Gold Film Surface Plasmon Resonance Research Articles

Prism SPR Glucose Sensor Based on Gold Nanoparticle/Gold Film Coupling Enhanced SPR

A novel glucose sensor based on gold nanoparticles (AuNPs) enhanced surface plasmon resonance (SPR) is proposed for the accurate detection of glucose concentration. The coupling enhancement effect of localized surface plasmon resonance (LSPR) of AuNPs and SPR of gold film can improve the refractive index sensitivity of the sensor. The specific reaction between glucose and glucose oxidase (GOD) causes a change in the refractive index of the glucose solution microenvironment and eventually leads to a drift in the resonance angle. Field emission scanning electron microscopy (SEM) was used to characterize the GOD before and after immobilization, and the effect of different concentrations of GOD on the detection of glucose by the sensor was investigated. The experimental results showed that the proposed sensor surface out excellent performance in terms of sensitivity (0.8633 degree/(mg/ml)).

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.

High Sensitivity Coreless Fiber Surface Plasmon Resonance Sensor Based on Au Nano Biconical Particles

A coupling enhanced surface plasmon resonance (SPR) sensor based on coreless fiber is proposed. Compared with the common fiber, the coreless fiber is easier to perceive the changes of the external medium environment. As one-dimensional material with superior performance, the Au nano biconical particles are used to improve the sensor performance. Based on the finite element method (FEM), the electric field enhancement effect of the coupling between the SPR of the gold film and the Localized surface plasmon resonance (LSPR) of the Au nano biconical particles on the surface of the coreless fiber is analyzed, and the experimental results show that the Au nano biconical particles can improve the sensitivity. The sensitivity of the improved Au nano biconical particle sensor is 3514 nm/RIU, which is 64% higher than that of the traditional gold film SPR sensor, and the quality factor is increased by 24%. The new sensor based on Au nano biconical particles and gold film has a good application prospect in biosensor and chemical measurement.

A novel SPR sensor sensitivity-enhancing method for immunoassay by inserting MoS2 nanosheets between metal film and fiber

In this work, we proposed a novel surface plasmon resonance (SPR) sensitivity-enhancing method by adding MoS2 nanosheets between gold film and fiber (fiber-MoS2-gold film). And we apply it to the detection of human IgG protein. The sensor was fabricated by attaching MoS2 nanosheets to the U-shaped fiber surface and then covering a layer of gold film. The refractive index sensitivity of 6184.4 nm/RIU was achieved by the fiber-MoS2-gold film sensor which is 59 percent higher than the gold film SPR sensor and 25 percent than the fiber-gold film-MoS2 SPR sensor.The presence of MoS2 increases the absorption of light energy and excites a stronger SPR phenomenon. At the same time, since the monolayer MoS2 is a direct bandgap semiconductor, the absorbed light energy promotes the transfer of electrons, generates strong coupling on the gold film surface, enhances the surface electric field, and improves the sensitivity of the sensor. Biofunctionalized sensor detect human IgG with the limit of detection as low as 19.7 ng/mL. This work proposed a novel method for enhancing the sensitivity of SPR sensor, it owns a higher sensitivity and a lower LOD which has broad application prospects in measuring low concentration biological analytes.

Urea and creatinine detection on nano-laminated gold thin film using Kretschmann-based surface plasmon resonance biosensor.

This work investigates the surface plasmon resonance (SPR) response of 50-nm thick nano-laminated gold film using Kretschmann-based biosensing for detection of urea and creatinine in solution of various concentrations (non-enzymatic samples). Comparison was made with the presence of urease and creatininase enzymes in the urea and creatinine solutions (enzymatic samples), respectively. Angular interrogation technique was applied using optical wavelengths of 670 nm and 785 nm. The biosensor detects the presence of urea and creatinine at concentrations ranging from 50–800 mM for urea samples and 10–200 mM for creatinine samples. The purpose of studying the enzymatic sample was mainly to enhance the sensitivity of the sensor towards urea and creatinine in the samples. Upon exposure to 670 nm optical wavelength, the sensitivity of 1.4°/M was detected in non-enzymatic urea samples and 4°/M in non-enzymatic creatinine samples. On the other hand, sensor sensitivity as high as 16.2°/M in urea-urease samples and 10°/M in creatinine-creatininase samples was detected. The enhanced sensitivity possibly attributed to the increase in refractive index of analyte sensing layer due to urea-urease and creatinine-creatininase coupling activity. This work has successfully proved the design and demonstrated a proof-of-concept experiment using a low-cost and easy fabrication of Kretschmann based nano-laminated gold film SPR biosensor for detection of urea and creatinine using urease and creatininase enzymes.

Magneto-plamonic nanoparticles enhanced surface plasmon resonance TB sensor based on recombinant gold binding antibody

The magneto-plamonic nanoparticles (MPNs) have been employed to enhance the signal of surface plasmon resonance (SPR) spectroscopy to gain new insight into MPN and gold film SPR interaction. Three different morphologies MPNs (sphere, short spiky and long spiky) of Fe3O4@Au nanoparticles with good dispersion were synthesized and characterized carefully. A sandwich SPR immunosensor was constructed by immobilizing gold binding anti-CFP-10 (Ab1) onto a gold chip surface via Au-S bond firstly. Gold binding anti-CFP-10 (Ab2) captured on MPN surface was utilized to amplify the SPR signals specifically. Compared with spiky MPNs, the structure of spherical MPN, which concentrates the electric charge density and immobilize more Abs on its surface coverage, could enhance the electronic coupling effect significantly. Attribute to the super paramagnetism of MPNs, a facile solution route was fabricated to capture and separate analyte from the real sample by outside extend magnetic field. Implementation of MPNs results in 30-fold enlargement of the SPR signal at the limit of detection. To this end, an immunoassay is carried out that couples the specificity of antibody-antigen interactions with the high sensitivity based on spherical MPNs signal enhancement SPR.

Graphene/Au-Enhanced Plastic Clad Silica Fiber Optic Surface Plasmon Resonance Sensor

Owing to its large surface-to-volume ratio and good biocompatibility, graphene has been identified as a highly promising candidate as the sensing layer for fiber optic sensors. In this paper, a graphene/Au-enhanced plastic clad silica (PCS) fiber optic surface plasmon resonance (SPR) sensor is presented. A sheet of graphene is employed as a sensing layer coated around the Au film on the PCS fiber surface. The PCS fiber is chosen to overcome the shortcomings of the structured microfibers and construct a more stable and reliable device. It is demonstrated that the introduction of graphene can enhance the intensity of the confined electric field surrounding the sensing layer, which results in a stronger light-matter interaction and thereby the improved sensitivity. The sensitivity of graphene-based fiber optic SPR sensor exhibits more than two times larger than that of the conventional gold film SPR fiber optic sensor. Furthermore, the dynamic response analyses reveal that the graphene/Au fiber optic SPR sensor exhibits a fast response (5 s response time) and excellent reusability (3.5% fluctuation) to the protein biomolecules. Such a graphene/Au fiber optic SPR sensor with high sensitivity and fast response shows a great promise for the future biochemical application.

Graphene Enhances the Sensitivity of Fiber-Optic Surface Plasmon Resonance Biosensor

In this paper, a fiber-optic surface plasmon resonance (SPR) biosensor is presented, in which a sheet of graphene acting as a sensing layer is coated around the gold film. A theoretical study of the proposed fiber-optic biosensor has been carried out by applying four-layer modal, which shows that by incorporating a graphene sensing layer, the sensitivity of the proposed SPR fiber biosensor can be greatly enhanced than the conventional gold film SPR fiber sensors. The relationship between resonance wavelengths and sensitivity of the proposed graphene sensing layer-based SPR fiber biosensor with the number of sensing layer has also been studied.

Two-layered metallic film-induced surface plasmon polariton for fluorescence emission enhancement in on-chip waveguide

We demonstrate an enhancement of fluorescence emission due to bimetallic silver-gold film-induced surface plasmon wave extension. Rhodamine B (RhB) dyes were excited by the evanescent wave field produced from surface plasmon polaritons excited on metal-deposited sections along an embedded strip waveguide. Various silver-gold combinations were used to quantify for the evanescent field enhancement. The underlying silver yields better evanescent field enhancement, while the overlying gold ensures that the stability of the sensing surface is not compromised. In comparison to the conventional single gold film surface plasmon resonance (SPR) configuration, the two-layered metallic structure is capable of enhancing the surface plasmon polariton (SPP) evanescent field considerably, as verified experimentally by the ca. 4.0 times improvement in the RhB fluorescence emission. The compact waveguide structure and improved electric field probing depth can potentially be exploited for on-chip SPR--fluorescence excitation of less concentrated fluorophore-labelled biological and chemical analytes, with a capability of massively parallel processing for high throughput screening.

Optimised film thickness for maximum evanescent field enhancement of a bimetallic film surface plasmon resonance biosensor

A surface plasmon resonance (SPR) optical biosensor, with a bimetallic silver–gold configuration that integrates the better evanescent field enhancement of silver, the higher resolution in the reflectivity minimum of silver, and the high chemical resistance of gold is presented. In comparison to most commercial sensors which use single gold films, the enhanced evanescent field of this double-layer configuration at the analyte–metal interface enables the monitoring of biomolecular interactions that occur further into the analyte. In addition, it is shown theoretically and demonstrated experimentally that the double-layer configuration achieves better minimum reflectivity resolution than the single gold film SPR configuration. Finally, the higher stability and better biomolecules adhesion of the proposed configuration, as weighed against a single silver film, makes it be a much better option to be employed for biosensing applications.

Highly sensitive regenerable immunosensor for label-free detection of 2,4-dichlorophenoxyacetic acid at ppb levels by using surface plasmon resonance imaging

This work reports the characteristics of a newly developed optical surface plasmon resonance (SPR) immunosensor for direct, label-free detection of 2,4-dichlorophenoxyacetic acid (2,4-D). The analyte 2,4-D is conjugated with bovine serum albumin (BSA) protein, and the analyte–BSA conjugate is immobilized on to the thin gold-film SPR sensor chip mounted in a continuous flow system by simple physical adsorption. The thin biofilm of 2,4-D-BSA formed on the sensor chip is characterized a monomolecular layer of 2,4-D-BSA conjugate. Functionalization of sensor surface by physical adsorption of 2,4-D-BSA conjugate and followed immunoreaction of surface-bound 2,4-D-BSA with a monoclonal anti-2,4-D-BSA antibody (2,4-D-Ab) are studied by SPR angle interrogation method. The antibody 2,4-D-Ab immobilizes firmly through selective immunoreaction over the 2,4-D-BSA physisorbed SPR sensor chip. Flow of a general protein such as BSA or a non-related antibody over the 2,4-D-BSA immobilized sensor chip showed negligible response indicating the resistivity of the sensor surface to non-selective adsorption of proteins. The quantification of free 2,4-D is based on competitive immunoassay format, which is performed by co-injecting the sample and the monoclonal antibody 2,4-D-Ab over the 2,4-D-BSA physisorbed thin gold-film SPR chip and measuring the amount of specifically bound monoclonal antibodies. When free 2,4-D molecules present in the analyte solution, competition between free 2,4-D and surface-bound 2,4-D-BSA conjugate for binding to 2,4-D-Ab decreases the affinity interaction of the antibody with the sensor surface. The change in the SPR angle in the presence of 2,4-D is inversely proportional to the concentration of 2,4-D coexisting. Such an analytical system has been shown to be capable of detecting concentrations of 2,4-D in buffer as low as 0.5 ng/ml (ppb) with a response time of 20 min, and the 2,4-D detection is possible in the concentration range from 0.5 ng/ml to 1 μg/ml (ppm). We used in this investigation a simple SPR instrument, which is not equipped with either regulated flow system or temperature-controller and is similar to a portable SPR analyzer. After an immunoaffinity binding test, the active sensor surface can be regenerated again by simply flowing a chaotropic solution of pepsin (10 ppm in 0.2 M glycine–HCl buffer (pH 2.0)) in the flow system for just 2 min. This regeneration ability enables the achievement of as much as 20 measurement cycles of 2,4-D using a single 2,4-D-BSA conjugate immobilized SPR sensor chip with good reproducibility.