Surface plasmon resonance for sensing phase changes in opaque materials

Abstract

The accurate and real-time detection of phase changes of opaque materials during different physical, chemical and mechanical processes is relevant in various industrial applications. In this dissertation, detection and monitoring of refractive index variations of opaque materials during phased changes using prism-based surface plasmon resonance (SPR) sensors have been reported. Using the Kretschmann configuration of SPR, a sensitive refractive index sensor has been designed which can relate the SPR absorption peak wavelength of the sensor to the sample refractive index. In particular, the phase changes of asphaltene in crude oil during its deposition, the role of inhibitors on the deposition rate and depth of asphaltene, and also the phase change of resin composite during curing process via UV light in dental applications have been studied. Using our SPR sensor for crude oil depositions, we can detect 142 nm SPR peak shift from 553±0.6 nm to 695±0.6 nm, for a 0.197 change in refractive index (RI) from 1.389 to 1.586. This is used to show crude oil RI varies from a RI value of 1.505 (SPR peak wavelength of 601 nm) in neat crude oil fluid to a RI value of 1.521 (SPR peak wavelength of 614 nm) when asphaltenes deposited on the surface of the sensor completely. In dental application, we similarly show that resin composite SPR peak wavelength shifts from 617±0.6 nm before UV curing to 633±0.6 nm after a complete UV curing. Furthermore, we used the matrix formalization modelling approach for calculating the theoretical SPR response from our sensor and it was in excellent agreement with our observed experimental results. Our findings show the potential of SPR sensors in various industrial and scientific applications, in particular applications in dentistry and oil industries for online real-time monitoring.