 in the spectral range of 1240-1430 cm-I are determined with a sensitive photoacoustic Raman spectroscopy, and more accurate data compared to the literature results are presented. The precision of the obtained depolarization ratio is achieved by measuring and fitting the dependence of the PARS signal intensity on the cross angle between the polarizations of two incident laser beams.

Synthesis of Azoxy Dyes and Their Copper Complexes and Their Application on Polyvinyl Alcohol (PVA) Polarizing Film

Azoxy dyes and their copper complexes with maximum dichroism in the spectrum range from 550nm to 700nm were synthesized and used to prepare polyvinyl alcohol (PVA) polarizing films. These films showed excellent polarizing ability. In addition, a neutral gray polarizing film was prepared by mixing synthesized dichromatic dyes with other dyes. The obtained polarizable film for gray shade was little pervious to light over the visible radiation wavelength region, ranging from 400nm to 700nm at cross state, and excellent in the polarizing activities and stable to moisture and heat.

Novel measurement scheme of peak separation of side-hole fiber grating

There are two peaks of different polarizations in the reflection spectrum of the side-hole fiber grating and their separation interval has a linear variation along with the pressure changing while it is insensitive to the temperature.We have proposed a novel measurement scheme based on polarization detection.The detection of peak separation is achieved by measuring the two peaks’ center wavelengths separately with all polarization maintaining fiber system.The side-hole fiber grating pressure sensing within the range of 0～3.5 MPa is realized successfully with the new scheme.

Influence of signal-to-noise ratio on accuracy of spectral analysis by near infrared spectroscopy

As one of the important indicators of spectrometer,signal-to-noise ratio(SNR)reflects the ability of spectrometer to detect weak signals.To investigate the influence of SNR on the prediction accuracy of spectral analysis,we first introduce the major factors affecting the spectral SNR.Taking green tea as an example,the influence of spectral SNR on the prediction accuracy of the origin identification model is analyzed by experiments.At the same time,the relationship between the spectral SNR and prediction accuracy of spectral analysis model is fitted.Based on this,the common methods for improving the spectral SNR are discussed.The results show that the accuracy of the prediction set model first decreases slowly,then decreases linearly,and finally tends to be flat as the spectral SNR decreases.Through calculation,in order to achieve the prediction accuracy of prediction model reaching 90%and 85%,the spectral SNR is required to be higher than 23.42 dB and 21.16 dB,respectively.The overall results provide certain parameters support for the development of new online analytical spectroscopic instruments,especially for the technical indicators of SNR.

02（1△） Yield Measurement by Raman Spectroscopy With Elimination of Chlorine Fluorescence Interference

Deleterious chlorine fluorescence was found to occur at the same frequency as the Raman scattering of 02 （1 A） and 02 （3 E）, seriously affecting the 02 （1 A） yield measurement in the reaction of chlorine with basic hydrogen peroxide by use of the Raman spectroscopy technique. To solve this problem we have taken advantage of the fact that Raman radiation is always strongly polarized while fluorescence is essentially non-polarized in a gaseous medium. When chlorine utilization of a singlet oxygen generator is 88%, 02（1A） yield reaches （42.4±7.4）% with the effect of chlorine fluorescence completely eliminated.

Simultaneous determination mercury species of Su-He-Xiang-Wan in rat tissues by HPLC-CVG-AFS

A simple and sensitive high performance liquid chromatography-chemical vapour generation-atom fluorescent spectrometry （HPLC-CVG-AFS） method was developed and validated for simultaneous determination mercury species in Su-He-Xiang-Wan （SHXW） and in tissues of rats, respectively. The species of mercury were separated by a Venusil MP-C 18 （5μm, 150 mm×4.6 ram） column with the optimized mobile phase containing 5% （w/v） acetonitrile, 0.01 mol/L L-cysteine and 0.06 moL/L ammonium acetate. The tissues of rats were freeze-dried after giving the medicine for 10 d, and then added into the solution containing 10% （w/v） HC1, 1% （w/v） sulfocarbamide and 0.15% （w/v） KC1 for increasing extraction rate. The resolutions of Hg2＋, MeHg and EtHg were 1.5 and 2.9, respectively. The detection limits of Hg2＋, MeHg and EtHg were 2.0, 1.0 and 0.9 ng/mL, respectively. The relative standard deviation （RSD） of inter- and intra-day precisions ranged from 1.56% to 2.86%. The recovery rates of three different adding level were 87%-101% （n=6）, and the RSDs were smaller than 8.2%. The results show that no MeHg and EtHg were detected in rat tissues. Only soluble mercury （Hg2＋） was determined for the mercury species of SHXW in rat tissues.

Cloud Top Height Retrieval Using Polarizing Remote Sensing Data of POLDER

A retrieval method of cloud top heights using polarizing remote sensing is proposed in this paper. Using the vector radiative transfer model in a coupled atmosphere-ocean system, the factors influencing the upwelling linear polarizing radiance at top-of-atmosphere are analyzed, which show that the upwelling linear polarizing radiance varies remarkably with the cloud top height, but has negligible sensitivity with cloud albedo and aerosol scattering above the cloud layer. Based on this property, a cloud top height retrieval algorithm using polarizing remote sensing was developed. The algorithm has been applied to the polarizing remote sensing data of Polarization and Directionality of the Earth's Reflectances-2 (POLDER-2). The retrieved cloud top height from POLDER-2 compares well with the Moderate Resolution Imaging Spectroradiometer (MODIS) operational product with a bias of 0.83 km and standard deviation of 1.56 km.

Polarized upconversion luminescence from a single LiLuF_(4):Yb^(3+)/Er^(3+) microcrystal for orientation tracking

Polarized upconversion luminescence(UCL)of lanthanide-doped micro/nano-crystals has shown great promise in single-particle tracking and super-resolution bioimaging.However,because of the spectral line broadening and multiple sites of lanthanide in upconversion particles(UCPs),the crystal-field(CF)polarization components of UCL are usually undistinguishable.Herein,we report the linearly polarized UCL in LiLuF_(4):Yb^(3+)/Er^(3+) single microcrystals with resolvable CF transition lines and a polarization degree up to 0.82.The CF levels and CF transition lines of Er^(3+),as well as their emission polarization anisotropy,are unraveled for the first time through low-temperature and high-resolution photoluminescence(PL)and UCL spectroscopies.By taking advantage of the well-resolved and highly-polarized CF transition lines of Er^(3+),we demonstrate the application of LiLuF_(4):Yb^(3+)/Er^(3+) single microcrystals as anisotropic UCL probes for orientation tracking.These findings provide fundamental insights into the polarization anisotropy of UCL in lanthanide-doped single particles,thus laying a foundation for the future design of anisotropic luminescent probes towards versatile applications.

Enhanced visible-light photocatalytic activity of a g-C_3N_4/m-LaVO_4 heterojunction: band offset determination

Band offset is a dominant factor affecting the photocatalytic performance of heterostructure photocatalysts. Therefore, controlling the band gap structure of semiconductors is a key challenge in the development of efficient photocatalysts. We used a typical in situ-method to prepare diverse graphite-phase carbon nitride(g-C_3N_4)samples from melamine, thiourea, and a mixture thereof,and found that they exhibited band gaps between2.3–2.8 e V. From UV–Vis spectra and X-ray photoelectron spectroscopy measurements, we determined that the g-C_3N_4 samples exhibited different band gap values and valence band positions. On this basis, we constructed g-C_3N_4/m-La VO_4 heterojunctions with different band offsets. UV–Vis spectra and X-ray photoelectron spectroscopy measurements revealed that the valence band offsets(VBOs) of the different heterojunctions were similar, but their conduction band offsets(CBOs) were significantly different. Photocatalytic experiments revealed that the reaction rate was enhanced with an increase in the CBO value. Furthermore, the three-phase g-C_3N_4/g-C_3N_4/mLa VO_4 heterojunction composed of m-La VO_4 and mixed g-C_3N_4 showed the highest photocatalytic activity, which was mainly due to the construction of a multilevel structure. This work investigates the influence of the band offset on heterojunction photoelectrochemical properties and provides a new strategy to improve the photocatalytic activity by constructing multilevel structures.

Determination of soluble solid content and acidity of loquats based on FT-NIR spectroscopy

The near infrared （NIR） spectroscopy technique has been applied in many fields because of its advantages of simple preparation, fast response, and non-destructiveness. We investigated the potential of NIR spectroscopy in diffuse reflectance mode for determining the soluble solid content （SSC） and acidity （pH） of intact loquats. Two cultivars of loquats （Dahongpao and Jiajiaozhong） harvested from two orchards （Tangxi and Chun＇an, Zhejiang, China） were used for the measurement of NIR spectra between 800 and 2500 nm. A total of 400 loquats （100 samples of each cultivar from each orchard） were used in this study. Relationships between NIR spectra and SSC and acidity of loquats were evaluated using partial least square （PLS） method. Spectra preprocessing options included the first and second derivatives, multiple scatter correction （MSC）, and the standard normal variate （SNV）. Three separate spectral windows identified as full NIR （800-2500 nm）, short NIR （800-1100 rim）, and long NIR （1100-2500 nm） were studied in factorial combination with the preprocessing options. The models gave relatively good predictions of the SSC of loquats, with root mean square error of prediction （RMSEP） values of 1.21, 1.00, 0.965, and 1.16 °Brix for Tangxi-Dahongpao, Tangxi-Jiajiaozhong, Chun＇an-Dahongpao, and Chun＇an-Jiajiaozhong, respectively. The acidity prediction was not satisfactory, with the RMSEP of 0.382, 0.194, 0.388, and 0.361 for the above four loquats, respectively. The results indicate that NIR diffuse reflectance spectroscopy can be used to predict the SSC and acidity of loquat fruit.

Design of a sinc-sampled fiber Bragg grating fabricated in high birefringence fiber

In this paper we design a new kind of sinc-sampled fiber Bragg grating which is fabricated in high birefringence fiber (HBF). The sampled grating has two sets of reflection spectra along two perpendicular polarization directions. The grating's channel number can be doubled approximately by designing the refractive index difference between the fast and slow axes of the fiber, which enhances the utilization ratio and reduces the claim for photosensitivity of the fiber. The group delay characteristics are theoretically studied and side-lobes are depressed by apodization as well to get the optimized spectra. The results show that the comb-like spectra of the grating have promising applications in both multi-wavelength polarized fiber lasers and fiber sensing networks.

Polarized Light Microscopy and Spectroscopy of Individual Single-Walled Carbon Nanotubes

Polarized light microscopy （PLM） is used to image individual single-walled carbon nanotubes （SWNTs） suspended in air across a slit opening. The imaging contrast relies on the strong optical anisotropy typical of SWNTs. We combine PLM with a tunable light source to enable hyperspectral excitation spectroscopy and nanotube chirality assignment. Comparison with fluorescence microscopy and spectroscopy confirms the assignment made with PLM. This represents a versatile new approach to imaging SWNTs and related structures.

Strain-induced direct-indirect bandgap transition and phonon modulation in monolayer WS2

In situ strain photoluminescence （PL） and Raman spectroscopy have been employed to exploit the evolutions of the electronic band structure and lattice vibrational responses of chemical vapor deposition （CVD）-grown monolayer tungsten disulphide （WS2） under uniaxial tensile strain. Observable broadening and appearance of an extra small feature at the longer-wavelength side shoulder of the PL peak occur under 2.5% strain, which could indicate the direct-indirect bandgap transition and is further confirmed by our density-functional-theory calculations. As the strain increases further, the spectral weight of the indirect transition gradually increases. Over the entire strain range, with the increase of the strain, the light emissions corresponding to each optical transition, such as the direct bandgap transition （K-K） and indirect bandgap transition （F-K, ≥2.5%）, exhibit a monotonous linear redshift. In addition, the binding energy of the indirect transition is found to be larger than that of the direct transition, and the slight lowering of the trion dissociation energy with increasing strain is observed. The strain was used to modulate not only the electronic band structure but also the lattice vibrations. The softening and splitting of the in-plane E＇ mode is observed under uniaxial tensile strain, and polarization-dependent Raman spectroscopy confirms the observed zigzag-oriented edge of WS2 grown by CVD in previous studies. These findings enrich our understanding of the strained states of monolayer transition-metal dichalcogenide （TMD） materials and lay a foundation for developing applications exploiting their strain-dependent optical properties, including the strain detection and light-emission modulation of such emerging two-dimensional TMDs.

The Effects of Spherical Surface and Laser Polarization on the Photodetachment Cross Section of H^-

We report the combined effects of laser polarization and curvature of the spherical surface on the detached electron spectra from H-. The Theoretical imaging method is used as a tool of investigation. The photodetachment cross sections for various polaxization angles, radii of curvatures and inter ion surface distances axe displayed. The analysis of the spectra reveals that the laser polarization angle θL, curvature of the surface τc and inter ion surface distance d strongly affect oscillations in the spectra. Therefore, a fine control on the laser polaxization and that of curvature in the surface can be used to control oscillations in the photodetachment of negative ions.