贵金属纳米材料的液相合成及其表面等离子体共振性质应用

金属中的表面等离子体共振是描述其导带电子在电磁场作用下集体振荡的一个物理概念。金属纳米颗粒由于其表面等离子体共振性质表现出独特的光学应用。本文在相关研究的基础上,综述了具备表面等离子体共振性质的不同形貌及多种复合结构的贵金属纳米材料的制备和应用,并对其发展及应用前景进行了展望。     

贵金属纳米材料的液相合成及其表面等离子体共振性质应用

金属中的表面等离子体共振是描述其导带电子在电磁场作用下集体振荡的一个物理概念。金属纳米颗粒由于其表面等离子体共振性质表现出独特的光学应用。本文在相关研究的基础上,综述了具备表面等离子体共振性质的不同形貌及多种复合结构的贵金属纳米材料的制备和应用,并对其发展及应用前景进行了展望。     

基于局域表面等离子体共振效应的光学生物传感器*

贵金属纳米粒子表现出许多常规块体材料所不具备的优异性能,其中局域表面等离子体共振 (LSPR) 特性是研究热点之一。LSPR 的形状和位置与纳米粒子的组成、大小、形状、介电性质以及局域介质环境密切相关。基于这一特性,贵金属纳米粒子已广泛应用于光学生物传感器、光过滤器和表面增强光谱等领域。本文对各种结构的贵金属纳米粒子的制备方法及其在光学生物传感器中的应用进行了综述,并对 LSPR 纳米传感器的未来发展前景做了展望。     

Recent developments and applications of hybrid surface plasmon resonance interfaces in optical sensing

Nanostructured noble metals exhibit an intense optical near field due to surface plasmon resonance, therefore promising widespread applications and being of interest to a broad spectrum of scientists, ranging from physicists, chemists, and materials scientists to biologists. A wealth of research is available discussing the synthesis, characterization, and application of noble metal nanoparticles in optical sensing. However, with respect to the sensitivity of the frequency and width of these surface plasmon resonance modes to the particle’s shape, size, and environment, in nearly every case, success strongly depends on the availability of highly stable, adhesive, and sensitive nanoparticles. This undoubtedly presents a challenging task to nanofabrication. The past decade has witnessed fascinating advances in this field, in particular, the construction of oxide-based hybrid plasmonic interfaces to overcome the problem addressed above by (1) coating the metallic nanostructures with thin overlayers to form sandwiched structures or (2) embedding metallic nanostructures in a dielectric matrix to obtain metal/dielectric matrix nanocomposite films. In this critical review, we focus on recent work related to this field, beginning with a presentation of hybrid films with enhanced structural and optical stability, readily and selectively designed using chemical and physical techniques. We then illustrate their interesting optical properties and demonstrate exciting evidence for the postulated application in surface plasmon sensing fields. Finally, we survey the work remaining to be done for that potential to be realized.     

Recent advances in analytical and bioanalysis applications of noble metal nanorods

In the last decade the use of anisotropic nanoparticles in analytical and bioanalytical applications has increased substantially. In particular, noble metal nanorods have unique optical properties that have attracted the interest of many research groups. The localized surface plasmon resonance (LSPR) generated by interaction of light at a specific wavelength with noble metal nanoparticles was found to depend on particle size and shape and on the constituting material and the surrounding dielectric solution. Because of their anisotropic shape, nanorods are characterized by two LSPR peaks: the transverse, fixed at approximately 530 nm, and the longitudinal, which is in the visible–near infra-red region of the spectrum and varies with nanorod aspect ratio. The intense surface plasmon band enables nanorods to absorb and scatter light in the visible and near infra-red regions, and fluorescence and two-photon induced luminescence are also observed. These optical properties, with the reactivity towards binding events that induce changes in the refractive index of the surrounding solution, make nanorods a useful tool for tracking binding events in different applications, for example assembly, biosensing, in-vivo targeting and imaging, and single-molecule detection by surface-enhanced Raman spectroscopy. This review presents the promising strategies proposed for functionalizing gold nanorods and their successful use in a variety of analytical and biomedical applications.     

Plasmonic photocatalysts: harvesting visible light with noble metal nanoparticles

The efforts to produce photocatalysts operating efficiently under visible light have led to a number of plasmonic photocatalysts, in which noble metal nanoparticles are deposited on the surface of polar semiconductor or insulator particles. In the metal-semiconductor composite photocatalysts, the noble metal nanoparticles act as a major component for harvesting visible light due to their surface plasmon resonance while the metal-semiconductor interface efficiently separates the photogenerated electrons and holes. In this article, we survey various plasmonic photocatalysts that have been prepared and characterized in recent years.     

A unified view of propagating and localized surface plasmon resonance biosensors

The intense colors of noble metal nanoparticles have inspired artists and fascinated scientists for hundreds of years. In this review, we describe refractive index sensing platforms based on the tunability of the localized surface plasmon resonance (LSPR) of arrays of silver nanoparticles and of single nanoparticles. Specifically, the color associated with single nanoparticles and surface-confined nanoparticle arrays will be shown to be tunable and useful as platforms for chemical and biological sensing. Finally, the LSPR nanosensor will be compared to traditional, flat surface, propagating surface plasmon resonance sensors.     

Near-field optical imaging of enhanced electric fields and plasmon waves in metal nanostructures

In this article, studies on noble metal nanostructures using near-field optical microscopic imaging are reviewed. We show that near-field transmission imaging and near-field two-photon excitation imaging provide valuable methods for investigation of plasmon resonances in metal nanostructures. The eigenfunctions of plasmon modes in metal nanoparticles are directly visualized using these methods. For metal nanowire systems, wavevectors of the longitudinal plasmon modes can be estimated directly from the wave-function images, and the dispersion relations are plotted and analyzed. Using ultrafast transient near-field imaging, we show that the deformation of the plasmon wave function takes place after photoexcitation of a gold nanorod. Such methods of plasmon-wave imaging may provide a unique basic tool for designing plasmon-mode-based nano-optical devices. We also demonstrate that the near-field two-photon excitation probability images reflect localized electric-field enhancements in metal nanostructures. We apply this method to gold nanosphere assemblies and clearly visualize the local enhanced optical fields in the interstitial sites between particles (hot spots). We also show the contribution of hot spots to surface enhanced Raman scattering. The methodology described here may provide valuable basic information about the characteristic enhanced optical fields in metal nanostructures as well as on their applications to new innovative research areas beyond the conventional scope of materials.     

Preparation and Use of Chemically Modified Noble Metal Nanoparticles

Papers dealing with chemical modification of the surface of noble metal nanoparticles and their use in analytical and bioanalytical chemistry, pharmacology, etc., are analyzed. Grafting of a layer of preset chemical composition on the nanoparticle surface allows preparation of functional materials combining the properties of the metal core (surface plasmon resonance, enhancement of fluorescence and nonelastic scattering) and shell (selective interaction with components of the surrounding medium). Combination of these properties opens wide prospects for using the modified nanoparticles in various branches of science and engineering, primary in chemical and biochemical analysis, and also in pharmacology.     

Spatially controlled SERS patterning using photoinduced disassembly of gelated gold nanoparticle aggregates

Controlling the assembly of the nanoparticles is important because the optical properties of noble metal nanoparticles, such as the surface plasmon resonance (SPR) and surface-enhanced Raman scattering (SERS), are critically dependent on interparticle distances. Among many approaches available, light-induced disassembly is particularly attractive because it enables spatial modification of the optical properties of nanoparticle assemblies. In this study, we prepare gold nanoparticle (AuNP) aggregates in a gel matrix. Irradiation of the gelated AuNP aggregates at 532 nm leads to the disassembly of the aggregates, changing the color (SPR) from dark blue to red and extinguishing the SERS signal along the irradiated pattern, which opens the possibility of facile fabrication of spatially controlled SERS-generating microstructures. The photoinduced disassembly of the AuNP aggregates in solution is also investigated using UV-vis spectroscopy and transmission electron microscopy.     

功能化金纳米材料在肿瘤诊疗中的研究与应用

作为一种重要的贵金属, 金具有表面等离子共振的光学特性, 在材料、 催化和医学诊疗等领域有着广泛且重要的应用. 本文综合评述了表面功能化的金纳米材料在肿瘤诊断及治疗领域的相关研究, 并对金纳米材料在肿瘤诊疗领域的未来发展进行了展望.     

基于贵金属纳米颗粒生长的比色传感研究进展

近年来,作为颜色标记和信号发生器的贵金属纳米粒子由于其简单性和实用性而被广泛用于比色测定和传感的研究当中。本文综述了近十年基于贵金属纳米粒子生长的比色传感器策略和应用的最新进展,总结了基于贵金属纳米颗粒生长的单色及多色传感器的传感原理、分类及前沿应用,探索了其比色传感的信号产生、分类和放大机制。由于贵金属纳米粒子在不同尺寸、距离、形状、成分等基底上的生长会产生不同的LSPR共振峰以及显著的传感信号变化,我们详细讨论了贵金属纳米粒子在金纳米棒等晶种基底上生长的比色传感。最后,我们对目前该比色传感面临的挑战和未来前景进行了展望。     

Surface plasmon resonance-mediated colloid gold monolayer junctions

Because of the localized field amplification that occurs, excitation of surface plasmons (SPs) in metal nanoparticle-based current-carrying nanoelectronic devices is expected to lead to new and interesting applications. We report a simple way to prepare surface plasmon resonance (SPR)-mediated colloid Au monolayer junctions by a wet chemistry and soft top electrode deposition. The SPR-enhanced junction current is observed upon illumination with light of energies close to the nanoparticle plasmon resonance wavelengths. This current is superimposed on tunneling current observed in the absence of surface plasmons.     

Plasmon‐Mediated Syntheses of Metallic Nanostructures

The ability to prepare noble metal nanostructures of a desired composition, size, and shape enables their resulting properties to be exquisitely tailored, which has led to the use of these structures in numerous applications, ranging from medicine to electronics. The prospect of using light to guide nanoparticle reactions is extremely attractive since one can, in principle, regulate particle growth based on the ability of the nanostructures to absorb a specific excitation wavelength. Therefore, using the nature of light, one can generate a homogenous population of product nanoparticles from a heterogeneous starting population. The best example of this is afforded by plasmon‐mediated syntheses of metal nanoparticles, which use visible light irradiation and plasmon excitation to drive the chemical reduction of Ag⁺ by citrate. Since the initial discovery that Ag triangular prisms could be prepared by the photo‐induced conversion of Ag spherical nanoparticles, plasmon‐mediated synthesis has become a highly controllable technique for preparing a number of different Ag particles with tight control over shape, as well as a wide variety of Au‐Ag bimetallic nanostructures. We discuss the underlying physical and chemical factors that drive structural selection and conclude by outlining some of the important design considerations for controlling particle shape as learned through studies of plasmon‐mediated reactions, but applicable to all methods of noble metal nanocrystal synthesis.     

Synthesis of ultra-small platinum,palladium and gold nanoparticles by Shewanella loihica PV-4 electrochemically active biofilms and their enhanced catalytic activities

Ultra-small nanoparticles (USNPs) of noble metals have a great potential in a variety of applications due to their high surface areas and high reactivity. This work employed electrochemically active biofilms (EABs) composed of a single bacterium strain of Shewanella loihica PV-4 and successfully synthesized USNPs of noble metal Au, Pd, and Pt. The synthesized USNPs had a size range between 2 and 7?nm and exhibited excellent catalytic performance in dye decomposition. The results of this work shine light on the use of EABs in nanoparticle synthesis.     

Plasmonic properties of single multispiked gold nanostars: correlating modeling with experiments

Gold nanostars, possessing multiple sharp spikes, have emerged as promising plasmonic particles in the field of ultrasensitive sensing. We have developed a water-based method for high-yield synthesis of size-tunable anisotropic gold nanoparticles with a varying number of spiky surface protrusions, and performed systematic experimental and theoretical analyses of the optical properties of the single gold nanostars by characterizing them simultaneously with scanning electron microscopy and dark-field scattering spectroscopy. The morphologies and corresponding scattering spectra of the individual gold nanostars have been compared with electromagnetic simulations of the plasmonic resonances utilizing the finite-difference time-domain (FDTD) method. The study provides a correlation between the experimental and calculated scattering spectra and charge distributions of the different plasmon modes in the individual gold nanostars with varying numbers and relative orientations of surface protrusions. Our results provide guidelines for choosing gold nanostars with a proper number of spikes and appropriate dimensions of the core and arms for particular plasmonic applications as well as for further developing preparation methods of multispiked metal nanoparticles.     

具特定晶面且大比表面积贵金属纳米晶催化基元的构筑

贵金属纳米晶在电催化等领域具有广泛应用. 其催化活性往往与纳米晶体的表面结构直接相关,而催化剂的贵金属原子利用率与比表面积密切相关. 因小尺寸纳米晶难以保留特定的晶面,而具有特定表面的纳米晶通常结晶成尺寸较大、比表面积比较小的晶体,调控纳米晶的尺寸和表面结构两种策略似乎相互矛盾. 如何可控合成同时具有特定表面结构和大比表面积的贵金属纳米晶具有重要的意义. 本综述从形貌调控角度详细介绍提高贵金属纳米晶原子利用率的方法策略;总结调控单贵金属及其合金同时具有特定晶面和大比表面积的研究现状;最后,对纳米晶的形貌调控领域未来的发展趋势提出展望.     

New insight into daylight photocatalysis of AgBr@Ag: synergistic effect between semiconductor photocatalysis and plasmonic photocatalysis

Noble metal nanoparticles (NPs) are often used as electron scavengers in conventional semiconductor photocatalysis to suppress electron-hole (e(-)-h(+) ) recombination and promote interfacial charge transfer, and thus enhance photocatalytic activity of semiconductors. In this contribution, it is demonstrated that noble metal NPs such as Ag NPs function as visible-light harvesting and electron-generating centers during the daylight photocatalysis of AgBr@Ag. Novel Ag plasmonic photocatalysis could cooperate with the conventional AgBr semiconductor photocatalysis to enhance the overall daylight activity of AgBr@Ag greatly because of an interesting synergistic effect. After a systematic investigation of the daylight photocatalysis mechanism of AgBr@Ag, the synergistic effect was attributed to surface plasmon resonance induced local electric field enhancement on Ag, which can accelerate the generation of e(-)-h(+) pairs in AgBr, so that more electrons are produced in the conduction band of AgBr under daylight irradiation. This study provides new insight into the photocatalytic mechanism of noble metal/semiconductor systems as well as the design and fabrication of novel plasmonic photocatalysts.     

Intrinsic therapeutic applications of noble metal nanoparticles: past, present and future

Biomedical nanotechnology is an evolving field having enormous potential to positively impact the health care system. Important biomedical applications of nanotechnology that may have potential clinical applications include targeted drug delivery, detection/diagnosis and imaging. Basic understanding of how nanomaterials, the building blocks of nanotechnology, interact with the cells and their biological consequences are beginning to evolve. Noble metal nanoparticles such as gold, silver and platinum are particularly interesting due to their size and shape dependent unique optoelectronic properties. These noble metal nanoparticles, particularly of gold, have elicited a lot of interest for important biomedical applications because of their ease of synthesis, characterization and surface functionalization. Furthermore, recent investigations are demonstrating another promising application of these nanomaterials as self-therapeutics. To realize the potential promise of these unique inorganic nanomaterials for future clinical translation, it is of utmost importance to understand a few critical parameters; (i) how these nanomaterials interact with the cells at the molecular level; (ii) how their biodistribution and pharmacokinetics influenced by their surface and routes of administration; (iii) mechanism of their detoxification and clearance and (iv) their therapeutic efficacy in appropriate disease model. Thus in this critical review, we will discuss the various clinical applications of gold, silver and platinum nanoparticles with relevance to above parameters. We will also mention various routes of synthesis of these noble metal nanoparticles. However, before we discuss present research, we will also look into the past. We need to understand the discoveries made before us in order to further our knowledge and technological development (318 references).     

Flash light synthesis of noble metal nanoparticles for electrochemical applications: silver,gold, and their alloys

Journal of Solid State Electrochemistry - The synthesis of noble metal nanoparticles (i.e., silver and gold) for electrochemical applications has been widely studied using mainly wet synthesis...