Comprehensive Analysis on Designing Cobaltite Spinel based Nanocomposite Sensors for Detection of Toxic Chemicals and Gases

Abstract

Spinel structures play very important role in many areas of materials science due to the large diversity of oxide compounds for various applications. Specifically, cobaltite-based spinels containing two distinctcation shave been use das potential sensordueto the irunique semiconducting and redoxproperty with desirable results. These nsing activity of these materials can be furtherenhanced by modifying reduced grapheneoxide(GO) and graphitic carbon nitride(g-C3N4) asasupportonit. This inturn allows the preparation of novel materials with promising characteristics. Keeping this in mind, this PhD thesisis focused on designing cobaltitespinel-based nano composite for the sensing of toxic analytes both in gas and liquid for mthrough the variation of their shape, size, morphology, and substitution of cations followed by different syntheticroutes. Broadly,it is focussedon two major objectives. The first major objective eisto modify different spinel based sensors(MnCo2O4, ZnCo2O4, and NiCo2O4) with reduce dgr phene oxide and use themas potential sensor for the detectionoftoxic gases(H2, NO2, andCH4) while the second major objectiveis to design spinel (MnCo2O4 and CuCo2O4) with both reduced graphene oxideandgraphitic carbon nitride for the detection fhazardous chemicals like pesticideandherbicides(chlorpyrifos and glyphosate). In the first project, I have demonstrated the morphological analysis of different structures (rod, sphere, flakes, and flower) based MnCo2O4 modified with rGO as potential sensor for detection of H2 gas (Chapter2, Sens. ActuatorsBChem., 2023, 380, 133348). After that, highlighting the effect off lowers haped spinel on sensing, the second project focusedona comparative study between normally synthesized ZnCo2O4 and MOF-derived ZnCo2O4 flower modifiedrGO for the detection of CH4 gas (Chapter3, Env. Sci. Nano, DOI:10.1039/D3EN00205E). In view of previous study, in the third objective, effort was given to de signacation substitited MOF-derived spinel based nano composite based potentialsensor for the sensing of NO2 gas (Chapter4, Sens. Actuators B Chem., 2024, 403,135182). In the electro chemical sensing part, this thesis documents our attempts to design spinel based nano composite supported by g-C3N4 as anefficientsensor for the detection of hazardous chemicals In this regard,in the fourth project,explorationon the design of MnCo2O4 particles decorate donbothrGOandg-C3N4 sheets to design highly selective and sensitive chlorpyrifossensor was done (Chapter5, J. Electroanal.Chem. 2022, 909,116115).Lateron, research was conducted to determine whether adequate growth of nano particlesong-C3N4 (H-C3N4) could be achieved by surface modification and improved electrocatalytic properties of the spinel nano particles.Towards this purpose, rGO ixand H-C3N4 modified MOF-derivedCuCo2O4 nanocomposite was designed a sanefficient sensor for the detection of glyphosate (Chapter6, Ind. Eng.Chem.Res., 2023,62, 3477). All the material spresentedin this thesis provedtobe highly sensitive, selective, stable, efficient, and recyclable system for the above applications which are of environmental significance.