Hongshun Hao

Characteristics of N-Acylhomoserine Lactones Produced by Hafnia alvei H4 Isolated from Spoiled Instant Sea Cucumber

This study aimed to identify N-acylhomoserine lactone (AHL) produced by Hafnia alvei H4, which was isolated from spoiled instant sea cucumber, and to investigate the effect of AHLs on biofilm formation. Two biosensor strains, Chromobacterium violaceum CV026 and Agrobacterium tumefaciens KYC55, were used to detect the quorum sensing (QS) activity of H. alvei H4 and to confirm the existence of AHL-mediated QS system. Thin layer chromatography (TLC) and high resolution triple quadrupole liquid chromatography/mass spectrometry (LC/MS) analysis of the AHLs extracted from the culture supernatant of H. alvei H4 revealed the existence of at least three AHLs: N-hexanoyl-l-homoserine lactone (C6-HSL), N-(3-oxo-octanoyl)-l-homoserine lactone (3-oxo-C8-HSL), and N-butyryl-l-homoserine lactone (C4-HSL). This is the first report of the production of C4-HSL by H. alvei. In order to determine the relationship between the production of AHL by H. alvei H4 and bacterial growth, the β-galactosidase assay was employed to monitor AHL activity during a 48-h growth phase. AHLs production reached a maximum level of 134.6 Miller unites at late log phase (after 18 h) and then decreased to a stable level of about 100 Miller unites. AHL production and bacterial growth displayed a similar trend, suggesting that growth of H. alvei H4 might be regulated by QS. The effect of AHLs on biofilm formation of H. alvei H4 was investigated by adding exogenous AHLs (C4-HSL, C6-HSL and 3-oxo-C8-HSL) to H. alvei H4 culture. Biofilm formation was significantly promoted (p < 0.05) by 5 and 10 µM C6-HSL, inhibited (p < 0.05) by C4-HSL (5 and 10 µM) and 5 µM 3-oxo-C8-HSL, suggesting that QS may have a regulatory role in the biofilm formation of H. alvei H4.

Preparation and photoelectric properties of Ho3+-doped titanium dioxide nanowire downconversion photoanode

Abstract Ho3+-doped titanium dioxide (TiO2:Ho3+) downconversion (DC) nanowires were synthesized through a simple hydrothermal method followed by a subsequent calcination process after being immersed in Ho(NO3)3 aqueous solution. Moreover, TiO2:Ho3+ nanowires (HTNWs) were used as the photoanode in dye-sensitized solar cells (DSSCs) to investigate their photoelectric properties. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to characterize the morphology and structure of the material, respectively. The photofluorescence and ultraviolet–visible absorption spectra of HTNWs reveal a DC from the near and middle ultraviolet light to visible light which matches the strong absorbed region of the N719 dye. Compared with the pure TNW photoanode, HTNWs DC photoanodes show greater photovoltaic efficiency. The photovoltaic conversion efficiency (η) of the DSSCs with HTNWs photoanode doped with 4% Ho2O3 (mass fraction) is two times that with pure TNW photoanode. This enhancement could be attributed to HTNWs which could extend the spectral response range of DSSCs to the near and middle ultraviolet region and increase the short-circuit current density (Jsc) of DSSCs, thus leading to the enhancement of photovoltaic conversion efficiency.

Multistep Controllability Synthesis and Growth Mechanism of ZnO Nanopagoda for Schottky Diode Device

Ordered ZnO arrays with a peculiar nanostructure were synthesized by a multistep synthesis process. The first step was the preparation of ZnO seed to induce the formation of ZnO array via potentiostatic electrodeposition method using a typical three electrode set-up. The second step was fabricating ZnO array along seed by Chemical Bath Deposition. Structural analysis of ZnO was carried out with X-ray diffraction (XRD), which showed a hexagonal wurtzite structure, and the selected area electron diffraction (SAED) patterns indicated that nanocrystalline is a part of monocrystal. The scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to study the microstructure, and showed a pagoda-like microstructure with a tiny top and large bottom, which had an average top diameter of exceeding 800nm at seed-depositing time of 60s, and then growth mechanisms are subsequently given a further explanation, viewed from kinetics and thermodynamics. In addition, the current–voltage curves of...

A Phase Separation Route to Synthesize α-Fe 2 O 3 Porous Nanofibers via Electrospinning for Ultrafast Ethanol Sensing

A facile and economic procedure was provided to synthesize α-Fe2O3 nanofibers. In this procedure, porous α-Fe2O3 nanofibers were obtained by a single-polymer/binary-solvent system, while solid α-Fe2O3 nanofibers were prepared by a single-polymer/single-solvent system. The crystal structure and morphology of both samples were characterized by x-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption/desorption isotherms. The formation mechanism of porous structure was based on solvent evaporation-induced phase separation by the use of mixed solvents with different volatility. Furthermore, ethanol-sensing performance of the porous α-Fe2O3 nanofibers was evaluated and compared with solid α-Fe2O3 nanofibers. Results from gas-sensing measurements reveal that porous α-Fe2O3 nanofibers exhibit higher sensitivity and slightly longer recovery time than solid α-Fe2O3 nanofibers. Over all, the gas sensor based on porous α-Fe2O3 nanofibers shows excellent ethanol-sensing capability with high sensitivity and ultrafast response/recovery behaviors, indicating its potential application as a real-time monitoring gas sensor.

Synthesis and performance of Ca-α/β-SiAlON composites from tailings

Ca-α/β-SiAlON composites were prepared using Ca-α/β-SiAlON powder synthesized from gold ore tailings, which contained abundant Si and Al elements as the major raw materials together with minor additives, through a pressure-less sintering method. The influences of sintering temperature on the phase composition and microstructure of the composites were analyzed. The scanning electron microscopy images of the composites show the interlacing of grains with elongated columnar, short columnar and plate-like morphologies. The composites sintered at 1520°C for 6 h have a flexural strength of 352 MPa, Vickers hardness of 11.2 GPa, and fracture toughness of 4.8 MPa·m1/2. The relative content of each phase in the products is I(Ca-α-SiAlON):I(β-SiAlON):I(Fe3Si) = 23:74:3, where Ii stands for the diffraction peak intensity of phase i.