Generation Of Surface Plasmon Resonance Research Articles

Gold-coated split laser-induced periodic surface structures as refractometric sensors

The generation of surface plasmon resonances (SPR) in laser-induced periodic surface structures (LIPSS) allows their application in the field of optical sensing, such as the detection of refractive index variations in gases and liquids. We have fabricated gold-coated LIPSS nanostructures on stainless steel substrates by using femtosecond laser nano-ablation. This technique is a low-cost and high-throughput fabrication method applicable to fast and large-scale manufacturing. The depth profile of the fabricated LIPSS shows a central dip at the top of each ripple that split the geometry. The actual topography is modeled and included in a computational electromagnetism package to obtain the expected optical response under the experimental conditions. The measured and simulated spectral reflectances are compared, and the differences are explained by the departure of the fabricated LIPSS from the ideal topography. The experiments and simulations showed excellent agreement for the main spectral characteristics, like the Fano-like lineshapes of the spectral reflectance. This fitting provides the values used to determine the refractometric performance of the fabricated device, that shows a sensitivity of 518 nm/RIU and a figure of merit of 32 RIU−1 for an aqueous analyte. Our experimental results show that the fabricated devices are competitive in terms of cost and simplicity when compared to existing devices with similar performance.

Plasmonic heating of protected silver nanowires for anti-frosting superhydrophobic coating

Atmospheric frosting and icing pose significant problems for critical and common-use infrastructures. Passive anti-frosting and anti-icing strategies that require no energy input have been actively sought, with no viable and permanent solutions known yet. Bioinspired superhydrophobic (SH) materials have been considered promising path to explore; however, the outcome has been less than compelling because of their low resistance to atmospheric humidity. In most cases, condensing water on an SH surface eventually leads to mechanical locking of ice instead of ice removal. Hybrid strategies involving some form of limited energy input are being increasingly considered, each with its own challenges. Here, we propose the application of plasmonic heating of silver nanowires (AgNWs) for remote frost removal, utilizing an SH hybrid passive-active system. This novel system comprises a durable nanocomposite covered with a hydrophobized mesh of AgNWs, protected against environmental degradation by a tin oxide (SnO2) shell. We demonstrate the frost removal ability at −10 °C and 30% RH, achieved by a combination of plasmonic heating of AgNWs with a non-sticking behavior of submicrometric droplets of molten frost on the SH surface. Heating was realized by illuminating the mesh with low-power blue laser light. Adjustment of the nanowire (NW) and shell dimensions allows the generation of surface plasmon resonance in illuminated NWs at a wavelength overlapping the emission maximum of the light used. In environmental stability tests, the nanostructures exhibited high atmospheric, mechanical, and thermal stability. The narrow-wavelength absorption of the structure in the blue light range and the reflective properties in the infrared range were designed to prevent protected surfaces from overheating in direct sunlight.

Ultrasensitive Optical Temperature Transducers Based on Surface Plasmon Resonance Enhanced Composited Goos-Hänchen and Imbert-Fedorov Shifts

The spatial and angular Goos-Hänchen and Imbert-Fedorov shifts occur simultaneously for the light beam reflected from a lossy surface (e.g., metal surface). The mixture of spatial and angular Goos-Hänchen (Imbert-Fedorov) shifts, referred to as composited Goos-Hänchen (Imbert-Fedorov) shift, has been experimentally confirmed in recent years. The temperature-dependent composite Goos-Hänchen and Imbert-Fedorov shifts for a light beam reflected from the prism-gold interface in the Kretschmann-Raether configuration are theoretically investigated. The spatial and angular Goos-Hänchen and Imbert-Fedorov shitfs of p-polarized incident light are significantly enhanced around the resonant angle with the generation of surface plasmon resonance. The ultrahigh temperature sensitivities of 0.79 cm/K and 188 μm/K are obtained with the composite Goos-Hänchen and Imbert-Fedorov shift, respectively, which are about 5 orders higher than those obtained with a bare gold surface. The ultrahigh temperature sensitivity is mostly contributed by the angular shift effect. Our results demonstrated the importance of angular shift effect in achieving an ultrahigh sensitivity. This work can serve as a guidance for the design of temperature sensor, chemical sensor and biosensor based on composite Goos-Hänchen and Imbert-Fedorov shifts.

2-D Study of Near-field Generated by Surface Plasmon Resonance of Short Axis of Gold Nano-rods on SiO2 and CeO2/SiO2 Substrates for Optimisation of Water Splitting Reaction

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.

Plasmon-enhanced photoelectrochemical water splitting by InGaN/GaN nano-photoanodes

It has been extensively focused on the development of photoelectrochemical (PEC) solar water splitting cells due to the urgent need for clean energy. In this study, InGaN/GaN multiple quantum wells (MQWs) nanorods (NRs) PEs are purposely designed with coupled plasmonic metal (Ag–Au core–shell nanowires) for high efficiency PEC water splitting, aiming for enhancing visible light absorption and carrier kinetic energy. By means of self-organized Nickel island patterning and ICP dry etching with proper depths, the photocurrent density of InGaN/GaN nano-photoanodes in NaCl solution can be significantly enhanced from 0.74 mA cm−2 to 1.4 mA cm−2 at 1.5 V versus RHE (reversible hydrogen electrode). Furthermore, by decorating plasmonic metal into the InGaN/GaN NR arrays, the PEC water splitting performance can reach a maximum photocurrent of 1.77 mA cm−2 at 1.5 versus RHE. Such improvement is mainly attributed to the synergistic effects of the visible light absorption of MQWs and the generation of surface plasmon resonance (SPR). The approach of plasmon-enhanced nanostructure with the III-nitride based nano-PEs will accelerate the developments of visible light photocatalysts for PEC solar cells.

Protein Trapping in Plasmonic Nanoslit and Nanoledge Cavities: The Behavior and Sensing.

A novel plasmonic nanoledge device was presented to explore the geometry-induced trapping of nanoscale biomolecules and examine a generation of surface plasmon resonance (SPR) for plasmonic sensing. To design an optimal plasmonic device, a semianalytical model was implemented for a quantitative analysis of SPR under plane-wave illumination and a finite-difference time-domain (FDTD) simulation was used to study the optical transmission and refractive index (RI) sensitivity. In addition, total internal reflection fluorescence (TIRF) imaging was used to visualize the migration of fluorescently labeled bovine serum albumin (BSA) into the nanoslits; and fluorescence correlation spectroscopy (FCS) was further used to investigate the diffusion of BSA in the nanoslits. Transmission SPR measurements of free prostate specific antigen (f-PSA), which is similar in size to BSA, were performed to validate the trapping of the molecules via specific binding reactions in the nanoledge cavities. The present study may facilitate further development of single nanomolecule detection and new nanomicrofluidic arrays for effective detection of multiple biomarkers in clinical biofluids.

Immunosensing with Near-Infrared Plasmonic Optical Fiber Gratings.

Surface Plasmon resonance (SPR) optical fiber biosensors constitute a miniaturized counterpart to the bulky prism configuration and offer remote operation in very small volumes of analyte. They are a cost-effective and relatively straightforward technique to yield in situ (or even possibly in vivo) molecular detection. They are usually obtained from a gold-coated fiber segment for which the core-guided light is brought into contact with the surrounding medium, either by etching (or side-polishing) or by using grating coupling. Recently, SPR generation was achieved in gold-coated tilted fiber Bragg gratings (TFBGs). These sensors probe the surrounding medium with near-infrared narrowband resonances, which enhances both the penetration depth of the evanescent field in the external medium and the wavelength resolution of the interrogation. They constitute the unique configuration able to probe all the fiber cladding modes individually, with high Q-factors. We use these unique spectral features in our work to sense proteins and extra-cellular membrane receptors that are both overexpressed in cancerous tissues. Impressive limit of detection (LOD) and sensitivity are reported, which paves the way for the further use of such immunosensors for cancer diagnosis.

Experimental demonstration of lossy mode and surface plasmon resonance generation with Kretschmann configuration

Lossy mode resonances (LMRs) and surface plasmon resonaces (SPRs) are obtained experimentally with a Kretschmann configuration using a BK7 glass prism with all sides polished and coated with indium tin oxide (ITO). The properties of ITO allow for obtaining LMRs and SPRs with the same experimental setup. The results are corroborated with a numerical method for calculation of the reflection in the Kretschmann configuration.

Generation of Surface Plasmon Resonance and Lossy Mode Resonance by thermal treatment of ITO thin-films

Silicon wafers coated with Indium Tin Oxide (ITO) by application of sputtering technique have been characterized after different post-annealing techniques, showing that this last factor is critical for the quality of the thin-film and for the creation and tuning of both surface plasmon resonances and lossy mode resonances. By adequate selection of the ITO thin-film thickness both resonances can be tracked in the same spectrum, which can be used in sensor and optical communications fields.

Effect of the structure of a network matrix on the formation of gold nanoparticles during photoreduction of its salts in solutions of acrylic oligomers

The effect of network parameters of three-dimensionally crosslinked polyacrylic optically transparent matrices on the generation of surface plasmon resonance of gold nanoparticles forming during irradiation of Au3+ salt solutions in a liquid acrylic composite is studied. During the UV irradiation of a solution, the photoreduction of gold and the photoinitiated polymerization of acrylates proceed simultaneously to form transparent colorless films in which, after subsequent light and/or heat treatment, an absorption band near 550 nm that corresponds to the plasmon resonance of nanosize metal particles is generated. During the photoreduction of gold salt in matrices of oligo(urethane acrylate) composites with similar structures of the oligomeric block, the parameters of the three-dimensional network—the internodal and interchain distances—affect the rate of generation of gold nanoparticles but not the limiting value of optical density for the plasmon-resonance band of nanoparticles. Polyacrylate matrices may serve as a registering medium for optical data recording.

High resolution interrogation of tilted fiber grating SPR sensors from polarization properties measurement

The generation of surface plasmon resonances (SPRs) in gold-coated weakly tilted fiber Bragg gratings (TFBGs) strongly depends on the state of polarization of the core guided light. Recently, it was demonstrated that rotating the linear state of polarization of the guided light by 90° with respect to the grating tilt allows to turn the SPR on and off. In this work, we measure the Jones matrix associated to the TFBG transmission properties in order to be able to analyze different polarization-related parameters (i.e. dependency on wavelength of polarization dependent loss and first Stokes parameter). As they contain the information about the SPR, they can be used as a robust and accurate demodulation technique for refractometry purposes. Unlike other methods reported so far, a tight control of the input state of polarization is not required. The maximum error on refractive index measurement has been determined to be ~1 10(-5) refractive index unit (RIU), 5 times better than intensity-based measurements on the same sensors.