Controllable Preparation Of Regular Bimetallic AgAu Composite Film With Poly (Acrylic Acid) And Their LSPR-enhanced Electrochemical Sensing Properties

Nanostructure metal materials(e.g.,Ag,Au,Cu,etc.)prepared based on self-assembled monolayer colloidal crystal assembly exhibit highly regular and uniform structure.They show the excellent optical and electrical properties and high catalytic activity,and they have important application in catalysis,chemical and biological sensors,photoelectric transformation,and etc.Among metal nanomaterials with local surface plasmon resonance(LSPR)properties,silver(Ag)nanomaterial has excellent plasmon resonance properties,and gold(Au)nanomaterial has become an important choice for sensing performance because of its good chemical stability and biocompatibility.Compared to a single component of nanostructure Au or Ag,bimetallic AgAu composite nanocrystals not only have the advantages of individual Ag and Au,and they show the synergistic effect and the coupling effect between the two kinds of metal particles.Therefore,bimetallic AgAu composite nanocrystals exhibit excellent catalytic activity,the regulated LSPR properties and good chemical stability,and thus they have a wide range of application including sensing,catalysis,medical diagnosis and biomedical imaging and other important fields.Bimetallic AgAu composites with regular nanostructures have the advantages of uniform surface and large specific surface,which can be used as interfacial electrochemical sensing materials with high sensing performance and good stability.At the same time,nanostructures AgAu composites can provide the maximum hot spot surface density that generated from the regular and uniform surface morphology,and they show enhanced electrochemical activity,and adjustable optical sensing performance due to their large surface area and regular crystal structure.In this thesis,the Ag nanoparticles assembled on the surface of colloidal crystal formed AgFON composite film material was prepared by using the interface self-assembly method,using the fluorine-doped tin oxide FTO(Sn O₂:F)coated glass as substrate.The surface structure and LSPR properties of AgAu bimetallic composite film electrode materials prepared by polyacrylic acid(PAA)can be effectively regulated by changing the concentration of HAuCl₄solution.The surface structure and LSPR enhanced electrochemical sensing performance of the prepared FTO-based AgAu composite film electrode material for glucose sensing were explored by cyclic voltammetry(CV)and time-current curve methods.The effect of the surface structure of the composite and the content of Ag and Au on its sensing performance was investigated.This thesis mainly includes the following three parts:(1)The two-dimensional colloidal crystal with regular morphology was obtained through the gas-liquid interface self-assembly technique,using core-shell structure polystyrene@polyacrylic acid(PS@PAA)particles as construction unit,and then Ag nanoparticles with uniform thickness was deposited on its surface by ion sputtering method.Finally,PAA stabilized AgFON composite film was obtained.The electrochemical sensing performance of glucose showed that the PAA stabilized AgFON composite film was more stable than AgFON composite film material.(2)(PAA-AgAu)FON film were obtained by the liquid/solid interface method.The bimetallic AgAu composite structure of(PAA-AgAu)FON film can be regulated by changing the concentration of HAuCl₄(0.1 m M,0.25 m M,0.5 m M and 0.75 m M).The results show that the surface morphology of(PAA-AgAu)FON composite film is directly related to the surface structure and void size of AgAu composite particles.When the concentration of HAuCl₄solution is small,AgAu composite particles are formed on the surface of the AgFON composite film.With the further increase of HAuCl₄concentration,the surface of(PAA-AgAu)FON composite film formed a larger porosity in the"cap zone region".In addition,with the increase of the concentration of HAuCl₄solution,the obtained composite film exhibited the gradually red-shift of LSPR peak,due to the size of AgAu particle and the relative content of Au in the bimetallic composite film.Using the prepared(PAA-AgAu)FON/FTO composite film as the catalytic material,glucose molecules as the analyte.The results of the electrochemical sensing performance of glucose showed that the pore structure of(PAA-AgAu)FON/FTO composite film provides a large specific surface for the electrocatalytic reaction of glucose,and the uniform surface structure greatly improves the sensitivity of glucose sensing.The sensitivity of bimetallic(PAA-AgAu)FON/FTO for glucose detection is 18.47?A/(m M)(the concentration of 0.001?0.5 m M),and the detection limit is as low as 1.0?M.(3)The bimetallic(PAA-AgAu)FON/FTO composite film shows excellent LSPR enhanced sensing performance toward glucose which resulting from the excellent LSPR performance of AgAu composite bimetallic nanocrystals.The pore structure of the AgAu composite particles provides a large specific surface for glucose oxidation reaction,which can significantly improve the sensitivity of glucose sensing.It was found that the relative content of Ag and Au in the composite film material and the composite structure was directly influenced to the enhanced glucose sensing effect of LSPR.The sensitivity of bimetallic(PAA-AgAu)FON/FTO for glucose detection is 48.03?A/m M(the concentration of 0.001?4.0 m M)and 198?A/m M(the concentration of 4.0?8.0 m M).The regular AgAu composite film electrode materials proposed in this study provides an important reference for the assembly and preparation of sensing electrode materials with high sensitivity and stability.They will have important application prospects in the fields of catalysis,chemical and biological sensing.