Localized Surface Plasmon Effect Research Articles

Zinc oxide nanorods electronically controlled terahertz modulator

AbstractMetal oxides are commonly employed in terahertz (THz) modulator devices operating in the THz frequency band. These metal oxides, which rely on electronic control, exhibit a clear response to THz waves. The modulation of THz waves is achieved by applying an electric field directly onto the surface of ZnO nanorods and their metal dopants. This external electric field has the capability to modulate both the phase and transmittance of the THz wave. The devices based on Au‐doped ZnO nanorods demonstrate a significant enhancement in modulation depth due to the incorporation of the localized surface plasmon effect. In the realm of active THz modulation, the velocity of electric modulation is enhanced while the required driving power is reduced. The primary focus of this research article is to present an analysis of the active modulation properties and the underlying principles of ZnO nanorods and their metallic dopants when subjected to an applied electric field. The modulation bandwidth range from 0.1 to 1.0 THz for our devices. The phase modulation of 0.866 rad and the transmittance modulation with the modulation depth of 0.4 was realized.

BiOI/AgI/Ag plasmonic heterostructure for efficient photoelectrochemical water splitting

BiOI-based photocathode has attracted much attention for photoelectrochemical (PEC) water splitting application. Here, we have designed a BiOI/AgI/Ag plasmonic heterostructure through a facile electrodeposition combined with ion-exchange and illumination approach. The work function difference between BiOI and AgI brings favorable interfacial band bending, and the Ag nanoparticle exhibits localized surface plasmonic effect to boost the carrier transfer. Thus, the BiOI/AgI/Ag photocathode achieves superior current density of −1.02 mA cm−2 at 0 V vs. RHE for 200 min, which is 50 times than that of pristine BiOI. These results pave a way for promising PEC water splitting using BiOI-based heterostructure photocathodes.

Electric- and magnetic-dipole surface lattice resonances in microwave regime

At optical frequencies, the collective excitation of the periodic array of metallic meta-molecules can support surface lattice resonances (SLRs) due to the coupling of localized surface-plasmon (LSP) resonances to Rayleigh anomaly diffraction. However, the LSP effect in metal blocks becomes negligible in the microwave region. Thus, how the SLRs behave in the microwave regime is very interesting. In this paper, a microwave metasurface consisting of periodic metallic cubes on an ultrathin dielectric substrate is investigated. Two high-Q transmission dips are found, which can be attributed, respectively, to electric-dipole SLRs (ED-SLRs) and magnetic-dipole SLRs (MD-SLRs), because of the non-resonant Rayleigh-like scattering of single cubes and diffraction coupling of the periodic array. The frequencies of both ED- and MD-SLRs are sensitive to the refractive index of the substrate, suggesting that the proposed metasurface may be used to measure the refractive index in the microwave range.

High Sensitivity Multiple Microcavity Enhanced 3-D Printed Micro-Stud Array Ultrafast Response Detector at 6G Frequency

The next generation of communication 6G technology in the terahertz band is crucial for the development of the future high-speed information society. How to achieve a highly sensitive response to low power density terahertz signals at room temperature has been one of the frontier research hot issues within this field. In addition, the reproducible line height of the device and its availability for mass production are also urgent issues to be addressed. Here, We have proposed a 6G detector based on combining the advantages of sub-wavelength micro-structures, 3D micro-cavity, and Weyl-semimetallic films. The localized surface plasmon (LSP) effect by the micro-stud array is used for the enhancement of the light-matter interaction. Also, the 3D structure leads to a micro-cavity allowing for a near enhancement of the interaction on a small scale. Furthermore, the 0-band gap of the Weyl-semimetal and the enhanced response to low-energy photon displacement currents near makes the Weyl-semimetal more suitable for detecting terahertz waves. In addition, the use of projection micro stereolithography 3D print technology combined with magnetron sputtering of thin films makes this terahertz detection technology solution reproducible, low cost, simple processing, and promising for industrial production, contributing to the development and diffusion of 6G technology.

Large Area Flexible Thin Layer Terahertz Detector

AbstractDue to the low photon energy in the relevant frequency band, fewer materials can directly excite carriers, and an extreme lack of high‐performance, large‐area detectors, limit the promotion, and development of 6G technology. In addition, flexible detectors with the integration of 6G communication and Internet of Things technology has good prospects for application in the development of optoelectronic devices, which are also urgently needed. A large‐area flexible thin layer terahertz detector is designed that combines the advantages of excellent optoelectronic performance in the detection of electromagnetic waves with low photon energy and the localized surface plasmon (LSP) effect in a sub‐wavelength structure detector. Due to the large effective area, the spiral electrode device demonstrates the best performance at room temperature. The noise equivalent power (NEP) and photoresponsivity (RV) are achieved with 0.4 pW Hz−1/2 and 154 MV W−1 at 0.28 THz. In addition, the bending experiments show that the device has extreme advantages for flexible 6G detector applications.

Rapid and Accurate On-Site Immunodiagnostics of Highly Contagious Severe Acute Respiratory Syndrome Coronavirus 2 Using Portable Surface-Enhanced Raman Scattering-Lateral Flow Assay Reader.

In early 2022, the number of people infected with the highly contagious mutant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), called Omicron, was increasing worldwide. Therefore, several countries approved the lateral flow assay (LFA) strip as a diagnostic method for confirming SARS-CoV-2 instead of reverse transcription-polymerase chain reaction (RT-PCR), which takes a long time to generate the results. However, owing to the limitation of detection sensitivity, commercial LFA strips have high false-negative diagnosis rates for patients with low virus concentrations. Therefore, in this study, we developed a portable surface-enhanced Raman scattering (SERS)-LFA reader based on localized surface plasmon effects to solve the sensitivity problem of the commercial LFA strip. We tested 54 clinical samples using this portable SERS-LFA reader, which generated 49 positive and 5 negative results. Out of the 49 positive results, SERS-LFA classified only 2 as false negative, while the commercial LFA classified 21 as false negative. This confirmed that the false-negative rate had significantly improved compared to that of commercial LFA strips. We believe that the proposed SERS-LFA system can be utilized as a point-of-care diagnostic system to quickly and accurately determine a virus infection that could spread significantly within a short period.

The Advanced Applications of 2D Materials in SERS

Surface-enhanced Raman scattering (SERS) as a label-free, non-contact, highly sensitive, and powerful technique has been widely applied in determining bio- and chemical molecules with fingerprint recognitions. 2-dimensional (2D) materials with layered structures, tunable optical properties, good chemical/physical stabilities, and strong charge–transfer interaction with molecules have attracted researchers’ interests. Two-D materials with a large and flat surface area, as well as good biocompatibility have been considered promising candidates in SERS and widely applied in chemical and bio-applications. It is well known that the noble metallic nanostructures with localized surface plasmon effects dominate the SERS performance. The combination of noble metallic nanostructure with 2D materials is becoming a new and attractive research domain. Until now, the SERS substrates combined with 2D materials, such as 2D graphene/metallic NPs, 2D materials@metallic core-shell structures, and metallic structure/2D materials/metallic structure are intensely studied. In this review, we introduce different kinds of fabrication strategies of 2D and 3D SERS substrates combing with 2D materials as well as their applications. We hope this review will help readers to figure out new ideas in designing and fabricating SERS substrates with high SERS performance that could enlarge the applicable domains of SERS.

Localized surface plasmon effect on 3-mercaptopropionic acid and citrate stabilized gold nanoparticles for biosensor application

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[Formula: see text]nm, while Au-Citrate has a plasmonic peak at 519[Formula: see text]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[Formula: see text]nm and 51[Formula: see text]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.

Role of an Inert Electrode Support in Plasmonic Electrocatalysis

Direct loading of plasmonic nanostructures onto catalytically inert conductive support materials leads to the Schottky barrier-free architecture of the photocatalytic system. Such systems have recently attracted the attention of the research community as they permit collection of hot carriers independent of their energy when additional charge separation strategies are used. However, a systematic mechanistic investigation and description of the contribution of an inert conductive support to plasmonic electrocatalysis is missing. Herein, we systematically investigated the effect of the supporting electrode material on the observed photoinduced enhancement by comparing the photoelectrocatalytic properties of AuNPs supported on highly oriented pyrolytic graphite (HOPG) and indium tin oxide (ITO) electrodes using electrocatalytic benzyl alcohol (BnOH) oxidation as a model system. Upon illumination, only ∼(3 ± 1)% enhancement in catalytic current was recorded on the AuNP/ITO electrodes in contrast to ∼(42 ± 6)% enhancement on AuNP/HOPG electrodes. Our results showed that the local heating due to light absorption by the electrode material itself independent of localized surface plasmon effects is the primary source of the observed significant photoinduced enhancement on the HOPG electrodes in comparison to the ITO electrodes. Moreover, we demonstrated that an increased interfacial charge transfer at elevated temperatures and not faster reactant diffusion as suggested previously is the main source of the thermal enhancement. This work highlights the importance of the systematic evaluation of contributions of all parts, even if they are catalytically inert, to the light-induced facilitation of catalytic reactions in plasmonic systems.

Photocatalytic Recovery of Gold from a Non-Cyanide Gold Plating Solution as Au Nanoparticle-Decorated Semiconductors.

In this work, a photocatalytic process was carried out to recover gold (Au) from the simulated non-cyanide plating bath solution. Effects of semiconductor types (TiO2, WO3, Nb2O3, CeO2, and Bi2O3), initial pH of the solution (3–10), and type of complexing agents (Na2S2O3 and Na2SO3) and their concentrations (1–4 mM each) on Au recovery were explored. Among all employed semiconductors, TiO2 exhibited the highest photocatalytic activity to recover Au from the simulated spent plating bath solution both in the absence and presence of complexing agents, in which Au was completely recovered within 15 min at a pH of 6.5. The presence of complexing agents remarkably affected the size of deposited Au on the TiO2 surface, the localized surface plasmon effect (LSPR) behavior, and the valence band (VB) edge position of the obtained Au/TiO2, without a significant change in the textural properties or the band gap energy. The photocatalytic activity of the obtained Au/TiO2 tested via two photocatalytic processes depended on the common reduction mechanism rather than the textural or optical properties. As a result, the Au/TiO2 NPs obtained from the proposed recovery process are recommended for use as a photocatalyst for the reactions occurring at the conduction band rather than at the valence band. Notably, they exhibited good stability after the fifth photocatalytic cycle for Au recovery from the actual cyanide plating bath solution.

Synthesis and Characterization of Silver-Gold Bimetallic Nanoparticles for Random Lasing

We developed rough silver-gold bimetallic nanoparticles for random lasing. Silver nanoparticles were synthesized based on a citrate-reduction method and the gold (III) chloride trihydrate was added to produce bimetallic nanoparticles. Gold atoms were deposited on the surface of the silver (Ag) through galvanic replacement reactions after the solution was stored at room temperature. Sample characterization and a spectrometry experiment were performed where bimetallic nanoparticles with nanogaps and the extinction of the nanoparticles were observed. The aim of this research is to synthesize nanoparticles for random dye laser in a weakly scattering regime. The novel bimetallic nanoparticles were added to Rhodamine 640 solution to produce random lasing. We found that random dye laser with bimetallic nanoparticles produced spectral narrowing and lasing threshold compared to random dye laser with silver nanoparticles. We attribute that to the localized surface plasmon effects which increase local electromagnetic field to provide sufficient optical gain for random lasing. The rough surface of bimetallic nanoparticles also contributes to the properties of random lasing. Thus, we suggest that the rough bimetallic nanoparticles can be used to develop random lasers.

Ag@SiO2-embedded InGaN/GaN nanorod array white light-emitting diode with perovskite nanocrystal films

White light-emitting diodes (LEDs) are great candidates for general lighting. Phosphors have commonly been used for the color conversion layers of white LEDs; however, they backscatter more than half of the down-converted light, which is lost within the device, thus degrading the overall performance. In this study, we propose and demonstrate white LEDs with improved efficiency enabled by the intimate integration of Ag@SiO2-supported blue InGaN/GaN nanorod LEDs together with green- and red-emitting perovskite nanocrystal (PNC) films as color conversion layers. The photoluminescence (PL) intensity of the blue LEDs (BLEDs) was significantly enhanced owing to the localized surface plasmon (LSP) effect of Ag@SiO2 nanoparticles. In addition, the perovskite PL intensity was improved by the high-power BLED backlight. The resulting PL intensity of the Ag@SiO2 nanoparticle-embedded nanorod white LED was 62% greater than that of a planar white LED.

Rh/Al Nanoantenna Photothermal Catalyst for Wide-Spectrum Solar-Driven CO2 Methanation with Nearly 100% Selectivity.

Solar-powered CO2 conversion represents a promising green and sustainable approach for achieving a carbon-neutral economy. However, the rational design of a wide-spectrum sunlight-driven catalysis system for effective CO2 reduction is an ongoing challenge. Herein, we report the preparation of a rhodium/aluminum (Rh/Al) nanoantenna photothermal catalyst that can utilize a broad range of sunlight (from ultraviolet to the near-infrared region) for highly efficient CO2 methanation, achieving a high CH4 selectivity of nearly 100% and an unprecedented CH4 productivity of 550 mmol·g-1·h-1 under concentrated simulated solar irradiation (11.3 W·cm-2). Detailed control experiment results verified that the CO2 methanation process was facilitated by the localized surface plasmonic resonance and nanoantenna effects of the Rh/Al nanostructure under light irradiation. In operando temperature-programmed Fourier transform infrared spectroscopy confirmed that CO2 methanation on the Rh/Al nanoantenna catalyst was a multistep reaction with CO as a key intermediate. The design of a wide-spectrum solar-driven photothermal catalyst provides a feasible strategy for boosting CO2-to-fuel conversion.

Localized surface plasmon resonance coupling with piezophototronic effect for enhancing hydrogen evolution reaction with Au@MoS2 nanoflowers

The hydrogen evolution rate of Au nanoparticles encapsulated by MoS 2 nanoflowers (Au@MoS 2 NFs) was dramatically increased through localized surface plasmon resonance (LSPR) coupling with the piezophototronic effect. The heterostructured Au@MoS 2 NFs had highly active reaction sites for intense piezoelectric polarization that established an electric field and a surface plasmon effect to play a crucial role in regulating interfacial charge migration. Simultaneous light irradiation and mechanical vibration applied to the Au@MoS 2 NFs increased the hydrogen evolution from 2981 μmol g −1 h −1 for the solely piezocatalytic process to 4808 μmol g −1 h −1 . The hydrogen evolution rate of the Au@MoS 2 NFs was 161% that of pristine MoS 2 NFs. The considerable performance improvement was attributed to piezoelectric generation of hot electrons through LSPR. Density functional theory and the finite element method were employed to simulate the charge transfer of the Au@MoS 2 NFs under simultaneous light irradiation and mechanical vibration. Greater mechanical strain on the heterostructured catalysts yielded a greater electric field, demonstrating the piezophototronic effect had strong synergy with LSPR and thus increasing the hydrogen evolution rate. The hydrogen evolution rate of Au nanoparticles encapsulated by MoS 2 nanoflowers (Au@MoS 2 NFs) was dramatically increased through localized surface plasmon resonance (LSPR) coupling with the piezophototronic effect. Simultaneous light irradiation and mechanical vibration applied to the Au@MoS 2 NFs increased the hydrogen evolution from 2981 μmol g −1 h −1 for the solely piezocatalytic process to 4808 μmol g −1 h −1 . • Heterostructured Au@MoS 2 nanoflower catalysts have highly active reaction sites. • Intense piezoelectric polarization built-in electric field coupled with localized surface plasmon (LSPR) effect. • The synergistic combination of LSPR and the piezophototronic effect yielded a considerable internal electric field. • Electric field regulating the interfacial charge migration to trigger electrochemical reactions.

Enhanced photoelectric performance in a CdO/ZnO/Ag heterostructure thin film photoanode

Abstract Hydrogen generation via solar water splitting using a semiconductor photo-electrode has been extensively explored owing to its contribution to the development of renewable energy. Although pure ZnO has many advantages, its wide band-gap limits its use in solar photoelectric applications. Recently, significant advancements have been made in the photoelectrochemical applications due to the development of multi-component heterostructures. In this study, CdO/ZnO/Ag heterostructure films are fabricated via pulsed laser deposition, and their structure, morphology, and photoelectric properties are intensively investigated. The results indicate that the CdO/ZnO/Ag heterostructure thin film exhibits a wide absorption range from ultraviolet to visible light and an enhanced absorption intensity. The photocurrent density of the heterostructure film reaches 0.25 μA/cm2, which is 4.2 times higher than that of pure ZnO film under visible light irradiation. The increased visible light photocurrent response is mainly attributed to the localized surface plasmon effect of Ag nanoparticles. The band structure of CdO/ZnO promotes the transfer of electrons to CdO, which decreases the recombination of electron-hole pairs at the CdO/ZnO interface and increases the photocurrent. A possible mechanism is proposed here to interpret the enhancement of the photoelectric response.

Ag Nanowire-Plasmonic-Assisted Charge Separation in Hybrid Heterojunctions of Ppy-PEDOT:PSS/GaN Nanorods for Enhanced UV Photodetection.

The surface states, poor carrier life, and other native defects in GaN nanorods (NRs) limit their utilization in high-speed and large-gain ultraviolet (UV) photodetection applications. Making a hybrid structure is one of the finest strategies to overcome such impediments. In this work, a polypyrrole (Ppy)-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)/GaN NRs hybrid structure is introduced for self-powered UV photodetection applications. This hybrid structure yields high photodetection performance, while pristine GaN NRs showed negligible photodetection properties. The ability of the photodetector is further boosted by functionalizing the hybrid structure with Ag nanowires (NWs). The Ag NWs-functionalized hybrid structure exhibited a responsivity of 3.1 × 103 (A/W), detectivity of 3.19 × 1014 Jones, and external quantum efficiency of 1.06 × 106 (%) under a UV illumination of λ = 382 nm. This high photoresponse is due to the huge photon absorption rising from the localized surface plasmonic effect of a Ag NWs network. Also, the Ag NWs significantly improved the rising and falling times, which were noted to be 0.20 and 0.21 s, respectively. The model band diagram was proposed with the assistance of X-ray photoelectron spectroscopy to explore the origin of the superior performance of the Ag NWs-decorated Ppy-PEDOT:PSS/GaN NRs photodetector. The proposed hybrid structure seems to be a promising candidate for the development of high-performance UV photodetectors.

Design and verification of a temperature-sensitive broadband metamaterial absorber based on VO2 film

Abstract Devices based on tunable metamaterials can be used in many fields. A tunable metamaterial absorber is designed and measured based on vanadium dioxide (VO2) film. An absorption band is obtained based on superposition effect of localized surface plasmon (LSP) modes. In experiments, this absorption band can be strengthened by optimizing structural parameters radius and thickness, which are consistent with resonance properties exhibited by an LC equivalent circuit of proposed unit cells. High absorption performance can still obtain when the incident angle reaches 60°. Moreover, the absorption performance of samples can be adjusted by changing the ambient temperature in further experiments. When temperature reaches and exceeds the phase transition point, the VO2 layer exhibits an insulation-metal phase transition phenomenon, resulting in the enhancement of the absorption band.

Ambipolar Plasmon‐Enhanced Photodetector Built on Germanium Nanodots Array/Graphene Hybrid

AbstractGraphene with gate‐tunable electronic properties is promising as the channel materials in ambipolar multifunctional photodetectors. However, owing to the zero bandgap and weak light absorption, photodetectors fabricated on pristine graphene have low photoresponsivity. Herein, an ambipolar multifunctional photodetector with improved photocurrent and response speed is constructed on germanium (Ge) nanodots array‐decorated graphene. The photocurrent map and simulated electric field distributions reveal that the enhanced photo‐response is attributed to the localized surface plasmonic resonance effects by trapping light around the Ge nanodots. The photodetector exhibits ambipolar photo‐response and the photocurrents can be tuned from negative to positive by applying different gate voltages due to the gate‐tunable Fermi level of graphene. This ambipolar photodetector with fast response has excellent potential in imaging and sensing arrays as well as multifunctional photodetectors.

SERS imaging-based aptasensor for ultrasensitive and reproducible detection of influenza virus A

Surface-enhanced Raman scattering (SERS)-based aptasensors display high sensitivity for influenza A/H1N1 virus detection but improved signal reproducibility is required. Therefore, in this study, we fabricated a three-dimensional (3D) nano-popcorn plasmonic substrate using the surface energy difference between a perfluorodecanethiol (PFDT) spacer and the Au layer. This energy difference led to Au nanoparticle self-assembly; neighboring nanoparticles then created multiple hotspots on the substrate. The localized surface plasmon effects at the hot spots dramatically enhanced the incident field. Quantitative evaluation of A/H1N1 virus was achieved using the decrease of Raman peak intensity resulting from the release of Cy3-labeled aptamer DNAs from nano-popcorn substrate surfaces via the interaction between the aptamer DNA and A/H1N1 virus. The use of a Raman imaging technique involving the fast mapping of all pixel points enabled the reproducible quantification of A/H1N1 virus on nano-popcorn substrates. Average ensemble effects obtained by averaging all randomly distributed hot spots mapped on the substrate made it possible to reliably quantify target viruses. The SERS-based imaging aptasensor platform proposed in this work overcomes the issues inherent in conventional approaches (the time-consuming and labor-intensiveness of RT-PCR and low sensitivity and quantitative analysis limits of lateral flow assay kits). Our SERS-based assay for detecting A/H1N1 virus had an estimated limit of detection of 97 PFU mL−1 (approximately three orders of magnitude more sensitive than that determined by the enzyme-linked immunosorbent assay) and the approximate assay time was estimated to be 20 min. Thus, this approach provides an ultrasensitive, reliable platform for detecting viral pathogens.

Electronic Detection of Photonic Band Gaps in Nanolithographic Metallic Gratings

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