Photocatalytic activity of neodymium ion doped TiO?for 2- Mercaptobenzothiazole degradation under visible light irradiation

Author name used in this publication: F. B. LiAuthor name used in this publication: X. Z. LiAuthor name used in this publication: K. W. Cheah2004-2005 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Optical properties of a novel yellow fluorescent dopant for use in organic LEDs

In this paper, the optical properties of a novel organic, 2,8-di(t-butyl)-5,11-di[4(t-butyl) phenyl]-6,12-diphenylnaphthacene (tetra(t-butyl)rubrene) have been investigated. Our results show that there are two peaks in the photoluminescence (PL) spectra of tetra(t-butyl)rubrene (TBRb) which are also confirmed in the electroluminescence (EL) spectra. Photo-quenching of the PL intensity is observed when the irradiation time increases. It is shown that oxidation is the dominant reason for photo-quenching. The absolute refractive index and absorption coefficient have also been determined and the results correlate well with the PL results. The results show that TBRb can be a good dopant to achieve the Förster energy transfer and to assist light emission. The optical properties of TBRb are similar to those of rubrene; however, the PL of TBRb is much stronger than that of rubrene. Finally, although crystalline organics have been commonly reported by heating the sample, we report crystallization of TBRb at low temperature <230 K when the TBRb film is in an amorphous form before cooling. © Springer-Verlag 2004.postprin

Photoluminescence of transparent strontium–barium–niobate-doped silica nanocomposites

Author name used in this publication: C. L. MakAuthor name used in this publication: K. H. Wong2001-2002 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Optical Properties of a Novel Dye in Yellow Florescent Organic LEDs

In this paper, time-resolved PL, lifetime and crystallization of a novel organic, 2,8-di(t-butyl)-5,11-di[4(t-butyl)phenyl]-6,12-diphenylnaphthacene, which is considered to be potential candidate to substitute the conventionally used 5,6,11,12-tetraphenylnaphthacene for a higher efficient yellow-color organic LED, were investigated. The PL intensity will reduce when the irradiation time increases because of photo-quenching. It is shown that oxidation is the dominant reason for photo-quenching. In addition, TBRb has two lifetimes. The short one is /spl sim/5 ns and the long one is /spl sim/31 ns. They are considerably contributed by the short PL peak and long PL peak respectively. Furthermore, we first report, to the best knowledge, crystallization of TBRb at low temperature of 11 K and with irradiation.published_or_final_versio

Enhanced photocatalytic activity of Ce??-TiO?for 2-mercaptobenzothiazole degradation in aqueous suspension for odour control

Author name used in this publication: F. B. LiAuthor name used in this publication: X. Z. Li2004-2005 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Visible photoluminescence in ZnO tetrapod and multipod structures

The investigation of the properties of ZnO tetrapod and multipod structures using scanning electron microscopy, X-ray diffraction, photoluminescence (PL) and electron paramagnetic resonance (EPR) spectroscopy was discussed. The ZnO samples were fabricated by heating a mixture of ZnO, GeO2 and graphite at 1100°C in order to modify the morphology of the fabricated structures. The room temperature of PL was measured by using a HeCd laser excitation source (325 nm). It was found that the green PL was due to transition between a shallow donor and deep acceptor in the absence of g ≈ 1.96 EPR signal and transition between the conduction band and deep acceptor in the absence of g ≈ 1.96 EPR signal.published_or_final_versio

Acceptors in undoped gallium antimonide

Undoped GaSb materials were studied by temperature dependent Hall (TDH) measurements and photoluminescence (PL). The TDH data reveals four acceptor levels (having ionization energies of 7meV, 32meV, 89meV and 123meV) in the as-grown undoped GaSb samples. The 32meV and the 89meV levels were attributed to the GaSb defect and the VGa-related defect. The Ga Sb defect was found to be the important acceptor responsible for the p-type nature of the present undoped GaSb samples because of its abundance and its low ionization energy. This defect was thermally stable after the 500°C annealing. Similar to the non-irradiated samples, the 777meV and the 800meV PL signals were also observed in the electron irradiated undoped GaSb samples. The decrease of the two peaks' intensities with respect to the electron irradiation dosage reveals the introduction of a non-radiative defect during the electron irradiation process, which competes with the transition responsible for the 777meV and the 800meV PL peaks.published_or_final_versio

NiOZnO light emitting diodes by solution-based growth

Heterojunction NiOZnO light emitting diodes have been fabricated using low temperature solution-based growth methods. While negligible light emission has been obtained for the as-grown NiO film, devices with annealed NiO film exhibit room-temperature electroluminescence (EL), which was attributed to the detrimental effects of nickel oxide hydroxide in as-grown NiO layers. The device performance can be further modified by insertion of the organic layers between NiO and ZnO and the EL spectra exhibited dependence on the bias voltage. For higher bias voltages, strong UV-violet emission peak can be obtained in spite of the dominance of defect emission in the photoluminescence spectra. © 2008 American Institute of Physics.published_or_final_versio

Green photoluminescence in ZnO nanostructures

In photoluminescence (PL) spectrum of ZnO, typically one or more peaks in the visible spectral range due to defect emission can be observed in addition to one UV peak due to band edge emission. The origin of the defect emission is controversial and several mechanisms have been proposed. In this work, we fabricated ZnO nanostructures with different methods (evaporation and chemical synthesis). We found that the preparation method influences the peak position of the defect emission. Different hypotheses for the origin of the green emission in our nanostructured samples are discussed. © 2005 American Institute of Physics.published_or_final_versio

ZnO nanorods grown on ZnSe particles by the chemical vapor deposition method

A novel structure of ZnO nanorods on microsized ZnSe particles has been prepared through a chemical vapor deposition technique using Zn and Se powders as the sources. The dimension of the nanorods can be controlled by adjusting the growth temperature, time and the Zn∈:∈Se ratio. Through the investigation of the effects of synthesis time and Zn∈:∈Se ratio on the formation of ZnO nanorods on ZnSe microparticles, it is proposed that the synthesis of the ZnO-ZnSe structures involves a two-stage formation. The growth of ZnO nanorods can be described by the vapor-solid mechanism. The photoluminescence of the ZnO-ZnSe structures has also been studied.postprin