Manika Khanuja

Pulse like hydrogen sensing response in Pd nanoparticle layers

This study reports an enhanced and unusual pulse like hydrogen sensing response in Pd nanoparticle layers. The faster H adsorption due to increased surface area and closure of conducting paths as a result of lattice expansion on hydride formation are the primary reasons for this. In comparison, Pd thin films exhibit a slow and subdued sensing response because of the overlap of the above two opposing effects and hydrogen induced lattice strain. Temperature independent conductivity in the temperature range of 20–300K confirms the presence of interparticle gaps in the case of Pd nanoparticle layers.

Hydrogen induced lattice expansion and crystallinity degradation in palladium nanoparticles: Effect of hydrogen concentration, pressure, and temperature

A detailed structural study involving in situ glancing angle x-ray diffraction (GAXRD) analysis carried out on Pd nanoparticle and thin film samples at hydrogen concentrations of 2%, 5%, and 10% over temperature ranging from −100 to 55 °C and hydrogen pressures ranging from 250 to 1000 mbars is reported. Variation in the lattice constant has been interpreted in terms of hydrogen content in α and β PdHx phases, and decrease in XRD peak intensity has been interpreted in terms of hydrogen induced degradation in crystalline quality and temperature induced lattice disorder. It is observed that Pd–H interaction is strongly influenced by the temperature and pressure dependences of physisorption, chemisorption, and diffusion. These results show that the increased surface area, interparticle gaps, and electronic enhancement result in enhanced Pd–H interaction in case of nanoparticles. In addition, the presence of single β phase and lower crystallinity degradation is observed in the case of Pd nanoparticles in comp...

Visible light induced bactericidal and photocatalytic activity of hydrothermally synthesized BiVO4 nano-octahedrals

In the present work, monoclinic bismuth vanadate (m-BiVO4) nanostructures have been synthesized via simple hydrothermal method and employed for visible light driven antimicrobial and photocatalytic activity. Morphology (octahedral) and size (200-300nm) of the m-BiVO4 are studied using transmission electron microscopy (TEM). The crystal structure of m-BiVO4 (monoclinic scheelite structure) is confirmed by high resolution-TEM (HRTEM) and X-ray diffraction (XRD) studies. The band gap of m-BiVO4 was estimated to be ca. 2.42eV through Kubelka-Munk function F(R∞) using diffuse reflectance spectroscopy (DRS). Antimicrobial action of m-BiVO4 is anticipated by (i) shake flask method, (ii) MTT [3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide] assay for cytotoxicity. SEM analysis has been carried on Escherichia coli (E.coli) before and after treatment with nanostructure materials to reveal the mechanism underlying the antimicrobial action. Antimicrobial activity is studied as a function of m-BiVO4 concentration viz. 20, 40, 60 and 80ppm. The bacterial growth is decreased 80% to 96%, with the increase in m-BiVO4 concentration from 20ppm to 80ppm, respectively, in 2h. Photocatalytic activity and rate kinetics of m-BiVO4 nanostructures have been studied as a function of time on methylene blue (MB) dye degradation which is one of the waste products of textile industries and responsible for water pollution.

Aspect-ratio-dependent photoinduced antimicrobial and photocatalytic organic pollutant degradation efficiency of ZnO nanorods

The photo-antimicrobial and photocatalytic performance of ZnO nanorods as a function of aspect ratio are presented. The antibacterial activity of the synthesized ZnO nanorod samples against Gram-negative and Gram-positive bacteria (Staphylococcus aureus and Escherichia coli, respectively) was determined by shake flask method with respect to time. ZnO nanorods with high aspect ratio showed superior antimicrobial and photocatalytic activity. These results are supported by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, ultraviolet–visible (UV–Vis) spectroscopy, photoluminescence, and Brunauer–Emmett–Teller (BET) studies. Degradation of methylene blue dye as model organic pollutant was used to assess their photocatalytic activity. Pseudo-first-order rate kinetics was used to calculate the photocatalytic reaction rate constant. The mechanisms for both antimicrobial and photocatalytic activity are elucidated.

Impact of Synergistic Association of ZnO-Nanorods and Symbiotic Fungus Piriformospora indica DSM 11827 on Brassica oleracea var. botrytis (Broccoli)

In the present work, novel nanotool called ‘nano-embedded fungus’ formed by impact of synergistic association of ZnO-nanorods and fungus Piriformospora indica DSM 11827, for growth of Brassica oleracea var. botrytis (Broccoli) is reported. ZnO-nanorods were synthesized by mechanical assisted thermal decomposition process and characterized by scanning electron microscopy (SEM) for morphology, X-ray diffraction for structural studies and UV-vis absorption spectroscopy for band gap determination. Nanoembedded fungus is prepared by optimizing ZnO-nanorods concentration (500 ppm) which resulted in the increased biomass of P. indica, as confirmed by dry weight method, spore count, spread plate and microscopy techniques viz. SEM and confocal microscopy. Enhancement in B. oleracea var. botrytis is reported on treatment with nanoembedded fungus. According to the authors, this is the first holistic study focusing on the impact of ZnO-nanorods in the enhancement of fungal symbiont for enhanced biomass productivity of B. oleracea plant.

Magnitude and time response of electronic and topographical changes during hydrogen sensing in size selected palladium nanoparticles

In this study, size dependence of electronic and topographical effects during Pd-H interaction has been investigated by studying H sensing in thin films of size selected and monosized nanoparticles having 15, 20, and 25 nm diameter. By separating the contributions of electronic changes due to H adsorption and topographical changes due to lattice expansion to hydrogen sensing, it has been shown that the magnitude and response time of these changes are sensitive functions of nanoparticle size and measurement temperature. The temperature dependence of saturated resistance corresponding to these changes provides important information about the nature of electronic and topographical changes.

Role of Nanoparticles on Plant Growth with Special Emphasis on Piriformospora indica: A Review

Agricultural nanotechnology is a tool that has the potential to overcome the challenges associated with conventional farming including low productivity and unbalanced ecosystem through nano-formulation of fertilizers (or pesticides, herbicides), efficient management of water and soil resources through porous nanostructures leading to enhancement in nutritional quality as well as quantity, simultaneously regenerating soil fertility, and stabilization of erosion-prone surfaces. In the present chapter, the synergetic association of nanoparticles and fungus called Nanoembedded fungus, a novel nanotool, and its role to (1) enhance the agriculture yield and to (2) overcome the existing agricultural challenges are discussed. The present chapter focuses on the interaction of nanoparticles (Ag, carbon nanotubes, TiO2, and ZnO) with fungus Piriformospora indica (Hymenomycetes, Basidiomycota) with emphasis on its correlation with plant growth.

A review and recent developments on strategies to improve the photocatalytic elimination of organic dye pollutants by BiOX (X=Cl, Br, I, F) nanostructures

The main environmental problems associated with water body pollution are typically those caused by the discharge of untreated effluents released by various industries. Wastewater from the textile dye industry is itself a large contributor and contains a huge number of complex components, a wide spectrum of organic pollutants with high concentration of biochemical oxygen demand (BOD)/chemical oxygen demand (COD) and other toxic elements. One of several potential techniques to degrade such reactive dyes before being discharged to water bodies is photocatalysis, and bismuth-based photocatalysts are rapidly gaining popularity in this direction. Bismuth oxyhalides, BiOX (X=Cl, Br, I, F), as a group of ternary compound semiconductors (V-VI-VII), have been explored extensively for their photocatalytic activity due to their unique crystal lattice with special layered structure in pure as well as modified form. With suitable band gap and band edge positions, which are a required condition for efficient water breakup and high photon absorption, BiOCl scores over other oxyhalides. Photocatalytic activity depends on many factors such as synthesis method, morphology, size, illumination type, dye choice among others. This paper gives a critical review on bismuth oxyhalides as a family on various aspects of modifications such as doping (with unique and interesting metals as well), morphology and synthesis parameters, polymer and carbon assisted composites in order to further enhance the photocatalytic efficiency in UV/visible region of solar spectrum.

Development of MoSe2 Nano-Urchins as a Sensing Platform for a Selective Bio-Capturing of Escherichia. coli Shiga Toxin DNA

The present study was aimed to develop “fluorine doped” tin oxide glass electrode with a MoSe2 nano-urchin based electrochemical biosensor for detection of Escherichia coli Shiga toxin DNA. The study comprises two conductive electrodes, and the working electrodes were drop deposited using MoSe2 nano-urchin, and DNA sequences specific to Shiga toxin Escherichia coli. Morphological characterizations were performed using Fourier transforms infrared spectrophotometer; X-ray diffraction technique and scanning electron microscopy. All measurements were done using methylene blue as an electrochemical indicator. The proposed electrochemical geno-sensor showed good linear detection range of 1 fM–100 µM with a low detection limit of 1 fM where the current response increased linearly with Escherichia coli Shiga toxin dsDNA concentration with R2 = 0.99. Additionally, the real sample was spiked with the dsDNA that shows insignificant interference. The results revealed that the developed sensing platform significantly improved the sensitivity and can provide a promising platform for effective detection of biomolecules using minute samples due to its stability and sensitivity.

Morphology-Preferable MoSe2 Nanobrooms as a Sensing Platform for Highly Selective Apta-Capturing of Salmonella Bacteria

The present report employed nanobroom (NB)-shaped two-dimensional molybdenum diselenide (MoSe2) for the preparation of a sensing matrix for the detection of Salmonella paratyphi. An aptamer specific to salmonella was immobilized onto MoSe2NB-modified fluorine-doped tin oxide via glutaraldehyde cross-linking. Structural and morphological characterizations were performed using UV–vis spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. Characterizations confirmed the nanobroom morphology and nanosize of the MoSe2 material. Electrochemical studies revealed a good linear detection range of 10–2–10–10 CFU/mL with low detection limit of 1 × 10–10 CFU/mL and with R2 = 0.98. The developed preferable nanobroom-shaped sensing matrix can provide a promising platform for rapid and accurate detection of Salmonella in real samples due to its tremendous stability and sensitivity.