Materials Science Forum Vols. 663-665

Abstract: Trivalent rare-earth ions, Dy3+, Yb3+, Pr3+, Ho3+, Tm3+, have been investigated as the co-doped auxiliary sensitizer for the electron trapping materials SrS:Eu2+ in order to enhance the fluorescence properties. It is found that Dy3+ and Ho3+ has the optimum photoluminescence stimulated luminescence (PSL) effect among the selected trivalent rare-earth ions. All the SrS: Eu2+ samples coped by different trivalent rare-earth ions can be stimulated by 980 nm laser after exposing to the conventional sun light, and they emit PSL with the peak located at 615 nm. The present research also indicates that some co-doped rare earth ions can increase fluorescence intensities of the traditional electron trapping materials SrS: Eu2+.

Abstract: Two novel polythiophenes with 1,3-dioxane group in the side chain named poly[3-(1,3-dioxane-2-ylethyl)thiophene] (PDT) and poly[3-(1,3-dioxane-2-ylethyl)-4-methyl- thiophene] (PDMT) were synthesized via oxidative polymerization firstly to form their precursor polymers and substitution secondly to obtain the target polymers in this paper. The chemical structures, molecular weights, thermal properties of the polymers were characterized by 1H NMR, FT-IR, GPC, and TGA respectively, indicating that both polymers had high molecular weight and good thermal stability. Meanwhile, the optical absorption and photoluminescence (PL) of both polymers were investigated and the results showed that the maximum absorption and emission wavelengths of PDMT were blue-shifted than that of PDT due to its methyl-substitution at 4-position in thiophene.

Abstract: Anodic aluminum oxide (AAO) film with nanopore arrays was prepared by one-step anodization of highly pure aluminum foil. Morphology, structure and photoluminescence property of AAO were characterized. Results showed that AAO owned honeycomb structure which was characterized by close-packed arrays of columnar hexagonal cells, each containing a central pore normal to the substrate. There were three peaks at around 370, 385 and 470 nm in the PL spectrum of AAO, which should be mainly attributed to the oxygen vacancies.

Abstract: This paper reports a study on fluorescence sensing properties of cadmium telluride (CdTe) quantum dots (QDs) film under exposure of volatile organic compounds; ethanol, 2-propanol and acetone. The high luminescence QDs were synthesized using a wet-chemical process. CdTe QDs film was deposited onto the surface of fiber optic probe by drop-casting method. The fluorescence properties of the film were studied by observing the change of photoluminescence (PL) spectra of the films in nitrogen (N2) and after exposing in organic vapors. It was observed that the PL of the film was quenched by the presence of the organic vapors. The amount and the rate of quenching are depended on the kind of the organic vapors

Abstract: By varying the antimony dopant level in the sol-gel solutions, we prepared a series of antimony-doped SnO2 films on slide glass with the sol-gel technique. The transmission, absorption, photoexcitation and photoemission spectra were measured for the sol-gel derived antimony-doped SnO2 films. Under the 300 nm excitation, near untraviolet emission at 390nm and blue emission at 460 nm were recorded from thermally annealed antimony-doped SnO2 films. The effect of the ionic dopant on the photoluminescent properties of the antimony-doped SnO2 films are discussed.

Abstract: Two synchronized operating modes of femtosecond and picosecond pulses, cross mode-locking and multi-pulse operating, are presented in a two-beam-pumped dual-wavelength Ti:sapphire laser. For the cross mode-locking mode, synchronized laser pulses of 37.5 fs and 0.891ps, with a timing jitter of 139 fs, are obtained in the femtosecond cavity and picosecond cavity, respectively. For the multi-pulse mode, pulses of 35 fs are obtained in the femtosecond cavity, whereas, multi-pulse mode appears in the picosecond cavity, with a pulse envelope width of 1.06 ps. The two operating modes can be switched from one to the other, dominated mainly by the mutual interaction between cross-phase modulation and self-amplitude modulation.

Abstract: The optical absorption and photoluminescence (PL) of 5-(2-pyrrolyl)-2-pyrrolidinone were investigated with ultra-visible absorption spectroscopy and photoluminescence spectrscopy. Upon the 325 nm excitation from a helium-cadmium laser, strong blue PL was recorded for the 5-(2-pyrrolyl)-2-pyrrolidinone. The peak of the PL was located at about 425 nm (2.92 eV). The origin of the strong PL can be assigned to isolated carbonyl group.

Abstract: Porous silicon (PS) of uniform structure was prepared by electroless silver deposition on surface of silicon at near room temperature in HF-AgNO3 system solution. Morphology of PS was characterized by scanning electron microscopy. The results showed that the diameter of hole was 1-2μm and holes distributed regularly. The ethylene diamine tetra acetic acid (EDTA) was an important additive to control the etching rate of silicon, which is of great significance to research the mechanism of porous silicon formation. Furthermore, photoluminescence property of PS was characterized.

Abstract: Based on the diffusion approximation theory, when the laser pulse transmitting through the turbid media, its energy will be attenuated and the pulse shape will be changed by the scattering and absorption. In this paper, Mathematics equations of the ultra short Gauss laser pulse in different pulse width tp are given, the reflective pulses with the boundary condition of semi-infinite homogeneous media are discussed. We get the simulation results of reflective intensity and the reflective pulse shape of different tp based on the diffusion equation. From the results, we know that the ultra short Gauss laser pulse will be widened by the diffusive scattering. Besides, we find that the various medium parameters will influence the reflection of the Gauss laser pulse very differently. With the boundary condition of semi-infinite homogeneous media, the influence of the absorption, the scattering, and the anisotropy coefficient will be also changed by the different tp of ultra short Gauss laser pulse. All the conditions mentioned above have been investigated in the present paper. This study will be very useful for the measurement of optical properties of tissue.

Abstract: A soluble polypyrrole without any substituent groups was obtained by controlling the oxidation level of polypyrrole in the presence of oxygen. Upon the exposure to the 325 nm ultraviolet excitation from a helium-cadmium laser, thin films of the non-substituted polypyrrole could give off strong photoluminescence with its peak at about 530 nm. To elucidate the origin of the recorded strong photoluminescence, we measured the absorption spectra of the polypyrrole thin films with ultraviolet-visible absorption spectroscopy and our data indicated the appropriately oxidized polypyrrole are free of polarons. With the help of the electronic structures calculated with Hückel tight-binding method, the intense photoluminescence is interpreted in terms of the direct electronic transitions from the conduction band to valence band of the conjugated polymer.