Synthesis of Graphene Quantum Dots by a Simple Hydrothermal Route Using Graphite Recycled from Spent Li-Ion Batteries

Abstract

Graphene quantum dots (GQDs) are nanosized systems that combine beneficial properties typical of graphenic materials (such as chemical stability, biocompatibility and ease of preparation from low-cost precursors) with remarkable photoluminescent features. GQDs are well-known for their low cytotoxicity and for being promising candidates in applications, such as bioimaging, optoelectronics, electrochemical energy storage, sensing and catalysis, among others. This work describes a simple and low-cost synthesis of GQDs, starting from an alcoholic aqueous suspension of graphene oxide (GO) and using a hydrothermal route. GO was prepared using graphite recycled from spent Li-ion batteries, via a modified Hummers method. The GO suspension was submitted to hydrothermal treatments at different temperatures using a homemade hydrothermal reactor that allows the control of the heating program and the assessment of the internal pressure generated in the reaction. The synthesized GQDs exhibited bright blue/green luminescence under UV light; showing the success of the chosen route and opening the way for future applications of these materials in the field of optoelectronic devices.

Novel Nanobiocatalyst Constituted by Lipase from Burkholderia cepacia Immobilized on Graphene Oxide Derived from Grape Seed Biochar

“…Graphene oxide (GO) can be produced from graphite by the Hummers method [8]. Graphene oxide showed great potential for application in different industrial sectors due to its properties such as high specific surface area, superior chemical resistance, good electrical and thermal conductivity, flexibility, and impermeability [9]. Among these applications, sensors, transparent conductive films, and enzymatic immobilization are included [10].…”