Synthesis and Largely Enhanced Nonlinear Refraction of Au@Cu<Subscript>2</Subscript>O Core-Shell Nanorods

Au@Cu₂O core-shell nanorods with tunable thickness of Cu₂O shell were synthesized and their linear and nonlinear optical responses were investigated. Two transverse plasmon resonance peaks were observed when the Au nanorods were coated with Cu₂O shells, which were adjusted by the Cu₂O shell thickness. The nonlinear absorption of the Au@Cu₂O nanorods is enhanced by 5 times at the longitudinal plasmon resonance wavelength compared with that of bare Au nanorods. More intriguingly, largely enhanced nonlinear refraction and suppressed nonlinear absorption at the transverse plasmon resonance wavelength were observed in the Au@Cu₂O nanorods. Our findings indicate the existence of strong local field enhancement at the interface between the Au core and the Cu₂O shell, which would provide a promising strategy in designing plasmonic nonlinear nanodevices with good nonlinear figures of merit.     

纳米半球壳结构光学调谐特性分析

利用离散偶极近似法,理论研究了颗粒几何结构参数和物理特性对金纳米半球壳颗粒消光特性的影响.结果表明,随着壳层厚度的增大,消光共振波长先发生蓝移而后再红移,共振波长转向时对应的壳层厚度随内核材料及外界环境介电常数和颗粒间距的增大而增大.利用等离激元杂化理论和相位延迟效应对该现象进行了解释.     

银纳米粒子的消光光谱与粒子形状的关系

先利用离散偶极子近似(Discrete Dipole Approximation,DDA)的方法,分别计算置于空气中的球形、不同长径比的椭球形和棒形银纳米粒子的消光光谱.计算结果表明:球形纳米粒子仅存在单个等离子体共振尖峰;而椭球状和棒状粒子则存在横向和纵向两个等离子体共振峰;并且横向峰的变化不甚明显,而纵向峰会随粒子长径比的增大而线性地红移.再结合Gans的解析理论,分析等离子体共振的机理,并研究纵向等离子体共振峰随着粒子长径比的增大而红移的现象.     

Investigation on composite Au/TiO_2 nanoparticles (Ⅰ)——Synthesis and characterization

Nanometer sized Au/TiO\-2 particles were synthesized by irradiation of a HAuCl\-4 solution containing colloidal TiO\-2 with light of wavelength (λ)>330 nm. The absorption maximum attributed to the surface plasmon band of gold was observed at 540 nm, a red shift of about 20 nm from the position in aqueous solution. The Au clusters are situated on the surface of TiO\-2 in terms of microcrystallite, which was confirmed by HRTEM, EDS and XRD. The electronic interfaction between the metal and the suport was discussed.     

Growth and optical absorption properties of silver nanorod arrays in porous anodic aluminum oxide templates

Silver nanorod arrays have been fabricated by alternat-ing current(AC) and pulsed direct current(DC) electrodeposition in porous anodic aluminum oxide(AAO) templates with controlled pore diameters of 19,38,and 65 nm,respectively.The variation of their optical absorption properties with the incident angle and the nanorods length(corresponding to the electrodeposition time) has been investigated.Optical absorption spectra show that the posi-tion of longitudinal surface plasmon resonance(LSPR) peak has a small blueshift with the increase of incident angle of the excitation light.While the aspect ratio of the nanorods increases,the position of LSPR peak first redshifts and then blueshifts to a certain wave-length.Furthermore,the position of LSPR peak can be tuned,ranging from 550 nm to 900 nm,which makes it possible to cou-ple various wavelength of excitation source to assist radiative en-ergy transfer to the acceptor.     

中空银纳米球的制备及其性能研究

新型的金属纳米粒子因为独特的由表面等离子体共振诱导(SPR)的光学性质和很多的潜在应用而受到社会广泛的关注。在具有SPR效应的贵金属纳米粒子中,中空纳米结构有一个很高的散射系数,其共振频率通过改变中空核的尺寸和壳的厚度可以很容易地被控制。本论文中拟采用电化学方法结合电偶置换法在高定向热解石墨(HOPG)及金膜表面制备不同尺寸具有中空结构的银纳米阵列,研究了中空银纳米阵列的局域表面等离子效应(L-SPR),为其在SPR定性和定量研究中的应用提供理论指导。     

修正偶应力理论层合薄板自由振动模型及尺度效应

通过引入各向异性的细观尺度复合材料层合板的本构方程,将各向同性修正偶应力理论推广到各向异性,基于虚功原理首次建立了复合材料层合板新修正偶应力理论的自由振动模型.该理论包含不同的两个材料细观参数,偶应力曲率应变不对称.但是,用于各向同性材料与原修正偶应力理论等价,为了便于工程应用,建立了只含一个细观材料参数的偶应力层合薄板理论弯曲和振动的简化模型.算例表明建立的偶应力层合薄板模型能用于分析层合板的自由振动尺度效应.     

Cu-MgF_2纳米金属陶瓷薄膜的微结构及吸收光谱特性研究

对用蒸发技术制备的Cu -MgF2 纳米金属陶瓷薄膜微结构及吸收光谱特性进行了研究。微结构分析表明薄膜由fcc -Cu纳米晶粒镶嵌于主要呈非晶态的MgF2 基体中所组成 ,晶粒的平均粒度约为 1 4～ 1 6nm。Cu -MgF2 纳米金属陶瓷薄膜在 2 0 0～ 80 0nm波段内的吸收光谱表明 :随着波长增加 ,吸收减小 ;Cu纳米晶粒的表面等离子共振吸收峰出现于 560nm处 ;短波长区呈现较强的Cu的带间跃迁吸收。用三维弥散系统的Maxwell-Garnett理论对Cu -MgF2 复合体系的实验吸收光谱特性作出了解释。     

低温固相法制备Cu2O纳米晶

本论文基于绿色化学的思想，运用低温固相反应实验技术成功地实现了氧化亚铜纳米晶的制备。用X—射线粉末衍射(XRD)和透射电镜(TEM)对所得产物进行了表征，并对氧化亚铜棒状结构的形成机理做了初步探讨。     

Investigation on composite Au /TiO2 nanoparticles (I)

Nanometer sized Au/TiO₂, particles were synthesized by irradiation of a HAuCl₄ solution containing colloidal TiO₂ with light of wavelength (λ) > 330 nm. The absorption maximum attributed to the surface plasmon band of gold was observed at 540 nm, a red shift of about 20 nm from the position in aqueous solution. The Au clusters are situated on the surface of TiO₂ in terms of microcrystallite, which was confirmed by HRTEM, EDS and XRD. The electronic interfaction between the metal and the suport was discussed.     

Microstructure and optical absorption properties of Au/NiO thin films

Au nanoparticles dispersed NiO composite films were prepared by a chemical solution method. The phase structure, microstructure, surface chemical state, and optical absorption properties of the films were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Uv-vis spectrometer. The results indicate that Au particles with the average diameters of 35–42 nm are approximately spherical and disperse in the NiO matrix. The optical absorption peaks due to the surface plasmon resonance of Au particles shift to the shorter wavelength and intensify with the increase of Au content. The bandwidth narrows when the Au content increases from 8.4wt% to 45.2wt%, but widens by further increasing the Au content from 45.2wt% to 60.5wt%. The band gap E_g increases with the increase of Au contents from 8.4wt% to 45.2wt%, but decreases by further increasing the Au content.     

非离子表面活性剂辅助液相合成Cu2O纳米线及其结构和性能研究

首次提出了一种利用非离子表面活性剂聚乙二醇(分子量:20 000)(PEG Mw20 000)为助生长剂,通过还原剂水合肼(N2H4)还原新生成的Cu(OH)2大规模合成半导体Cu2O纳米线的新方法.用TEM和HRTEM研究了所合成的Cu2O纳米线的形貌和结晶性,并用FT-IR红外吸收谱研究了纳米线的红外吸收特性,用纳米材料的量子效应和表面效应对FT-IR红外吸收谱中的蓝移现象作了解释.讨论了表面活性剂PEG的作用,由此详细研究了Cu2O纳米线的生长机制,指出Cu2O纳米线是由于吸附在PEG长链上的Cu2O纳米粒子通过彼此间的相互连接沿着PEG长链自组装而形成的.     

Size-dependent optical properties of Au nanorods

In the fast evolving field of nanoscience and nanotechnology,where size and shape are crucial in deciding the optoelectronic properties of nanomaterials,the understanding of size and shape dependent behavior is of direct relevance to device applications.Present study reports the synthesis of Au nanorods with well controlled aspect ratios,and the influence of the aspect ratio on the surface enhanced Raman scattering(SERS) activity using crystal violet(CV) as the probe molecule.The influence of pH and the concentrations of reducing agent and Ag ions in controlling the aspect ratio of gold nanorods are also investigated.The structural and optical properties of the synthesized samples have been characterized by transmission electron microscopy(TEM) and UV-visible absorption spectroscopy.The nonlinear optical(NLO) transmission of the Au nanorods investigated using the open aperture Z-scan technique revealed the absorption saturation followed by an optical limiting behavior,which may find potential applications in optoelectronic nanodevices.     

Synthesis and characterization of Au@Pt nanoparticles

Aucore-Ptshell （Au@Pt） nanoparticles were synthesized at room temperature by reducing K2PtCl6 with hydrogen in the solution containing Au colloids and polyvinylpyrrolidone （PVP）. The particles obtained were characterized with UV-Vis, TEM and XPS techniques. UV-Vis spectra show that the surface plasmon absorption feature of Au colloids is significantly reduced with increasing the amount of reduced Pt. TEM images that the metals are found always appear as spherical nanoparticles and their sizes grow apparently due to the reduction of PtCl6^2- ions, indicating that Pt is deposited from solution onto Au particle surface and forms a Pt-layer with uniform thickness. In the XPS spectra, the signals of Au metal decrease due to the reductive deposition of Pt on the surface of the Au colloids. UV-Vis and XPS data are consistent in showing that when the amount of Pt in the AuPt colloids is increased to reach an overall atomic ratio of Pt/Au=2, the Pt deposits form a shell covering completely the surface of Au particles, demonstrating the core-shell structure of the synthesized AuPt particles.     

Au@SiO2 core/shell nanoparticle-decorated TiO2 nanorod arrays for enhanced photoelectrochemical water splitting

To improve the separation efficiency of photoinduced charge carries,Au@SiO2nanoparticles(NPs)with core–shell structure were loaded onto the surface of TiO2nanorods grown on fluorine-doped tin oxide substrate by a facile two-step process.The resulted Au@SiO2/TiO2photoanodes were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,as well as photoelectrochemical measurements.Compared with pristine TiO2nanorod film,the Au@SiO2/TiO2films showed remarkable enhancement in photoelectrochemical water splitting,with incident photonto-current conversion efficiency increasing from 31%to37%at 380 nm at 0.7 V versus saturated calomel electrode.This could be interpreted by the effect of metallic surface plasmon resonance of Au@SiO2NPs,which would generate an intense electromagnetic field with spatially nonhomogenous distributed intensity.As a result,the charge carriers generated in the near-surface region of TiO2nanorods could be easily separated.This modification method based on the effect of metallic surface plasmon resonance for promoted charge carrier separation provides a promising way to develop semiconductor photoelectrodes with high solar water-splitting performance.     

Au, Ag and Au:Ag colloidal nanoparticles synthesized by pulsed laser ablation as SERS substrates

Chemically pure colloidal suspensions of gold and silver nanoparticles were synthesized using pulsed laser ablation.The dependence of laser fl uence on the surface plasmon characteristics of the nanoparticles was investigated.Au:Ag colloidal suspensions were prepared by mixing highly monodisperse Au and Ag nanocolloids.The plasmon band of these mixtures was found to be highly sensitive to Au:Ag concentration ratio and wavelength of the laser beam used in the ablation process.The Au:Ag mixture consists of almost spherical shaped nanostructures with a tendency to join with adjacent ones.The surface enhanced Raman scattering activity of the Au,Ag and Au:Ag colloidal suspensions was tested using crystal violet as probe molecules.Enhancement in Raman signal obtained with Au:Ag substrates was found to be promising and strongly depends on its plasmon characteristics.     

Magnetically separable and visible light-active Ag/NiCo_2O_4 nanorods prepared by a simple route for superior photodegradation of atrazine in water

Atrazine(ATZ) is a known herbicide used in agriculture and caused many concerns according to its toxicity.Herein,we have prepared NiCo_2 O_4 nanorods that can work as a photocatalyst under visible light exposure by Ag loading through a simple route.The characterizations revealed the role of Ag for improving the structural,optical and optoelectronic properties of the produced photocatalyst.The Ag loading with 5 wt% confirms the minimization of the bandgap from 3.6 down to 2.57 eV with enhanced visible light absorption and sustaining the magnetic properties.The Ag/NiCo_2 O_4 nanorods showed a superior photodegradation of ATZ within 20 min at2.0 g L~(-1) with excellent recyclability.The enhancement of the photocatalytic activity is referred to the local surface plasmon resonance of Ag-loaded photocatalyst.This reduces the electron-hole recombination and outperforms the unloaded sample.This work is highlighting the application of magnetically separable spinel photocatalysts for the removal of herbicides and water remediation.     

A multiple-labelling method for cells using Au nanoparticles with different shapes

An important and difficult issue is simultaneously identifying the detailed locations of various molecules on the cell surface, as this identification requires a synergistic effect between more than one molecule in a living cell. Au nanoparticles (NPs) with different shapes can be readily recognised under low vacuum scanning electron microscopy (lvSEM). Anisotropic Au nanorods (NRs) possess unique surface plasmon resonance (SPR) properties, which can be further utilised for two photon luminescence (TPL) and other optical imaging techniques. In this paper, Au NRs and Au nanooctahedra (Au NOs) are introduced as biomarkers for ICAM-1 and Integrin β1. Combined with the advantages of lvSEM, this multiple-labelling method is a new method for studying the interactions between specific, functional molecules.     

铜镀层对IC引线框架表面抗氧化失效的作用

研究了在铜合金表面电镀纯铜层保护膜对铜合金引线框架氧化失效的影响.研究发现,电镀纯铜层后,纯铜层氧化速率较高,氧化膜较厚,然而,由于纯铜层的阻挡作用,可以使氧化只发生在纯铜层上,减少CuO的生成.当铜合金表面的电镀纯铜层厚度超过一个临界值,表面电镀纯铜处理可以明显改善材料的耐氧化剥离性.表面电镀前的铜合金氧化膜结构为CuO/Cu2O/Cu.电镀纯铜层后,氧化膜结构变为Cu2O/Cu,当氧化膜主要由Cu2O构成时,氧化膜结合强度较高.     

金/二氧化硅中空核壳纳米球的制备与表征

采用水热反应法和正硅酸乙酯水解法制备出核壳结构的Au/C纳米球颗粒以及夹层结构的Au/C/SiO<,2>纳米球颗粒,在空气中锻烧将Au/C/SiO<,2>夹层结构中的碳层除去,得到内部带有可移动纳米金核、壳层厚度约为20 nM的中空Au/SiO<,2>纳米球颗粒.用透射电子显微镜对所制得的纳米微球的形貌进行表征,并用红...