Regulation Of The Surface Plasmon Resonance Of Silver Nanostructures And Its Application In Surface Enhanced Raman Scattering

With continuous development of nanotechnology,various size,composition,and morphology of coinage metal nanostructures emerge in an endless stream.For now,of the metals,silver can support the strongest Surface Plasmons Resonance?SPR?,so it has been widely concerned due to a great potential application for the high-sensitivity biological,chemical detection and sensing.Based on the study of the optical response of silver nanoparticle arrays,this paper mainly focus on the preparation of high performance Surface-Enhanced Raman Scattering?SERS?substrates by dry process and achieving the trace and in situ detection.The combination of Ag nanoparticles and three-dimensional nanostructures can be realized with plasma etching,ion sputtering and annealing process.Based on that,a high density distribution of “hot spots” can be obtained.And eventually prepared a high enhancement factor,uniform and repeatable SERS substrate in large-scale and cost-effectively.Details are as follows:1?The structure and the optical response of sliver nanoparticles can be controlled with the aid of hexagonal close-packed aluminum pit arrays,thin film deposition technique and annealing process.The morphology,size?5 nm –100 nm?,inter-particle distance?3 nm – 100 nm?and distribution of sliver nanoparticles on this nanostructure can be well define via varying the thickness of initial sliver film and selecting the different annealing temperature and aluminum pit arrays.Based on that,the optical response of silver nanoparticle arrays with small size?³0 nm?were studied.The distinct quadrupole resonance mode is observed in the experiment due to a strong electromagnetic coupling between silver nanoparticles,which making the dipolar resonance mode shifts toward longer wavelength,and a 80 nm spectral shift was thus observed.Moreover,we also confirm our interpretation of experimental phenomena by a electromagnetic simulation.The quadrupole resonance mode indicating the strong coupling of the electromagnetic field between the small size metal nanoparticles,and that's the essence of electromagnetic enhancement mechanism of SERS.Therefore,the appearance of the quadrupole resonance mode is the sign of a high-sensitivity SERS substrate.Raman measurements confirmed that coupling array has a higher SERS activity and its detection limit of R6 G is 10^-9 M.2?High sensitivity three-dimensional?3D?SERS substrates were prepared using the maskless plasma etching and ion sputtering.The top and bottom diameter of a single nanocone is 15 nm and 35 nm,respectively,its height is about 150 nm,and the distribution density is up to 650 ?m^-2.Optimizing the sliver sputtering duration,a SERS is greatly enhanced,so this substrates are highly sensitive with excellent reproducibility,exhibiting an enhancement factor up to 1012 with a very low relative standard deviation?RSD?around 5%,and its detection limit of R6 G is up to 10^-13 M.Moreover,the trace dimethyl phthalate?DMP?at a concentration of 10^-7 M can be well detected using this SERS substrate,revealing its potential in the detection of pollutants.Furthermore,we have obtained a high density 3D silicon nanowire array by using in situ alumina template combined with metal assisted chemical etching.The diameter and length of the silicon nanowires can be well defined by regulating the structure of the aluminum oxide template and the conditions of chemical etching,followed by supercritical drying was developed and eventually well-separated,vertically aligned silicon nanowire array can be obtained.The high controllability of this three-dimensional silicon nanowires array laid a foundation for the further fabrication of highly active SERS substrates.3?Nanowire arrays rooted on the surface of polyethylene terephthalate?PET?membrane were obtained by treating it with oxygen plasma.Silver nanoparticles decorated nanowire arrays have a variety of types of “hot spots”,which can greatly improve the detection sensitivity and reproducibility of substrates,and its detection limit of R6 G is 10-8 M.Importantly,due to good flexibility,high transparency of the polyethylene terephthalate,this SERS substrate can be applied to the in situ ultrasensitive detection of analyte on irregular objects.Furthermore,the trace analyte attached to the fruit surface has been well detected using this SERS substrate through in situ detection,and it shows that this flexibility,transparency,3D SERS substrate has a excellent potential applications in daily life,especially in the in situ detection of pesticide residues on the surface of vegetable and fruit.