Chapter 24 - Synthesis and applications of carbon dots from waste biomass

Abstract

Carbon dots (C-dots) are a new type of carbon-based zero-dimensional material that has gained a lot of attention because of its superior properties like smaller size, biocompatibility, low toxicity, water solubility, high sensitivity, high quantum yield, tuneable fluorescence emission and excitation, and ease of modification. Carbon dots are also known as carbogenic nanodots because they have higher oxygen content. Carbon-based products are traditionally made from nonrenewable sources like coal and petroleum coke. However, rising demand and dwindling nonrenewable resources need the production of carbon-based products from renewable raw materials. Biomass waste (agricultural residues, municipal solid trash, and food waste) is a renewable resource with a high carbon content that can be exploited to produce high-value carbon products (45%–55%). Carbon dots can be made from biomass waste utilizing top-down and bottom-up procedures such as hydrothermal carbonization, microwave-assisted carbonization, ultrasonic-assisted carbonization, pyrolysis, and chemical oxidation, among others. Carbon dots created from waste biomass can be efficiently used because of various advantages viz; generated from garbage waste so cost shall be low and its availability in large amounts. Utilize trash created, large-scale production viability, and low cost. Carbon dots made from biomass waste can be self-passivated during the synthesis process, unlike carbon dots made from chemical agents, because the abundance of carbonaceous compounds in biomass waste allows carbonization and surface passivation to occur simultaneously, with long-chain compounds or heteroatom-containing compounds acting as surface passivation agents. Carbon dots made from biomass waste have excellent photostability, high fluorescence quantum yield, excellent biocompatibility, low cytotoxicity, high photocatalytic activity, and easy surface fictionalization, making them useful in a variety of applications including drug delivery, bioimaging, chemical sensing, environmental monitoring, disease diagnosis, solar cells, and catalysis. Although much effort has gone into making carbon dots from waste biomass, there are still a number of obstacles to overcome, including large-scale production of high-quality carbon dots from renewable biomass waste, a lack of understanding of the photoluminescence mechanism, precise control of surface functionalization during the synthesis process, and a maximum absorption wavelength in the ultraviolet to blue range, which limit its application in the field of bioimaging. As a result, more research is needed to overcome these constraints and generate carbon dots that can operate in wavelengths ranging from far red to near-infrared.