Development of Novel Carbon Dot Hybrid Sensors for the Detection of Environmental Pollutants and Biomarkers

Abstract

Nanocarbon materials can be potentially used in the growth of next-generation optical biosensors. Driven by its low-cost, simplicity, utility, high sensitivity and carbon-based optical biosensors have been widely researched as an alternative tool to aid scientists in identifying environmental pollutants and important biomolecules. In this context, the thesis entitled, “Development of novel carbon dot hybrid sensors for the detection of environmental pollutants and biomarkers” is an embodiment of investigations aimed at the design and development of metal doped carbon quantum dots sensors, sensing protocols, and exploring the practical applications of these sensors in the detection of the analytes in model plant or living organism for specific applications. The thesis has been divided into eight chapters. Chapter 1 presents a brief literature review on proper selection of molecular precursors, surface passivating agents, heteroatoms and metal precursors can produce carbon nanomaterials with biocompatibility, high QY and long-term stability which may offer a wide variety of applications. The underlying photophysical process responsible for the alteration of fluorescence response of the carbon dot in presence of the analyte has been discussed. The recent development of literature on the application of carbon dot in both environmental and biomarker sensing has been included. The goal of the thesis is defined at the end of the chapter 1. In chapter 2, Manganese dioxide-carbon dot (MnO2CD) composite nanoparticles of size 45 nm have been synthesized and utilized for the detection of arsenic, organoarsenic and organothioarsenic compounds such as dimethylarsenate (DMA), dimethyldithioarsinate (DMDTA), and dimethylmonothioarsinate (DMMTA). Chapter 3 and 4 describes the development of a betaine-modified carbon dot (BT@CD) and Ag- doped CD sensor for monitoring Cr(VI) and perchlorate respectively in water as well as real samples. Due to its easy translocation in the vascular bundles, these fluorescence nanosensors can be applied to detect Cr(VI) in rice plants (Oryza Sativa) through fluorescence confocal imaging. The treatment of rice plants with BT@JCDs in the concentration range of 0.2 to 1g/mL triggered photophysical parameters promoting plant growth. In chapter 5 and 6, we have constructed different surface passivated metal carbon dot integrated probes Ca@Cu-CD and AuNP@GCD for the detection of glycine and dopamine respectively. The exceptional combination of fluorescence and conducting properties establishes our probes as a dual sensor for the nonenzymatic detection of two neurotransmitter glycine and dopamine in real serum samples. Our effort to explore the use of carbon dot in developing wearable sensors has been presented in chapter 7. We have fabricated a mechanically stable, stretchable hydrogel patch by integrating Cu-CD in a PVA-Agar hydrogel. The hydrogel patch sensor can monitor Ca2+ level in sweat in both fluorescence and electrical mode. At the same time because of excellent skin adhesiveness and flexibility MCD@PAGH sensor can be attached to any joint to monitor strain induced by body motion in both electrical and fluorescence mode.