Multilayered Cu–Ti deposition on silicon substrates for chemiresistor applications

Abstract

On the perspective to develop CuO–TiO₂ MOS, multilayered Cu and Ti thin layers were alternatively deposited on silicon wafers using 25?keV Ar?+?ion beam sputtering and, subsequently, oxidized by thermal annealing in air at 400?°C for 24?h. The deposited films have variable ratios of the Cu and Ti % at. One of the main goal is to obtain such multilayers avoiding the presence of Cu–Ti–O compounds. The samples were characterized in terms of composition (by RBS and SIMS analyses) and morphology (by AFM and SEM investigations). In particular, SIMS maps allows to observe the spatial distribution and thickness of each phase of the Cu/Ti multilayers, and further to observe Cu diffusion and mixing with Ti, as well as phase separation of CuO and TiO₂ in the samples. The reasons of this effect represent an open issue that has to investigated, in order to improve the MOS fabrication.     

Kinetics and mechanism of oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-cystine by manganese(III) in sulfuric acid medium

The kinetics of oxidation of l-cystine by Mn^III have been studied in sulfuric acid medium at 30 °C. The reaction was followed spectrophotometrically at λmax = 500 nm. The reaction shows first order dependence on both [Mn^III] and [cystine]. It was found that the rate of the reaction decreases with increase of [H⁺] up to a certain point and then remains unchanged. The oxidation product of the reaction was found to be cysteic acid. A plausible mechanism has been proposed to account for the experimental results.     

Synthesis and antimicrobial activity of novel 2‐(aryl)‐3‐[5‐(2‐oxo‐2H‐3‐chromenyl)‐1,3‐oxazol‐2‐yl]‐1,3‐thiazolan‐4‐ones

A series of novel 2‐(aryl)‐3‐[5‐(2‐oxo‐2H‐3‐chromenyl)‐1,3‐oxazol‐2‐yl]‐1,3‐thiazolan‐4‐ones 4a , 4b , 4c , 4e , 4f , 4g , 4h , 4i , 4j have been synthesized and assayed for their antibacterial activity against Gram‐positive bacteria viz. Bacillus subtilis (ATCC 6633), Staphylococcus aureus (ATCC 6538p), Micrococcus luteus (IFC 12708), and Gram‐negative bacteria viz. Proteus vulgaris (ATCC 3851), Salmonella typhimurium (ATCC 14028), Escherichia coli (ATCC 25922), and also antifungal activity against Candida albicans (ATCC 10231), Aspergillus fumigatus (HIC 6094), Trichophyton rubrum (IFO 9185), and Trichophyton mentagrophytes (IFO 40996). Among the screened compounds, 4d , 4e , 4f , 4g , and 4j exhibited potent inhibitory activity compared with the standard drug at the tested concentrations. The results reveal that, the presence of difluorophenyl in 4f and pipernyl ring in 4j at 2‐position of thiazolidine‐4‐one ring show significant inhibitory activity. The other compounds also showed appreciable activity against the test bacteria and fungi and emerged as potential molecules for further development. J. Heterocyclic Chem., 2011.     

Surfactant-Assisted Acid Pretreatment of Sugarcane Tops for Bioethanol Production

Sugarcane tops is one of the largest biomass resources in India and in tropical countries such as Brazil in terms of surplus availability. Conversion of this feedstock to ethanol requires pretreatment to make it more accessible for the enzymes used in saccharification. Though several pretreatment regimens have been developed for addressing biomass recalcitrance, very few seem to be promising as an industrial process. A novel hybrid method involving use of mild acid and surfactant was developed which could effectively remove lignin and improve the sugar yield from sugar cane tops. Operational parameters that affect the pretreatment efficiency (measured as yield of sugars) were studied and optimized. Changes in structural properties of the biomass were studied in relation to the pretreatment process using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier Transform Infrared (FTIR) analysis, and the changes in chemical composition was also monitored. The biomass pretreated with the optimized novel method could yield 0.798?g of reducing sugars per gram of pretreated biomass upon enzymatic hydrolysis.     

Synthesis,biological evaluation,and molecular docking studies of novel pyrazole,pyrazoline-clubbed pyridine as potential antimicrobial agents

We have prepared 15 hybrid pyrazole, pyrazoline-clubbed pyridine–containing compounds (5a-o) and tested for their antibacterial and antifungal activities for the development of potential antimicrobial agents. The structures of this novel series were characterized by various spectral techniques like IR, ¹H NMR, ¹³C NMR, LC–MS, and elemental analysis. The synthesized compounds 5d, 5e, 5i, 5k, 5m, and 5o exhibited significant antimicrobial activity in the comparison of standard drugs. Molecular docking studies that have been carried out to emphasize the binding orientations of these molecules were in good compliance with crystal structure interactions. The predicted drug-likeness (ADME) properties were found to be in the acceptable range.     

Scattering of light by a periodic structure in the presence of randomness IV. Limit of detection by curve fitting

In the context of scattering of light, we determine the extent of randomness within which a hidden periodic part can still be detected. The detection is carried out using a technique called the extended matched filtering, first introduced by us in this context. The earlier prediction, before our technique was introduced, had placed the limit of detection, by intensity measurements alone, at (r ₀/Λ) ∼ 0.33, where r₀ is the coherence length of light for scattering by the rough part of the surface and Λ is the wavelength of the periodic part of the surface. In our earlier works we have shown that by intensity measurements alone, the limit of detection can be taken to a much lower value of (r ₀/Λ), when the extended matched filtering method is employed. In this paper we follow the extended matched filtering method, and try to reach the lowest possible value of detection in (r ₀/Λ) by fitting the data to a polynomial. It is concluded by our numerical work that the lowest possible limit for detection from intensity measurements alone is (r ₀/Λ) = 0.11.     

Some features of the perturbing effects of gravity near the gas liquid critical point

The effect of gravity on various thermodynamic properties near the gas-liquid critical point has been calculated. Using a simple equation satisfying scaling requirements, an analytic expression for density profile is obtained, using which the effect on different thermodynamic properties can be easily calculated.     

Measurement of diffusion coefficient of transparent liquid solutions using Michelson interferometer

The study of diffusivity is important for the design of chemical equipment and its knowledge is needed for mass transfer studies and is the most fundamental property of any chemical system in which the chemical engineers are interested. Here, we report a new interferometric technique to determine the diffusion coefficient of transparent liquid solutions using Michelson interferometer geometry. The experimental cell containing the diffusing solution was kept in one of the arms of Michelson Interferometer. The liquids of differing concentrations were introduced in the cell. Two separate circular interference fringe systems were formed due to the two solutions and they were recorded on a PC using a CCD camera. The time variation of these interferograms yields the diffusion coefficient. The obtained diffusivity values matched very well with the existing experimental results. Detailed theoretical and experimental analysis is given in the paper.