Synthesis of carbon quantum dots using unutilized low-grade lignite coal

Area of Science:

• Materials Science
• Nanotechnology
• Environmental Science

Background:

• Nigeria possesses large unutilized coal deposits, posing environmental and economic challenges.
• Resource recovery from low-grade coal offers sustainable solutions for nanomaterial synthesis.
• Innovative reuse of local resources can drive economic revitalization and environmental management.

Purpose of the Study:

• To synthesize carbon quantum dots (CQDs) from lignite coal sourced in Enugu, Nigeria.
• To characterize the structural, elemental, and optical properties of the synthesized CQDs.
• To evaluate the potential industrial applications of coal-derived CQDs.

Main Methods:

• One-step oxidation process for CQD synthesis from lignite coal.
• Elemental analysis using EDX and XPS.
• Characterization of optical properties (fluorescence, UV-Vis absorption) and structural properties (XRD, nitrogen adsorption).

Main Results:

• CQDs composed of over 90% carbon with sulfur, silicon, nitrogen, and oxygen dopants were synthesized.
• CQDs exhibited tunable optical properties with band gaps of 2.61 eV (direct) and 2.68 eV (indirect), and UV-Vis absorption maximum around 400 nm.
• Characterization revealed an amorphous structure (68%), crystallite size of 0.650 nm, quantum confinement effects, and microporous/mesoporous structures.

Conclusions:

• Coal-derived CQDs possess moderate surface area, multi-elemental doping, and tunable optical properties.
• These CQDs demonstrate significant potential for industrial applications in environmental remediation, catalysis, optoelectronics, and biomedical imaging.
• This research promotes sustainable nanomaterial production and economic revitalization of Nigeria's coal sector.