Syntheses Of Fluorescence Quantum Dots And Their Applications In Detection Of Ferric Ions

In recent years,the control and management of heavy metal pollutions has become a worldwide resrarch priority for environment security and ecological environment sustainaility.The heavy metals are widely distributed in atmosphere,soil and water.In water,they are mainly in the form of cations.There are many kinds of heavy metal ions pollutions in water,and ferric ion(Fe³⁺)is one of them.As an essential element for life,Fe³⁺plays an indispensable role in many physiological processes in the human body.However,when the content deviates from the normal value in the human body,it will also induce diseases such as cancer,hemochromatosis,anemia and so on.Therefore,it is of practical significance to achieve efficient,accurate and sensitive detection of Fe³⁺has great practical significance.Graphene quantum dots?GQDs?and black phosphorus quantum dots?BPQDs?are two new types of fluorescence nanoprobe materials,which have many advantages,such as good water solubility,good biocompatibility,anti-photobleaching and so on,thus have attracted extensive attention from research fields of fluorescence sensing,bioimaging,and biomarkers in recent years.In this paper,based on simple and facile methods,we explored the preparation of GQDs and BPQDs,respectively.And through the introduction of surface functional groups,we realized the specificity detection of two kinds of fluorescent probe materials to Fe³⁺.The main research contents of this thesis are as follows:In the first part of content,we present a facile preparation of single-layered GQDs?sl-GQDs?through a one-step hydrothermal route by using citric acid and?-cyclodextrin?CD?as precursors.The as-prepared sl-GQDs emits green fluorescence excited by UV light and with fiuorescence quantum yield of 5.34%.Due to the presence of CD molecules,the usually occurred irreversible agglomerate between the graphene sheets was effectively restrained,thus lead to the formation of sl-GQDs,in which the CD molecules were decorated homogeneously on its surface.Meanwhile,attributable to the presence of abundant hydroxyl,carboxyl and carbonyl groups on its surface,the as-prepared sl-GQDs show high affinity to Fe³⁺and can lead to the formation of metal complex structures.Therefore,in this part of content,the specificity detection of Fe³⁺was achieved by fluorescence quenching of sl-GQDs in the presence of Fe³⁺.The detection limit was about 0.26?M.The fluorescence signal of the probe has little change in the presence of more than ten kinds of interfering ions,such as Al³⁺,Ca²⁺,Co²⁺,Cr³⁺,Cu²⁺,Fe²⁺,K⁺,Mg²⁺,Mn²⁺,Na⁺,Ni²⁺,Zn²⁺and so on,showing good specificity detection for Fe³⁺.In addition,the fluorescence sensor based on sl-GQDs has also been successfully applied to the specificity detection of Fe³⁺in the tap water samples,with satisfied recoveries of93.8%-101.5%.In the second part of content,we synthesized CD modified GQDs/BPQDs complex?CD-GQDs/BPQDs?by using flake black phosphorus?BP?powder as the precursor,the DMF solvent as the exfoliated solvent and CD as the auxiliary molecules through one-step solvothermal method under the protection of Argon.The as-prepared CD-GQDs/BPQDs emits blue fluorescence excited by UV light and with fiuorescence quantum yield of 12.60%.Due to the auxiliary dispersibility of CD and the exfoliate ability of DMF solvent,the as-prepared CD-GQDs/BPQDs form a"sandwich"structure composed of single-layer GQDs,single-layer BPQDs and CD molecular modification layers.Among them,GQDs as the base material of BPQDs can not only effectively prevent BPQDs from being oxidized by water and oxygen in the air,improve the stability of BPQDs,and it can also effectively inhibit the?-?stacking between layers of BPQDs.Attributable to the presence of CD molecules,the?-?stacking between graphene and BP material layers were effectively inhibited.And CD molecules contain abundant hydroxyl,carboxyl and carbonyl groups on its surface,which ensure the specific fluorescence recognition of Fe³⁺.The detection limit was about 0.19?M.The fluorescence signal of the probe has little change in the presence of more than ten kinds of interfering ions,such as Al³⁺,Bi³⁺,Hg²⁺,Cr³⁺,Cu²⁺,Fe²⁺,K⁺,Mg²⁺,Mn²⁺,Pb²⁺,Ni²⁺,Zn²⁺and so on,showing good specificity detection for Fe³⁺.Furthermore,the present fluorescence sensor based on CD-GQDs/BPQDs had also been successfully applied in the detection of Fe³⁺in the tap water samples,with satisfied recoveries of93.5%-107.1%.