Localized Surface Plasmons In Nanoparticles Research Articles

Determining Quasi-Equilibrium Electron and Hole Distributions of Plasmonic Photocatalysts Using Photomodulated X-ray Absorption Spectroscopy.

Most photocatalytic and photovoltaic devices operate under broadband, constant illumination. Electron and hole dynamics in these devices, however, are usually measured by using ultrafast pulsed lasers in a narrow wavelength range. In this work, we use excited-state X-ray theory originally developed for transient X-ray experiments to study steady-state photomodulated X-ray spectra. We use this method to attempt to extract electron and hole distributions from spectra collected at a nontime-resolved synchrotron beamline. A set of plasmonic metal core-shell nanoparticles is designed as the control experiment because they can systematically isolate photothermal, hot electron, and thermalized electron-hole pairs in a TiO2 shell. Steady-state changes in the Ti L2,3 edge are measured with and without continuous-wave illumination of the nanoparticle's localized surface plasmon resonance. The results suggest that within error the quasi-equilibrium carrier distribution can be determined even from relatively noisy data with mixed excited-state phenomena. Just as importantly, the theoretical analysis of noisy data is used to provide guidelines for the beamline development of photomodulated steady-state spectroscopy.

Plasmonic Photocatalysis Driven by Indirect Gold Excitation Via Upconversion Nanoparticle Emission Monitored In Situ by Surface-Enhanced Raman Spectroscopy

Lanthanide-doped upconversion nanoparticles (UCNPs) absorb low-energy photons, in the near-infrared region (NIR), and emit high-energy photons, in the visible or ultraviolet region (UV/Vis). The higher energy radiation emissions can be used to promote plasmonic photocatalytic reactions by coupling UCNPs with plasmonic nanoparticles. Thus, in this work, highly crystalline β-NaYF4:Yb3+,Er3+@NaYF4:Nd3+@NaYF4 UCNPs capped with an amino-modified nanosized silica shell were coupled with Au nanospheres (13 ± 2 nm). The plasmonic-driven dimerization of 4-aminothiophenol (4-ATP) to 4,4′-dimercaptoazobenzene (DMAB) was carried out solely by using the UCNP visible emissions to excite the Au nanoparticle localized surface plasmon resonance band. The reaction was monitored in situ through surface-enhanced Raman spectroscopy (SERS) and optimal conditions were achieved in order to eliminate secondary influences during spectra acquisition. The SERS substrates containing either UCNPs@SiO2-NH2/Au or SiO2-NH2/Au nanoparticles were prepared by the drop-cast method in silicon substrates. In the studied reaction conditions, plasmonic photocatalytic activity was observed only in the substrates containing UCNPs and Au nanoparticles. The plasmonic-driven reaction was achieved by UCNPs excitation with a 980 nm laser (25.7 mW), aligned in a Raman spectrometer, only after 5 s of exposition. Interactive document mapping (IDMAP), which is an unsupervised pattern recognition method, was applied to analyze the numerous SERS spectra acquired during the plasmonic photocatalytic measurements. The high values found for the silhouette coefficient (0.88 for the Si_SiO2-NH2/Au and 0.76 for the Si_NYF@SiO2-NH/Au substrate) indicate that strong discrimination among the Raman spectra was achieved. Thus, through IDMAP, it was observed that the SERS spectra obtained for the substrates containing either UCNPs@SiO2-NH2/Au or SiO2-NH2/Au corresponded to spectral features, respectively, from the DMAB product and the 4-ATP reagent, evidencing that, in the optimized reaction conditions, the dimerization occurred only through the interaction of the UCNPs with the Au nanospheres.

Study of fluorescence lifetime modification for car lighting by single gold nanoparticle localized surface plasmon

Study of fluorescence lifetime modification for car lighting by single gold nanoparticle localized surface plasmon

Study of fluorescence lifetime modification for car lighting by single gold nanoparticle localized surface plasmon

Interactions between fluorephores and surface plasmon was investigated by a custom-built fluorescence lifetime system. Gold nanoparticle with double-stranded DNA on the surface was utilized to exactly control the distance between fluorephores and the nanoparticle. We calculated surface plasmon-induced changes in the radiative decay rate constant and the quenching rate constant. The results revealed that the distance between the fluorephore and the nanoparticle strongly affected the radiative decay rate and the quenching rate. With an increase in the distance, the radiative decay rate decreased while the quenching rate increased. This suggests that the distance between fluorephores and surface plasmon plays an important role in fluorescence lifetime modification. The results also indicated that the fluorescence lifetime of the fluorephores can be significantly modified by surface plasmon resonance. This indicates that surface plasmon resonance can be used as a tool to control the fluorescence lifetime of fluorephores for sensing applications.

Sensitivity enhancement of nanoparticle localized surface plasmon resonance pressure sensor based on the MoS2 monolayer for ultra-wide range pressure detection

The next generation of optical pressure sensors should be highly sensitive, and have wide-ranging pressure sensing detection. The monolayer MoS2 has been considered as an excellent material with exceptional mechanical, physical, electronic and chemical properties, which is significantly different from the properties of graphene. In this paper, the properties of the MoS2 monolayer according to the placement of silver nanoparticles on the surface have been used to design a pressure sensor that can act based on localized surface plasmon resonance. The MoS2 monolayer sensitivity to stress and variations the properties in proportion to the applied pressure, increases the possibility of using it as a pressure sensor. High pressure range, nanoscale and integration capabilities are important features of this sensor. In this sensor the change in the resonance frequency is proportional to the pressure range which the structure parameters including the shape of the nanoparticles, the material and radius of the nanoparticles, the angle of the incoming light and the presence of the mos2 monolayer by considering and optimizing are provided. For mechanics section calculation, we used the FEM method, and for optical behavior, the FDTD method. Measurable pressure range is less than 1 Gpa with 11 nm/GPa sensitivity for this sensor.

NiSe and CoSe Topological Nodal-Line Semimetals: A Sustainable Platform for Efficient Thermoplasmonics and Solar-Driven Photothermal Membrane Distillation.

The control of heat at the nanoscale via the excitation of localized surface plasmons in nanoparticles (NPs) irradiated with light holds great potential in several fields (cancer therapy, catalysis, desalination). To date, most thermoplasmonic applications are based on Ag and Au NPs, whose cost of raw materials inevitably limits the scalability for industrial applications requiring large amounts of photothermal NPs, as in the case of desalination plants. On the other hand, alternative nanomaterials proposed so far exhibit severe restrictions associated with the insufficient photothermal efficacy in the visible, the poor chemical stability, and the challenging scalability. Here, it is demonstrated the outstanding potential of NiSe and CoSe topological nodal-line semimetals for thermoplasmonics. The anisotropic dielectric properties of NiSe and CoSe activate additional plasmonic resonances. Specifically, NiSe and CoSe NPs support multiple localized surface plasmons in the optical range, resulting in a broadband matching with sunlight radiation spectrum. Finally, it is validated the proposed NiSe and CoSe-based thermoplasmonic platform by implementing solar-driven membrane distillation by adopting NiSe and CoSe nanofillers embedded in a polymeric membrane for seawater desalination. Remarkably, replacing Ag with NiSe and CoSe for solar membrane distillation increases the transmembrane flux by 330% and 690%, respectively. Correspondingly, costs of raw materials are also reduced by 24 and 11 times, respectively. The results pave the way for the advent of NiSe and CoSe for efficient and sustainable thermoplasmonics and related applications exploiting sunlight within the paradigm of the circular blue economy.

Sensitivity enhanced D-type large-core fiber SPR sensor based on Gold nanoparticle/Au film co-modification

A D-type large core optical fiber sensor with high sensitivity and good stability based on the coupling of gold nanoparticles and Au film was proposed and demonstrated by simulation and experiments. The proposed sensor is numerically simulated based on the finite element method. The simulation shows that the electric field intensity of the gap coupling between gold nanoparticles and Au film is 4–5 times higher than that of Au film, and the electric field intensity on the surface of gold nanoparticles is twice as strong as that on the surface of Au films. The electric field coupling effect between the Au film surface plasmon resonance (SPR) and the gold nanoparticle localized surface plasmon resonance (LSPR) can improve the refractive index sensitivity of the sensor. Experimental results show that the refractive index sensitivity of D-type optical fiber/Au film/gold nanoparticles sensor reaches 3074 nm/refraction index unit (RIU), which is 1.4 times that of D-type optical fiber/Au film sensor. SPR–LSPR coupling effect is a good method to improve the sensing performance of optical fiber sensors, especially for detecting the refractive index changes of surrounding media. Compared with existing similar biosensors, the designed biosensor has higher sensitivity and the sensor proposed in this paper has great application prospects in the field of biological detection.

Tunable magneto-optical linear and circular dichroism spectra for a dimer of core–shell prolate spheroids

Searching for methods to modulate localized surface plasmons in nanoparticles is one of the challenging and important areas in plasmonic effects. Surface plasmons can be influenced in a magnetic field due to the additional magnetic force on the electrons, resulting in some magneto-optical phenomena. In this paper, we study the magneto-optical properties of core–shell spheroidal nanoparticles. We apply the coupled dipole method to calculate the absorption and linear and circular dichroism spectra of a single nanoparticle and a dimer of nanoparticles. The polarizability tensor of spherical nanoparticles is extended for spheroidal nanoparticles, and, by utilizing it, we show that the single spheroidal nanoparticle reveals circular dichroism. It is reported that core size and nanoparticles axis direction can be used to engineer the whole spectrum for both configurations.

Sharp selective scattering of red, green, and blue light achieved via gain material's loss compensation.

Frequency-selective scattering of light can be achieved by metallic nanoparticle's localized surface plasmon resonance (LSPR). And this property may find an application in a transparent projection screen: ideally, specially designed metallic nanoparticles dispersed in a transparent matrix only selectively scatter red, green and blue light and transmit the visible light of other colors. However, optical absorption and surface dispersion of a metallic nanoparticle, whose size is comparable or smaller than mean free path of electrons in the constituent material, degenerate the desired performance by broadening the resonance peak width (i.e., decreasing frequency-selectivity) and decreasing light scattering intensity. In this work, it is shown that the problem can be solved by introducing gain material. Numerical simulations are performed on nanostructures based on silver (Ag), gold (Au) or aluminum (Al) with or without gain material, to examine the effect of gain material and to search for suitable structures for sharp selective scattering of red, green and blue light. And it is found that introducing gain material greatly improves performance of the structures based on Ag or Au except the structures based on Al. The most suitable structures for sharp selective scattering of red, green and blue light are, respectively, found to be the core-shell structures of silica/Au (core/shell), silica/Ag and Ag/silica, all with gain material.

Selective Scattering of Blue and Red Light Based on Silver and Gold Nanocubes

Selective scattering of red, green, and blue light and transmitting other visible light to achieve a transparent projection screen has been proposed based on metallic nanoparticle's localized surface plasmon resonance (LSPR). However, of the many proposed structures, dielectric (TiO2) substrate/silver (Ag) nanocube structure was only demonstrated to selectively scatter blue light in the backward direction. Therefore, for this setup, on one hand, it is of interest to enhance selective backward scattering of red light, and on the other hand, it is of interest to investigate ways of selective forward scattering of both blue and red light. Selective backward scattering may be used in applications such as heads up display (HUD), while selective forward scattering may be applied to, for example, display advertisements on shop windows. In this work, through numerical simulation, forward and backward scattering properties of dielectric substrate/Ag (or gold) nanocube structures were investigated. Based on these properties, three designs are proposed which can achieve selective scattering of blue and red light in forward or backward or both directions.

Resonant scattering of green light enabled by Ag@TiO2 and its application in a green light projection screen

The ability to selectively scatter green light is essential for an RGB transparent projection display, and this can be achieved by a silver-core, titania-shell nanostructure (Ag@TiO2), based on the metallic nanoparticle's localized surface plasmon resonance. The ability to selectively scatter green light is shown in a theoretical design, in which structural optimization is included, and is then experimentally verified by characterization of a transparent film produced by dispersing such nanoparticles in a polymer matrix. A visual assessesment indicates that a high-quality green image can be clearly displayed on the transparent film. For completeness, a theoretical design for selective scattering of red light based on Ag@TiO2 is also shown.

Sculpting Fano Resonances To Control Photonic-Plasmonic Hybridization.

Hybrid photonic-plasmonic systems have tremendous potential as versatile platforms for the study and control of nanoscale light-matter interactions since their respective components have either high-quality factors or low mode volumes. Individual metallic nanoparticles deposited on optical microresonators provide an excellent example where ultrahigh-quality optical whispering-gallery modes can be combined with nanoscopic plasmonic mode volumes to maximize the system's photonic performance. Such optimization, however, is difficult in practice because of the inability to easily measure and tune critical system parameters. In this Letter, we present a general and practical method to determine the coupling strength and tailor the degree of hybridization in composite optical microresonator-plasmonic nanoparticle systems based on experimentally measured absorption spectra. Specifically, we use thermal annealing to control the detuning between a metal nanoparticle's localized surface plasmon resonance and the whispering-gallery modes of an optical microresonator cavity. We demonstrate the ability to sculpt Fano resonance lineshapes in the absorption spectrum and infer system parameters critical to elucidating the underlying photonic-plasmonic hybridization. We show that including decoherence processes is necessary to capture the evolution of the lineshapes. As a result, thermal annealing allows us to directly tune the degree of hybridization and various hybrid mode quantities such as the quality factor and mode volume and ultimately maximize the Purcell factor to be 104.

Single Gold Nanoparticle Localized Surface Plasmon Resonance Spectral Imaging for Quantifying Binding Constant of Carbohydrate–Protein Interaction

Quantifying carbohydrate-protein (ligand-receptor) interactions is important to understand diverse biological processes and to develop new diagnostic and therapeutic methods. We develop an approach to quantitatively study carbohydrate-protein interactions by Au nanoparticle localized surface plasmon resonance (LSPR) peak position shift at the single particles level. Unlike the previous techniques for single particle LSPR spectral imaging, only the first-order streak of an individual nanoparticle is needed to extract a LSPR spectrum, which has great potential to increase throughput to 500 single particle spectra in each frame. LSPR peak shift of protein modified single Au nanoparticles is found to be a function of its ligand concentration, which can be used to fit the binding constants of the interactions. The moderate interactions of Antithrombin III (AT III) and heparins including low molecular weight heparin (LMWH) are determined as well as the strong interaction of transferrin and antitransferrin and the weak interaction of bovine serum album (BSA) and heparin. The measured binding constants of transferrin to antitransferrin, heparin and LMWH to AT III, and BSA to heparin are (3.0 ± 0.6) × 10(9) M(-1), (3.1 ± 0.3) × 10(6) M(-1), (8.0 ± 0.5) × 10(5) M(-1), and (5.1 ± 0.1) × 10(3) M(-1), respectively, which are in good agreement with the reported values.

Effect of particle properties and light polarization on the plasmonic resonances in metallic nanoparticles

The resonance behavior of localized surface plasmons in silver and gold nanoparticles was studied in the visible and near-infrared regions of the electromagnetic spectrum. Arrays of nano-sized gold (Au) and silver (Ag) particles with different properties were produced with electron-beam lithography technique over glass substrates. The effect of the particle size, shape variations, period, thickness, metal type, substrate type and sulfidation were studied via transmission and reflectance measurements. The results are compared with the theoretical calculations based on the DDA simulations performed by software developed in this study. We propose a new intensity modulation technique based on localized surface plasmons in nanoparticles with asymmetric shapes.

Local 2PPE-yield enhancement in a defined periodic silver nanodisk array

Well-prepared periodic arrays of silver nanoparticles are investigated by means of linear and non-linear photoemission electron microscopy. The structures show homogeneous photoemission for UV excitation in the linear photoemission regime whereas striking inhomogeneities are mapped in the case of the nonlinear (2 photon) excitation using ultrashort 400 nm laser pulses. A detailed analysis enables to assign these inhomogeneities to defect induced electron momentum transfer processes only effective for the 2 photon excitation process. We propose this mechanism to be of relevance for the appearance of so-called hot spots in nonlinear photoemission as identified in other 2PPE studies in the past. Furthermore, the complementarity between all-optical studies and nonlinear photoemission studies of localized surface plasmons in nanoparticles is discussed.

Surface enhanced Raman scattering phenomenon

Surface enhanced Raman scattering and surface enhanced fluorescence phenomena are the result of resonance excitation of localized surface plasmons in nanoparticles of some metals. By appropriate choice of the shape and size of metallic nanoparticles, the kind of adsorbed molecules and the wavelength of the exciting light, it is possible to achieve enhancement of the intensity of Raman scattering equal to 1012-1014. This means that only some molecules inside the exciting light beam are sufficient to record the Raman spectrum. Electromagnetic and chemical mechanisms of enhancement of Raman scattered light and methods of roughness investigation of surfaces exhibiting this promising phenomenon are described in this paper. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)