Multilayer accordion like Ti3C2Tx MXene is prepared by selective etching of Al layer from Ti3AlC2 MAX phase. For better gas sensing responses, a minimal amount of TiO2 decoration is being carried out by annealing the Ti3C2Tx MXene in an argon atmosphere at 550 °C for 6 h. The X-ray diffraction pattern shows successful removal of Al layer and TiO2 decoration on Ti3C2Tx MXene surface which is well supported by field emission scanning electron microscope images. Due to TiO2 decoration, MXene shows semiconducting behaviour and corresponding bandgap is 3.2 eV. Resistance of TiO2 decorated MXene sample increases in presence of H2, CH4 and NO2 gases at room temperature. However, resistance of the sample decreases for H2, and CH4 gases and increases for NO2 gas at 100 °C which shows n-type semiconducting behaviour. Also, at 100 °C, sensitivity increases by one order to that of room temperature gas response of TiO2 decorated MXene sample.
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Methane sensing studies of ex-situ oxidized sputtered V2O5 nanostructured films: Effect of post oxidation duration
The effect of microstructural modifications of V2O5 thin films, obtained through alterations in post oxidation duration, on methane sensing behavior is reported for the first time. Three different oxidation times viz., 1 h, 3 h and 5 h yielded varied microstructure and vibrational properties as evident from XRD and Raman investigation. These changes in properties manifest as differences in gas sensing behavior. Methane sensing properties of V2O5 was investigated in temperature range from 100 to 300 °C and optimum operating temperature of 200 °C was identified for all three samples. Films oxidized for 1 h showed the highest response due to favorable surface conditions which are discussed. These results will help in tailoring microstructure towards device level application processes.
Recent progress in Nanostructured Metal Oxides based NO2 gas sensing in India
The metal oxides are considered as an outstanding semiconductor material to sense several toxicants from the environment. In particular, the nanostructure containing rod, wire, and tube-like morphology of metal oxides were widely utilized to fabricate effective gas sensors worldwide. Out of number of toxicant, nitrogen dioxide (NO2) is one of the highly reactive gas, results from the burning of fuel from vehicles, power plants, and off-road equipment.The exposures to NO2 may giverise to the development of the respiratory diseases and leads to the death. Therefore, the efficient detection of NO2 gas is the urgent need of recent era. More than 5000 research articles were published on the NO2 gas sensing worldwide. The researchers from India is also contributed a lot to detect the NO2 gas via nanostructured metal oxides powder and thin films. The aim of the present article is to explore the recent advances of NO2 gas sensors based on metal oxide nanomaterials within the country. The review begins with the general introduction of metal oxide, gas sensorand NO2 gas sensor and followed by the broadly discussion of major research groups working in India and their finding in the fieldof nanostructured metal oxide for the fabrication of NO2 gas sensors. Moreover, various factors likegas concentrations, working temperature, morphologies, sensor response, selectivity, etc. of metal oxides were discussed in the present report. The report concludes with the future directions and opportunities in the field of detection of NO2 gas in India and world.
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Recent progress in Nanostructured Metal Oxides based NO2 gas sensing in India
A comprehensive review on functionalized Hydroxyapatite nanostructures based gas sensors for environmental pollutant monitoring
The utilization of advanced sensing techniques for detecting and monitoring toxic gases in industry and the environment is a predominant action. For such applications, the sensor material should possess higher sensitivity, faster detection, and real-time operation. Mostly, metal oxides (MOs) are preferred for gas sensing purposes owing to their excellent sensing property, wide band-gap, electrical conductivity, and high surface reactivity. But, the same MOs lag in many perspectives like low selectivity, higher operating temperature (> 400 °C), more power consumption, and reduced stability. Since more emphasis is given to materials that operate at room temperatures like nano-hydroxyapatite (nHAp), it’s a bio-ceramic material used for chemical gas sensing. The nHAp is a matrix of rich calcium (Ca2+) and phosphate (PO43-) ions. In chemical gas sensors, the nHAp possess significant properties like large surface phosphate-hydroxide (P-OH) groups, ionic conductivity, porous nature, and ion exchange capability for effective gas molecule interaction. In this profound review, we discussed the nHAp structure with different fabrication techniques for gas sensing. Particularly, functionalized nHAp with MO and polymers were focused and their stability, sensitivity, selectivity, and adsorption rate are presented along with different mechanisms. Existing challenges and future perspectives of nHAp material are also highlighted.
Defect mediated optical detection of ammonia using SnO2 nanoparticle
SnO2 with oxygen vacancies, an n-type gas sensing material used commercially as resistive sensors at high temperatures, suffers from the drift in voltage, contact resistances and poor selectivity. These prevailed defects in rutile SnO2 offer excellent optical properties which remain to be explored for the gas sensor. Apart from advantage of contactless operation with no direct voltage application, an optical method with the varied light energies is highly beneficial for excitations of the deep electronic states at ease, with opportunity to improve the sensor response measurement quickly in selective manner. In this direction, we report the synthesis and characterization of SnO2 nanostructures with emphasis on their Raman and photoluminescence properties. In subsequence, the crucial role of various defects in displaying the improved optical responses and selectivity for ammonia are highlighted.
Genome-wide mutation/SNP analysis, biological characteristics, and Pan-India prevalence of SARS-CoV-2 Variants of Concern
The origin of COVID-19 pandemic, caused by SARS-CoV-2, was traced to Wuhan, China. Thereafter, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolved into various variants owing to genome-wide mutations, causing emergence of multiple variants, including Variant of Interest and Variant of Concern. Here, we discuss genomic architecture of SARS-CoV-2, as well as its multiple variants- alpha, beta, gamma, and delta, along with their biological properties, such as transmissibility, reduction in antibody-mediated neutralization, virulence, disease severity, vaccine effectiveness, and the prevalence across the India vis-à-vis world. Our data on VOC, pooled from the Global Initiative on Sharing All Influenza Data up to 31 October 2021, shows around 89% prevalence of delta VOC across various Indian States. Whereas alpha, beta, and gamma variants show 10.44%, 0.57%, and 0.11% prevalence, respectively. Compared with global scale, the reported Indian prevalence of alpha, beta, gamma, and delta are 0.40%, 0.63%, 0.04%, and 1.7%, respectively. Furthermore, prevalent vaccines of various natures show significantly reduced effectiveness against these VOCs, necessitating urgent need for development of effective prophylactic vaccines and potential therapy to contain the pandemic.
Recent development in carbon nanotubes based gas sensors
Technological expansion in nanotechnology have given upsurge to a new generation of functional organic nanomaterials with well-defined characteristics and controlled shape, allowing for a large number of possible applications. Innovative detection systems for the reliable and timely monitoring of dangerous gases in industrial processes and the environment are vital for maintaining optimum health and safety. In this context, semiconductor metal oxides, polymers, and carbon-based materials are often utilized materials for the applications of gas sensing. Metal oxide gas sensors are low-cost and have good sensitivity, however, they frequently demand higher working temperatures above ~120°C. Polymer-based gas sensors, on the other hand, are generally used to detect volatile organic compounds (VOCs) and have a high sensitivity and quick response, but they are prone to irreversibility and instability over time. Carbon-based gas sensors are becoming increasingly popular due to their unique characteristics and high sensitivity. Carbon nanostructures, such as carbon nanotubes (CNTs), are generally recognized as prospective nanomaterials for developing a new gas sensor with important nanotechnology implications. Carbon nanotubes have sparked a lot of interest because of their great surface-area-to-volume ratio, chemical inertness, nanoscale architecture, and hollow core, all of this makes them appealing for nanotechnology applications currently and in the future. This review work covers the current state-of-the-art work and advancements in gas sensors development based on organic nanomaterials; carbon nanotubes in particular.
Graphene – properties, production and rising applications: A review
Out of all the 2D materials discovered until now, Graphene has been the hot topic to date. Graphene is a two dimensional-sp2 bonded, single-layer membrane of a carbon atom tightly bonded in a hexagonal honeycomb lattice. The layers of graphene are piled up to form graphite. The single layers of graphene are held together by weak Vander Waal forces in graphite, which are then separated by exfoliation of graphene from graphite. Graphene has marvelous electrical, mechanical, and optical properties which makes it suitable for use in many modern technologies towards an excellent replacement to the other materials used by the industries. The remarkable properties and nature of graphene made it a very promising material for the future. This review discusses about fundamentals of graphene, properties that makes graphene an extraordinary material and its vast number of applications
Viral infection mitigations using advanced nanomaterials and tools: lessons from SARS-CoV-2 for future prospective interventions
The emergence of recent corona virus SARS-CoV-2-led pandemic infection has generated the incessant demand for the evaluation and development of suitable advanced materials for controlling this and future unforeseen viral infections. The current nanoscience-based materials are being evaluated for possible appliances at different stages encompassing, fields locations for control, identification of virus spread, diagnosis of infection and potential therapeutic interventions by drug development. Assorted materials like carbon nanomaterials, metal nanoparticles, metal organic frameworks (MOFs), covalent organic framework (COF) materials, 2D materials, optical tweezers, artificial cells, etc. have been extensively investigated for the diagnosis, protection, and as therapeutics for viral infections. Herein, the existing materials and nanotechnological tools proposed or evaluated for controlling different viral infections and specifically, COVID-19 are deliberated. An insightful exploration of the advances in materials science, nanoscience and nanobiotechnology has been kept in core focus with perspective for controlling the similar type of infections in future.
X-ray and Raman study of CH3NH3PbI3 perovskite nanocrystals
Organic-inorganic hybrid perovskite nanocrystals have gained considerable attention for optoelectronics applications due to their unique properties like high light absorption coefficient, band gap tunability, and larger diffusion length. In this work, the ligand-assisted re-precipitation method (LARP) was employed to synthesize CH3NH3PbI3 nanocrystals (NCs). The optical and structural properties of nanocrystals depend on their size. X-ray diffraction (XRD) and small-angle X-ray scattering (SAXS) techniques are used to determine the crystal structure, particle size distribution, and surface to volume ratio of CH3NH3PbI3 nanocrystals. The organic-inorganic interactions of CH3NH3PbI3 nanocrystals are studied by Raman spectra at room temperature. This study will provide the basis to interpret the morphological properties of perovskite nanocrystals for their full exploitation in different optoelectronics applications