Mahendra D. Shirsat

Polyaniline nanowires-gold nanoparticles hybrid network based chemiresistive hydrogen sulfide sensor

We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for hydrogen sulfide detection and quantification using polyaniline nanowires-gold nanoparticles hybrid network. The sensor was fabricated by facile electrochemical technique. Initially, polyaniline nanowires with a diameter of 250–320 nm bridging the gap between a pair of microfabricated gold electrodes were synthesized using templateless electrochemical polymerization using a two step galvanostatic technique. Polyaniline nanowires were then electrochemically functionalized with gold nanoparticles using cyclic voltammetry technique. These chemiresistive sensors show an excellent limit of detection (0.1 ppb), wide dynamic range (0.1–100 ppb), and very good selectivity and reproducibility.

Study on optical properties of l-valine doped ADP crystal

Single crystal of l-valine doped ammonium dihydrogen phosphate has been grown by slow evaporation method at room temperature. The crystalline nature of the grown crystal was confirmed using powder X-ray diffraction technique. The different functional groups of the grown crystal were identified using Fourier transform infrared analysis. The UV-visible studies were employed to examine the high optical transparency and influential optical constants for tailoring materials suitability for optoelectronics applications. The cutoff wavelength of the title crystal was found to be 280nm with wide optical band gap of 4.7eV. The dielectric measurements were carried to determine the dielectric constant and dielectric loss at room temperature. The grown crystal has been characterized by thermogravimetric analysis. The second harmonic generation efficiency of the grown crystal was determined by the classical Kurtz powder technique and it is found to be 1.92 times that of potassium dihydrogen phosphate. The grown crystal was identified as third order nonlinear optical material employing Z-scan technique using He-Ne laser operating at 632.8nm.

Synthesis and Characterization of Ppy-PVS, Ppy-pTS, and Ppy-DBS Composite Films

Composite films of polypyrrole-poly(vinyl sulphonic acid) (Ppy-PVS), polypyrrole-p-toluene sulphonic acid (Ppy-pTS) and polypyrrole-dodecylbenzene sulphonic acid (Ppy-DBS) were synthesized on ITO coated glass, using electrochemical polymerization. The synthesized films were characterized using electrochemical technique, electrical conductivity, UV-Vis spectroscopy, FTIR spectra, and scanning electron microscopy (SEM). This study reveals that Ppy-PVS composite films provide a polymer matrix with very good mechanical and environmental stability, uniform surface morphology, and higher conductivity, which are suitable for the immobilization of biocomponent.

Controlled functionalization of single-walled carbon nanotubes for enhanced ammonia sensing: a comparative study

Electrochemically controllable functionalization of single-walled carbon nanotubes (SWNTs) with poly(N-methyl pyrrole) (P[NMP]) is demonstrated for room temperature gas sensing applications. Comparative investigations reveal that the loading content of the functionalization entity has prominent effects on the sensing characteristics of SWNTs. The optimized sensing backbone (P[NMP]-functionalized SWNTs with 5??C deposited charge) exhibited a lower detection limit of 10?ppb and excellent linearity for a detection window of 10?ppb?01?ppm concentration of NH3. The typical response and recovery time of the optimized sensor is on the order of minutes. Finally, a performance comparison of the P[NMP]-functionalized SWNT sensing backbones with the pristine P[NMP] nanowire sensor ensured the well-defined role of SWNTs in the functionalized structure. The proposed sensing mechanism suggests that the synthesis parameters can be manoeuvered for the highest operational efficiency of the sensors.

Doping effect of carboxylic acids on optical, electrical, mechanical and thermal traits of KDP crystal

Abstract Single crystals of maleic acid (MA)- and oxalic acid (OA)-doped potassium dihydrogen phosphate (KDP) materials have been grown by slow evaporation solution technique. The structural parameters of the grown crystals have been determined using the single crystal X-ray diffraction technique. Fourier transform infrared analysis has been done to identify the functional groups of grown crystals. The modifications in optical transmittance, optical band gap and different optical constants of KDP crystal due to addition of MA and OA have been investigated by means of UV–Visible spectral analysis. The Vicker’s microhardness studies have been carried out to examine the mechanical behaviour of pure and doped KDP crystals. The influence of dopants on thermal stability of KDP crystal has been investigated using the thermogravimetric and differential thermal analysis. The dielectric constant, dielectric loss, ac resistivity and ac conductivity of pure and doped KDP crystals were evaluated under dielectric studies.

Optical, thermal and electrical properties of pure and doped bis-thiourea cadmium formate (BTCF) crystal

A glycine doped bis-thiourea cadmium formate (BTCF) crystal has been grown by a slow solution evaporation technique. The shifts in vibrational frequencies of different functional groups of BTCF were identified by Fourier transform infrared (FT-IR) spectral analysis. UV-visible studies were employed to assess the optical transparency of pure and doped BTCF crystals. The optical band gap of doped BTCF is found to be 5.16 eV. The optical constants, refractive index, reflectance, and optical conductivity have been evaluated, using the transmission data. The dielectric characteristics of pure and doped BTCF were investigated by employing dielectric studies. The decomposition temperature of pure and doped BTCF crystals was determined by using thermogravimetric analysis. The encouraging third-order nonlinear optical properties of pure and doped BTCF crystals were examined by employing the Z-scan technique at 632.8 nm.

Synthesis of H2SO4 doped polyaniline film by potentiometric method

H2SO4 doped polyaniline films were synthesized in aqueous acidic media. The polyaniline film deposited on platinum electrode exhibits highest conductivity. The conductivity of each H2SO4 doped polyaniline sample was determined by the four-probe technique. The current-voltage curve exhibits that polyaniline sample has an ohmic behaviour. Experiments were conducted to establish the conductivity of the sample from room temperature to 110°C. The current was set constant. It has been observed that at lower current as well as higher current conductivity of the polyaniline sample is due to the electrons transferred to the conduction band. It is observed that the concentration ratio of 0.2:1 of aniline and H2SO4 for synthesis of PANI film on platinum electrode shows good conductivity.

Evaluate the effect of L-valine on linear–nonlinear optical and electrical properties of BTCA crystal to identify photonic device applications

In this study, pure and l-valine (LV)-doped bis-thiourea cadmium acetate (BTCA) crystals have been grown by slow solution evaporation technique. For the first time, LV has been used as a dopant to tune the optical (linear and third-order non-linear optical) and electrical properties of BTCA crystal which are vital for various integrated optic device applications. The UV-visible spectral analysis has been performed in the range of 200–900 nm to determine the optical transparency of grown crystals. The Z-scan (open and closed apertures) studies were undertaken at 632.8 nm to ascertain the nature of third-order non-linearity in grown crystals. The third-order non-linear optical parameters such as non-linear refraction (n2), absorption coefficient (β) and susceptibility (χ3) of grown crystals have been calculated. The susceptibility (χ3) of pure and LV-doped BTCA crystal is found to be 2.58 × 10−4 esu and 3.34 × 10−4 esu, respectively. The electrical studies have been carried out to analyse the dielectric constant, dielectric loss, ac resistivity and ac conductivity of pure and LV-doped BTCA crystals.

Investigation on structural, UV-visible, SHG efficiency, dielectric, mechanical and thermal behavior of L-cystine doped zinc thiourea sulphate crystal for NLO device applications

In the present study, pure and L-cystine (LC) doped zinc thiourea sulphate (ZTS) crystals have been grown by slow evaporation solution technique at ambient temperature. The powder X-ray diffraction (XRD) analysis has been carried out to identify the shifts in peak positions and structural parameters of grown crystals. The incorporation of LC in ZTS crystal has been qualitatively analyzed by means of Fourier transform infrared (FTIR) spectroscopic study. In UV-visible studies, the influence of LC on optical transparency, bandgap and various optical constants of ZTS crystal have been investigated to explore various optical applications. The thermal stability of LC doped ZTS crystal has been determined by means of differential scanning calorimetry (DSC) analysis. The hardness behavior and hardness number of grown crystals have been comparatively evaluated by employing the Vicker’s microhardness test. The dielectric study of pure and LC doped ZTS crystal has been carried out at different temperature. In Kurtz–Perry powder technique, the second harmonic generation (SHG) efficiency of LC doped ZTS crystal is found to be 1.16 times that of ZTS crystal.

Growth, structural UV–visible, SHG, mechanical and dielectric studies of bis-thiourea zinc chloride doped KDP crystal for NLO device applications

Optically transparent 11 × 10 × 4 mm3 bis-thiourea zinc chloride (BTZC) doped potassium dihydrogen phosphate (KDP) crystal has been grown by slow evaporation solution technique. The cell parameters of the grown crystal have been determined by single crystal X-ray diffraction analysis. The incorporation of BTZC in KDP crystal has been qualitatively analysed by FT-IR spectral analysis. The optical transparency and vital optical constants of BTZC doped KDP single crystals have been evaluated in the range of 200–900 nm. The mechanical behaviour of pure and doped KDP crystals has been investigated under the Vickers microhardness studies. The dielectric parameters of grown crystal have been investigated within the frequency range of 10–100 KHz. In Kurtz–Perry powder test, the second harmonic generation (SHG) efficiency of BTZC doped KDP crystal is found to be 1.65 times that of KDP material.