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We report a theoretical study of plasmon generation of a giant electromagnetic field in a supernarrow nanoslit formed by a silver cylinder and a flat mirror surface. It is shown that as the silver surfaces approach each other, gap plasmons are excited in the gap between them, which results in a resonant amplification of the field. It is demonstrated for the first time that the electric field amplification increases with decreasing distance between the cylindrical and flat surfaces and reaches saturation, at which the field intensity becomes record high, exceeding the incident wave intensity by ten orders of magnitude. The found gap plasmon modes will increase the sensitivity to the detection of small concentrations of molecules, down to single molecules, by the methods of giant Raman scattering of light and plasmon-enhanced IR spectroscopy.

Gold nanoparticles (Au-NPs) are readily used nanoparticles which finds applications in fields like biosensors, drug delivery, optical bioimaging and many state of art systems used for detection. In the recent years fiber optic sensors have seen utilization of Au-NPs along with other nanoparticles for implementation of sensors for sensing various biomolecules like cholesterol, glucose, and uric acid. The cancer cells, creatinine and bacteria can also be detected with the fiber optic sensors. Given the significance of Au-NPs in fiber optic sensors, the current work is a review of the synthesis, the common methods used for characterization, and the applications of Au-NPs. It is important to discuss and analyse the work reported in the literature to understand the trend and gaps in developing plasmonic optical fiber sensors.

This paper presents a novel dual-polarized refractive index sensor based on D-shaped photonic crystal fiber. Unlike the traditional D-shaped structures, we use a micro-opening of the deposited gold film as microfluidic channel to excite the surface plasmon resonance (SPR) mode. The fiber consists of two layers of circular pores arranged in an octagonal lattice structure. By optimizing the structural parameters of the fiber, the proposed sensor detection range: the refractive index of the analyte changes from 1.26 to 1.36. Numerical simulation based on the finite element method shows that the average sensitivities in the x- and y- polarization modes are 1182 nm RIU−1 and 5736 nm RIU−1, respectively. When the refractive index of the analyte to be measured is 1.36, the highest sensitivity of the x and y polarization directions is 1298 nm RIU−1 and 11 039 nm RIU−1, respectively. Among them, the resonance wavelength and the resonance intensity increase with the refractive index of the sample to be tested. In addition, we further analyzed the effects of microfluidic channel size, deposited gold film thickness, sensing region length and the overall structure of the fiber (polishing depth, inner cladding pore size, etc) on sensor transmission characteristics.

The photonic spin Hall effect (SHE), featured by a spin-dependent transverse shift of left- and right-handed circularly polarized light, holds great potential for applications in optical sensors, precise metrology and nanophotonic devices. In this paper, we present the significant enhancement of photonic SHE in the terahertz range by considering the InSb-supported long-range surface plasmon resonance (LRSPR) effect. The influences of the InSb/ENZ layer thickness and temperature on the photonic SHE were investigated. With the optimal structural parameters and temperature, the maximal spin shift of the horizontal polarization light can reach up to 2.68 mm. Moreover, the spin shift is very sensitive to the refractive index change of gas, and thus a terahertz gas sensing device with a superior intensity sensitivity of 2.5 × 105 μm/RIU is proposed. These findings provide an effective method to enhance the photonic SHE in the terahertz range and therefore offer the opportunity for developing the terahertz optical sensors based on photonic SHE.

A high sensitivity plasmonic temperature sensor based on a side-polished photonic crystal fiber is proposed in this work. In order to achieve high sensitivity and high stability, the gold layer is coated on the side-polished photonic crystal fiber to support surface plasmon resonance. The mixture of ethanol and chloroform is used as the thermosensitive liquid. The performances of the proposed temperature sensor were investigated by the finite element method (FEM). Simulation results indicate that the sensitivity of the temperature sensor is as high as 7.82 nm/°C. It has good linearity (R 2 = 0.99803), the resolution of 1.1 × 10−3 °C, and the amplitude sensitivity of 0.1008 °C−1. In addition, the sizes of the small air hole and polishing depth have little influence on the sensitivity. Therefore, the proposed sensor shows a high structure tolerance. The excellent performance and high structure tolerance of the sensor make it an appropriate choice for temperature measurement.

Ag/ZnO composite nanostructures are produced by combined laser and ion implantation techniques. The ZnO layers are grown on SiO2 (001) and Al2O3 (r-cut) substrates by pulsed laser deposition (PLD) in vacuum and in oxygen ambient using a third-harmonic Nd:YAG laser. The ion implantation allows the introduction of Ag nanoparticles (NPs) in the surface of the ZnO matrix. These NPs are incorporated into the ZnO matrices to fabricate metal-semiconductor nanocomposites with the aim of manipulating their functionalities, exploiting the characteristics of both the matrix and the metal NPs. The composite samples are modified by laser annealing at 355 nm and 532 nm. The changes are investigated in the plasmon resonance absorption of the nanostructures before and after the annealing. The influence is explored of the different substrates used and the deposition conditions of ZnO growth on the properties of Ag/ZnO. The nanostructures obtained are efficient as SERS substrates for detection of ammonium nitrate under laser excitation at 633 nm. The SERS enhancement is attributed to the synergistic interactions between the plasmonic coupling among the surface embedded AgNPs and the enhanced charge transfer properties of the ZnO.

The multifunctional upconversion nanoparticles (UCNPs) are fascinating tool for biological applications. In the present work, photon upconverting NaGdF4:Yb,Er and Ag nanoparticles decorated NaGdF4:Yb,Er (NaGdF4:Yb,Er@Ag) nanoparticles were prepared using a simple polyol process. Rietveld refinement was performed for detailed crystal structural and phase fraction analysis. The morphology of the NaGdF4:Yb,Er@Ag was examined using high-resolution transmission electron microscope, which reveals silver nanoparticles of 8 nm in size were decorated over spherical shaped NaGdF4:Yb,Er nanoparticles with a mean particle size of 90 nm. The chemical compositions were confirmed by EDAX and inductively coupled plasma-optical emission spectrometry analyses. The upconversion luminescence (UCL) of NaGdF4:Yb,Er at 980 nm excitation showed an intense red emission. After incorporating the silver nanoparticles, the UCL intensity decreased due to weak scattering and surface plasmon resonance effect. The VSM magnetic measurement indicates both the UCNPs possess paramagnetic behaviour. The NaGdF4:Yb,Er@Ag showed computed tomography imaging. Magnetic resonance imaging study exhibited better T1 weighted relaxivity in the NaGdF4:Yb,Er than the commercial Gd-DOTA. For the first time, the optical trapping was successfully demonstrated for the upconversion NaGdF4:Yb,Er nanoparticle at near-infrared 980 nm light using an optical tweezer setup. The optically trapped UCNP possessing paramagnetic property exhibited a good optical trapping stiffness. The UCL of trapped single UCNP is recorded to explore the effect of the silver nanoparticles. The multifunctional properties for the NaGdF4:Yb,Er@Ag nanoparticle are demonstrated.

A high-sensitivity three-core photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) is proposed in this paper. The gold film is selected as the plasmonic metal and coated on the outside surface of the PCF to excite the SPR phenomenon. There are three different diameter air holes of d1, d2, and d3 distributed on the cross-section of the sensor. Among them, sensor performance can be affected by changing the diameter of the central hole and the thickness of the gold film. The sensor shows the maximum confinement loss value and spectral sensitivity of 50 dB cm−1 and 30600 nm RIU−1, respectively, at analyte RI (na = 1.41), and the corresponding maximum resolution is 3.27 × 10–6. The above simulation result shows that the sensor has excellent performance, thus laying the foundation for future research.

Indium–tin–oxide (ITO) is a material having metallic behavior in the infra-red spectral range. Its electrical and optical properties are also easily tuned, making it a suitable alternative plasmonic material in the infra-red region. In this work, electrical and optical simulation modeling was performed to study the effect of trap densities in different carrier scattering mechanisms on the mobility in ITO. This study correlates the micro-structural and opto-electronic parameters to the surface plasmon resonance (SPR) behavior in the ITO thin films. The results indicate that low defect density with high carrier concentration can provide better SPR performance in ITO.

The angular Goos-Hanchen shift dependence on the subwavelength grating parameters and the incident Gaussian beam width is investigated theoretically. High sensitivity of the angular Goos-Hanchen shift to the incident angle of a light beam near the surface plasmon resonance is demonstrated. Splitting of the reflected beam into two angularly separated beams is shown for strongly focused beam incident at the surface plasmon resonance angle.

This article theoretically considers surface plasmon resonance in composite structures. The features of the surface plasmon resonance arising at the interface with media containing nanoparticles from a high-temperature superconductor are investigated. The dielectric constant of spherical superconducting inclusions is considered taking into account Gorter-Casimir two-fluid model. The temperature dependence of the electrodynamic parameters of the superconductor is taken into account. The two-fluid model, the dependence of the concentration of non-superconducting electrons in a superconductor is often used as the fourth power of temperature nn~T4. In this work, a phenomenological model is used, according to which the electron concentration of non-superconducting electrons in a superconductor is determined by the formula nn~Tγ with γ=1.3÷2. This model is in good agreement with experimental data for high-temperature ceramic superconductors. The dispersion characteristics of surface plasmons arising in a planar structure with a thin nanocomposite superconductor layer are investigated. It is shown that the dispersion characteristics depend significantly on temperature.

Ag/SiO2 and Au/SiO2 samples were prepared by separately implanting 30 keV Ag and Au ions into 0.5-mm-thick SiO2 slabs at a fluence of 6 × 1016 ion·cm−2, and their optical and structural properties were studied in detail by using a fiber spectrometer and a transmission electron microscope, respectively. Our results showed that the two samples featured by their respective nanocomposite surface layers were asymmetrical in structure, and hence, their characteristic signals in the reflectance spectra excited by the lights incident from the rear surfaces were able to exhibit corresponding blueshifts when the overlays on the implanted surfaces were increased in refractive index with respect to air. Our results also showed that each of characteristic signals was strongly dependent on the localized surface plasmon resonance (LSPR) behavior of the involved Ag or Au nanoparticles (NPs), and it could not appear at a wavelength position smaller than or equal to that of the LSPR absorption peak since the involved Ag or Au NPs were quite small in size. These results meant that the two samples could be regarded as the LSPR sensors with a negative refractive index sensitivity (RIS), although their sensing abilities would lose when the overlays were very large in refractive index. Especially, the two samples were demonstrated to be relatively high in stability because the involved Ag and Au NPs were closely hugged and chemically protected by the matrices of SiO2, and consequently, they could have a chance to become prospective sensing devices in some special fields as long as their RISs and linearities could be improved in the future. The above findings substantially confirmed that the metal ion implantation into transparent dielectric slab was an effective route to the high-stability LSPR sensors.

The optical properties of graphene in monolayer and bilayer structure is essential for the development of optical devices viz. surface plasmon resonance based bio-sensors. The band structure of the twisted bilayer graphene (T-BLG) is remarkably different than the normal AA or AB stacking. This provides an opportunity to control the optical and electrical properties of BLG by applying an in-plane twist to one of the layer relative to other in a BLG system. Here, we calculated the refractive index (RI) of AA and AB stacking of BLG system using density functional theory. Though the spectrum for AA stacking shows some similarity with that of monolayer graphene, the spectrum for AB stacking was found to be remarkably different. The spectrum of AB stacked layer is red-shifted and the absorption peaks in low energy regime increases nearly by 3-folds. A large dependency of the twist angle on RI of twisted BLG were found. Based on the calculation, a schematic of phase diagram showing material behavior of such twisted BLG systems as a function of twist angle and photon energy was constructed. The twisted AA stacked BLG shows largely dielectric behavior whereas the twisted AB stacked BLG shows predominately semimetallic and semiconducting behavior. This study presents a refractive index landscape of twisted BLG dependent on important parameters viz. photon energy and inplane relative twist angle. Our studies will be very useful for the design and development of optical devices employing BLG systems particularly surface plasmon resonance based bio-sensors which essentially measures change in refractive index due to adsorption of analytes.

A Cd-doped ZnO nano-composite (Cd:ZnO) was synthesized using wet chemistry, and then incorporated into the photo-active layer of a thin film organic solar cell (TFOSC) to assist photon harvesting. The nano-composite (NC) formed different sized nano-structures that are beneficial to optical absorption and charge transport processes in the TFOSC. The effects on the NC were studied using a solar absorber medium composed of a poly(3-hexylthiophene) (P3HT) and 6-6-phenyl-C61-butyric acid methyl ester (PCBM) blend with standard device architecture: ITO/PEDOT:PSS/P3HT:PCBM/LiF/Al. The electrical and optical properties of the photoactive films were investigated at various doping levels of Cd:ZnO NC in the medium. The composite showed interesting local surface plasmon resonance, which significantly impacted on the performance of the cells. Consequently, the power conversion efficiency of the TFOSC grew by 84% compared to the reference cell. It is also noted that Cd:ZnO is environmentally stable and compatible for solution device processing.

The properties of MXenes, new generation of 2D materials, are determined by the surface terminations, which depends on flake preparation method. Changing the surface termination chemical groups can significantly modify the MXene flake properties and functionality. However, the common methods of MXene flake surface chemistry tuning require high-energy treatments and often lead to flake damage. In this work, we propose a plasmon-assisted chemical transformation for tuning the surface chemistry and termination of MXene flakes. The plasmon resonance was directly excited on MXene flakes and induced the generation of highly reactive radicals from electrostatically absorbed iodonium salt cations, leading to immediate grafting of the created radicals to the flake edges and basal planes. We used bis-CF3-substituted iodonium salts, and subsequent analysis of the Ti3C2Tx MXene flake surface composition indicated decreases in the total oxygen concentration and oxidized titanium with a simultaneous increase in the fluorine surface concentration, which was related to –C6H3(CF3)2 moiety attachment. The ability to substitute the hydrophilic oxygen-containing groups with hydrophobic and oleophilic –CF3 groups containing functional groups allows us to create a stable suspension of a MXene in nonpolar organic solvents and prepare a superhydrophobic, water-repellent and oxidation-stable conductive MXene coating.

The SARS-CoV-2 i.e., the novel severe acute respiratory syndrome corona virus; has caused massive loss of life. Mitigating this pandemic requires rapid inexpensive technologies for testing COVID-19. Optical sensors can be used to detect the Covid-19 virus by the surface Plasmon resonance phenomenon. Surface plasmon resonance sensors have good sensitivity, response times, fine resolution, and limits of detection. This paper, provides a brief overview on the COVID-19 effects, currently used testing technology, and potential of surface plasmon resonance optical sensors use for detecting this virus.

Aflatoxin is regarded as the potent carcinogenic agent which is secreted from fungi and present in some food products. So far, many detection methods have been developed to determine the trace amounts of aflatoxin in foods. In the present study a colorimetric competitive assay for detection of aflatoxin B1 (AFB1) has been developed based on interaction of gelatin functionalized gold nanoparticles (AuNPs@gelatin) in specific enzymatic reaction. Bacterial supernatant containing gelatinase enzyme were used as the substrate that could digest the coated gelatin on the surface of AuNPs and following in the presence of NaCl medium ingredient resulted to color change of AuNPs colloidal solution from red to purple. It was observed that with addition of aflatoxin to the bacterial supernatant, aflatoxin could interfere in aggregation of AuNPs and inhibited the process which subsequently prevent the expected color change induced by AuNPs aggregation. The supernatant containing AuNPs were investigated to analyze their induced surface plasmon resonance spectra through UV-Visible spectroscopy. The absorption values were directly proportional with the applied AFB1 concentration. The experiment conditions including incubation time, AuNPs concentration and pH were investigated. The obtained results showed that through this approach we could detect the AFB1 in a linear range from 10 to 140 pg/mL, with detection limit of 4 pg/mL. Real sample assay in saffron samples showed recoveries percentage of 92.4-93.5%. The applied approach proposed simple, cost effective and specific method for detection of AFB1 toxin in food samples.

Development of simple and accurate methods for the detection of As3+is highly desirable and technically important. In this work, a highly sensitive and selective long-period fiber gratings sensor based on surface plasmon resonance (LPFG-SPR) was developed for As3+detection by designing glutathione-functionalized Au nanoparticles as a signal amplification tag. Based on the chemical interaction between As3+and glutathione, the self-assembling glutathione on the surface of the gold film combines selectively with As3+, and then anchors the glutathione-functionalized Au nanoparticles, which changes the refractive index of the surrounding environment, resulting in a shift of the transmission spectrum. Results show that the sensor could detect As3+with concentrations ranging from 0.02 ppb to 2 ppb. The sensor exhibited excellent specificity for As3+against other metal ions, such as Na+, K+, Fe3+, Mg2+, Cu2+, Pb2+, Ni2+, Ba2+, Ca2+, and Co3+. The fiber sensor was successfully employed to detect As3+in pond water samples, demonstrating that it has the potential for As3+detection with the advantages of low cost, high sensitivity, and a simple structure.

The studies of Surface Plasmon Resonance SPR have focused on novel materials (gold and silver ). In this paper, four kinds of samples have been prepared also the system of plasmonic imaging with objective lens to excite the SPR our samples. The hot spot images for our different samples proved that the blue wavelength (405nm) can be excite the SPRs better than the green wavelength (532nm) for silver samples and the green wavelength can be excite the SPRs better than the blue wavelength for gold samples, also the increasing in consternation of AgNWs due to increasing in width of Gaussian hot spot.

We numerically demonstrate an ultraviolet graphene ultranarrow absorption in a hybrid graphene-metal structure. The full-width at half maximum of the absorption band being 9 nm in ultraviolet range is achieved based on the coupling of lattice plasmon resonances of the metallic nanostructure to the optical dissipation of graphene. The position, absorbance and linewidth of the hybridized narrow resonant mode tuned by controlling geometrical parameters and materials are systematically investigated. The proposed structure possesses high refractive index sensitivity of 288 nm/RIU and figure of merit of 72, and can also be used to detect small molecules layer of sub-nanometer thickness and refractive index with small changes, providing promising applications in ultra-compact efficient biosensors.

A dual D-type photonic crystal fiber (PCF) was proposed in this work to measure the refractive index and temperature of seawater. Two golden layers were designed to be coated on the two polished planes in the dual D-type PCF. Two confinement loss peaks in the transmission spectrum appeared due to the surface plasmon resonances which were inspired on the two golden layers. In order to achieve two-parameter sensing, one of the two polished planes was further coated with a polydimethylsiloxane (PDMS) layer which was temperature-sensitive. Seawater was assumed to be coated on the outer surface of the PCF. Numerical results by using the finite element method showed that the measurement sensitivity of the refractive index of seawater reached 1371 and 1228 nm/RIU, while the measurement sensitivity of temperature reached −0.3 and −1.06 nm/ °C, respectively. Finally, we obtained the transfer matrix expression which could be used to measure the refractive index and temperature of seawater simultaneously. The designed dual D-type PCF, which is simple in structure, highly sensitive and two-parameter measuring, could be a promising candidate for the monitoring of seawater.

In this work, a single fiber optic fiber was developed as a water pollution sensor based on the Surface Plasmon Resonance Phenomenon based upon the Mach - Zehender Interferometry (MZI) technology. The sensor submitted was developed to detect water pollutants. The SPR sensors were prepared by coating a golden metallic film which thickness 42 nm on a chemically etched single-mode fiber with a thickness of 20 micrometers, which achieved the best results of sensitivity to water pollution, the results of the high sensitivity of the optical fiber sensor were obtained based on the surface plasmon resonance phenomenon. The experimental results showed high sensitivity, reaching 1315 pm/mol.l−1 for a salty solution with distilled water, 1705 pm/mol.l−1 for the salty solution with tap water, as well as 2222 pm/mol.l−1 for sugar solution with distilled water, and 1925 pm/mol.l−1 for sugar solution with tap water. This means that these sensors which are based on SPR could be very useful in the field of water pollution detection.

This study aims to synthesize silver nanoparticles using leaf extract of Graptophyllum pictum and to characterize their properties, starting from localized surface plasmon resonance, functional groups and the particle size distribution, to their antibacterial activity. The measurement of the wavelength of localized surface plasmon resonance was conducted using UV-VIS spectroscopy, while FTIR spectroscopy was used to identify the chemical bonds of organic compounds in the particle. The particle size distribution was analyzed using TEM. The spectrophotometric method was used to assess the antimicrobial properties of the particles against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli. For this purpose, OD-620 of the bacterial sample was compared to OD-620 of the bacterial sample mixed with the silver nanoparticles, where the data was taken in 24 hours. The wavelength of localized surface plasmon resonance was found to be 455 nm, while FTIR spectrum showed the chemical bonds of organic compounds, denoting the presence of the extract on the particle. The particles were mostly spherical with diameters varying from 5.4 nm to 50.6 nm and the mean diameter was found to be 21.5±9.9 nm. The results from the antimicrobial assessment show that Graptophyllum pictum silver nanoparticles inhibit the growth of both S. aureus and E. coli, where during 24 hours of observation time, the particles affected E. coli, faster than the particles affected S. aureus.

Localized surface plasmon has been extensively studied and used for the photocatalysis of various chemical reactions. However, the different contributions between plasmon resonance and interband transition in photocatalysis has not been well understood. Here, we study the photothermal and hot electrons effects for crystal transformation by combining controlled experiments with numerical simulations. By photo-excitation of NaYF4 : Eu3+ @Au composite structure, it is found that the plasmonic catalysis is much superior to that of interband transition in the experiments, owing to the hot electrons generated by plasmon decay more energetic to facilitate the reaction. We emphasize that the energy level of hot electrons plays an essential role for improving the photocatalytic activity. The results provide guidelines for improving the efficiency of plasmonic catalysis in future experimental design.

Branched AuNPs usually have two or more local surface plasmon resonance (LSPR) absorption bands due to their structural anisotropy, and the LSPR performance is more sensitive to the changes of environmental refractive index than that of spherical AuNPs. The design and preparation of branched AuNPs as colorimetric probes is expected to improve the selectivity and sensitivity of detection of targets. In this paper, branched AuNPs were innovatively synthesized via hyperbranched polyethylenimine (HPEI) fabricated and capped AuNPs as seeds and cetyltrimethylammonium bromide (CTAB) as template agent. The branched AuNPs were characterized by TEM, DLS, zeta potentials and UV-Vis spectra. Using the branched AuNPs as colorimetric probe, the detection system for Hg2+ and Ag+ showed bright color changes from blue to orange and blue to green based on the morphological evolution of branched AuNPs. The branched AuNPs could selectively detect Hg2+ and Ag+ at concentrations as low as 77 and 140 nM, respectively. Moreover, this unusual colorimetric method has been successfully used in real water samples and has great potential as a simple, rapid, sensitive and selective method for the detection of Hg2+ and Ag+.

A dual-polarized photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR) was proposed to measure the refractive index (RI) of liquids. The gold film and liquid analyte were successively wrapped on the outer surface of PCF to stimulate the external SPR effect, which greatly reduced the manufacturing difficulties contrast to depositing gold film and filling liquid analyte in the inner air holes of PCF. The performance of the proposed PCF sensor was numerically investigated by the finite element method (FEM). The results show that the proposed PCF sensor can realize dual-polarized detection in the RI range of 1.36-1.42. The x and y polarization (X-P and Y-P) core modes coupled to X-P 2nd-order and Y-P 1st-order surface plasmon polariton (SPP) modes, respectively. As the RI of analyte increased, the wavelength sensitivity increased and therefore a maximum value of 15900 nm/RIU in X-P and 16900 nm/RIU in Y-P were achieved. Correspondingly, we obtained a maximum amplitude sensitivity of 2026.05 RIU-1 in X-P and 2102.65 RIU-1 in Y-P. What's more, the fabrication tolerance of the proposed PCF was up to ±0.4 μm, which made the proposed PCF a favorable candidate in the detection of liquids.

Silver conjugated Tetracycline, was created and characterized by ultraviolet visible spectrophotometry (UV-vis), Fourier transform infrared (FT-IR), X-Ray Diffraction Patterns (XRD). Using antibacterial assays, the effects of tetracycline alone and drugs-conjugated with silver nanoparticles were tested against Gram-ve Pseudomonas aeruginosa isolates by well diffusion assay. The UV-vis spectra of silver-drug Nano conjugates showed a characteristic surface Plasmon resonance band in the range of 400–450 nm. FTIR analysis demonstrated the involvement of Hydroxyl groups in both drugs in the stabilization of silver nanoparticles. (XRD) showed that they cubic structure of silver and, antibacterial assays showed that biosynthesis silver nanoparticle conjugation enhanced antibacterial potential of Tetracycline compared with drug alone.

The surface plasmon resonance of gold nanoparticles in a polycrystalline energy-related material – pentaerythritol tetranitrate (PETN) – has been observed for the first time. The extinction spectra of this material are recorded, and its absorption characteristics are determined by the photoacoustic method using pulsed laser irradiation. Using the data obtained, it is concluded that gold nanoparticles are promising inclusions in explosive materials when designing an optical detonator.

We have shown experimentally that the effect of cw UV radiation and pulsed UV radiation from a nanosecond laser as well as thermal treatment of glasses with europium, silver and cerium ions (photosensitizer) allow the local formation of the areas in glass, having different luminescence colour or the areas of different colouration. These effects are caused by a change in the charge state of molecular clusters and the formation of silver nanoparticles possessing plasmon resonance in glass. This allows recording of multicolour optical information by means of a focused beam from a UV laser, both near the glass surface and within its volume. We have revealed the influence of chlorine on the formation and properties of silver nanoparticles in glass in the course of thermal treatment following the laser impact.

In this paper, four SPR sensors have been proposed and analyzed theoretically. The proposed SPR sensors are prism—Au-Ag alloy—CH3NH3PbI3—Au-Ag alloy—graphene—sensing medium, prism—Au-Al alloy—CH3NH3PbI3—Au-Al alloy—graphene—sensing medium, prism—CH3NH3PbI3—Au-Ag alloy—CH3NH3PbI3—graphene—sensing medium and prism—CH3NH3PbI3—Au-Al alloy—CH3NH3PbI3—graphene—sensing medium. Matrix method for N-layer model has been utilized to analysis the performance parameters of the proposed sensors. The performance parameters were determined in terms of the detection accuracy (DA), sensitivity, and figure of Merit (FoM). The thicknesses of bimetallic alloy and CH3NH3PbI3 layers and bimetallic alloy composition have been optimized to achieve the best performance of the sensors. It is found that the best detection accuracy, sensitivity and figure of Merit of the proposed sensors are 0.279 deg−1, 85.2 deg/RIU and 23.79 RIU−1 for configuration I; 0.414 deg−1, 77.2 deg/RIU and 32.03 RIU−1 for configuration II; 0.120 deg−1, 106.60 deg/RIU and 12.81 RIU−1 for configuration III; and 0.186 deg−1, 93 deg/RIU and 17.35 RIU−1 for configuration IV.

Graphene surface plasmons have gained wide interest due to their promising applications in terahertz technology. In this paper, we propose an easily implemented monolayer graphene structure, and exploit its quadra resonance mode to achieve triple plasmon-induced transparency (PIT) and triple plasmon-induced absorption (PIA) effects. A uniform theoretical model with four resonators is introduced to elaborate the intrinsic coupling mechanism and examine the accuracy of simulated results. By altering the Fermi energy and the carrier mobility of the graphene, the proposed triple PIT (PIA) system exhibits a dynamically tunable property, and the absorption intensity can be controlled over a broadband frequency range. It is found that the absorption intensity of the triple PIA spectrum can be as high as 50% with four absorption bands, which is 20 times more than that of monolayer graphene. Besides, we further investigate the triple PIT system for terahertz plasmonic sensing applications, and it is shown that the highest sensitivity of 0.4 THz RIU−1 is reached. Thus, the triple PIT system we propose can be employed for multi-band light absorption and plasmonic optical sensing.

We report enhancement of the transverse magneto-optic Kerr effect (TMOKE) in Au/Fe/Au trilayers for improving the refractive index (RI) sensitivity in surface plasmon resonance sensors by magnetic modulation. The thicknesses of the upper Au layer, the Fe layer and the lower Au layer with required thickness resolution were theoretically optimized to maximize the TMOKE intensity with perfect momentum matching, and 3% TMOKE intensity was obtained in a trilayer. Furthermore, a wedge-shaped Au thin film was fabricated on a glass substrate, and the incident angle showing minimum reflectivity was modulated, corresponding to a difference in momentum matching. Resolution of the metal layer thickness (0.26 nm) was demonstrated in a single sensor chip for maximizing the TMOKE intensity. Enhanced RI resolution is expected in sensor chips formed of a Au/Fe/wedge Au trilayer, which will contribute to improvements in the limit of detection when measuring the analytes by analyzing the resulting signals.

Energy conversion to generate hot electrons through the excitation of localized surface plasmon resonance (LSPR) in metallic nanostructures is an emerging strategy in photovoltaics and photocatalytic devices. Important factors for surface plasmon and hot electron generation are the size, shape, and materials of plasmonic metal nanostructures, which affect LSPR excitation, absorbance, and hot electron collection. Here, we fabricated the ordered structure of metal-semiconductor plasmonic nanodiodes using nanosphere lithography and reactive ion etching. Two types of hole-shaped plasmonic nanostructures with the hole diameter of 280 and 115 nm were fabricated on Au/TiO2 Schottky diodes. We show that hot electron flow can be manipulated by changing the size of plasmonic nanostructures on the Schottky diode. We show that the short-circuit photocurrent changes and the incident photon-to-electron conversion efficiency results exhibit the peak shift depending on the structures. These phenomena are explicitly observed with finite difference time domain simulations. The capability of tuning the morphology of plasmonic nanostructure on the Schottky diode can give rise to new possibilities in controlling hot electron generation and developing novel hot-electron-based energy conversion devices.

Based on 30 keV silver ions at a fluence of 6 × 1016 ions·cm−2 implanted into SiO2, Al2O3 and YAG, we found that the nanocomposite layers embedded with silver nanoparticles are sensitive to the refractive index of overlays on the implanted surface. By dropping liquids with different refractive indices on the surface of nanocomposite layer, the reflection spectra of the rear surface would shift. The sample with YAG as the substrate has better performance by comparing with the other two samples. The prepared structures have the advantages of simple structure and stable performance, which has potential applications in localized surface plasmon resonance sensors.

Organic–inorganic hybrid perovskites have attracted widespread attention in relation to light-emitting diodes (LEDs) due to their excellent properties. However, the imperfect energy band alignment between the perovskite and poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) limits the device’s performance. Here, we have investigated the effect of blending MoS2 in PEDOT:PSS and the resulting performance of perovskite LEDs (PeLEDs). We found that the doping of MoS2 can optimize the energy barrier and promote hole injection, significantly improving the current efficiency (CE) of PeLEDs, which can be attributed to the distinguished electrical conductivity and improved charge injection balance. At the same time, the local surface plasmon resonance effect with Au nanoparticles (NPs) is also introduced to reduce the nonradiative recombination and effectively promote light emission to further improve the performance of PeLED devices. Compared to the control PeLEDs device with undoped PEDOT:PSS as the hole transport layer, a 223% enhancement in maximum CE and a 130% enhancement in maximum luminance are achieved, with an optimal volume ratio for the PEDOT:PSS:MoS2 of 1:0.4 and Au NPs of 10%. Thus, the optimization combination of MoS2 and Au NPs is an excellent approach to improve the performance of PeLEDs, thereby increasing the potential applications of PeLED devices.

Enhancing the light coupling efficiency of large-area monolayer molybdenum disulfide (1L-MoS2) is one of the major challenges for its successful applications in optoelectronics and photonics. Herein, we demonstrate a dramatically enhanced photoluminescence (PL) emission from direct chemical vapor deposited monolayer MoS2 on a fluorine-doped TiO2/Au nanoparticle plasmonic substrate, where the PL intensity is enhanced by nearly three orders of magnitude, highest among the reported values. The formation of TiO2/Au/1L-MoS2 ternary core–shell heterojunction is evidenced by the high-resolution transmission electron microscopy and Raman analyses. Localized surface plasmon resonance induced enhanced absorption and improved light coupling in the system was revealed from the UV–vis absorption and Raman spectroscopy analyzes. Our studies reveal that the observed giant PL enhancement in 1L-MoS2 results from two major aspects: firstly, the heavy p-doping of the MoS2 lattice is caused by the transfer of the excess electrons from the MoS2 to TiO2 at the interface, which enhances the neutral exciton emissions and restrains the trion formation. Secondly, the localized surface plasmon in Au NPs underneath the 1L-MoS2 film initiates exciton-plasmon coupling between excitons of the 1L-MoS2 and surface plasmons of the Au NPs at the MoS2/Au interface. The PL and Raman analyses further confirm the p-doping effect. We isolate the contributions of plasmon enhancement from the theoretical calculation of the field enhancement factor using the effective medium approximation of plasmonic heterostructure, which is in excellent agreement with the experimental data. This work paves a way for the rational design of the plasmonic heterostructure for the effective improvement in the light emission efficiency of 1L-MoS2, and may enable engineering the different contributions to enhance the optoelectronic performance of 2D heterostructures.

Distinguishing near-field intensity distribution and plasmon resonance peak wavelength of surface plasmon resonance of gold nano-rods (AuNRs) can provide information for the optimisation of localised surface plasmon and gap plasmon resonances of gold nano-rods. This work, shows the influence of how refractive indexes of the surrounding medium and adjacent surface, as well as, AuNRs pair inter-particle gap contributes to the generation of surface plasmon resonances. The simulation model presented consists of AuNRs pair situated on silicon dioxide (SiO2) and cerium dioxide/silicon dioxide (CeO2/SiO2) substrates with air and water as the surrounding media. The results show high near-field intensities at AuNRs/CeO2 interfaces with CeO2 refractive index (n = 2.38), and the near-field intensities contributed by the gap resonance is minimal between the AuNRs of inter-particle gap of 10 nm, however, the near-field intensities become significant near to the AuNRs/CeO2 interfaces because of reduced near-field interference. The simulation set-up provides the conditions for water splitting in thermochemical redox reaction of CeO2/CeO2-x resulting in the production of hydrogen. AuNRs pair with inter-particle gap of 5 nm situated on 10 nm thick CeO2 of CeO2/SiO2 substrate shows the most favorable conditions for water splitting.

Detecting analytes whose refractive index (RI) below 1.3 has crucial medical applications. A D-shaped photonic crystal fiber (PCF) sensor based on surface plasmon resonance (SPR), is proposed and simulated by the finite element method, and its sensitivity is optimized through tailoring distinct structure parameters. The simulation results indicate that in the broad RI range from 1.21 to 1.31, the wavelength sensitivity can reach up to 33 300 nm/RIU that greatly exceeds the existing PCF-SPR sensors for low RI detection, and the maximum figure of merit of 81 RIU−1 can be obtained.

We fabricated a highly sensitive layered structure of organic molecules and studied the influence of polarization of the external electromagnetic (EM) wave on the surface plasmon resonance response from the layered structure. The layered structure was formed by depositing a self-assembled monolayer (SAM) of mercaptoundecanoic acid (MUA) followed by a single layer of Langmuir-Schaefer (LS) film of traditional calamitic liquid crystal molecule, 4 -octyl-4-biphenylcarbonitrile (8CB). The SAM of MUA was found to be non-responsive towards the change in resonance angle (RA) of surface plasmon resonance (SPR) due to the change in polarization of the external EM wave. However, such layer provides a soft-surface platform for the single layer of 8CB molecules which gets perturbed locally due to the incidence of the external EM wave. We obtained an oscillatory modulation of the change in RA due to the change in polarization angle of the EM wave with respect to the plane of incidence. The magnitude of sensitivity was found to be ∼4 milli°/° angle of polarization of the external EM wave. This study strongly suggests that sensitivity of a SPR-based sensor can be controlled by altering the linear state of polarization of the incident external EM wave.

Surface plasmon resonance (SPR) sensors are widely explored due their ultra-sensitivity to even a minute alteration of refractive index. Knowledge of adsorption processes could be exploited to explain the performance and interaction mechanism of an SPR sensor. Here in, we report the fitting of the experimental SPR sensing data during the detection of low concentrations of acetone vapour (0.5-5 ppm) using the linearized and non-linearized format of the Langmuir and the Freundlich isotherm models. The sensing layer is made from a ternary composite material of doped polyaniline, reduced graphene oxide and chitosan. The objective is to find the best model, understand the interaction mechanism and investigate the performance of the sensing layer. Correlation factors and error values were used to determine the best fit. The results showed that the Freundlich model could fit the data better than the two formats of the Langmuir model. Also, the interaction mechanism was predicted to be the physical one due to the heterogeneity parameter value, n

In this study, two different n-CdS/p-Cu2S solar cells were prepared by evaporating Cu at different substrate temperatures (200 K and 300 K) by vacuum evaporation method on a single crystal CdS semiconductor. Field emission scanning electron microscope images showed that the Cu layer obtained at a temperature of 200 K was composed of nanoparticles in accordance with the soliton growth mechanism. Cu film thickness was determined as 395 ∓ 0.76 nm at 300 K substrate temperature and 187 ∓ 0.45 nm at 200 K substrate temperature. The current–voltage (I–V) and capacitance–voltage (C–V) characteristics of the solar cells were examined for 12 weeks in dark and light environments. Open-circuit voltage (V oc), short-circuit current (I sc), maximum power (P max), filling factor and efficiency (η) were calculated from I–V measurements. For the prepared solar cells, the highest efficiency value was obtained in the 7th week (η= 0.1360) at 200 K substrate temperature, while it was obtained in the 5th week (η = 0.0384) at 300 K substrate temperature. From C–V measurements, donor density (N d) and barrier potential (V bi) were calculated. The solar cell produced at 200 K substrate temperature has higher donor density (1st week 2.99 × 1016 cm−3) and barrier potential values (12th week 0.411 V). At the end of the 12-week period, the deterioration rate of solar cells created at 200 K and 300 K substrate temperatures was 51% and 94%, respectively.

Gold nanoparticles (AuNPs) represent a relatively simple nanosystem to be synthesised and functionalized. AuNPs offer numerous advantages over different nanomaterials, primarily due to highly optimized protocols for their production with sizes in the range 1–150 nm and shapes, spherical, nanorods (AuNRs), nanocages, nanostars or nanoshells (AuNSs), just to name a few. AuNPs possess unique properties both from the optical and chemical point of view. AuNPs can absorb and scatter light with remarkable efficiency. Their outstanding interaction with light is due to the conduction electrons on the metal surface undergoing a collective oscillation when they are excited by light at specific wavelengths. This oscillation, known as a localized surface plasmon resonance, causes the absorption and scattering intensities of AuNPs to be significantly higher than identically sized non-plasmonic nanoparticles. In addition, AuNP absorption and scattering properties can be tuned by controlling the particle size, shape, and the local refractive index near the particle surface. By the chemical side, AuNPs offer the advantage of functionalization with therapeutic agents through covalent and ionic binding, which can be useful for biomedical applications, with particular emphasis on cancer treatments. Functionalized AuNPs exhibit good biocompatibility and controllable distribution patterns when delivered in cells and tissues, which make them particularly fine candidates for the basis of innovative therapies. Currently, major available AuNP-based cancer therapeutic approaches are the photothermal therapy (PTT) or photodynamic therapy (PDT). PTT and PDT rely upon irradiation of surface plasmon resonant AuNPs (previously delivered in cancer cells) by light, in particular, in the near-infrared range. Under irradiation, AuNPs surface electrons are excited and resonate intensely, and fast conversion of light into heat takes place in about 1 ps. The cancer cells are destroyed by the induced hyperthermia, i.e. the condition under which cells are subject to temperature in the range of 41 °C–47 °C for tens of minutes. The review is focused on the description of the optical and thermal properties of AuNPs that underlie their continuous and progressive exploitation for diagnosis and cancer therapy.

In this letter, we proposed an advanced dual-band detector based on the plasmonic response of patterned graphene integrated on a gold array. The photodetector shows ultra-high photoresponse performance in both visible light (0.4–0.7 μm) and mid-infrared (4–14 μm) light. The highest achievable responsivity of 2.7 A W−1 is comparable with typical visible and mid-infrared photodetectors. The working wavelength can be tuned by changing the external gate voltage bias, the dimension of graphene, and the architecture of the gold array. The demonstration of a surface plasmon resonance enhanced detector brings us a step closer to high sensitivity room-temperature multiband devices.

We propose a structure suitable for surface plasmon resonance (SPR) excitation with light incident on the back-side of the device, which has affinity with the semiconductor process. We constructed a diffraction grating on the top layer of a silicon-on-insulator wafer and completely embedded the grating in a polymer. According to a reflectance measurement, SPR could be efficiently excited, and its behavior presented consistency with the calculations. Since this structure is semiconductor fabrication based and allows elimination of both the prism and the light receiver commonly used in SPR experiments, it will contribute to realization of a thin one-chip SPR device.

Compared with the glass surface, the photoluminescence intensity of CsPbBr3 quantum dots excited by 1200 nm femtosecond laser on the surface of Au island fiber film (AIF) is significantly enhanced. On the other hand, the photoluminescence intensity decay of CsPbBr3 quantum dots on the AIF surface shows a fast decay of the average photoluminescence lifetime. The Photoluminescence enhancement effect of CsPbBr3 quantum dots was analysed by photoluminescence spectrum, transmission electron microscope, absorption spectrum and photoluminescence decay. The spectral changes of CsPbBr3 quantum dots on the AIF surface are related to surface plasmon resonance. The enhanced photoluminescence of CsPbBr3 quantum dots on the AIF surface can be used in optical communication and quantum information communication.

We have investigated in detail the growth dynamics of gold nanorods with various aspect ratios in different surrounding environments. Surprisingly, a blue shift in the temporal evolution of colloidal gold nanorods in aqueous medium has been observed during the growth of nanorods by UV visible absorption spectroscopy. The longitudinal surface plasmon resonance peak evolves as soon as the nanorods start to grow from spheres, and the system undergoes a blue shift in the absorption spectra. Although a red-shift is expected as a natural phenomenon during the growth process of all nanosystems, our blue shift observation is regarded as a consequence of competition between the parameters of growth solution and actual growth of nanorods. The growth of nanorods contributes to the red-shift which is hidden under the dominating contribution of the growth solution responsible for the observed massive blue shift., Comment: 24 pages. 8 figures

The development of high-effective photodetectors operating in a wide spectral range is an important technological task. In this work we have demonstrated that the detection bandwidth ofh-BN photodetectors in the UV range can be extended due to the surface plasmon resonance (SPR) effect. Theoretical calculations showed that, among Al, Au, Ag, and Cu, Al is the most suitable metal for theh-BN UV sensible detectors due to the SPR effect in the middle UV range. Based on the theoretical predictions, a simple and highly efficient method for obtainingh-BN/Al nanocomposites for localized SPR-based UV detectors was developed. It was demonstrated that theh-BN/Al material is sensitive to UV radiation with a wavelength of 266 nm that is far away of the detection limit of 240 nm inherent for pureh-BN.

Dye-sensitized solar cells (DSSCs) have recently gained much attention, due to the low-cost materials and their cheaper manufacturing techniques. However, these cells show a weak response to incident solar photons, resulting in poor power-conversion efficiency. In this paper, we described an improvement to the optical absorption efficiency of DSSCs in the wavelength range between 350 nm and 750 nm using the surface plasmon-resonance effect of plasmonic nanoparticles. Three different structures are studied, including unilayer, bilayer, and trilayer photoanodes based on various core–shell plasmonic spherical nanoparticles made of Ag@TiO2. In all structures, the nanoparticle size is optimized to obtain broadband optical absorption. The absorption efficiency of the dye-sensitized solar cell is significantly improved, from 65.2% to 72.3%, by tuning the photoanode structure from unilayer to trilayer. The results show that a unilayer photoanode with smaller-sized nanoparticles leads to higher absorption, compared to larger sizes. The UV–vis results indicate that mixing large- and small-sized nanoparticles in bi- and trilayer photoanodes is a good approach for improving the light-harvesting efficiency of DSSCs, compared to uniformly distributed nanoparticles. A maximum short-circuit current density of 17.32 mA cm−2 is recorded for a photoanode based on a trilayer structure of Ag@TiO2 nanoparticles.