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The sun provides a plentiful and inexpensive source of carbon-neutral energy that has yet to be fully utilized. This is a major driving force behind the development of organic photovoltaic (OPV) materials and devices, which are expected to offer benefits such as low cost, flexibility, and widespread availability. For the photovoltaic performance enhancement of the inverted ZnO-nanorods (NR)/organic hybrid solar cells with poly(3-exylthiophene):(6,6)-phenyl-C61-butyric-acid-methylester (P3HT:PCBM) and poly (3,4-ethylenedioxythiophene):poly (styrenesulfonate) (PEDOT:PSS) active layers, gold nanoparticles (Au-NPs) were introduced into the interface between indium-thin-oxide cathode layer and ZnO cathode buffer layer, and the efficiency improvement was observed. It's worth noting that adding Au NPs had both a positive and negative impact on device performance. Au NPs were shown to be advantageous to localized surface plasmon resonance (LSPs) in the coupling of dispersed light from ZnO NRs in order to extend the light's path length in the absorbing medium. Although the light absorption in the active layer could be enhanced, Au NPs might also act as recombination centers within the active layer. To avoid this adverse effect, Au NPs are covered by the ZnO seeded layer to prevent Au NPs from direct contact with the active layer. The dominant surface plasmonic effect of Au NPs increased the photoelectric conversion efficiency from 2.4% to 3.8%.

Owing to the intense carrier recombination and limited optical absorption, the as‐fabricated CsPbBr3 visible light photodetectors (PDs) are far from practical application. In this work, we have demonstrated performance‐improved metal‐semiconductor‐metal (MSM) structured CsPbBr3 visible light PDs realized by the decoration of sputtered Au nanoparticles (NPs). It showed that the Au NPs on the CsPbBr3 exhibited synergistic benefits including improving the photogenerated charge carriers’ lifetime and enhancing the optical absorption of the CsPbBr3, both of which are fundamental factors for the performance‐improved PDs. Electrical characterizations showed that localized Schottky junctions formed at the Au NPs/CsPbBr3 interface. In addition, optical investigations showed that effective resonant coupling occurred between the localized surface plasmon resonance effects of Au NPs and excitons in the CsPbBr3. As a result, the on‐off switching of the Au‐decorated CsPbBr3 photodetector increased by 13 times compared with that of the pristine one. Meanwhile, the peak photo sensitivity of the CsPbBr3 photodetector was increased from 0.088 to 0.61 A W‐1 after the decoration of Au NPs. It is believed that the results shown in this work will provide pathways for fabricating high‐performance CsPbBr3 PDs and other similar devices in the future.

Localized surface plasmon interaction of colloidal gold nanoparticles and the resultant changes in the linewidth of plasmon bands are reported. The evolution of the plasmon band in colloids is investigated by increasing the number of particles per unit volume. The volume of the solvent is reduced from 15 to 3 ml by the simple evaporation method. It is observed that the linewidth of the plasmon band varies in a non-uniform manner, which is attributed to the interaction of plasmons from the surface of gold nanoparticles rather than aggregation effects. Indication of aggregation effects such as a progressive redshift in plasmon peak and continuous broadening of linewidth were absent. Gold nanoparticles are prepared using laser ablation of the gold target with nanosecond laser pulses using pure water as a solvent. Change in the linewidth of plasmon bands on colloidal gold nanoparticles with minimized size distribution prepared using laser fluences viz. 5.09, 10.19, 15.28, 20.38 and 25.48 J/cm2 are explored.

Tunable extraordinary optical transmission (EOT) with graphene is realized using a novel metallic ring–rod nested structure in the terahertz frequency regime. The generated double-enhanced transmission peaks primarily originate from the excitation of localized surface plasmon resonances (LSPRs). On using graphene, the resonating surface plasmon distribution changes in the reaction plane, which disturbs the generation of LSPRs. By regulating the Fermi energy (Ef) of the graphene to reach a certain level, an adjustment from bimodal EOT to unimodal EOT is obtained. As the Ef of the graphene integrated beneath the rod increases to 0.5 eV, the transmittance of the peak at 2.42 THz decreases to 6%. Moreover, the transmission peak at 1.77 THz virtually disappears due to the Ef increasing to 0.7 eV when the graphene is placed beneath the ring. The significant tuning capabilities of the bimodal EOT indicate its promising application prospects in frequency-selective surfaces, communication, filtering, and radar.

The performance improvement of solid-state triplet-triplet annihilation-based photon upconversion (TTA-UC) systems is required for the application to various solar devices. The performance can be improved by making use of the local strong electric field generated through the excitation of localized surface plasmon (LSP) resonance of metal nanostructures. However, since the improvement is effective only within the limited nanospace around nanoparticles (i.e., the near-field effect), a methodology for improving the performance over a wider spatial region is desirable. In this study, a significant improvement in the threshold light excitation intensity (Ith) (77% decrease) as the figure of merit and the upconverted emission intensity (6.3 times enhancement) in a solid-state TTA-UC film with a thickness of 3 μm was achieved by stacking the film with periodic Ag half-shell arrays. The highest-enhanced upconverted emission was obtained by tuning the diffuse reflectance peak, which results from the excitation of LSP resonance of the Ag half-shell arrays, to overlap well with the photoexcitation peak of the sensitizer in the TTA-UC film. The intensity of the enhanced upconverted emission was independent of the distance between the lower edge of the TTA-UC film and the surface of half-shell arrays in the nanometer order. These results suggest that the performance improvement was attributed to the photoexcitation enhancement of the sensitizer by elongating the excitation light path length inside the TTA-UC film, which was achieved through a strong backward scattering of the incident light based on the LSP resonance excitation (i.e., the far-field effect). In addition, the upconverted emission was improved using half-shell arrays comprising low-cost Al, although the enhancement factor was 3.5, which was lower than that of Ag half-shell arrays. The lower enhancement may be attributed to a decrease in the backward scattering of the excitation light owing to the intrinsic strong interband transition of Al at long visible wavelengths.

The optical and dielectric properties of plasmonic of Fe2O3/Au and Fe3O4/Au core/shell nanoparticles were studied using Finite Element computational approach. The optical response of these nanostructures was investigated through the computation of the real and the imaginary parts of the effective dielectric permittivity and the absorption cross-section in the visible-near infrared spectral range. Our findings are as follows. Firstly, we have compared our obtained numerical results with those predicted by Maxwell–Garnett effective medium theory. Secondly, the obtained results reveal that the localized surface plasmons resonance (LSPR) peak shifts to near infrared for a Fe2O3/Au-nanoparticle are similar to that of a Fe3O4/Au-nanoparticle having the same geometric parameters. Thirdly, the optical characteristics of the plasmonic nanoparticles were also studied. Finally, we hope that the developed numerical method can be extended to investigate the electromagnetic coupling within or between particles and its effect on the plasmonic behaviors. This makes the core/shell composite nanoparticles extremely interesting for magnetic, optical and biomedical applications.

Recently, localized surface plasmon resonances (SPRs) of metallic nanoparticles (NPs) have been widely used to construct plasmonic nanohybrids for heterogeneous photocatalysis. For example, the combination of plasmonic Au NPs and TiO2 provides pure TiO2 visible-light activity. The SPR effect induces an electric field and consequently enhances light scattering and absorption, favoring the transfer of photon energy to hot carriers for catalytic reactions. Numerous approaches have been dedicated to the improvement of SPR absorption in photocatalysts. Here, we have designed a core@shell-satellite nanohybrid catalyst whereby an Ag NP core, as a plasmonic resonator featuring unique dual functions of strong scattering and near-field enhancement, is encapsulated by SiO2 and TiO2 layers in sequence, with Au NPs on the outer surface, Ag@SiO2@TiO2-Au, for efficient plasmonic photocatalysis. By varying the size and number of Ag NP cores, the Au SPR can be tailored over the visible and near-infrared spectral region to reabsorb the scattered photons. In the presence of the Ag core, the incident light is efficiently confined in the reaction suspension by undergoing multiple scattering, thus leading to an increase of the optical path to the photocatalysis. Moreover, using numerical analysis and experimental verifications, we demonstrate that the Ag core also induces a strong near-field enhancement at the Au-TiO2 interface via SPR coupling with Au. Consequently, the activity of the TiO2-Au plasmonic photocatalyst is significantly enhanced, resulting in a high H2 production rate under visible light. Thus, the design of a single structural unit with strong scattering and field enhancement, induced by a plasmonic resonator, is a highly effective strategy to boost photocatalytic activity.

The extension of plasmonics to materials beyond the conventional noble metals opens up a novel and exciting regime after the inspiring discovery of characteristic localized surface plasmon resonances (LSPRs) in doped semiconductor nanocrystals originating from the collective oscillations of free holes in the valence band. We herein prepare colloidal monodisperse eccentric dual plasmonic noble metal-nonstoichiometric copper chalcogenide (Au@Cu2−xSe) hybrid hetero-nanostructures with precisely controlled semiconductor shell size and two tunable LSPRs in both visible (VIS) and near-infrared (NIR) regions associated with Au and Cu2−xSe, respectively. Through systematic evaluations of the photocatalytic performance of Au@Cu2−xSe upon sole NIR and dual VIS + NIR simultaneous excitations, we are capable of unambiguously elucidating the role of plasmonic coupling between two dissimilar building blocks on the accelerated photocatalytic reactions with greater rate constants from both experimental and computational perspectives. The significantly enhanced strength of the electromagnetic field arising from efficient plasmonic coupling under the excitation of two LSPRs results in the superior activities of dual plasmonic Au@Cu2−xSe in photocatalysis. The new physical and chemical insights gained from this work provide the keystone for the rational design and construction of high-quality dual- or even multi-plasmonic nano-systems with optimized properties for widespread applications ranging from photocatalysis to molecular spectroscopies.

Infrared phototransistors with very high performance show great potential in optoelectronic application, attributable to the intrinsic high transconductive gain of the transistor structure and therefore very large photo-responsivity. To distinguish multispectral information with phototransistors, however, the coincident spectral light has to been laterally dispersed and thereby coupled to the individual photo-gates sensing different target bands. Here, the dual-frequency plasmonic photo-coupler based on a single perforated metallic layer is numerically designed in the infrared region to improve photon absorption efficiency at two target wavelengths. The geometric parameters of the plasmonic grating composed of large and small cross-shaped holes are independently tuned to control the resonance frequencies under different incident (x- and y-) polarization conditions. While the dual-frequency resonant modes are induced by the hybridization between localized surface plasmons (LSPs) and propagating surface plasmons (PSPs), it is found that LSPs play the dominant role and can be effectively adjusted to achieve the target dual-frequency response. More importantly, the spectral response with low- (high-) frequency resonance corresponding to large (small) cross-hole region matches the spatially distributed photogates of the phototransistor structure and therefore realizes near-field enhancement and hence large photoresponsivity at target dual frequencies. In addition, the spectral response for x- and y-polarizations can be unified despite of the apparently broken symmetry between these two polarizations. Our work provides a general strategy to realize sensitive multiband-infrared phototransistors which require only state-of-the-art planar technology and are applicable for highly sensitive infrared photodetection.

Plasmonic composites consisting of silver nanostructures and zinc oxide semiconductor have better photocatalytic performance than pure zinc oxide. To prepare the composites, nanostructures of zinc oxide particles, gold spheres, and three different silver morphology including cubes, spheres, and wires were synthesized. A detailed study of the main mechanisms governing the activity of plasmonic photocatalysts showed that the improvement of photocatalytic performance is attributed to localized surface plasmon resonance-mediated energy transfer from silver to zinc oxide. This mechanism, which is performed using non-radiative (near-field) and radiation (far-field) processes, led to an increase in the concentration of e−/h+ pairs near the semiconductor. We also showed that the increase of the photocatalytic activity depends on the shape of the silver nanostructures in the composites. Our theoretical and experimental studies have shown that composites containing silver cubes have the highest increase of photocatalytic activity compared to other morphologies. The percentage of photocatalytic degradation of methylene blue solution in presence of silver cubes was about 15% higher than that of other morphologies. Therefore, by controlling the shape of noble metal nanostructures, the photocatalytic activity of a semiconductor can be maximized and adjusted.

Metal-oxides hold promise as superior plasmonic materials in the mid-infrared compared to metals, although their integration over established material technologies still remains challenging. We demonstrate localized surface plasmons in self-assembled, hemispherical CdZnO metal-oxide nanoparticles on GaAs, as a route to enhance the absorption in mid-infrared photodetectors. In this system, two localized surface plasmon modes are identified at 5.3 and 2.7 μm, which yield an enhancement of the light intensity in the underlying GaAs. In the case of the long-wavelength mode the enhancement is as large as 100 near the interface, and persists at depths down to 50 nm. We show numerically that both modes can be coupled to infrared intersubband transitions in GaAs-based multiple quantum wells, yielding an absorbed power gain as high as 5.5, and allowing light absorption at normal incidence. Experimentally, we demonstrate this coupling in a nanoparticle/multiple quantum well structure, where under p-polarization the intersubband absorption is enhanced by a factor of 2.5 and is still observed under s-polarization, forbidden by the usual absorption selection rules. Thus, the integration of CdZnO on GaAs can help improve the figures of merit of quantum well infrared photodetectors, concept that can be extended to other midinfrared detector technologies.

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.

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.

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.

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.

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.

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.

Within a mid-IR few-cycle laser, the generation of MHz isolated attosecond pulses via nanoplasmonic field enhancement in a structure that consisted of a metal coupled nanoparticle-disk, an insulator spacer, and a thin metal film is theoretically investigated. The interaction between the localized surface plasmons caused by the coupled nanodisks and the metal layer results in increased electric field. The resonance wavelengths of these two types of surface plasmons supported by the nanostructure are tailored by changing the coupled nanoparticle-disk size and the material type. Numerical calculations are used to optimize nanostructure and attain plasmonic field enhancement factors up to 86. The HHG process is studied by the time–frequency analysis. Our studies show that only short trajectories contribute to HHG and also, the chirp of these harmonics is very low. As a result, an isolated 40 as pulse without phase compensation is obtained directly by superposing the chirp-free high-order harmonics.

In this brief, we propose a novel wide-bandpass substrate integrated waveguide (SIW) filter in a compact circular cavity. It is implemented by etching spoof localized surface plasmon (SLSP) structure for more modes excitation. The dominant mode of SIW cavity and the seven modes of SLSP are employed to realize octuple-mode wideband filtering feature. Moreover, the two edges of the filter passband can be adjusted independently by changing the parameters of SIW or SLSP. Compared to traditional SIW wideband filters, the proposed structure dramatically increases the bandwidth meanwhile balances the size, complexity, and loss. A sample was fabricated and measured to validate the design. The measured results are in good agreement with the simulated ones, showing that a 3-dB relative bandwidth about 63% is achieved.

We prepared MoS2 monolayers on Au nanodot (ND) and nanohole (NH) arrays. Both these sample arrays exhibited enhanced photoluminescence intensity compared with that of a bare SiO2/Si substrate. The ...

Hollow metal nanostructures are fascinating because of their unique and surrounding environment-sensitive localized surface plasmon resonances (LSPRs). Herein, we have investigated the hollow silver nanoshell (HSN) sensitivity of different inner core radii and shell thicknesses with respect to change in surrounding medium refractive index. Also, we have shown that the extinction peak of HSNs can be fine-tuned in the visible region as well as biological windows by manipulating the size parameters. Moreover, an enhancement in refractive index sensitivity of 133 to 283 nm/RIU can be achieved in the biological windows by thick hollow silver nanoshells in comparison to thin ones. To achieve a comprehensive study, the sensitivity of homogeneous LSPR extinction inflection points with change in refractive index is also investigated. A consistent improvement in bulk refractive index sensitivity of 36% and 15% is predicted with thick and thin shell layers, respectively. Finally, thick HSNs showed higher refractive index sensitivity when compared with thin ones. Moreover, we envision the idea of more than one molecule detection by tracking the curvature changes. Therefore, we provide a deeper insight into the refractive index sensitivity of homogeneous LSPR inflection points for their use in LSPR-based sensors.

In this paper, we present a periodic nanostructure based on two types of silver plasmonic nanoantennas in order to enhance light absorption in graphene with a wavelength between 300 nm and 1800 nm. In this structure, a single graphene layer is located between two hexagonal boron nitride (hBN) layers, where this set is sandwiched between two layers of SiO2. The first nanoantenna type is a trapezoid inside SiO2, adjacent to the lower hBN, which focuses light within the graphene layer by intensifying the localized surface plasmons, triggering a significant increase in the absorption of the solar spectrum by graphene. The extent of this increase changes with varying bases of the trapezoid. The second nanoantenna type is in the same structure and contains two unequal trapezoids adjacent to each other. By adjusting the bases of these trapezoids, a relatively uniform broadband absorption spectrum is achieved which significantly enhances light absorption in the solar spectrum within 300–1800 nm, as compared to the first nanoantenna type. Both the first and second types of nanoantenna provide appropriate absorption at a communication window of 1550 nm as well as at 850 nm and 1300 nm, respectively.

Ultrafast laser irradiation can induce morphological and structural changes in plasmonic nanoparticles. Gold nanorods (Au NRs), in particular, can be welded together upon irradiation with femtosecond laser pulses, leading to dimers and trimers through the formation of necks between individual nanorods. We used electron tomography to determine the 3D (atomic) structure at such necks for representative welding geometries and to characterize the induced defects. The spatial distribution of localized surface plasmon modes for different welding configurations was assessed by electron energy loss spectroscopy. Additionally, we were able to directly compare the plasmon line width of single-crystalline and welded Au NRs with single defects at the same resonance energy, thus making a direct link between the structural and plasmonic properties. In this manner, we show that the occurrence of (single) defects results in significant plasmon broadening.

Interaction between light and plasmon oscillations in semiconductor nanocrystals has received significant attention in recent years driven, in part, by the possibility of coupling between plasmonic and semiconducting properties. Such coupling could lead to a variety of new applications in plasmonics, photonics, and optoelectronics. In this Concept we discuss the methods for generation of localized surface plasmon resonances in colloidal semiconductor nanocrystals and their unique magneto-optical properties. Different means of introducing free charge carriers, including aliovalent doping, non-stoichiometry, and external charging, are first compared and contrasted. The resulting plasmons can be manipulated using circularly polarized light and external magnetic field, allowing for the formation of the magnetoplasmon modes. The concept of using these magnetoplasmon modes as a new degree of freedom for controlling excitonic states and charge-carrier polarization is introduced and discussed. We also highlight some notable recent examples of controlling plasmon-exciton interactions and comment on their implications for future research in sustainable information technology.

In nanolithographic metallic gratings we investigate the dependence of photonic band gaps on geometrical parameters. Finite element modeling was used to develop a model for an optoelectronic device with periodicity of 470 nm and concomitantly the electronic response of a nanofabricated metal-semiconductor-metal photodetector grating was experimentally studied under a sweeping monochromatic light source. The grating spectral response increased in the region between 470 nm and 520 nm, corroborating the computational results. This increase is understood to occur because photons with wavelength shorter than approximately 520 nm are energetic enough to excite interband transitions in the Au, but the period of the structure acts as a cutoff where incident photons with wavelength shorter than the period are less likely to form surface plasmon polaritons. This cutoff originates from a photonic band gap. Magnetic field intensity profiles at the 3 dB cutoff indicate that a surface plasmon wave exists where each finger interacts with the next through overlapping magnetic fields, suggesting that the cutoff is a surface plasmon wave effect. Localized surface plasmon effects were observed at longer wavelengths in the modeled absorbance. The effects of three geometrical parameters on the spectral dependence of modeled absorbance were investigated.

A light delivery system based on localized surface plasmon (LSP) is the key component of heat-assisted magnetic recording (HAMR). We demonstrated a novel resonator–antenna system as the light delivery system for HAMR. We numerically analyzed the interaction mechanism between the resonator waveguide and the antenna. The localized enhanced resonated field of the resonator can improve the electric-field enhancement of the antenna. Based on the interaction mechanism, we proposed the ring resonator to achieve higher electric-field enhancement of light spots as the resonated field can be several times higher than input light under the resonance condition. The input laser energy can be recycled by limiting the energy in the ring waveguide without using higher power laser sources. Numerical results show that the nanofocusing performance in the ring resonator system would be much better than normal light systems. The maximum electric-field enhancement of light spots can be 124, and the absorption efficiency can be about 10% in the ring-lollipop system. The proposed resonator–antenna system can effectively increase the nanofocusing performance of the light delivery system for HAMR.

Three-dimensional (3D) plasmonic structures have attracted great attention because abnormal wetting behavior of plasmonic nanoparticles (NPs) on 3D nanostructure can enhance the localized surface plasmons (LSPs). However, previous 3D plasmonic nanostructures inherently had weak plasmonic light absorption, low electrical conductivity, and optical transmittance. Here, we fabricated a novel 3D plasmonic nanostructure composed of Ag NPs as the metal for strong LSPs and 3D nano-branched indium tin oxide (ITO BRs) as a transparent and conductive framework. The Ag NPs formed on the ITO BRs have a more dewetted behavior than those formed on the ITO films. We experimentally investigated the reasons for the dewetting behavior of Ag NPs concerning the geometry of ITO BRs. The spherical Ag NPs are spatially separated and have high density, thereby resulting in strong LSPs. Finite-domain time-difference simulation evidenced that spatially-separated, high-density and spherical Ag NPs formed on ITO BRs dramatically boost the localized electric field in the active layer of organic solar cells (OSCs). Photocurrent of PTB7:PCBM OSCs with the ITO BRs/Ag NPs increased by 14%.

Recently, plasmonic nanofluids (i.e., a suspension of plasmonic nanoparticles in a base fluid) have been widely employed in direct-absorption solar collectors because the localized surface plasmon supported by plasmonic nanoparticles can greatly improve the direct solar thermal conversion performance. Considering that the surface plasmon resonance frequency of metallic nanoparticles, such as gold, silver, and aluminum, is usually located in the ultraviolet to visible range, the absorption coefficient of a plasmonic nanofluid must be spectrally tuned for full utilization of the solar radiation in a broad spectrum. In the present study, a modern design process in the form of a genetic algorithm (GA) is applied to the tailoring of the spectral absorption coefficient of a plasmonic nanofluid. To do this, the major components of a conventional GA, such as the gene description, fitness function for the evaluation, crossover, and mutation function, are modified to be suitable for the inverse problem of tailoring the spectral absorption coefficient of a plasmonic nanofluid. By applying the customized GA, we obtained an optimal combination for a blended nanofluid with the desired spectral distribution of the absorption coefficient, specifically a uniform distribution, solar-spectrum-like distribution, and a step-function-like distribution. The resulting absorption coefficient of the designed plasmonic nanofluid is in good agreement with the prescribed spectral distribution within about 10\% to 20\% of error when six types of nanoparticles are blended. Finally, we also investigate how the inhomogeneous broadening effect caused by the fabrication uncertainty of the nanoparticles changes their optimal combination., 4 figures

In this article, we present a theoretical study on localized surface Plasmon of spherical Ag nanoparticles (NPs) done by numerical simulation. A plane EM wave was used to determine absorption cross-section and results showed that excitation of LSPPs produced an electric field on the surface of the nanoparticle. This field causes a large cross sectional area that influences higher scattering of incident photon at the surface of an absorber layer. It was concluded that LSPPs excitations in small size spherical particles can be utilized in low-cost solar cells to increase PCE of solar panels and can be expanded to many other fields of optoelectronic technologies ranging from solar cells, through photo diodes to optical bio-sensing applications.

Recently, localized surface plasmon resonance of noble metal nanoparticles has been widely used to broaden the photoresponse of wide-band-gap semiconductors. In this work, Au nanoparticles with different sputtering time were prepared via ion sputtering and thermal treatment on ZnO thin films prepared by magnetron sputtering. The influence of the Au nanoparticle sputtering time on the absorbance of the Au/ZnO nanocomposite was investigated. The results show that Au/ZnO nanocomposites have enhanced UV absorption and broad absorption bands around 580–600 nm compared with ZnO without Au nanoparticles, which are attributed to the band-to-band excitation of ZnO and localized surface plasmon resonance of gold nanoparticles. Under the illumination of UV light, electrons are excited from the valence band to conduction band of ZnO, while hot electrons are transferred from Au nanoparticles with smaller particle size to ZnO, resulting in the generation of photocurrent. Under the illumination of visible light, only hot electrons are transferred from Au nanoparticles with larger particle size to ZnO, leading to the generation of photocurrent. Then the influence of sputtering time on the dark current and IXenon lamp/IDark of the photodetectors was investigated. The results show that Au nanoparticles are able to decrease the dark current of photodetectors and influence the photoresponse under visible light illumination.

Recently, studies have been carried out on attempts to combine surface-enhanced Surface-enhanced Raman spectroscopy (SERS) substrates that can be based on either localized surface plasmon (LSP) or surface plasmon polaritons (SPP) structures. By combining these two systems, the drawbacks of each other can be solved. However, the manufacturing methods involved so far are sophisticated, labor-intensive, expensive, and also technically demanding. We propose a facile method for the fabrication of a flexible plasmonic nanoslit SERS sensor. We utilized the pattern on periodic optical disks (DVD-R) as a cheap substitute for printing the periodic pattern on PDMS with soft imprint lithography. Ag nanoslit (AgNS) was fabricated by serial bideposition using a dynamic oblique angle deposition (DOD) technique. The nanoslit structures were physically and optically characterized, and the experimental results were compared to the numerical simulation studies; Monte Carlo and the finite-difference time-domain (FDTD) simulation. The Ag nanoslit structure showed an excellent SERS enhancement, and its biosensing capability was demonstrated by the sensing of bilirubin.

The electron transfer mechanism of noble materials to semiconductor was enhanced for the first time by localized surface plasmon resonances (LSPRs) using in situ irradiated X-ray photoelectron spec...

Heavily doped metal oxide nanocrystals (NCs) possess tunable infrared localized surface plasmon resonances (LSPRs) that give them utility for several potential applications, including photothermal ...

This article presents the architecture of optical microring resonator based on surface plasmon polaritons using different profile materials like silicon (Si), silver (Ag) and gold (Au). It is observed that 3.53e-005 w/m, 6.92e-005 w/m, 7.05e-005 w/m received optical powers are achieved in silicon (Si), silver (Ag) and gold (Au) profile materials, respectively, of optical microring resonator at 0.1 w/m minimum input transmission power for 1.55 μm input transmission wavelength. The result shows that the silicon profile is best for designing the optical microring resonator in terms of received optical power.

Plasmonic color generation has attracted much research interest because of the unique optical properties of plasmonic nanocrystals that are promising for chromatic applications, such as flat-panel displays, smart windows, and wearable devices. Low-cost, monodisperse plasmonic nanocrystals supporting strong localized surface plasmon resonances are favorable for the generation of plasmonic colors. However, many implementations so far have either a single static state or complexities in the particle alignment and switching mechanism for generating multiple displaying states. Herein, we report on a facile and robust approach for realizing the electrochemical switching of plasmonic colors out of colloidal plasmonic nanocrystals. The metal nanocrystals are coated with a layer of polyaniline, whose refractive index and optical absorption are reversibly switched through the variation of an applied electrochemical potential. The change in refractive index and optical absorption results in the modulation of the plasmonic scattering intensity with a depth of 11 dB. The electrochemical switching process is fast (∼5 ms) and stable (over 1000 switching cycles). A device configuration is further demonstrated for switching plasmonic color patterns in a transparent electrochemical device, which is made from indium tin oxide electrodes and a polyvinyl alcohol solid electrolyte. Our control of plasmonic colors provides a favorable platform for engineering low-cost and high-performance miniaturized optical devices.

Localized surface plasmon resonances optically excited in metallic nanoparticles (NPs) produce beneficial thermal and nonthermal effects. Nonthermal effects, such as enhancing and localizing fields...

Recently, metal surface plasma technology has been widely used to improve the quantum efficiency of optoelectronic devices, such as ZnO light-emitting diodes (LEDs). In this work, Ag films with the appropriate thickness were prepared by evaporation and annealed, and a layer of ZnCdO films with different Cd concentrations was grown on the Ag films by the pulsed laser deposition method. During this process, the changes in the Cd concentrations caused the near-band edge (NBE) emission of the ZnCdO films to be continuously adjusted in the ultraviolet to green wavelength range by controlling the oxygen pressure. The prepared Ag nanoparticles and ZnCdO composite films were used to study the metal localized surface plasmon (LSP) effect. The results show that the enhanced or reduced photoluminescence intensity of ZnCdO NBE depends on the probability of electrons transport to either the LSP level or the Fermi level of the metal. This discovery provides an important theoretical basis for the preparation of ZnCdO semiconductor LEDs in the future.

Synthesis of anisotropic Ag nanoprisms (AgPRs) contributes to the development of high performance plasmonic devices. The localized surface plasmon resonance wavelength of AgPRs was successfully tun...

We propose a plasmon induced tunable metasurface for multiband superabsorption and terahertz sensing. It consists of a graphene sheet that facilitates perfect absorption where the graphene pattern at the top layer creates an enhanced evanescent wave that facilitates the metasurface to work as a sensor. The modelling and numerical analysis are carried out using Finite Element Method (FEM) based software, CST microwave studio where a genetic algorithm (GA) is used to optimize the geometric parameters, and metasurface tunability is achieved via an external gate voltage on the graphene. By exploiting graphene’s tunable properties we demonstrate a multiband superabsorption spectra having a maximum absorption of 99.7% in a frequency range of 0.1–2.0 THz that also maintain unique optical performance over a wide incidence angle. Further results show how the superabsorber can be used as a sensor, where the resonance frequency shifts with the refractive index of the surrounding environment.

A central theme of nanocrystal (NC) research involves synthesis of dimension-controlled NCs and studyof size-dependent scaling laws governing their optical, electrical, magnetic, and thermodynamic properties. Here, we describe the synthesis of monodisperse CdO NCs that exhibit high quality-factor (up to 5.5) mid-infrared (MIR) localized surface plasmon resonances (LSPR) and elucidate the inverse scaling relationship between carrier concentration and NC size. The LSPR wavelength is readily tunable between 2.4 and ∼6.0 μm by controlling the size of CdO NCs. Structural and spectroscopic characterization provide strong evidence that free electrons primarily originate from self-doping due to NC surface-induced nonstoichiometry. The ability to probe and to control NC stoichiometry and intrinsic defects will pave the way toward predictive synthesis of doped NCs with desirable LSPR characteristics.

Mesoporous silica features open and accessible pores that can intake substances from the outside. The combination of mesoporous silica with plasmonic nanostructures represents an interesting platform for an optical sensor based on the dependence of plasmonic modes on the refractive index of the medium in which metallic nanoparticles are embedded. However, so far only a limited number of plasmonic nanostructures are combined with mesoporous silica, including random dispersion of metallic nanoparticles and flat metallic thin films. In this study, we make a mesoporous silica layer on an aluminum nanocylinder array. Such plasmonic arrangements support both localized surface plasmon resonances (LSPRs) and extended modes which are the result of the hybridization of LSPRs and photonic modes extending into the mesoporous layer. We investigate in situ optical reflectance of this system under controlled pressure of isopropanol vapor. Upon exposure, the capillary condensation in the mesopores results in a gradual spectral shift of the reflectance. Our analysis demonstrates that such shifts depend largely on the nature of the modes; that is, the extended modes show larger shifts compared to localized ones. Our materials represent a useful platform for the field of environmental sensing

We developed a convenient, facile, low cost and ‘‘green” method to synthesize nanoparticles (NPs) with deep-ultraviolet localized surface plasmon resonances (LSPR) based on laser ablation of aluminum target in liquid. The nanoparticles had an Al-Al2O3@C core-shell structure, and the LSPR peak ranged from 240nm to 250nm with the increasing of laser radiation time. It is found that the LSPR peak of the NPs is related to the presence of Al2O3 based on experimental characterization and theoretical simulation. The carbon shell can reduce the oxidation of Al nanoparticles and enhance the stability, which is significant important to achieve the deep-ultraviolet LSPR. Moreover, we demonstrated the enhancement of the blue fluorescence intensity from CsPbBr3-xClx by the Al-Al2O3@C NPs, due to the stronger excitations for CsPbBr3-xClx by the enhancement of localized electromagnetic field from LSPR.

Visualization of surface plasmon polariton (SPP) propagation at dielectric/metal interfaces is indispensable in providing opportunities for the precise designing and controlling of the functionalities of future plasmonic nanodevices. Here, we report the visualization of SPPs propagating along the buried organic/metal interface of fullerene (C60)/Au(111), through dual-colored two-photon photoemission electron microscopy (2P-PEEM) which precisely visualizes the SPP propagation of plasmonic metal nanostructures. Although SPPs excited by near-infrared photons at the few monolayer C60/Au(111) interface are clearly visualized as interference beat patterns between the SPPs and incident light, faithfully reflecting SPP properties modulated by the overlayer, photoemission signals are suppressed for thicker C60 films, due to less valence electrons participating in 2P-photoemission processes. With the use of silver (Agn (n = 21 and 55)) nanoclusters, which exhibit enhancement of overall photoemission intensities due to localized surface plasmons functioning as SPP sensitizers, it is revealed that the 2P-PEEM is applicable to the imaging of SPPs for thick C60/Au(111) interfaces, where SPP properties are hardly modulated by the added small amount (∼0.1 monolayer) of Agn sensitizers.

Anisotropic gold nanostructures are attracting attention due to the strong correlation between their shape and the localized surface plasmon resonances, which allows tuning their optical responses ...