Strontium Barium Niobate (SBN) has been known for its highest electro optic coefficient amongst the known photorefractive materials. SBN thin films were prepared using Pulsed Laser Deposition (PLD) technique on the conducting LSCO coated Si Substrate and its tetragonal tungsten bronze structure was confirmed using X-ray diffraction technique. Surface Plasmon Resonance (SPR) technique has been effectively used by exploiting the SBN thin film in Otto configuration using prism coupling technique. The SPR reflectance curves for prism/air-gap/gold/SBN/LSCO/Si system were obtained by varying the applied electric field from 0 to 150kV/cm. A continuous increase in minimum reflectance of SPR curves with increase in the electric field across the SBN thin film has been obtained indicating variation in optical properties of SBN thin film on application of electric field. This increase in reflectance was attributed to the change in propagation constant of wave vector due to the change of optical properties of the film under consideration. The resonance condition changes hence the SPR minimum reflectance angle and position changes.
The present report addresses the application of surface plasmon resonance (SPR) phenomenon for urea sensing. The former promises a high sensitivity, label-free detection, and real-time information by monitoring the refractive index change at the metal–dielectric interface. In the present report, a highly sensitive urea biosensor has been developed by integrating a ZnO thin film matrix with the SPR technique. Kretschmann configuration has been used to excite the surface plasmon (SP) modes at the ZnO–metal (gold) interface using an indigeneously developed table top SPR measurement setup. Urease (Urs), the urea-specific enzyme, has been immobilized on the surface of ZnO thin film by physical adsorption technique. The SPR reflectance curves were recorded for the prism/Au/ZnO/Urs system in angular interrogation mode with phosphate-buffered saline (PBS) solution as the liquid media. The SPR resonance angle is found to be shifted toward a lower angle from 49.1 to 42.0 deg with an increase in the urea concentration (0 to 300 mg/dl) in the PBS solution. The developed sensor (prism/Au/ZnO/Urs) is found to be highly sensitive [sensitivity=0.039 deg/(mg/dl) or 203 deg/RIU] with detection accuracy of 0.045(deg)−1.
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