Photothermal properties of Cu@polycarbonate composites with strong localized surface plasmon resonances

Copper is relatively low cost and highly abundant compared with the well-studied noble metals such as gold and silver.However,the poor plasmonic and high susceptibility towards oxidation limit the study of its optical properties and applications as well.Herein,copper nanoparticles@polycarbonate(Cu@PC)composites were prepared by using a facile one-step solvothermal method.The Cu@PC composites have strong localized surface plasmon resonances(LSPR)due to that the PC shell can induce the particles to form many-particles system with different particle numbers,which not only lead to overlap and hybridize of the LSPR modes,but also shift the LSPR away from the interband transitions,and the PC layer also prevents the oxidation of Cu nanoparticles.The photothermal conversion efficiency of Cu@PC composites reaches 41.1%under 808 nm continuous wave(CW)laser irradiation which is higher than previously reported Cu nanomaterials that have been reported.Meanwhile,the composites also have high photothermal stability.Moreover,interfacial evaporator is prepared by assembling the Cu@PC composites on scouring sponge as light absorption layer which has>92.8%absorption in entire solar spectrum range.Its seawater evaporation rate is 3.177 kg·m^(-2)·h^(-1)with a E_(evaporator)/E_(water)of 5.2.The high evaporation rate interfacial evaporator with low cost,simple,and scalable approach shows great application value in the field of photothermal evaporation.

A review on plasmonic enhancement of activity and selectivity in electrocatalytic CO_(2)reduction

Utilizing plasmonic effects to assist electrochemical reactions exhibits a huge potential in tuning the reaction activities and product selectivity,which is most appealing especially in chemical reactions with multiple products,such as CO_(2)reduction reaction(CO_(2)RR).However,a comprehensive review of the development and the underlying mechanisms in plasmon-assisted electrocatalytic CO_(2)RR remains few and far between.Herein,the fundamentals of localized surface plasmonic resonance(LSPR)excitation and the properties of typical plasmonic metals(including Au,Ag,and Cu)are retrospected.Subsequently,the potential mechanisms of plasmonic effects(such as hot carrier effects and photothermal effects)on the reaction performance in the field of plasmon-assisted electrocatalytic CO_(2)RR are summarized,which provides directions for the future development of this field.It is concluded that plasmonic catalysts exhibit potential capabilities in enhancing CO_(2)RR while more in situ techniques are essential to further clarify the inner mechanisms.

Fano resonances in complex plasmonic super-nanoclusters： The effect of environmental modifications on the LSPR sensitivity

In this study, gold nanodisk clusters in heptamer orientations as clusters were used to design a super-heptamer consisting of one central and six peripheral heptamers. We examined the position and movement of the plasmon and Fano resonances by sketching the spectral response of the superstructure for various nanodisk dimensions. The quality of the interference between the superradiant and subradiant plasmon resonance modes of the nanodisk clusters was found to depend strongly on the structural configuration and the refractive index of the environmental medium. We replaced the central heptamer with a nanodisk and probed the position of the Fano resonance by geometrically altering the nanodisk structure. Finally, the effect of the dielectric environment on the plasruon re- sponse of both of the studied structures was examined numerically and theoretically. The localized surface plasmon resonance sensitivity of the finite plasmonic structures to the presence of liquid substances was investigated and shown by plotting the linear figure of merit. The finite-difference time-domain method was used as a numerical tool to investigate the plasmon response of the structure.

Large-scale controllable fabrication of aluminum nanobowls for surface plasmon-enhanced fluorescence

Al nanoparticles(NPs)exhibit excellent localized surface plasmon resonance(LSPR)properties and have been considered a promising alternative to plasmonic Au or Ag NPs.However,it remains difficult to fabricate Al NPs with uniform size and controllable morphology over a large area on substrates,which seriously hinders the in-depth exploration of their properties and applications.Herein,we have developed a self-assembly nanoparticle template method to realize the controllable preparation of bowl-shaped Al NPs(Al nanobowls(Al NBs))with tunable sizes from 36 to 131 nm on the substrate surface,accompanied by tunable LSPR spectral responses from 272 to 480 nm.Among them,131 nm Al NBs exhibit superior fluorescence enhancement ability(1932.2-fold)and a low detection limit(78.6 pM)towards 5-carboxyfluorescein,exceeding comparable Ag NBs and Au nanospheres(NSs).This can be attributed to the strong electromagnetic enhancement induced by the LSPR effect and the effective inhibition of fluorescence quenching caused by the self-passivated oxide layer.Therefore,the successful fabrication of Al NBs on substrates is of vital significance for their promising applications,including surface-enhanced spectroscopy,sensitive fluorescence detection,light-harvesting devices,biosensing,and ultraviolet(UV)plasmonics.

Engineering the inter-island plasmonic coupling in homometallic Au-Au_(n)core-satellite structures

We show that through strong ligand mediated interfacial energy control between Au seeds and the deposited Au,the non-wetting growth of Au on Au seeds led to the formation homometallic core-satellite nanostructures.To modulate the intraparticle plasmonic coupling between the core and the satellites,the number and size of the Au satellites,and their inter-island distances were continuously tuned by varying the growth kinetics.As a result of the precise structural control,the plasmonic absorptions of the core-satellite nanostructures were tuned from visible to near-infrared(NIR)spectral range,and the extent of spectral modulation(500-1300 nm)is among the best of the literature methods.This synthetic advance enriches the toolbox for nanosynthesis and points to a new direction in the exploration of sophisticated functional designs.

Noble-metal free plasmonic nanomaterials for enhanced photocatalytic applications—A review

Plasmonic nanomaterial catalysis is currently at the frontier of photocatalysis,overcoming the limitations of wide bandgap semiconductors for light absorption.Its localized surface plasmon resonance(LSPR)properties allow broad ultraviolet-visible-near infrared ray(UV-vis-NIR)absorption,making it an ideal material for solar energy conversion.Most plasmonic nanostructures rely on precious metals.Although noble metal plasmonic nanomaterials have proven to be one of the strategies for enhancing photocatalytic activity,their expensive cost and limitations in light absorption range have hindered their practical application.As a result,noble-metal free plasmonic nanomaterials have risen to the top of the research priority list.Therefore,this paper reviews the fundamental principles and classification of the LSPR effect of noble-metal free plasmonic nanomaterials in photocatalytic and their recent applications in hydrogen generation,carbon dioxide reduction,and pollutant degradation.Specific cases elucidate the possible working mechanism of enhanced photocatalysis by noble-metal free plasmonic nanomaterials.Finally,the challenges and future opportunities for noble-metal free plasmonic nanomaterials in energy conversion and storage are discussed and envisioned.

Deviating from the nanorod shape： Shape-dependent plasmonic properties of silver nanorice and nanocarrot structures

Noble metallic nanostructures exhibit special optical properties resulting from excitation of surface plasmons. Among the various metallic nanostructures, nanorods have attracted particular attention because of their unique and intriguing shape-dependent plasmonic properties. Nanorods can sup- port transverse and longitudinal plasmon modes, the latter ones depending strongly on the aspect ratio of the nanorod. These modes can be routinely tuned from the visible to the near-infrared spectral regions. Although nanorods have been investigated extensively, there are few studies de- voted to nanostructures deviating from the nanorod shape. This review provides an overview of recent progress in the development of two kinds of novel quasi-one-dimensional silver nanostruc- tures, nanorice and nanocarrot, including their syntheses, crystalline characterizations, plasmonic property analyses, and performance in plasmonic sensing applications.

The beginnings of plasmomechanics： towards plasmonic strain sensors

This article exposes the beginnings of a new field which could be named as ＂plasmomechanics＂. Plasmomechanics comes from the convergence between mechanics and plasmonics. Here we discuss a relatively recent topic whose technolo- gical aim is the development of plasmonic strain sensors, The idea is based on the ability to deduce Au nanoparticles （NPs） distance distributions from polarized optical extinction spectroscopy which could thus give access to material strains. Variations of interparticle distances distributions can indeed lead to variations of plasmonic coupling and thus to material color change as shown here experimentally and numerically for random Au NP assemblies deposited onto elastomer films,

Background-free three-dimensional selective imaging of anisotropic plasmonic nanoparticles

There is an increasing demand for advanced optical imaging techniques that can detect and resolve nanosize objects at a spatial resolution below the optical diffraction limit, especially in three-dimensional （3D） cellular environments. In this study, using a polarization-activated localization scheme based on the orientation-dependent properties of anisotropic plasmonic metal nanoparticles （MNPs）, ＂photoswitchable＂ imaging of single gold nanorods （AuNRs） was accomplished not only in two dimensions but also in three dimensions. Moreover, the Rayleigh scattering background arising from the congested subcellular structures was efficiently suppressed. Thus, we obtained the 3D distributions of both the position and the orientation of the AuNRs inside the cells and investigated their intemalization kinetics. To our knowledge, this is the first demonstration of the confocal-like 3D imaging of non-fluorescence nanoparticles with a high resolution and almost zero background. This technique is easy to implement and should greatly facilitate MNP studies and applications in biomedicine and biology.

Study of thermoelectric enhanced SERS and photocatalysis with ZnO-metal nanorod arrays

Herein,a thermoelectric induced surface-enhanced Raman scattering(SERS)substrate consisting of ZnO nanorod arrays and metal nanoparticles is proposed.The intensities of SERS signals are further enhanced by an order of magnitude and the limit of detection(LOD)for the molecules is reduced by at least one order of magnitude after the application of a thermoelectric potential.The enhancement mechanism is analyzed carefully and thoroughly based on the experimental and theoretical results,thus proving that the thermoelectric-induced enhancement of the SERS signals should be classified as a chemical contribution.Furthermore,it is proved that the electric regulation mechanism is universally applicable,and the fabricated substrate realizes enormous enhancements for various types of molecules,such as rhodamine 6G,methyl orange,crystal violet,amaranth,and biological molecules.Additionally,the proposed electric-induced SERS(E-SERS)substrate is also realized to monitor and manipulate the plasmon-activated redox reactions.We believe that this study can promote the course of the research on ESERS and plasmon-enhanced photocatalysts.

Fabrication of cost-effective, highly reproducible large area arrays of nanotriangular pillars for surface enhanced Raman scattering substrates

Development of cost-effective, highly reproducible non-conventional fabrication techniques for anisotropic metal nanostructures is essential to realizing potential applications of plasmonic devices, photonic devices, and surface enhanced Raman scattering （SERS） phenomenon based sensors. This report highlights the fabrication of nanotriangle arrays via nanoimprinting to overcome difficulties in creating large-area SERS active substrates with uniform, reproducible Raman signals. Electron beam lithography of anisotropic nanostructures, formation of arrays of nanotriangles in silicon and the transfer of triangular shapes to polymethylmethacrylate （PMMA） sheets via nanoimprinting have not been reported elsewhere. The reuse of silicon masters offers potential for production of low cost SERS substrates. The SERS activity and reproducibility of nanotriangles are illustrated and a consistent average enhancement factor of up to -2.9 × 1011, which is the highest value reported for a patterned SERS substrate, is achieved.

Near-Infrared Absorption Imaging and Processing Technologies Based on Gold Nanorods

Noble metal nanoparticles with localized surface plasmon resonance （LSPR） properties are widely used as optical sensors in biochemical detection and medical diagnosis. In this paper, we propose an effective determination method to measure the LSPR absorption intensity of gold nanorods （GNRs）. A near-infrared （NIR） imaging system is established, and an NIR absorption image of the multiple samples of the colloidal GNRs is captured. Then, the LSPR absorption intensities of these samples are obtained by calculating the average grayscale of the target areas based on the NIR image processing technology. By using this method, the LSPR absorption intensities of the multiple samples are determined all at once, and their accuracy is as high as that obtained by using spectrophotometry. These results suggest that this method is an efficient multi-channel determination technique with high-throughput sensing applications.

In situ irradiated X-ray photoelectron spectroscopy on Ag-WS2 heterostructure for hydrogen production enhancement

The hot electron transition of noble materials to catalysis accelerated by localized surface plasmon resonances(LSPRs)was detected by in situ irradiated X-ray photoelectron spectroscopy(ISI-XPS)in this article.This paper synthesized an Ag Nanowire(AgNW)@WS2 core-shell structure,with an ultra-thin shell of WS_(2)(3-7 nm),and characterized its photocatalytic properties.The AgNW@WS_(2) core-shell structure exhibited different surface-enhanced Raman spectroscopy(SERS)effects by changing shell thickness,indicating that the effect of AgNW could be controlled by WS2 shell.Furthermore,the hydrogen production of AgNW@WS2 could reach to 356%of that of pure WS2.The hot electrons arising from the LSPRs effect broke through the Schottky barrier between WS_(2) and AgNW and transferred to the WS2 shell,whose photocatalytic effect was thus enhanced.In addition,when the LSPRs effect was intensified by reducing the shell thickness,the hot electron transition of noble materials to catalysis was accelerated.

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.