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Rare-earth-doped up-converters with Yb3+ as a sensitizer show a high internal conversion efficiency under the excitation at wavelength λ = 980 nm. For the solar cell applications of up-converters, ...

Nanoparticles of refractory compounds represent a class of stable materials showing a great promise to support localized surface plasmon resonances (LSPRs) in both visible and near infrared (NIR) spectral regions. It is still challenging to rationally tune the LSPR band because of the difficulty to control the density of charge carriers in individual refractory nanoparticles and maintain the dispersity of nanoparticles in the processes of synthesis and applications. In this work, controlled chemical transformation of titanium dioxide (TiO2) nanoparticles encapsulated with mesoporous silica (SiO2) shells to titanium nitride (TiN) via nitridation reaction at elevated temperatures is developed to tune the density of free electrons in the resulting titanium-oxide-nitride (TiOxNy) nanoparticles. Such tunability enables a flexibility to support LSPR-based optical absorption in the synthesized TiOxNy@SiO2 core-shell nanoparticles across both the visible and NIR regions. The silica shells play a crucial role in preventing the sintering of TiOxNy nanoparticles in the nitridation reaction and maintaining the stability of TiOxNy nanoparticles in applications. The LSPR-based broadband absorption of light in the TiOxNy@SiO2 nanoparticles exhibits strong photothermal effect with photo-to-thermal conversion efficiency as high as ~ 76%.

Developing a simple structure using low-cost material that enables both large-scale fabrication and broadband absorption response is highly desirable but very challenging for achieving high-performance metamaterial absorber. Herein, we propose and numerically investigate an ultra-broadband and wide-angle insensitive perfect metamaterial absorber in the ultraviolet to near-infrared (UV–NIR) region based on a simple metal–dielectric–metal structure. The proposed absorber structure consists of a periodic array of a tungsten hexagonal prism and a tungsten ground plane separated by a silicon dioxide dielectric substrate. The proposed absorber achieves an ultra-broadband absorption response in the range of 275–1000 nm with an absorptivity above 90 $$\%$$ and a relative bandwidth of 106.8 $$\%$$ at normal incidence, which covers from the UV to NIR region. The absorption efficiency is maintained with the figure of merit $$\eta _{OBW}$$ higher than 90 $$\%$$ for a wide incident angle up to 40 $$^{o}$$ for transverse electric (TE) polarization and 65 $$^{o}$$ for transverse magnetic (TM) polarization. The effects of structural parameters and different metallic materials on the absorption performance are presented. In addition, the physical mechanism is analyzed using the surface density and distributions of electric and magnetic fields that are attributed to both localized surface plasmon (LSP) and propagating surface plasmon (PSP) resonances. Owing to outstanding merits of simple structure, low cost, and high absorption performance, the designed absorber can be suitable for many applications in the UV–NIR spectrum such as thermal emitters and solar cells.

In plasmonic catalysis, localized surface plasmons can be leveraged to drive chemical reactions. This approach is promising for catalyzing many challenging reactions at relatively low temperatures ...

Doped metal oxide nanocrystals (NCs) exhibit tunable localized surface plasmon resonances (LSPRs) in the infrared spectral region. Compared to the binary oxides commonly studied, plasmonic NCs deri...

We report a novel type of electromagnetically induced transparency (EIT) analogue based on metamaterials (MMs) with hybrid structures, in which spiral and cut-wire structures serve as bright-mode resonators with the spoof electric localized surface plasmons and electric dipole resonance. With the simulations and experiments, the EIT analogue generated by the frequency detuning and hybridization between the resonators is verified. The simulated surface charge density and electric and magnetic field distributions, together with the theoretical analysis based on the Lorentz oscillator model, reveal the principle of the EIT analogue. Moreover, the transmission window of the MM demonstrates linear dependence on the refractive index’s change of surrounding media, showing the potential as a tool for environmental detection.

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 WS2 (3 ∼ 7 nm), and characterized its photocatalytic properties. The AgNW@WS2 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 WS2 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.

Lanthanide-doped nanoparticles have great potential for energy conversion applications, as their optical properties can be precisely controlled by varying the doping composition, concentration, and surface structures, as well as through plasmonic coupling. In this Perspective we highlight recent advances in upconversion emission modulation enabled by coupling upconversion nanoparticles with well-defined plasmonic nanostructures. We emphasize fundamental understanding of luminescence enhancement, monochromatic emission amplification, lifetime tuning, and polarization control at nanoscale. The interplay between localized surface plasmons and absorbed photons at the plasmonic metal-lanthanide interface substantially enriches the interpretation of plasmon-coupled nonlinear photophysical processes. These studies will enable novel functional nanomaterials or nanostructures to be designed for a multitude of technological applications, including biomedicine, lasing, optogenetics, super-resolution imaging, photovoltaics, and photocatalysis.

Cadmium telluride (CdTe) thin films with a nanocolumnar morphology were grown on glass substrates using the Sublimated Vapor Effusion Deposition technique and a rotational source in counter-rotation with respect to the substrate. Afterward, it was proceeded to coat with silver nanoparticles whose average size was of ~ 100 ± 40 nm. X-ray diffraction analysis showed that all samples presented the zinc-blend structure with a preferred orientation of (111), with a crystallite size of ~ 52 nm, and that they were under tensile stress. The bandgap value was EG = 1.53 eV and the Urbach energy E0 ~ 13.2 meV. The porosity value was estimated at ~ 0.0562 (5.6%). A Localized Surface Plasmon Resonances effect was presented for the Ag nanoparticles near the wavelengths close to 548 nm and 660 nm, and this resulted in improved light absorption in the CdTe nanocolumnar layer compared to samples grown only with a CdTe nanocolumnar structure.

This paper proposes a novel design of plasmonic perovskite solar cell (PSC). It consists of an anti-reflective glass of fluorine-doped tin oxide (FTO), a compact buffer layer of n-type titanium dioxide (TiO2), an absorbing thin-film layer of perovskite (MAPbI3) integrated with gold (Au) nanospheres, a layer of p-type doped spiro-OMeTAD, and a layer of the cathode on aluminum (Al). This multilayer design’s primary purpose is to allow the light to enter the PSC with the minimum reflection and trap it in the active layer due to the presence of Au nanospheres. In this layer, the higher efficiency of PSC is achieved by localized surface plasmon resonances (LSPRs) in the wavelength range from 300 to 1100 nm. A reflective Al layer is used at the bottom of the device to reflect the light into the upper layers to considerably enhance the PSC absorption. The three-dimensional finite-difference time-domain method was conducted to find the best solution to Maxwell’s equations so that the best thickness and radius can be selected for each layer and Au nanospheres, respectively. Proper physical dimensions and Au nanospheres played a significant role in numerically indicating that the proposed structures are 60% more absorbent than the other conventional PSCs. In-house simulation software is used to approximate the solar cell by applying the finite element method to develop solutions for the drift–diffusion and Poisson’s equations. The examinations of the previous studies revealed that the current study is the first study that has simulated the real model of Auger recombination in perovskite. The results indicated that the proposed PSC embedded with Au nanospheres has the following properties: the built-in potential of 3.16 V, short-circuit current of 27.97 mA/cm2, the open-circuit voltage of 1 V, maximum power of 24.84 mW/cm2, fill-factor of 0.88, the conduction band of 3 eV, electron quasi-Fermi level of 2.5 eV, the hole quasi-Fermi level of 0.6 eV, and efficiency of 24.84%. Finally, the suggested PSC has performed 62% more efficient than conventional PSCs.

It is essential to realize a Raman measurement technique without artifact or fluorescence signals for high-quality and reliable data in a valid molecular-level analysis and interpretation. This requirement applies especially to a molecule with strong fluorescence like porphyrin. Here, the surface of a gold substrate performs better as a DCDR substrate for tetraphenylporphyrin than other surfaces, such as tantalum, indium tin oxide glass, or aluminium. Polarized Raman spectra of tetraphenylporphyrin demonstrated the oriented deposition of porphyrin crystallites on the Au substrate using the drop coating technique. The emission anisotropy suggests that the deposited crystallites are arranged outward radially with the porphyrin ring orientation. The orientation is signed by the NH⋯HN axis that is parallel to the radial vector along the X-axis. Moreover, it also demonstrates high chemical stability after preservation and repeated measurements. The Raman signal on a gold substrate is enhanced more than on other substrates beyond mere preconcentration of analytes or the coffee-ring effect only, which might be due to the contribution of the SERRS effect. This effect will be discussed based on the interactions among localized surface plasmons, vibronic transitions, and Raman active vibrational modes.

Due to the relatively low photo-thermal conversion efficiency and poor tumor targeting capacity, phototheranostic nanoagents encounter some challenges in cancer photothermal therapy. To address this problem, in the current research we developed vacancy-rich MoSe2-x (0 ≤ x ≤ 1) nanoflowers (MNFs) with molecular 2-deoxy-D-glucose (2-DG) as the activity target, which could be used as a novel phototheranostic nanoagent in the photoacoustic imaging guided chemo-photothermal synergistic therapy. This selenium-deficient structure endows MNFs with high photothermal conversion efficiency (41.7%) due to the strong localized surface plasmon resonances. Besides, the surface linked 2-DG molecules and the flower-like morphology in the nanoagents promoted the targeting effect (active and passive), thus facilitating the efficient concentration of the nanoagents within the tumor site. Both in vitro and in vivo anti-tumor experiments have demonstrated the high synergistic efficacy promoted by MNFs and complete tumor eradication with lower administration dosages could be achieved. This rational design of nanoparticles not only provided the paradigm of high therapeutic efficacy of a chemo-photothermal protocol for precise cancer theranostics, but also expanded the scope of nanomedical applications using semiconductor-based nanoplatforms through well-defined designing of their microstructures and physiochemical properties.

Sustainability drives modern technology. Practices ensuring efficient resource utilization, guided resource handling and promotion of negative ecological footprint befittingly implicate “growth”. With manufacturing being one of the major contributing sectors to a nation's economy, adopting greener fabrication processes, the production of cleaner energy and the development of efficient products are important to achieve technological translation. Herein, a bi-functional hybrid (semiconductor–metal) system comprising zinc oxide nano leaves uniformly decorated with gold nano islands was synthesized using a one-step, room temperature biosynthetic reduction strategy. Being a one-step process, the number of reaction reagents and auxiliary byproducts was limited while material engineering ensured efficient product performance derived from coexistence of localized surface plasmon, semiconduction and their synergistic interaction. Detailed characterization of the as synthesized hybrid system concludes presence of defect states, crystalline nature, engineered band gap, pertinent chemical elemental state and interfacial charge distribution features. The hybrid nanostructures show strong surface-enhanced Raman scattering (SERS) characteristics for model R6G molecules (LOD: 10−10 M). Marked with the presence of symmetric and non-totally symmetric Raman vibrations, the role of electromagnetic and chemical enhancement was equally attributed to improved signal strengths. Contribution from charge transfer was verified using off resonance measurements and by studying the photolytic behavior of the nano-hybrid system. The self-cleaning feature of the nanohybrid was tested against a model bacterial contaminant S. aureus, which was killed with 100% efficiency using ∼60 μg ml−1 under natural sunlight.

This review describes recent studies on coupled plasmonic systems for controlling plasmon dynamics and molecular detection using spectral modulations. The plasmon dephasing time can be controlled by weak and strong coupling regimes between the plasmonic nanostructures or localized surface plasmon resonances (LSPRs) and the other optical modes such as microcavities. The modal coupling induces near-field enhancement by extending the plasmon dephasing time to increase the near-field enhancement at certain wavelengths resulting in the enhancement of molecular detection. On the other hand, the interaction between LSPR and molecular excited or vibrational states also modulates the resonance spectrum, which can also be used for detecting a small number of molecules with a subtle change in the spectrum. The spectral modulation is induced by weak and strong couplings between LSPRs and the electronic or vibrational states of molecules, and this method is sensitive enough to measure a single molecule.

Two-dimensional metal carbides and nitrides, known as MXenes, are an emerging class of materials that are promising for a variety of applications. In this work, using time-dependent density functional theory calculations, we investigate the localized surface plasmon resonances and electric field confinement of pristine and surface-terminated [fluorinated (F) and/or oxidized (O)] mono-layered titanium carbide (Ti3C2) MXene nanoclusters. We found that the nanoclusters (Ti48C32, Ti48C32F32, and Ti48C32O32) exhibit broadband photoabsorption spectra and localized surface plasmon resonances even at low energy in the infrared region (a spectral range of interest for molecular sensing). In addition, the nanoclusters produce a sizable electric field confinement on the surface with a strength that varies with the F/O surface termination. Our findings provide significant theoretical insight into the optical and plasmonic properties of MXene nanoclusters.

Highlights Development of Au nanostar@AIE nanodots photosensitizers for theranostic applications.Achieving excellent metal-enhanced fluorescence and singlet oxygen generation efficiency simultaneously.Mechanism study of the role of FRET on metal-enhanced singlet oxygen generation. Supplementary Information The online version of this article (10.1007/s40820-020-00583-2) contains supplementary material, which is available to authorized users., Dual-functional aggregation-induced photosensitizers (AIE-PSs) with singlet oxygen generation (SOG) ability and bright fluorescence in aggregated state have received much attention in image-guided photodynamic therapy (PDT). However, designing an AIE-PS with both high SOG and intense fluorescence via molecular design is still challenging. In this work, we report a new nanohybrid consisting of gold nanostar (AuNS) and AIE-PS dots with enhanced fluorescence and photosensitization for theranostic applications. The spectral overlap between the extinction of AuNS and fluorescence emission of AIE-PS dots (665 nm) is carefully selected using five different AuNSs with distinct localized surface plasmon (LSPR) peaks. Results show that all the AuNSs can enhance the 1O2 production of AIE-PS dots, among which the AuNS with LSPR peak at 585 nm exhibited the highest 1O2 enhancement factor of 15-fold with increased fluorescence brightness. To the best of our knowledge, this is the highest enhancement factor reported for the metal-enhanced singlet oxygen generation systems. The Au585@AIE-PS nanodots were applied for simultaneous fluorescence imaging and photodynamic ablation of HeLa cancer cells with strongly enhanced PDT efficiency in vitro. This study provides a better understanding of the metal-enhanced AIE-PS nanohybrid systems, opening up new avenue towards advanced image-guided PDT with greatly improved efficacy. Supplementary Information The online version of this article (10.1007/s40820-020-00583-2) contains supplementary material, which is available to authorized users.

Exploitation of strong light-matter interactions in plasmonic systems is vital for both fundamental studies and the development of new applications, which enables exceptional physical phenomena and promotes potential applications in nanophotonics, information communication, and quantum information processing. Here, we present an analytic model of the interaction between localized surface plasmon resonances and excitons, where a semiclassical method is utilized. Two kinds of metal nanoparticles (nanosphere and nanoellipsoid) are considered in our study. We derive the relations between the plasmon-exciton coupling strength and the geometry and material parameters of the coupled systems when the nanoparticles are put in an excitonic medium, which give an important guide to achieve strong plasmon-exciton coupling. Rabi splittings and anticrossing behavior are also demonstrated in the calculated extinction spectra. Furthermore, we propose an analytic model to describe the strong coupling between excitons and plasmon in a core-shell nanorod structure which is widely used in experiments. Our study provides a simple yet rigorous prescription to both analyze and design plexcitonic systems aiming at strong light-matter interactions.

The development of Surface Enhanced Raman Scattering (SERS) promotes the wide application of Raman spectroscopy in chemical and biomolecular detection. SERS detection relies on analytes in close contact with the metallic surface, and therefore direct molecular trace detection in the liquid phase is difficult. In this paper, static liquid phase SERS detection was performed simply using a capillary without pre-functionalization. Gold nanoparticles (AuNPs) with an optimized size ensure localized surface plasmons in resonance with the exciting laser light. Grazing incidence and multimode interference in the capillary ensure that the longitudinal Raman signal is effectively excited and accumulated. An enhancement factor as high as 108 and a detection limit of 10−9 M of crystal violet in aqueous solution have been achieved.

In this article, we propose an ultra-compact microwave sensor based on an effective localized surface plasmon (ELSP) resonance for complex permittivity measurement of aqueous ethanol solution. The sensitivity of the sensor is dramatically enhanced thanks to the strong electromagnetic (EM) field coupling and enhancement of the ELSP in a deep-subwavelength scale. An equivalent circuit model of the sensor is established for analyzing the sensing mechanism, and the complex permittivity of the aqueous ethanol solution under test is extracted from the S-parameter through an empirical model. For demonstration, we successfully predict the complex permittivity of aqueous ethanol solution with an ethanol concentration of 0%–90% through simulations and experiments. This ELSP-based sensor features an ultra-compact size of $0.008\lambda _{0}^{2}$ and high sensitivity of 0.57% and can find many applications (liquid permittivity measurement, liquid testing, and so on) in highly integrated systems.

It is critically important that engineers be able to numerically simulate the scattering of electromagnetic radiation by bounded obstacles. Additionally, that these simulations be robust and highly...

Plasmon resonance modulation with an external magnetic field (magnetoplasmonics) represents a promising route for the improvement of the sensitivity of plasmon-based refractometric sensing. To this purpose, an accurate material choice is needed to realize hybrid nanostructures with an improved magnetoplasmonic response. In this work, we prepared core@shell nanostructures made of an 8 nm Au core surrounded by an ultrathin iron oxide shell (

Introducing nanostructured metals with ultraviolet plasmonic characters has attracted much attention for fabricating high performance optoelectronic devices in the shorter wavelength spectrum. In this work, platinum nanoparticles (PtNPs) with controlled plasmonic responses in ultraviolet wavelengths were successfully synthesized. To demonstrate the promising availability, PtNPs with desired sizes were deposited on a hexagonal ZnO microwire via Ga-doping (PtNPs@ZnO:Ga MW). Under ultraviolet illumination, typical near-band-edge emission of ZnO:Ga MW was considerably enhanced; meanwhile, the photocurrent is much larger than that of the bare MW. Thereby, the enhanced phenomena of a ZnO:Ga MW is related to localized surface plasmon resonances of the decorated PtNPs. A single MW with a hexagonal cross-section can be a potential platform to construct a whispering gallery mode (WGM) cavity due to its total inner wall reflection. Given this, the influence of PtNPs via ultraviolet plasmons on lasing features of the ZnO:Ga MW was tested. The lasing characteristics are significantly enhanced, including lasing output enhancement, a clear reduction of the threshold and the improvement of the quality factor. To exploit the working principle, PtNPs serving as powerful ultraviolet plasmons can couple with ZnO:Ga excitons, accelerating radiative recombination. Since fabricating stable, typical nanostructured metals with ultraviolet plasmons remains a challenging issue, the results illustrated in the work may offer a low-cost and efficient scheme for achieving plasmon-enhanced wide-bandgap semiconductor based ultraviolet optoelectronic devices with excellent performances.

Shell-isolated nanoparticles (SHINs) have attracted increasing interest for non-interfering plasmonic enhanced sensing in fields such as materials science, biosensing, and in various electrochemical systems. The metallic core of these nanoparticles is isolated from the surrounding environment preventing direct contact or chemical interaction with the metal surface, while still being close enough to enable localized surface plasmon enhancement of the Raman scattering signal from the analyte. This concept forms the basis of the shell isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) technique. To date, the vast majority of SHIN designs have focused on SiO2 shells around spherical nanoparticle cores and there has been very limited published research considering alternatives. In this article, we introduce a new polymer-based approach which provides excellent control over the layer thickness and can be applied to plasmonic metal nanoparticles of various shapes and sizes without compromising the overall nanoparticle morphology. The SHIN layers are shown to exhibit excellent passivation properties and robustness in the case of gold nanosphere (AuNP) and anisotropic gold nanostar (AuNS) core shapes. In addition, in situ SHINERS spectro-electrochemistry measurements performed on both SHIN and bare Au nanoparticles demonstrate the utility of the SHIN coatings. Correlated confocal Raman and SEM mapping was achieved to clearly establish single nanoparticle SERS sensitivity. Finally, confocal in situ SERS mapping enabled visualisation of the redox related molecular structure changes occurring on an electrode surface in the vicinity of individual SHIN-coated nanoparticles.

The dependence of field splitting characteristics of multilaminar plasmonic structure on its metallic components topology is analyzed. It is found that the coupling interaction between metallic-particle-centered localized surface plasmons generates a collective effect, collective metallic-particles-centered plasmons, to dominantly determine the plasmonic resonances of the structure. When the metallic particles filling ratio within the matrix is high, this collective effect may cause resonance splitting phenomenon and greatly enlarge the frequency range of field splitting enhancement, which is the physical mechanism and also the designing guideline for multilaminar plasmonic broadband perfect absorber. The surface plasmon polaritons are concurrently superimposed on the metallic-particles-centered collective effect to establish an inter-group coupling competition effect, which may strengthen or weaken the preexisting resonance processes through constructive or destructive field interference in between. This serves as the theoretical base for narrowband field splitting enhancement applications. Moreover, we have revealed the existence of the corresponding relationship between the specific field splitting resonance and those participating or dominating metallic particles involved, which provides the advantages to finely tailor field splitting characteristics through precise implantation of nanoparticles.

The absorption and reflection of electromagnetic waves by various particles in the earth’s atmosphere allow the passage of only certain electromagnetic wavelengths to reach the ground, called Earth’s atmosphere transparent window. In this study, perfect absorption was theoretically obtained in the range of near- and mid-infrared earth’s atmospheric transparency window using a simple absorber with metal-dielectric-metal structure. The numerical simulations showed the average absorption to reach 96.2% at wavelengths from 2000 to 6000 nm. Also, the broadband absorption was noticed and attributed to combined physical mechanisms, such as anti-reflection effect, localized surface plasmon polariton, propagating surface plasmon polarization, Fabry–Perot cavity and slow light mode. Meanwhile, the proposed absorber displayed simple-structure, low-cost, wide-angle, and polarization-independent. In sum, the proposed absorber might be useful for future applications related to atmospheric transparency window, such as remote sensing, energy harvesting, infrared detection, and stray light elimination.

Given the sub-wavelength trapping challenges in the optical tweezers, the plasmonic tweezers serve as a bridge by breaking the diffraction limit. Hence, the development of plasmonic tweezers can open up many potential applications in biology, medicine, and chemistry. In this paper, using localized surface plasmons (LSPs) of graphene nanodisk with a resonance frequency of 20 THz, we design a lab-on-a-chip optophoresis system, which can be utilized to effectively trap the nanoparticles. The LSPs of graphene nanodisk generate a large field gradient in the deep sub-wavelength area around the resonance frequency. We show that by an appropriate choice of chemical potentials of the graphene nanodisks, the strong optical near-field forces desired for trapping can be generated under the illumination of the THz source when the polystyrene (PS) nanoparticles are located in the vicinity of graphene nanodisks. Numerical simulations show that the designed system with graphene nanodisks of 250 nm in diameter and chemical potentials of $\mu _{c} = 0.6$ eV can trap the PS nanoparticles of 12 nm in diameter and larger with a THz source intensity of 19 $mW/{\mu } {m^{2}}$ , demonstrating acceptable sensitivities for variations in the nanoparticle diameter and refractive index. Moreover, at the same source intensity, the graphene nanodisks with $\mu _{c} = 0.7$ eV can trap the PS nanoparticle as small as 9.5 nm in diameter.

We present a strong coupling system realized by coupling the localized surface plasmon mode in individual silver nanogrooves and propagating surface plasmon modes launched by periodic nanogroove arrays with varied periodicities on a continuous silver medium. When the propagating modes are in resonance with the localized mode, we observe a √N scaling of Rabi splitting energy, where N is the number of propagating modes coupled to the localized mode. Here, we confirm a giant Rabi splitting on the order of 450-660 meV (N = 2) in the visible spectral range, and the corresponding coupling strength is 160-235 meV. In some of the strong coupling cases studied by us, the coupling strength is about 10% of the mode energy, reaching the ultrastrong coupling regime.

Molecular bond dissociation and formation reactions induced by localized surface plasmons of metal nanostructures are promising reactions in terms of the effective utilization of sunlight. The plas...

Plasmonic materials interact strongly with light to focus and enhance electromagnetic radiation down to nanoscale volumes. Due to this localized confinement, materials that support localized surface plasmon resonances are capable of driving energetically unfavorable chemical reactions. In certain cases, the plasmonic nanostructures are able to preferentially catalyze the formation of specific photoproducts, which offers an opportunity for the development of solar-driven chemical synthesis. Here, using plasmonic environments, we report inducing an intramolecular methyl migration reaction, forming 4-methylpyridine from N-methylpyridinium. Using both experimental and computational methods, we were able to confirm the identity of the N-methylpyridinium by making spectral comparisons against possible photoproducts. This reaction involves breaking a C-N bond and forming a new C-C bond, highlighting the ability of plasmonic materials to drive complex and selective reactions. Additionally, we observe that the product yield depends strongly on optical illumination conditions. This is likely due to steric hindrance in specific regions on the nanostructured plasmonic substrate, providing an optical handle for driving plasmonic catalysis with spatial specificity. This work adds yet another class of reactions accessible by surface plasmon excitation to the ever-growing library of plasmon-mediated chemical reactions.

Infrared detection technology has been widely applied in many areas. Unlike internal photoemission and the photoelectric mechanism, which are limited by the interface barrier height and material bandgap, the research of the hot carrier effect from nanometer thickness of metal could surpass the capability of silicon-based Schottky devices to detect mid-infrared and even far-infrared. In this work, we investigate the effects of physical characteristics of Cr nanometal surfaces and metal/silicon interfaces on hot carrier optical detection. Based on the results of scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis, the hot carrier effect and the variation of optical response intensity are found to depend highly on the physical properties of metal surfaces, such as surface coverage, metal thickness, and internal stress. Since the contact layer formed by Cr and Si is the main role of infrared light detection in the experiment, the higher the metal coverage, the higher the optical response. Additionally, a thicker metal surface makes the hot carriers take a longer time to convert into current signals after generation, leading to signal degradation due to the short lifetime of the hot carriers. Furthermore, the film with the best hot carrier effect induced in the Cr/Si structure is able to detect an infrared signal up to 4.2 μm. Additionally, it has a 229 times improvement in the signal-to-noise ratio (SNR) for a single band compared with ones with less favorable conditions.

We have discussed the impact on experimental characteristics which are important to detect localized surface plasmon peaks in EELS successfully, namely: the intensity of plasmonic signal, the signal to background ratio, and the signal to zero-loss peak ratio considering a limited dynamic range of the spectrometer camera.

Localized surface plasmons (LSPs) are a potentially valuable property for the practical use of small size metallic particles. Exploiting the LSPs in metallic nanoparticle (NP)-based solar cells was shown to increase the efficiency of solar panels. A large extinction cross section of NPs allows for high scattering of light at the surface of the panel, which reduces the panel thickness, allowing for small size and low-cost solar cells. In this paper, the extinction cross-section of spherical nanoparticles is studied and simulated numerically. Surface plasmons were first modeled using the Drude’s model then the scattering and absorption cross-sections were derived. Commercial3D simulation software was used to model the near field distribution of the three NP structures. A spherical nanoparticle made of silver was modeled first and the field distribution inside the sphere was presented. The extinction cross-section was also calculated. Two other structures were also presented; a silica NP was first coated with silver shell then a silver NP was coated with silica shell. These structures were studied to estimate the effects of the surroundings on the extinction cross-section. The results show that the silica NP coated with a silver shell provides a high extinction cross-section and can be considered as a good choice for the LSPs-based solar cells.