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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 (PO₄^3-) 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.

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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https://pubs.thesciencein.org/journal/index.php/jmns/article/view/294

Recent progress in Nanostructured Metal Oxides based NO2 gas sensing in India

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. 

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.

Contraceptives are playing an integral role in maintaining human reproductive and sexual health in present society. Currently available contraceptives are based on the ease of applying, comfort during use, and activity period. The materials used in the development of contraceptives can be a determining factor towards the desired features for possible adoption. Here, in this review, we have discussed the important and futuristic contraceptives in terms of biomaterials used in the production and techniques which can be used as inspiration for better contraceptives in the future. Especially, this review discusses long-acting reversible hormonal contraceptives, Intrauterine Devices (IUDs), oral pills, vaginal rings, and patches along with the comparison of these with several polymer-composite-based implants for contraception. The overall analysis indicated possible development of better contraception devices in near future, particularly with further improvements in biomaterials that are used for the production of advanced multipurpose polymer-composite-based contraceptive implants.

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

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.

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