John Bosco Balaguru Rayappan

Bio: John Bosco Balaguru Rayappan is an academic researcher from Shanmugha Arts, Science, Technology & Research Academy. The author has contributed to research in topics: Encryption & Thin film. The author has an hindex of 39, co-authored 313 publications receiving 6377 citations.

A review on detection of heavy metal ions in water – An electrochemical approach

Abstract: Most of the metal ions are carcinogens and lead to serious health concerns by producing free radicals. Hence, fast and accurate detection of metal ions has become a critical issue. Among various metal ions arsenic, cadmium, lead, mercury and chromium are considered to be highly toxic. To detect these metal ions, electrochemical biosensors with interfaces such as microorganisms, enzymes, microspheres, nanomaterials like gold, silver nanoparticles, CNTs, and metal oxides have been developed. Among these, nanomaterials are considered to be most promising, owing to their strong adsorption, fast electron transfer kinetics, and biocompatibility, which are very apt for biosensing applications. The coupling of electrochemical techniques with nanomaterials has enhanced the sensitivity, limit of detection, and robustness of the sensors. In this review, toxicity mechanisms of various metal ions and their relationship towards the induction of oxidative stress have been summarized. Also, electrochemical biosensors employed in the detection of metal ions with various interfaces have been highlighted.

A highly selective room temperature ammonia sensor using spray deposited zinc oxide thin film

Abstract: Nanostructured ZnO thin films were deposited on glass substrates at 503 K using spray pyrolysis technique and the films were post annealed at 673 K in air atmosphere for 3 h. The structural, morphological and optical properties of as-deposited and annealed samples were investigated. The annealed films showed uniform spherical morphology in contrast with as-deposited films. XRD patterns of both the annealed and as-deposited films confirmed the polycrystalline nature of the films with hexagonal wurtzite structure. Room temperature ammonia sensing characteristics of annealed films were studied for various concentration levels of ammonia at dry air and humidity conditions. A highest room temperature response of 233 was achieved at 25 ppm of NH3 with a response and recovery times of 20 and 25 s respectively. The response of the sensor to other gases such as methanol, ethanol, 2-propanol, benzyl alcohol and acetone indicated a high selectivity towards ammonia gas. The room temperature (303 K) operation, with high selectivity, repeatability and fast transition times of the sensor together with the low deposition cost suggests suitability for developing a low power cost-effective ammonia sensor.

Effective Ammonia Detection Using n-ZnO/p-NiO Heterostructured Nanofibers

Abstract: Metal-oxide heterostructures are very important materials for developing various toxic gas/chemical detection sensor systems. However, the major factors, such as sensitivity, selectivity, stability, response, and recovery times of the sensors, still need to be optimized for practical technological applications. Low-dimensional materials have shown tremendous potential to solve majority of the critical issues due to their surface chemistry than that of their bulk form. In this paper, the role of nanostructured n-ZnO/p-NiO heterostructure as room temperature (RT) ammonia sensor has been investigated. Toward this paper, the electrospinning method was employed to prepare heterostructure metal-oxides blended with polyvinyl alcohol (n-ZnO/p-NiO) nanofibers. The systematic characterizations of the obtained n-ZnO/p-NiO heterostructure were performed using X-Ray diffractometer, scanning electron microscope, and photoluminescence spectrophotometer. Furthermore, the RT ammonia sensing characteristics were investigated.

Semiconductor metal oxide gas sensors: A review

Abstract: This review paper encompasses a detailed study of semiconductor metal oxide (SMO) gas sensors. It provides for a detailed comparison of SMO gas sensors with other gas sensors, especially for ammonia gas sensing. Different parameters which affect the performance (sensitivity, selectivity and stability) of SMO gas sensors are discussed here under. This paper also gives an insight about the dopant or impurity induced variations in the SMO materials used for gas sensing. It is concluded that dopants enhance the properties of SMOs for gas sensing applications by changing their microstructure and morphology, activation energy, electronic structure or band gap of the metal oxides. In some cases, dopants create defects in SMOs by generating oxygen vacancy or by forming solid solutions. These defects enhance the gas sensing properties. Different nanostructures (nanowires, nanotubes, heterojunctions), other than nanopowders have also been studied in this review. At the end, examples of SMOs are given to illustrate the potential use of different SMO materials for gas sensing.

A New Strategy for Heavy Metal Polluted Environments: A Review of Microbial Biosorbents

Abstract: Persistent heavy metal pollution poses a major threat to all life forms in the environment due to its toxic effects. These metals are very reactive at low concentrations and can accumulate in the food web, causing severe public health concerns. Remediation using conventional physical and chemical methods is uneconomical and generates large volumes of chemical waste. Bioremediation of hazardous metals has received considerable and growing interest over the years. The use of microbial biosorbents is eco-friendly and cost effective; hence, it is an efficient alternative for the remediation of heavy metal contaminated environments. Microbes have various mechanisms of metal sequestration that hold greater metal biosorption capacities. The goal of microbial biosorption is to remove and/or recover metals and metalloids from solutions, using living or dead biomass and their components. This review discusses the sources of toxic heavy metals and describes the groups of microorganisms with biosorbent potential for heavy metal removal.

Humidity Sensors Principle, Mechanism, and Fabrication Technologies: A Comprehensive Review

Abstract: Humidity measurement is one of the most significant issues in various areas of applications such as instrumentation, automated systems, agriculture, climatology and GIS. Numerous sorts of humidity sensors fabricated and developed for industrial and laboratory applications are reviewed and presented in this article. The survey frequently concentrates on the RH sensors based upon their organic and inorganic functional materials, e.g., porous ceramics (semiconductors), polymers, ceramic/polymer and electrolytes, as well as conduction mechanism and fabrication technologies. A significant aim of this review is to provide a distinct categorization pursuant to state of the art humidity sensor types, principles of work, sensing substances, transduction mechanisms, and production technologies. Furthermore, performance characteristics of the different humidity sensors such as electrical and statistical data will be detailed and gives an added value to the report. By comparison of overall prospects of the sensors it was revealed that there are still drawbacks as to efficiency of sensing elements and conduction values. The flexibility offered by thick film and thin film processes either in the preparation of materials or in the choice of shape and size of the sensor structure provides advantages over other technologies. These ceramic sensors show faster response than other types.