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, Pb 2+ , Cu 2+ , Fe 3+ , and Cr 3+ 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, 0.10‐0.30 mg/mL, 2.5446 ng/mL, 0.0694 mg/mL, 0.3103–1.5515 μM/mL, 0.4299–4.7293 μM/mL, 1.3010 μM/mL and 0.05–2.5 μM/mL. The limit of detection is 2.5446 ng/mL, 0.0694 mg/mL, 0.8641 μM/mL, 1.2454 μM/mL, 1.3010 μM/m, 0.8550 μM/mL and 2.8562 μM/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. • Carbon quantum dots (CQD) have been synthesized from corn cob biomass by hydrothermal method. • Biomass impurities of Si and N in CQD is advantageous in producing white light emission. • The CQD has higher quantum yield of 54% even at the neutral pH conditions. • Highly sensitive multi-fluorescence sensor detection of DNA, paracetamol, Pb 2+ , Cu 2+ , Fe 3+ , and Cr 3+ . • Flexible white light emitting sheets under UV excitation is fabricated using CQD.