Advances in Nanocomposite Thin-Film-Based Optical Fiber Sensors for Environmental Health Monitoring—A Review

Abstract

The importance of nanocomposite-based fiber optic sensors has immensely increased in the fields of chemical, gas, bio-analytes, food processing, environmental indoor/outdoor air quality monitoring, safety issues, and heavy metal for accurate detection due to advancements in modern science and technology. Exposure to harmful analytes that exceed the optimum concentrations is dangerous and it is essential to monitor and keep human beings healthy. The growing prevalence of the health risks associated with various toxic/polluting gases, chemicals, and heavy metals, as well as the need for rectification measures, the standard regulations have prompted extensive research into the development of efficient optical sensors that can detect trace levels of pollution from various sources. For sensing various harmful gases, chemicals, and heavy metals, nano thin film optical sensor structures based on various sensing materials such as metal oxide semiconductors, polymers, metals, carbon nanotubes, graphene, and others have been explored. These sensors are found to have a better sensing response in terms of sensitivity, selectivity, response time, recovery time, and repeatability than uncoated-based optical sensors. Various optical sensing setups to detect gases (NH <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> , NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , CO, CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and heavy metal substances <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\vphantom {^{\int ^{A}}}$ </tex-math></inline-formula> such as (Hg <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+2</sup> , Cr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+2</sup> , Cu <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+2</sup> , Pb <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+2</sup> , Cd <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+2</sup> ) are frequently detected harmful compounds in the environment in the present report for the different sensing methods. We focused on the recent advancement of the nanomaterial-based fiber optic sensor for gas, chemical, and heavy metal detection for monitoring environmental health in the review article.