New Gold-silver Nanocomposite Materials And Their Medical And Environmental Sensing And Detection Applications

Gold?Au?and silver?Ag?noble metal nanomaterials with good electrical conductivity,catalytic activity,and photoelectric properties have been widely used in photocatalysis and medical sensing fields.In the thesis,the high adsorption performance of melamine?MA?and the photocatalysis of zinc oxide?ZnO?were utilized introduced.Moreover,some Au and Ag noble metal nanocomposites were synthesized to modify the electrodes or used as functional probes for the sensitive and specific analysis of sulfides,glutathione?GSH?,uric acid?UA?,and formaldehyde.These contents mainly include:?1?A kind of Ag-MA mesoporous nanocomposites were synthesized through a controlled supramolecular self-assembly pathway,which was then modified on the electrode surface to achieve the electrical analysis of multiple sulfides in high salt medium?Chapter 2?.The results show that wirelike and rodlike Ag-MA nanocomposites were prepared by controlling the ratios of Ag and MA.The electrode modified with wirelike Ag-MA nanocomposites were found to show a stable and sharp electrochemical oxidation peak of solid-state AgCl?the peak potential is close to zero?,which could effectively avoid the interference of other electrically active substances coexisting in the background.More importantly,after the introduction of sulfides,the yielded AgCl signals would decrease through the specific sulfide-chloride replacement reaction towards the transferring of AgCl into Ag₂S.The so established electrochemical analysis technique can allow for the specific and sensitive analysis of multiple sulfides(H₂S/S^2-,S_x^2-,S₂O₃^2-,and cysteine)in high salt media such as blood and wastewater,achieving the detection limit of S^2-ions in blood down to 0.24?M.?2?A microwell electrode was fabricated with Ag-doped ZnO?Ag-Zn O?nanocomposites for the detection of GSH in cells?Chapter 3?.The superhydrophobic coating was prepared on ITO plate using octadecyltrichlorosilane?OTS?and Ag-ZnO nanocomposites that were prepared through a sol-gel route.Furthermore,the microwell modified electrode was prepared by use of the photocatalysis of Ag-ZnO that would catalyze OTS to yield the superhydrophilic microwell.Benefitting from the super-wettability difference between the microwell and the surrounding substrate,the microwell modified electrode can efficiently enrich the trace analytes from the solution.A stable and sharp solid-state AgCl electrochemical oxidation peak could be obtained at near zero potential.Especially,due to the strong interaction of thiols in GSH and Ag in AgCl,the solid-state AgCl signals on the microwell modified electrode would be reduced.A sensitive and specific electroanalysis method has thereby been achieved for probing GSH in cell samples,with the detection limit of about 11.25 pM.?3?An electrical analysis technique has been developed for the UA in blood based on Au-MA nanocomposites?Chapter 4?.Through using MA as the reducing agent,the Au-MA nanocomposites were first synthesized and then modified onto the electrodes.It was found that UA could be efficiently adsorbed onto the Au-MA modified electrodes by taking advantage of the large volume-to-surface area of MA in Au-MA nanocomposites.Moreover,the prepared eletrodes would benefit from the high conductivity and electrocatalytic activity of Au nanoparticles in Au-MA nanocomposites.Based on the pH-denpending oxidation peak potentials of UA,the developed Au-MA modified electrodes could facilitate the specific electroanalysis of UA in blood,showing the detection limit of 0.54?M.?4?The test strips were fabricated using Ag-MA nanocomposites that were synthesized by supramolecular self-assembly for the visual detection of formaldehyde in water?Chapter 5?.It was found that the test strips enabled the efficiently covalent adsorption for formaldehyde with the aid of Ag-MA nanocomposites,of which the silver components would be reduced to form a visible black precipitate under the alkaline condition to be further measured by the solid phase reflectance.Rapid and visual colorimetric analysis of formaldehyde could be realized in the linear range of 0.1-22.0?M,with the detection limit of 0.039?M.