Abstract: In this paper, a micro-arc oxidation (MAO) approach is introduced for “in-situ” preparing TiO2 composite layer upon the surface of titanium alloy (Ti-6Al-4V) substrate. The surface morphologies, chemical compositions, crystal microstructure and photocatalytic properties of the layers were investigated by using a field emission scanning electron microscope (FE-SEM), energy dispersive spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), electro-chemical workstation and UV-Vis spectrophotometer. The experimental results revealed that photocatalytic performance of the TiO2 composite layers was much higher than that of the pure TiO2 layer and also exhibited absorption under the visible light irradiation.
Abstract: The aromatic triazole is an interesting electron-injection/transport chromophore because it possesses high electron affinity and thermal stability. In organic lighting-emitting diodes (OLEDs), highly electron-deficient triazole (Tz) derivates have been demonstrated to have more efficient electron-transport and hole-blocking characteristics and have a higher stability to high current density than the oxadiazole derivates. In this study, we have successfully synthesized a star-shaped soluble oligomer,4-(4-butylphenyl)-3,5-bis(4-(5'-hexyl-2,2'-bithiophen-5-yl)phenyl)-4H-1,2,4-triazole(Tz-2T-Hex) via Suzuki coupling reaction. The Tz-2T-Hex shows a red-shifted UV-vis absorption spectrum than Tz-Br with a maximum at 380 nm, due to the introduction of two bithiophene units at both ends. As film, Tz-2T-Hex showed the PL maximum at 530 nm. Tz-2T-Hex emitted light of a white color with the CIE coordinates (0.32 and 0.34).
Abstract: Thin films of Sn10Sb20Se70-XTeX (0≤X≤8) composition were deposited using thermal evaporation technique. As-prepared films were amorphous as studied by X-ray diffraction. Surface morphology studies revealed that films have surface roughness ~2 nm and av. grain size ~ 30 nm. Optical band gap Eg calculated from transmittance and reflectance data showed a sharp decrease for initial substitution of Se with Te upto 2 at%. Further substitution upto 4 at%, lead to a small increase in Eg value and thereafter it marginally decreased for further substitution beyond 4at%. The trend of optical band gap variation with tellurium content has been qualitatively explained using band model given by Kastner. The dc-conductivity measurements showed thermally activated conduction with single activation energy for the measured temperature regime and followed Mayer-Neldel rule. The dc-activation energy has nearly half the value as that of optical band gap that revealed the intrinsic nature of semiconductor. The annealing below glass transition Tg led to decrease in optical band gap as well as dc-activation energy that might be related to increase of disorder in material with annealing.
Abstract: This paper reports the preparation of exceptionally high brightness CdTe quantum dots (QDs) that gives emission in the range of green to red by simply prepared them in a binary mixture of octadecyl phosphonic acid (ODPA) and oleic acid (OA) surfactants. By easy controlling the ratio between the two surfactants in the reaction, the QDs with unique emission, high -brightness and -quantum yield (QY), ca. 63, 87 and 89% for green, yellow and red QDs respectively, can be obtained. Owing to their unique PL and high QY, the CdTe QDs should find an extensive uses in the currently existing applications.
Abstract: Lead-based glass samples were fabricated in a laboratory scale using quartz sands that was a by-product of feldspar floatation in Tak Province, northern Thailand, and 20-wt% commercial-grade PbO as the main compositions. A CdS/Se compound of ratios ranging from 1:1 to 1:10 was doped into the glass mixture. The dried powders were well mixed in a ceramic crucible before being melted in an electric furnace at a maximum temperature of 1100°C for 4 hours. Transparent and bubble-free glass samples were resulted after cooling down to room temperature. It was found that the glass colors were changed from colorless to reddish brown by the addition of CdS/Se compound. Physical properties of the samples, such as, color, specific gravity, and refractive index were studied. Specific gravity and refractive index increased with increasing ratio of CdS/Se. UV-VIS-NIR spectra were measured and discussed.
Abstract: In this paper, we introduce a simple and effective method to prepare ZnO nanorods using aqueous solutions. The morphology and structure properties of ZnO nanorods were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL). The SEM results indicated that the diameter of ZnO nanoroads was about 100 nm. The XRD pattern showed that the ZnO nanorods had high-purity wuruzite structure. The PL spectrum revealed that ZnO nanorods had a strong visible emission at 423 nm. The field emission (FE) properties of ZnO nanorods were also studied. The FE results showed that the turn-on field and threshold field were 24V/μm and 39V/μm, respectively.
Abstract: Ca3(VO4)2: Eu3+, Bi3+ phosphor powders were prepared by the combustion synthesis or the solid state reaction at room temperature, respectively. The phase composition, morphology and photo-luminescence of the Ca3(VO4)2: Eu3+, Bi3+ phosphors were investigated by X-ray diffraction, scanning electron microscope, and spectrophotometry, respectively. The results show that the Ca3(VO4)2: Eu3+, Bi3+ powder prepared by the combustion synthesis is claviform, while the Ca3(VO4)2: Eu3+, Bi3+ powder directly obtained by the solid state reaction at room temperature is orbicular. The discrepancy in emission is attributed to the variation in the Eu3+ morphology of in powders.
Abstract: A novel azobenzene optically polymer (P-DA) was synthesized based on the azo chromophore molecule, chiral reagent L(-)-tartaric acid, acryloyl chloride and methacrylate. The P-DA was characterized by FT-IR, UV-Vis spectroscopy, 1H NMR, DSC and TGA. The P-DA had high thermal stability up to its glass-transition temperature (Tg) of 110 oC and 5 % heat weight loss temperature of 199 oC. The UV-induced trans/cis photoisomerization and reflex-isomerization behaviors were investigated. The results indicated that the P-DA solution could undergo photochromism after irradiated by 365 nm UV light. The optical parameters: refractive index (n), the dielectric constant (ε) and thermal volume expansion coefficient (β) of P-DA were obtained. The thermo-optic coefficients are one order of magnitude larger than those of the inorganic materials, such as SiO2 (1.1×10−5 oC -1 and LiNbO3 (4×10−5 oC -1) and was larger than the organic material such as polystyrene (-1.23×10-4 oC -1) and PMMA (-1.20×10-4 oC -1). The conclusion had a little significance to develop optical communication.
Abstract: YVO4:Eu3+ red phosphor was prepared by combustion synthesis without any post heat treatment at 700 oC-900 oC, using urea, oxalate acid and metal nitrates as raw materials. The product can emit bright red light under ultraviolet light irradiation. The phase compositions and luminescence properties were studied via X-ray diffraction (XRD) and photoluminescence spectra. The experimental results indicated that addition of appropriate amount of fuel and oxalate acid is favorable for the improvement of luminescence intensity.