Synthesis Of Fluorescent Carbon Quantum Dots And Its Application In Environmental Analysis

Fluorescent carbon nanomaterials,especially carbon quantum dots（CQDs）,have inspired growing interest of scientific community,due to their extraordinary properties,including excellent optical properties and high light stability,good dispersion and biocompatibility,low toxicity and abundant active sites.Studies have shown that heteroatom doping or surface functionalization can fill surface defects,stabilize fluorescence properties,increase active sites and broaden the range of applications.In recent years,the use of CQDs as fluorescent probes for highly selective detection of trace metal ions directly or as visible light catalysts directly or in combination with other semiconductor photocatalysts to improve photocatalytic activity has become more and more popular.This paper prepares novel CQDs by three kinds of modification including nitrogen-doped carbon dots（N-CDs）,amino-functionalized carbon dots（PEI-CQDs）and carbon-semiconductor photocatalyst composites（BiOI/CQDs）.The properties of the novel nanomaterials were studied and applied in the field of environmental analysis.The specific research contents are as follows:（1）Nitrogen-doped carbon dots（N-CDs）were successfully synthesized by one-pot hydrothermal method using ammonia triacetic acid（NTA）as a raw material.Here,NTA was used as both a carbon source and a nitrogen source,and no other reagents were needed.A novel sensing platform for detecting Fe³⁺ions was constructed using the obtained N-CDs.We proposed and confirmed the mechanism of Fe³⁺quenching the fluorescence of N-CDs and attributed its quenching behavior to the formation of iron complexes.（2）The developing of the method of green synthetic carbon quantum dots with carambola as carbon source overcomes the shortcomings of using expensive and toxic organic chemical reagents as raw materials in the previous reports.The precursors are widely available,green and non-toxic,cheap and easy to obtain.The obtained carbon quantum dots exhibit a spherical shape with an average size of around 3.2 nm and show a good dispersibility and water solubility.PEI-CQDs can be applied to detect Cu²⁺in water with high selectivity and sensitivity under weakly acidic conditions.（3）A novel BiOI/CQDs nanocomposite was prepared by a simple hydrothermal method.The BiOI nanosheets were modified by the PEI-CQDs prepared in the previous chapter.The photocatalytic activity of BiOI/CQDs composites was studied using Rhodamine B as a pollutant.Through modifying by CQDs,the photocatalytic activity of BiOI was significantly enhanced.And BiOI/CQDs-1%exhibits the best photocatalytic activity,which was 8.9 times that of pure BiOI.