Zhao Xiujian

Structure, Upconversion and Fluorescence Properties of Er3+-Doped TeO2-TiO2-La2O3 Tellurite Glass

Tellurite glasses were generally applied in rare earth optical materials due to their excellent physical and chemi- cal properties. In this study, novel tellurite glasses composed of Te02-Ti02-La203 were prepared by conventional melting- quenching method. Some basic physical parameters such as density, refractive indices, transition temperature and crystal- line temperature were measured. The structure was analyzed by Raman spectra. The absorption, upconversion and fluores- cence spectra were measured by UV-Vis-NIR spectrophotometer and spectrofluorimeter . Under 980 nrn laser excitation, upconversion luminescence centered at 531, 545 and 657 nm corresponding to the transition 4Hll/2-+4115/2, 4s3/2+4115/2 and 4Fg/244115/2 respectively, were observed. The effects of Ti02 concentration on structure and upconversion lumines- cence intensity were discussed. The result indicated that the upconversion intensity increased as the phonon concentration decreased. The fluorescence properties of Er3+ doped glass were also studied. The dominant peak centered at 1531 nm and full width at half maximum (FWHM) was 64 nm. The E? + stimulated emission cross-section was calculated on the basis of McCumber theory. The possible mechanism of upconvesion and fluorescence were proposed.

Broadband infrared luminescence from bismuth-doped GeS2-Ga2S3 chalcogenide glasses

Near-infrared luminescence is observed from bismuth-doped GeS2—Ga2S3 chalcogenide glasses excited by an 808 nm laser diode. The emission peak with a maximum at about 1260 nm is observed in 80GeS2-20Ga2S3:0.5Bi glass and it shifts toward the long wavelength with the addition of Bi gradually. The full width of half maximum (FWHM) is about 200 nm. The broadband infrared luminescence of Bi-doped GeS2-Ga2S3 chalcogenide glasses may be predominantly originated from the low valence state of Bi, such as Bi+. Raman scattering is also conducted to clarify the structure of glasses. These Bi-doped GeS2-Ga2S3 chalcogenide glasses can be applied potentially in novel broadband optical fibre amplifiers and broadly tunable laser in optical communication system.

Plasma Activation of Integrated Carbon Nanotube Electrodes for Electrochemical Detection of Catechol

In this study, integrated multi-wall carbon nanotube (MWCNT) electrodes were prepared in the holes of glass directly by microwave plasma chemical vapour deposition (MWPCVD). The electrochemical behaviour of catechol at the integrated MWCNT electrodes was investigated. The oxygen plasma treated CNT electrodes had better electrochemical performance for the analysis of catechol than that of as-synthesized CNT electrodes. Both the as-synthesized CNTs and plasma treated CNTs were characterized by TEM(transmission electron microscopy, XPS(X-ray photoelectron spectroscopy) and Raman spectroscopy. The results revealed that the oxygen plasma activation is an effective method to enhance the electrochemical properties of CNT electrodes.

Microstructural probing of (1−x) GeS2−x Ga2S3 system glasses by Raman scattering

Raman scattering measurement of (1−x) GeS2−xGa2S3 system glasses was conducted in order to understand the microstructural change caused by the addition of Ga2S3. According to the change of Raman spectra with the addition of Ga2S3, two main structural transformations were deduced: the gradual enhancement of ethane-like structural units S3Ge−GeS3 (250 cm−1) and S3 Ga−GaS3 (270 cm−1) and the appearance of charge ambalanced units [Ga2S2(S1/2)4]2− and [Ga(S1/2)4]− And this change of structural aspect seems to give us a clue to understanding the cause of the increased rare-earth solubility.

CeO2-TiO2/SiO2 Anti-Reflecting and UV-Shielding Double-Functional Films Coated on Glass Substrates Using Sol-Gel Method

Abstract CeO2-TiO2/SiO2 double-layered films were coated on glass substrates using sol-gel method. The films, formed using spin-coating process, had two optical properties at the same time, anti-reflection in visible region and ultraviolet rays (UV) shielding. The films could be used as museum windows, commercial high-resolution displays and so on. These films were composed of CeO2 and TiO2 with molar ratio of 50 to 50 in the first layer and silica matrix in the 2nd layer. Furthermore, the 2nd layer was composed of porous silica films, which showed a lower refractive index, reducing the reflectance significantly in visible wavelength region. The reflectance of the films in visible region between 400 × 700 nm was lower than 2%, and almost 100% UV was shielded. The surface roughness of the films was observed through an atomic force microscope, a depth composition profile of the double layered film was measured with an X-ray photoelectron spectrometer (XPS).

Microstructure and thermal properties analysis of (1−x) As2S3−xCdBr2 glass system

The homogeneous glass sample for the (1−x)As2S3−xCdBr2, where x=0.015, 0.035, 0.05, was prepared by the conventional melt-quenched method. Amorphous (1−x)As2S3−xCdBr2 alloys were determined by X-ray diffraction, thermal comprehensive analysis and Raman scattering. The glass transition temperature (Tg) decreases a bit with the addition of CdBr2. Based on the experimental data, the microstructure is considered to be the discrete molecule species of AsBr3 and Cd−S atomic bonds or clusters are homogeneously dispersed in a disordered polymer network formed by AsS3 pyramids interlinked by sulfur bridges.

Microstructure and thermal properties of (1−x) As2S3−xCdCl2 glassy system

The homogenous glass samples of the (1−x) As2S3−xCdCl2 where x=0 and 0.05 were prepared by the conventional melt-quenched method. The addition of 5 mol% CdCl2 enhanced the glass transition temperature of pure As2S3 glass sample by about 30°C. Based on the experimental data, the microstructure is considered to be that the discrete molecule species of AsCl3 and nanocrystal CdS is homogeneously dispersed in the disordered polymer network formed by AsS3 pyramids interconnected by sulfur bridges.

IR spectra analysis of SiO2−TiO2−GeO2 gel glass of CO2 laser transmitting hollow waveguide

Both titanium and germanium were introduced into silicon dioxide system by sol-gel method to move its region of anomalous dispersion caused by IR resonance absorption towards the wavelength of CO2 laser. It is indicated by IR absorption spectra that as the content of SiO2 decreases in this glass system TiO2 and GeO2 tends to exist in their own phases. As for the gel glass with a composition of 40 SiO2·30TiO2·30GeO2, when the temperature is below 600°C, germanium atoms exist mainly in Ge−O−Ge bonds. With the temperature increasing from 800°C to 1000°C, titanium atoms in Si−O−Ti bonds abmost transform into Ti−O−Ti bonds. Furthermore, a large number of Si−O−Ti and Si−O−Ge bonds formed when the temperature approaches 800°C, which makes a notable IR absorption band round the wavelength of CO2 laser. Therefore, sol-gel based SiO2−TiO2−GeO2 gel glass is a candidate material for CO2 laser hollow waveguide.

Synthesis of Au nanorods in a low pH solution via seed-media method

The gold (Au) nanorods with various aspect ratios are obtained by a seed-media method in low pH growth solution. Transmission electron microscopy (TEM) and UV-visible spectrophotometry are utilized to characterize the Au nanorods, and the longitudinal absorption peak positions of Au nanorods show different shifting trends of the growth evolutions in various low pH (1~3) solutions. Other influential factors on the shape of Au nanorod are also systematically studied under low pH reaction condition. The positions of longitudinal peak shift between 600 nm and 900 nm, with the aspect ratios of Au nanorods varying from 2 to 5 both in the simulation and experimental results. The simulation results are in agreement with experimental ones.

Large and Ultrafast Third-Order Nonlinear Optical Properties of Ge-S Based Chalcogenide Glasses

We report ultrafast third-order nonlinear optical (NLO) properties of several chalcogenide glasses GeSx (x = 1.8, 2.0, 2.5) measured by femtosecond time-resolved optical Kerr gate technique at 820 nm. The third-order nonlinear susceptibility of GeS1.8 glass is determined to be as large as 1.41×10−12 esu, which is the maximum value of the third order nonlinear susceptibility χ(3) for the three compositions investigated. The symmetric Gauss profiles of optical Kerr signals reveal the nature of ultrafast nonlinear response of these samples, which are originated from the ultrafast polarization of the electron clouds. By detailed microstructural analysis of these glasses based on the chain-crossing model (CCM) and the random-covalent-network model (RCNM), it can be concluded that χ(3) value of GeSx glasses can be enhanced greatly by S–S covalent bonds or S3Ge–GeS3 ethane-like units.