Guo-Hua Lv

Simultaneous determination of gibberellic acid, indole-3-acetic acid and abscisic acid in wheat extracts by solid-phase extraction and liquid chromatography-electrospray tandem mass spectrometry.

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed for simultaneous determination of three representative phytohormones in plant samples: gibberellic acid (GA(3)), indole-3-acetic acid (IAA) and abscisic acid (ABA). A solid-phase extraction (SPE) pretreatment method was used to concentrate and purify the three phytohormones of different groups from plant samples. The separation was carried out on a C(18) reversed-phase column, using methanol/water containing 0.2% formic acid (50:50, v/v) as the isocratic mobile phase at the flow-rate of 1.0 mL min(-1), and the three phytohormones were eluted within 7 min. A linear ion trap mass spectrometer equipped with electrospray ionization source was operated in negative ion mode. Selective reaction monitoring (SRM) was employed for quantitative measurement. The SRM transitions monitored were as 345-->239, 301 for GA(3), 174-->130 for IAA and 263-->153, 219 for ABA. Good linearities were found within the ranges of 5-200 microg mL(-1) for IAA and 0.005-10 microg mL(-1) for ABA and GA(3). Their detection limits based on a signal-to-noise ratio of three were 0.005 microg mL(-1), 2.2 microg mL(-1) and 0.003 microg mL(-1) for GA(3), IAA and ABA, respectively. Good recoveries from 95.5% to 102.4% for the three phytohormones were obtained. The results demonstrated that the SPE-LC-MS/MS method developed is highly effective for analyzing trace amounts of the three phytohormones in plant samples.

Treatment of enterococcus faecalis bacteria by a helium atmospheric cold plasma brush with oxygen addition

An atmospheric cold plasma brush suitable for large area and low-temperature plasma-based sterilization is designed. Results demonstrate that the He/O2 plasma more effectively kills Enterococcus faecalis than the pure He plasma. In addition, the sterilization efficiency values of the He/O2 plasma depend on the oxygen fraction in Helium gas. The atmospheric cold plasma brush using a proper ratio of He/O2 (2.5%) reaches the optimum sterilization efficiency. After plasma treatment, the cell structure and morphology changes can be observed by the scanning electron microscopy. Optical emission measurements indicate that reactive species such as O and OH play a significant role in the sterilization process.

Deactivation of A549 cancer cells in vitro by a dielectric barrier discharge plasma needle

An inactivation mechanism study on A549 cancer cells by means of a dielectric barrier discharge plasma needle is presented. The neutral red uptake assay provides a quantitative estimation of cell viability after plasma treatment. Experimental results show that the efficiency of argon plasma for the inactivation process is very dependent on power and treatment time. A 27 W power and 120 s treatment time along with 900 standard cubic centimeter per minute Ar flow and a nozzle-to-sample separation of 3 mm are the best parameters of the process. According to the argon emission spectra of the plasma jet and the optical microscope images of the A549 cells after plasma treatment, it is concluded that the reactive species (for example, OH and O) in the argon plasma play a major role in the cell deactivation.

Nanolayer biofilm coated on magnetic nanoparticles by using a dielectric barrier discharge glow plasma fluidized bed for immobilizing an antimicrobial peptide

Using the monomer of acrylic acid and the novel technique of using a dielectric barrier discharge glow plasma fluidized bed (GPFB), a nanolayer biofilm of polyacrylic acid (PAA) was uniformly coated on the surface of magnetic nickel nanoparticles (NPs). Transmission electron microscopy, Fourier transform infrared spectroscopy, and x-ray photoelectron spectroscopy, etc, were used to characterize the modified NPs. The thickness of the biofilm was about 2 nm when the NPs were treated using the GPFB once, and the discharging conditions affected the density of the carboxyl group obviously. The PAA acting as an adhesion layer was used to immobilize the antimicrobial peptide LL-37, to kill the bacteria of Escherichia coli (E. coli), and the results indicated that the modified nickel NPs immobilizing a certain concentration of LL-37 could kill the bacteria effectively.

Characteristics of NOx removal combining dielectric barrier discharge plasma with selective catalytic reduction by C2H5OH

With the assistance of dielectric barrier discharge (DBD) plasma, selective catalytic reduction of NOx by ethanol over Ag/Al2O3 catalysts was studied. Experimental results show that NOx conversion was greatly enhanced due to the presence of DBD plasma at lower temperature. By varying the DBD voltages or power in 13 kHz frequency at different temperatures, NOx conversion was increased to 40.7% from 6.4% at 176 °C, even to 66.8% from 17.3% at 200 °C. NOx conversion could even be improved to 90% at temperature above 255 °C. It was proposed that nonthermal plasma generated by dielectric barrier discharge reactor was very effective for oxidizing NO to NO2 under excess O2 conditions, which possesses high reactivity with C2H5OH to yield CxHyNzO compound. By reacting with CxHyNzO compound and oxygen, NOx is converted to N2 at low temperatures.

Characteristics of (Ti,Ta)N thin films prepared by using pulsed high energy density plasma

(Ti,Ta)N films were prepared by pulsed high energy density plasma (PHEDP) from a coaxial gun in N2 gas. The coaxial gun is composed of a tantalum inner electrode and a titanium outer one. Material characteristics of the (Ti,Ta)N film were investigated by x-ray photoelectron spectroscopy and x-ray diffraction. The microstructure of the film was observed by a scanning electron microscope. The elemental composition and the interface of the film/substrate were analysed using Auger electron spectrometry. Our results suggest that the binary metal nitride film, (Ti,Ta)N, can be prepared by PHEDP. It also shows that dense nanocrystalline (Ti,Ta)N film can be achieved.

Characteristics of NOx Removal Combining Dielectric Barrier Discharge Plasma with Selective Catalytic Reduction by C3H6

Characteristics of NOx removal combining dielectric barrier discharge (DBD) plasma with selective catalytic reduction (SCR) by C3H6 were investigated under the conditions of high NOx concentration and high space velocity at various temperatures. Experiment results show that there were no obvious removal of NOx and NO in the only C3H6-SCR system and only DBD system individually. But the high NOx removal rate was achieved in C3H6-SCR cooperating with DBD plasma system. Especially NOx removal rate can reach up to 88.5% at 150 °C simulating diesel engine exhaust temperature. It can be seen that when discharge comes into being, the catalystic activity was enhanced with discharge strengthened, so that the NOx was almost completely removed. In the course of NOx removal, DBD played an important role in oxidizing NO to NO2 and activating C3H6 and catalysts to reduce NOx.

Deposition of Ti-Al-N Films by Using a Cathodic Vacuum Arc with Pulsed Bias

Ti-Al-N hard films have been prepared by cathodic arc deposition by using an unipolar pulsed bias. In the present study, Ti-Al-N films were deposited on stainless steel and silicon wafers. The deposition rate, micrograph, preferred orientation and composition were systematically investigated by usingx-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), and a scanning electron microscope (SEM). It is shown that substate bias duty cycle and frequency have a great effect on film structure. A simple explanation for the results is also presented.

Characterization of Ti-Al-N Films Deposited by Cathodic Vacuum Arc with Different N2 Partial Pressure

A series of Ti-Al-N films were deposited on silicon wafer and steel substrates by cathodic vacuum arc technique in N2/Ar gas mixtures, using a compound Ti(50):Al(50) target. The chemical composition, crystalline microstructure, film deposition rate and surface morphology of the films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscope (SEM) coupled with an energy dispersive X-ray analysis system (EDX), respectively. The hardness and Young’s modulus, wear performance and corrosion behavior of the Ti-Al-N (multi-phase) films at different N2 partial pressure were analyzed and explained on the basis of microstructure, mechanical properties and wear mechanisms.