Plasma-Bioresource-Derived Multifunctional Porous NGQD/AuNP Nanocomposites for Water Monitoring and Purification

Metal-organic composites with controlled structures and properties are actively pursued for diverse applications such as optoelectronics, sensing, imaging, drug delivery, cancer therapy, energy generation and storage, environmental monitoring and purification, and many others. Among those applications, stable 3D architectural multifunctional metal-organic composites with high efficacy in water treatment are highly desired for next-generation clean and sustainable technologies. Current synthesis methods of metal-organic composites face major problems including long preparation time, laborious step, toxic chemicals, harsh solvent, high temperature, uncontrolled structures and properties.<br/><br/>Here we report rapid and environment-friendly plasma engineering of lightweight and porous 3D NGQD/AuNP composites from chitosan using non-thermal microplasmas at ambient conditions without toxic chemicals and high temperature treatment. The highly reactive species generated by the plasma are used to simultaneously synthesize both NGQDs and AuNPs from chitosan containing gold salt. Moreover, synergistic effect of the NGQDs and AuNPs as the nanocross-linkers can accelerate the cross-linking of chitosan to form a 3D porous composite without the need of toxic chemicals and high-temperature treatment. The engineered composites exhibit multifunctional properties including stable solid-state PL emission, tunable surface functionalities, catalytic ability, high porosity, and mechanical robustness, having potential for water treatment including selective PL detection of Hg²⁺, remarkable adsorption of remazol brilliant blue R (RBBR), and catalytic reduction of 4-nitrophenol (4-NP). Furthermore, our method can also yield colloidal NGQDs used for Cr(VI) detection in solution, ranging from 1 to 100 μM with a 61 nM limit of detection (LoD). Our work provides not only a general method to engineer organic-metal composites with defined structures and properties, but also a new insight into their rational design for emerging applications.