The role of solvents on the optical properties of carbon quantum dots synthesized via solvothermal/hydrothermal method

Abstract

This research explores how different solvents affect the synthesis and optical properties of carbon quantum dots (CQDs) using a solvothermal method. Previous studies on emission-related applications have emphasized the optical and electrical properties, but there has been little focus on how the choice of solvent affects electrocatalytic applications. The findings demonstrate that the choice of solvent significantly influences the crystallinity, particle size, functional groups, and both absorption and photoluminescence spectra, leading to variations in the band gaps. CQDs-DI had the smallest particles at 3.6 ± 0.6 nm with a polycrystalline structure, CQDs-Glycerol had moderate-sized particles at 6.7 ± 0.6 nm with an amorphous structure, while CQDs-DMF produced the largest particles at 15.1 ± 2.0 nm. FTIR and UV-Vis tests confirmed different functional groups, with CQDs-DMF showing amide groups. The presence of amide groups in CQDs-DMF led to hydrophobic properties, supported by an additional peak in the UV-Vis spectrum at 450 nm, caused by the surface state of C=N. Additionally, TRPL characterization showed that CQDs-Glycerol had the fastest lifetime decay, at 2.3 ns, other than CQDs-DI at 4.73 ns and CQDs-DMF at 5.58 ns. This study demonstrate that DI and glycerol solvent are efficient solvents for synthesizing CQDs as electrocatalysts due to their hydrophilic nature and crystallinity.