Ranjan K. Pati

Electrodeposition of Si from an Ionic Liquid Bath at Room Temperature in the Presence of Water

The electrochemical deposition of Si has been carried out in an ionic liquid medium in the presence of water in a limited dry nitrogen environment on highly oriented pyrolytic graphite (HOPG) at room temperature. It has been found that the presence of water in ionic liquids does not affect the available effective potential window to a large extent. Silicon has been successfully deposited electrochemically in the overpotential regime in two different ionic liquids, namely, BMImTf2N and BMImPF6, in the presence of water. Although a Si thin film has been obtained from BMImTf2N; only distinguished Si crystals protected in ionic liquid droplets have been observed from BMImPF6. The most important observation of the present investigation is that the Si precursor, SiCl4, instead of undergoing hydrolysis, even in the presence of water, coexisted with ionic liquids, and elemental Si has been successfully electrodeposited.

Gastrointestinal tract mechanism of nitrite capture modeled on the self assembled monolayer of thioproline for electrochemical nitrite determination

Gastrointestinal (GI) tract has a unique mechanism for nitric oxide (NO) capture in the form of N-nitrosamines. N-Nitrosamines are formed by the reaction between thioproline (THP) and NO under the acidic conditions prevalent in the stomach. The nitrosamines thus formed are excreted in the urine and act as an important biomarker for human NO concentrations. Exploiting the GI tract mechanism of nitrosamine formation, we prepared the self-assembled monolayers (SAMs) of THP on gold wafers and gold nanoparticles (GNPs). The SAMs were characterized by contact angle measurements, ATR-FTIR, FE-SEM with EDS, XPS, DLS and TEM. The SAM-covered gold surfaces were used as a mimetic model of the GI tract to capture nitrite (NO2−) ions for their determination using electrochemical and colorimetric methods. The XPS and ATR-FTIR were used to determine the mechanism of NO2− binding to THP, supported by electrochemical measurements. The rapid NO2− capture by THP SAM-coated gold surfaces results in the electrovalent binding of NO2− with THP within fractions of seconds. Since THP is known to react with NO2− at about a 1000 times faster rate than the reaction with known reactants, the added advantage of the designed THP-SAM-coated gold surface model is a rapid reaction kinetics which minimize the self-decomposition of NO. The electrochemical detection provides an excellent detection limit with good sensitivity. UV-visible spectroscopy, though it efficiently detects the traces of NO2−, is unable to give the competitive limit of detection and sensitivity obtained from electrochemical detection. Thus, the THP-SAM-coated gold model can be considered as a GI tract model capturing the NO2− using similar reactants and conditions prevalent to those in GI tract. The developed model can be employed for routine screening and the determination of NO2− or NO in complex samples or biological matrices without any interference from the matrix as most common impurities/species do not react with THP-SAMs under the employed conditions.

Effect of annealing temperature on the PEC performance of electrodeposited copper oxides

In this work, we have deposited Cu2O film on fluorine doped tin oxide (FTO) substrate by electrodeposition. Pure CuO phase has been obtained by annealing the electrodeposited Cu2O film at optimized temperature (500°C) for two hours in air. Copper(I) oxide films showed good photo response with a current density of 0.54mA/cm2 at 0 V vs RHE. It is evident from UV-Visible spectroscopic analysis that the bandgap of Cu(I) and Cu(II) oxides differs from each other resulting in significant change in photo current for these two phases, observed in the PEC study. However CuO film showed better stability as compared to Cu2O film.In this work, we have deposited Cu2O film on fluorine doped tin oxide (FTO) substrate by electrodeposition. Pure CuO phase has been obtained by annealing the electrodeposited Cu2O film at optimized temperature (500°C) for two hours in air. Copper(I) oxide films showed good photo response with a current density of 0.54mA/cm2 at 0 V vs RHE. It is evident from UV-Visible spectroscopic analysis that the bandgap of Cu(I) and Cu(II) oxides differs from each other resulting in significant change in photo current for these two phases, observed in the PEC study. However CuO film showed better stability as compared to Cu2O film.

Determining the confined optical length of high index vertical Si nanoforest arrays for photonic applications

The structural and the optical properties of different Si nanostructures have been compared. Detailed optical properties of Si nanowires arrays of different optical lengths, fabricated by facile electroless etching technique, have been reported. The theoretical calculation of exponential sine profile at constant λ = 600 nm shows a better explanation in terms of gradient index with optical length for vertical nanowires. The observations signify the possibility of strong light trapping due to an exponential gradient towards the high index along the nanowires and the existence of dense subwavelength features. The optical admittance (Ƶ) shows a strong impact on optical distance (Z) for Z < H, owing to the electromagnetic wave interaction with the nanowires that perceive a different Ƶ at the oblique angle of incidence (AOI). In addition, the experimental reflectance data and the theoretical model for transverse electric and transverse magnetic modes predict that an optical length of 5 μm can exhibit a very low...

Effect of annealing atmosphere on microstructure, optical and electronic properties of spray-pyrolysed In-doped Zn(O,S) thin films

Spray-pyrolysed zinc oxy-sulphide Zn(O,S) has been doped with varying concentrations of indium (In) to improve its electrical and optical properties for possible application as buffer layer in thin film solar cells. The In-doping in Zn(O,S) is found to change the electron carrier concentration from

Optimization of photoelectrochemical performance in chemical bath deposited nanostructured CuO

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Effective Photocurrent Enhancement in Nanostructured CuO by Organic Dye Sensitization: Studies on Charge Transfer Kinetics

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