Indian Institute of Technology Kharagpur

About: Indian Institute of Technology Kharagpur is a education organization based out in Kharagpur, India. It is known for research contribution in the topics: Computer science & Dielectric. The organization has 16887 authors who have published 38658 publications receiving 714526 citations.

Multifunctional Au-ZnO Plasmonic Nanostructures for Enhanced UV Photodetector and Room Temperature NO Sensing Devices

Abstract: In this study we report the enhancement of UV photodetection and wavelength tunable light induced NO gas sensing at room temperature using Au-ZnO nanocomposites synthesized by a simple photochemical process Plasmonic Au-ZnO nanostructures with a size less than the incident wavelength have been found to exhibit a localized surface plasmon resonance (LSPR) that leads to a strong absorption, scattering and local field enhancement The photoresponse of Au-ZnO nanocomposite can be effectively enhanced by 80 times at 335 nm over control ZnO We also demonstrated Au-ZnO nanocomposite's application to wavelength tunable gas sensor operating at room temperature The sensing response of Au-ZnO nancomposite is enhanced both in UV and visible region, as compared to control ZnO The sensitivity is observed to be higher in the visible region due to the LSPR effect of Au NPs The selectivity is found to be higher for NO gas over CO and some other volatile organic compounds (VOCs), with a minimum detection limit of 01 ppb for Au-ZnO sensor at 335 nm

Impedance spectroscopy of multiferroic Pb Zr x Ti 1 − x O 3 ∕ Co Fe 2 O 4 layered thin films

Abstract: The electrical properties of ferroelectric $\mathrm{Pb}(\mathrm{Zr},\mathrm{Ti}){\mathrm{O}}_{3}$ (PZT) and ferromagnetic $\mathrm{Co}{\mathrm{Fe}}_{2}{\mathrm{O}}_{4}$ (CFO) thin film multilayers (MLs) fabricated by pulsed laser deposition technique has been studied by impedance and modulus spectroscopy. The effect of various PZT/CFO configurations having three, five, and nine layers has been systematically investigated. The transmission electron microscopy images revealed that the ML structures were at least partially diffused near the interface. Diffraction patterns indicate clear PZT and CFO crystal structures in the interior and at the interface of the ML structure. Room temperature micro-Raman spectra indicate separate PZT and CFO phases in ML structure without any impurity phase. We studied frequency and temperature dependencies of impedance, electric modulus, and ac conductivity of ML thin films in the ranges of $100\phantom{\rule{0.3em}{0ex}}\mathrm{Hz}\char21{}1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz}$ and $200\char21{}650\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, respectively. We observed two distinct electrical responses in all the investigated ML films at low temperature $(l400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ and at elevated temperature $(g400\phantom{\rule{0.3em}{0ex}}\mathrm{K})$. We attributed these contributions to the grain effects at low temperature and grain boundary effects at high temperature. We explained this electrical behavior by Maxwell-Wagner-type contributions arising from the interfacial charge at the interface of the ML structure. Master modulus spectra indicate that the magnitude of grain boundary compared to grain becomes more prominent with the increase in the number of layer. The frequency dependent conductivity results well fitted with the double power law, $\ensuremath{\sigma}(\ensuremath{\omega})=\ensuremath{\sigma}(0)+{A}_{1}{\ensuremath{\omega}}^{{n}_{1}}+{A}_{2}{\ensuremath{\omega}}^{{n}_{2}}$, and the results showed evidence of three types of conduction process at elevated temperature: (i) low frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{kHz})$ conductivity is due to long-range ordering (frequency independent), (ii) midfrequency conductivity $(l10\phantom{\rule{0.3em}{0ex}}\mathrm{kHz})$ may be due to the short-range hopping, and (iii) high frequency $(l1\phantom{\rule{0.3em}{0ex}}\mathrm{MHz})$ conduction is due to the localized relaxation hopping mechanism.

Solvent and Ligand Effects on the Localized Surface Plasmon Resonance (LSPR) of Gold Colloids

Abstract: Cetylpyridinium chloride(CPC)-stabilized gold organosol in toluene has been prepared by using a two-phase (water−toluene) extraction of AuCl4- followed by its reduction with sodium borohydride in the presence of the surfactant, CPC. The surfactant-stabilized gold nanoparticles were exploited to examine their optical properties when exposed to various solvent systems and ligands by measuring the changes in the localized surface plasmon resonance (LSPR) spectrum. It was seen that the position of the surface plasmon band of metal nanoparticles is greatly influenced by the solvents and the ligands under consideration. The surface plasmon absorption maxima modulates/varies between 520 and 550 nm for gold nanoparticles, depending on the refractive index of the solvent. The significant discovery presented here is that λmax of the LSPR shifts to the blue by 3 nm for the increase of one carbon atom in the alcohol chain. Cationic and anionic surfactants of different chain lengths induce changes in the optical prope...