Weichao Gu

The preliminary discharging characterization of a novel APGD plume and its application in organic contaminant degradation

An atmospheric pressure glow discharge plume (APGD-p) using a dielectric barrier discharge reactor with one conductive liquid electrode was designed in our study. The preliminary characteristics of the plume and application in the degradation of a dye, methyl violet 5BN (MV-5BN), were presented in this paper. The APGD reactor produced a cold plasma plume with temperature not higher than 320 K at power 5 - 50 W. The MV- 5BN solution as a probe for dye wastewater was treated by the downstream gases of the plasma plume. The results indicated that the active argon (Ar) and nitrogen (N-2) gases had little effect on the MV- 5BN degradation, but the air and oxygen (O-2) gas depleted the organic molecules effectively. In particular, the downstream O-2 gas degraded the dye molecules entirely.

Application of a novel atmospheric pressure plasma fluidized bed in the powder surface modification

A novel atmospheric pressure plasma fluidized bed (APPFB) with one liquid electrode was designed, and its preliminary discharge characteristics were studied. The glow discharge in the APPFB was generated by applying a low power with helium (He) gas, and the plasma gas temperature was no higher than 320 K when the applied power was lower than 11 W. The plasma optical emission spectrum (OES) of the gas mixture consisting of He and hexamethyldisiloxane (HMDSO) was recorded by a UV-visible monochromator. The calcium carbonate powders were modified by APPFB using HMDSO in the He plasma. The powder surface energy was decreased greatly by coating an organosilicon polymer onto the powder surface. This surface modification process changed the wettability of the powder from super-hydrophilicity to super-hydrophobicity, and the contact angle of water on the modified powders surface was greater than 160°.

Preparation of nanocones for immobilizing DNA probe by a low-temperature plasma plume

Using allylamine monomer, a matrix of nanocones was fabricated by applying a low-temperature plasma plume without any catalysts and template. This nanocone acted as an adhesion layer immobilizing DNA probe for DNA hybridization assay. A simple conceptual model to describe the growth of the nanocones was also developed. The highest density of amino-labeled DNA probe was about 1.6pM∕cm2 confirmed by the dyed oligonucleotide, and each nanocone contained nearly 3×102 amine groups. This strategy provides a robust procedure to immobilize DNA, which is a very useful substrate for fabricating nanobiosensors.

Preparation of Ta(C)N films by pulsed high energy density plasma

The pulsed high energy density plasma (PHEDP) is generated in the working gas due to a high-voltage high-current discharge, within a coaxial gun. In PHEDP surface modification, discharge is applied for preparing the amorphous and nanostructured high-melting materials as thin films deposited on various substrates. In this investigation, Ta(C)N films were deposited using PHEDP on stainless steel. Pure tantalum and graphite were used as the inner and outer electrodes of the PHEDP coaxial gun, respectively. Nitrogen was used as the working gas and also one of the reactants. Preliminary study on the films prepared under different conditions shows that the formation of Ta(C)N is drastically voltage dependent. At lower gun voltage, no Ta(C)N was detected in the films; when the gun voltage reaches or exceeds 3.0 kV, Ta(C)N occurred. The films are composed of densely stacked nanocrystallines with diameter less than 30 nm, and some grains are within 10 nm in diameter.