One-step synthesis of fluorescence-enhanced carbon dots for Fe (III) on-off-on sensing, bioimaging and light-emitting devices.

Carbon quantum dots (CDs), as one of the most potential fluorescent sensing materials, have attracted lots of attention in recent years. However, the low quantum yields, complicated separation and purification procedures have limited its application and large-scale production. In this paper, a facile and universal method was successfully developed to synthesize CDs-silica (SiO) spheres composites (CS composites), which not only demonstrates 10-fold fluorescence enhancement compared with single CDs but also enables the purification with a simple centrifugation step. Meanwhile, fabricated composites also presented superior photoluminescence (PL) stability and high PL intensity, even in some tough environments such as acid/alkali aqueous solution, high/low temperature, and high ion concentration aqueous solution. This simple, fast, low-cost, and efficient synthesis method would potentially expand the application of CDs for clinical analysis, optical sensing (ferric ion (Fe) and pyrophosphate), bioimaging and light-emitting diodes (LEDs).