Nanoporous Gold Used In The Electrochemical Study Of Glucose Oxidation And Detection Of 4 - Nitrophenol

Nanoporous metals are expected to be promising material in the future due to its unique structural properties,such as open bicontinuous metal-void phase,high surface-to-volume ratio and great porosity.Nanoporous Au-Ag alloys and nanoporous gold(NPG) with uniform pore sizes and ligaments,prepared by selective dissolution of Ag from Au₄₂Ag₅₈ alloy samples in HNO₃ solutions,are more suitable for acting as the anode catalyst for electrooxidation of small organic molecules than bulk Au or Au nanoparticles,and the high surface area is help to increase the sensitivity as a electrochemical sensor material.As a result,the main research content of this thesis focus on the characterization of electrocatalytic oxidation of glucose on nanoporous Au-Ag alloys and the fabrication of novel electrochemical sensor based on nanoporous gold(NPG),which are summarized as follows:(1)Nanoporous Au-Ag alloys with different Ag content were prepared by selective dissolution of Ag from Au₄₂Ag₅₈ alloy samples in HNO₃ solutions.With gradual dissolution of Ag component,the corroded Au-Ag alloy samples displayed typical bicontinuous nanoporous structures after being etched for 32 min.The as-prepared nanostructured Au-Ag alloys exhibit the higher catalytic activity towards the electrooxidation of D-glucose than the uncorroded Au₄₂Ag₅₈ alloy.It is of interest that the existence of a tiny amount of silver in the corroded Au-Ag alloys is very advantageous to enhancing their catalytic activity for electrooxidation of glucose.The new finding was confirmed by the significant enhancement of the catalytic activity of a nanoporous gold(NPG) electrode after modification with a monolayer of Ag atoms underpotentially deposited.The nanoporous Au-Ag alloys with appropriate amount of Ag and the NPGs modified with Ag UPD monolayers are expected to be promising electrocatalysts for the electrooxidation of glucose.(2) The as-prepared NPG samples were used as the working electrodes to investigate the redox behavior of p-nitrophenol(p-NP) by cyclic voltammetry.Quite different from voltammetric behavior of polycrystalline gold electrodes,the cyclic voltammograms(CVs) of the NPG display a pair of nearly symmetrical redox waves which are ascribed to the reaction of 4-(hydroxyamino)phenol / 4-nitrosophenol couple.It is interesting that this pair of redox waves are hardly affected by the isomers of p-NP;and moreover,their peak areas are linear with the concentration of p-NP in the range from 0.25 mg dm^-3 to 10 mg dm^-3.Because of high sensitivity and good selectivity,the NPG is expected to act as a promising electrochemical sensor material for detecting trace p-NP in wastewaters.