Recent Advances in Magnetooptics: Innovations in Materials, Techniques, and Applications

Imaging surface plasmon resonance system for screening affinity ligands

Development of an Au/ZnO thin film surface plasmon resonance-based biosensor immunoassay for the detection of carbohydrate antigen 15‐3 in human saliva

In this paper we propose Otto surface plasmon resonance (SPR) system with tunable air-gap using piezoactuator for the first time. The proposed Otto configuration based SPR system include a piezoactuator for varying an air-gap distance between a prism and gold surface. We verified effects of air-gap variation in Otto SPR system and the measured results show that the Otto SPR sensor can be realized with a metal film and prism by using a microactuator without complex microfabrication process for specific air-gap distance.

This paper describes a statistical approach that improves the detection accuracy in simulated experimental surface plasmon resonance (SPR) systems operated in a conventional angular readout scheme. Two SPR system have been investigated: a conventional one and a second one, containing absorbing metallic nanoparticles within the sensing layer. The modified Maxwell-Garnett model that optimally describes the experimental literature results was applied to modeling of the nanoparticle-inclusive sensor. Statistical hypothesis testing was then used to determine the limit of detection of the analyte and nanoparticles. Analyte concentrations as low as 1 pM, corresponding to the refractive index change of 4x10(-8) have been detected with optimized metal layers operated close to the nanoparticle absorption maximum. This is about one order of magnitude smaller than the values obtained in conventional SPR systems with nanoparticles and comparable to the phase-sensitive surface plasmon resonance detection.

Room temperature detection of NO2 gas using optical sensor based on surface plasmon resonance technique

A surface plasmon resonance system for the measurement of glucose in aqueous solution

Optical glucose measurement is an attractive research topic for years. One of the goals is to develop a portable device for continuous and non-invasive monitoring of blood glucose for diabetics. In this work, a surface plasmon resonance (SPR) system, which has a high detection sensitivity of 7.61/spl times/10/sup -7/ refractive index unit (RIU), is utilized for measuring the glucose concentration in aqueous solution. The experimental results show that this approach, which measures the optical behavior of glucose solution, may possibly reveal a new pathway for the non-invasive measurement of blood glucose.

Analysis of Carbohydrates Using Liquid Chromatography–Surface Plasmon Resonance Immunosensing Systems

Simple yet ultrasensitive and accurate quantification of a variety of analytical targets by virtue of a universal sensing device holds promise to revolutionize environmental monitoring, medical diagnostics, and food safety. Here, we propose a novel optical surface plasmon resonance (SPR) system in which the frequency-shifted light of different polarizations returned the laser cavity to stimulate laser heterodyne feedback interferometry (LHFI), hence amplifying the reflectivity change caused by the refractive index (RI) variations on the gold-coated SPR chip surface. In addition, the s-polarized light was further used as the reference to compensate the noise of the LHFI-amplified SPR system, resulting in nearly 3 orders of magnitude enhancement of RI resolution (5.9 × 10-8 RIU) over the original SPR system (2.0 × 10-5 RIU). By exploiting nucleic acids, antibodies, and receptors as recognition materials, a variety of micropollutants were detected with ultralow detection limits, ranging from a toxic metal ion (Hg2+, 70 ng/L) to a group of commonly occurring biotoxin (microcystins, 3.9 ng microcystin-LR/L) and a class of environmental endocrine disruptors (estrogens, 0.7 ng 17β-estradiol/L). This sensing platform exhibits several distinct characteristics, including dual improvement of sensitivity and stability and common-path optical construction without needing optical alignment, demonstrating a promising avenue toward environmental monitoring.

A new aptamer-based surface plasmon resonance (SPR) system has been designed to detect Hg2+ that utilizes near-infrared (NIR)-to-NIR gold nanoparticle coated NaYF4:Yb,Tm,Gd up-conversion nanoparticles (AuNPs@NaYF4:Yb,Tm,Gd UCNPs) as probes. The AuNPs@NaYF4:Yb,Tm,Gd UCNPs were prepared and excited by near-infrared light (980 nm) which emitted at a near-infrared wavelength (808 nm) using an inexpensive infrared continuous wave laser diode. The AuNPs@NaYF4:Yb,Tm,Gd UCNPs were conjugated with Hg2+ aptamers. In the presence of Hg2+, the AuNPs@NaYF4:Yb,Tm,Gd UCNPs were brought into close proximity because of the formation of T-Hg2+-T base pairs. Then the luminescence enhanced because of the plasmon resonance effects. Based on this, a new SPR system was developed for the detection of Hg2+ that had high sensitivity and selectivity in the NIR region. This method was successfully applied to detect Hg2+ concentration in real samples.

Customizable miniaturized SPR instrument

An Automatic Miniature Surface Plasmon Resonance System for Cortisol Detection

Surface plasmon resonance (SPR) is the collective oscillation of free electrons at the interface between metal and dielectric layers. Since the resonant condition of SPR is dominated by refractive indices of metal and dielectric layer, it is possible to distinguish the refractive index change of dielectric layer through the shifts of resonant condition. Considering the system resolution of SPR system nowadays, the sensing resolution up to 10-6 RIU (refractive index change) is available for a general SPR system. Accordingly, SPR provides a label-free platform to detect bio-interactions. However, for pursuing trace measurement, rapid detection, precise diagnosis, versatile functions, or lower cost, researchers devote themselves to develop different interrogations for diverse applications. For the most general four interrogations: angle, wavelength, intensity, and phase are well applied in current literatures. In this study, we focus on the sensitivity enhancement and potential applications of SPR interrogated by different routes, in order to expend its applying fields. For the non-complicated and efficient sensing platform, intensity interrogation, we discussed the relation between sensitivity and thickness of metal sensing layer, and further derived a generalized sensitivity model for intensity interrogation SPR system. In addition, we found that the optimized metal thickness in intensity interrogation is different from the thickness for best coupling efficiency, which is the most commonly used in research. This difference can be explained through two damping factors in SPR. For the sophisticated and ultra-sensitive sensing platform, phase interrogation, we applied such interrogation on LSPR. LSPR is characterized by coupler-free excitation, nano-scale, and diverse resonant modes; nevertheless, its sensitivity is over 10 folds lower than SPR. In contrast with other researchers who modified the resonant modes, we used phase interrogation instead of extinction spectra to enhance the sensitivity. Our results show that the sensitivity was enhanced over 80 folds at the same LSPR structures under the near-field excitation. This study not only confirms the feasibility of exploiting LSPR by optical phase, but also complements its insufficiency on sensitivity. For the low-cost and large linear detection range sensing platform, wavelength interrogation, we expect to have the potential application on point-of-care test. We proposed a color SPR system based on wavelength interrogation, in which we directly observed the color change of reflection rather than identified the resonant wavelength through spectrometer. Moreover, by using Ag/Au bi-metallic film to replace the general used Au film, we are able to enhance the sensitivity and color contrast without losing linear detection range. In short, we hope to promote SPR sensing system through the studies on intensity, phase, and wavelength interrogations.

Ethanol concentration was quantified by the use of a compact surface plasmon resonance (SPR) system, which electrically detects hot electrons via a Schottky barrier. Although it is well known that SPR can be used as bio/chemical sensors, implementation is not necessarily practical, due to the size and cost impediments associated with a system with variable wavelength or angle of incidence. However, scanning capability is not a prerequisite if the objective is to use SPR in a sensor. It is possible to build a small, inexpensive SPR sensor if the optics have no moving parts and a Schottky barrier is used for electrical current detection in place of a photodetector. This article reports on the design and performance of such a novel SPR sensor, and its application for quantifying ethanol concentration. As the concentration of ethanol is increased, the change in the angle dependence of the SPR current is observed. This change can be understood as a superposition of contributions of SPR coupled with the +3rd- and −3rd-order diffraction. Moreover, real-time monitoring of ethanol concentration was demonstrated using the proposed SPR system.

Surface plasmon resonance (SPR) biosensors are an extremely sensitive optical technique used to detect the changes in refractive index occurring at the sensor interface. Fluorescence involves the emission of light by a substance that has absorbed light or other electromagnetic radiation, and the parameters of the absorbed and emitted radiation are used to identify the presence and the amount of specific molecules in a specimen. SPR biosensors and fluorescence analysis are both effective methods for real-time detection. The combination of these technologies would improve the quantitative detection sensitivity of fluorescence analysis and the specificity of SPR detection. We designed and developed an SPR and fluorescence synchronous detection system. The SPR module was based on two kinds of modulation methods, and the fluorescence module was capable of switching between four wavelengths. The fluorescence microspheres and A549 cells of different concentration were both detected by the SPR and fluorescence method synchronously in real time. The fluorescent signal and the optical signal of the SPR were shown to correlate. The correlation coefficient for fluorescent microspheres detection reached up to 0.9866. The system could be used in cell analysis and molecule diagnosis in the future.