Growth and Spectroscopic Characteristics of Yb^3+:LiGd(WO_4)_2 Crystal

The Yb3＋：LiGd（WO4）2 crystal with the dimension of Ф15×35 mm3 was grown by Czochralski technique. The spectroscopic characterization and fluorescence dynamics of Yb3＋ in yb3＋：LiGd（WO4）2 crystal were investigated. The yb3＋：LiGd（WO4）2 crystal exhibits a broad absorption band centered near 975 nm with the linewidths of 16 and 11 nm and maximal absorption cross-section of 3.60 × 10-20 and 2.90× 10-20 cm2 for π- and σ-polarization, respectively. The emission broadband has an FWHM of 47 and 45 nm with the emission cross sections of 3.92 × 10-20 and 3.34× 10-2o cm2 at 1020 nm for re- and or-polarization, respectively. The measured fluorescence lifetime is 398 gs. The blue light emission around 480 nm through cooperative upconversion from the de-excitation of excited Yb3＋-Yb3＋ pairs at 4 K was observed under 932-nm excitation and demonstrated.

Electrochemical and spectroscopic characteristics of dissolved organic matter in a forest soil profile

Dissolved organic matter （DOM） represents one of the most mobile and reactive organic compounds in ecosystem and plays an important role in the fate and transport of soil organic pollutants, nutrient cycling and more importantly global climate change. Electrochemical methods were first employed to evaluate DOM redox properties, and spectroscopic approaches were utilized to obtain information concerning its composition and structure. DOM was extracted from a forest soil profile with five horizons. Differential pulse voltammetry indicated that there were more redox-active moieties in the DOM from upper horizons than in that from lower horizons. Cyclic voltammetry further showed that these moieties were reversible in electron transfer. Chronoamperometry was employed to quantify the electron transfer capacity of DOM, including electron acceptor capacity and electron donor capacity, both of which decreased sharply with increasing depth. FT-IR, UV-Vis and fluorescence spectra results suggested that DOM from the upper horizons was enriched with aromatic and humic structures while that from the lower horizons was rich in aliphatic carbon, which supported the findings obtained by electrochemical approaches. Electrochemical approaches combined with spectroscopic methods were applied to evaluate the characteristics of DOM extracted along a forest soil profile. The electrochemical properties of DOM, which can be rapidly and simply obtained, provide insight into the migration and transformation of DOM along a soil profile and will aid in better understanding of the biogeochemical role of DOM in natural environments.

Isosteroidal Alkaloids from Fritillaria verticillata Willd. and Their NMR Spectroscopic Characteristics

Chemical investigation of Fritillaria verticillata Willd.led to the isolation of eight novel isosteroidal alkaloids(1—4,6,9—11)and four known alkaloids(5,7—8,12),including three unprecedented cis-fused D/E(13α,17α)cevanine alkaloids(1—3),one rarely cis-fused E/F(22α)cevanine alkaloid(6),and one uncommon 5β-jervine-type isosteroidal alkaloid featuring a cis-fused A/B ring moiety(11).In order to establish the structures of 1,the calculated NMR with DP4+evaluation was applied from the plausible structure candidates.The characteristic proton signals for distinguishing D/E conjunction of cevanine alkaloids were summarized.In addition,some proton and carbon signalsαto nitrogen in 6 and 7 are unobservable due to the 14N nuclear quadrupolar relaxation,based on the NMR experiments in different solvents,calculated NMR method and X-ray technology,their structures were determined.The NMR characteristics of cevanine alkaloids to distinguish orientation of long-pair on nitrogen atom withβ-hydroxyl at C-20 were also concluded.The anti-inflammatory effects of compounds 1 and 4 were evaluated in LPS-activated RAW 264.7 macrophages.Compound 4 decreased LPS-induced releases of IL-1βand IL-17αin RAW264.7 cells in a dose-dependent manner.Further mechanistic study revealed that 4 suppressed the phosphorylation of IκBαand p65 subunit to regulate the NF-κB signaling pathway.

Optical-Electrical Characteristics and Carrier Dynamics of Semi-Insulation GaAs by Terahertz Spectroscopic Technique

OaAs has been widely used to fabricate a variety of optoelectronic devices by virtue of its superior performance, and it is very important to accurately measure its electrical and optical properties. In this study, a semi- insulation （SI） GaAs wafer is investigated by the terahertz （THz） non-destructive testing technology. Using an air biased coherent generation and detection THz time domain spectroscopy system, the THz time domain waveform and spectrum of SI-GaAs are obtained by the time domain spectroscopy module, and its optical- electrical characteristics including complex refractive index, permittivity and dielectric loss angle are calculated. Its carrier lifetime is measured by the optical-pump THz-probe module, and the THz pulse induced intervalley scattering in photo-excited SI-GaAs is discussed.

Spectroscopic and lasing characteristics of 1,3,5,7-tetramethyl-8-ethyl-pyrromethene-BF_2 complex

The basic optical properties of the newly synthesized pyrromethene-BF2 derivative (Compound 1) were investigated systematically by its ultraviolet to visible (UV-visible) absorption, fluorescence and triplet-triplet absorption. Its lasing characteristics were measured on a dye laser system pumped by a continuous wave Ar ion laser. The results suggest that, compared with the typical pyrromethene-BF2 dye such as P-546, Compound 1 possesses stronger fluorescence and lower triplet-triplet absorption over its fluorescence spectral region. Excellent laser properties were also observed for Compound 1. It outperforms the commercially available benchmark laser dye rhodamine 6G in laser wavelength tuning range, which proves that Compound 1 is probably a potential candidate to be developed as the all-solid-state laser material.

Characterization of humic substances in bio-treated municipal solid waste landfill leachate

Considerable organic matter remains in muni- cipal solid waste landfill leachate after biological treat- ments. Humic substances （HSs） dominate the organic matter in bio-treated landfill leachate. In this study, the HSs from landfill leachate treated by membrane bioreactor （MBR-HSs） were analyzed via elemental analysis, ultra- violet-visible spectroscopy, Fourier transform infrared spectroscopy, and charge polarized magic-angle spin- ning-~3C-nuclear magnetic resonance. The characteristic absorption in the UV wavelength range indicated the presence of high C=C and C=O double bonds within the MBR-HSs. Compared with commercial HSs, MBR-HSs had lower carbon content [48.14% for fulvic acids （FA） and 49.52% for humic acids （HA）], higher nitrogen content （4.31% for FA and 6.16% for HA）, lower aromatic structure content, and higher carbohydrate and carboxylic atoms of carbon content. FA predominantly had an aliphatic structure, and HA had less condensed or substituted aromatic ring structures than natural HA. The aromatic carbon content of MBR-HSs was lower than that of humus-derived HSs but higher than that of waste- derived HSs, indicating that MBR-HSs appeared to be more similar to humus-derived HSs than waste-derived HA.

Polarized spectral analysis of Er^(3+) ions in Er^(3+)/Yb^(3+):LiLa(MoO_4)_2 crystal

Optical characteristics and upconversion dynamics of Er3+ in Er3+/Yb3+:LiLa(MoO4)2 crystals were investigated. The absorption spectra, fluorescence spectra and the fluorescence decay curves were analyzed at room temperature. The infrared emission at 1538 nm and visible emissions at 520–569 and 640–670 nm, corresponding to 2H11/2,4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions, were simultaneously observed in Er3+/Yb3+:LiLa(MoO4)2 crystals under 976 nm excitation at room temperature. The maximal emiss...