Research On A Novel Method For Detecting Copper And Mercury In Food Based On Shape And Catalytic Activity Controlled Concave Gold-Silver Nanoparticles

Food safety is a major concern,and food pollution is one of the main reasons for it.Among common food pollutants,heavy metals pose a serious threat to food safety.With the development of detection technology,heavy metal elements are usually detected by atomic absorption spectroscopy.However,there are still drawbacks such as complex instrument operation and high analysis cost.Therefore,the development of simple and fast detection methods is particularly necessary.In recent years,metal nanoparticles have been widely used in food testing due to good biocompatibility and unique optical and catalytic properties.This thesis achieves the regulation of morphology and catalytic activity through regrowth of concave gold nanocubes(CGNs)and synthesizes a batch of gold-silver nanoparticles with high catalytic activity.Based on the impact of heavy metal ions on catalytic activity;a rapid detection method for Hg2+ and Cu2+ using colorimetry/fluorescence sensing is developed.The specific research content is as follows:(1)The morphology and catalytic activity of CGNs were controlled through regrowth,and a colorimetric sensing detection method for Hg2+was developed based on the inhibition of gold nanoparticles(D-2)catalyzed borohy dride reduction of p-nitrophenol(4-NP)by Hg2+.Under alkaline conditions,the morphology of CGNs was controlled by adjusting the amount of growth solution(Au+/H2O2 solution),and gold nanoparticles with various morphologies such as concave,star-shaped,and multi-branched were synthesized.The catalytic activity of the nanomaterial was evaluated using the catalytic borohydride reduction of 4-NP,and the worm-like D-2 nanoparticles had the best catalytic activity.The nanoparticles were characterized and analyzed by transmission electron microscopy,high-resolution transmission electron microscopy,and X-ray diffraction,and the reasons for the high catalytic activity of D-2 gold nanoparticles were preliminarily analyzed and discussed.The addition of Hg2+ decreased the reduction rate of 4-NP,and a quantitative detection of Hg2+was achieved based on this·The concentration of Hg2+ in the range of 0-58 nM had a good linear relationship with the reduction time of 4-NP,with a linear equation of ΔA=0.074CHg(Ⅱ)+3.513(R2=0.995),and the detection limit(LOD)was 2 nM.The method had high selectivity for Hg2+ and achieved efficient quantitative detection of Hg2+ in drinking water.(2)A series of Au-Ag alloy nanoparticles were prepared by regrowth of CGNs in a silver solution,and a fluorescence sensing detection method for Cu2+ was developed by the inhibition of Cu2+ on the catalytic oxidation of o-phenylenediamine(OPD)by Au-Ag nanoparticles(N-0.5)with H2O2.The morphology,catalytic activity,and composition of Au-Ag nanoparticles were controlled by adding different amounts of silver growth solution(Ag+/AA solution)to the CGNs solution,and the nanoparticles were characterized and analyzed by transmission electron microscopy.The catalytic activity of these Au-Ag nanoparticles was evaluated by the oxidation of OPD,and the N-0.5 nanoparticles had the best catalytic activity.The addition of Cu2+to the OPD oxidation reaction inhibited the fluorescence of the reaction solution,and a quantitative detection of Cu2+ was achieved based on this.The concentration of Cu2+in the range of 0.2-40 μM had a linear relationship with the fluorescence intensity of OPD,with a linear equation of ΔF/F0=0.0197CCu(Ⅱ)+0.0446(R2=0.992),LOD is 0.08 μM.The method was applied to the detection of Cu2+in actual water samples and achieved accurate and rapid quantitative detection.(3)The morphology and catalytic activity of CGNs were controlled by regrowth under the influence of iodide ions,and a colorimetric and fluorescence dual-signal sensing detection method for Hg2+ was developed by using the inhibition of gold nanoparticles(Y-0.125)catalyzed borohydride reduction of rhodamine B(RhB)by Hg2+.The morphology and catalytic activity of CGNs were controlled by adjusting the amount of Au3+/AA/I-solution,and the morphology of CGNs changed from concave to square to spherical.The catalytic activity of the nanoparticles synthesized during the control process was evaluated by using them for the catalytic borohydride reduction of RhB,and the Y-0.125 nanoparticles had the best catalytic activity.When Hg2+ was added to the reduction system,it formed a gold-mercury alloy with gold nanoparticles and accelerated the reduction of RhB.Based on this,a quantitative detection of Hg2+was achieved.The concentration of Hg2+ in the range of 0.5-10 μM had a good linear relationship with the absorbance or fluorescence intensity of RhB,with linear equations of ΔA=0.234CHg(Ⅱ)-0.0685(R2=0.991)for the colorimetric method andΔF/F0=0.555CHg(Ⅱ)+0.0685(R2=0.992)for the fluorescence method,and the LODs were 0.2 μM and 0.12 μM,respectively.The method had a recovery rate of 98.8-99.6%and a relative standard deviation(RSD)of no more than 1.5%in the actual sample detection.