Enhanced sensitivity of wavelength modulated surface plasmon resonance devices using dispersion from a dye solution

A dispersion technique for enhancing the sensitivity of wavelength modulated surface plasmon resonance devices is presented. Using the dye, 1,1'3,3,3',3'-hexamethylindodicarbocyanine (HIDC) iodide, which contains a strong absorption band centered in the dynamic range of the surface plasmon resonance coupling wavelength, the sensitivity to the bulk solution refractive index and the detection of analyte near the sensor surface is increased. A quantitative theory for the enhancement effect is derived from the fundamental equation for surface plasmon resonance. Experimental results are presented for a surface plasmon resonance fiber optic sensor. As much as a Lt-fold enhancement in the sensitivity of the surface plasmon resonance response was obtained for bulk sucrose solutions, and a 2-fold enhancement was obtained for binding of proteins to the sensor surface. The theoretical analysis shows that it should readily be possible to obtain significantly greater enhancements of the sensitivity. (C) 1999 Elsevier Science S.A. All rights reserved.