SYNTHESIS OF TWO-DIMENSIONAL NANOMATERIALS FOR ELECTROCHEMICAL SENSING APPLICATION

Abstract

Unique surface features, chemical, optical, and electronic properties of 2 dimensional (2D) nanomaterials have made them attract tremendous recognition for a vast range of applications. 2D nanomaterials like hexagonal boron nitride (h-BN), transition metal dichalcogenides (TMDs), black phosphorus, and layered double hydroxides (LDHs) etc. are being widely explored in the field of sensing. The large surface area makes 2D nanomaterials ideal platforms for loading more and more entities for sensitive detection of the target analyte. Amongst various 2D nanomaterials, graphene has displayed a substantial potential for further exploration due to its vast range of interesting properties. Other 2D nanomaterials (Mn3O4 and α-Fe2O3) are used for sensing due to their interesting properties viz. high charge carrier ability, good biocompatibility, and chemical stability etc. In this work, Mn3O4 and α-Fe2O3 nanoparticles were synthesized using simple co-precipitation and hydrothermal methods, respectively. The integration of these nanomaterials with graphene oxide (GO) for the detection of fumonisin B₁ demonstrated excellent performance, with a low limit of detection (LOD) and high recovery rates. It provides high specificity, and affinity toward target antigens. The sensing method uses the electrochemical transduction method. It is a cost-effective method as compared to optical methods. It has very high sensitivity, often reaching pico/nanomolar detection limits, suitable for miniaturization and point-of-care applications, and also compatible with label-free detection formats. It uses covalent immobilization over physical adsorption. The nanostructure surface has reactive groups (–COOH, and –NH₂,) for antibody conjugation via standard chemistries e.g. EDC/NHS coupling. It targets Fc region to maximize antigen-binding site accessibility. It provides sufficient surface area for antibody loading. The blocking agents like BSA is used post immobilization to reduce background signal. The covalent binding which is a chemical method is more favorable when testings are done in buffer solutions and repeated measurements are to be recorded. Therefore, the nano composites (GOMn3O4, and α-Fe2O3/rGO) are used for covalent vi attachment of antibodies on the immobilization matrix. The growth of mycotoxins is a major global challenge in food contamination to both humans and animal health. Amongst various types of mycotoxins, fumonisin B1 is very important mycotoxin, and is designated as a carcinogen by the International Agency for Research on Cancer (IARC), placed it in class 2B group of human carcinogens. Conventional techniques used for detecting the mycotoxins are time-consuming, expensive, cumbersome, and require trained personnel for operation. The findings of the research work conducted for achieving the above-mentioned objectives have been divided into 5 chapters. Chapter 1 begins with a brief introduction to nanomaterials, and nanotechnology, gradually followed by intriguing properties of 2D nanomaterials, a discussion about biosensors and their components, choice of nanomaterials (GOMn3O4, and α-Fe2O3/rGO) as an immobilization matrix, based on a comprehensive literature review. The chapter then elucidates the motivation to pursue this work and the objectives of the present thesis work. Chapter 2 describes in detail the methods chosen for the synthesis of nanomaterials, and the technique used for thin film formation. This is succeeded by a discussion on all the characterization techniques which have been used in the present thesis work for confirmation of the formation of desired nanostructures and testing the biosensing performance of the fabricated platform. Chapter 3 presents the study on detection of FB1 using synthesized Mn3O4/GO nanostructures. Chapter 4 presents the study on detection of FB1 using synthesized α-Fe2O3/rGO nanostructures. Chapter 5 summarizes the conclusions, future of sensors. This chapter winds up with prospects of this research work.