Synthesis And SERS Applications Of Spiny Gold Nanoparticles And Their Core-shell Nanoparticles

Plasmonic gold nanoparticles are widely applied in surface-enhanced Raman scattering(SERS),photocatalysis,optical sensing,biomedicine and environment due to their unique local surface plasmon resonance(LSPR)effect Research areas such as science.The LSPR effect is related to the morphology of plasmon materials so that it can provide new application opportunities in SERS,plasmon photocatalysis and other fields.Compared with gold nanospheres and gold nanorods,the surface of gold nanoparticles(AuNMs)with a three-dimensional spiny branch structure and rougher surface,stronger adsorption capacity and higher SERS enhancement effect.However,it is very difficult to control the morphology of AuNMs.Especially,the control of the spiny branch density on the surface of AuNMs with free-surfactant is still a challenging in current research.For a long time,the object of SERS detection is still limited to molecules with strong adsorption on the enhanced substrate,and it is still difficult to detect molecules with weak adsorption or no interaction with the substrate.Metal-organic framework(MOFs)materials with many advantages such as regular pore structure,high porosity,adjustable pore size,and good stability can not only adsorb and enrich molecules,but also weaken the flow and diffusion of molecules on the substrate.In addition,if gold nanoparticles with plasmon characteristics are introduced into MOFs materials to form a new SERS substrate,the substrate has both the LSPR properties of gold nanoparticles with plasmon characteristics and the excellent adsorption and enrichment of MOFs materials Function,you can break through the limitations of these molecules on the SERS solid substrate with poor adsorption and difficult to detect.In this paper,a variety of different shapes of anisotropic AuNMs and AuNMs@ZIF-8 core-shell nanoparticles with different shell thickness were prepared.The growth mechanism of nanoparticles was studied specifically,and realizing qualitative or quantitative detection of some samples with their SERS effect..The main research contents and conclusions are as follows:1.AuNMs was synthesized using seed-mediated growth method in the absence of surfactants.The density of spiny branches on the surface of AuNMs was successfully adjusted and the growth mechanism was studied in detail.It was showed that balancing chloride ion concentration and ascorbic acid activity inthe growth solution was the key for optimal AuNMs.2.The finite-difference time-domain(FDTD)method was used to calculate the electromagnetic field distribution of a single AuNMs.And the electromagnetic field coupling between AuNMs dimers was simulated at different excitation wavelengths,the study results were analyzed in detail..3.A single layer of AuNMs with optimal SERS activity was laid on a silicon substrate and used as a reinforcing substrate to evaluate the SERS enhancement.The limit of detection of p-aminothiophenol as the probe molecule up to 1 n M level.In addition,a single layer of AuNMs was laid on a glass substrate to detect the residues of thiram pesticides on grape surface.The limit of detection was less than 1 ?M,which met international and domestic detection standards.4.Using seed-mediated growth method,the core-shell AuNMs@ZIF-8 was synthesized by embedding multi-spiny gold nanoparticles(AuNMs)into within zeolitic imidazolate frameworks-8(ZIF-8)and the thickness of ZIF-8 porous on AuNMs can be effectively controlled as need by varying the concentrations of the ZIF-8 precursors.Using the prepared thin shell AuNMs@ZIF-8 as a SERS reinforced substrate to trace detection of volatile formaldehyde.The core-shell substrate exhibits a high SERS response toward gaseous formaldehyde up to a ppb limit of detection.Further,the causes of SERS enhancement were analyzed in detail.The Raman enhancements due to not only plasmonic effect of AuNMs,but also the molecule-trapping capability of the microporous ZIF-8 shell.The existence of porous structure makes the flow rate of gaseous molecules slow and changes the travelled route,thereby the gaseous molecules easily approach the hot spots.This study provide a new methods for molecular detection,it can be potential applied in molecular sensing.These results have important guiding significance for the synthesis of gold nanostructures with different morphologies and core-shell nanoparticles.The synthesized porous core-shell structure overcomes the non-selective limitations of conventional SERS detection methods,which provides a new method for detecting small molecules,volatile molecules,gas molecules,etc.