The Synthesis Of Carbon Quantum Dot And Its Application In Optical Detection

Carbon quantum dots（CQDs）,as one of the most important nanomaterials,have attracted interests due to its excellent physical and chemical properties including adjustable fluorescence emission wavelength,high optical stability,resistance to bleaching and good biocompatibility.In addition,the synthetic materials were easy available and the route was simple.Therefore,the applications of CQDs in chemical sensing,biosensing,bioimaging,drug delivery,photodynamic therapy,photocatalysis and electrocatalysis have been rapidly developed in recent years.In this paper,one-step hydrothermal method was used to synthesize two fluorescent CQDs（CQDs-1 and CQDs-2）.Fluoremetric and colorimetric dual mode sensing platforms based on CQDs-1 has been developed for the detection of Cu²⁺in aqueous solution.A ratiometric temperature sensor has been established by CQDs-2.The details are as follows:（1）Two fluorescent CQDs were synthesized using one-step hydrothermal method by different precursors.The optical properties,structure and morphology of the synthesized CQDs were characterized.These results showed that the prepared CQDs had good dispersibility,uniform size and strong fluorescence stability.（2）Fluorometric and colorimetric dual mode sensing platform based on CQDs-1 and gold-silver core shell nanoparticles（Au@Ag NPs）had been established for detection trace Cu²⁺ions in aqueous solution.The detection of Cu²⁺was achieved by monitoring changes in the fluorescence of CQDs-1 and the surface plasmon resonance（SPR）absorption of Au@Ag NPs,The dynamic linear range of 0.005-1μM for Cu²⁺detection was realized with Limit-of-detection（LOD）of 4.81 nM for fluorometric measurement and 3.85 nM for colorimetric measurement.Therefore,a label-free and simple dual-mode sensing system was developed for highly selective and sensitive detection of trace Cu²⁺in aqueous samples.（3）Using CQDs-2 and 2,3-diaminophenazine（DAP）,a ratiometric temperature sensor was constructed to detect temperature.O-phenylenediamine（OPD）could produce DAP by under the catalysis of Cu²⁺.This reaction was greatly affected by the temperature.In others words,the more DAP would been generated at high temperature.The fluorescence of CQDs-2 could been quenched by DAP.The fluorescence intensity ratio(F₅₅₀/F₄₅₅)of DAP and CQDs-2 at different temperatures was measured.The F₅₅₀/F₄₅₅ value was exponentially increasing in the range of 20 ^oC-80 ^oC.Thus,in this chapter,a ratiometric sensor based on CQDs-2 and DAP was used to detect the system temperature.