Study On Preparation,Optical,Electrical Properties And Applications Of Silver Nanostructure Materials

Compared with traditional bulk metal materials,silver(Ag)nanomaterials have attracted extensive attention due to their unique optical,electrical,thermal,and antibacterial properties.Recently,how to interpret these photoelectric phenomena in Ag nanomaterials and make full use of these properties for practical application has been a research hotspot in this field.Based on these purposes,silver nanowires,silver nanoparticles,and their composites were prepared by chemical methods.On this basis,we have analyzed a series of unique photoelectric phenomena in various Ag nanostructures and discussed the application prospect of Ag nanomaterials in detail.The main results are summarized as follows:1.In this work,we have developed a flexible,robust,and reusable silver-functionalized SERS substrate for pesticide residue detection.This SERS substrate is composed of a silver nanoparticle@silver nanowire(Ag NP@Ag NW)network that is embedded into polydimethylsiloxane.The unique network structure provides rich LSPR(localized surface plasmon resonance)‘‘hot spots'',where the electromagnetic field can be magnified through the excitation of localized surface plasmon resonances of Ag NPs that surround Ag NWs.The embedded structure improves the adsorption ability of the surface for target molecules,thereby reducing Raman fluorescence.In addition,this substrate retains 54.7%of the original Raman intensity after ten cycles;hence,this substrate shows satisfactory recyclability performance.Moreover,the SERS substrate exhibits acceptable detection reproducibility with 4.22%relative standard deviation and satisfactory tensile properties.These results demonstrate that our substrate has the potential for use in environmental supervision,food safety,and security applications2.Although silver-based SERS substrates have desirable enhancement factors(EF)and relatively low cost,gold structures have been preferred owing to their proved long-term oxidation(tarnishing)stability.Here we have developed a large-area monolayer gold nanoparticles(Au NPs)densely arranged on Ag NWs network/PDMS surface for SERS application.This substrate shows not only an equivalent EF to Ag NWs/PDMS structure in our previous studies but also long-term stability for SERS(reproducible for over 6 months under ambient condition).Moreover,the interface plasmons model between two different metals combined with the 3D finite-difference time-domain method is presented to interpret EF change rules in Au-Ag composite nanostructure and the basis of field enhancement.3.This work reports the use of Ag NWs,as a research object to study the mechanism of LSPR generation and hot electron transfer at the metal-semiconductor nanostructure interface.We further investigated the influence of hot electron released by Ag nanostructures on SERS,photocatalysis,and photoelectric chemical reaction.Tungsten oxide(WO_3-x)is a type of transition metal oxide that has rich substoichiometric compositions and possesses oxygen defects.These oxygen defects determine the photon–electron interactions in the WO_3-x structures.Therein,WO_3-xquantum dots(QDs)exhibit fast carrier-transport for photon–electron interactions due to their strong quantum-size effects.In this study,We use of non-stoichiometric WO_3-xQDs in combination with Ag NWs to study photon–electron interactions on the nanoscale.We demonstrate that the incident photon-to-electron conversion efficiency can be increased by 8.5%and that the dye photodegradation performance was improved by 40%in a WO_2.72 QD@Ag NW(WO_2.72 QDs supported on Ag NWs)composite compared to those of individual WO_2.72 QDs under simulated AM 1.5G light.Furthermore,the WO_3-x QD@Ag NW composite exhibits both photocatalytic activity and surface-enhanced Raman scattering(SERS)features,and the WO_3-xQDs can be switched between a“photocatalytic state”and a“SERS state”by changing the stoichiometric ratio.The synergistic effects are ascribed to the“plasmonic state”of WO_2.72 QDs upon light irradiation.This work provides new insight into the design of highly efficient transition metal oxide/plasmonic metal nanocomposites for photoelectric devices.4.In this study,Ag NWs/HPCM aerogels with the porous structure were prepared by a freeze-drying method.In the preparation process,HPMC,as water-soluble fiber,can be mixed directly with Ag NWs in aqueous solution without adding any dispersant or pretreatment.This advantage greatly simplifies the preparation process of Ag NWs/cellulose aerogel structure.The prepared Ag NWs/HPMC aerogel exhibits low density(52 mg cm^-3),high porosity(96.5%)and high electromagnetic interference shielding efficiency(90 d B).This work suggests that the content of HPMC in Ag NWs/HPMC aerogel affects the pore size and distribution in aerogel structures,which directly determines the shielding mechanism in the aerogel structure(reflection loss and absorption loss).