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Surface plasmon resonance (SPR) is an interfacial phenomenon, and the plasmonic sensors are based on the optical excitation of the collective oscillations of free electrons at a metal-dielectric interface. Here, we present the new development of an incoherent broadband (IBB)-SPR probe combining the wavelength interrogation technique with polarization-multiplexing (PM). The performance characteristics of the so-called PMIBB-SPR strategy was validated for the detection of nonenzymatic aqueous urea samples as a representative example for plasmonic sensing with an excellent wavelength and phase sensitivities of 0.1363 nm/mM and 10.34597 mM/deg, respectively. We further explored the missing link between plasmonic polariton resonance (PPR) and polarization modulation via the measurements of the Stokes parameters of the reflected light. This deepens our understanding of the fundamentals of polarization-multiplexed SPR phenomenon at the interface. This study thus paves the way to develop a new-generation analytical technique with the aim of tracking various real-time chemical and biological molecular interactions occurring at the interfaces.

We employed the wavelength-interrogated surface plasmon resonance (SPR) method to characterize the real-time kinetics of urea-urease hydrolysis reaction in response to a CO2-free N2 environment and CO2-enriched ambient reaction medium. We established that a simple label-free SPR probe could accurately extract kinetic parameters from the nature of the sharp jump of the SPR wavelength shift in the reaction profile. The kinetic analysis showed that CO2 production increases with increasing reaction time irrespective of CO2-free N2 or CO2-enriched reaction environment. We also explored the essential insights into the isotopic fractionations of 12CO2, 13CO2, 12C18O16O in the reaction medium utilizing integrated cavity output spectroscopy. The plasmonic system measured the reaction rate in the order of 10-7 M/s for urea species in the presence of the urease enzyme. This study deepens our understanding of plasmonic-based enzymatic urea hydrolysis in real time and opens a new way to quantify chemical reaction kinetics for various other systems. This is the first detailed experimental investigation of the real-time kinetics of urea-urease hydrolysis reaction exploiting wavelength-interrogated surface plasmon resonance method in response to produced CO2 in the CO2-free N2 environment and CO2-enriched ambient reaction medium utilizing integrated cavity output spectroscopy. [ABSTRACT FROM AUTHOR]

Here, we perform a theoretical investigation of the impact of film thickness and incident angle on the surface plasmon resonance spectra for annealed and postannealed Ga-doped ZnO (ZnO:Ga) in a 3-phase Kretschmann configuration. A detailed comparative study has been performed to determine the optimum configuration to be utilized for sensing applications. Though both films are found to support plasmonic excitation for thickness below 200 nm, detection accuracy and sensitivity calculations from the resonance plots simulated in the MATLAB environment reveal that the preference of one over the other should be in accordance with the concerned application. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR)-based differential phase analysis has been presented. Real as well as complex plane analysis of resonance parameters have been undertaken for the optimum selection of metal thicknesses in a bimetallic SPR configuration working under both angular and spectral regime. Theoretically, we can characterize the aqueous solution in terms of this differential phase variation due to the variation of sample parameters such as concentration and temperature. In this respect, two case studies, namely, concentration of hemoglobin in human blood and sensing of temperature of water have been demonstrated and proposed theoretically. By monitoring the change of differential phase, proposed approach leads to a very sensitive measurement of concentration and temperature. [ABSTRACT FROM AUTHOR]

Split Mach–Zehnder interferometer is proposed for demonstration of phase modulation of p- and s- polarized beams in a surface plasmon resonance based phase sensitive interference imaging platform. Significant phase change has been observed in Al coated prism based SPR configuration for p-polarized beam, whereas practically no phase change occurs for s-polarized beam. Qualitative analysis of SPR modulated interference fringes also validates the observed effects. A proposed Split Mach–Zehnder set up is shown for simultaneous sensing of two different samples. [ABSTRACT FROM AUTHOR]

We report a novel scheme for sensitivity-enhanced liquid phase cavity ring-down spectroscopy (CRDS) exploiting the two-dimensional transition metal dichalcogenides (2D-TMDCs) based surface plasmon resonance (SPR). We investigated the performance of the proposed sensing scheme by monitoring water isotopologues i.e. D 2 O (heavy water) and H 2 O on the SPR chip utilizing a simulation-based characteristics transfer matrix method. The cavity-enhanced SPR coupled with 2D-TMDCs is employed to detect D 2 O from distilled (DI) water with good time response. This proposed approach exhibited minimum sensitivity up to 448 ns/RIU with 4-layers of molybdenum disulfide (MoS 2) and maximum sensitivity up to​ 604 ns/RIU with 4-layers of tungsten diselenide (WSe 2). Moreover, dependence of cavity-finesse and chip-sensitivity on the 2D-nanomaterials suggests that SPR-CRDS is a new-strategy for the applications of plasmonic chemical sensing in the condensed phase with absorbance of the order of 10−11. • Coupling cavity ring-down spectroscopy and surface plasmon resonance with 2D-TMDC to probe condensed-phase molecules. • Performance of the proposed scheme was tested by monitoring various water isotopologues. • Various 2D materials were employed to increase the ring-down sensitivity. [ABSTRACT FROM AUTHOR]

Experimental investigation on surface plasmon resonance (SPR) modulated interference has been proposed and demonstrated under radially sheared environment with the help of a birefringent lens. SPR modulated interference images captured by a charged couple device have been demonstrated in two different analyzing regime, namely, using an analyzer and using a Wollaston prism, the later being advantageous for the simultaneous observation of p- and s-polarized contribution towards SPR. We also report the analysis of the interference imaging for the two substrate materials and also for the two analytes in order to show the substrate-sample dependency of SPR. Moreover, phase dependent resonant behavior, together with the analysis of amplitude reflection co-efficient in complex plane, has been theoretically simulated and discussed in support of the present experimental investigation, which can be well utilized for biological and chemical sensing. [ABSTRACT FROM AUTHOR]

Metallic film thickness optimization in mono- and bimetallic plasmonic structures has been carried out in order to determine the correct device parameters. Different resonance parameters, such as reflectivity, phase, field enhancement, and the complex amplitude reflectance Argand diagram (CARAD), have been investigated for the proposed optimization procedure. Comparison of mono- and bimetallic plasmonic structures has been carried out in the context of these resonance parameters with simultaneous angular and spectral interrogation. Differential phase analysis has also been performed and its application to sensing has been discussed along with a proposed interferometric set-up. [ABSTRACT FROM AUTHOR]