Peanut shell carbon quantum dots modified with citric acid: amplifying visual detection of fluorescence sensitivity for Cu²⁺

Carbon quantum dots are widely investigated due to their photoluminescence properties. Here, we report a green synthesis of carbon quantum dots to increase the photoluminescence properties of peanut shells through pyrolysis. In this synthesis process, citric acid is pyrolyzed with the peanut shells to obtain the highly fluorescent PSCA-CQD. This synthesis method is highly cost-effective, simple, environment-friendly, and highly efficient. The prepared PSCA-CQD has improved photoluminescence, higher quantum yield, and good reproducibility. Further investigation has suggested that PSCA-CQDs are highly sensitive for visual Cu2+ ion detection.