A novel idea of utilizing transition metals in surface plasmon resonance detection has been verified both theoretically and experimentally. Different metal films were covered with increasing numbers of monomolecular layers of cadmium behenate and surface plasmon resonance curves were recorded for each additional layer. Results of the measurements show that it is the position of the ‘down-way’ slope of the resonance curve that is most affected by changes in the resonance conditions, not the width of the whole curve nor the position of the minimum. The angle of the slope shifts to higher values when the number of monomolecular layers increases. Thus, the sensitivity of the system depends on the first derivative of the resonance curve (‘steepness’ of the slope). For example, detection sensitivities obtained with such transition metals as palladium are comparable with those obtained with gold. These results were confirmed by computer simulations of the surface plasmon resonance phenomenon. For calculations the Fresnel reflections equations for multilayered media were used, with exact solutions obtained numerically.
Sadowski, J., Lekkala, J., & Vikholm, I. (1991). Biosensors based on surface plasmons excited in non-noble metals. Biosensors & Bioelectronics, 6(5), 439-444. https://doi.org/10.1016/0956-5663(91)87009-Z