• AMIT KUMAR

Articles written in Bulletin of Materials Science

• Effect of power variation on wettability and optical properties of co-sputtered titanium and zirconium oxynitride films

The present paper deals with deposition of titanium and zirconium oxynitride films prepared from cosputtering titanium and zirconium targets by reactive RF magnetron sputtering. The effect of power variation on various properties of the deposited films is analysed. The film gets transformed from amorphous to well crystalline oxynitride films with gradual increase of target powers as observed from XRD graphs. The films exhibit hydrophilic and hydrophobic behaviours depending upon the presence of various phases. Surface energy decreases as the film properties change from hydrophilic to hydrophobic due to greater contact angle values. The optical properties were measured by UV–Vis–NIR spectrophotometer, transmission spectra and bandgap values show variation with respect to change in elemental composition as determined from EDS analysis.

• Ultraviolet sensing properties of polyvinyl alcohol-coated aluminium-doped zinc oxide nanorods

Undoped and aluminium (Al)-doped zinc oxide (ZnO) nanorods have been synthesized by electrochemical route. The synthesized materials have been characterized by X-ray diffraction, UV–visible spectrometer and scanning electron microscope. The Al-doped ZnO nanorods have been coated with polyvinyl alcohol. Current–voltage characteristics have been investigated in dark and under UV-light illumination. Aluminium doping in ZnO increase its electrical conductivity and further polyvinyl alcohol coating on Al-doped ZnO increase UV sensitivity of the material. Response and recovery time of Al-doped ZnO and PVA-coated Al-doped ZnO nanorods have been recorded. PVA-coated Al-doped ZnO nanorods shows very fast response and recovery time of 10 s in comparison to uncoated ZnO (20 min) nanorods.

• Thromboresistance of functionalized poly(methylmethacrylate): the effect of surface polarity

An implant material when comes in contact with blood fluids (e.g., blood and lymph), adsorb proteins spontaneously on its surface. Notably, blood coagulation is influenced by many factors, including mainly chemical structure and polarity (charge) of the material. The present study describes the methodology to improve the blood compatibility of poly(methylmethacrylate) (PMMA) by incorporating ionic groups with varying polarities. PMMA has been functionalized with different groups containing positive, negative and neutral polarity by the free radical polymerization technique and suchmodification were further confirmed through Fourier transform infrared (FTIR) spectroscopy. The level of thrombogenicity was found three times lower with negatively charged PMMA in comparison to those of positively charged and neutral PMMA. Platelet adhesion was noted almost negligible in all samples after 10 s of blood exposure. High adsorption of fibrinogen from the blood was noticed in the test sample containing a group with positive polarity (thiouronium chloride) while there was no platelet adhesion observed even after 120 s of blood exposure in the test samples containing negatively charged (sulphate) and neutral (hydroxyl group) functional groups.

• Effect of annealing temperature and CdCl$_2$ treatment on the photo-conversion efficiency of CdTe/Zn$_{0.1}$Cd$_{0.9}$S thin film solar cells

We report the effects of annealing in conjunction with CdCl$_2$ treatment on the photovoltaic properties of CdTe/Zn$_{0.1}$Cd$_{0.9}$S thin film solar cells. CdTe layer is subjected to dry CdCl$_2$ treatment by thermal evaporation method and subsequently, heat treated in air using a tube furnace from 400 to 500$^{\circ}$C. AFM and XRD results show improved grain size and crystallographic properties of the CdTe film with dry CdCl$_2$ treatment. This recrystallization and grain growth of the CdTe layer upon CdCl$_2$ treatment translates into improved photo-conversion efficiencies of CdTe/Zn$_{0.1}$Cd$_{0.9}$S cell. The results of dry CdCl$_2$ treatment were compared with conventional wet CdCl$_2$ treatment. Photo-conversion efficiency of 5.2% is achieved for dry CdCl$_2$-treated cells in comparison with 2.4% of wet-treated cell at heat treatment temperature of 425$^{\circ}$C.

• Magnetotactic curcumin iButtonbots as efficient bactericidal agents

The microbial contamination of drinking water is one of the most major concerns of community health in the developing world. Numerous water-borne pathogens are rapidly evolving and becoming resistant to traditional antibiotics.To get an efficacious bactericidal response, an assembly of several antibiotics or increased dosage are being administered, which may produce adverse side effects after prolonged use. Here, we describe a proficient method for disinfecting waterborne coliform bacterial strains of Escherichia coli DH5$\alpha$ from contaminated water samples using magnetic microbotsdecorated with curcumin (CU) conjugates. These magnetic microbots, namely, iButtonbots were composed of soft Agaricus bisporus (button mushroom) microcapsules with inherit antimicrobial properties. The locomotives were coated with magnetite nanoparticles for their remote guidance towards cells and collection along with CU for more enhanced bactericidal response. CU, a major active constituent of the Indian dietary spice turmeric and edible button mushrooms are known to exhibit antimicrobial activity against a wide range of bacterial species. The synergic antibacterial effect of CU and mushroomconstituents, imparts a profound bactericidal property to these magnetic microbots.We have demonstrated that microbots are capable of efficiently killing majority of bacterial cells in contaminated water samples. After extermination of bacteria, magnetic properties of embedded magnetite nanoparticles in porous mushroom matrix, allows collection of microbots from water samples. The presented biocompatible microbots offer an innovative method for rapid decontamination of bacteria-laden drinking water samples.

• Charge transport studies of highly stable diketopyrrolopyrrole-based molecular semiconductor

In the last decade, the diketopyrrolopyrrole (DPP)-based molecular semiconductors received significant prominence for its ability to build ambient stable donor–acceptor type organic materials for numerous microelectronics applications, especially in organic thin-film transistors and photovoltaics. This research article demonstrates the charge transport properties of 3,6-bis(5-(4-(dimethylamino)phenyl)thiophen-2-yl)-2,5-dihexadecylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione[DPP(PhNMe$_2$)$_2$] in single layer device structure prepared by thermal evaporation technique in the frequency and temperature range of 10$^2$–10$^6$ Hz and 133–273 K, respectively. An initial impression of Nyquist plot suggests metal-like behaviour as the impedance increases with an increase in temperature. Semicircle in Nyquist plot suggests Debye-type relaxation. This result has been explained mathematically and fitted equivalent circuit (contact resistance + parallel combination of resistance and capacitance) of device. Resonance frequency have been estimated by the Nyquist plot and crosschecked by Joncher’s Power Law. The frequency exponent ‘s’ is estimated by Joncher’s Universal Power Law and it further shows that charge transport mechanism in the device is quantum mechanical tunnelling. These analyses indicate the existence of Poole–Frenkel effect and explains the charge carrier mobility dependence on the applied field in the studied temperature range.

• # Bulletin of Materials Science

Volume 46, 2023
All articles
Continuous Article Publishing mode

• # Dr Shanti Swarup Bhatnagar for Science and Technology

Posted on October 12, 2020

Prof. Subi Jacob George — Jawaharlal Nehru Centre for Advanced Scientific Research, Jakkur, Bengaluru
Chemical Sciences 2020