Quorum Sensing Disruption in Vibrio harveyi Bacteria by Clay Materials.

This work describes the use of clay minerals as catalysts for the degradation of quorum sensing molecule N-(3-oxooctanoyl)-dl-homoserine lactone. Certain clay minerals as a result of their surface properties and porosity can catalytically degrade the quorum sensing molecule into smaller fragments. The disruption of quorum sensing by clay in a growing Gram-negative Vibrio harveyi bacteria culture was also studied by monitoring luminescence and population density of the bacteria, wherein quenching of bacterial quorum sensing activity was observed by means of luminescence reduction. The results of this study show that food-grade clays can be used as biocatalysts in disrupting bacterial activity in various media.

Fabrication of Au/ZnO Schottky nanodiode using mesoporous silica film as template.

Au/ZnO Schottky nanodiode is prepared by two-step electrodeposition, using mesoporous silica (MPS) film as template. Nano-ZnO is firstly deposited in the pores of MPS film, which achieves enhanced conductivity and enables continued electrodeposition of Au to form an Au/ZnO Schottky nanodiode. Current-voltage (I-V) curves of Au/ZnO nanodiode are recorded under a switched UV-light with the wavelength of 365 nm. The characteristic I-V curves show rectifying behavior in the dark, and present more linear Ohmic response upon UV exposure, which might be caused by the lowered Schottky barrier height and narrowered Schottky barrier width. In addition, fast increased forward-current and lowered breakdown voltage are observed from I-V curves of Au/ZnO Schottky nanodiode. The ideality factor of the Au/ZnO Schottky diode is determined to be approximately 8. These results suggest a different photocurrent-generation process, and provide experimental support to the model proposed in ultrasmall Schottky diodes.

Synthesis of a three-dimensional cubic mesoporous silica monolith employing an organic additive through an evaporation-induced self-assembly process.

We demonstrate a robust approach to the synthesis of a 3D cubic Im3m mesoporous silica monolith from SiO2/cetyltrimethylammoniumbromide (CTAB)/1,3,5-triisopropylbenzene (TIPB) sols having molar compositions of 1SiO2/0.0017HCl/5.2H2O/10EtOH/0.10CTAB/0.1-0.5TIPB by the evaporation-induced self-assembly (EISA) process. The addition of TIPB is aimed at altering the micelle geometry to spheroid from rodlike in the gel state; the change in micelle geometry leads to the formation of a 3D cage-type cubic mesostructure in the monolith. The synthesized materials exhibit BET surface areas of 800-1000 m(2)/g, a BJH pore diameter of 2.9-4.3 nm, and a pore volume of 0.7-1.0 cm(3)/g, demonstrating ultrahigh porosity of the 3D cubic mesostructure.

Versatile fabrication of distorted cubic mesoporous silica film using CTAB together with a hydrophobic organic additive.

We have succeeded in the fabrication of distorted cubic R-3m mesoporous silica film with 3D open mesostructure providing high pore accessibility from the surface-air interface of the film. The film fabrication involves a unique approach of adding 1,3,5- triisopropylbenzene (TIPB) to the silica/cetyltrimethylammoniumbromide (CTAB) coating sol during its preparation. The addition of TIPB induces the formation of spheroid micelles, promoting R-3m mesostructure in the film. This phase does not exist in the corresponding binary phase diagram of CTAB surfactant.

Investigation on the drying induced phase transformation of mesoporous silica; a comprehensive understanding toward mesophase determination.

Phase transformation of mesoporous silica during the drying process is investigated. As-synthesized hexagonal p6mm obtained under the conditions used in this study is transformed to cubic Ia3d as drying proceeds, even at room temperature. Prolonged synthesis results in the formation of a well-ordered hexagonal mesophase, with almost no phase transformation. Drying at a higher temperature promotes the phase transformation of not only hexagonal to cubic, but also cubic to lamellar mesophases. Release of water is detected during drying, which is followed by the phase transformation of the mesophases. The phase transformations observed here proceed against the direction estimated on the basis of the state-of-the-art understanding. Here, considering the degree of silicate condensation and the amount of residual water in the as-synthesized mesoporous silica, a comprehensive explanation of mesophase determination is proposed including thermodynamic and kinetic aspects to account for the results observed here and those in the literature.