Electroanalysis Of Small Molecules Based On Silver/gold Staining And Galvanic Replacement Reaction On The Surface Of Nanogold

Due to the unique physicochemical properties of noble metal and nanomaterials, noble metal nanomaterials have attracted much attention in the fields of energy, environment, bioscience/biotechnology and analysis/testing. Metal staining has important application in the biological analysis because of the high sensitivity and low cost. The galvanic replacement reaction can be ultized to prepare noble metal nanomaterials, which has been extensively studied in recent years. In this thesis, we briefly review noble metal nanomaterials, metal staining and galvanic replacement reaction. Then we study the preparation of the electrodes modified with the noble metal nanomaterials(platinum, gold and palladium) based on galvanic replacement reaction and the silver staining/gold staining on the surface of nanogold. The electrochemical analysis of small molecules such as ethanol, glucose and formaldehyde are performed. The main concents of this thesis are as follows.1. This paper presents a new approach for preparing a rough Pt film on an electrodeposited Au modifiedAu disk electrode(Aupla/Au) by silver staining and galvanic replacement reactions(GRRs), and the mod-ified electrode is used for amperometric and fuel-cell-based sensing of ethanol. Briefly, Ag was stainedon Aupla/Au through chemical reduction of AgNO3 by hydroquinone(Ag/Aupla/Au). The GRRs betweenthe stained silver and H2PtCl6 produced size-enlarged nanoparticles containing Pt and AgCl, and elec-troreduction and ammonia rinse of AgCl could efficiently enhance the porosity to finally obtain thePtGRRx/Aupla/Au electrode, where x denotes the number of silver staining/GRR cycles. Scanning electronmicroscopy, energy-dispersive X-ray spectroscopy, quartz crystal microbalance and cyclic voltamme-try were used to characterize the modified electrode. The PtGRR4/Aupla/Au electrode exhibited a linearanodic amperometric response to ethanol concentration from 0.01 mM to 11.3 mM with a limit of detection(LOD, S/N = 3) of 3 μM, excellent stability and acceptable selectivity, which was used for analysis ofethanol in real Chinese liquor samples with satisfactory results. An ethanol/O2 fuel cell was constructedusing two PtGRR4/Aupla/Au electrodes, which showed a self-powered linear voltage response to ethanolconcentration from 0.02 to 15.7 mM with a LOD of 15 μM.2. Au was selectively stained on the catalytic Au nanoseeds surfaces on an electrodeposited Au modified glassy carbon electrode through gold staining from redox reaction between HAuCl4 and hydroxylamine hydrochloride. The analytical performance of glucose at the electrode modified with amplified gold nanoparticles was studied in the alkaline medium. The results show that the modified electrode exhibited a linear amperometric response to glucose concentration from 0.001 mM to 17.5mM with a sensitivity of 530 μA mM-1 cm-2 and a limit of detection of 0.5 ?M. This method is expected to find applications in detection of glucose in real blood serum samples.3. The glassy carbon electrode modified with nanoporous palladium was prepared by silver staining and galvanic replacement reaction between stained silver and chloropalladic acid. The electrooxidation of formaldehyde in alkaline medium was studied. The modified electrode exhibited a linear detection response to formaldehyde concentration from 0.005 mM to 8.55 mM with a sensitivity of 842 μA mM-1 cm-2 and a limit of detection of 1 ?M. This method has the potential for application in formaldehyde analysis in real samples.