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An improvement of solid-state fluorescence from a luminous nanocomposite made from corn-starch-based bioplastic by adding intentionally Cu-doped carbon quantum dots (CQDs) has been reported. An affordable, environmentally sustainable, one-step hydrothermal technique was employed to synthesize CQDs from Brassica juncea flower extract. The morphological, structural, and physicochemical characteristics of the material were investigated. The quasi-circular shaped CQDs have been found to have a size distribution of 2–5 nm, to have yellow-greenish fluorescence upon UV stimulation, to have excellent photostability, and to be highly water soluble, with a quantum yield of up to 18.4%. Interestingly, the fluorescence spectra of intentionally Cu-doped CQDs (hereafter N, Ca, Cu-doped CQDs) were found to be brighter after 280 nm illumination than unintentional one. Furthermore, as a solid-phase dispersion matrix of CQDs, the environmentally benign and biodegradable bioplastic is appealing. As a result, this work demonstrated the effect of Cu-doping on solid-state fluorescence in the down-conversion of UVC tubes via a composite constructed by inserting CQDs into the solid-state matrix of corn-starch-based bioplastic nanocomposite, which demonstrated vivid greenish-yellow emission in the electroluminescent spectra with CIE chromatic coordinates (0.33, 0.58 vs. 0.31, 0.67). [ABSTRACT FROM AUTHOR]

Carbon quantum dots (CQDs)-based composite as a luminescent down-conversion materials are gaining importance nowadays because of many favorable factors including stable fluorescence, ease of functionalization, tuning of emission in visible range etc. In this work, we report an economical, sustainable and green synthesis of CQDs derived from mustard (Brassica juncea) flower extract. The as-synthesized CQDs were unintentionally doped with nitrogen and calcium without the inclusion of any doping element precursors. However, phosphorus was intentionally doped to improve the luminescent characteristics of as-synthesized CQDs. The morphological, structural, and physicochemical properties of P-doped CQDs were examined. The quasi-circular or polygonal-shaped CQDs, with an average diameter of 3.4 nm, emerged to produce yellow-greenish fluorescence upon UV stimulation, demonstrate outstanding photostability, and had a quantum yield of up to 18.2%. Furthermore, the ecologically friendly and biodegradable bioplastic is attractive as a solid phase dispersion matrix of CQDs. Hence, this work revealed the effect of phosphorus doping on solid-state fluorescence in the down-conversion of LEDs and UV tubes by producing a composite constructed through inserting CQDs into the solid-state matrix of corn-starch-based bioplastic. [Display omitted] • Effect of intentional P-doped in N,Ca-doped CQDs@bioplastic composite is reported. • Intentional P-doped CQDs were synthesized from Brassica juncea flower extract. • Down-conversion of LEDs and UV tubes have been demonstrated. • Influence of pH on fluorescence properties have also been investigated. [ABSTRACT FROM AUTHOR]