Microplasma Engineering of Bioresource-Derived Surafce-Functinoalized Graphene Quantum Dots as Ultrahigh Sensitive Optical Nanosensors

Recently, graphene quantum dots (GQDs) caught attention due to their a vast range of application in different fields of science and technology. It is a new type of cgraphene-based nanomaterials with lateral size less than 10 nm. GQDs have attracted many researchers because of its tunable fluorescence, chemical and photo stability, low toxicity and biocompatibility. Synthesizing GQDs using bioresource-containing precursors is an environment friendly and green route. Graphene quantum dots show high conductivity, larger surface area and long life. Therefore, GQDs can be used as catalysts, fuel cells, drug delivery as well as fluorescence based sensor for sensing of different pollutants, Metal ions, dyes which are very toxic to environment as well as human being as it pollute mainly water sources can cause health issues. It is very harmful to life of plants, animals and also human being. Detection of these metal Ion using GQDs can help preventing diseases in human and harmful impact on environments.<br/>There is a number of techniques for the synthesis of GQDs using biomass precursors. However most of them are time consuming, costly, harsh reaction condition and includes use of toxic chemicals. Here we approached microplasma method for synthesis of GQDs from different biomass precursors, which is one of the most promising approaches for nanomaterial synthesis due to its simple approaching and stable and low cost. High electron density in microplasma provides non-thermal dissociation of molecular gases to form reactive species such as OH radical, O radical, O₂^- radical. These reactive species in precursor solution interact with chemical species and form GQDs.<br/>Here we report an effective synthesis of tunable GQDs under ambient condition by using microplasma. Here we used different biomass precursor for the synthesis of GQDs, including chitosan, fructose, lignin, citric acid and starch. Tunable fluorescence can be explored by controlling the chemistry of reactions during the synthesis. This method leads to highly crystalline particles with tunable properties and high reproducibility from simple biomass. GQDs synthesized from different biomass shown selectivity to different metal ions due to their surface functional functionalities. This work shows a promising method to synthesis of GQDs with different functionality and not only for metal ion detection but also for many other future applications such as drug delivery, nanomedicines, disease detection and therapy.