Microstructural and Optical Absorption Properties of Cu—MgF2 Nanoparticle Cermet Film

We examine the microstructural and optical absorption spectra of 10-30vol% Cu-MgF2 nanoparticle cermet films prepared by co-evaporation in vacuum.The results show that the Cu-MgF2 cermet films are mainly composed of the amorphous MgF2 matrix with embedded fcc Cu nanoparticles of average size 12-24nm.The results also show that the optical absorption of the films decreases as the wavelength increases in the range of 200-800nm.The surface plasmon resonance absorption peaks of Cu nanoparticles in 10,20 and 30vol% Cu-MgF2 films appear at 578,588 and 606 nm,respectively.The interband transition absorption of Cu starts from 590nm downwards.Based on the Maxwell-Garnett theory,the experimental optical absorption properties of the films have been quantitatively evaluated.     

Microstructure and optical absorption of Au-MgF2 nanoparticle cermet films

The microstructure and optical absorption of Au-MgF2 nanoparticle cermet films with different Au contents are studied. The microstructural analysis shows that the films are mainly composed of the amorphous MgF2 matrix with embedded fcc Au nanoparticles with a mean size of 9.8-21.4nm. Spectral analysis suggests that the surface plasma resonance （SPR） absorption peak of Au particles appears at λ=492-537nm. With increasing Au content, absorption peak intensity increases, profile narrows and location redshifts. Theoretical absorption spectra are calculated based on Maxwell-Garnett theory and compared with experimental spectra.     

Optical Properties of Plasmon Resonances with Ag/SiO2/Ag Multi-Layer Composite Nanoparticles

Optical properties of plasmon resonance with Ag/SiO2/Ag multi-layer nanoparticles are studied by numerical simulation based on Green＇s function theory. The results show that compared with single-layer Ag nanoparticles, the multi-layer nanoparticles exhibit several distinctive optical properties, e.g. with increasing the numbers of the multi-layer nanoparticles, the scattering efficiency red shiRs, and the intensity of scattering enhances accordingly. It is interesting to find out that slicing an Ag-layer into multi-layers leads to stronger scattering intensity and more ＂hot spots＂ or regions of stronger field enhancement. This property of plasmon resonance of surface Raman scattering has greatly broadened the application scope of Raman spectroscopy. The study of metal surface plasmon resonance characteristics is critical to the further understanding of surface enhanced Raman scattering as well as its applications.     

Surface Plasmon Resonance and Raman Scattering Activity of the Au/AgxO/Ag Multilayer Film

The nanostructured Au/AgxO/Ag sandwich multilayer films on quartz substrates are prepared by the magnetron sputtering method. The morphology, plasmon resonance and surface enhanced Raman scattering （SERS） activi- ties of the multilayer films are studied. The resonant absorption wavelength of localized surface plasmon is tuned in a wide range from 618nm to 993nm by controlling the density of nanoparticles of Au and Ag. The SERS activity of the Au/AgxO/Ag multilayer films are enhanced over -10 times compared with those of bare Ag and bare Au films. These properties may find a potential application in biosensor and bioimaging.     

Photoinduced Reorientation Process and Nonlinear Optical Properties of Ag Nanoparticle Doped Azo Polymer Films

Azobenzene polymer films doped with and without Ag nanoparticles are prepared. The photoinduced reorientation process is investigated by using an Nd：YVO4 pump beam at 532 nm and a low semiconductor laser beam at 650 nm. The reorientation rate of azo polymer films is enhanced in the presence of Ag nanoparticles, and the rate of the azo polymer film with Ag concentration of 2.2 μg/ml is larger than that of the azo polymer films with Ag concentrations of 1.1 μg/ml and 4.4 μg/ml. The third-order nonlinear optical properties of the Ag/azo composite film are obtained by the Z-scan technique at a wavelength of 532 nm, and the measured nonlinear refractive index is 9.258×10-9 esu. It is shown that the main mechanisms involved in the large nonlinear optical responses come from the local field enhancement of Ag nanoparticles and the nonlinear effect of the azo polymer matrix.     

Influence of Ambient Atmosphere on the Plasmon Resonance Absorption of Ag／SiOx（0≤x≤2） Nanocomposite Film

Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si-containing matrices were prepared by radio frequency magnetron co-sputtering deposition.We studied the influence of ambient atmosphere during the preparation and heat-treatment of Ag/SiOx(0≤x≤2) nanocomposite film on its optical absorption properties.We found that the plasmon resonance absorption peak shifts to shorter wavelengths with the increasing oxygen content in the SiOx matrix.The analysis indicates that the potential barrier between Ag nanoparticles and SiOx matrix increases with the increasing x value,which will induce the surface resonance state to shift to higher energy.The electrons in the vicinity of the Fermi level of Ag nanoparticles must absorb more energy to be transferred to the surface resonance state with the increasing x value.It was also found that the plasmon resonance absorption peaks of the samples annealed in different ambient atmospheres are located at about the same position.This is because the oxidation surface layer is dense enough to prevent the oxygen from peretration into the sample to oxidize the silicon in the inner layer.     

Silver-Doping Induced Lattice Distortion in TiO2 Nanoparticles

The Ag-doping effects on Ti02 nanoparticles are investigated by means of x-ray diffraction （XRD） and Raman scattering spectroscopy. XRD and Raman results indicate that Ag-doping stabilizes the rutile phase in TiO2. We find an Ag-doping induced lattice expansion in both anatase and rutile phases. The Ag-doping has different influences on the lattice distortion for anatase and rutile phases, that is, the e/a-value for the anatase phase decreases with 0.5% Ag-doping and then increases with 1~ Ag-doping while that for the rutile phase shows a gradual increase with increasing Ag-doping. We have ascribed the different variations of lattice distortion due to Ag-doping to the change of interracial interaction between the anatase and rutile phases induced by different Ag concentrations.     

Au Films Composed of Nanoparticles Fabricated on Liquid Surfaces for SERS

A series of Au films with different nominal deposition thickness d were fabricated on ionic liquid surfaces by thermal evaporation at room temperature,taken as surface-enhanced Raman scattering(SERS) substrates.Au atoms deposited on the liquid surfaces can diffuse and aggregate randomly and eventually form films with ramified structure,which consist of nanoparticles(NPs).There are amounts of ultrasmall(～1 nm or smaller) nanogaps among the Au NPs,which can dramatically enhance Raman signal.Raman spectra of R6G were investigated with the assistance of the Au films.The results indicate that the Au films with higher thickness possess better SERS performance when 5.0 ≤d ≤30.0 nm.A random distribution model of Au NPs was used in the finite-difference time-domain method and the simulation results are in good agreement with the experimental findings.     

Large Third-Order Optical Nonlinearity of Cadmium Sulphide Nanoparticles Embedded in Polymer Thin Films

A simple method for synthesis of well dispersed cadmium sulphide nanoparticles embedded in a polyethylene glycol matrix （PEG 400） in thin film form is presented. The large blue shift of the band gap energy of the CdS nanoparticles compared to the bulk semiconductors is observed via UV-vis absorption spectra. Photoluminescence spectra of CdS nanocomposite films show that the emission peaks shift towards the longer wavelength with the increase of annealing temperature. Transmission electron microscopic images as well as Raman scattering studies confirm the CdS nanometer size particle formation within the polymer matrix. The particle size is about 8 nm. Selected area electron diffraction （SAED） shows the cubic zinc blende polycrystalline rings. Third-order optical nonlinearity of the CdS nanopartieles embedded in polymer thin films is studied with the Z-scan technique under 1064 nm excitation. The results show that the CdS nanocomposite film exhibits negative nonlinear refraction index and positive absorption coefficient. The film shows large optical nonlinearity, and the magnitude of the third-order nonlinear susceptibility of the film is calculated to be 1.73 × 10^-9 esu. The corresponding mechanism is discussed.     

Optical constants and their dispersion of Ag-MgF_2 nanoparticle composite films

Ag-MgF_2 composite films with different Ag fractions were prepared through a co-evaporation method. Microstructure analysis shows that the films are composed of amorphous MgF_2 matrix and embedded fcc-Ag nanoparticles. The optical constants and their dispersion of the films, within the wavelength range of 250 - 650 nm, were measured by reflecting spectroscopic ellipsometry. The maximum of the imaginary part ε~″ of the complex dielectric permittivity attributing to the surface plasmon resonance polarization of the Ag nanoparticles in an Ag-MgF_2 film, and the tangent of the phase-shift angle δ resulting from the dielectric loss of the film, occur at λ= 435 nm and λ= 420 nm, respectively. Based on Maxwell-Garnett effective medium theory, the experimentally observed dispersion spectra were reasonably described.     

Optical constants and their dispersion of Ag-MgF2 nanoparticle composite films

Ag-MgF2 composite films with different Ag fractions were prepared through a co-evaporation method.Microstructure analysis shows that the films are composed of amorphous MgF2 matrix and embedded fcc-Ag nanoparticles. The optical constants and their dispersion of the films, within the wavelength range of 250 - 650 nm, were measured by reflecting spectroscopic ellipsometry. The maximum of the imaginary part ε" of the complex dielectric permittivity attributing to the surface plasmon resonance polarization of the Ag nanoparticles in an Ag-MgF2 film, and the tangent of the phase-shift angle δ resulting from the dielectric loss of the film, occur at λ = 435 nm and λ = 420 nm, respectively. Based on Maxwell-Garnett effective medium theory, the experimentally observed dispersion spectra were reasonably described.     

Cu-MgF2复合纳米金属陶瓷薄膜的电导特性研究

用射频磁控共溅射法制备了Cu体积分数分别为10%，15%，20%和30%的Cu-MgF₂复 合金属陶 瓷薄膜.用x射线衍射、x射线光电子能谱和变温四引线技术对薄膜的微结构、组分及电导特 性进行了测试分析.微结构分析表明：制备的Cu-MgF₂复合薄膜由fcc-Cu晶态纳 米微粒镶嵌 于主要为非晶态的MgF₂陶瓷基体中构成，Cu晶粒的平均晶粒尺寸随组分增加从1 1.9nm增 至17.8nm.50—300K温度范围内的电导测试结果表明：当Cu体积 关键词： 2复合纳米金属陶瓷膜')" href="#">Cu-MgF₂复合纳米金属陶瓷膜 微结构 组分 电导特性 激活能 渗透阈     

银纳米粒子自组装复合LB膜的结构与性质

纳米粒子的自组装和有序组装膜的结构与性质近年来受到了人们的广泛关注,纳米粒子的表面结构与性质对由其组装成的有序膜的结构与性质有直接的影响。文章报道了利用自组装技术制备的银纳米粒子与双亲有机分子的单层和多层复合LB膜,通过吸收光谱和表面增强拉曼光谱研究了银纳米粒子与吸附分子间的相互作用,探讨了复合膜的成膜特性及银纳米粒子的拉曼增强特性。十八胺/银粒子复合LB膜的吸收光谱及拉曼光谱显示,十八胺分子与银纳米粒子表面的活位通过NH₂中的氮原子以复合体的形式结合;同时,在激发光的作用下复合体可能存在光催化过程。根据银粒子复合LB膜的实验结果,十八胺和十八酸之间的反应产物在复合膜中起空间位阻作用,与银粒子表面的相互作用较弱。     

SERS activity of carbon nanotubes modified by silver nanoparticles with different particle sizes

A two-dimensional (2D) surface-enhanced Raman scattering (SERS) substrate is fabricated by decorating carbon nanotube (CNT) films with Ag nanoparticles (AgNPs) in different sizes, via simple and low-cost chemical reduction method and self-assembling method. The change of Raman and SERS activity of carbon nanotubes/Ag nanoparticles (CNTs/AgNPs) composites with varying size of AgNPs are investigated by using rhodamine 6G (R6G) as a probe molecule. Meanwhile, the scattering cross section of AgNPs and the distribution of electric field of CNTs/AgNPs composite are simulated through finite difference time domain (FDTD) method. Surface plasmon resonance (SPR) wavelength is redshifted as the size of AgNPs increases, and the intensity of SERS and electric field increase with AgNPs size increasing. The experiment and simulation results show a Raman scattering enhancement factor (EF) of 10⁸ for the hybrid substrate.     

Ag-MgF2复合纳米金属陶瓷薄膜的渗透阈研究

介绍了几种计算纳米金属颗粒镶嵌于陶瓷基体中而形成的复合纳米金属陶瓷薄膜渗透阈的理论方法，分析了理论方法中所运用模型的特点及其精度.并将Landauer有效介质理论和Priou渗透阈理论应用于Ag-MgF₂复合纳米金属陶瓷薄膜的渗透阈计算，所得值分别为0.08和0.14(Ag的体积分数)，按Priou渗透阈理论计算的结果与实验结果相符.最后讨论了影响复合金属陶瓷薄膜体系渗透阈的主要因素. 关键词： 2复合纳米金属陶瓷薄膜')" href="#">Ag-MgF₂复合纳米金属陶瓷薄膜 渗透阈理论 渗透阈     

SERS study of Ag nanoparticles electrodeposited on patterned TiO2 nanotube films

In this work, Ag nanoparticles (NPs) were deposited on patterned TiO₂ nanotube films through pulse‐current (PC) electrodeposition, and as a result patterned Ag NPs films were achieved. Scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X‐ray diffraction (XRD) were used, respectively, to study the morphology, uniformity, and phase structure of the patterned Ag NP films. The size and density of the as‐deposited Ag NPs could be controlled by changing the deposition charge density, and it was found that the patterned Ag NP films produced under a charge density of 2.0 C cm⁻² gave intense UV–vis and Raman peaks. Two‐dimensional surface‐enhanced Raman scattering (SERS) mapping of rhodamine 6G (R6G) on the patterned Ag NP films demonstrated a high‐throughput, localized molecular adsorption and micropatterned SERS effect. Copyright © 2010 John Wiley & Sons, Ltd.     

密排银颗粒薄膜的制备及其SERS应用

银纳米颗粒通过自组装形成二维结构薄膜具有独特的光学性质,其提供的大量“热点”使其成为优越的表面增强拉曼散射(Surface enhanced Raman Scattering,SERS)基底.本文采用水/正己烷界面上自组装的方法得到了由密排的银纳米颗粒构成的薄膜,并以Rhodamine 6G为探针分子,比较了不同尺寸银...     

Controlling SERS intensity by tuning the size and height of a silver nanoparticle array

It is demonstrated that the surface-enhanced Raman scattering (SERS) intensity of R6G molecules adsorbed on a Ag nanoparticle array can be controlled by tuning the size and height of the nanoparticles. A firm Ag nanoparticle array was fabricated on glass substrate by using nanosphere lithography (NSL) combined with reactive ion etching (RIE). Different sizes of Ag nanoparticles were fabricated with seed polystyrene nanospheres ranging from 430 nm to 820 nm in diameter. By depositing different thicknesses of Ag film and lifting off nanospheres from the surface of the substrate, the height of the Ag nanoparticles can be tuned. It is observed that the SERS enhancement factor will increase when the size of the Ag nanoparticles decreases and the deposition thickness of the Ag film increases. An enhancement factor as high as 2×10⁶ can be achieved when the size of the polystyrene nanospheres is 430 nm in diameter and the height of the Ag nanoparticles is 96 nm. By using a confocal Raman mapping technique, we also demonstrate that the intensity of Raman scattering is enhanced due to the local surface plasmon resonance (LSPR) occurring in the Ag nanoparticle array.