Probing of Ultrafast Plasmon Dynamics on Gold Bowtie Nanostructure Using Photoemission Electron Microscopy

We report the direct imaging of plasmon on the tips pulses and probing of ultrafast plasmon dynamics by of nano-prisms in a bowtie structure excited by 7 fs laser combining the pump-probe technology with three-photon photoemission electron microscopy. Different photoemission patterns induced by the plasmon effect are observed when the bowties are excited by s- and p-polarized femtosecond laser pulses. A series of images of the evolution of local surface plasmon modes on different tips of the bowtie are obtained by the time-resolved three-photon photoemission electron microscopy, and the result discloses that plasmon excitation is dominated by the interfer- ence of the pump and probe pulses within the first 13 fs of the delay time, and thereafter the individual plasmon starts to oscillate on its own characteristic resonant frequencies.

Electron beam evaporated gold doped tungsten oxide nanostructured films for sensor applications

Gas sensors play a vital role in monitoring environmental pollution for human health,safety,and the detection of various gasses in the environment.Nanostructured metal oxide thin films have been widely used in sensor applications owing to their unique properties.In this study,pure and gold(Au)doped nanostructured tungsten trioxide(WO_(3))films were deposited on glass substrates by electron beam evaporation at room temperature.The microstructure of the WO_(3) films changed from nanoflakes to nanorods upon variation of the wt%of Au.The sensing properties of WO_(3) based nanostructure films were measured using a computer-controlled system.The gas sensing results showed that the Au-doped WO_(3) films exhibited a higher sensitivity than the undoped films.The 15 wt%Au-doped WO_(3) nanostructure films showed high sensitivity towards ethanol and the response(sensitivity)value was 89.The response and recovery times for 15 wt%Au-doped WO_(3) were 8 and 10 s,respectively.

High stability of the goldalloy fullerenes:A density functional theory investigation of M_(12)@Au_(20)(M=Na,Al,Ag,Sc,Y,La,Lu,and Au) clusters

Discovering highly stable metal fullerenes such as the celebrated C 60 is interesting in cluster science as they have potential applications as building blocks in new nanostructures.We here investigated the structural and electronic properties of the fullerenes M 12 @Au 20（M=Na,Al,Ag,Sc,Y,La,Lu,and Au）,using a first-principles investigation with the density functional theory.It is found that these compound clusters possess a similar cage structure to the icosahedral Au 32 fullerene.La 12 @Au 20 is found to be particularly stable among these clusters.The binding energy of La 12 @Au 20 is 3.43 eV per atom,1.05 eV larger than that in Au 32.The highest occupied molecular orbital-lowest unoccupied molecular orbital（HOMO-LUMO） gap of La 12 @Au 20 is only 0.31 eV,suggesting that it should be relatively chemically reactive.

基于聚苯乙烯模板的金纳米碗结构的制备及二次电子发射特性

降低金属微波部件二次电子发射系数(SEY)是提高其微放电阈值的常用方法,以二维聚苯乙烯(PS)胶体晶体为模板、二氧化钛(TiO_(2))为过渡层,采用电化学沉积法在镀银铝合金表面制备金纳米碗结构涂层,利用金纳米碗结构吸收和捕获二次电子,降低表面二次电子发射系数。结果表明:当镀金液中亚硫酸钠(Na_(2)SO_(3))浓度为140 g/L、乙二胺四乙酸二钠(Na_(2)EDTA)浓度为5 g/L、氯金酸(HAuCl_(4))浓度为10 g/L、沉积时间为60 min时,金纳米碗结构涂层的二次电子发射系数最大值为1.62,与初始镀银铝合金样片相比,其SEY最大值降低了26.4%。本研究为抑制微放电效应提供了一种新的表面处理方法。

Synthesis, properties and applications of one- and two- dimensional gold nanostructures

The controlled synthesis of gold nanocrystals has been the subject of intensive studies for decades because the properties and functions of gold nanomaterials are highly dependent on their particle size, shape, and dimensionality. Especially, anisotropic gold nanocrystals, such as nanowires, nanobelts, nanoplates and nanosheets, have attracted much attention due to their striking properties and promising applications in electronics, catalysis, photonics, sensing and biomedicine. In this review, we will summarize the recent developments of one- dimensional （1D） and two-dimensional （2D） gold nanostructures. Various kinds of synthetic methods for preparation of these 1D and 2D gold nanocrystals will be described. Moreover, we will also briefly introduce the properties and potential applications of these 1D and 2D gold nanocrystals.

Growth of Anisotropic Platinum Nanostructures Catalyzed by Gold Seed Nanoparticles

This paper reports an effective method for the synthesis of platinum nanostructures with anisotropic morphologies by decomposition of platinum dichloride in oleylamine at intermediate temperatures catalyzed by gold seed nanoparticles.A small quantity of spherical gold nanoparticles formed in situ was used to trigger the nucleation and anisotropic growth of the Pt nanocrystals.By varying the amount of gold seed nanoparticles,porous fl ower-like,irregular polyhedron-shaped,multi-branched rod shaped,and caterpillar-like Pt nanostructures were produced in high yields at 190240°C in reaction times of a few minutes.Control of morphology under different conditions has been systematically studied and a kinetically controlled induced growth mechanism has been proposed.

Nanostructured gold films exhibiting almost complete absorption of light at visible wavelengths

Nanostructured known to exhibit properties metal surfaces have been that deviate from that of the bulk material. By simply modifying the texture of a metal surface, various unique optical properties can be observed. In this paper, we present a simple two step electrochemical process combining electrodeposition and anodization to generate black gold surfaces. This process is simple, versatile and up-scalable for the production of large surfaces. The black gold films have remarkable optical behavior as they absorb more than 93% of incident light over the entire visible spectrum and also exhibit no specular reflectance. A careful analysis by scanning electron microscopy reveals that these unique optical properties are due to their randomly rough surface, as they consist in a forest of dendritic microstructures with a nanoscale roughness. This new type of black films can be fabricated to a large variety of substrates, turning them to super absorbers with potential applications in photovoltaic solar cells or highly sensitive detectors and so on.

Facile Synthesis of Multi-Branched Gold Nanostructures through a TBAB-Assisted Route in Aqueous Solution and Their SERS Property

Facile synthesis of multi-branched gold nanostructures by using the tetrabutyl ammonium bromide （TBAB） as a capping agent is described. The reaction is carried out in a one-step process at mild temperature. Gold nanostructures with more than six sharp branches ranging from 70 to 130 nm in length are synthesized in high yield. It is proposed that the relative weak adsorption capacity of TBAB leads to the incompletely covered gold surface and the growth of nanoparticles occurs on the uncovered gold surface, and therefore short branches appear consequently. Then positively charged TBAB layers on the gold surfaces prevent the branches from aggregating with each other which stimulates the branch growth. The prepared branched gold nanoparticles show efficient surface-enhanced Raman scattering （SERS） properties. Low temperature （4 ℃） is unfavorable to the formation of multi-branched gold nanostructures, and only thin small irregular plate-like nanoparticles are produced. The addition of SDS in TBAB aqueous solution results in forming SDS micelles at much lower concentration of SDS （0.4 mmol/L） as compared to that in pure water, and short branched gold nanoparticles are obtained in the SDS-TBAB system.

Effects of the physicochemical properties of gold nanostructures on cellular internalization

Unique physicochemical properties of Au nanomaterials make them potential star materials in biomedicalapplications. However, we still know a little about the basic problem of what really mattersin fabrication of Au nanomaterials which can get into biological systems, especially cells, with highefficiency. An understanding of how the physicochemical properties of Au nanomaterials affecttheir cell internalization is of significant interest. Studies devoted to clarify the functions of variousproperties of Au nanostructures such as size, shape and kinds of surface characteristics in cell internalizationare under way. These fundamental investigations will give us a foundation for constructingAu nanomaterial-based biomedical devices in the future. In this review, we present the current advancesand rationales in study of the relationship between the physicochemical properties of Aunanomaterials and cell uptake. We also provide a perspective on the Au nanomaterial-cell interactionresearch.

Selective Gold Deposition on a Nanostructured Block Copolymer Film Crystallized by Epitaxy

An ordered nanostructure formed by epitaxial crystallization of a semicrystalline block copolymer on a substrate has been used as a patterned template for the selective deposition of thermally evaporated gold nanoparticles, resulting in the formation of structure-guiding host nanocomposites in which the ordered distribution of the guest particles is guided by the ordering of the host nanostructured block copolymer matrix. This opens new perspectives in the field of polymeric composites related to the maximum enhancement of effective physical properties and to the numerous possible applications that arise due to the presence of long-range order in the spatial distribution of functional nanoparticles.

Electrochemical construction of porous gold nanostructures on DVD substrate and its application as nonenzymatic hydrogen peroxide sensor

A simple acid-etching method was used to leach out silver from a bimetallic gold-silver based Digital Video Disc(DVD), which was further treated via a cyclic voltammetric scanning in 1 mmol/L HAu Cl4 solution to create a porous gold nanostructure. The as-fabricated electrode was characterized by field-emission scanning electron microscopy, energy-dispersed X-ray spectroscopy and X-ray diffraction. The high electro-catalytic activity of the resulting electrode toward the reduction of hydrogen peroxide(H2O2) presented excellent linear relationship in the range of 8.0×10?5 to 1.26×10?2 mol/L with the detection limit of 2.0×10-5 mol/L(S/N=3). The as-developed non-enzyme-sensor showed good reproducibility, stability, and selectivity.

Gold nanostructure based LSPR biosensors

The localized surface plasmon resonance (LSPR) of noble metal nanoparticles have been described in numerous articles. Changes in the peak intensity and wavelength of

Assemblies and composites of gold nanostructures for functional devices

Gold has been one of the most vastly used noble metals due to its unique properties.In modern manufacturing,gold is extensively used in electronics industry as electrical connectors due to the high conductivity and corrosion resistance.With advancements in gold chemistry and nanofabrication technologies,gold materials can be tailored down to the dimension of nanoscale,which enables various novel properties.However,it is still a huge challenge to realize practical functional devices by rational utilizing these gold nanostructures-based materials.Herein,the recent developments in the design and fabrication of various functional devices based on assemblies and composites of gold nanostructures are summarized.Starting from the plasmonic effect,optical colorimetric sensors,optoelectronics and surface-enhanced Raman spectroscopy sensors are introduced.Followed by conductive devices with novel properties,flexible transparent conductors,stretchable electronics,wearable and implantable devices are discussed.Both bottom-up and top-down approaches to prepare assemblies and composites are covered.In addition,the challenges and future developments in the field are also addressed.It is believed that further developments in gold nanostructures-based materials will greatly contribute to the nextgeneration biosensors,optoelectronics,wearable and implantable electronics.

金纳米结构光热转换材料的研究进展

金纳米结构材料具有重要的光热转换性质,在癌症治疗方面引起了全世界的高度关注。综述了金纳米结构光热转换材料包括纳米球、纳米棒、纳米壳、纳米笼以及纳米簇等的制备方法和进展,随后总结了其表面功能化的3种方法,即利用双功能的配体直接进行配体交换、二氧化硅包覆、聚合物包覆。最后介绍了其在激光诱导的药物释放、光热治疗、近红外热成像等生物医药方面的应用。

甲酸在纳米金承载铂(Pt^Au)电催化剂上的电化学氧化

采用循环伏安扫描测试对不同浓度的甲酸在纳米Au颗粒（（10.0±1.2）nm）承载Pt电催化剂（记为Ptm^Au,其中m为Pt/Au原子比）上的电化学氧化过程进行了研究.结果表明,Pt在纳米Au颗粒表面的形态对甲酸的电化学氧化行为影响显著.当Pt对Au颗粒形成壳层覆盖（m〉0.2）时,甲酸电氧化反应主要发生在高电势（相对SCE电极为0.6~1.0 V）范围,与常规Pt/C电催化剂上甲酸的电氧化行为类似;当Au表面Pt的形态由单原子壳层（m=0.2）递变为不大于1.0 nm的Pt原子簇或原子筏（m〈0.2）时,在低电势（-0.2~0.6 V）范围也能明显检测到甲酸的电氧化反应,而且随着m的减小,Pt的质量比活性显著提高.Pt呈现100%暴露（电化学活性面积EAS=236 m2/g-Pt）的Pt0.05^Au/C电催化剂在甲酸电氧化峰（0.38 V）处的质量比活性是通常Pt/C电催化剂（Pt分散度为30%或EAS为74 m2/g-Pt）的40倍,表明随着Au颗粒上Pt尺寸的减小或分散度的提高,Ptm^Au/C电催化剂对甲酸电氧化反应的催化活性也显著提高.在甲酸浓度由0.2 mol/L渐提高至3.2 mol/L时,Ptm^Au/C和Pt/C催化剂上甲酸电氧化反应的比电流均呈先增大后减小的火山形变化,表明适宜的甲酸工作浓度也是在Pt基催化剂上实现高功率直接甲酸燃料电池的关键因素之一.

Au-Ag三角纳米环单层膜的原位转化制备及SERS效应

利用模板牺牲氧化还原反应将自组装在基片上的三角板银纳米粒子(边长约为79.2nm)与氯金酸溶液作用进而原位转化形成三角纳米环.通过紫外-可见(UV-Vis)光谱实时监测基片上银三角板纳米粒子在反应不同阶段的消光特性;扫描电子显微镜(SEM)显示了银三角板纳米粒子转化过程的形貌变化;利用X射线光电子能谱(XPS)对其成分进行分析.表征结果表明,三角纳米环的成分为Au-Ag合金或复合物;随着基片与氯金酸溶液作用时间的增加,自组装膜的表面等离子体共振峰逐渐红移;Au-Ag三角环状纳米粒子的平均壁厚度从29.3nm缩小至16.2nm.以4-巯基苯胺(4-ATP)为探针分子研究了该Au-Ag三角环状纳米粒子单层膜的表面增强拉曼(SERS)活性.自组装单层膜基底的SERS信号随着Au-Ag三角纳米环平均壁厚度的增加逐渐增强.

帽状金纳米结构的制备、表征及表面增强拉曼散射活性

采用真空离子溅射法在自组装的单层阵列二氧化硅纳米粒子表面沉积金薄膜,制备了以S iO2为核的帽状金纳米结构.用透射电镜、扫描电镜、原子力显微镜、X射线衍射仪和紫外-可见-近红外分光光度计对样品的表面形貌、结构及光学性质进行了表征.以亚甲基蓝作为探针分子,对金纳米帽的表面增强拉曼散射活性进行了研究,结果显示,吸附在金纳米帽上的分子拉曼散射信号得到显著增强,增强因子达到107数量级.该基底在超灵敏生物和化学检测方面具有潜在的应用前景.

花瓣状铂-金-石墨烯纳米结构的制备及其在葡萄糖测定中的应用

利用氧化石墨烯（GO）、PtCl6^2-、AuCl^4-作为前驱体,在-0.4 V条件下,采用一步电化学还原法对GO和金属前驱体进行同时还原,成功制备了花瓣状的Pt-Au-GO纳米结构;同时利用伏安法研究了该催化剂对葡萄糖氧化的电催化性能,结果表明,此纳米结构对葡萄糖氧化反应表现出很好的电催化性能;据此构建了无酶葡萄糖传感器,该传感器在较低的电位下（-0.1 V）对葡萄糖的线性检测范围为1.0~25.0 mmol/L,响应灵敏度为26.3μA cm^-2（mmol/L）^-1,检出限为4.0μmol/L（S/N=3）,且传感器具有很好的重现性、稳定性和选择性,可用于实际样品的分析检测。

氯金酸的浓度对纳米金形态的影响

采用Zn置换HAuCl4溶液的方法制备了具有不同形貌的纳米金，并研究了HAuCl4溶液的浓度对纳米金形貌的影响。实验结果表明，纳米金的形貌主要取决于HAuCl4溶液的浓度。当HAuCl4溶液的浓度为0．01 mmol／L时，置换反应进行5min后的产物是金纳米颗粒，其粒径为10～50nm，24h后金颗粒的粒径超过100nm，金颗粒团聚成金花状。当HAuCl4溶液的浓度为1 mmol／L时，金颗粒的粒径为数百纳米，部分金颗粒团聚成金花状。当HAuCl4溶液的浓度为10 mmol／L时，在金颗粒中出现由纳米金片组成的多晶枝晶，多晶枝晶随后通过OA和OR机制转变成单晶枝晶。当HAuCl4溶液的浓度为30 mmol／L时，反应时直接生成金枝晶。因此，通过控制HAuCl4溶液的浓度，可制备具有不同形貌的纳米金。

基于毛丹状Au@Ag合金纳米结构的活性细菌表面增强拉曼散射传感

为实现活性细菌的快速和原位检测,使用无机碱性双氧水作为“清洁”还原剂,还原制备了一种毛丹状Au@Ag合金纳米颗粒,并将其作为表面增强拉曼散射(SERS)基底材料。研究发现:构建的毛丹状Au@Ag合金纳米颗粒具有较高的表面粗糙度和致密的表面纳米毛刺,该结构对细菌表面的吸附能力较强,且不影响细菌的生物活性;构建的毛丹状Au@Ag合金纳米颗粒在单颗粒表面具有大量的“纳米针尖”和“纳米间隙”,这种结构可产生较强的局部表面等离子体共振效应;将毛丹状Au@Ag合金纳米颗粒吸附于细菌表面,可以有效地增加细菌表面的SERS“热点”,且在实际检测中容易操作。利用以上特点,在633 nm的激发光激发下,可以有效获得活性细菌的SERS指纹谱信号,该方法的灵敏度和检测效率高,能广泛应用于微生物细胞的SERS传感分析。