Tuning Surface Plasmon On Noble Metal And Application In SERS And Photothermal Therapy

Surface plasmons?SPs?is an electromagnetic oscillation formed by the interaction of free electrons in the metal surface with the photons,which brings a series of novel optical properties to metals,such as local field enhancement,efficient photothermal conversion efficiency and selective absorption of light,etc.With the deepening of SPs research and the continuous progress of high precision nanofabrication technology,SPs can be effectively regulated to meet different applications.In this paper,we have effectively regulated the SPs of noble metal by adjusting the morphology and composition of noble metal nanostructures,and further compounding noble metal with graphene.Based on the above regulation,we have obtained noble metal nanostructures with high surface-enhanced Raman scattering?SERS?activity and successfully applied to the effective detection of heavy metal ions,small drug molecules and virus particles.In addition,we explored the photothermal effect of noble metal nanoparticles and for photothermal treatment of bone defect.The details are as following.1.A large area,ordered Au TNAs was prepared by using single-layer polystyrene sphere?PS?masks as temple,and the thermal stability of Au TNAs is greatly improved by covering a layer of graphene on Au TNAs.Based on the high thermal stability of graphene/Au TNAs,graphene/Au TNAs was used as a recyclable SERS substrate and for the recyclable detection of amoxicillin and other organic molecules.Compared with Au TNAs,the thermal stability of the monolayer graphene-covered Au TNAs has been greatly improved.The principle of recyclable detection was as follows:by annealing the SERS substrate contaminated by the detected molecules at high temperature in Ar atmosphere,the molecules can be effectively removed,while Au TNAs coated with monolayer graphene can maintain the original structure unchanged,so it can be used to detect the target molecules again.The SERS substrate exhibits excellent performance in recyclable detection of amoxicillin and other organic molecules.2.On the basis of achievement 1,we deposited a layer of Au nanoparticles?Au NPs?on graphene to regulate the coupling between Au TNAs and Au NPs through the presence of graphene,and prepared a substrate with both horizontal and vertical coupling,which greatly increased the"hot spot"density of the substrate,which was successfully applied to the detection of mercury ion(Hg²⁺)in sandy soil.PS particle masks was used to prepare large-area ordered Au TNAs.After graphene was transferred on Au TNAs,Au NPs were deposited on graphene to obtain sandwich structure.The existence of graphene can effectively regulate the gap between Au TNAs and Au NPs,thus forming a large area of uniform sub-nanometer scale"hot spots".Compared with the substrate without graphene,the substrate with the existence of monolayer graphene has a significant improvement in Raman scattering enhancement and electromagnetic field enhancement.The detection limits of Hg²⁺in water and sandy soil can reach 10^-9M and 10^-7 M respectively for SERS substrate with the existence of monolayer graphene.Furthermore,in order to enrich and detect Hg²⁺effectively,Au nanooctahedron?Au NOCs?was used to construct plasma microsphere as a three-dimensional SERS platform for the ultra-sensitive detection of Hg²⁺.After modifying Au NOCs with hydrophobic molecules,water droplet containing Hg²⁺was dripped into Au NOCs,then,Au NOCs self-assemble on the surface of water droplets to form a sealed microsphere,which completely encapsulated Hg²⁺in the microsphere,thus achieving the enrichment of Hg²⁺.The detection limit of Hg²⁺in water can reach 10^-16 M,which is much lower than that of conventional analytical methods.In addition,by combination of microsphere sensing and microfluidic tube for on-line detection,which achieves orderly and fast detection of microspheres containing different concentrations of target molecules.3.In order to effectively detect large-size analyte?such as virus?,On the basis of achievement 1 and 2 single-layer PS array template,we constructed double-layer PS template,combining with oxygen plasma etching,we fabricated a volume-enhanced Raman scattering?VERS?substrate.The substrate has hollow nanocones that match the size of the virus and can effectively enrich the virus particles into the hollow nanocone.In addition,the hollow nanocone is filled with"hot spot",which can greatly improve the Raman signals of single viruses.Compared with the traditional SERS substrate,the repeatability and integrity of virus Raman signals obtained on VERS substrate have been greatly improved.4.Porous gold-palladium nanoparticles?Au@Pd NPs?were synthesized by compounding metal palladium?Pd?with Au.The plasma absorption peaks of Au NPs were successfully adjusted to 650-900 nm,and then Au@Pd NPs were used as near infrared?NIR?photothermal agents for photothermal treatment of bone defects in vivo.Porous Au@Pd NPs can generate appropriate heat under 808 nm laser irradiation,and the appropriate heat can greatly promote cell division and bone regeneration.Through in vivo experiments,porous Au@Pd NPs were used as hyperthermia agent to rapidly promote bone healing through photothermal therapy?40-43°C?.