The Optimization Of Nanometallic-based Localized Surface Plasmon Resonance By Laser And Their Applied Researches

Due to their unique localized surface plasmon resonance(LSPR),metal nanostructures(including Ag,Au,Cu)with tunable light absorption-conversion ability exhibit excellent light excitation response performance under visible-Near-Infrared light irradiation,which has allowed the realization of numerous applications such as biomedicine,food safety,photoelectric sensing,and energy conversion-storage fields.Among them,a locally enhanced electromagnetic field on the surface of metal-based nanocomposites can remarkably enhance the Raman signals for the adsorbed molecules.And the resulting surface enhanced Raman scattering(SERS)spectroscopic diagnostic technology has been widely applied in the fields of microanalysis of medical molecules,early diagnosis of tumor cells,monitoring of organic pollutant molecules,and trace detection of pesticide residues in the epidermis of fruits and vegetables.Additionally,considering the efficient conversion efficiency of the unique LSPR effect of nanometals towards visible-Near Infrared light,the metal-based composite configuration can be used as highly active photocatalysts to achieve efficient conversion from solar energy to chemical energy,which will promote the rapid development of many energy conversion fields such as photocatalytic hydrogen production,photocatalytic degradation,carbon dioxide reduction,nitrogen fixation,and organic synthesis.Regulating the microscopic morphology of metal-based composite configuration elaborately can effectively optimize its LSPR effect and continue to promote the application of light excitation.Over the years,researchers have achieved remarkable results in preparation of a variety of complex microstructures such as porous,core-shell,hollow,long dendritic,heterojunction,and polycrystalline heterogeneity or surface defects.On this basis,how to further obtain metal-based composite materials with clean surface is also a current research hotspot.Because the light excitation response based on LSPR is the surface atoms driven by the light on the surface of the nanomaterial interact with external environment,which will result in the significant light sensing,photocatalysis,photoelectric conversion,etc.Therefore,materials with clean surface should be guaranteed so that its interface can directly and effectively contact the incident light with the external reaction environment,which is more conducive to play the significant advantages of the LSPR effect in many frontier scientific and technological fields.In order to design metal-based nanocomposite configuration ingeniously,conventional synthesis methods need to use complex organic reagents as protective ligands for regulating metal nucleation crystallization to realize the construction of multimorphological nano-metals.Subsequent isolation layers formed by organic reagents attached to the surface of nanoproducts will inevitably reduce the light-to-electric conversion/transmission performance.Therefore,the surface of materials must be cleaned and purified through tedious and rigorous cleaning-purification processes.In contrast,as a new type of green and environmentally friendly synthesis method,the laser control optimization strategy does not need to introduce additional complex organic reagents to fabricate metal nanocomposites with high-clean surface.It is based on the excitation mechanism of light-substance interaction as well as the photons absorption-conversion-excitation in the micro-processing technology to realize the modification of material structure.Moreover,reasonable control of laser irradiation parameters can also systematically optimize the design of the inherent LSPR of the constructed metal-based composites.This thesis focuses on the exploration of laser-induced synthesis strategy in liqulid.It is based on the the active electrons formed by laser exciting the precursor material effectively are used as a green and efficient reducing agent to realize the effective reduction of metal ions in the surrounding solution leading to controllable synthesis of various metal-based composite configurations.According to the above laser control optimization strategy,we mainly prepared high-efficiency Au/Ag/AgCl nanochains visible-light catalysts and four high-activity SERS substrates including Ag@Au nanodendrites,ZnO@Au,Ag@ZnO and GO/Au nanocomposites.Additionally,we have carried out a meaningful extended exploration.Based on the rich oxygen-containing functional groups on the GO surface,PtPd nanoflowers were successfully grown on their surface with the assistance of ethanol,and the electrocatalytic properties of the GO/PtPd nanocomposites were explored.The main research content of this paper can be summarized as follows:1.Exploration of 532 nm pulsed-laser irradiation-induced synthesis strategy,and synthesis Au/Ag/AgCI nanochains with clean surface by exciting metal ion mixed solution effectively.The unique chain-like configuration and the strong synergistic coupling effect in the ternary system make Au/Ag/AgCl nanocomposites exhibit excellent wide-spectrum response LSPR characteristics,which in turn promote the transfer of photogenerated electrons and the efficiency of charge carriers separation.Compared with monodisperse Ag/AgCl nanoparticles,taking methylene blue(MB)as research molecules,the Au/Ag/AgCl nanocomposite configuration showed significantly enhanced visible-light photocatalytic degradation performance.It is worth noting that the inherent self-deposition characteristics of ternary Au/Ag/AgCl nanochains make it automatically separate from the supernatant,which can easily complete sewage purification without subsequent separation steps of catalysts in traditional research.The as-prepared Au/Ag/AgCl can still maintain photocatalytic degradation rate of?97.6%even after 14 repeated photodegradation for two consecutive weeks,furrther revealing that this unique high-activity catalyst also has long-term stability.This research will provide new ideas for the subsequent design of other more excellent photocatalysts and expand its application research.2.Based on the 532 nm continuous laser irradiation-induced synthesis strategy,the Ag@Au nanodendrites with tunable composition(relative content of Ag 1.2?34%)were fabricated.We analyze the excellent SERS performance of as-prepared Ag@Au nanodendrites by using 4-aminothiophenol(4-ATP)as probe molecules.In this study,compared with other bimetallic component nanostructures,Ag@Au nanodendrites with relative content of Ag 34%can significantly enhance the SERS activity due to its significant intermetallic synergy,which detection limit is as low as?10-14 M and the enhancement factor(EF)is up to?1011.This work can effectively adjust the bimetallic components of Ag@Au nanodendrites by laser irradiation-induced synthesis strategy,thereby optimizing the synergistic coupling effect between the metals and obtaining better SERS activity,which provides experimental and theoretical basis for subsequent SERS diagnostic analysis of molecules with ultra-low concentration.3.Based on the short-wavelength ultraviolet laser irradiation strategy in liquid,Ag and Au nanoparticles are controllably loaded on the surface of ZnO semiconductors to construct Ag@ZnO and ZnO@Au heterostructure composite configurations.The semiconductor ZnO is excited by the ultraviolet laser to generate electron-hole pairs,and then the active electrons generated by the excitation are used as a novel reducing agent to reduce surrounding metal ions to realize the controllable overgrowth of metal nanoparticles.Based on the as-synthesis of Ag@ZnO nanocomposites,the detection limit for crystal violet(CV)is as low as 10-9 M,and the EF is as high as?107.Further,using ZnO@Au nanocomposites as SERS substrates,the detection limit for methyl blue(MB)is as low as 10-9 M.Based on its excellent photocatalytic degradation ability,after 20 cycles of SERS detection-photocatalytic degradation experiments,the ZnO@Au SERS substrates still show excellent ultra-sensitive detection ability.This research can easily and efficiently support noble metal Ag and Au nanoparticles on relatively inexpensive semiconductor structures by ultraviolet-laser irradiation strategy.It has both the chemical enhancement mechanism(CM)caused by the charge transfer of the semiconductor and the noble metal LSPR induced electromagnetic field enhancement mechanism(EM),making it more advantageous than a single type.Additionally,based on its excellent photocatalytic degradation characteristics,it can realize the reuse of SERS substrates and provide new ideas for the development and design of other low-cost and high-performance SERS substrates.4.Based on the UV laser irradiation strategy in liquid,the reducibility of oxygen-containing functional groups on the surface of the 2D GO is effectively improved by light excitation,and GO/Au nanocomposites are constructed by high-density,monodisperse Au nanoparticles loading on the surface of 2D GO.The optimized GO/Au nanocomposites with 2.25%Au composition give rise to ultralow SERS analyses of(10-14 M)methylene blue(MB),(10-13 M)rhodamine 6G(R6G)and(10-13 M)malachite green(MG),respectively.More importantly,it can also simultaneously analyze these three aromatic dyes in a mixture condition at detection limits as low as nano-mole(nM)level.On this basis,we further expanded and explored other methods to improve the reduction of oxygen-containing functional groups on the surface of GO,that is,using clean ethanol as an auxiliary reagent,combining ethanol with GO enhance surface hydroxyl functional groups and greatly improve its reduction Performance,which supports the growth of PtPd nanoflower structure and obtains GO/PtPd nanocomposites.As for methanol oxidation reaction(MOR),the resulting GO/PtPd nanocomposites provide much higher electrocatalytic performances(mass and specific activity as well as long-term durability)than the loading of monometallic Pt or Pd nanoparticles on the GO support.Especially,compared to MOR test at room temperature(25?),70%electrocatalytic activity of GO/PtPd NFs can be maintained even under low temperature(5?)condition,while that of commercial Pt/C catalysts is merely about 57%.In this study,multi-morphic metal nanostructures can be effectively loaded by optimizing the modification of the oxygen-containing functional groups on the GO surface,and the excellent photoelectric conversion performance can be obtained to promote the cutting-edge cross-research of multifunctional composite materials.