Search

The figure of SEM, XRD and the nonlinear refractive and nonlinear absorption versus laser power.

A serial of Er3+∶Ag-bismuth glass nanocomposites were prepared by the conventional melting-quenching method.The effect of nano-silver addition on the emission intensity of Er3+ was investigated.The experimental results indicate that Ag nanoparticles of mass fraction of 0.2% drastically enhances the intensity(~4.6 times) of 1.53 μm emission bands of Er3+.Local field enhancement induced by Ag0 surface plasmon resonance(SPR) and energy transfer from fluorescent Ag0→Er3+ ions are found to be responsible for this enhancement.

In order to output the ideal infrared fluorescence matrix glass,a serial of chalcogenide glasses based on Ge-Ga-S-KBr system doped with different Er3+ concentrations are synthesized by a melt-quenching technique.The refractive indexes,absorption spectra,mid-infrared emission spectra of samples are measured.The oscillator strengths of absorption lines of Er3+ ions are calculated using the absorption spectra.The intensity parameters(Ωi,i=2,4,6),transition probabilities(A),branching ratios(β) are predicted for Er3+ ions in the samples using the Judd-Ofelt theory.The mid-infrared emission properties are investigated for the samples with the different Er3+ concentrations under 808 nm laser excitation.The 2.8 μm-emission cross-section is calculated using the theory of the Futchbauer-Ladenburg.The results indicate that the fluorescence under 808 nm excitation with peak wavelength at 2.8 μm is due to the Er3+∶4I11/2→4I13/2 transition.The intensity of the mid-infrared fluorescence is enhanced by increasing the concentration of the Er3+ from 0.4 wt% to 1.0 wt%.Multiphonon relaxation rate is estimated to be 37 s-1 for the Er3+∶4I11/2 level.

In the present study, a simple approach has been presented to in situ deposition of Pd-doped well-crystallized SnO 2 nanocrystals on the surface of multiwalled carbon nanotubes (MWCNTs) in the ethanol solution of SnCl 2 . The morphology, microstructure and surface chemistry of the as-prepared nanocomposites were characterized by high resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. The HRTEM and XRD results show that the well-crystallized SnO 2 nanocrystals with uniform crystal size (about 5 nm) tightly and homogenously coat on the entire surface of the MWCNTs. The carboxylic function groups on the MWCNTs surface may supply nucleation sites for facilitating the in situ deposition of SnO 2 nanocrystals. The XPS results reveal that the chemical states of the nanocomposites and the dopant of Pd mainly exists in two chemical states as Pd 2+ and Pd 4+ . The response of the 2.5 at% Pd-doped SnO 2 /MWCNTs nanocomposites to 1000 ppm NO at the temperature of 250 °C behaviors better, whose response time is about 70 s and the sensitivity is about 4.62.

Pyroelectric materials take the most important role in pyroelectric infrared detectors. A high temperature above 550°C is required to obtain the traditional pyroelectric films such as PZT, BST, etc., which would hold back the realization of integration of pyroelectric thin film monolithic uncooled focal plane array (UFPA). Zinc oxide (ZnO) has been studied widely in recent years because of its excellent semiconducting, optical, piezoelectric and pyroelectric multiple properties. All these imply its potential applications in photo-catalysis, composite materials, dye-sensitized solar cells, sensors, as well as in UFPA applications. In the wurtzite structure of ZnO, it is easy to replace Zn by doping other metal elements such as Al, Ga, In, Sn, Cr, Mg, etc. for tailoring its properties. Thus an ideal preparation method is demanded to easily control the particle size, size distribution, crystallinity and morphology. On the other hand, the structureperformance relationship of ZnO in pyroelectric applications is still not clear. In the present work, we developed a surfactant-assisted complex sol-gel method, which allows easily control of the particle size, size distribution, crystallinity, morphology and doping of ZnO nanoparticles. Two types of ZnO nanoparticles including pure ZnO and magnesium doped ZnO were prepared for our investigation. Their detailed morphology, structural, optical properties would be presented. Pure wurtzite structure was obtained after 500°C calcinations for the sample with the Mg concentration in MgxZn1-xO below 10 at%. Well dispersed ZnO-based nanoparticles with uniform size distribution were obtained using PEG 2000 as a surfactant. The as-obtained ZnO-based nanoparticles were also sintered for pyroelectric property test. Their pyroelectric properties were compared in order to reveal its possible applications as target materials for pyroelectric films preparation in infrared detector arrays.