Application Research Of Colorimetric Analysis Based On Gold,Gold Platinum Nanoparticles In Detection Of Sulfur-containing Substances

As harmful substances,thiocyanate(SCN~-)and thiourea(TU)are widely used in many industries and fields,such as agriculture,medicine,chemical industry,dyes and photography et al.Due to their wide range of applications,residues of these harmful substances may exist in wastewater,environmental water and biological metabolism.For the environment and the human body,excessive thiocyanate and thiourea will cause very serious consequences to organisms.Therefore,it is very important to develop simple and convenient sensors for detecting thiocyanate and thiourea.The first chapter gives an overview of SCN~-and thiourea.It mainly introduces the detection significance of two substances and the current detection methods,and summarizes the advantages and disadvantages of these methods.The second chapter based on the characteristics of aggregation and anti-aggregation for gold nanoparticles(AuNPs),and proposes a colorimetric sensor that uses 2-aminopyridine(2-AP)to detect SCN~-through an anti-aggregation mechanism.Due to the electrostatic repulsion of citrate on the surface of AuNPs,the synthesized AuNPs were in a dispersed state.The UV-Vis absorption peak was at 520nm,and the solution color was wine red.After the aggregating agent 2-AP was added,the original electrostatic repulsion force was broken by 2-AP and agglomeration occurred.The bathochromic-shift UV-Vis absorption peak of the aggregated AuNPs was found at 675 nm,and the solution color was changed to blue.When SCN~-presents in the solution,SCN~-protects the gold nanoparticles from the influence of2-AP and in a dispersed state.Based on this phenomenon,a colorimetric sensor for detecting SCN~-based on the anti-aggregation of AuNPs was developed.The experiment explored that the sensor can quantitatively detect SCN~-,and had excellent selectivity and anti-interference ability.In actual samples determinations,it had huge potential application values.In the third chapter,after studying the properties of AuNPs,Pt atoms were synthesized on the surface to increase the catalytic performance.Gold/platinum nanoparticles(Au@PtNPs)had very excellent peroxidase-like activity,which can accelerate the decomposition of hydrogen peroxide and turn the colorless 3,3’,5,5’-Tetramethylbenzidine dihydrochloride(TMB)into the blue oxidation state TMB(oxTMB).When thiourea molecules presents in the solution,the lone electron pair of the S atom can occupy the empty orbital of the Au atom,causing TU to be easily adsorbed on the surface of Au@PtNPs.Therefore,the addition of TU would cause the aggregation of Au@PtNPs.Due to the influence of the aggregation Au@PtNPs and the occupancy of TU molecules,the peroxidase-like activity of Au@PtNPs decreased sharply,and the colorless substrate TMB would not undergo color changes.Based on this change,a colorimetric sensor for detecting TU was proposed.Experiments showed that the colorimetric sensor has a wide detection range,good selectivity and strong anti-interference ability.In actual water samples detections,it can also show good detection capabilities.