Department of Physics

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

Physics

We report the demonstration of high-performance long-wavelength infrared (LWIR) nBn photodetectors based on InAs/InAs1−xSbx type-II superlattices. A new saw-tooth superlattice design was used to implement the electron barrier of the photodetectors. The device exhibited a cut-off wavelength of ∼10 μm at 77 K. The photodetector exhibited a peak responsivity of 2.65 A/W, corresponding to a quantum efficiency of 43%. With an R × A of 664 Ω·cm2 and a dark current density of 8 × 10−5 A/cm2, under −80 mV bias voltage at 77 K, the photodetector exhibited a specific detectivity of 4.72 × 1011 cm·√Hz/W and a background-limited operating temperature of 110 K. © 2017 Author(s).

World University root node

School of Advanced Sciences

Chennai Campus

Fulltext

APL Materials

Background-limited long wavelength infrared InAs/InAs1−xSbx type-II superlattice-based photodetectors operating at 110 K

The original version of this article unfortunately contained a mistake. The captions to Figs. 3 and 4 were interchanged. The correct versions are given below. (Figure Presented.) © 2017, Springer-Verlag Berlin Heidelberg.

Applied Physics A: Materials Science and Processing

Erratum to: Enhancement of device performance by using quaternary capping over ternary capping in strain-coupled InAs/GaAs quantum dot infrared photodetectors (Applied Physics A, (2015), 118, 2, (511-517), 10.1007/s00339-014-8854-9)

We report on the influence of hydrogen incorporation on the conductivity of phosphorous (P) doped ZnO thin films grown by using radio-frequency (RF) magnetron sputtering.

RSC Advances

Hydrogen incorporation effect in phosphorus-doped p-type ZnO thin films grown by radio-frequency magnetron sputtering

4-(aminocarbonyl)pyridine 4-(aminocarbonyl)pyridinium hydrogen L-malate [(4ACP)(4ACP).(LM)] a new organic nonlinear optical (NLO) crystal was grown by the slow evaporation method. Single crystal X-ray diffraction analysis revealed that the [(4ACP)(4ACP).(LM)] crystal belongs to monoclinic crystal system, space group P21/n, with a three dimensional network. Thermogravimetry (TG) and differential thermal (DT) analyses showed that [(4ACP)(4ACP).(LM)] is thermally stable up to 165 °C. The optical transmittance window and the lower cut-off wavelength of [(4ACP)(4ACP).(LM)] were found out by UV–vis–NIR spectral study. The molecular structure of [(4ACP)(4ACP).(LM)] was further confirmed by FTIR spectral studies. The relative dielectric permittivity and dielectric loss were determined as function of frequency and temperature. The third order nonlinear optical property of [(4ACP)(4ACP).(LM)] was studied by the Z-scan technique using a 532 nm diode pumped CW Nd:YAG laser. Nonlinear refractive index, nonlinear absorption coefficient and third order nonlinear susceptibility of the grown crystal were found to be 7.38×10−8 cm2/W, 0.08×10−4 cm/W and 5.36×10−6 esu, respectively. The laser damage threshold value is found to be 1.75 GW/cm2 © 2016 Elsevier Inc.

Computer Science

School of Computer Science and Engineering

Journal of Solid State Chemistry

Synthesis, growth, structural and optical studies of a new organic three dimensional framework: 4-(aminocarbonyl)pyridine 4-(aminocarbonyl)pyridinium hydrogen L-malate

We had synthesized a new compound YbFe2As2 using heating technique followed by the furnace cooling process. YbFe2As2 had been synthesized in polycrystalline form. The presence of adsorbed oxygen was confirmed on the surfaces of grown YbFe2As2 by EDAX analysis. Hence the sample had been named as YbFe2As2:O2. This new compound YbFe2As2:O2 had shown paramagnetic behaviour when magnetization (M) versus temperature (T) was measured using superconducting quantum interference device (SQUID) at constant magnetic field (H = 795.77 × 103 A m-1). A sharp slope change around 140 K was noticed during magnetization (M) versus temperature (T) at H = (795.77 × 101 A m-1) which is the SDW transition temperature for the well-studied parent compound BaFe2As2. Result of M versus H measurements for YbFe2As2:O2 at 2 and 200 K had revealed that the saturation point could not been achieved at H = (557.04 × 104 A m-1). The detailed magnetic studies on YbFe2As2:O2 exhibited that the co-existence of both strong antiferromagnetic as well as a weak ferromagnetic behaviour. Temperature versus resistivity measurement showed metallic behaviour along with a transition at around 13 K. Influence of antiferromagnetic spin fluctuation in the normal state transport property of YbFe2As2:O2 had been found. © 2017 IOP Publishing Ltd.

Materials Research Express

Synthesis and physical properties of oxygen adsorbed YbFe2As2

The present work describes the successful synthesize of spinel magnetic ferrite Mn1-xNixFe2O4 (x = 0.0, 0.1, 0.2, 0.3, 0.4 &amp; 0.5) nanoparticles via a simple microwave combustion method which was then evaluated for its photocatalytic activity in the degradation of indigo carmine (IC) synthetic dye, a major water pollutant. Our results reveal that the synthesized of Ni2+ doped MnFe2O4 nanoparticles possess well-crystalline pure cubic spinel phase, exhibit excellent optical and magnetic properties. Further, the photocatalytic performance of the synthesized nanoparticles at different concentration ratios of Ni2+ ions was monitored by photocatalytic degradation of indigo carmine synthetic dye under UV (λ = 365 nm) light irradiation. In order to get maximum photocatalytic degradation (PCD) efficiency, we have optimized various parameters, which include catalyst dosage, initial dye concentration, pH and Ni2+ dopant content. It was found that the reaction was facilitated with optimum catalyst dose of 50 mg/100 mL, high dye concentrations of 150 mg/L and acidic pH and among all the synthesized samples, Mn0·5Ni0.5Fe2O4 exhibit superior performance of photocatalytic activity on the degradation of indigo carmine synthetic dye. These results highlighted the potential use of effective, low-cost and easily available photocatalysts for the promotion of wastewater treatment and environmental remediation. In addition, the antibacterial activity of spinel magnetic Mn1–xNixFe2O4 nanoparticles against two Gram positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram negative bacteria (Pseudomonas aeruginosa and Escherichia coli) was also examined. Our antibacterial activity results are comparable with the results obtained using the antibiotic, streptomycin. © 2016 Elsevier B.V.

Journal of Photochemistry and Photobiology B: Biology

Studies on the efficient dual performance of Mn1–xNixFe2O4 spinel nanoparticles in photodegradation and antibacterial activity

Green protocols for the synthesis of nickel oxide nanoparticles using Moringa oleifera plant extract has been reported in the present study as they are cost effective and ecofriendly, moreover this paper records that the nickel oxide (NiO) nanoparticles prepared from green method shows better cytotoxicity and antibacterial activity. The NiO nanoparticles were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), High resolution transmission electron microscopy (HRTEM), Energy dispersive X-ray analysis (EDX), and Photoluminescence spectroscopy (PL). The formation of a pure nickel oxide phase was confirmed by XRD and FTIR. The synthesized NiO nanoparticles was single crystalline having face centered cubic phase and has two intense photoluminescence emissions at 305.46 nm and 410 nm. The formation of nano- and micro-structures was confirmed by HRTEM. The in-vitro cytotoxicity and cell viability of human cancer cell HT-29 (Colon Carcinoma cell lines) and antibacterial studies against various bacterial strains were studied with various concentrations of nickel oxide nanoparticles prepared from Moringa oleifera plant extract. MTT assay measurements on cell viability and morphological studies proved that the synthesized NiO nanoparticles posses cytotoxic activity against human cancer cells and the various zones of inhibition (mm), obtained revealed the effective antibacterial activity of NiO nanoparticles against various Gram positive and Gram negative bacterial pathogens. © 2016 Elsevier B.V.

Green synthesis of NiO nanoparticles using Moringa oleifera extract and their biomedical applications: Cytotoxicity effect of nanoparticles against HT-29 cancer cells

Utilization of crust leather waste (CLW) as precursors for the preparation of hierarchical porous carbons (HPC) were investigated. HPCs were prepared from CLW by pre-carbonization followed by chemical activation using KOH at relatively high temperatures. Textural properties of HPC's showed an extent of micro-and mesoporosity with maximum BET surface area of 716m(2)/g. Inducements of graphitic planes in leather waste derived carbons were observed from X-ray diffraction and HR-TEM analysis. Microstructure, thermal behavior and surface functional groups were identified using FT-Raman, thermo gravimetric analysis and FT-IR techniques. HPCs were evaluated for electrochemical properties by cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) by three electrode system. CLC9 sample showed a maximum capacitance of 1960F/g in 1M KCl electrolyte. Results achieved from rectangular curves of CV, GCD symmetric curves and Nyquist plots show that the leather waste carbon is suitable to fabricate supercapacitors as it possess high specific capacitance and electrochemical cycle stability. The present study proposes an effective method for solid waste management in leather industry by the way of converting toxic leather waste to new graphitic porous carbonaceous materials as a potential candidate for energy storage devices.

VIT Unitversity

Journal of Hazardous Materials

Preparation and characterization of hierarchical porous carbons derived from solid leather waste for supercapacitor applications

Zn1-xCuxO (0 ≤ x ≤ 0.2) nanoparticles were prepared by co-precipitation method followed by drying at 200 °C. A non-ionic surfactant Tween-80 which was not reported in earlier studies, was used during preparation process. X-ray diffraction analysis showed the formation of wurtzite ZnO phase nanostructures. The Rietveld analysis showed the appearance of impurity phase (CuO), when Cu2+ was doped with ZnO (x = 0.05 to 0.2). Morphological observations using scanning electron microscopy show the formation of nanoparticles with remarkable morphologies. Photoluminescence spectra revealed emission bands in both UV and visible regions due to the defect centres acting as trap levels. Diffuse reflectance spectroscopy (DRS) showed a decreasing trend in the value of the band gap with increasing Cu2+ doping for lower concentration (x = 0 to 0.1) and then increasing trend for higher concentration of Cu2+ doping. (x = 0.1 to 0.2). The elemental composition of Zn, Cu and O was quantitatively obtained from EDAX analysis where the chemical composition was close to the starting stoichiometries. Magnetisation-Field (M-H) hysteresis curves revealed the appearance of ferromagnetic behaviour, where the magnetic characteristics such as coercivity and saturation magnetization values, were found to be sensitive to Cu2+ doping level. © Copyright 2016 American Scientific Publishers.

Journal of Nanoscience and Nanotechnology

Structural, Optical and Magnetic Properties of Cu-Doped ZnO Nanoparticles by Co-Precipitation Method

Nanoporous carbons (NPC) were prepared from crust leather wastes at temperatures 600, 700, 800 and 900 °C are labelled as CLC6, CLC7, CLC8 and CLC9 respectively. DC electrical conductivities of these NPCs were determined by two-probe method. The effects of compression pressure on electrical conductivity were studied by varying the compression pressure ranging from 17 to 611 KPa. An increase in values of electrical conductivity (EC) was noted for all samples with increase in compression pressures. CLC9 showed relatively higher conductivity values compared to the samples prepared at temperatures. At a compression pressure of 611 KPa, the EC values for CLC6, CLC7, CLC8 and CLC9 were 4.82×10-2, 4.26×10-1, 1.32, 3.7 Ω-1m-1 respectively. The temperature dependent conductivities of NPCs such as CLC6, CLC7, CLC8 and CLC9 revealed that the energy band gap (Eg) values to be 0.455, 0.253, 0.175, 0.145 eV respectively. This Eg values indicate that the NPCs fall under the category of low band gap semiconducting materials. Nitrogen adsorption/desorption isotherms show mixed type with Type I at low relative pressure range (P/Po) and Type IV at high P/Po range indicating that NPCs consists of both micropores (pore diameter, d &lt;2 nm) and mesopores (2 &lt; d &lt;50 nm) according to IUPAC classification. CLC8 possessed a maximum surface area of 716 m2/g estimated by Brunauer-Emmett-Teller (BET) method. Evolution of graphitic peaks was confirmed using Raman spectroscopy and X-ray diffraction techniques to support the electrical conduction mechanisms in NPCs. The surface morphology of the samples were observed using high resolution scanning electron microscope. Copyright © 2016 American Scientific Publishers.