Green synthesis of white light emitting carbon quantum dots: Fabrication of white fluorescent film and optical sensor applications

In this work, we have reported on the facile synthesis of white light-emitting carbon quantum dots (CQD) from corncob by hydrothermal method. This CQD has a broad emission from 380 nm to 650 nm with high photoluminescence intensity even after three months of shelf-life and stable at variable pH conditions. The presence of Si and N impurities in the biomass gives a greater advantage in producing white light emission with high quantum yield (54%) and enhanced lifetime at ambient conditions. The CQD is highly sensitive towards DNA, paracetamol, Pb2+, Cu2+, Fe3+, and Cr3+ fluorescence sensing and signifies its application as a multi-modal fluorescence sensor. The results of optical sensitivity calculated from the linear range of 1-10 ng/mL, 0.100.30 mg/mL, 2.5446 ng/mL, 0.0694 mg/mL, 0.3103-1.5515 mu M/mL, 0.4299-4.7293 mu M/mL, 1.3010 mu M/mL and 0.05-2.5 mu M/mL. The limit of detection is 2.5446 ng/mL, 0.0694 mg/mL, 0.8641 mu M/mL, 1.2454 mu M/mL, 1.3010 mu M/m, 0.8550 mu M/mL and 2.8562 mu M/mL, respectively. And also, the relative standard deviation values of 2.30%, 4.46%, 1.79%, 1.84%, 0.26%, 1.23% and 0.35% are evidences its possibility of development towards potential optical sensor applications. Flexible white light-emitting sheets were fabricated from the CQD, illuminates uniform brightness, and has good color reproducibility and higher stability under various UV light excitation.

Automated summary

This study demonstrates the facile synthesis of white light-emitting carbon quantum dots from corncob using a hydrothermal method, showing high photoluminescence intensity and stability over time. The presence of Si and N impurities in the biomass contributes to the high quantum yield and enhanced lifetime of the quantum dots. These carbon quantum dots exhibit high sensitivity towards various substances in fluorescence sensing, with potential applications in optical sensor development. Additionally, flexible white light-emitting sheets fabricated from the carbon quantum dots display uniform brightness, good color reproducibility, and increased stability under UV light excitation.