Synthesis And Application Of Fluorescent Carbon Dots With Polymer As Carbon Source

Fluorescent carbon dots?CDs?have drawn great attention in recent years due to their excellent water dispersibility,chemical and photo stability,the low cost of fabrication and good biocompatibility.These superior properties make them to be promising candidates in chemical sensing,biosensors,catalysis,and photovoltaic devices.This paper successfully used polyethyleneimine?PEI?as a carbon source for the synthesis of fluorescent carbon dots.The main contents are listed as follows:?1?A simple one-step hydrothermal synthesis of fluorescent carbon dots is performed using PEI with only three elements of C,N,and H as the carbon source.Both the N-doping and the amino-functionalization of CDs were accomplished simultaneously.The CDs exhibited strong blue fluorescence and good dispersion in aqueous solution.A lot of free amino of the surface of CDs simplified the subsequent modifications.Through an amide reaction,glutathione-functional CDs were successfully applied to selective detection of Co²⁺.?2?Carbon dots/gold nanoclusters?CDs/Au NCs?nanohybrid based on dual-signal ratiometric fluorescent probe for sensitive and selective sensing of Ag⁺and L-cysteine?Cys?had been established.Fluorescence have been widely used for visual detection,however,single-color fluorescence was inconvenient for people to distinguish color change.The PEI as a carbon source to synthesize fluorescent CDs with blue fluorescence served as a reference signal and Au NCs with orange fluorescence as a reporter,by adjusting the proportion of the CDs and Au NCs,nanohybrid emitted a middle color-gray orange via a single excitation wavelength.Ag⁺enhanced the orange of Au NCs,but Cys could quench it completely with the high affinity of the coordination interaction between Cys and Ag⁺,while the blue fluorescence of CDs was not affected.Therefore,the fluorescence of nanohybrid showed gray orange to light orange for determination of Ag⁺,and light orange to blue for determination of Cys.Both proposed methods had high selectivity.Moreover,visual detection was successfully carried out,which showed a more distinguishable color difference than that in aqueous solution.It will be applied to real-time online visual fluorescence detection for Ag⁺and Cys in the future.?3?Based on the second chapter the amino rich carbon dots synthesized by hydrothermal method.It can directly synthesize gold silver nanoparticles?AuAg NPs?by simply mixing with chloro auric acid solution for visual detection of Cys This method is simple and quick,without using any additional function of reducing agent,stabilizer and external energy.At the same time,the synthesized AuAg NPs had good stability and showed good detection performance for cysteine.It can be observed by the naked eye thatwith the increase of Cys concentration,the solution from yellowish to reddish brown is finally colorless.This phenomenon provides a better direction for subsequent visual detection.