Synthesis,Characterization And Application Of Ratiometric Fluorescent Carbon Dots

Carbon dots（CDs）,a fluorescent sensing material with particle size less than 10 nm,have been attracting much attention since being accidentally discovered in 2004.the advantages of facile preparation,rapid response,tunable emission,excellent water solubility,and low toxicity enable their increasing applications in fluorescence sensing,bioimaging,anti-counterfeit encryption,environmental agriculture and photocatalysis.In this paper,two kinds of CDs with different performance were synthesized by a one-step hydrothermal method and applied to multiple applications such as ion analysis,handheld detection,and bioimaging based on their properties.1.Handheld detection platform integrating ratiometric fluorescent N,P co-doped carbon dots（N,P-CDs）paper strip,smartphone,and 3D-printed accessory corroborates its efficacy for visual quantitative detection of Mn（Ⅶ）and GSH via a continuous fluorescence color shift.N,P-CDs were synthesized by hydrothermal treatment of 1,8-diaminonaphthalene,phosphoric acid,and formamide.Inspiringly,with increasing Mn（Ⅶ）concentrations,blue emission of N,P-CDs decreases gradually at 445 nm and a ratio rising orange band emerges at 600 nm under 340 nm excitation,which concurrently exhibits continuous fluorescence color variation of blue,purplish blue,purplish pink,pink,to orange.Subsequent addition of GSH renders orange fluorescence of N,P-CDs@Mn（Ⅶ）gradually quench but blue peak slightly enhance,accompanied by the fluorescence color successively returning from orange to blue.The RGB values of the resulting images were precisely defined by a color recognition application within the smartphone,and the R/B values could be employed for Mn（Ⅶ）and GSH quantification with linear ranges of 0-40μM and 0-28μM,respectively,as well as limits of detection of 24.49 n M and 21.41 n M,respectively.It is solicitously anticipated that our research will provide novel insight for the development of effective sensing protocol and the enlargement of practical application prospect.2.Ratiometric dual-emission carbon dots（D-CDs）were satisfactorily synthesized by hydrothermal treatment of aloe and neutral red.Inspiringly,with increasing Hg²⁺concentration,the emission of D-CDs at 616 nm gradually decreases while that at 550 nm shows a ratiometric enhancement.Subsequent addition of GSH restores the fluorescence of D-CDs.Furthermore,increasing p H gives rise to the enhancement of dual emission peaks of D-CDs at 550 nm and 616 nm.More strikingly,as-synthesized D-CDs can be extended for ratiometric quantification of Hg²⁺and GSH as well as monitoring the fluctuation of p H in biological systems.This research is expected to provide new ideas for expanding biosensors and exploring multimodal detection.