Localized Surface Plasmon Resonance and Refractive Index Sensitivity of Metal–Dielectric–Metal Multilayered Nanostructures

The localized surface plasmon resonances of multilayered nanostructures are studied using finite difference time domain simulations and plasmon hybridization method. Concentric metal–dielectric–metal (MDM) structure with metal core and nanoshell separated by a thin dielectric layer exhibits a strong coupling between the core and nanoshell plasmon resonance modes. The coupled resonance mode wavelengths show dependence on the dielectric layer thickness and composition of core and outer layer metal. The aluminum-based MDM structures show lower plasmon wavelength compared with Ag- and Au-based MDM nanostructures. The calculated refractive index sensitivity (RIS) factor is in the order Ag–Air–Ag>Au–Air–Au>Al–Air–Al for monometallic multilayered nanostructures. Bimetallic multilayered nanostructures support strong and tunable plasmon resonance wavelengths as well as high RIS factor of 510 nm/refractive index unit (RIU) and 470 nm/RIU for Al–Air–Au and Ag-Air-Au, respectively. The MDM structures not only exhibit higher index sensitivity but also cover a wide ultraviolet–near-infrared wavelengths, making these structures very promising for index sensing, biomolecule sensing, and surface-enhanced Raman spectroscopy.     

Modeling of a Graphene Nanoribbon–based Microfluidic Surface Plasmon Resonance Biosensor

Plasmonics - A surface plasmon resonance (SPR) biosensor based on a graphene nanoribbon array in a microfluidic flow cell operating in a flow-over format is studied. The optical response of the...     

A High-Performance Refractive Index Sensor Based on Hybrid Resonance Modes in a Square Nanocavity Coupled with Metal–Insulator–Metal Plasmonic Waveguide

Plasmonics - We present one of the simplest nanoscale systems for a high-performance refractive index (RI) sensor. We investigate analytically and numerically the transmission response of the...     

Optical Biochip with Multichannels for Detecting Biotin–Streptavidin Based on Localized Surface Plasmon Resonance

A rapid and accurate detection of molecular binding of antigen-antibody signaling in high throughput is of great importance for biosensing technology. We proposed a novel optical biochip with multichannels for the purpose of detection of biotin–streptavidin on the basis of localized surface plasmon resonance. The optical biochip was fabricated using photolithography to form the microarrays functioning with multichannels on glass substrate. There are different nanostructures in each microarray. Dry etching and nanosphere lithography techniques were applied to fabricate Ag nanostructures such as hemispheres, nanocylindricals, triangular, and rhombic nanostructures. We demonstrated that 100-nM target molecule (streptavidin) on these optical biochips can be easily detected by a UV-visible spectrometer. It indicated that period and shape of the nanostructures significantly affect the optical performance of the nanostructures with different shapes and geometrical parameters. Our experimental results demonstrated that the optical biochips with the multichannels can detect the target molecule using the microarrays structured with different shapes and periods simultaneously. Batch processing of immunoassay for different biomolecular through the different channels embedded on the same chip can be realized accordingly.     

The Plasmon–Plasmon Coupling in a System of a Dielectric Slab Doped with Silver Nano-spheres Sandwiched Between Two Silver Parallel Plates

I compute the transmission coefficient as function of the incident light frequency for a system consisting of a dielectric slab doped with silver nano-spheres sandwiched between two silver parallel plates. Then, I analyze the details of the transmission spectrum identifying the coupled plasmons from the two (doped dielectric and plates) subsystems which dominate the system’s dynamics.     

Giant Enhancement of Transmitted Light and Its Localization Due to Elastic Surface Plasmon–Polariton Scattering by a Thin Dielectric Diffraction Grating

The enhancement factor for surface plasmon–polaritons scattering by a thin dielectric grating was measured experimentally. Scattering of a p-polarized wave may be up to 30,000 times stronger than the non-resonant scattering of an s-polarized wave by the same grating. A detailed comparison between the theoretical calculations and experimental measurements was performed. Strong localization of the scattered field near the edges of diffraction grating grooves was found. Such localization is very promising for numerous applications, e.g., biological sensors, optical tweezers for catching particles, or viruses, etc.     

Use of Surface Plasmon Resonance and Biolayer Interferometry for the Study of Protein–Protein Interactions on the Example of an Enzyme of a Glycosyl Hydrolase Subtype (EC 3.2.1) and Specific Antibodies to It

Two previously obtained, full-size, fully human antibodies that reversibly bind the active form of an enzyme belonging to the subtype EC 3.2.1, which is used for substitutive enzymatic therapy in lysosomal storage diseases, have been characterized by surface plasmon resonance and biolayer interferometry methods. It was shown under normal physiological conditions that the designed antibodies specifically bound with the antigen (KD ~ 10^–8 M) and rapidly dissociated at neutral pH in 60% ethylene glycol while leaving the enzymatic activity unchanged. Dan ue to their properties, the developed antibodies can be used in industry as affinity ligand in the isolation of therapeutic substances of the enzyme.     

Noble Metal Ion Embedded Nanocomposite Glass Materials for Optical Functionality of UV–Visible Surface Plasmon Resonance (SPR) Surface-Enhanced Raman Scattering (SERS) X-ray and Electron Microscopic Studies: An Overview

Plasmonics - Raman spectroscopy (RS) is a modern scientific analytic fingerprint technique that detects, examines, and analyzes the constituent chemical composition of various substances...     

Identification of a novel and potent inhibitor of phospholipase A(2) in a medicinal plant: crystal structure at 1.93Å and Surface Plasmon Resonance analysis of phospholipase A(2) complexed with berberine

Crystal of Russell Viper venom phospholipase A(2) complexed with an isoquinoline alkaloid, berberine from a herbaceous plant Cardiospermum halicacabum, was prepared and its structure was solved by X-ray crystallography. The crystal diffracted up to 1.93? and the structure solution clearly located the position of berberine in the active site of the enzyme. Two hydrogen bonds, one direct and the other water mediated, were formed between berberine and the enzyme. Gly 30 and His 48 made these two hydrogen bonds. Additionally, the hydrophobic surface of berberine made a number of hydrophobic contacts with side chains of neighboring amino acids. Surface Plasmon Resonance studies revealed strong binding affinity between berberine and phospholipase A(2). Enzyme inhibition studies proved that berberine is a competitive inhibitor of phospholipase A(2). It was inferred that the isoquinoline alkaloid, berberine, is a potent natural inhibitor of phospholipaseA(2).     

Effects of episodic turbulence on diatom mortality and physiology,with a protocol for the use of Evans Blue stain for live–dead determinations

Short-lived, high-intensity turbulence in aquatic environments—or episodic turbulence—has been shown to cause mortality in zooplankton, but its effects on marine phytoplankton have rarely been investigated. Episodic turbulence derives from anthropogenic and natural causes such as boat propellers, strong winds, and breaking waves. This study focused on the effects of episodic turbulence on two diatoms: Thalassiosira weissflogii and Skeletonema costatum. 45 s exposure to turbulence intensities above 2.5 cm² s^?3 reduced diatom abundance by up to 32% and increased the number of intact dead cells by 22%. After exposure to 4.0 cm² s^?3, photosynthetic efficiency decreased by 25 and 9% in T. weissflogii and S. costatum, respectively. Turbulence also caused extracellular release of optically reactive DOM and biologically important trace metals such as iron. The turbulence levels tested are comparable to those under breaking surface waves and are substantially lower than those generated by boat propellers. An improved technique using the Evans Blue stain was developed to enable visual live/dead plankton cell determinations. When used in conjunction with preservation and flow cytometry, this staining method provides a way to study phytoplankton mortality due to turbulence and other environmental stresses.     

Simulations of the Ion Current to a Probe in Plasma with Allowance for Ionization and Ion–Neutral Collisions: II. Cylindrical Probe

The ion current to a cylindrical probe is considered with allowance for volume ionization, ion–neutral collisions, and the ion orbital moment. A model based on the molecular dynamics method and applicable in a wide range of plasma parameters (r_p/λ_D= 0.01–100, r_i/λ_D= 0.002–200, ν_i/ω_0i= 0.01–0.05, and T_i/T_e = 0?0.01) is proposed A convenient representation of the dependence of the relative ion current density on the Langmuir coefficient β² and a technique for determining the plasma density from simulation results are offered.     

Evaluation of a Minimally Invasive Cell Sampling Device Coupled with Assessment of Trefoil Factor 3 Expression for Diagnosing Barrett's Esophagus: A Multi-Center Case–Control Study

BackgroundBarrett''s esophagus (BE) is a commonly undiagnosed condition that predisposes to esophageal adenocarcinoma. Routine endoscopic screening for BE is not recommended because of the burden this would impose on the health care system. The objective of this study was to determine whether a novel approach using a minimally invasive cell sampling device, the Cytosponge, coupled with immunohistochemical staining for the biomarker Trefoil Factor 3 (TFF3), could be used to identify patients who warrant endoscopy to diagnose BE.ConclusionsThe Cytosponge-TFF3 test is safe and acceptable, and has accuracy comparable to other screening tests. This test may be a simple and inexpensive approach to identify patients with reflux symptoms who warrant endoscopy to diagnose BE.