Development And Applications Of Sensitive Detection Based On SPR Effect Of Noble Metal Nanostructures

Noble metal nanostructures have been extensively studied because of the surface plasmon resonance(SPR)effect,which results in a significant enhancement of the local electric field near metal surface.The study of sensitive detection based on SPR effect has played a key role in the low content detection and is very important for many research fields.However,recent applications become increasingly demanding on detection sensitivity,and its improvement has become an urgent issue.Recently,with the rapid development of materials synthesis technology,the interaction mechanism between noble metal nanostructures and various materials has been gradually studied and utilized.Compared with the simple structure of the noble metals,these hybrid structures exhibit richer optical properties because of the interaction between surface plasmas and materials.A large number of theoretical and experimental results have confirmed that the composite noble metal nanostructures can further enhance the local electric filed,which has a great potential in improving detection sensitivity.However,the current research in this field mainly focuses on the design,fabrication and optical properties of various forms of composite structures,while the research of their applications based on the relevant mechanism,which should have great practical values and significance,is relatively inadequate.Aiming at this scientific problem,based on the SPR effect of noble metal nanostructures,a variety of sensitive detection techniques from both experimental and theoretical aspects are developed in this thesis.The main contents of the thesis are as follows:1.By using the hybridization LSPR effect of composite noble metal nanostructures and the charge transfer mechanism of the metal surface,silver nanoparticle dimer structures with a gap of about 1 nm were designed and fabricated for highly sensitive detection and quantitative analysis of neurotransmitters dopamine molecules.Silver nanoparticles are rich in carboxyl groups,which combine with amino groups on dopamine molecules to form stable chemical bonds providing an efficient charge transfer channel.Thus,a high SERS intensity and very low detection limit are obtained experimentally.The detection limit reaches 20 pM,and there is a good linearity between30 pM and 300 nM.The average relative prediction error between the predicted concentration of dopamine and the actual concentration of the tested sample is 4.22%,which is considered to have a good practical application prospect.2.By utilizing silver nanoparticle dimer structures,we studied the adsorption mechanism of molecules on the surface of the noble metal.The effect of binding energy on the metal surface and the charge transfer mechanism of enhanced adsorption induced by light field were investigated and analyzed.The experimental results show that the adsorption types of Nile Blue and Crystal Violet molecules on the surface of silver nanoparticles are physical adsorption.The binding energies are less than 40 kJ/mol,and the charge transfer effect between the molecules and metals is weak.A strong charge transfer phenomenon exists for dopamine molecules adsorbed on metal surface with the binding energies 256 kJ/mol.Surface enhanced Raman spectroscopy and infrared spectroscopy show that there is a charge transfer between DA molecule and Ag nanoparticles.Further experimental results show that the adsorption of Nile Blue and Crystal Violet molecules at a specific concentration can be increased by the inducing light field.Through a multi-layer adsorption kinetic model,we preliminarily analyzed the enhancement mechanism of light field induced adsorption on physical adsorption types.3.By utilizing noble metal/dielectric interface structure,a phase-type SPR Bio-detection platform consisting of a single-layer graphene,few-layer antimoneneand nano-thickness gold film was designed.In the SPR detection layer,the Van der Waals heterojunction is formed between monolayer graphene and few-layer antimonene,which is used to enhance the photon absorption.Under the SPR excitation,the graphene/antimonene heterojunction generates an effective charge transfer to the gold film to provide enough excitation energy,leading to a significant electric field enhancement at the interface of the detection layer.Monolayer graphene can also be used as a bio-recognition site to capture aromatic bio-analytes by the?-?stacking effect.The detection sensitivity of this model was studied systematically by optimizing the thickness of the gold film and the number of antimonene layers.The optimized results show that the best detection condition is depositing bilayer antimonene and monolayer graphene on 47 nm gold film,the highest sensitivity of the proposed bioassay model is about 64.8 times higher than that of graphene/gold composite nanostructures.4.Further,by utilizing noble metal/dielectric interface structure,a tunable phase-type detection model with high sensitivity based on the SPR effect is proposed.By overlaying anisotropic two-dimensional layered material graphene and black phosphorus(BP)on a gold film,the sensitivity becomes adjustable.The monolayer graphene does not only provide the binding sites for aromatic biological molecules,but also prevents the degeneration of the BP layer.In the case of SPR excitation,the strong charge transfer between graphene,BP and gold film can significantly enhance the electric field near the sensing interface and thus improve the detection sensitivity.The simulation results show that the phase-type BP/graphene/gold film biosensor model is more sensitive than the traditional angle-type SPR detection model,and its sensitivity is improved by about three orders of magnitude.The simulation results show that the optimal parameters are 48 nm thick gold film and 4 layers of BP monolayer graphene,which lead to the highest detection sensitivity 7.4914×10~4 deg/RIU.The excitation state of SPR can be further controlled by rotating the angle of BP layer,which realizes the adjustability of detection sensitivity.5.By utilizing noble metal/dielectric interface structure,a tunable phase-type pressure detection model based on SPR effect is proposed.Few layered antimonene and pressure-sensitive two-dimensional material monolayer?-SnSe were stacked on a gold film to realize pressure detection.By adjusting the number of antimonene layers and the thickness of Au film,the detection range of the pressure sensor is efficiently regulated.Graphene is introduced to generate effective charge transfer to the gold film and enhance the pressure resistance.