Plasma Nanoengineering of Bioresource-Derived Graphene Quantum Dots as Ultrasensitive Environmental Nanoprobes

Abstract

Environmental contamination and energy shortage are among the most critical global issues that require urgent solutions to ensure sustainable ecological balance. Rapid and ultrasensitive monitoring of water quality against pollutant contaminations using a low-cost, easy-to-operate, and environmentally friendly technology is a promising yet not commonly available solution. Here, we demonstrate the effective use of plasma-converted natural bioresources for environmental monitoring. The energy-efficient microplasmas operated at ambient conditions are used to convert diverse bioresources, including fructose, chitosan, citric acid, lignin, cellulose, and starch, into heteroatom-doped graphene quantum dots (GQDs) with controlled structures and functionalities for applications as fluorescence-based environmental nanoprobes. The simple structure of citric acid enables the production of monodispersed 3.6 nm averaged-size GQDs with excitation-independent emissions, while the saccharides including fructose, chitosan, lignin, cellulose, and starch allow the synthesis of GQDs with excitation-dependent emissions due to broader size distribution. Moreover, the presence of heteroatoms such as N and/or S in the chemical structures of chitosan and lignin coupled with the highly reactive species generated by the plasma facilitates the one-step synthesis of N, S-codoped GQDs, which offer selective detection of toxic environmental contaminants with a low limit of detection of 7.4 nM. Our work provides an insight into the rapid and green fabrication of GQDs with tunable emissions from natural resources in a scalable and sustainable manner, which is expected to generate impact in the environmental safety, energy conversion and storage, nanocatalysis, and nanomedicine fields.

Heteroatom-doped lignin-derived carbon material: performance and application

“…The stronger binding affinity of Cr 6+ with N, B-CQDs could induce considerable energy dissipation and restrain the recombination of excitons, thus leading to a notable reduction in the fluorescence of N, B-CQDs. Kurniawan et al 145 synthesized N–S-doped lignin-derived graphene quantum dots (L-GQDs), which could be used for the selective detection of Hg 2+ in the range of 1–50 μM with the lowest detection limit (LOD) of 68.5 nM. The introduction of N and S in L-GQDs significantly modified their surface charge characteristics, thus promoting massive Hg 2+ adsorption and leading to significant photoluminescence quenching.…”

Advances in Structural Modifications and Properties of Graphene Quantum Dots for Biomedical Applications

“…Some of these methods are described below in detail with examples while emphasizing their advantages as well as limitations. Several methods such as electron beam lithography, chemical oxidation, , hydrothermal, , solvothermal, microwave-assisted, , green-chemistry, synthesis, laser ablation, plasma, chemical vapor deposition, and electrochemical , routes have been employed to synthesize the GQDs. Subsequently, this approach is low cost, uses abundant raw materials, and produces edge-functionalized and water-soluble GQDs.…”

Microflow Synthesis of Fluorescent Carbon Dots for Selective Co2+ Detection

“…The GQDs exhibit selective detection of Cu 2+ , with a low limit of detection (LOD) down to 0.5 μM. Afterward, the microplasma method was extended to the fabrication of N, S-codoped GQDs from diverse bioresources, suggesting they are applicable for real-time monitoring of water environments against pollutants . On this basis, GQD-inorganic nanocomposites were also designed to prepare molecular separation membranes with extremely high separation efficiency .…”

“…Afterward, the microplasma method was extended to the fabrication of N, S-codoped GQDs from diverse bioresources, suggesting they are applicable for real-time monitoring of water environments against pollutants. 12 On this basis, GQDinorganic nanocomposites were also designed to prepare molecular separation membranes with extremely high separation efficiency. 13 In addition to the microplasma technique, continuous microflow synthesis has been regarded as a potential alternative to traditional methods, as it not only provides the system with uniform residence time distribution to address the issue of poor reproducibility of batch reactors but also affords excellent control over the synthesis parameters to obtain uniform products with desired properties.…”