The Preparation And The Localized Surface Plasmon Performance Of Nano-β-Sn-reduced Graphene Oxide Composites

Noble metal-reduced graphene oxide(RGO)nanocomposites have been attracted intense attention thanks to the combination of the strong localized surface plasmon performance of noble metals and the excellent optical,electrical properties and chemical stability of RGO.And therefore,the nanocomposites have been widely used in the fields of bio-sensors,photovoltaic devices,photo detectors,and photocatalysis,and so on.However,the coupling between the noble metals and RGO will be weakened due to the mismatch of electronic structures between the two components,which will eventually reduce the performance of such nanocomposites.Choosing metallic Sn(β-Sn),which belongs to IV group and supports surface plasmon as well,to combine with RGO is therefore a promising proposal to form a hybrid structure without the electronic defects.As a result,such β-Sn-RGO nano-hybrid structure could achieve stronger near-field enhancement effect.In this dissertation,the research on preparation and surface plasmon performance of cubic β-Sn nanoparticles has been firstly carried out.Then,two different β-Sn-RGO nanohybrid structures,attached structure and core-shell structure,have been prepared,respectively.Afterwards,the surface plasmon performance of both structures have been demonstrated.And the main results are as follows:1.The β-Sn nanoparticles with cubic structure have been successfully prepared by three methods,which are oil bath method,high temperature wet chemical method and seed crystal method,respectively.The optical characterizations and finite element simulations indicate that the size-dependent surface plasmon performance of cubic β-Sn nanoparticles agree well with the classical Mie theory.The quadrupole resonance mode of β-Sn will appear when the size increases up to 50 nm,and all of the surface plasmon resonance peaks will red-shift with the increasing of size.In addition,the average near-field enhancement factor((?))changes with the increasing of the size abiding by different ways.In the wavelength range of 200-500 nm,(?) decreases with the size and the maximum value can be up to 6.4.While in the longer wavelength range of 500-800 nm,(?)increases with the size,which can be due to the red-shifting of the resonance peaks,and the maximum value is only 1.5.2.The β-Sn/RGO nano-attached structure has been successfully prepared by a solvothermal reduction method.The optical characterizations and finite element simulations indicate that comparing with the pure β-Sn nanoparticles,the attached structure shows the surface plasmon resonance peaks with longer wavelength,which can be assigned to the coupling between the β-Sn nanoparticles and RGO.Furthermore,the surface enhanced Raman scattering experiments reveal that the β-Sn/RGO nano-attached structure could enhance the Raman signals from rhodamine molecules with an average enhancement factor of 1.5 under the excitation of 633 nm.In addition,the (?) increases with the size of the β-Sn nanoparticles in the beginning,after reaching the maximum value of 2.6 with size of 180 nm,the (?) start to decrease with the size increasing.On the other hand,the distribution of β-Sn nanoparticles affects the enhancement as well.The finite element calculations indicate that the (?) dramatically increase with the decreasing of the gap of the β-Sn dimer with size of 40 nm.The value is about 1.4 when the gap is 20 nm and the maximum (?) value of 3000 can be reached when the gap is 0.3.The β-Sn@RGO nano-core-shell structure has been successfully prepared by an electrostatic self-assembly method.The optical characterizations and finite element simulations indicate that the surface plasmon resonance peaks will keep red-shifting and broadening when the size of β-Sn core or the thickness of RGO shell increase.Furthermore,the size-dependent (?) changings on the core and shell are different.The (?) increases with the size of the β-Sn core in the beginning,and then drops after reaching the maximum.While it decreases monotonously with the increasing of RGO thickness.The maximum (?) value of 5.9 can be reached when the β-Sn@RGO nano-core-shell structure has been optimized with core and shell of 80 and 2 nm,respectively.