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Understanding the dynamics of hot, highly energetic electrons resulting from nonradiative plasmon decay is crucial for optimizing applications in photocatalysis and energy conversion. This study presents an analysis of electron kinetics within plasmonic metals, focusing on the steady-state behavior during continuous-wave (CW) illumination. Using an inelastic spectroscopy technique, we quantify the temperature and lifetimes of distinct carrier populations during excitation. A significant finding is the monotonic increase in hot electron lifetime with decreases in electronic temperature. We also observe a 1.22× increase in hot electron temperature during intraband excitation compared to interband excitation and a corresponding 2.34× increase in carrier lifetime. The shorter lifetimes during interband excitation are hypothesized to result from direct recombination of nonthermal holes and hot electrons, highlighting steady-state kinetics. Our results help bridge the knowledge gap between ultrafast and steady-state spectroscopies, offering critical insights for optimizing plasmonic applications.

The detection of sub-ppm levels of nanoplastics using a surface-enhanced Raman scattering sensor was demonstrated. The proposed Au nanograting as surface-enhanced Raman scattering sensor, fabricated using nanoimprint lithography and oblique angle deposition, was designed to contain nanoplastics with enhanced local plasmonic fields. Electromagnetic simulations and Raman measurements show that the plasmonic field enhanced inside the nanograting enables the detection of Raman signal from 50-nm-sized polystyrene nanoparticles in 3-μL-droplets at a concertation of 0.1 ppm. Furthermore, the proposed sensor was applied to detect polystyrene in microwave-heated water in a disposable bowl. The results show that the proposed sensor offers promising potential for detecting nanoplastics released from plasticware. [ABSTRACT FROM AUTHOR]

Plasmonic superstructures offer broad prospects in photothermal catalysis, yet their controllable synthesis remains a challenge. Here, a controlled synthesis method for Cu‐Ru plasmonic superstructures via a one‐step polyol reduction process is presented, where Cu nanoparticles serve as the core, while the shell is formed from Ru nanoclusters. Through a comprehensive investigation of the growth mechanism, precise control over the composition and size of the superstructures is achieved. Finite‐difference time‐domain  simulations and photothermal conversion experiments demonstrated that the optimized Cu3Ru1 superstructures possess strong light absorption capabilities and efficient photothermal conversion performance. These properties are effectively utilized in the photothermal recycling of waste polyethylene and polyethylene terephthalate, marking a significant advance in employing Cu‐based plasmonic materials for sustainable catalytic technology. [ABSTRACT FROM AUTHOR]

Over the past three decades, plasmonic nanostructures, particularly spherical ones, have seen remarkable advancements. Recently, attention has shifted toward anisotropic nanoparticles, especially star‐shaped/branched structures such as plasmonic nanostars (PNS), due to their distinct properties. PNS offers superior electromagnetic enhancement effects, larger surface areas, and as well as non‐linear and unusual photothermal properties, setting them apart from spherical counterparts. Despite significant progress in synthetic methods and characterization of the particles, challenges remain in transitioning PNS technology into practical use. In this perspective article, the distinctive attributes of PNS in biosensing applications are discussed, beginning with an exploration of synthesis methodologies. Their optoelectronic properties are examined and discussed how these properties influence their interaction with different molecules from a biosensing perspective. With a focus on PNS, detailed insights are offered into their unique properties, current applications, and future potential. By fostering discussion and understanding of PNS development, this article aims to facilitate the translation of PNS technology into practical applications, encouraging targeted improvements and advancements. [ABSTRACT FROM AUTHOR]

Silver nanowire (AgNWs) is a typical precious metal nanowire with excellent electrical conductivity, light transmittance, and flexural resistance, which can be widely used in the fields of catalysis, optoelectronics, flexible display devices and biomedicine. We have prepared gold-silver bimetallic nanostructures based on AgNWs as templates and controlled gold nanoparticles coating on the surface of AgNWs by chemical reduction method. The catalytic efficacy of this gold-silver bimetallic nanowires (AuAg BNWs) for the hydroreduction of 4-nitrophenol to 4-aminophenol was analyzed using this nanostructure as a nanocatalyst. Due to the large number of small-sized gold nanoparticles on the surface of the nanostructure, it shows good catalytic activity, and the apparent rate constants and the turnover frequency reach 0.108− 1 min and 43.41 h− 1, respectively. In addition, the surface enhanced Raman scattering (SERS) properties of this AuAg BNWs structure were analyzed using crystal violet as a probe molecule. Because the plasmonic-enhanced localized electric field effect, the nanostructure also exhibited good SERS enhanced properties. Based on these studies, it is advantageous to the preparation of gold-silver bimetallic nanostructures and their applications in catalysis and SERS sensing. [ABSTRACT FROM AUTHOR]

Integrating two-dimensional layered supercell (LSC) oxides and plasmonic Au nanostructures into one hybrid framework can open up multifunctionality tuning into a new level. In this work, Bi-based LSCs Bi3Fe2Mn2Ox and Bi2WO6 incorporated with secondary plasmonic Au and/or ferromagnetic La0.7Sr0.3MnO3 phases have been grown via pulsed laser deposition (PLD). Microstructural characterization results show the highly epitaxy film quality and distinct LSC structures despite the incorporated secondary phases. The nanocomposite films exhibit multiferroic and plasmonic responses due to the multi-phase coupling. This work provides a new approach of integrating self-assembled LSC-metal/oxide nanocomposite thin films for future multiferroics and spintronics device applications. [ABSTRACT FROM AUTHOR]

The fabrication of core–satellite (CS) assemblies offers a versatile strategy for tailoring the optical properties of plasmonic nanomaterials. In addition to key factors like size, shape, and spatial arrangement of individual components, the combination of plasmonic units with different compositions (e.g., gold and silver) has been demonstrated to produce materials with enhanced properties and functionalities applicable across a range of fields. Notably, several CS assembly variants have emerged as promising substrates for surface-enhanced Raman spectroscopy (SERS). In this study, we address a gap in the knowledge by conducting a systematic cross-comparison of the optical and SERS properties of highly bright homo- and bimetallic CS assemblies. We evaluated the SERS efficiencies of these different superstructures across various excitation wavelengths and supported our findings with numerical simulations. The insights gained from this study offer a valuable foundation for researchers seeking to select and optimize the most suitable CS assemblies for their given SERS application. [ABSTRACT FROM AUTHOR]

Anti-Stokes Raman thermometry, a rapidly evolving field in Raman spectroscopy, was investigated for in situ cellular temperature measurementsa critical aspect in photothermal cancer therapy. In this study, multiwalled carbon nanotubes decorated with gold nanorods (MWCNTs-GNRs) were employed as nanothermometer probes. Characterization involved the analysis of individual Raman spectra acquired at various powers and initial temperatures. The changes observed in the Raman spectra of MWCNTs-GNRs, particularly in response to variations in temperature and excitation power, provide the necessary information to develop a reliable Raman thermometry. This methodology facilitated the extraction of the intrinsic photothermal heating coefficient of MWCNTs-GNRs, offering essential insights into their thermometric properties. An evaluation was extended to incubating MWCNTs-GNRs with prostate cancer PC3 cell lines, where anti-Stokes and Stokes signals were measured at different laser powers to assess in situ cellular temperatures. Temperature maps for a selected area were generated for MWCNTs-GNRs and a single PC3 cell incubated with MWCNTs-GNRs with data standard error analysis performed to indicate a certain level of reliability in temperature measurement accuracy. Cell viability was determined through trypan blue assays, and the obtained temperatures were correlated with viability outcomes at different laser powers. Our investigation encompassed a temperature range spanning 60–100 °C, transcending the critical temperature threshold of 50 °C, which is associated with inducing cell demise. The study highlights the potential of MWCNTs-GNRs as nanothermometer probes for targeted photothermal therapies. [ABSTRACT FROM AUTHOR]

By depositing a dielectric fiber on top of 3D Dirac semi‐metal (DSM) and Au layers, the tunable propagation properties of hybrid modes are systematically investigated in the mid‐infrared regime, including the effects of the temperatures, the Fermi levels, and rotation angles. Interestingly, due to the importance of inter‐band transition in the mid‐infrared spectral regime, a strong temperature related epsilon‐near‐zero (ENZ) phenomenon has manifested near the transition frequency. Namely, below room temperature, the real part of the effective refractive index (propagation length) shows a peak (valley). Particularly, at 77 K, the according abruption ratio (ratio of maximum to minimum in ENZ region) is 9.71 (204.1). Additionally, the propagation properties are also closely associated with the Fermi level. When the Fermi level varies in the range of 0.08–0.15 eV, the peak position of the real part of the effective refractive index shifts blue from 21.3 to 38.2 THz, and the according abruption ratio of the propagation length can be modulated in the range of 3.81–45.3. These results are very useful for designing tunable plasmonic devices, such as cutting‐edge modulator, filter, and resonators. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative optical biosensor designed for multimode refractive index (MMRI) detection, employing split ring resonator (SRR) technology for enhanced sensitivity in cancer cell analysis. The proposed biosensor comprises two concentric SRRs, one resembling a cube and the other a cylinder, each incorporating an air gap. Rigorous analysis and optimization of dimensional parameters were conducted using the finite difference time domain (FDTD) numerical solution method. The simulation results demonstrated that the biosensor achieves exceptional sensitivity and an optimal figure of merit (FOM). Specifically, the first mode of the biosensor exhibited a sensitivity exceeding 80 nm/RIU and an FOM surpassing 20 RIU⁻1, while the second mode demonstrated a sensitivity of 570 nm/RIU and an FOM exceeding 4 RIU⁻1. These results indicate that the first mode benefits from a higher FOM, enhancing precision and accuracy, while the second mode benefits from high sensitivity, enabling the detection of minute refractive index changes. With a primary focus on early cancer cell detection and timely treatment initiation to address the global cancer mortality burden, the biosensor's high-quality factor (Q-factor) and FOM promise significant advancements in cancer diagnostics and therapeutic interventions. [ABSTRACT FROM AUTHOR]

A novel plasmonic waveguide structure consisting of a rectangular resonator side coupled with a split ring resonator (SRR) and a metal–insulator–metal (MIM) waveguide with metal baffle was proposed. The transmission characteristics of the present structure were simulated by a finite-difference time-domain (FDTD) method. The results show that the structure can realize three typical plasmonically-induced reflection (PIR) windows. Meantime, the PIR window can be tuned vertically and horizontally, respectively, and multiple PIR windows with different wavelength intervals can also be obtained by changing the split position. In addition, the sensitivity of the proposed structure can reach up to 1,075 nm/RIU. Furthermore, a rectangular resonator was added to the other side of the plasmonic waveguide structure for realizing the dual-channel PIR window. Another SRR was added to form a symmetrical structure, which further improved the sensitivity and transmittance. Undoubtedly, the proposed structure will have potential applications in sensor and optical switches. [ABSTRACT FROM AUTHOR]

Localized surface plasmon resonance (LSPR) in plasmonic nanomaterials can concentrate light in the nano‐dimension, leading to an enhancement of the light intensity by order of magnitude. While LSPR is a subject of extensive research in chalcogenide semiconductor nanocrystals (NCs), research on tellurium multinary chalcogenides (MnCs) remains elusive, possibly due to non‐availability of the corresponding quantum dots (QDs). In this report, we show the sequential switching of plasmonic to non‐plasmonic properties during the colloidal synthesis of AgInTe2 QDs. The reaction passes through several intermediates including AgInTe2/AgIn5Te8 core/shell NCs, AgInTe2 microrods (MRs), AgInTe2 QDs, and finally AgInTe2 quantum dot chain (QDC). Here, the AgInTe2/AgIn5Te8 core/shell NCs and AgInTe2 QDs depict strong LSPR absorption in the visible‐NIR region until ~2000 nm. We propose that small‐size quantum confined and cation deficient AgInTe2 particles are responsible for the observation of LSPR modes in both cases due to presence of the free carriers (holes). Our work on developing Te‐based plasmonic MnC QDs may find significant advancement in the nanoscale light‐matter interaction in semiconductor research. [ABSTRACT FROM AUTHOR]

We propose and numerically investigate a D-shaped SPR fiber sensor based on Au nanowire grating-zinc oxide (ZnO) nanofilm hybrid structure. Plasmonic mode couplings are investigated by birefringence analysis. The resonance peak can be found by searching the wavelength where birefringence is zero. It proves that in visible and near-infrared (NIR) region, ZnO nanofilm can greatly improve the refractive index sensitivity (RIS) of the sensor, which is the result of the promoted photon interaction and enhanced electric field intensity at the metal–semiconductor junction. The calculated maximum RIS is 15,433 nm/RIU within a wide refractive index detection range of 1.29–1.42, which is better than most reported D-shaped SPR fiber sensors to the best of our knowledge. In addition, it's found ZnO nanofilm inhibits the coupled intensity of degenerate mode in x direction to some extent, and the degree of inhibition is related to the film thickness, which might be due to its large dielectric constant. [ABSTRACT FROM AUTHOR]

The manuscript presents the design and investigation of square and L-shaped graphene plasmonic nano-antenna arrays on a silicon dioxide substrate for plasmonic biosensing applications. The design parameters, such as the shape of the nanostructure, spacing between the antenna array elements, size of the antenna array and chemical potential of the graphene are used to analyze the plasmonic resonance characteristics of the proposed plasmonic nano-antenna array. Initially, dispersive characteristics of graphene, such as conductivity, permittivity and refractive index are analyzed using its chemical potential for the validation of the graphene material for plasmonic sensing applications. The proposed square and L-shaped nanopatch antenna structures are radiating at 30 THz with a reflection coefficient of -28.4 dB and − 44.6 dB respectively at 0.1 eV chemical potential. It is observed that graphene nanopatch antenna radiates at 30 THz, 115 THz and 176 THz at a chemical potential of 1.3 eV. Further, the study demonstrated that the designed square and L-shaped nano-antenna exhibit a gain of 3.52 dB and 9.51 dB respectively at 30 THz. The gain can be increased further using a square and L-shaped nano-antenna array of dimensions 2 × 2, 3 × 3 and 4 × 4. It is observed that maximum gains of 33.44 dB and 30.86 dB are obtained for the square and L-shaped 4 × 4 plasmonic nanoarray antenna respectively. Finally, a nanocircuit model of square and L-shaped nano-antennas is proposed and validated through CST simulations. [ABSTRACT FROM AUTHOR]

Abstract In this paper, we report a graphene-based plasmonic photodetector optimized using the particle swarm optimization (PSO) algorithm and compatible with complementary metal–oxide–semiconductor (CMOS) technology. The proposed photodetector structure is designed to minimize fabrication challenges and reduce production costs compared to more complex alternatives. Graphene has been used for its unique properties in the detection region, titanium nitride (TiN) as a CMOS-compatible metal, and both to aid in plasmonic excitation. Photodetectors have key parameters influenced by multiple independent variables. However, practical constraints prevent thorough adjustment of all variables to achieve optimal parameter values, often resulting in analysis based on several simplified models. Here we optimize these variables by presenting a new approach in the field of photodetectors using the capabilities of the PSO algorithm. As a result, for the proposed device at the wavelength of 1550 nm, the voltage responsivity is 210.6215 V/W, the current responsivity is 3.7213 A/W, the ultra-compressed length is less than 3 $$\mu {\text{m}}$$ μ m , and the specific detectivity is 2.566× $${10}^{7}$$ 10 7 Jones were obtained. Furthermore, the device in question works under the photothermoelectric effect (PTE) at zero bias and has zero dark current, which ultimately resulted in a very low noise equivalent power (NEP) of 4.5361 $${\text{pW}}/\sqrt{\text{Hz}}$$ pW / Hz .

Abstract Surface-enhanced Raman scattering (SERS) exploits localized surface plasmon resonances in metallic nanostructures to significantly amplify Raman signals and perform ultrasensitive analyses. A critical factor for SERS-based analysis systems is the formation of numerous electromagnetic hot spots within the nanostructures, which represent regions with highly concentrated fields emerging from excited localized surface plasmons. These intense hotspot fields can amplify the Raman signal by several orders of magnitude, facilitating analyte detection at extremely low concentrations and highly sensitive molecular identification at the single-nanoparticle level. In this study, mesoscopic star-shaped gold particles (gold mesostars) were synthesized using a three-step seed-mediated growth approach coupled with the addition of silver ions. Our study confirms the successful synthesis of gold mesostars with numerous sharp tips via the multi-directional growth effect induced by the underpotential deposition of silver adatoms (AgUPD) onto the gold surfaces. The AgUPD process affects the nanocrystal growth kinetics of the noble metal and its morphological evolution, thereby leading to intricate nanostructures with high-index facets and protruding tips or branches. Mesoscopic gold particles with a distinctive star-like morphology featuring multiple sharp projections from the central core were synthesized by exploiting this phenomenon. Sharp tips of the gold mesostars facilitate intense localized electromagnetic fields, which result in strong SERS enhancements at the single-particle level. Electromagnetic fields can be further enhanced by interparticle hot spots in addition to the intraparticle local field enhancements when arranged in multilayered arrays on substrates, rendering these arrays as highly efficient SERS-active substrates with improved sensitivity. Evaluation using Raman-tagged analytes revealed a higher SERS signal intensity compared to that of individual mesostars because of interparticle hot spots enhancements. These substrates enabled analyte detection at a concentration of 10− 9 M, demonstrating their remarkable sensitivity for trace analysis applications.

This paper introduces a novel class of low-loss and cost-effective optical planar structures tailored for magnetic detection applications. These structures represent unconventional magneto-plasmonic devices specifically optimized for an ‘optical switch’ configuration. The structure consists of a 1D deep sinusoidal gold grating covered by a thin cobalt layer. In this unique arrangement, the excited plasmon induces a high-contrast switching phenomenon between the reflected free space intensity of specular (0th) and −1st diffracted orders, sensitive to any transverse magnetic fields applied to the cobalt layer. The use of these two distinct diffracted orders induces differential measurements, effectively mitigating common drift and perturbations. This innovative approach results in an enhanced detection sensitivity, showcasing the potential of these structures for advanced magnetic field sensing applications.

Abstract In recent years, graphene field-effect-transistors (GFETs) have demonstrated an outstanding potential for terahertz (THz) photodetection due to their fast response and high-sensitivity. Such features are essential to enable emerging THz applications, including 6G wireless communications, quantum information, bioimaging and security. However, the overall performance of these photodetectors may be utterly compromised by the impact of internal resistances presented in the device, so-called access or parasitic resistances. In this work, we provide a detailed study of the influence of internal device resistances in the photoresponse of high-mobility dual-gate GFET detectors. Such dual-gate architectures allow us to fine tune (decrease) the internal resistance of the device by an order of magnitude and consequently demonstrate an improved responsivity and noise-equivalent-power values of the photodetector, respectively. Our results can be well understood by a series resistance model, as shown by the excellent agreement found between the experimental data and theoretical calculations. These findings are therefore relevant to understand and improve the overall performance of existing high-mobility graphene photodetectors. Graphical Abstract

Abstract In this work, a multispectral aptasensor structure, including a sub-layer and two side walls, was presented. The cells are positioned at the down and top of the structure, with the down cells oriented perpendicular to the walls and the top cells aligned parallel to the walls. The validity of the findings was verified by the utilization of a numerical simulation technique known as 3D Finite Difference Time Domain (FDTD). The biosensor under consideration exhibits sensitivities of 1093.7 nm/RIU, 754 nm/RIU, and 707.43 nm/RIU in mode III, mode II, and mode I, respectively. In the majority of instances, the quantity of analyte available is insufficient to coat the surface of the sensor thoroughly. Consequently, in this study, the evaluation of surface sensitivity was undertaken alongside bulk sensitivity. The surface sensitivity of the suggested structure for mode II in the sensor layer, with thicknesses of 10, 20, 30, and 70 nm, is measured to be 25, 78, 344, and 717.636 nm/RIU, respectively. Our design incorporates a unique arrangement of sub-layer and side walls, with cells positioned to maximize interaction with the target analyte. This innovative configuration, combined with Ag for its superior plasmonic properties, enables the detection of E. coli O157 with remarkable sensitivity.

Herein, a localized surface plasmon resonance‐based sensor for volatile organic compounds (VOCs) detection is developed. The sensors are fabricated as a hybrid nanostructure of gold nanoparticles coated with a tantalum oxide (TaO) thin film on a glass slide substrate through magnetron sputtering and thermal solid‐state dewetting techniques. The thickness of the TaO film varies between 10 and 70 nm. The optical properties of samples are characterized by UV‐Vis‐NIR spectrophotometry, while their morphologies are confirmed via transmission electron microscopy. The results show the shift of the minimum optical transmittance related to the TaO thickness. Electrical field simulations are performed to predict the sensitivity of the prepared samples for VOCs detection. In addition, the sensors are tested with different VOCs, including formaldehyde, isopropanol, acetone, and methanol, which show good potential for practical applications. [ABSTRACT FROM AUTHOR]

The optoelectronic resistive random‐access memory (RRAM) with the integrated function of perception, storage and intrinsic randomness displays promising applications in the hardware level in‐sensor image cryptography. In this work, 2D hexagonal boron nitride based optoelectronic RRAM is fabricated with semitransparent noble metal (Ag or Au) as top electrodes, which can simultaneous capture color image and generate physically unclonable function (PUF) key for in‐sensor color image cryptography. Surface plasmons of noble metals enable the strong light absorption to realize an efficient modulation of filament growth at nanoscale. Resistive switching curves show that the optical stimuli can impede the filament aggregation and promote the filament annihilation, which originates from photothermal effects and photogenerated hot electrons in localized surface plasmon resonance of noble metals. By selecting noble metals, the optoelectronic RRAM array can respond to distinct wavelengths and mimic the biological dichromatic cone cells to perform the color perception. Due to the intrinsic and high‐quality randomness, the optoelectronic RRAM can produce a PUF key in every exposure cycle, which can be applied in the reconfigurable cryptography. The findings demonstrate an effective strategy to build optoelectronic RRAM for in‐sensor color image cryptography applications. [ABSTRACT FROM AUTHOR]

We investigated the formation of nanoporous metallic networks through a physical vapor deposition (PVD) process. Utilizing transmission electron microscopy (TEM), we observe the early stages of growth, revealing the presence of large pores and pillars. Our findings highlight the significant influence of the electrostatic nature of the substrate on the metallic network growth, where repulsion and attraction mechanisms come into play during the deposition process. We extend the applicability of this method, demonstrating its versatility in fabricating macroscopic metallic networks composed of submicrometer building blocks on different substrates, among them an amber stone, in a one-step process. The resulting three-dimensional (3D) networks display distinctive nonlinear optical properties, including enhanced second harmonic generation (SHG) and surface-enhanced Raman scattering (SERS) responses. The latter is used to detect contamination in water down to 10–8 M. [ABSTRACT FROM AUTHOR]

The integration of nanocomposite thin films with combined multifunctionalities on flexible substrates is desired for flexible device design and applications. For example, combined plasmonic and magnetic properties could lead to unique optical switchable magnetic devices and sensors. In this work, a multiphase TiN-Au-Ni nanocomposite system with core–shell-like Au-Ni nanopillars embedded in a TiN matrix has been demonstrated on flexible mica substrates. The three-phase nanocomposite film has been compared with its single metal nanocomposite counterparts, i.e., TiN-Au and TiN-Ni. Magnetic measurement results suggest that both TiN-Au-Ni/mica and TiN-Ni/mica present room-temperature ferromagnetic property. Tunable plasmonic property has been achieved by varying the metallic component of the nanocomposite films. The cyclic bending test was performed to verify the property reliability of the flexible nanocomposite thin films upon bending. This work opens a new path for integrating complex nitride-based nanocomposite designs on mica towards multifunctional flexible nanodevice applications. [ABSTRACT FROM AUTHOR]

Terahertz (THz) fields are increasingly being used to address the critical challenges associated with achieving high data rates and rapid communication. In this study, a hybrid plasmonic THz waveguide is designed and analysed operating in the 2.5–3.5 THz frequency range. The waveguide is constructed using gallium arsenide as the high-refractive-index core, surrounded by aluminium arsenide and silver placed on a high-density polyethylene (HDPE) substrate. Graphene is strategically positioned between the HDPE layers to enhance light confinement. The mode properties of the proposed waveguide are simulated with Comol Multiphysics using the finite-element method and show unique characteristics. Observation of the simulated results at 2.5–3.5 THz reveals a high effective refractive index of 3.79, a maximum effective mode area of 1.88 mm2, a high birefringence of 0.2, a low dispersion of 0.10 ps THz−1 cm−1, a high mode field diameter of 15.8 mm, a high beat length of 123 mm and a low confinement loss of 1.79 × 10−9 mm−1. These features make the proposed waveguide suitable for applications in photonic integrated circuits for THz communications. [ABSTRACT FROM AUTHOR]

We theoretically study the polarization of plasmonic fields in a hybrid nanosystem composed of three different metallic nano ellipsoid and a semiconductor quantum dot. The components of the hybrid nanosystem interact with three electromagnetic fields and one another via dipole-dipole interactions. We derive the density matrix equations at a steady state for the description of the optical properties of the hybrid nanosystem. The polarization of the plasmonic fields induced on the prolate, spherical, and oblate nano ellipsoid is calculated. We find that the polarization of the plasmonic fields depends on the number of the metallic nanoparticles (ellipsoid), the depolarization factor of the metallic nano ellipsoid, the direction of the plasmonic field, and the metallic nano ellipsoid parameters of the hybrid nanosystem. The phenomena of electromagnetically induced transparency (EIT) and electromagnetically induced transparency with amplification (EITA) are obtained in this work. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated a tunable and high transmission efficiency plasmonic power splitter and also a wavelength demultiplexer based on metal–insulator-metal surface. By using Finite Difference Time Domain method, the power splitter exhibits high transmission peaks of about 45% in each output port. Additionally, the simulation results demonstrate that the equal transmitted wavelengths of the two output ports can be easily tuned by changing the geometric parameters of the waveguide. Subsequently, the structure was amended to become a demultiplexer with selecting wavelengths of 1272 and 912 nm, and transmission efficiencies of 76.44 and 88.03%, respectively. Following that, the dependence of demultiplexing wavelengths on geometrical parameters of the structure is investigated. Besides being highly compact and efficient, having narrow-band spectra and low reflectance coefficient are the other main advantages of these devices. The compact power splitter presented in this study is one of the critical components of an integrated processor and hence can be of great interest in a wide range of applications, from highly integrated photonic circuits to on-chip optoelectronic modules and other optical devices such as erbium-doped fiber amplifiers. [ABSTRACT FROM AUTHOR]

The synthesis of ordered gold‐copper (Au3Cu) alloy nanocrystals (≈10 nm) is reported and used in the semiconductor (2H) to metallic (1T) phase transformation of an atomically thin large‐area 2D‐MoS2 grown via CVD technique. The ordered Au3Cu nanocrystals are dispersed over 2D‐MoS2, and the phase transformation is confirmed via Raman spectroscopy followed by X‐ray photoelectron spectroscopy (XPS), while the surface properties of the Au3Cu/2D‐MoS2 is determined by the XPS valence band analysis and ultra‐violet photoemission spectroscopy (UPS). By comparing overpotential and Tafel slopes for Hydrogen Evolution Reaction (HER), a decrease is observed in overpotential by 83.2 mV and Tafel slope by ≈58.25 mV per decade for Au3Cu/MoS2 on light irradiation. This electrocatalytic enhancement of Au3Cu/MoS2 refers to the transformation of semiconducting 2D‐MoS2 to metallic phase under light illumination, thereby altering the surface electronic structures, improving carrier concentrations, lowering the valence band edge, and lowering the free energy of H* adsorption/desorption. Density functional theory (DFT) calculations, along with other surface characterizations, further illustrate that the ordered nanocrystal‐induced phase transformation in 2D‐MoS2 leads to a more durable metallic characteristic, thus, enhancing the surface electrical conductivity, reducing surface potential and Gibbs free energy, and improving the kinetics of photoelectrocatalytic performance of the hybrid structure. [ABSTRACT FROM AUTHOR]

In this paper, we report a graphene-based plasmonic photodetector optimized using the particle swarm optimization (PSO) algorithm and compatible with complementary metal–oxide–semiconductor (CMOS) technology. The proposed photodetector structure is designed to minimize fabrication challenges and reduce production costs compared to more complex alternatives. Graphene has been used for its unique properties in the detection region, titanium nitride (TiN) as a CMOS-compatible metal, and both to aid in plasmonic excitation. Photodetectors have key parameters influenced by multiple independent variables. However, practical constraints prevent thorough adjustment of all variables to achieve optimal parameter values, often resulting in analysis based on several simplified models. Here we optimize these variables by presenting a new approach in the field of photodetectors using the capabilities of the PSO algorithm. As a result, for the proposed device at the wavelength of 1550 nm, the voltage responsivity is 210.6215 V/W, the current responsivity is 3.7213 A/W, the ultra-compressed length is less than 3 μ m , and the specific detectivity is 2.566× 10 7 Jones were obtained. Furthermore, the device in question works under the photothermoelectric effect (PTE) at zero bias and has zero dark current, which ultimately resulted in a very low noise equivalent power (NEP) of 4.5361 pW / Hz . [ABSTRACT FROM AUTHOR]

In this paper, a dual-layer plasmonic material-based electro-absorption modulator (EAM) is designed and investigated. Indium-tin-oxide (ITO), along with dielectric materials such as boron nitride (hBN) and hafnium dioxide (HfO2), is integrated into the Si waveguide for tuning the light propagating inside the device. The device showed enhanced performance in terms of extinction ratio (ER) = 34.48 dB/µm, the figure of merit (FOM) = 493, and insertion loss (IL) = 0.06 dB/µm for On-state at 1.55 µm wavelength. Also, the dual-state behavior of the EAM was observed and investigated. An IL of 22.22 dB/µm and 25.39 dB/µm was observed for the Off-On and On-Off configurations, respectively. A modulation frequency (${f_{3dB}}$ f 3 dB ) of 1.72 THz and 340 GHz was achieved for the EAM with hBN and HfO2 as the dielectric material. The investigated EAM with different dielectric materials has the potential to be integrated into future-generation photonic integrated circuits (PICs). [ABSTRACT FROM AUTHOR]

Now a days, plenty of nanostructured absorbers have been designing and investigating by employing various novel materials. In this paper, we employ a single-layer and ultrathin plasmonic absorber based on MXene, comprising of subwavelength-sized array of nano-cylinders. The proposed MXene-based absorber contains a three-layer device structure, having a top and bottom layer comprising MXene, a middle dielectric layer of Aluminium Nitride (AlN). It presents a large absorption window and shows an absorption value of 90% in a long operating wavelength ranging from 400 to 2600 nm. The discussed MXene-based plasmonic absorber does not change its absorption features by varying the different polarization angles and this is attributed to the symmetric structure of the constituent design. Additionally, the absorber also holds good absorption characteristics even at larger incident angles up to 60°. The proposed MXene-based absorber shows potential for various interesting applications, including photovoltaics, solar energy harvesting, and infrared imaging. [ABSTRACT FROM AUTHOR]

Surface-enhanced Raman scattering (SERS) exploits localized surface plasmon resonances in metallic nanostructures to significantly amplify Raman signals and perform ultrasensitive analyses. A critical factor for SERS-based analysis systems is the formation of numerous electromagnetic hot spots within the nanostructures, which represent regions with highly concentrated fields emerging from excited localized surface plasmons. These intense hotspot fields can amplify the Raman signal by several orders of magnitude, facilitating analyte detection at extremely low concentrations and highly sensitive molecular identification at the single-nanoparticle level. In this study, mesoscopic star-shaped gold particles (gold mesostars) were synthesized using a three-step seed-mediated growth approach coupled with the addition of silver ions. Our study confirms the successful synthesis of gold mesostars with numerous sharp tips via the multi-directional growth effect induced by the underpotential deposition of silver adatoms (AgUPD) onto the gold surfaces. The AgUPD process affects the nanocrystal growth kinetics of the noble metal and its morphological evolution, thereby leading to intricate nanostructures with high-index facets and protruding tips or branches. Mesoscopic gold particles with a distinctive star-like morphology featuring multiple sharp projections from the central core were synthesized by exploiting this phenomenon. Sharp tips of the gold mesostars facilitate intense localized electromagnetic fields, which result in strong SERS enhancements at the single-particle level. Electromagnetic fields can be further enhanced by interparticle hot spots in addition to the intraparticle local field enhancements when arranged in multilayered arrays on substrates, rendering these arrays as highly efficient SERS-active substrates with improved sensitivity. Evaluation using Raman-tagged analytes revealed a higher SERS signal intensity compared to that of individual mesostars because of interparticle hot spots enhancements. These substrates enabled analyte detection at a concentration of 10− 9 M, demonstrating their remarkable sensitivity for trace analysis applications. [ABSTRACT FROM AUTHOR]

A fiber-based surface plasmon resonance (SPR) sensor is investigated in this study. Initially, a D-shaped optical fiber is studied under different types and brands of light sources, optical spectrometers, and polarizing angles. The best stability with low noise is a supercontinuum light source with Avantes spectrometer. Using the polarizer controller to tune the width and dip shows the minimum absorption point when waveplates are set at 90°, 0°, and 45°. The temperature effects are recognized as shifts in absorption ranging from 30 to 60 °C for fiber-based SPR (with and without a polarizer controller). In the photoelastic effect, the sensor shows significant variation according to the applied load, with a maximum sensitivity of 1.05 nm/g at 5 g weight. Stability, response time, and selectivity are also discussed. Results are used to analyze the plasmonic sensor efficiency for Hg ions detection. It appears that there is a lack of information regarding the light types and polarization angles within a D-shaped fiber for Hg ions SPR sensor. As of now, there seems to be no published literature that has thoroughly explored this topic under different conditions. [ABSTRACT FROM AUTHOR]

Plasmonics is an emerging and very advantageous technology which provides high speed and tiny size devices for fulfilling the demand of today's high-speed world. SPPs are the information carrying elements in plasmonics, which are capable of breaking the diffraction limit. Plasmonics technology has shown its application in uncountable nanophotonic applications like switching, filtering, light modulation, sensing and in many more fields. Modulators are the key components of integrated photonic system. Various modulators which work on different effects are discussed in this study for providing a universal idea of modulators to researchers. Some useful plasmonic active materials are also discussed which are used in most of plasmonic modulators and other active devices. Previously, many researchers have worked on many kinds of modulators and switches, which operate on different kind of operating principles. For providing an overview about plasmonic modulators, their classification and their operation, we have discussed the state of art of some previously introduced modulators and switches which operates on electro-refractive effects and include electro-optic effect, Pockels effect, free charge carrier dispersion effect, phase change effect, elasto-optic effect, magneto-optic effect, and thermo-optic effect. Instead of different effects used in plasmonic switches and modulators different active materials like liquid crystals, graphene, vanadium di-oxide, chalcogenides, polymers, indium tin oxide, bismuth ferrite, barium titanate, and lithium niobate are also explained with their properties. Additionally, we also compared modulators based on different effects in terms of their design characteristics and performances. [ABSTRACT FROM AUTHOR]

Structural engineering has proven effective in tailoring the photocatalytic properties of semiconductor nanostructures. In this work, a sophisticated double‐hollow yolk@shell nanostructure composed of a plasmonic, mobile, hollow Au nanosphere (HGN) yolk and a permeable, hollow CdS shell is proposed to achieve remarkable solar hydrogen production. The shell thickness of HGN@CdS is finely adjusted from 7.7, 18.4 to 24.5 nm to investigate its influence on the photocatalytic performance. Compared with pure HGN, pure CdS, a physical mixture of HGN and CdS, and a counterpart single‐hollow cit‐Au@CdS yolk@shell nanostructure, HGN@CdS exhibits superior hydrogen production under visible light illumination (λ = 400–700 nm). The apparent quantum yield of hydrogen production reaches 8.2% at 320 nm, 6.2% at 420 nm, and 4.4% at 660 nm. The plasmon‐enhanced activity at 660 nm is exceptional, surpassing the plasmon‐induced photoactivities of the state‐of‐the‐art plasmonic photocatalysts ever reported. The superiority of HGN@CdS originates from the creation of charge separation state at HGN/CdS heterojunction, the considerably long‐lived hot electrons of plasmonic HGN, the magnified electric field, and the advantageous features of double‐hollow yolk@shell nanostructures. The findings can provide a guideline for the rational design of versatile double‐hollow yolk@shell nanostructures for widespread photocatalytic applications. [ABSTRACT FROM AUTHOR]

In this paper, we study both theoretically and experimentally the sensitivity of bimodal interferometric sensors where interference occurs between two plasmonic modes with different properties propagating in the same physical waveguide. In contrast to the well-known Mach–Zehnder interferometric (MZI) sensor, we show for the first time that the sensitivity of the bimodal sensor is independent of the sensing area length. This is validated by applying the theory to an integrated plasmo-photonic bimodal sensor that comprises an aluminum (Al) plasmonic stripe waveguide co-integrated between two accessible SU-8 photonic waveguides. A series of such bimodal sensors utilizing plasmonic stripes of different lengths were numerically simulated, demonstrating bulk refractive index (RI) sensitivities around 5700 nm/RIU for all sensor variants, confirming the theoretical results. The theoretical and numerical results were also validated experimentally through chip-level RI sensing experiments on three fabricated SU-8/Al bimodal sensors with plasmonic sensing lengths of 50, 75, and 100 μm. The obtained experimental RI sensitivities were found to be very close and equal to 4464, 4386, and 4362 nm/RIU, respectively, confirming that the sensing length has no effect on the bimodal sensor sensitivity. The above outcome alleviates the design and optical loss constraints, paving the way for more compact and powerful sensors that can achieve high sensitivity values at ultra-short sensing lengths. [ABSTRACT FROM AUTHOR]

The rapid development of the battery industry has brought about a large amount of waste battery pollution. How to realize the high-value utilization of waste batteries is an urgent problem to be solved. Herein, cobalt and titanium compounds (LTCO) were firstly recovered from spent lithium-ion batteries (LIBs) using the carbon thermal reduction approach, and plasmonic attapulgite/Co(Ti)Ox (H-ATP/Co(Ti)Ox) nanocomposites were prepared by the microwave hydrothermal technique. H-ATP had a large specific surface area and enough active sites to capture CO2 molecules. The biochar not only reduced the spinel phase of waste LIBs into metal oxides including Co3O4 and TiO2 but also increased the separation and transmission of the carriers, thereby accelerating the adsorption and reduction of CO2. In addition, H-ATP/Co(Ti)Ox exhibited a localized surface plasmon resonance effect (LSPR) in the visible to near-infrared region and released high-energy hot electrons, enhancing the surface temperature of the catalyst and further improving the catalytic reduction of CO2 with a high CO yield of 14.7 μmol·g−1·h−1. The current work demonstrates the potential for CO2 reduction by taking advantage of natural mineral and spent batteries. [ABSTRACT FROM AUTHOR]

A ternary nanocomposite, BaTiO3–CNT/Ag, was synthesized via a coprecipitation method to function as a photocatalyst for pollutant degradation and H2 production through a water-splitting reaction. The successful preparation of the nanocomposite and the enhancement of its morphological properties were confirmed through Raman spectroscopy, X-ray diffraction/photoelectron spectroscopy (XRD/XPS), and scanning/transmission electron microscopy (SEM/TEM) studies. Utilizing transient photocurrent, photoluminescence (PL) spectroscopy, UV–visible diffuse reflectance spectroscopy (DRS), Mott–Schottky, and electrochemical impedance spectroscopy (EIS) tests, it was determined that the incorporation of carbon nanotube (CNT) and Ag into BaTiO3 led to a promotion of charge separation efficiency up to 15 times, a decrease in the bandgap energy from 3.12 to 2.85 eV, larger band bending, lower electron/hole recombination, and extensive lower internal resistance. In photodegradation-related studies, the response surface methodology (RSM) method was performed for experimental design to optimize the amounts of photocatalyst dosage, irradiation time, and initial dye concentration, yielding optimal values of 0.681 g/L, 67.5 min, and 1 mg/L, respectively. The sample showed outstanding photocatalytic efficiency in the degradation of different organic water pollutants, coupled with remarkable stability and reusability, as evidenced by a four-run cyclic experiment. Finally, the evaluation of H2 production revealed a remarkable amount of 542.4 μmol/g·h for the ternary nanocomposite, which is about 5 times higher than that of the pure BaTiO3 sample. This research provides thorough insight into the synthesis of a ternary nanocomposite that extremely enhances the charge transfer abilities and, therefore, boosts the photocatalytic H2 production and photodegradation of pollutants. [ABSTRACT FROM AUTHOR]

In this work, a multispectral aptasensor structure, including a sub-layer and two side walls, was presented. The cells are positioned at the down and top of the structure, with the down cells oriented perpendicular to the walls and the top cells aligned parallel to the walls. The validity of the findings was verified by the utilization of a numerical simulation technique known as 3D Finite Difference Time Domain (FDTD). The biosensor under consideration exhibits sensitivities of 1093.7 nm/RIU, 754 nm/RIU, and 707.43 nm/RIU in mode III, mode II, and mode I, respectively. In the majority of instances, the quantity of analyte available is insufficient to coat the surface of the sensor thoroughly. Consequently, in this study, the evaluation of surface sensitivity was undertaken alongside bulk sensitivity. The surface sensitivity of the suggested structure for mode II in the sensor layer, with thicknesses of 10, 20, 30, and 70 nm, is measured to be 25, 78, 344, and 717.636 nm/RIU, respectively. Our design incorporates a unique arrangement of sub-layer and side walls, with cells positioned to maximize interaction with the target analyte. This innovative configuration, combined with Ag for its superior plasmonic properties, enables the detection of E. coli O157 with remarkable sensitivity. [ABSTRACT FROM AUTHOR]

With the explosive growth of communication traffic, increasing the modulation bandwidth of semiconductor lasers has attracted significant attention. However, after rapid progress is achieved, further increasing the modulation bandwidth of semiconductor lasers is hampered by the slow charge‐carrier dynamics. Here, a room temperature, single‐mode perovskite nanolaser with sub‐picosecond pulses, enabled by high Purcell enhancement is reported. This enhancement is achieved via transferring an atomically smooth perovskite nanoplatelet onto the surface of an ultra‐smooth SiO2/Ag film. This nanolaser features a low mode volume (V) as low as 0.137 µm3, a high‐quality factor (Q) up to 2180, and a low lasing threshold of 36.65 µJ cm−2. The Q value of the laser is one order of magnitude higher than that of state‐of‐the‐art nanolasers. The smoothness of both the nanoplatelet and the SiO2/Ag film in the laser is critical to achieving a high Purcell enhancement. Polarization analysis reveals that the laser emission consists of a transvere‐magnetic (TM) polarized surface plasmon mode and a transverse‐electric (TE) polarized photonic mode. Furthermore, ultrafast charge‐carrier dynamics indicate the surface plasmon decay time can be as short as 0.6 ± 0.4 ps due to the high Purcell enhancement. This work opens up the possibility of developing nanolasers with high bandwidths and ultra‐small sizes. [ABSTRACT FROM AUTHOR]

We studied the effect of core-semiconductor radius, Au-shell thickness, graphene chemical potential, and graphene layers on the plasmonic resonance under quasi-static approximation. The core quantum dots used in the study are CdS, CdSe, ZnTe, and C u 2 O . The core-semiconductors are coated with Au and then wrapped with graphene. We compared the absorbance peaks position, the width of the absorbance peaks (FWHM), and the enhancement of the peak intensity of each core-bishell nanoparticles. We considered three fixed radii of the core semiconductors; r 1 = 20 , 30, and 35 nm. For each radius, the thickness of the Au varied from 1 to 15 nm, and μ varied from 1.0 to 1.6 eV. For all samples, the first resonance peaks are found in the visible region or in near-infrared region depending on the value of the chemical potential and the second peaks found in the infrared or near-infrared region. The effect of the graphene layers is also studied. From the four samples, C u 2 O @ A u @ g r a p h e n e has better absorbance/extinction cross-section, with relatively large values of d for each value of μ and r 1 . CdSAu@graphene has least absorption cross-section intensity that occurs relatively at small thickness of Au. The overall combined effect of the four parameters is enhanced absorption/extinction surface plasmon resonance peaks accompanied by blue shift of the graphene resonance. The obtained results can be used in medical applications that require sensitive imaging, therapy, and as a sensor. [ABSTRACT FROM AUTHOR]

Plasmonic nanoparticles exhibit dramatic changes in optical properties depending on their spatial organization. Therefore, the ability to precisely control their assembly structure is important for both fundamental understanding and practical applications. In this personal account, we describe a templated surfactant‐assisted seed‐growth method to synthesize core–shell‐type gold nanoparticle assemblies with controllable surface morphologies and optical properties. This approach provides a simple procedure for simultaneous growth and assembly of metal nanoparticles on polymer templates, producing well‐defined nanostructures such as spiky nanoshells and raspberry‐like metamolecules with useful and interesting optical properties, such as strong and uniform surface‐enhanced Raman scattering and metamaterial properties. We discuss the factors that control the morphology and collective properties, describe the design rules acquired from the system, and suggest future directions of this research area. [ABSTRACT FROM AUTHOR]

Abstract We report the deposition of single atom nickel catalyst on refractory plasmonic titanium nitride (TiN) nanomaterials supports using the wet synthesis method under visible light irradiation. TiN nanoparticles efficiently absorb visible light to generate photoexcited electrons and holes. Photoexcited electrons reduce nickel precursor to deposit Ni atoms on TiN nanoparticles’ surface. The generated hot holes are scavenged by the methanol. We studied the Ni deposition on TiN nanoparticles by varying light intensity, light exposure time, and metal precursor concentration. These studies confirmed the photodeposition method is driven by hot electrons and helped us to find optimum synthesis conditions for single atoms deposition. We characterized the nanocatalysts using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). We used density functional theory (DFT) calculations to predict favorable deposition sites and aggregation energy of Ni atoms on TiN. Surface defect sites of TiN are most favorable for single nickel atoms depositions. Interestingly, the oxygen sites on native surface oxide layer of TiN also exhibit strong binding with the single Ni atoms. Plasmon enhanced synthesis method can facilitate photodeposition of single atom catalysts on a wide class of metallic supports with plasmonic properties.