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The objective of this study was to research the performance of the electrospun polystyrene-acrylic resin composite nanofibre on the adsorption of gaseous aromatic compounds, such as benzene and chlorobenzene. The equilibrium adsorption amount of benzene was 254.3 μg mg-1, while the equilibrium adsorption amount of chlorobenzene was 2.5 μg mg-1. The dynamic adsorption of the two compounds onto the composite nanofibres was also studied. Comparing with the conventional adsorbent (Tenax-TA), the performace of this nanofibre was well as that of Tenax-TA. The results of comparison confirm that electrospun nanofibres can be a potential adsorbent for the sampling of gaseous aromatic compounds.

In order to detect the environmental pollutants in water sample with high sensitivity, an automatic method based on a combined preconcentration setup and flow injection system was developed. A novel packed fiber solid phase extraction (PFSPE) cartridge packed with electrospun nanofiber was first designed to adsorb environmental pollutants from water media in an online manner. Rhodamine B (RB) was selected as a model pollutant. Under the optimized conditions, a good linearity of wide range between 25-1000 ng mL-1 was achieved. The LOD was 7.5 ng mL-1. The method was applied to analysis RB in water samples with satisfactory results.

A novel micro-extraction procedure was developed through the use of an electrospun polymer nanofiber as a solid-phase extraction (SPE) sorbent to directly extract benzimidazoles in pork. The target compound was then monitored by a high performance liquid chromatography with ultraviolet detector (HPLC-UV) system. The eluted solvent was investigated meanwhile. Under the optimized conditions, a linear response for benzimidazoles over the range of 20-1000 ng mL−1 was achieved with the γ2 >0.99. The recoveries were in the range of 95.4%~101.2%. RSDs of intra-day and inter-day assays were 3.5%~6.3% and 5.7%~9.9%. The method is simple, sensitive, accurate and repeatable, which can be used for the determination of benzimidazoles in pork.

Due to the limitation of the hole injection, p-type doping is essential to improve the performance of InGaN/GaN multiple quantum well light-emitting diodes (LEDs). In this work, we propose and show a depletion-region Mg-doping method. Here we systematically analyze the effectiveness of different Mg-doping profiles ranging from the electron blocking layer to the active region. Numerical computations show that the Mg-doping decreases the valence band barrier for holes and thus enhances the hole transportation. The proposed depletion-region Mg-doping approach also increases the barrier height for electrons, which leads to a reduced electron overflow, while increasing the hole concentration in the p-GaN layer. Experimentally measured external quantum efficiency indicates that Mg-doping position is vitally important. The doping in or adjacent to the quantum well degrades the LED performance due to Mg diffusion, increasing the corresponding nonradiative recombination, which is well supported by the measured carrier lifetimes. The experimental results are well numerically reproduced by modifying the nonradiative recombination lifetimes, which further validate the effectiveness of our approach. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore) Published version

Laser lift-off technique was employed to carry out transfer of prefabricated InGaN multiple-quantum-well light-emitting diodes (LEDs) from sapphire onto Cu substrate. Silver epoxy was used as the bonding material. Characterization results showed tremendous device improvements in terms of maximum allowable current, light output power, and reliability from the use of conductive Cu substrate. LEDs on Cu could withstand a maximum current of 530 mA before breakdown while those on sapphire could only withstand 350 mA. At 40 mA, light output power of LEDs on sapphire and Cu was 0.74 and 0.95 mW, respectively. In addition, reliability test at constant current of 300 mA showed improvement in light output power for LEDs on Cu whereas LEDs on sapphire suffered deterioration with time.