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We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 16.4 Ω/sq, while the reference ITO TCE exhibited a transmittance of 76.4% and a sheet resistance of 18.7 Ω/sq. Despite the 8.9% lower optical transmittance, the UVLEDs fabricated with HFTCEs achieved a 25% increase in output efficiency compared to reference UVLEDs. This improvement is attributed to the HFTCE's twofold longer current spreading length under operating forward voltages, and more significantly, the enhanced out-coupling of localized surface plasmon (LSP) resonance with the trapped wave-guided light modes. [ABSTRACT FROM AUTHOR]

A plasmonic nanosensor is proposed and investigated its sensitivity using the optical properties of plasmonic nanoparticles. To this end, we first consider the nanosensor consisting of bowtie nanoparticles. Then, the nanosensor performance is examined under different factors such as the refractive index of the background environment, the height, and length of the nanoparticles. The proposed bowtie nanoparticles, in this work, are made of gold. The boundary element method is used to simulate the nanosensor. The extinction cross-section is computed in terms of wavelength and the effect of various factors on the resonance wavelength of localized surface plasmon is investigated. It is shown that the nanosensor investigated in this research has a high sensitivity to the changes in the refractive index of the studied sample. The sensitivity of the nanosensor is obtained as 650 nm/RIIU. In addition, the required spectral range can be arbitrarily adjusted by the type of nanoparticles. [ABSTRACT FROM AUTHOR]

Position-sensitive detector (PSD) is an essential noncontact optical position sensor based on the lateral photovoltaic effect (LPE), which plays a vital role in various applications. However, limited by the absorption of substrate and rapid recombination of carriers, it remains challenging to develop superior-performance PSDs. Here, we use Ag nanoparticles (NPs) to boost the light-harvesting efficiency and ZnO nanowires (NWs) to capture hot electrons and observe the plasmon-enhanced LPE in this structure. Without any applied bias voltage, it shows an excellent position sensitivity in a broad-band range of 405–980 nm with a maximum sensitivity of 252.6 mV/mm, which is about six times larger than that in the ZnO NWs/Si (42.8 mV/mm) structure. Besides, the LPE response is strongly dependent on the ZnO NW growth time and Ag NP concentration. We elaborated the underlying mechanism by analyzing hot electron generation and injection and the diffusion of charge carriers under nonuniform light illumination. The excellent position sensitivity performance can be attributed to the efficient transport of hot electrons in the conductive network of the ZnO NW film. Our findings further establish the potential of Ag-decorated ZnO NWs for noncontact photoelectric sensing and provide insights into developing high-sensitivity, low-cost, and self-powered PSDs. [ABSTRACT FROM AUTHOR]

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future. [ABSTRACT FROM AUTHOR]

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Ultrafast nanophotonics is a rapidly growing area of study focused on creating nanodevices that can modulate the properties of light at, to this date, unparalleled speed. To facilitate the growth of this field, there is a growing need for compact metamaterial designs for the manipulation of the amplitude, phase, and polarization of light. One promising strategy involves leveraging the optical nonlinearity of nanostructured materials to alter their permittivity by interacting with high‐intensity ultrashort laser pulses. This study showcases how such requirements can be met through the utilization of 2D materials, particularly graphene. The nonlinear optical response of a graphene nanorectangle array is theoretically modeled to achieve all‐optical, fully reversible, broadband, and ultrafast dynamic control of light chirality. This is achieved by taking advantage of the energy relaxation dynamics of coherently excited localized plasmons supported by the metasurface, and the transient increase in electron temperature in graphene. Using finite‐difference time‐domain simulations, ultrafast dynamic tuning between circular and linearly polarized light is demonstrated. The proposed platform gives promise for ultrathin, CMOS‐compatible nanophotonic systems that can provide high‐speed, room‐temperature modulation of light polarization. [ABSTRACT FROM AUTHOR]

Structured illumination microscopy (SIM), an advanced super-resolution methodology, transcends the traditional diffraction limit inherent in optical imaging. This technique utilizes standing-wave illumination generated through the interplay of two obliquely incident light waves. The intrinsic resolution constraint of SIM, traditionally pegged at half the wavelength because of the standing wave's periodicity, has the potential for enhancement by integrating high spatial frequency illumination patterns, particularly when sourced in the near-field of plasmonic nanostructures. The present study introduces and computationally validates a novel, easily fabricated substrate composed of self-assembled gold nanoparticles designed explicitly for generating these high spatial frequency patterns. Addressing the necessity for diverse patterns in reconstructing super-resolution imagery within plasmonic SIM, this research conducted extensive numerical simulations of nanoparticle arrays under varying illumination scenarios. This undertaking affirmed the feasibility of manipulating high-frequency patterns. Super-resolution reconstruction was actualized by applying Blind-SIM techniques, which verified its effectiveness. This innovative approach notably achieved a resolution threshold of 60 nm, markedly exceeding the conventional 150 nm diffraction barrier and surpassing the 75 nm resolution typically observed in standard SIM applications. Highlights: Use a self-assembled nanoparticle plasmonic substrate as structured illumination. Numerical demonstration of super-resolution imaging. Considerable improvement in resolution threshold, exceeding standard SIM. [ABSTRACT FROM AUTHOR]

We investigated hybrid functional transparent conductive electrodes (HFTCEs) composed of indium-tin-oxide (ITO) and silver nanowires (AgNWs) for the enhancement of output efficiency in GaN-based ultraviolet light-emitting diodes (UVLEDs). The HFTCEs demonstrated an optical transmittance of 69.5% at a wavelength of 380 nm and a sheet resistance of 16.4 Ω/sq, while the reference ITO TCE exhibited a transmittance of 76.4% and a sheet resistance of 18.7 Ω/sq. Despite the 8.9% lower optical transmittance, the UVLEDs fabricated with HFTCEs achieved a 25% increase in output efficiency compared to reference UVLEDs. This improvement is attributed to the HFTCE’s twofold longer current spreading length under operating forward voltages, and more significantly, the enhanced out-coupling of localized surface plasmon (LSP) resonance with the trapped wave-guided light modes.

The potential applications of nanoparticles in future technologies are extensive. Many of those applications require assembly of monodispersed nanostructures into ordered macroscopic building blocks, such as arrays, to enable their integration into complex devices. Examples of such applications include electrical contacts to nanoparticles in electro-optical devices and nanogap-enabled chemical sensors. Herein, we present a versatile approach to fabricate extended and highly ordered arrays of fully alloyed Ag/Au nanoparticles on solid substrates that can be easily expanded to other binary and even higher alloys. The strategy is demonstrated by fabricating Ag/Au alloys with Ag compositions ranging from 0% to 100%. As expected, the plasmon resonance of the alloyed nanoparticles could be varied between those of pristine Au and Ag. The width of the plasmon resonance was significantly smaller compared to those of partially low-temperature alloyed mixtures presented previously. Finally, a Cu2O semiconductor shell was grown on the alloy core to demonstrate that the resulting nanoparticle surfaces are accessible for functionalization, therefore broadening the potential applications of the material. [ABSTRACT FROM AUTHOR]

To investigate nanosensors based on localized surface plasmon, a structure consisting of a conical nanoshell has been considered and the factors affecting its performance has been studied. The factors are the refractive index of the background environment, dimensions, and the nanoshell material. A nanosensor consisting of an Au@Cu2−xS nanoshell with a Cu2−xS semiconductor shell and a gold core has been proposed and its sensitivity has been investigated. The sensitivity of this Cu2−xS nanoshell reaches 1505 nm RIU , which is more than bimetallic nanoshells. Using the boundary element method and calculating the extinction cross-section in terms of wavelength, the dependence of the resonance wavelength of the localized surface plasmon on different parameters has been investigated. It is shown that the nanosensor investigated in this research has a high sensitivity to the changes in the refractive index of the studied sample. In addition, the required spectral range can be arbitrarily adjusted by the type of nanoparticles. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman spectroscopy (TERS) has recently been developed to push the spatial resolution down to single-chemical-bond scale. The morphology of the scanning tip, especially the atomistic protrusion at the tip apex, plays an essential role in obtaining both high spatial resolution and large field enhancement at the Ångström level. Although it is very difficult to directly characterize the atomistic structures of the tip, the Raman scattering from the apex’s own vibrations of the metal tip can provide valuable information about the stacking of atoms at the tip apex. However, conventional quantum chemistry packages can only simulate the Raman scattering of small metal clusters with few atoms due to huge computational cost, which is not enough since the shaft of the tip behind the apex also makes significant contributions to the polarizabilities of the whole tip. Here we propose an atomistic polarization model to simulate the Raman spectra of large metal tips at subwavelength scales based on the combination of the atomistic discrete dipole approximation model and the density functional theory. The atomistic tip with different sizes and stacking structures is considered in its entirety during the calculation of polarizabilities, and only the vibrational contributions from the tip apex are taken into account to simulate the Raman spectra of the tip. The Raman spectral features are found to be very sensitive to the local constituent element at the tip apex, atomic stacking modes, and shape of the tip apex, which can thus be used as a fingerprint to identify different atomistic structures of the tip apex. Moreover, our approaches can be extended to the metal tips with sub-wavelength sizes, making it possible to consider both the large scale and the atomistic detail of the tip simultaneously. The method presented here can be used as a basic tool to simulate the Raman scattering process of the metal tips and other nanostructures in an economic way, which is beneficial for understanding the roles of atomistic structures in tip- and surface-enhanced spectroscopies.

As the driving source, highly efficient silicon-based light emission is urgently needed for the realization of optoelectronic integrated chips. Here, we report that enhanced green electroluminescence (EL) can be obtained from oxygen-doped silicon nitride (SiNx:O) films based on an ordered and tunable Ag nanocavity array with a high density by nanosphere lithography and laser irradiation. Compared with that of a pure SiNxO device, the green electroluminescence (EL) from the SiNx:O/Ag nanocavity array device can be increased by 7.1-fold. Moreover, the external quantum efficiency of the green electroluminescence (EL) is enhanced 3-fold for SiNx:O/Ag nanocavity arrays with diameters of 300 nm. The analysis of absorption spectra and the FDTD calculation reveal that the localized surface plasmon (LSP) resonance of size-controllable Ag nanocavity arrays and SiNx:O films play a key role in the strong green EL. Our discovery demonstrates that SiNx:O films coupled with tunable Ag nanocavity arrays are promising for silicon-based light-emitting diode devices of the AI period in the future.

Electron energy loss spectroscopy (EELS) is often utilized to characterize localized surface plasmon modes supported by plasmonic antennas. However, the spectral resolution of this technique is only mediocre, and it can be rather difficult to resolve modes close in the energy, such as coupled modes of dimer antennas. Here, we address this issue for a case study of the dimer plasmonic antenna composed of two gold discs. We analyze four nearly degenerate coupled plasmon modes of the dimer: longitudinal and transverse bonding and antibonding dipole modes. With a traditional approach, which takes into account the spectral response of the antennas recorded at specific points, the modes cannot be experimentally identified with EELS. Therefore, we employ the spectral and spatial sensitivity of EELS simultaneously. We propose several metrics that can be utilized to resolve the modes. First, we utilize electrodynamic simulations to verify that the metrics indeed represent the spectral positions of the plasmon modes. Next, we apply the metrics to experimental data, demonstrating their ability to resolve three of the above-mentioned modes (with transverse bonding and antibonding modes still unresolved), identify them unequivocally, and determine their energies. In this respect, the spatio-spectral metrics increase the information extracted from electron energy loss spectroscopy applied to plasmonic antennas.

Due to the increasing importance of nanosensors in the early diagnosis of diseases, the need for high-performance nanosensors is one of the goals of researchers. In this paper, a structure consisting of plasmonic nanoshells with spherical and ellipsoidal geometry has been proposed to calculate the refractive index (RI) changes in the range of 1–3. The sensitivity of the proposed nanosensor has been computed, and the effective factors on the performance of the nanosensor, including geometry, material, core dimensions, shell thickness, and RI of the surrounding environment are studied. To this end, various nanostructures have been modeled using the boundary element method. It has been shown that ellipsoidal nanoshells are more sensitive to RI changes than spherical nanoshells. Also, the results show that nanoshells with a core and shell made of plasmonic metals (bimetallic nanoshell) can exponentially increase the sensitivity of the nanosensor. [ABSTRACT FROM AUTHOR]

Circular dichroism (CD) effects have broad applications in fields including biophysical analysis, analytical chemistry, nanoscale imaging, and nanosensor design. Herein, a novel design of a tilted F-type chiral metal nanostructure composed of circular nanoholes with varying radii has been proposed to achieve remarkable CD effects, and the results demonstrate the generation of a significant current oscillation at the sharp edges where the nanoholes overlap under circularly polarized light, resulting in a strong CD effect. The CD effect can reach up to 7.5%. Furthermore, spectral modulation of the resonant wavelength can be achieved by adjusting the structural parameters, which enhances the tunability of the structure. Overall, these results provide theoretical or practical guidance for enhancing the circular dichroism signal strength of chiral metal nanostructures and designing new types of two-dimensional chiral structures. [ABSTRACT FROM AUTHOR]

Localized surface plasmon polaritons can confine the optical field to a single-nanometer-scale area, strongly enhancing the interaction between photons and molecules. Theoretically, the ultimate enhancement might be achieved by reducing the “photon size” to the molecular extinction cross-section. In addition, desired control of electronic transitions in molecules can be realized if the “photon shape” can be manipulated on a single-nanometer scale. By matching the photon shape with that of the molecular electron wavefunction, optically forbidden transitions can be induced efficiently and selectively, enabling various unconventional photoreactions. Here, we demonstrate the possibility of forming single-nanometer-scale, highly intense fields of optical vortices using designed plasmonic nanostructures. The orbital and spin angular momenta provided by a Laguerre–Gaussian beam are selectively transferred to the localized plasmons of a metal multimer structure and then confined into a nanogap. This plasmonic nano-vortex field is expected to fit the molecular electron orbital shape and spin with the corresponding angular momenta.

Surface Plasmonic Resonance (SPR) induced by metallic nanoparticles can be exploited to enhance the response of photodetectors (PD) to a large degree. Since the interface between metallic nanoparticles and semiconductors plays an important role in SPR, the magnitude of the enhancement is highly dependent on the morphology and roughness of the surface where the nanoparticles are distributed. In this work, we used mechanical polishing to produce different surface roughnesses for the ZnO film. Then, we exploited sputtering to fabricate Al nanoparticles on the ZnO film. The size and spacing of the Al nanoparticles were adjusted by sputtering power and time. Finally, we made a comparison among the PD with surface processing only, the Al-nanoparticles-enhanced PD, and the Al-nanoparticles-enhanced PD with surface processing. The results showed that increasing the surface roughness could enhance the photo response due to the augmentation of light scattering. More interestingly, the SPR induced by the Al nanoparticles could be strengthened by increasing the roughness. The responsivity could be enlarged by three orders of magnitude after we introduced surface roughness to boost the SPR. This work revealed the mechanism behind how surface roughness influences SPR enhancement. This provides new means for improving the photo responses of SPR-enhanced photodetectors. [ABSTRACT FROM AUTHOR]

In this article, we propose a simple method to calculate electrical permittivity and refractive index of surface agents of gold nanoparticles (Au NPs), in which it is possible to find the refractive index of surface agents shell by using the absorption peak of the gold nano-colloid. One of the usual tests for detection of surface agents is colorimetric methods based on the change of color of Au NPs. The color change is mainly due to the shift of localized surface plasmon resonance which is related to electrical interactions of surface agents. Although there are many mathematical models for simulating the absorption spectrum and calculating the plasmonic peak, using them is not simple and possible for everyone due to the need for programming. Here, the necessary simulations have been performed for different values ​​of refractive index of surface agents and particle size, and absorption peaks have been obtained. Using numerical methods, a simple formula is obtained between the wavelength of plasmonic peak, the ratio of hydrodynamic diameter to Feret size of the particles, and the refractive index of the surface agents. This method can help researchers to obtain the refractive index and consequently the type or concentration of surface agents around Au NPs without the need for programming or complex mathematical operations. It can also open new horizons in analyzing colorimetric diagnosis of biological agents such as viral antibodies, antigens, and other biological agents. [ABSTRACT FROM AUTHOR]

Surface-Enhanced Raman Spectroscopy is a powerful technique that boosts the distinctive fingerprint signals of molecules, making them more accessible for analysis. It utilizes metallic nanoparticles, acting as amplifiers, to greatly enhance the signals emitted by the molecules. This study aimed to explore the SERS potential of gold nanoparticles (AuNPs) with different geometries using a non-resonant molecule, 4-MBA. Nanospheres (14±2 nm), nanorods (11±2 nm x 50±7 nm) and nanostars (38±4 nm) were synthesized via the HAuCl4 reduction method. All three AuNP geometries exhibited a remarkable enhancement of the Raman signal of 4-MBA by a magnitude of 104. Notably, only gold nanorods and nanostars displayed localized surface plasmon within the biological window, making them highly suitable for biological sample analysis. Meanwhile, the application of gold nanospheres should be limited to chemical SERS detection. These findings confirm the potential use of these nanostructures as SERS substrates for studying molecules with low molar...

Using finite element calculations, we investigated the near field properties of two types of commonly used metal nanostructures (a tip-substrate model representing a scanning tunneling microscope type setup (TS) and a nanoparticle-on-mirror (NPoM) configuration) with atomic sharpness and extreme focusing capabilities. The spatial confinement and electric field enhancement of the local field as well as the fluorescence quantum efficiency of a model molecule (as represented by an oscillating dipole) in the cavity region of the two models were systematically studied. It was found that the TS model tends to support higher local electric field enhancement while the NPoM model can provide a more localized plasmon electric field near the nanoparticle. Calculations with the radiating model molecule indicate that both TS and NPoM can cause significant enhancements to the non-radiative decay rates at the order of 106 in the wavelength range of 500–1000 nm. The TS model shows better performance for the radiative enhancements and the resulting emission quantum yield. These results are not only helpful to improve the understanding of such important nanocavities but also supply a reference for their further applications in different areas.

We report on a self-referenced refractive index optical sensor based on Au nanoislands. The device consists of a random distribution of Au nanoislands formed by dewetting on a planar SiO2/metal Fabry–Pérot cavity. Experimental and theoretical studies of the reflectance of this configuration reveal that its spectral response results from a combination of two resonances: a localized surface plasmon resonance (LSPR) associated to the Au nanoislands and the lowest-order anti-symmetric resonance of the Fabry–Pérot cavity. When the device is immersed in different fluids, the LSPR contribution provides high sensitivity to refractive index variations of the fluid, whereas those refractive index changes have little impact on the Fabry–Pérot resonance wavelength, allowing its use as a reference signal. The self-referenced sensor exhibits a spectral sensitivity of 212 nm/RIU (RIU: refractive index unit), which is larger than those of similar structures, and an intensity sensitivity of 4.9 RIU−1. The proposed chip-based architecture and the low cost and simplicity of the Au nanoisland synthesis procedure make the demonstrated sensor a promising self-referenced plasmonic sensor for compact biosensing optical platforms based on reflection mode operation. [ABSTRACT FROM AUTHOR]

NH- ÎĽ LED, namely a micro light-emitting diode structure with nano-holes dug all the way through the active region, is designed to make silver nanoparticles in extremely close contact with the quantum wells for improving the coupling between the localized surface plasmon and the quantum wells (LSP-QWs coupling) and thus enhancing the optical properties of the ÎĽ LED. The experimental results show that, thanks to this deep nanohole structure, the LSP-QWs coupling can be realized effectively, which ultimately increases the optical performance of the ÎĽ LED. The internal quantum efficiency of the NH- ÎĽ LED filled with silver nanoparticles is increased by 12%, and the final optical output power is also enhanced. We have further carried out a comparison study which measures the transient lifetime of two different types of ÎĽ LEDs, and the results provide convincing evidence for the existence of the ultra close range LSP-QWs coupling effect. [ABSTRACT FROM AUTHOR]

Herein, we attempt to study the synthesis process of 3-mercaptopropionic acid (3-MPA) capped gold nanoparticles (Au-MPA) and to optimize the preparation of colorimetric sensor based on the localized surface plasmon (LSP) phenomenon compared to the citrate stabilized gold nanoparticles (Au-Citrate). Both Au-Citrate and Au-MPA were prepared using the reduction method. In our case, the product of Au-MPA shows red-wine color of solution with a plasmonic peak at 527 nm, while Au-Citrate has a plasmonic peak at 519 nm with the same color of the solution. Both particles have a spherical shape as validated by the TEM image with the average size of Au-Citrate and Au-MPA being 34 nm and 51 nm, respectively. Different peak values can be explained by the different size distributions and modified local refractive indices due to the adsorbed ligand on the metal surfaces. Vibrational frequency characterization shows shifting and broadening especially in the region of CO stretching as the result of carboxyl group interaction. Functionalization of AuNPs by the use of biocytin (Biotinylated-AuNPs) shows good stability as revealed with no significant change in the absorbance spectra compared to the AuNP capped by citrate or 3-MPA. The addition of various concentrations of avidin into the assay results in the color changes and the red-shift of the absorbance spectra due to the cross-link aggregation with an intermediate value in the sensing characteristic. This research provides preliminary studies for colorimetric colloidal sensor performances tunability by modifying the adsorbed ligand as the linker between the metal and the bioreceptor. [ABSTRACT FROM AUTHOR]

A localized surface plasmon (LSP) coupling nanorod $\mu $ LED using graphene as a transparent conductive electrode structure was demonstrated. The optical performance of the $\mu $ LED with LSP coupling is enhanced by about 36% in external quantum efficiency and 84% in photoluminescence measurements as compared with the LSP-free sample. This LSP coupling enhancement relies on the very large sidewall area provided by the nanorod structure and the zero distance contact between the nanoparticles and nanorods. This work provides a broad prospect for the application of LSP in the $\mu $ LED field. [ABSTRACT FROM AUTHOR]

The strong coherent coupling in different electromagnetic modes can control the light-matter interaction more conveniently. Here, we theoretically researched the hybridization between the borophene surface plasmon (BSP) mode and the borophene localized surface plasmon (BLSP) mode in borophene grating structure. This coupling effect leads to the emergence of multiple hybrid modes. The absorption spectra of the system are investigated through finite difference time domain (FDTD) simulation and coupled oscillator model (COM). Results show that the coherent coupling of BSP and BLSP can be achieved by adjusting the carrier density of the borophene gratings. A Rabi splitting effect with frequency of 21.6 THz can be observed. Furthermore, we investigated the effects of geometric structural parameters, incident angle, and relaxation time on the correlated coupling spectra. Our work may deepen the understanding of light–matter interactions and provide a reference for borophene-based active photonic devices in the near-infrared region. • The absorption properties and field distribution are simulated by finite difference time domain method. • The results of the COM theory are consistent with the FDTD simulation. • A Rabi splitting phenomenon with a high frequency of 21.6 THz can be observed. • The coherent coupling of BSP and BLSP can be achieved by adjusting the carrier density of the borophene gratings. • Provide a reference for borophene-based active photonic devices in the near-infrared region. [ABSTRACT FROM AUTHOR]

Circular dichroism (CD) effects have broad applications in fields including biophysical analysis, analytical chemistry, nanoscale imaging, and nanosensor design. Herein, a novel design of a tilted F-type chiral metal nanostructure composed of circular nanoholes with varying radii has been proposed to achieve remarkable CD effects, and the results demonstrate the generation of a significant current oscillation at the sharp edges where the nanoholes overlap under circularly polarized light, resulting in a strong CD effect. The CD effect can reach up to 7.5%. Furthermore, spectral modulation of the resonant wavelength can be achieved by adjusting the structural parameters, which enhances the tunability of the structure. Overall, these results provide theoretical or practical guidance for enhancing the circular dichroism signal strength of chiral metal nanostructures and designing new types of two-dimensional chiral structures.

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%.

Abstract 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.

Plasmonic phenomena on the surface between metal and dielectric have received extensive attention, and have boosted a series of exciting techniques. Plasmonics describes the interaction between light and electronics and shows great potential in nanophotonics, optoelectronic devices, quantum physics, and surface-enhanced spectroscopy, etc. However, plasmonic phenomena are always suffering from the inherent loss issue of plasmonic materials at optical frequency, which has restricted further applications of plasmonics. In this review, we focus on the technique of waveguide effective plasmonics, which is a feasible low-loss realization of plasmonic metamaterials in lower frequency based on the structural dispersion. This review provides the underlying physics of the waveguide effective plasmonics and its applications varying from classical plasmonic concepts to novel effective plasmonic devices. Finally, we make a brief discussion on the direction of future researches and a prospect of the potential applications.

Microspectrometer features remarkable portability and integration and is prospected to provide quick detection tools to daily life and revolutionize research techniques. Due to the extremely finite footprint, microspectrometer can hardly analyze the polarization feature by placing a polarizer in the optical path as conventional spectrometers. Here, a novel 2D wavelength‐polarization dispersive microspectroscope based on a carbon nanocoil with plasmonic Au nanoparticles (Au/CNC) as a dispersive component is demonstrated. The unique 2D dispersion properties of Au/CNC are examined by microspectroscopic and Fourier spatial microscopic exploration. Au/CNC disperses light as wavelength to bands of different diffraction orders like a grating along the coil axis. The wavelength of the incident light can be obtained from the location of the signal lines in a relatively large visible‐near‐infrared wavelength range. Perpendicular to the coil axis, incident light is dispersed as polarization with bright and dark areas. Therefore, the left‐ and right‐circularly polarized light can be distinguished, and polarization orientation of linearly polarized light can be obtained. This effect provides a powerful microspectrometer that simultaneously analyzes wavelength and polarization features. Moreover, this potent tool can further evolve new revolutionary techniques via integration with other systems. [ABSTRACT FROM AUTHOR]

Plasmonic excitations decay within femtoseconds, leaving nonthermal (often referred to as "hot") charge carriers behind that can be injected into molecular structures to trigger chemical reactions that are otherwise out of reach─a process known as plasmonic catalysis. In this Letter, we demonstrate that strong coupling between resonator structures and plasmonic nanoparticles can be used to control the spectral overlap between the plasmonic excitation energy and the charge injection energy into nearby molecules. Our atomistic description couples real-time density-functional theory self-consistently to an electromagnetic resonator structure via the radiation-reaction potential. Control over the resonator provides then an additional knob for nonintrusively enhancing plasmonic catalysis, here more than 6-fold, and dynamically reacting to deterioration of the catalyst─a new facet of modern catalysis.

We have demonstrated localized surface plasmon (LSP)-enhanced cathodoluminescence (CL) from an atomic layer deposition (ALD)-grown Al2O3/ZnO/Al2O3 heterostructure to develop a bright nanometer-scale light source for an electron beam excitation-assisted (EXA) optical microscope. Three types of metals, Ag, Al, and Au, were compared, and an 181-fold enhancement of CL emission was achieved with Ag nanoparticles (NPs), with the plasmon resonance wavelength close to the emission wavelength energy of ZnO. The enhanced emission is plausibly attributed to LSP/exciton coupling. However, it is also attributed to an increase in coupling efficiency with penetration depth and also to an increase in light extraction efficiency by grading the refractive indices at the heterostructure., (© The Author(s) 2024. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site–for further information please contact journals.permissions@oup.com.)

Plasmon photocatalysis reactions are thought to occur through vibrationally activated reactants, driven by nonthermal energy transfer from plasmon-induced hot carriers. However, a detailed quantum-state-level understanding and quantification of the activation have been lacking. Using anti-Stokes surface-enhanced Raman scattering (SERS) spectroscopy, we mapped the vibrational population distributions of reactants on plasmon-excited nanostructures. Our results reveal a highly nonthermal distribution with an anomalously enhanced population of multiquantum excited states  ( v ≥ 2). The shape of the distribution and its dependence on local field intensity and excitation wavelength cannot be explained by photothermal heating or vibronic optical transitions of the metal-molecule complex. Instead, it can be modeled by hot electron-molecule energy transfer mediated by the transient negative ions, establishing direct links among nonthermal reactant activation, plasmon-induced hot electrons, and negative ion resonances. Moreover, the presence of multiquantum excited reactants, which are far more reactive than those in the ground state or first excited state, presents opportunities for vibrationally controlling chemical selectivities.

Surface Plasmonic Resonance (SPR) induced by metallic nanoparticles can be exploited to enhance the response of photodetectors (PD) to a large degree. Since the interface between metallic nanoparticles and semiconductors plays an important role in SPR, the magnitude of the enhancement is highly dependent on the morphology and roughness of the surface where the nanoparticles are distributed. In this work, we used mechanical polishing to produce different surface roughnesses for the ZnO film. Then, we exploited sputtering to fabricate Al nanoparticles on the ZnO film. The size and spacing of the Al nanoparticles were adjusted by sputtering power and time. Finally, we made a comparison among the PD with surface processing only, the Al-nanoparticles-enhanced PD, and the Al-nanoparticles-enhanced PD with surface processing. The results showed that increasing the surface roughness could enhance the photo response due to the augmentation of light scattering. More interestingly, the SPR induced by the Al nanoparticles could be strengthened by increasing the roughness. The responsivity could be enlarged by three orders of magnitude after we introduced surface roughness to boost the SPR. This work revealed the mechanism behind how surface roughness influences SPR enhancement. This provides new means for improving the photo responses of SPR-enhanced photodetectors.

A novel scheme of optical readout based on thermo-optic cavity coupled plasmonic scattering for infrared imaging sensor is proposed to lessen the complex and bulky of existed systems using reflective or diffractive optical readout schemes. This new scheme readouts thermally-modulated back-scattering visible light signals of metallic nanostructures under large-angle dark field illumination. Numerical simulation is employed to reveal the mechanisms of large temperature sensitivity and low angular sensitivity of scattering, which is attributed to the thermal-optic effects of Fabry–Perot (F-P) microcavity coupled with local surface plasmon resonance (LSPR) generated from metallic nanostructures. The feasibility of the proposed scheme is demonstrated by preliminary experiments and optical measurements. Thermal-optic modulated scattering spectra have been obtained for 3.39 μm infrared illumination and a temperature sensitivity of 0.24 nm/℃ for 605 ~ 640 nm band has been reached. This scheme provides a new approach to develop compact and low cost infrared imaging systems. [ABSTRACT FROM AUTHOR]

Optical feedback for either the excitation or the signal is an effective approach to enhance the detection sensitivity of Raman scattering spectroscopy. A combination of plasmonic and optical feedback schemes may supply multifold enhancement mechanisms with further improved efficiency. Herein, a plasmonic Bragg grating (PBG) consisting of periodically distributed silver nanoslabs coated onto the sidewalls of the grating lines is reported. Localized surface plasmons excited in the silver nanoslabs with a large width/thickness ratio facilitate enhanced local field and Raman interaction. Asymmetric Bragg diffraction not only supplies optical feedback along the grating plane to extend largely the laser–molecule interaction distance but also enables efficient collection of the Raman signal through back‐diffraction into the detection system. Such a design accomplishes "volume" surface‐enhanced Raman scattering with a modulation depth of more than 500 nm and strong optical feedback, extending largely the limited interaction distance of surface plasmons. With respect to the scheme using Ag films for enhancement, a further enhancement factor larger than 2.8 × 103 has been achieved by the PBG device in the direct detection of the low‐concentration water solution of R6G molecules. The discovered photophysics is potentially important for practical applications in in situ water pollutant detection. [ABSTRACT FROM AUTHOR]

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.

The electromagnetic multipole method has been extensively adopted for a better understanding of the physical mechanism of localized surface plasmon. In this work, we quantitatively decomposed the total extinction spectra of typical silver nanoparticles into multipole components, which are shown to be quite different from qualitative assignment of resonance peaks reported previously. Taking the quasi-normal mode method as reference standard, we examined the scope of application of the electromagnetic multipole method in assigning plasmonic resonance peaks, and pointed out the necessity of employing eigenmode-based approaches when interpreting plasmonic spectra, which can hopefully lead to more physical insights into the underlying mechanisms of plasmonics phenomena.

Dyes are important concerns regarding aquatic environmental contamination given their extensive industrial use and the occurrence of highly toxic and carcinogenic effects on the biota. In this work, photodegradation processes of the organic dye crystal violet (CV) by a hybrid plasmonic photocatalyst involving titanium dioxide (TiO 2) and silver nanoparticles (AgNP), through irradiation with low-power visible light were studied, and the experiments were tracked by ultraviolet-visible absorption (UV–VIS) and surface-enhanced resonance Raman scattering (SERRS) spectroscopies. Enhanced photocatalytic activity was observed, reaching about 71, 80 and 87 % of CV removal with only 100 minutes of irradiation, depending on the Ag loading used. The high photocatalytic efficiency is further highlighted by the low energy consumption in the process, requiring only ca. 1.46 kW h L-1 in the best reaction condition. Quantum-mechanical calculations were used to the assignment of electronic spectra, as well as to the prediction of frontier molecular orbitals and atomic charges, aiming to propose mechanisms for radical attacks. Such results allow suggesting degradation processes involved mainly N-demethylation and bond breaking of central carbon. The presence of CV protonated species was also supported through Density Functional Theory (DFT) investigation. The integration of theoretical and experimental results allows proposing the formation of pararosaniline, phenol and benzophenone derivatives, which may have highest ecotoxicity than the original contaminant, outstanding the remarkable relevance of SERRS spectroscopy in monitoring such recalcitrant substances. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

As an excellent clean medium for hydrogen storage and fuel cell applications, the photolysis of ammonia via localized surface plasmon could be invoked as a promising route towards significantly reducing the temperature for conventional thermolysis. Here, we explore the underlying microscopic mechanism of ultrafast carrier dynamics in plasmon-mediated NH3 photodecomposition at the single-molecular level using real-time time-dependent density functional theory. The NH3 molecule adsorbed on the tip of archetypal magic metal clusters represented by tetrahedral Ag20 and icosahedral Ag147, splits within a hundred femtoseconds upon laser pulse illumination. We found that the splitting of the first N-H bond is dominated by the intramolecular charge transfer driven by localized surface plasmon. Surprisingly, the phase of laser pulse could modulate the dynamics of charge transfer and thus affect the plasmon-induced bond breaking. These findings offer a new avenue for NH3 decomposition and provide in-depth insights in designing highly efficient plasmon-mediated photocatalysts. [ABSTRACT FROM AUTHOR]

In this work, periodic arrays of 3D composite structures consisting of gold nanoparticle (AuNP) capped VO2 shells on self‐assembled highly‐ordered SiO2 microspheres have been designed and fabricated, and their temperature‐tunable surface‐enhanced Raman scattering (SERS) performance is investigated. The results show that the SERS intensity enhancement factor (EF) for R6G molecules adsorbed on the AuNP‐capped VO2 shells increases from 8.3 × 105 to 3.9 × 106 when triggering the semiconductor‐to‐metal phase transition of VO2 by temperature rise, which strengthens the plasmonic coupling between the AuNPs and VO2 shells and consequently leads to a larger electric near‐field enhancement at the gaps between neighboring AuNPs. Such periodic arrays of AuNP‐capped VO2 shells with tunable plasmonic coupling can provide great opportunities for various optical applications, such as quantitative SERS detection of analytes, photothermal nano‐regulators, and biosensing in general. [ABSTRACT FROM AUTHOR]

Heat-assisted magnetic recording is a technology to improve recording density for hard disks. The authors' group has proposed a device, in which a gold nano-antenna as a near-field transducer is attached to a semiconductor ring resonator as an integrated light source. Localized surface plasmon resonance at the tip of nano-antenna excites near-field light to form small recorded marks to increase recording density. In this study, to improve the device performance, the dependence of spot size and energy density of near-field light on tip curvature, length, and bottom diameter of nano-antenna was investigated through a numerical simulation. Cylinder type and cone type nano-antennas were considered. For both types, as the tip curvature of nano-antenna increased, the spot size decreased and the energy density increased. It was possible to reduce the spot size to 18 × 18 nm2. For cylinder type, there was an optimal length of nano-antenna where the energy density became maximum, and the optimal length changed depending on the presence or absence of recording medium. This was because of the difference in plasmon resonance condition. Moreover, for cone type, there was an optimal bottom diameter of nano-antenna where the energy density became maximum, and the optimal bottom diameter changed depending on the length of nano-antenna. [ABSTRACT FROM AUTHOR]