Range Surface Plasmon Research Articles

Deposition of plasmonic ITO nanoparticles by near-infrared laser ablation

Compound nanoparticles (NPs) attract attention because of their unique electrical, optical, and catalytic properties. Among them, plasmonic tin-doped indium oxide (ITO) NPs are characterized by transparency in the visible wavelength range and tunable localized surface plasmon resonance (LSPR) in the near-infrared (NIR) range due to high electronic conductivity. To date, they have been usually synthesized by a chemical solution process. However, the chemically synthesized ITO NPs are capped with organic protecting agents, which often block exchange of charge carriers and access of chemical species to the NPs, limiting some applications. In the present study, we propose a method for direct deposition of ITO NPs on a glass or plastic substrate using commercially available ITO-coated glass via NIR laser ablation. The LSPR characteristics of the ITO NPs, thus, prepared were controlled by changing the ablation conditions such as laser power. In addition, the potential applications of the ITO NPs were also investigated through measurements of their refractive index sensitivity and magnetic circular dichroism.

Detection of cortisol using long range surface plasmon resonance sensor with enhance figure of merit

Detection of cortisol using long range surface plasmon resonance sensor with enhance figure of merit

Tuning of the Cut-Off Frequency in Effective Medium Approximation and Long Range Surface Plasmon Excitation in Graphene and Black Phosphorus

Tuning of the Cut-Off Frequency in Effective Medium Approximation and Long Range Surface Plasmon Excitation in Graphene and Black Phosphorus

Ultra high sensitive long range surface plasmon resonance sensor for chemical and biochemical sensing

In this work, we proposed a long-range surface plasmon (LRSPR) sensor using a dielectric (Cytop) –Gold (Au)- graphene oxide (GO) layer to enhance the sensor’s detection accuracy (DA), figure of merit (FoM) and imaging sensitivity (Simag). The proposed sensor’s effectiveness for long-range is numerically demonstrated. The GO layer is used to protect the unwanted oxidation of Au and to improve the imaging sensitivity. By comparing its FoM and Simag to that of the traditional surface plasmon sensor (cSPR), the proposed sensor takes advantage of its high adsorption efficiency and high resolution. The Au-GO layer in the cSPR sensor and the cytop-Au-GO layer in the proposed sensor interfaces enhance the electric field intensity and penetration depth (PD). We attain the highest DA, FoM and Simag of 100/°, 1400/RIU, and 4183.9/RIU with 2000 nm of cytop thickness. For chemical and biological applications, the proposed LRSPR sensor design may be advantageous.

Detection of pathogens in water using long range surface plasmon resonance biosensor: Numerical investigation

This work presents a numerical demonstration for improving the imaging sensitivity of long-range surface plasmon (LRSPR) biosensors using the prism 2S2G/cytop/Cu/Gr (Graphene)/sensing medium (SM) configuration. In the suggested LRSPR biosensor, the imaging sensitivity is compared to that of the traditional surface plasmon sensor (tSPR) through numerical analysis. The proposed LRSPR sensor reaches 4655.7/RIU as its maximum imaging sensitivity for detecting E. coli bacteria. The maximum electric field intensity is found at the interface between the Cu/SM in the tSPR sensor and the Gr/SM in the proposed sensor. For pathogens detection such as pure-water (P.W.), Vibrio-Cholera (V.C.), Escherichia-Coli (E.coli), Bacillus-Anthracis (B.A.), and Enterococcus -aecalis (B.F), the penetration depth (PD) for the LRSPR sensor are 304.46 nm, 955.45 nm, 961.45 nm, 957.44 nm and 1050.7 nm. The LRSPR sensor's effectiveness in biosensing applications is further demonstrated by its figure of merit (FoM) for the detection of pathogens bacteria, which is 291.8/RIU (V.C), 781.5/RIU (E.coli), 59.28/RIU(B.A.) and 738.5/RIU (E.F.), respectively.

Design of a highly sensitive and precise long-range surface plasmon resonance sensor for early detection of malaria

This manuscript presents an innovative Kretschmann configured for Long Range Surface Plasmon Resonance (LRSPR) sensor for malaria detection. It utilizes tungsten diselenide (WSe2) as a bio+molecular recognition element (BRE) layer to attach target analyte. The optimized sensor design demonstrates exceptional performance in detecting different malaria stages (Schizont with refractive index (RI) = 1.371, Trophozoite with RI = 1.381, and Ring with RI = 1.396) at a 633 nm wavelength. In comparison to conventional surface plasmon resonance (CSPR), the LRSPR biosensor exhibits a substantial improvement, a 6.67 to 10 times increase in detection accuracy (DA), an impressive 40 to 86.55 times enhancement in imaging figure of merit (IFOM), and a 6.0 to 8.66 times boost in imaging sensitivity (Simg.) for the sequential detection of different stages of malaria. COMSOL Multiphysics simulations highlight a deeper penetration depth (PD) of 258.71 nm, 276.85 nm, and 373.04 nm for the detection of Schizont, Trophozoite, and Ring stages, respectively.

Wide refractive index detection range surface plasmon resonance sensor based on D-shaped photonic crystal fiber

We propose and simulate a surface plasmon resonance (SPR) refractive index (RI) sensor based on a novel D-shaped photonic crystal fiber. We used an open air hole coated with gold film to improve SPR effect. The sensor uses photonic crystal fiber with the same air holes diameter. The effects of structural parameters on resonance spectrum were analyzed by finite element method (FEM). Three SPR peaks were obtained in the wavelength range of 800–1300 nm. The maximum sensitivity is 5626.86 nm/RIU and the maximum resolution is 1.78 × 10−5 RIU at the refractive index of 1.38. The simulation results show that the refractive index detection range of the sensor is 1.26–1.38. Compared with other D-shaped structures, our sensor can measure larger RI ranges of the analyte.

Long-range surface plasmon resonance biosensors with cytop/Al/Perovskite and cytop/Al/MoS2 configurations

In this paper, long range surface plasmon resonance (LRSPR) biosensors with cytop/Al/Perovskite and cytop/Al/MoS2 configurations have been theoretically investigated and compared with standard LRSPR biosensor with cytop/Al/graphene configuration. To calculate the optical properties of considered configurations for the desired application, transfer matrix method for TM mode has been used to obtain reflectance. The sensitivity of the considered configurations for designed biosensors has been investigated with variation of optical parameters of the structure. A new configuration of LRSPR biosensors based on Al- MoS2 or Al-Perovskite has been proposed to enhance sensitivity, detection accuracy, and efficiency. The maximum value of sensitivity of the proposed Al-Perovskite based LRSPR biosensor is found to be 4847 RIU−1. Moreover, the sensitivity of Al-MoS2 and Al-Peroskite based LRSPR biosensors show nearly 10% and nearly 30% more optical responses respectively than the Al-graphene based LRSPR biosensor.

High-Sensitivity Biosensor With Optical Tunneling Effect Excited by Long-Range Surface Plasmon Resonance

Optical tunneling is an effect extremely sensitive to wavelength changes. In this article, we use this effect to design a new type of biosensor. The tunneling effect is excited by long range surface plasmon resonance, the energy is concentrated in the sensing medium in the form of standing waves, which lead a very high wavelength sensitivity and quality factor. By using COMSOL for finite element analysis, for the sensor structure of (BK7/Cytop /Al2O3/Ag/Al2O3/sensing media/air), a quality factor of 10296 RIU-1 is achieved under angle modulation,a sensitivity of 170,000 nm/ RIUand a quality factor of 11333 RIU-1 are obtainedunder wavelength modulation. At the same time, the advantage of this structure is that there is no excessive requirement on the refractive index of the material, and a good sensing effect can be achieved even if the material is cheap and easy to prepare. After optimization, this structure is suitable for sensing media with a refractive index of 1.335-1.375, which can be applied to most liquid solutions.

Enhancement of Sensitivity with High-Reflective-Index Guided-Wave Nanomaterials for a Long-Range Surface Plasmon Resonance Sensor.

A guided−wave long−range surface plasmon resonance (GW−LRSPR) sensor was proposed in this investigation. In the proposed sensor, high−refractive−index (RI) dielectric films (i.e., CH3NH3PbBr3 perovskite, silicon) served as the guided−wave (GW) layer, which was combined with the long−range surface plasmon resonance (LRSPR) structure to form the GW−LRSPR sensing structure. The theoretical results based on the transfer matrix method (TMM) demonstrated that the LRSPR signal was enhanced by the additional high#x2212;RI GW layer, which was called the GW−LRSPR signal. The achieved GW−LRSPR signal had a strong ability to perceive the analyte. By optimizing the low− and high−RI dielectrics in the GW−LRSPR sensing structure, we obtained the highest sensitivity (S) of 1340.4 RIU−1 based on a CH3NH3PbBr3 GW layer, and the corresponding figure of merit (FOM) was 8.16 × 104 RIU−1 deg−1. Compared with the conventional LRSPR sensor (S = 688.9 RIU−1), the sensitivity of this new type of sensor was improved by nearly 94%.

Smartphone integrated handheld Long Range Surface Plasmon Resonance based fiber-optic biosensor with tunable SiO2 sensing matrix

In the present work, a novel smartphone assisted fiber optic (FO)-Long range surface plasmon resonance (LRSPR) based biosensor is proposed. In the developed biosensor, the inbuilt color sensitive property of the digital camera present in the smartphone is used for the monitoring of blue and red color channel intensities. This will replace the most exploited diffraction gratings or narrow band filters used for analyzing the spectral data in reported smartphone based SPR sensors. The proposed technique helps in improving the sensitivity and reduces the chances of wrong detection. For the first time, SiO2 nanostructured film is employed as the dielectric sensing layer to excite the Long range surface plasmons (LRSPs) in the dielectric-metal-dielectric configuration. The proposed FO-LRSPR biosensor possess limit of detection of 0.02 mM and sensitivity of 0.9/mM and, for uric acid detection in the 0.1 mM–1 mM concentration range. The novel fabricated sensor which is found to be stable up to 24 weeks can be effectively utilized in health sector and environment monitoring and it possess the ability of point-of-care detection, even in rural and remote areas.

Compact resonant plasmonic hybrid waveguide refractive index sensors for aqueous medium

Ultra-compact and high sensitivity resonant plasmonic refractive index sensors for aqueous medium are proposed. The sensors are based on the resonant coupling between the waveguide mode and the surface plasmon mode supported by a thin metal layer. For optimized layer thicknesses, the periodic coupling between the two hybrid modes guided by the structure takes place and a resonant absorption peak appears for a particular sensor length. The sensors are designed to operate in the spectral mode at visible wavelengths centred about 0.6328 μm. The sensors have been designed for the long range surface plasmon polaritons (LRSPP) as well as the short range surface plasmon polaritons (SRSPP). This study provides a detailed understanding of designing an ultra-short and efficient sensor for the aqueous medium with high spectral sensitivity (S), ultrahigh resolution (R) and figure of merit (FOM). The attained numerical values show that for optimized layer thicknesses, a sensitivity of 9200 nm/RIU for LRSPP mode and 1800 nm/RIU for SRSPP mode can be achieved for the aqueous medium with the sensor lengths of 83.5 μm and 15 μm (shortest to the best of our knowledge) respectively. Also, the values of R and FOM are 1.52 × 10−7 RIU and 7.7 × 103 RIU−1 for the LRSPP based sensor and 6.7 × 10−7 RIU and 4.5 × 103 RIU−1 for the SRSPP mode based sensor.

Effect of buffer layer index on short range surface plasmon polariton based TE pass polarizer

We investigate theoretically the dependence of the extinction ratio, metal layer thickness and buffer thickness of a short length plasmonic polarizer on the buffer layer index. The polarizer section consists of a thin metal layer above the single mode dielectric waveguide separated by a low index dielectric buffer layer. Strong coupling between the surface plasmon polariton (SPP) mode and the guided mode takes place when their phase constants are matched. The SPP mode being of TM type, interacts with the guided TM mode and is completely absorbed by metal film due to resonant coupling between the two modes. The TE guided mode does not couple to the SPP mode and is passed un-attenuated through the polarizer. The buffer layer thickness can be optimized to maximize the TM mode attenuation and reduce the TE losses, which provides a large extinction ratio. Since the polarizer is based on the interference of the SPP mode and the waveguide mode, a periodic coupling of the field takes place between these two modes. It is shown that for properly optimized layer thicknesses, an extinction ratio exceeding 200 dB can be achieved for various buffer layer indices. Effect of buffer layer index on the polarizer length is also presented.

Refractive index tuning of SiO2 for Long Range Surface Plasmon Resonance based biosensor

A novel, highly sensitive and low cost Long Range Surface Plasmon Resonance (LRSPR) biosensor for detecting uric acid, as a model analyte, has been developed in this work. Silicon dioxide (SiO2) having low and tunable refractive index has been chosen as the dielectric layer for the excitation of LRSP modes replacing the most explored Cytop and Teflon polymers. The prepared LRSPR based uric acid bio-sensor gives good response characteristics with a high sensitivity of about 21.6°/mM and low limit of detection (LOD) of 0.02 mM. The fabricated LRSPR sensor was also evaluated to detect uric acid in real serum samples. The results yield a great scope to promote the development of robust, efficient and highly selective LRSPR based biosensors with SiO2 as tunable dielectric layer.

Perfect absorption in symmetrical single layer ultrathin metal grating with unilateral illumination

In symmetric environment, as the tangential electric field is almost constant across the ultrathin film, the absorption rate of the film is up to 0.5 under single side illumination. In this letter, we propose a symmetrical single layer ultrathin metal grating structure where perfect absorption (up to 0.99) can be achieved with unilateral illumination. We consider that this phenomenon of extraordinary optical absorption is caused by the coupling of the localized surface plasmon resonance and the long range surface plasmon. In particular, the electromagnetic response of the metal grating we proposed greatly resembles the electromagnetic induced absorption (EIA) which shows a narrow absorption peak within a broad absorption profile.

Long Range Surface Plasmons assisted highly sensitive and room temperature operated NO2 gas sensor

Long Range Surface Plasmons (LRSPs) are excited in the SnO2/Au/SnO2/prism structure using Kretschmann configuration for detecting NO2 gas. SnO2 thin films of two different thicknesses are grown by RF sputtering technique and 205 nm thin SnO2 film resulted in the sharp LRSP resonance (LRSPR) reflectance curve with the minimum reflectance (Rmin) = 0.05 at the resonance angle (θspr) of 42.38°. LRSPR based room temperature (22 °C) operated gas sensor using the optimized SnO2/Au/SnO2/prism configuration is developed in the present work for effectively detecting NO2 gas in a broad concentration range from 0.5 ppm to 2000 ppm. The LRSPR reflectance curve corresponding to the prepared sensor shows an appreciable shift of 8.47° in the resonance angle on exposure to NO2 gas (2000 ppm). The developed optical sensor illustrated high sensitivity (0.2°/ppm) along with the limit of detection (LOD) of 0.38 ppm of NO2 gas. The sensor exhibited outstanding selectivity towards NO2 gas and showed insignificant response to various other interfering gases. The obtained results highlight the successful fabrication of competent LRSPR based optical gas sensor capable of detecting NO2 gas at room temperature.

Photonic crystal fiber based wide-range of refractive index sensor with phase matching between core mode and metal defect mode

A high sensitivity wide range surface plasmon resonance (SPR) refractive index sensor based on photonic crystal fiber (PCF) has been proposed in this paper. The finite element method (FEM) is used to calculate and analyte the structure of PCF. The optical properties of the PCF are investigated by adjusting the refractive index of liquid analyte. By optimization, the fiber sensor achieves a high linearity refractive index sensitivity of 0.9979 and 1931.03 nm / RIU over a refractive index range from 1.350 to 1.460 and achieves a short PCF length of 1 mm. It is allowed the sensor to be small enough to be integrated into inspection equipment,and expected to gain important applications in the fields of biological monitoring, environmental monitoring, and chemical production.

Highly sensitive long range surface plasmon based liquid sensor by shining the radially polarized light in bimetallic taper fiber structure

A new approach towards the enhancement of sensitivity in fiber optic liquid sensor is proposed, designed and simulated using the long range surface plasmon resonance technique shining the radially polarized light in bimetallic fiber structure, which comprises a fiber core coated with 40 nm and 10 nm thin Ag and Au layer respectively. The radially outward field distribution of the radially polarized light enables the multiple point plasmonic interaction on the whole fiber periphery which enhances the sensitivity as well as the dynamic range of refractive index sensing through the proposed sensor. A 13 times and 25 times better sensitivity has been estimated using NaCl and KCl solution as compared with the existing articles till date using p-polarized light. Minimum measurable concentration is 0.5 g/l and 1 g/l for NaCl and KCl solutions for a minimum change in output power of 30.04 μW and 25.60 μW respectively using InGaAs detector. With enhanced sensitivity and higher dynamic range of refractive index, this new idea explores the new avenues in the field of fibre optic liquid sensing applications.

Nano-film aluminum-gold for ultra-high dynamic-range surface plasmon resonance chemical sensor

An analytical and experimental study of nanofilm aluminum (Al) for ultra-high dynamic range surface plasmon resonance (SPR) biosensor is presented in this article. A thin film of 16 nm Al is proposed for metallic sensing layer for SPR sensor. For the protective layer, a 10 nm of gold (Au) layer was configured on top of Al as a protection layer. This ultra-high dynamic range of SPR biosensor reached the bulk refractive index sample limit up to 1.45 RIU. For the analytical study, with the assumption of anisotropic refractive indices experiment, the dynamic range showed a refractive index value of around 1.58 RIU. The refractive index value limit achieved by the proposed sensing design is potentially implemented in various applications, such as in chemical detection and environmental monitoring study with high refractive index solution sample. The experimental results are presented as a proof-of-concept of the proposed idea.

Optimization of angle-pixel resolution for angular plasmonic biosensors

An angular plasmonic sensor based on optimized angle-pixel resolution to detect antibody-antigen binding process is presented. Owing to discrete resonance curves by the CCD pixels, the pixel sensitivity and detection noise of the plasmonic sensors need to be balanced. The angle-pixel resolution is adjusted by changing the distance between the sensor chip and the CCD to obtain the optimal refractive index (RI) resolution for three plasmonic sensors, which are surface plasmon resonance (SPR), long range surface plasmon resonance (LRSPR) and plasmon waveguide resonance (PWR) sensors. Each plasmonic sensor can achieve its optimal RI resolution at the optimal distance, and the LRSPR sensor has the best RI resolution. Attributing to the reference channel and temperature control module in the sensor system, the RI resolution can achieve 4.37 × 10−7 RIU at Normal mode and 1.13 × 10-7 RIU at a slow response Extreme mode. The Protein A-IgG binding reaction experiment indicates that the plasmonic sensor has linear response to IgG concentration in a wide range and the limit of detection (LOD) is 5.45 pM at Extreme mode. The procedure and result of this work are helpful to the optimization of other angular plasmonic sensors.