Rare-earth free solid-state fluorescent carbon-quantum dots: Multi-color emission and its application as optical dual-mode sensor

Abstract

Proposing a straightforward technique for producing multi-color carbon quantum dots (CQDs) and investigating how luminescence can be tuned and improved is appealing and encouraging. The production of white light-emitting nanophosphors is crucial for the development of future display and lighting technologies, and their outstanding luminescent qualities provide considerable potential in sensing applications. The rare-earth ions have been used often as dopants to produce semiconducting nanophosphors, the restricted unavailability of rare-earth elements in our planet necessitates to look for more appropriate substitutes. Herein, we present the fabrication of CQDs co-doped with Cu and Mn (Cu/Mn:CQDs) transition metal ions that exhibit strong white light emission with the Commission Internationale de L′Eclairage (CIE) chromaticity coordinates (0.36, 0.30), which has a high color rendering index (CRI) value of 89. The as-produced Cu/Mn:CQDs have a quantum yield of 28.35 % and are employed as a fluorescent sensor for Fe3+ and ascorbic acid (AA) detection through "on-off-on" sequential mode. The fluorescence of Cu/Mn:CQDs can be greatly suppressed by Fe3+ ions via static quenching and then recovered by adding AA, as AA causes Fe3+ to be reduced to Fe2+. This sensor demonstrated high selectivity and sensitivity towards Fe3+ and AA with detection limits of 16 and 46 nM, respectively. Most importantly, the as-proposed fluorescence sensing system are successful for detecting Fe3+ and AA in real water samples with satisfactory results. Furthermore, an IMPLICATION logic gate is built based on the unique properties of Cu/Mn:CQDs nanohybrids, indicating new prospects for application in single and multiple biological sensing. This research could open the path for the development of low cost, high performance and environment-friendly multicolor phosphor for optoelectronic devices and sensing applications.