Temperature-dependent sensitivity of surface plasmon resonance sensors at the gold-water interface

Instrumental performance and sensitivity of surface plasmon polariton or resonance (SPR) sensors are crucially affected by ambient temperature fluctuations. Apart from temperature-induced opto-mechanical displacements, resonance conditions and associated output quantities vary, due to thermo-physical properties of optical components, like prism, semi-transparent metal-film and aqueous analyte solution. The variation of instrumental sensitivity S as function of environmental temperature has been exploited experimentally in the temperature region 275 K < T < 320 K. A compact, robust commercial SPR device has been used, operating in the angular interrogation mode. At temperature < 300 K, S^θ steadily deteriorates from 120°/RIU to 30°/RIU. For comparison, the thermal device characteristics also has been evaluated theoretically within the range 273 K < T < 370 K for both, angular interrogation mode (AIM) and wavelength interrogation mode (WIM). Fresnel's equation system and established analytical sensitivity expressions have been elaborated, and differences assigned to simplifications in the analytical form. An appropriate thermo-physical data set of experimentally verified optical materials parameters n (λ, T) and ε (λ, T) for all, BK7 glass prism, gold metal film, and aqueous analyte has been used. A singularity has been identified in the simulations near the freezing point of water, while a soft transition appears in the experiment. Towards higher device temperatures at 300 K < T < 370 K, S^{θ, λ} decreases weakly. The effect is more pronounced at shorter wavelength ≤550 nm, and in the wavelength interrogation mode. A steady increase towards higher T was observed for the SPR-line broadening parameter in the AIM, but a distinct maximum resolved at 305 K for wavelength interrogation.