In Situ Generation Of Uncoated Plasmonic Nanoparticles For Photocatalysis And Nanosensing

Plasmonic nanoparticles（NPs）,such as Au,Ag,and Cu,have high optical trapping capacity due to the localized surface plasmon resonance（LSPR）.The optical absorption of plasmonic NPs is widely adjustable on the visible spectrum and easily affected by many factors.Thus,plasmonic NPs are widely used in the construction of photocatalysts and nanosensing.During the synthesis of plasmonic NPs,the protectant（such as citric acid,tannic acid,ascorbic acid,cetyltrimethylammonium bromide,polyvinylpyrrolidone,and polyvinyl alcohol）contributes to control the structure morphology,size distribution,and stability.However,the protectant would remain on the surface of plasmonic NPs,which would affect the catalytic performance and the interaction with target molecules.At the same time,the protectant will seriously hinder the study of the true structure-property of clean NPs.Therefore,designing stable and uncoated plasmonic NPs as a photocatalytic system and colorimetric sensing platform are of great significance for the study of direct photocatalysis of plasmonic NPs and the development of efficient sensing strategies.As a physical and chemical barrier,the protectant limits the free interaction of reactants or analytes onto the surface of NPs.Aiming at the problem that the protectant in the synthesis of plasmonic NPs affects its catalytic performance and the interaction with the target molecule,a design strategy of in situ generation of plasmonic NPs on a functional carrier is proposed in this thesis,and develops a new method of efficient photocatalysis and novel nanosensing.The main research contents are as follows:1.Ag-Ti₃C₂ nanohybrids are prepared by the in-situ generation of bare surface Ag NPs on the Ti₃C₂ Nanosheets（NSs）,which improved the transfer efficiency of photogenerated carriers.Compared with Ag NPs that have stable protectants on the surface,uncoated Ag NPs have higher carrier transfer efficiency,and the photocatalytic degradation efficiency of plasmonic-driven methyl orange（MO）is increased by 95times.The Ti₃C₂-assisted plasmon-driven hot charge carrier separation in photocatalysis is investigated to enhance the direct plasmonic photocatalysis of uncoated Ag NPs.The partial oxidation of Ti₃C₂ to Ti O_2-x introduces the plasmonic metal-support interaction（PMSI）between the plasmonic metal and the support,which is different from the general plasmonic photocatalytic performance improvement mechanism.Ti₃C₂-assisted plasmonic hot carrier separation offers the prospect of designing more efficient direct photocatalysis of uncoated Ag NPs.2.Based on the bare surface of Ag-Ti₃C₂ nanohybrid,a novel I^-nanosensing strategy is constructed,and the limit of detection of I^-in the concentration of 0.5-300μM is as low as 0.31μM.A novel visual I^-detection system with high sensitivity and selectivity is established by the correlation between the color change caused by the MO signal and the concentration of I^-.Ag I and electrons are generated by I^-etching uncoated Ag NPs.Benefiting from the excellent O₂ adsorption capacity and the prominent metallic conductivity,Ti₃C₂ is used to obtain electrons and produce H₂O₂through a self-driven Fenton-like process.Moreover,the in-situ formed H₂O₂ oxidizes and degrades MO molecules adsorbed on Ti₃C₂.A systematic study on the mechanism of the I^--induced etching of uncoated Ag-Ti₃C₂ nanohybrids,and further substantiates that the formation of H₂O₂ is controlled by the amount of I^-,which is reflected upon the extent of MO degradation.Therefore,the proposed sensing strategy realizes the real-time colorimetric detection of I^-in the environment.3.Ti₃C₂ Quantum Dots（QDs）were prepared by Ti₃C₂ NSs,and a fluorescence colorimetric dual-mode sensor system for Ag⁺detection was constructed,which realized the rapid and sensitive detection of Ag⁺in environmental water samples.Ti₃C₂QDs retain part of the reducibility of Ti₃C₂ NSs and can induce Ag⁺to produce Ag NPs,which causes colorimetric signal changes and fluorescence signal enhancement.In the colorimetric sensing strategy,the limit of detection of Ag⁺in the concentration of 0.5-160μM is as low as 0.41μM.In the fluorescence sensing strategy,the limit of detection of Ag⁺in the concentration of 0.5-40μM is as low as 0.45μM.Therefore,the dual readout Ag⁺based on Ti₃C₂ QDs will pave a new way for the development of a fast and accurate real-time detection platform,and this design realizes the real-time rapid detection of Ag⁺in the environment.4.Au-PCN-222（Fe）nanozyme cascade catalytic system is designed based on the in-situ generation of uncoated Au NPs by PCN-222（Fe）,and the reaction process of the nanozyme cascade catalytic system can be regulated by light.Taking advantage of the property of phosphatase-like,the substrate of 4-nitrophenyl phosphate disodium（p-NPP）is concentrated in PCN-222（Fe）to produce 4-nitrophenol（p-NP）.At the same time,Au NPs are used to reduce p-NP to 4-aminophenol（p-AP）with the assistance of Na BH₄.Benefitting from the different mechanisms of light and dark reactions,the reaction progress of p-NPP to p-AP is regulated by light.Therefore,the logical control of the nanozyme cascade catalytic reaction process through plasmonic switches is conducive to the precise regulation of the nanozyme cascade system by light.