Investigation on the effect of RF air plasma and neem leaf extract treatment on the surface modification and antimicrobial activity of cotton fabric

A thorough investigation on the antimicrobial activity of RF air plasma and azadirachtin (neem leaf extract) treated cotton fabric has been dealt with in this paper. The cotton fabric was given a RF air plasma treatment to improve its hydrophilicity. The process parameters such as electrode gap, time of exposure and RF power have been varied to study their effect in improving the hydrophilicity of the cotton fabric and they were optimized based on the static immersion test results. The neem leaf extract (azadirachtin) was applied on fabric samples to impart antimicrobial activity. The antimicrobial efficacy of the samples have been analysed and compared with the efficacy of the cotton fabric treated with the antimicrobial finish alone. The investigation reveals that the RF air plasma has modified the surface of the fabric, which in turn increased the antimicrobial activity of the fabric when treated with azadirachtin. The surface modification due to RF air plasma treatment has been analysed by comparing the FTIR spectra of the untreated and plasma treated samples. The molecular interaction between the fabric, azadirachtin and citric acid which was used as a cross linking agent to increase the durability of the antimicrobial finish has also been analysed using FTIR spectra.     

PDT光敏剂HA在不同液相体系下的光谱特性研究

为了对候选光敏剂竹红菌甲素(HA)进行改性并保持其优异的敏化特性,对HA的光谱特性和激发态性质作了进一步的指认。系统研究了HA在不同液相体系下的吸收和荧光光谱,对指认HA的光谱和电子跃迁的机制提出了新的依据,结果表明,吸收带I产生于π-π*跃迁,吸收带Ⅱ和Ⅲ产生于P-π共轭所导致的L→aπ跃迁的电子振动结构;荧光发射带I和Ⅱ是产生于同一跃迁机制S1(L,aπ)→S0的正常荧光的振动结构。     

A theoretical study of the oxygen K-edge near-edge X-ray absorption ne structure of N2O/Ir(110)

A multiple-scattering cluster method is employed to calculate the oxygen K-edge near-edge X-ray absorption fine structure of N₂O/Ir(110) and its monolayer. Two peaks and one weak resonance appear in both cases. The selfconsistent field DV-X calculations of the peaks and resonance show that the physical origin of the pre-edge peak x is different from those of the main peak 1 and the other weak resonance σ₁. This setup is intrinsic to the N₂O monolayer, owing to the interaction between the neighbouring molecular chains in the monolayer and partly to the adsorbed atomic oxygen, according to both the theoretical and experimental data.     

A study of the interaction between perylene and the TiO2(1 1 0)-(1 × 1) surface-based on XPS, UPS and NEXAFS measurements

The interaction between a semi-large aromatic hydrocarbon compound (perylene) and the TiO₂(1 1 0)-(1 × 1) surface under ultra high vacuum conditions has been probed by X-ray photoemission spectroscopy (XPS), ultraviolet photoemission spectroscopy (UPS) and near-edge X-ray absorption fine structure (NEXAFS) methods. UPS measurements of the adsorbate system have been compared with an experimental UPS spectrum of perylene in the gas phase and a calculated spectrum obtained by means of density functional theory (DFT) methods. NEXAFS results of perylene molecules adsorbed on TiO₂(1 1 0)-(1 × 1) were compared with data from an α-phase perylene single crystal. A novel analysis of the valence data has been employed to show that no strong chemical interaction takes place between perylene and the TiO₂(1 1 0)-(1 × 1) surface. Furthermore, angle-dependent NEXAFS measurements and the growth curve results suggest that the perylene molecules are oriented flat down onto the TiO₂ substrate due to weak van der Waals interactions.     

A comprehensive overview on the structure and comparison of magnetic properties of nanocrystalline synthesized by a thermal treatment method

This study reports the simple synthesis of MFe₂O₄ (where M=Zn, Mn and Co) nanostructures by a thermal treatment method, followed by calcination at various temperatures from 723 to 873 K. Poly(vinyl pyrrolidon) (PVP) was used as a capping agent to stabilize the particles and prevent them from agglomeration. The pyrolytic behaviors of the polymeric precursor were analyzed by use of simultaneous thermo-gravimetry analyses (TGA) and derivative thermo-gravimetry (DTG) analyses. The characterization studies were conducted by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Fourier transform infrared spectroscopy (FT-IR) confirmed the presence of metal oxide bands for all the calcined samples. Magnetic properties were demonstrated by a vibrating sample magnetometer (VSM), which displayed that the calcined samples exhibited different types of magnetic behavior. The present study also substantiated that magnetic properties of ferrite nanoparticles prepared by the thermal treatment method, from viewing microstructures of them, can be explained as the results of the two important factors: cation distribution and impurity phase of α-Fe₂O₃. These two factors are subcategory of the preparation method which is related to macrostructure of ferrite. Electron paramagnetic resonance (EPR) spectroscopy showed the existence of unpaired electrons ZnFe₂O₄ and MnFe₂O₄ nanoparticles while it did not exhibit resonance signal for CoFe₂O₄ nanoparticles.     

Surface chemistry of NO and NO2 on the Pt(1 1 0)-(1 × 2) surface: A comparative study

The surface chemistry of NO and NO₂ on clean and oxygen-precovered Pt(1 1 0)-(1 × 2) surfaces were investigated by means of high resolution electron energy loss spectroscopy (HREELS), X-ray photoelectron spectroscopy (XPS) and thermal desorption spectroscopy (TDS). At room temperature, NO molecularly adsorbs on Pt(1 1 0), forming linear NO(a) and bridged NO(a). Coverage-dependent repulsive interactions within NO(a) drive the reversible transformation between linear and bridged NO(a). Some NO(a) decomposes upon heating, producing both N₂ and N₂O. For NO adsorption on the oxygen-precovered surface, repulsive interactions exist between precovered oxygen adatoms and NO(a), resulting in more NO(a) desorbing from the surface in the form of linear NO(a). Bridged NO(a) experiences stronger repulsive interactions with precovered oxygen than linear NO(a). The desorption activation energy of bridged NO(a) from oxygen-precovered Pt(1 1 0) is lower than that from clean Pt(1 1 0), but the desorption activation energy of linear NO(a) is not affected by the precovered oxygen. NO₂ decomposes on Pt(1 1 0)-(1 × 2) surface at room temperature. The resulted NO(a) (both linear NO(a) and bridged NO(a)) and O(a) repulsively interact each other. Comparing with NO/Pt(1 1 0), more NO(a) desorbs from NO₂/Pt(1 1 0) as linear NO(a), and both linear NO(a) and bridged NO(a) exhibit lower desorption activation energies. The reaction pathways of NO(a) on Pt(1 1 0), desorption or decomposition, are affected by their repulsive interactions with coexisting oxygen adatoms.     

Adsorption and reaction of methanethiol on the Ru(0 0 0 1)-p(2 × 2)O surface: A TPD and XPS study

Methanethiol adsorbed on Ru(0 0 0 1)-p(2 × 2)O has been studied by TPD and XPS. The dissociation of methanethiol to methylthiolate and hydrogen at 90 K is evidenced by the observation of hydroxyl and water. The saturation coverage of methylthiolate is ∼0.15 ML, measured by both XPS and TPD. A detailed analysis suggests that only the hcp-hollow sites have been occupied. Upon annealing the surface, water and hydroxyl desorb from the surface at ∼210 K. Methylthiolate decomposes to methyl radical and atomic sulphur via C-S cleavage between 350 and 450 K. Some methyl radicals (0.05 ML) have been transferred to Ru atoms before they decompose to carbon and hydrogen. The rest of methyl radicals desorb as gaseous phase. No evidence for the transfer of methyl radical to surface oxygen has been found.     

A study on the phase transformation behaviour of Cu-20wt.Sn alloy produced using powder metallurgy method: Experimental and molecular dynamics modelling

In this study, Cu-20wt.Sn alloy was produced by powder metallurgy (PM) method by using high purity element powders. The phases in the microstructure of the produced alloy were determined by XRD study. The phase transformation behaviour of the alloy was investigated by DSC and modelling method. Moreover, the Cu-20wt.Sn alloy system was modelled with molecular dynamics (MD) simulation based on modified Embedded Atom Method (MEAM). The radial distribution function (RDF) was calculated to determine the structural properties of system during the phase transformations. The experimental results showed that the transformation ($\alpha +\delta$) → ($\alpha +\gamma$) occur at temperature above 500°C. The simulation results showed that the phase transformation $\alpha +\delta \to \alpha +\gamma$ occurs at 550°C temperature. Our simulation results are in reasonable agreement with the experimental data.