Designer Gold-Framed Palladium Nanocubes for Plasmon-Enhanced Electrocatalytic Oxidation of Ethanol

Surface plasmon of coinage metal nanostructures has been employed as a powerful route in boosting the performances in heterogenous catalysis. Development of efficient plasmonic nanocatalysts with high catalytic performance and efficient light harvesting properties is of vital importance. Herein, we rationally designed and synthesized a plasmonic nanocatalyst composed of Au-framed Pd nanocubes by an Ag(I)-assisted seed-mediated growth method. In the synthesis, the incorporation of Ag(I) suppresses the reduction of Au on the {100} surface of cubic Pd seeds and leads to the formation of Au nanoframes on the Pd nanocubes. The unique Au-framed Pd nanocubes can integrate the superior electrocatalytic of Pd and the outstanding plasmonic properties of Au. Thus, these nanostructures were employed as plasmonic nanocatalysts for plasmon-enhanced electrocatalytic oxidation of ethanol with improved stability.     

Towards Electrochemiluminescence Microscopy Exploration of Plasmonic-Mediated Phenomena at the Single-Nanoparticle Level

The rational design of functional plasmonic metasurfaces and metamaterials requires the development of high-throughput characterization techniques compatible with operando conditions and capable of addressing single-nanostructures. In their work, Wei et al. demonstrate the use of electrochemiluminescence microscopy to investigate the mechanism behind plasmon-enhanced luminescence induced by gold nanostructures. The use of gold plasmonic arrays was exploited to achieve the rapid spectroscopic evaluation of all the individual nanostructures, and the correlation of the results with high- resolution electron microscopy analysis, guaranteeing a strict one-to-one correspondence. The authors were able to identify two different mechanisms for the enhancement of [Ru(bpy)₃]²⁺-tri-n-propylamine electrochemiluminescence mediated by single gold nanoparticles and by small plasmonic clusters. In the future, the proposed characterization could be used for the rapid and in situ spectroscopic analysis of more complex plasmonic nanostructures and metasurfaces.     

Plasmonic films based on colloidal lithography

This paper reviews recent advances in the field of plasmonic films fabricated by colloidal lithography. Compared with conventional lithography techniques such as electron beam lithography and focused ion beam lithography, the unconventional colloidal lithography technique with advantages of low-cost and high-throughput has made the fabrication process more efficient, and moreover brought out novel films that show remarkable surface plasmon features. These plasmonic films include those with nanohole arrays, nanovoid arrays and nanoshell arrays with precisely controlled shapes, sizes, and spacing. Based on these novel nanostructures, optical and sensing performances can be greatly enhanced. The introduction of colloidal lithography provides not only efficient fabrication processes but also plasmonic films with unique nanostructures, which are difficult to be fabricated by conventional lithography techniques.     

Dodecahedral Au/Pt Nanobowls as Robust Plasmonic Electrocatalysts for Methanol Oxidation under Visible-Light Illumination

Plasmonic nanostructures with large absorption areas under resonant excitation have been utilized extensively in photon-assisted applications. In this work, dodecahedral Au nanobowls were first prepared by an easy and template-free method only through the introduction of H₂PtCl₆ and I⁻ during the growth procedure. The Au nanobowls show electron-field enhancement due to the high curvature of the bowl edge, the open region, and dodecahedral morphology. Au/Pt nanobowls, which couple plasmonic Au and catalytic Pt, were then constructed as plasmonic electrocatalysts for methanol oxidation. The mass activity reached 497.6 mA mg⁻¹ under visible-light illumination, which is 1.9 times that measured in the dark. Simultaneously, the electrocatalytic stability is also greatly improved under light excitation. The enhanced properties of the plasmonic Au/Pt electrocatalysts are ascribed to the synergistic effect of the plasmon-enhanced photothermal and hot-carrier effects on the basis of experimental investigations. This work thus offers an effective methodology to construct efficient plasmonic electrocatalysts for fuel cells.     

Plasmonics for pulsed-laser cell nanosurgery: Fundamentals and applications

This review describes the fundamental aspects of pulsed laser interaction with plasmonic nanostructures, and its applications to cell nanosurgery, including the destruction, modification or manipulation of molecular, sub-cellular and cellular structures. The review assumes no prior knowledge of the field of plasmonics and begins with a short review of the basic theory of plasmon excitation and optical properties of nanoscale metallic structures. Fundamentals of short and ultrashort laser pulse interaction with plasmonic nanostructures in a water environment are then discussed. Special emphasis is put on the consequences of the irradiation on the surrounding environment of the nanostructure, including heating, low-density plasma generation, pressure wave release and formation of vapor bubbles. The paper is concluded with a review of different applications of pulsed-laser interaction with plasmonic nanostructures for cell nanosurgery, including photothermal therapy, plasmonic enhanced cell transfection, molecular surgery and drug delivery.     

Understanding plasmonic catalysis with controlled nanomaterials based on catalytic and plasmonic metals

Recently, it has been established that the localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles can be put toward the acceleration and control of molecular transformations. This field, named plasmonic catalysis, has emerged as a new frontier in nanocatalysis. For metals such as silver (Ag), gold (Au), and copper (Cu), the LSPR excitation can take place in the visible and near-infrared ranges, opening possibilities for the conversion of solar to chemical energy and new/alternative reaction pathways not accessible via conventional, thermally activated catalytic processes. As both catalytic and optical properties can be tuned by controlling several physical and chemical parameters at the nanoscale, design-controlled nanomaterials open the door to unlock the potential of plasmonic catalysis both in terms of fundamental understanding and optimization of performances. In this context, after introducing the fundamentals of plasmonic catalysis, we provide an overview on the current understanding of this field enabled by the utilization of designed-controlled nanostructures based on plasmonic and catalytic metals as model systems. We start by discussing trends in plasmonic catalytic performances and their correlation with nanoparticle size, shape, composition, and structure. Then, we highlight how multimetallic compositions and morphologies containing both catalytic and plasmonic components enables one to extend the use of plasmonic catalysis to metals that are important in catalysis but do not support LSPR excitation in the visible range. Finally, we focus on key challenges and perspectives that are critically important to assist us in designing future energy-efficient plasmonic-catalytic materials.     

SPR银金电极上光电化学反应和EC-SERS理论研究

随着纳米科学的发展,人们再次关注到金属电极上的光电化学研究. 这主要得益于币族金属纳米结构具有强的表面等离激元共振（SPR）效应,它能有效地将光从远场光转化为近场光,汇聚光能到金属表面区域,可以在表面产生强的光电场效应,或产生较长寿命的热电子-空穴载流子效应,或是更长时间尺度的热效应. 因此,SPR效应不仅产生了表面增强拉曼散射(SERS)效应,用于表征吸附分子,而且可能诱发表面化学反应,为在电化学界面实现光与电协同调控化学反应提供新思路. 本文首先回顾了金属电极上光电流理论的发展,然后总结了本研究组近年来将量子化学计算用于光电化学反应和SERS光谱研究的工作,并以在银金纳米结构电极上水合质子还原和芳香胺氧化为例,比较了热电子和热空穴参与光电化学反应的特点,揭示了SPR参与光电化学反应的本质.     

Imaging nanostructures with scanning photoionization microscopy

We report detailed studies of local electronic properties in nanostructured thin metallic films using scanning photoionization microscopy. This novel form of microscopy combines the advantages of diffraction-limited optical excitation with the ability to detect both photons and low kinetic energy photoelectrons, permitting sensitive characterization of heterogeneous surfaces under vacuum conditions. Using this technique, correlated measurements of multiphoton photoemission cross section and optical penetration depth are reported for Au films supported on Pt. These results present a first step toward combining confocal fluorescence or Raman microscopy with time-resolved photoelectron imaging spectroscopy in complex metal film environments, which should be ideally suited to investigating local plasmonic effects in nanostructures.     

Surface Activation of Pt Nanoparticles Synthesised by “Hot Injection” in the Presence of Oleylamine

Oleylamine (OA) based “hot injection” colloidal synthesis offers a versatile approach to the synthesis of highly monodisperse metallic and multi‐metallic alloyed nanostructures in the absence of potentially toxic and unstable phosphine compounds. For application in heterogeneous catalysis and electrocatalysis, the adsorbed OA species at the metal surfaces should be effectively removed without compromising the structure and composition of the nanostructures. Herein, we investigate the removal of OA from colloidal Pt nanoparticles through 1) “chemical methods” such as washing in acetic acid or ethanol, and ligand exchange with pyridine; and 2) thermal pre‐treatment between 185 and 400 °C in air, H₂ or Ar atmospheres. The electrochemical reactivity of Pt nanoparticles is acutely affected by the presence of surface organic impurities, making this material ideal for monitoring the effectiveness of OA removal. The results showed that thermal treatment in Ar at temperatures above 400 °C provides highly active particles, with reactivity comparable to the benchmark commercial catalyst, Pt/ETEK. The mechanism involved in thermal desorption of OA was also investigated by thermogravimetric analysis coupled to mass spectrometry (TGA‐MS). Oxidation of HCOOH and adsorbed CO in acidic solution were used as test reactions to assess the Pt electrocatalytic activity.     

Electrochemical plasmonic sensors

The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.     

Optical enhancement effects of plasmonic nanostructures on organic photovoltaic cells

In this article, the optical enhancement effects of plasmonic nanostructures on OPV cells were reviewed as an effective way to resolve the mismatch problems between the short exciton diffusion length in organic semiconductors (around 10 nm) and the large thickness required to fully absorb sunlight (e.g. hundreds of nanometers). Especially, the performances of OPVs with plasmonic nanoparticles in photoactive and buffer layers and with periodic nanostructures were investigated. Furthermore, nanoimprint lithography-based nanofabrication processes that can easily control the dimension and uniformity of structures for large-area and uniform plasmonic nanostructures were demonstrated.     

Plasmonic approach to enhanced fluorescence for applications in biotechnology and the life sciences

One of the most rapidly growing areas of physics and nanotechnology is concerned with plasmonic effects on the nanometer scale; these have applications in sensing and imaging technologies. Nanoplasmonic colloids such as Ag and Au have been attracting active interest, and there has been a recent explosion in the use of these metallic nanostructures to modify the spectral properties of fluorophores favorably and to enhance the fluorescence emission intensity. In this feature article, we summarize our work over a range of nanoplasmonics-assisted biological applications such as flow cytometry, immunoassays, cell imaging and bioassays where we use custom-designed plasmonic nanostructures (Ag and Au) to enhance fluorescence signatures. This fluorophore-metal effect offers unique advantages in providing improved photostability and enhanced fluorescence signals. We discuss the plasmonic enhancement of lanthanide fluorophores whose long and microsecond lifetimes offer the advantage of background-free fluorescence detection, but low photon cycling rates lead to poor brightness. We also show that plasmonic colloids are capable of enhancing the emission of fluorescent nanoparticles, including upconverting nanocrystals and lanthanide nanocomposites.     

Recent advances in plasmonic organic photovoltaics

Light trapping based on the localized surface-plasmon resonance(LSPR)effect of metallic nanostructures is a promising strategy to improve the device performance of organic solar cells(OSCs).We review recent advances in plasmonic-enhanced OPVs with solution-processed metallic nanoparticles(NPs).The different types of metallic NPs(sizes,shapes,and hybrids),incorporation positions,and NPs with tunable resonance wavelengths toward broadband enhancement are systematically summarized to give a guideline for the realization of highly efficient plasmonic photovoltaics.     

Use of thin sectioning (nanoskiving) to fabricate nanostructures for electronic and optical applications

This Review discusses nanoskiving--a simple and inexpensive method of nanofabrication, which minimizes requirements for access to cleanrooms and associated facilities, and which makes it possible to fabricate nanostructures from materials, and of geometries, to which more familiar methods of nanofabrication are not applicable. Nanoskiving requires three steps: 1) deposition of a metallic, semiconducting, ceramic, or polymeric thin film onto an epoxy substrate; 2) embedding this film in epoxy, to form an epoxy block, with the film as an inclusion; and 3) sectioning the epoxy block into slabs with an ultramicrotome. These slabs, which can be 30 nm-10 μm thick, contain nanostructures whose lateral dimensions are equal to the thicknesses of the embedded thin films. Electronic applications of structures produced by this method include nanoelectrodes for electrochemistry, chemoresistive nanowires, and heterostructures of organic semiconductors. Optical applications include surface plasmon resonators, plasmonic waveguides, and frequency-selective surfaces.     

Nanostructured materials with localized surface plasmon resonance for photocatalysis

Localized surface plasmon resonance（LSPR） enhanced photocatalysis has fascinated much interest and considerable efforts have been devoted toward the development of plasmonic photocatalysts.In the past decades,noble metal nanoparticles（Au and Ag） with LSPR feature have found wide applications in solar energy conversion.Numerous metal-based photocatalysts have been proposed including metal/semiconductor heterostructures and plasmonic bimetallic or multimetallic nanostructures.However,high cost and...     

Sensing using localised surface plasmon resonance sensors

The bright colours of noble metal particles have attracted considerable interest since historical times, where they were used as decorative pigments in stained glass windows. More recently, the tuneable optical properties of metal nanoparticles and their addressability via spectroscopic techniques have brought them back into the forefront of fundamental and applied research fields. Much of the recent attention concerning metal nanoparticles such as gold and silver has been their use as small-volume, ultra-sensitive label-free optical sensors. Plasmonic nanoparticles act in this case as transducers that convert changes in the local refractive index into spectral shifts of the localized surface plasmon resonance (LSPR) band. This LSPR-shift assay is a general technique for measuring binding affinities and rates from any molecule that induces a change in the local refractive index around the metallic nanostructures. By attaching molecular recognition elements (chemical or biological ligands) on the nanostructures, specificity and selectivity to the analyte of interest are introduced into the nanosensor. In this review, we will discuss the different methods used to fabricate plasmonic nanosensors. A special emphasis will be given to techniques used to link plasmonic nanostructures to surfaces. While the difference between colorimetric and refractive index sensing approaches will be briefly described, the importance to distinguish between bulk refractive index (RI) sensing and molecular near-field refractive index sensing will be discussed. The recent progress made in the development of novel surface functionalization strategies together with the formation of optically and mechanically stable LSPR sensors will be highlighted.     

Recent Advances in Plasmonic Nanostructures Applied for Label-free Single-cell Analysis

Cellular heterogeneity presents a major challenge in understanding the relationship between cells of particular genotype and response in disease. In order to characterize the cell-to-cell differences during the biochemical processes, single-cell analysis is necessary. Profiting from the unique localized surface plasmon resonance (LSPR) and Mie scattering, plasmonic nanostructures have revealed stable and adjustable scattering signals, avoiding photobleaching, blinking and autofluorescence phenomenon. These characterizations are propitious to the dynamic trace and biological image of single living cells. In this review, we discuss the recent advances in plasmonic nanostructures applied for label-free detection and monitoring of target cells at single-cell level by using three different techniques, surface-enhanced Raman scattering (SERS), surface-enhanced Infrared absorption spectroscopy (SEIRAS), and dark-field microscopy. Various avenues to design plasmonic probes combining spectra and imaging for single-cell analysis are demonstrated as well. We hope this review can highlight the superiority of plasmonic nanostructures in single cellular analysis, and further motivate the development of label-free cell analysis technique to elucidate cellular diversity and heterogeneity.     

Plasmonic biosensing based on non-noble-metal materials

This review focuses on the research progress of non-noble-metal materials with nanostructures for plasmonic biosensing. Firstly, the physical and sensing principles of localized surface plasmon resonance (LSPR) sensors are briefly introduced; then non-noble-metal materials, such as copper, aluminum, semiconductor, graphene and other materials, for plasmonic sensing are categorized and presented. Finally, a rational discussion about the future prospective of novel materials for plasmonic sensing is given.     

Hot‐Electron‐Transfer Enhancement for the Efficient Energy Conversion of Visible Light

Great strides have been made in enhancing solar energy conversion by utilizing plasmonic nanostructures in semiconductors. However, current generation with plasmonic nanostructures is still somewhat inefficient owing to the ultrafast decay of plasmon‐induced hot electrons. It is now shown that the ultrafast decay of hot electrons across Au nanoparticles can be significantly reduced by strong coupling with CdS quantum dots and by a Schottky junction with perovskite SrTiO₃ nanoparticles. The designed plasmonic nanostructure with three distinct components enables a hot‐electron‐assisted energy cascade for electron transfer, CdS→Au→SrTiO₃, as demonstrated by steady‐state and time‐resolved photoluminescence spectroscopy. Consequently, hot‐electron transfer enabled the efficient production of H₂ from water as well as significant electron harvesting under irradiation with visible light of various wavelengths. These findings provide a new approach for overcoming the low efficiency that is typically associated with plasmonic nanostructures.     

Nano-Impact Single-Entity Electrochemistry Enables Plasmon-Enhanced Electrocatalysis**

Plasmon-enhanced electrocatalysis (PEEC), based on a combination of localized surface plasmon resonance excitation and an electrochemical bias applied to a plasmonic material, can result in improved electrical-to-chemical energy conversion compared to conventional electrocatalysis. Here, we demonstrate the advantages of nano-impact single-entity electrochemistry (SEE) for investigating the intrinsic activity of plasmonic catalysts at the single-particle level using glucose electrooxidation and oxygen reduction on gold nanoparticles as model reactions. We show that in conventional ensemble measurements, plasmonic effects have minimal impact on photocurrents. We suggest that this is due to the continuous equilibration of the Fermi level (E_F) of the deposited gold nanoparticles with the E_F of the working electrode, leading to fast neutralization of hot carriers by the measuring circuit. The photocurrents detected in the ensemble measurements are primarily caused by photo-induced heating of the supporting electrode material. In SEE, the E_F of suspended gold nanoparticles is unaffected by the working electrode potential. As a result, plasmonic effects are the dominant source of photocurrents under SEE experimental conditions.