Surface Plasmon Resonance Phenomenon Research Articles

Au nanoparticles-modified S-scheme In2O3/H1.5CN heterojunction with enhanced photocatalytic CO2 reduction activity

The construction of S-scheme heterojunction is of great significance for the photocatalytic reduction of CO2. Here, we prepared two-dimensional (2D) ultra-thin g-C3N4 by acidifying the carbon nitride precursor, and used In2O3 to construct a S-scheme heterojunction with 2D g-C3N4, and finally In2O3/H1.5CN was modified with Au nanoparticles. The physicochemical properties of the prepared materials were studied by SEM/TEM, XPS, DRS, PL and photochemical test. Meantime, the S-scheme charge transfer mechanism was demonstrated by UPS and ESR. As a result, on the one hand, S-scheme heterojunction accelerated the transfer of electrons on the CB of In2O3 to the VB of g-C3N4, avoided the recombination of photon-generated carrier. On the other hand, Au, as an effective cocatalyst, promoted photoinduced electron transfer and provided more active sites for CO2 reduction and the local surface plasmon resonance phenomenon caused by Au NPs enhanced the visible light absorption capacity of the composite material. Moreover, 2D thin layer of g-C3N4 played a carrier effect to disperse In2O3 cube. Therefore, In2O3/H1.5CN/2Au had stable CO2 reduction products, and the yields of CO/CH4 reached 141.24/77.05 μmol/g.

100 GSM paper as an SERS substrate for trace detection of pharmaceutical drugs in an aqueous medium

Surface-enhanced Raman spectroscopy (SERS) is a unique technique that allows us to detect samples in trace quantities. The spectral intensities of the characteristic Raman peaks of the analyte molecule are enhanced manifold in the presence of noble metal nanoparticles (NPs). The existence of NPs is necessary to couple the incident electromagnetic field with NPs through the localized surface plasmon resonance phenomenon, which primarily contributes to the enhancement of an SERS signal. The present work demonstrates the working of a paper-based SERS substrate to detect and quantify two pharmaceutical drugs—paracetamol and aspirin—in water. The proposed SERS substrate was obtained by drop-casting silver NPs over printing grade 100 grams per square meter (GSM) paper. 100 GSM denotes the class of paper where 100 grams of raw materials (cellulose) is used per square meter to manufacture the paper. The performance of the designed SERS substrate was initially evaluated with two Raman active samples—malachite green and rhodamine-6G. The applicability of the proposed SERS substrate was evaluated further through monitoring the Raman spectra of the two aforementioned pharmaceutical drugs in different field-collected water samples, thus establishing the reliability of the scheme in a real field environment.

Cascade integration of nonlinear phenomena exhibited by monometallic nanoparticles

In this work were numerically analyzed the third-order nonlinear optical effects exhibited by combinations of uncoupled monometallic silver, gold and platinum nanoparticles. The nanosystems were considered to be homogeneous and surrounded by a dielectric matrix. The design of the nanostructures was evaluated as a collective behavior resulting from the specific order of the set in trilayer tandem form. The characteristic Localized Surface Plasmon Resonance phenomena in the yellow, green and ultraviolet absorption bands for the Ag, Au and Pt; respectively, were considered. Different permutations of the three kind of monometallic elements selected in sequence were studied by using the wave equation and the finite difference method. Immediate indications useful for exploring nonlinear nanodevices and for building up nanostructured platforms based on nanoscale functions can be anticipated from this work.

Mechanistic insight the visible light driven hydrogen generation by plasmonic Au-Cu alloy mounted on TiO2 @B-doped g-C3N4 heterojunction photocatalyst

Designing of two dimensional surfaces and interfaces with light-active materials has been established as a versatile approach to increase their photocatalytic activity. In the present work, n-type anatase TiO 2 coupled with p-type B-doped g-C 3 N 4 nanosheet (BCN) were fabricated and Au-Cu nanoalloy with varying atomic ratio were deposited on the p-n heterojunction. The incorporation of Au-Cu on the interface of the dyad enhances light absorption over broad regime, charge separation, and migration. Au-Cu with 1:1 ratio (with an average particle size of 1.2 nm) loaded p-n hetrojunction (TBCAC-1:1) shows excellent photocurrent enhancement (approximately 4.4-folds) in the cathodic direction as compared to their monometallic plasmonic counterpart. Additionally, the catalyst shows photocurrent at zero biased potential as well as lower onset potential as compared to the other alloy. TBCAC-1:1 photocatalyst could able to produce 2150 μmol h −1 g −1 of hydrogen, which is (approximately 3-folds) as compared to their monometallic counterparts. The hydrogen evolution process for Au-Cu (1:1) system was found to be governed by the charge distribution which dictates the binding preference of the Au and Cu sites leading to the water splitting as investigated by DFT calculation. The excellent hydrogen generation by the photocatalyst links to the synergistic effect between Au and Cu associated with the hot electron photochemistry due to surface plasmon resonance phenomenon. Hot electron mediated H 2 generation by a plasmonic TiO 2 /BCN/Au-Cu photocatalyst • n-type TiO 2 with p-type B-doped g-C 3 N 4 nanosheet (BCN) were fabricated and Au-Cu nanoalloy were deposited on it. • Au-Cu on the interface of the dyad enhances light absorption over broad regime, charge separation, and migration. • Au-Cu with 1:1 ratio loaded p-n hetrojunction (TBCAC-1:1) shows excellent photocurrent enhancement in the cathodic direction as compared to other. • TBCAC-1:1 produced 2150 μmol h -1 g -1 of hydrogen (approximately 3-folds) as compared to monometallic counterparts. • The hydrogen evolution process is governed by the charge distribution between Au and Cu sites investigated by DFT calculation.

Graphene Oxide-Sensitized Surface Plasmon Resonance Biosensor of Porcine Reproductive and Respiratory Syndrome Virus.

Biosensor analysis based on the surface plasmon resonance (SPR) phenomenon enables label-free, highly sensitive analyte detection without prior sample purification or processing. However, potential applications of SPR biosensors in virus detection in biological samples remain to be explored. Owing to its excellent biocompatibility and abundance of hydroxyl and carboxyl functional groups, graphene oxide (GO) has been widely used as a biosensor of proteins and metal ions in living cells. The present work explored the effect of GO modification on the sensitivity of an SPR biosensor and used a GO-modified sensor to detect porcine reproductive and respiratory syndrome virus in cell culture, as shown. The GO modification markedly enhanced the sensitivity of the Fourier transform SPR sensor and enabled linear detection of porcine reproductive and respiratory syndrome virus (PRRSV) with a multiplicity of infection in the range 0.2–1.7 (R2 = 0.998). Such a GO-modified sensor provides a promising alternative for virus detection.

Design of Au nanorods-based plasmonic catalyst in combination with nanohybrid Pd-rGO layer for boosting CO2 hydrogenation to formic acid under visible light irradiation

In recent years, research on the use of surface plasmon resonance phenomena induced by visible to near-infrared light for photocatalytic reactions has attracted much attention from the viewpoint of solar energy utilization. It has been extensively researched that the plasmon-mediated catalytic reaction can be promoted due to the injection of energetic hot electrons originating during the relaxation process of the surface plasmon resonance (SPR) into the reaction substrate molecules. In this report, we have prepared Pd/Au NRs@rGO nanocatalyst in which Au nanorods (NRs) with plasmonic properties are surrounded by a layer of reduced graphene oxide (rGO) with excellent electrical conductivity, and Pd nanoparticles (NPs) are supported on the Au NRs to efficiently transport hot electrons to the reaction substrate. The successful synthesis of the catalyst was characterized by HAADF-STEM, TEM, UV–vis, XRD, XAFS, and ICP analysis. The applicability of the prepared catalyst was tested in the photocatalytic reduction of CO2 to formic acid (FA) reaction under visible light irradiation. A photocatalytic FA yield of 1.7 μmol was obtained in 24 h, which was 2.7-fold higher than in dark reaction conditions. The SPR enhancement of Pd/Au NRs in combination with rGO in Pd/Au NRs@rGO catalyst led to the superior product yield of FA under visible light irradiation and room temperature conditions.

Smartphone-based Surface Plasmon Resonance Sensors: a Review.

The surface plasmon resonance (SPR) is a phenomenon based on the combination of quantum mechanics and electromagnetism, which leads to the creation of charge oscillations on a metal–dielectric interface. The SPR phenomenon creates a signal which measures refractive index change at the metal–dielectric interface. SPR-based sensors are being developed for real-time and label-free detection of water pollutants, toxins, disease biomarkers, etc., which are highly sensitive and selective. Smartphones provide hardware and software capability which can be incorporated into SPR sensors, enabling the possibility of economical and accurate on-site portable sensing. The camera, screen, and LED flashlight of the smartphone can be employed as components of the sensor. The current article explores the recent advances in smartphone-based SPR sensors by studying their principle, components, application, and signal processing. Furthermore, the general theoretical and practical aspects of SPR sensors are discussed.

Tuning Surface Plasmon Resonance Responses through Size and Crosslinking Control of Multivalent Protein Binding-Capable Nanoscale Hydrogels.

Surface plasmon resonance (SPR) phenomena have been widely studied to detect biomolecules because of their high sensitivity and ability to determine biomolecular interactions with kinetic information. However, highly selective detection in specific concentration ranges relevant to target biomolecules is still a challenging task. Recently, we developed bioresponsive nanoscale hydrogels to selectively intensify SPR signals through multivalent protein binding (MPB) events with target biomolecules, including IL-2, where we were able to demonstrate exceptional selectivity for target biomolecules with minimal responses to nonspecific and monovalent binding events. In this work, we systematically explored the relationship between the physical properties of MPB-capable nanoscale hydrogels and their SPR response induced in the presence of the programmed cell death protein 1 antibody (PD-1Ab) as a model target biomolecule. First, we developed a synthetic protocol by controlling various reaction parameters to construct a library of nanoscale poly(N-isopropylacrylamide-co-acrylic acid) hydrogels (NHs) with different sizes (from 400 nm to 1 μm) and degrees of crosslinking (from 2 to 8%). Then, by incorporating MPB-capable PD-1 receptors onto the surface of NHs to form PD-1-responsive nanoscale hydrogels (PNHs), the hydrogel size and crosslinking dependency of their SPR responses were investigated. Our results reveal the appropriate hydrogel size regime and degree of crosslinking for effective PD-1Ab detection at specific concentrations range between a few nM and 1 μM. Overall, our study demonstrates that by tuning the physical properties of the nanoscale hydrogel matrix, the sensitivity and detection range of MPB-based SPR sensors can be modulated to potentially benefit clinical applications such as monitoring diverse therapeutic biomolecules.

Design of refractive index sensing based on optimum combination of plasmonic materials gold with indium tin oxide/titanium dioxide

In this research work, a penta core photonic crystal fiber (PCF)-based refractive index (RI) sensor is presented to address the surface plasmon resonance (SPR) phenomenon. The proposed RI sensor (PRIS) model is tested with two material configurations, i.e., gold-indium tin oxide (Au–ITO) and gold–titanium dioxide (Au–TiO2). Analytes having an RI varying from 1.340 to 1.380 RIU are tested from the PRIS for both material configurations. These configurations are compared with each other based on sensor parameters, such as wavelength sensitivity (WS), amplitude sensitivity (AS), linearity, and sensor resolution (SR). The sensor parameters are investigated for both transverse electric (TM) mode and transverse electric (TE) mode. The proposed sensor with Au–ITO configuration offers a maximum WS of 12,000 nm / RIU, AS of 13,640 RIU − 1, and maximum SR of 8.33 × 10 − 6 RIU for TM mode. Corresponding to the TE mode maximum WS of 11,000 nm / RIU, AS of 12,180 RIU − 1 and maximum SR of 9.09 × 10 − 6 RIU are obtained. The proposed sensor with the Au–TiO2 configuration presents a maximum WS of 12,000 nm / RIU, AS of 20,370 RIU − 1, and maximum SR of 8.33 × 10 − 6 RIU for the TM mode. Corresponding to the TE mode maximum WS of 13,000 nm / RIU, AS of 18,100 RIU − 1 and maximum SR of 7.69 × 10 − 6 RIU is obtained. The maximum values of the sensor features are obtained for the analyte with RI 1.375 RIU for both configurations. Finally, a comparison between sensing parameters of plasmonic material ITO and TiO2 is performed, and optimum material is identified when used with Au for RI sensing.

Photothermal Therapy with HER2-Targeted Silver Nanoparticles Leading to Cancer Remission.

Nanoparticles exhibiting the localized surface plasmon resonance (LSPR) phenomenon are promising tools for diagnostics and cancer treatment. Among widely used metal nanoparticles, silver nanoparticles (Ag NPs) possess the strongest light scattering and surface plasmon strength. However, the therapeutic potential of Ag NPs has until now been underestimated. Here we show targeted photothermal therapy of solid tumors with 35 nm HER2-targeted Ag NPs, which were produced by the green synthesis using an aqueous extract of Lavandula angustifolia Mill. Light irradiation tests demonstrated effective hyperthermic properties of these NPs, namely heating by 10 °C in 10 min. To mediate targeted cancer therapy, Ag NPs were conjugated to the scaffold polypeptide, affibody ZHER2:342, which recognizes a clinically relevant oncomarker HER2. The conjugation was mediated by the PEG linker to obtain Ag-PEG-HER2 nanoparticles. Flow cytometry tests showed that Ag-PEG-HER2 particles successfully bind to HER2-overexpressing cells with a specificity comparable to that of full-size anti-HER2 IgGs. A confocal microscopy study showed efficient internalization of Ag-PEG-HER2 into cells in less than 2 h of incubation. Cytotoxicity assays demonstrated effective cell death upon exposure to Ag-PEG-HER2 and irradiation, caused by the production of reactive oxygen species. Xenograft tumor therapy with Ag-PEG-HER2 particles in vivo resulted in full primary tumor regression and the prevention of metastatic spread. Thus, for the first time, we have shown that HER2-directed plasmonic Ag nanoparticles are effective sensitizers for targeted photothermal oncotherapy.

Long-Term Plasmonic Stability of Copper Nanoparticles Produced by Gas-Phase Aggregation Method Followed by UV-Ozone Treatment

Coinage metal nanoparticles (NPs) are well-known for the phenomenon of localized surface plasmon resonance (LSPR), which is widely utilized for enhanced sensing and detection. LSPR stability over time is an important issue for the practical application of nanoparticle matrices. Some metals, and copper among those, are chemically reactive in ambient atmospheric conditions that leads to degradation of plasmonic functionality. This work reports on the formation of Cu NP matrices utilizing magnetron-sputtering gas-phase aggregation, size-selection and soft-landing on a substrate. This method provides monocrystalline NPs with high purity, thus, improving chemical inertness towards ambient gases, for example, oxygen. Additionally, a simple approach of UV-ozone treatment is shown to form an oxide shell protecting the metallic core against reactions with environmental species and stabilizing the plasmonic properties for a period of over 150 days. The suggested methodology is promising to improve the competitiveness of Cu nano-matrices with those of Au and Ag in plasmonic sensing and detection.

Evaluation of Structural and Optical Properties of Graphene Oxide-Polyvinyl Alcohol Thin Film and Its Potential for Pesticide Detection Using an Optical Method

In the present work, graphene oxide (GO)–polyvinyl alcohol (PVA) composites thin film has been successfully synthesized and prepared by spin coating techniques. Then, the properties and morphology of the samples were characterized using Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-Vis), and atomic force microscopy (AFM). Experimental FTIR results for GO–PVA thin film demonstrated the existence of important functional groups such as -CH2 stretching, C=O stretching, and O–H stretching. Furthermore, UV-Vis analysis indicated that the GO–PVA thin film had the highest absorbance that can be observed at wavelengths ranging from 200 to 500 nm with a band gap of 4.082 eV. The surface morphology of the GO–PVA thin film indicated the thickness increased when in contact with carbaryl. The incorporation of the GO–PVA thin film with an optical method based on the surface plasmon resonance (SPR) phenomenon demonstrated a positive response for the detection of carbaryl pesticide as low as 0.02 ppb. This study has successfully proposed that the GO–PVA thin film has high potential as a polymer nanomaterial-based SPR sensor for pesticide detection.

Polarization-Multiplexed Incoherent Broadband Surface Plasmon Resonance: A New Analytical Strategy for Plasmonic Sensing.

Surface plasmon resonance (SPR) is an interfacial phenomenon, and the plasmonic sensors are based on the optical excitation of the collective oscillations of free electrons at a metal-dielectric interface. Here, we present the new development of an incoherent broadband (IBB)-SPR probe combining the wavelength interrogation technique with polarization-multiplexing (PM). The performance characteristics of the so-called PMIBB-SPR strategy was validated for the detection of nonenzymatic aqueous urea samples as a representative example for plasmonic sensing with an excellent wavelength and phase sensitivities of 0.1363 nm/mM and 10.34597 mM/deg, respectively. We further explored the missing link between plasmonic polariton resonance (PPR) and polarization modulation via the measurements of the Stokes parameters of the reflected light. This deepens our understanding of the fundamentals of polarization-multiplexed SPR phenomenon at the interface. This study thus paves the way to develop a new-generation analytical technique with the aim of tracking various real-time chemical and biological molecular interactions occurring at the interfaces.

Designing highly sensitive exposed core surface plasmon resonance biosensors

With technological advancement, photonic crystal fibers (PCFs) are effectively used to design miniaturized, flexible, and efficient biosensors. This paper proposes an exposed core PCF biosensor based on widely known surface plasmon resonance (SPR) phenomena. An external sensing mechanism is followed to characterize the sensing performance within the refractive index (RI) range between 1.28 and 1.40. Metal strip (gold (Au) and titanium dioxide (TiO2)) is deposited on the outer surface only along the four channels instead of the entire surface, which could decrease the difficulties associated with the metal deposition on the entire circular surface. Simulating the sensor using finite element method based COMSOL Multiphysics software, we find tremendous amplitude sensitivity of 7420.69 RIU−1 and wavelength sensitivity of 87,000 nm/RIU. In addition, the sensor offers the highest resolution of 7.7×10−6 RIU, the figure of merit of 1011.63 RIU−1, signal to noise ratio of 10.05 dB, the detection accuracy of 0.016598 nm−1, and detection limit of 102.23 nm. However, the promising sensing performance indicates that the proposed sensor could be implemented effectively to detect different biological and chemical substances.

Microchannel-Embedded D-Shaped Photonic Crystal Fiber-Based Highly Sensitive Plasmonic Biosensor

An improved design of a D-shaped photonic crystal fiber (PCF)-based refractive index (RI) sensor is proposed that uses the surface plasmon resonance phenomenon. The sensor consists of a large semicircular open channel that is inserted at the upside of the D-shaped PCF. A thin plasmonic sensing layer is deposited on the interior surface of the channel to excite the surface plasmon wave that eliminates the requirement of additional effort to fabricate a well-polished sensing layer of the D-shaped sensor. The sensor’s optical properties are numerically explored by the finite element method. The sensor is optimized to detect the RI of biological and biochemical analytes in the range of 1.33 to 1.44, shows spectral sensitivity as high as 63,000 nm/RIU with a spectral resolution of 1.59 × 10−06 RIU, and maximum amplitude sensitivity of 1439 RIU−1 with a resolution of 6.94 × 10−06 RIU. It is also found that the sensor’s linearity parameter is very high with a large figure of merit of about 839. Additionally, the sensor’s fabrication tolerance is studied by varying its structural parameters. Therefore, high sensing parameters with a wide detection range make this microchannel-based D-shaped PCF sensor an appropriate device for the application of biological and biochemical analyte detection.

Ultra‐Sensitive β‐Ga2O3 Solar‐Blind Photodetector with High‐Density Al@Al2O3 Core−Shell Nanoplasmonic Array

Abstractβ‐Ga2O3 solar‐blind photodetectors (PDs) are attracting great attention for broad applications. However, their detection sensitivities are still lower than expected after tremendous efforts. The phenomenon of localized surface plasmon resonance (LSPR) offers another approach beyond conventional techniques to engineer the photodetection performance, but extending the plasmonic properties into the deep‐ultraviolet region faces severe challenges, among which strictly controlling the nanostructures structural properties is extremely prominent besides material selection. Herein, well‐defined Al@Al2O3 core−shell nanostructure arrays are fabricated with sub‐50 nm feature sizes, narrow dimension distributions, periodic graphene‐like patterns, and extremely high densities (up to 152.7 counts µm−2). The decorated β‐Ga2O3 PDs exhibit significantly enhanced sensitivities without response spectra broadening. Particularly, the sample with a 42‐nm nanostructure array possesses an ultrahigh specific detectivity (4.22 × 1015 Jones), being one of the top among film‐type gallium oxide PDs, and an excellent responsivity of 216.0 A W−1 peaked at 235 nm. Moreover, the passivation effect of self‐terminating native oxide shell is confirmed. The finite‐difference time‐domain simulations based on isolated, dimer, and arrayed models not only demonstrate the presence of LSPR, but also reveal the critical contribution of nanostructure density. The findings provide an alternative platform to break the bottleneck and develop ultra‐sensitive, truly solar‐blind PDs for advanced optoelectronic systems.

Selective Colorimetric Detection of Mercury(II) using Silver Nanoparticles-Chitosan

Contamination of the environment by hazardous metal ions has been a major environmental issue for the past several decades. Among several hazardous metals, mercury ion (Hg(II)) is of particular concern as its compounds are extremely toxic. Hence, developing detection methods for traces of Hg(II) ions in aquatic systems is critical for mercury pollution mitigation. One method that can be used to monitor Hg(II) in aquatic systems is colorimetry-based method which is simple, rapid, and low-cost, yet selective and sensitive. The method can be conducted by applying the Localized Surface Plasmon Resonance phenomenon of metal nanoparticles, such as silver nanoparticles. There are non-Hg(II) ions in the aquatic environment that can interfere the measurements. Thus, a selective method is needed to obtain a valid measurement result. Here, we introduced silver nanoparticles-chitosan (AgNPs-Ch) synthesized by chemical reduction as a selective probe of Hg(II) in an aqueous solution. The AgNPs-Ch was synthesized from silver nitrate at 80°C using trisodium citrate and chitosan as reducing agent and stabilizer, respectively. The synthesized nanoparticles were spherical with an average size below 15.0 nm. Moreover, the AgNPs-Ch was selective for Hg(II) with a linearity of 0.9556 in the concentration range of 1 - 5 ppm and was able to detect the ion down to 1.33 ppm.

Highly sensitive gold-film surface plasmon resonance (SPR) sensor employing germanium selenide (GeSe) nanosheets

Although surface plasmon resonance (SPR) methods are frequently employed due to their remarkable advantages such as reduced sample requirements, they confront a significant challenge in terms of sensitivity improvement. GeSe is an appropriate material for resolving this issue. According to the theoretical basis of the research, GeSe is a two-dimensional material which is a direct band gap semiconductor that may be utilized to promote electron transport and stimulate greater SPR phenomena. The first use of GeSe in an optical fiber sensor is reported in this study. A U-shaped optical fiber-GeSe-Au sensor is proposed. As a two-dimensional material with comparable physical characteristics to GeSe, MoS2 is compared to GeSe to characterize its influence upon the sensitivity. The sensitivity of fiber-GeSe-Au sensor is 7398.1 nm/refractive index unit (RIU), which is nearly twice as sensitive as a gold film SPR sensor and 1.5 times as sensitive as a sensor utilizing MoS2 nanosheets with the same structure. This study introduces a novel approach for enhancing the sensitivity, which gives a new option for monitoring biological substances at low concentrations with high sensitivity and stability and demonstrates that GeSe nanosheets have significant promise for future applications.

Spatially selective nanoplasmonic response in Ag embedded GLAD TiO2 nanocomposite thin films

The nanoplasmonic behaviour of Ag decorated TiO2 film structure was spatially varied across the sample surface by utilizing the tailored optical response of the underlying dielectric TiO2 thin film prepared using a novel collimated glancing angle deposition technique (collimated-GLAD). A blue shift in maximum attenuation coefficient region and minimum film transmittance region of the Ag/collimated-GLAD TiO2 nanocomposite coating with increase in height from the evaporation source was detected. The presence of minimum transmittance region was found to have occurred due to localized surface plasmon resonance (LSPR) phenomenon with additional contribution from thin film interference. The measured transmittance spectra showed spatial selectivity in LSPR wavelength of ∼22 nm with increase in height from the evaporation source. The variation of surrounding medium's (i.e. the TiO2 layer) refractive index (with height from the evaporation source) of the Ag nanostructures was the key factor responsible for the spatially varying nanoplasmonic response of Ag/collimated-GLAD TiO2 film across the sample surface. The Surface enhanced Raman scattering (SERS) characterization of the Ag/collimated-GLAD TiO2 film revealed photocatalysis driven dimerization conversion of p-aminothiophenol (p-ATP) molecules to p,p’-dimercaptoazobisbenzene (DMAB) due to the localized surface plasmons of the film structure along with the substantial enhancement in the Raman peak intensities compared to the blank substrate.

Study of the Optical and Thermoplasmonics Properties of Gold Nanoparticle Embedded in Al2O3 Matrix.

In this paper, the optical and thermoplasmonics properties of nanocomposites consisting of spherical gold nanoparticles (AuNPs) integrated in {Al}_{2}{O}_{3} matrix are determined using the Finite Element Method (FEM). Firstly, the refractive index (n), extinction coefficient (kappa ), absorption coefficient {(mu }_{a}), and optical conductivity (sigma ) are calculated from the effective complex permittivity obtained by solving the Laplace’s equation for different size and concentration of nanoparticles. The surface plasmon resonance (SPR) properties of AuNPs are optimized from the peak presented in the absorption coefficient spectrum. The results show that the optical parameters n, kappa , {mu }_{a}, and sigma undergo a strong variation around the wavelength {lambda }_{max} corresponding to the SPR phenomenon. The value of {lambda }_{max} increases from 560 to 600 nm when the radius of the particles varies between r=5 and r=30 nm. The effect of the AuNP concentration on the band gap energy {E}_{g}(eV) of Au-{Al}_{2}{O}_{3} nanocomposites is also studied, a shift from Eg=5.34 to Eg=5.49 eV is observed when the concentration of the AuNPs increases from 0 to 0.82mathrm{%}. The electric field enhancement induced by the AuNPs at plasmonic resonance is also determined depending to the particle size; the results show that the enhancement factor increases from g=4.71 to g=6.95 when the radius of the AuNPs increases from r=5 to 30 nm. The thermal dissipation of the plasmonic energy of spherical of our system dispersed in the {Al}_{2}{O}_{3} matrix is determined considering the Joule effect which occurs by the oscillation of the charges at the plasmonic resonance. The generated thermal power by particles is calculated for different sizes, which allows to calculate the thermal power per gram of particles depending on the intensity of the incident electric field. The results show that the plasmonic thermal power is almost identical for small particles when the radius is less than r=15 nm and increases considerably when the size increases from r=15 to 30 nm. For a fixed size and incident field amplitude, we calculated the temperature change in the nanocomposites Au-{Al}_{2}{O}_{3} depending of time for different particle concentrations; the temperature variation curves obtained are linear as a function of time.