Research On Electrochemical Sensing Technology Based On Silver Nanocomposite Materials

Nanomaterials have been widely applied in many fields such as chemistry,medicine,industry,energy,catalysis and agriculture.Silver（Ag）nanocomposites,with large volume-to-surface area,high stability,good catalytic activity,play a vital role in many reaserach fields.In the present thesis,three type of Ag nanocomposites have been fabricated by using different materials and preparation routes.Moreover,three kinds of electrochemical sensing detection platforms have been established with with these Ag nanocomposites for the electroanalysis of chloride ions,phosphorothioates（PTs）,like-Phoxim（Phox）,and mercury ions with high detection sensitivity ang selectivity.The contents of the thesis mainly include:（1）An electrical analysis method has been established for the detection of chloride ions by using mesoporous materials of Q-graphene（QG）loaded Ag-melamine（MA）nanocomposites.The QG@MA-Ag nanocomposites were synthesized with nanowires structure the controlled supramolecular self-assembly approach using hollow QG as the scaffold.It was discovered that the electrodes modified with QG@MA-Ag nanowires could exhibit highly stable and especially sharp response peaks of solid-state Ag/AgCl electrochemistry at the very low potentials approaching to zero,in the presence of Cl^-ions.Moreover,both of the electrochemical responses of currents（I）and potentials（V）to Cl^-ions could change rationally depending on the Cl^-concentrations.Using the established electrochemical analysis technique with the conductance output（I/V）,highly selective and ultra-sensitive detection of chloride can be realized.The detection range is about 0.25μM to 250.0 mM,with the detection limit（LOD）low as 0.16μM.Such a chloride sensor with the signal outputs of conductances may feature a new format of highly sensitive electroanalysis.（2）A new technology has been established for the electroanalytical detection and photocatalytic degradation of sulfur-containing organophosphorus pesticides（PTs）like（Phox）by using LaPO₄@Ag nanocomposites（Chapter 3）.An urchin-like mesoporous LaPO₄@Ag nanocomposites were fabricated by the citric acid-mediated self-assembly route,showing some outstanding properties of large specific surface area,high environmental stability,high conductivity,and especially strong photocatalysis.The as-fabricated LaPO₄@Ag nanocomposites were employed as the electrochemical probes and photocatalytic adsorbents for the selective electroanalysis and efficient photocatalytic removal of PTs of Phox.It was discovered that the electrodes modified with LaPO₄@Ag nanocomposites could facilitate the detection of Phox at a low potential,which may aid to avoid some of the electroactive substances that might coexist in complex samples.Moreover,the developed LaPO₄@Ag adsorbents with mesoporous hollow structure and large specific surface area,could not only enable the increased adsorption or enrichment of sulfide-containing targets of PTs,but also might present the strong photocatalytic ability under visibal light.The efficient degradation or removal of highly toxic Phox under sunlight was demonstrated.Besides,the so designed citric acid-mediated self-assembly route may pave the way towards the fabrication of various nanocomposites featuring the photocatalysis,adsorption and electroanalysis functions of great interest,thus promising for the extensive applications in the fields of industrial photocatalysis,environmental monitoring,biomedical analysis,and food safety.（3）An electrochemical detection strategy has been developed for the Hg²⁺by using Ag/Ag₃PO₄ nanocomposites（Chapter 4）.The Ag/Ag₃PO₄ nanocomposites,which were synthesized by the one-step way using citric acid as the reducing agent,modified on the electrodes for the electroanalysis of Hg²⁺.The experimental results indicate that the Ag/Ag₃PO₄ nanocomposites can display the advantages of good stability,large surface area and high conductivity.Through the strong Ag-Hg interaction,the developed electroanalysis method can allow for the selective detection of Hg²⁺ions in blood samples in a linear range of 0.10μM to 5.0μM,with the detection limit as low as 0.050μM.