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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]

In this paper, indium tin oxide (ITO) is considered as an alternative plasmonic material beyond conventional plasmon generating metal. A total of 150-nm-thick ITO film-based Kretschmann configuration is demonstrated in NIR region. Minimum possible reflectance with optimum FWHM of resonance plot is the essential criteria for the incident angle selection of the said structure to increase the sensitivity and improve the performance of SPR biosensors in wavelength interrogation mode. Reflectance, phase, and field enhancement curves have been studied for different gaseous samples, and corresponding wavelength sensitivity has been calculated for the change of refractive index of the sample in the order of two. Differential resonance parameters have also been studied which are found to provide increased sensitivity. Theoretical simulation-based results validate that the proposed sensor can provide higher sensitivity by measuring the differential phase. [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]