Construction Of Sensing Methods For Metal Ions And Ascorbic Acid Based On Gold Nanomaterials

Gold nanoparticles(Au NPs)are one of the materials that have been discovered and applied since ancient times.In modern times,gold nanoclusters(Au NCs)with smaller particle size have also been widely studied and developed.These gold nanomaterials have been widely used in chemical detection,biomedicine and other related fields because of their excellent optical stability,low biological toxicity and easy to control for size.In this thesis the“ON-OFF-ON”and“ON-OFF”systems were constructed for the detection of Fe³⁺,ascorbic acid(AA)and Hg²⁺based on the interaction between related gold nanomaterials and analytes.There are two parts in this thesis:1.Detection of Fe³⁺and ascorbic acid based on ratio fluorescence of glutathione gold nanoclustersIn this work,glutathion(GSH)-Au NCs with red fluorescence was synthesized from GSH and chloroauric acid without adding reductant,The prepared Au NCs were used for the high-efficiency detection of Fe³⁺and AA.Au NCs show red emission with two fluorescence peaks at 425 and 585 nm,respectively.Firstly,the peak at 585 nm can be quenched and the peak at 425 nm can be enhanced in the presence of Fe³⁺.The ratio of the fluorescence intensity for 425 and 585 nm(F₄₂₅/F₅₈₅)was enhanced with the increase of Fe³⁺concentration.There was a linear response between the value of F₄₂₅/F₅₈₅ and the concentration of Fe³⁺.The ratio fluorescence of Au NCs can be successfully used for the detection of Fe³⁺rather than any other metal ions.There was a linear response between the value of F₄₂₅/F₅₈₅and the concentration of Fe³⁺in the range of 0.75-125?M with a limit of determination at 227 n M.Secondly,the fluorescence of Au NCs at 585 nm quenched by Fe³⁺can be recovered by the addition of AA.The enhanced fluorescence intensity of Au NCs at 585 nm was proportional with the concentration of AA.And then the system of Au NCs-Fe³⁺can be employed for the determination of AA.The possible mechanism is that Fe³⁺can induce the aggregation of Au NCs,and AA can reduce Fe³⁺.The proposed method has been successfully applied to the determination of Fe³⁺in water and serum samples,as well as the determination of AA in tablets.2.Colorimetry determination of Hg²⁺using gold nanoparticles with N-methylpyrrolidone as reducing agentIn this experiment,a gold nanoparticle colorimetric probe with direct response to Hg²⁺was developed,using N-methyl-pyrrolidone and tetrachloroauric acid as precursors.After high temperature hydrolysis,N-methyl-pyrrolidone shows good reducibility,and can be used as a stabilizer to synthesize gold nanoparticles.The gold nanoparticles have a good characteristic peak and show wine red color.It can be found that Hg²⁺can induce the aggregation of gold nanoparticles,which makes the absorbance of gold nanoparticles increase at 700 nm,and the solution color also changes to blue black.This method shows good selectivity and can be used to detect Hg²⁺in environmental water samples.It is a feasible tool for detecting Hg²⁺and has great significance in the research of building chemical and biosensors.