Bioresource-Based Graphene Quantum Dots and Their Applications: A Review

Environmental worsening, energy crises, and various other factors have enhanced the demand for facile, cheap, and green approaches for creating emerging materials from bioresources. In recent times, graphene quantum dots (GQDs) are the most developing zero-dimensional nanomaterials owing to exclusive electronic and optical properties. Biomass-derived GQDs have been considered an advanced material and have gained complete attention because of their green, inexpensive, nonsustainable, environmental-friendly, and recyclable nature. This review elucidates the current challenges and the use of bioprecursors (e.g., rice husk, plant leaves, honey, coffee) and the methodologies (top-down and bottom-up) of their conversion into ecofriendly GQDs. Biomass resources are converted into ecofriendly GQDs and a facile, low-cost, scalable synthesis. Biomass-derived GQDs are in great demand due to attractive properties like large surface area, low toxicity, and good biocompatibility. Various parameters like absorption, surface and edge states, and quantum confinement affecting the physical, chemical, and electrochemical properties of GQDs are discussed. This review also focuses further on the result of heteroatom doping, pH, and solvent on the photoluminescence (PL) emission of GQDs. The optical and electrochemical sensors based on biomass-derived GQDs are explored in detail. Biomass-derived GQDs have tremendous performance in the biomedical field and energy applications due to their very low toxicity and biocompatibility. This review addresses the future approaches and possible research directions in biomass-derived GQDs. GQDs display minimal cytotoxic reactivity, superior biocompatibility, and chemical insensitivity. To enhance the optoelectronic and physicochemical characteristics of GQDs, their properties can be tuned via surface/edge functionalization or doping. Monitoring the concentrations of pollution gases severely harming the biosphere requires developing more precise and sensitive sensors. Doped GQDs can significantly increase their capacity to adsorb. The reliable gas sensors based on doped GQDs could be a viable replacement for the present sensors available in the market.