PRISM-FREE BROADBAND COUPLING APPROACH FOR SPECTROELECTROCHEMICAL CHARACTERIZATION OF SURFACE-IMMOBILIZED MOLECULES

摘要

Indium-tin oxide (ITO)-coated quartz plates with tapered ends have been utilized as stand alone waveguides for spectroelectrochemical characterization of immobilized dyes and protein films. Light coupling into the core is achieved through a 60-degree tapered end on both sides of the waveguide that conveniently eliminates the need for a pair of coupling prisms. This is a significant improvement in our slab optical waveguide (SOWG) platform that utilizes a pair of LaSF_8 prisms for light coupling into the waveguide. We observed that the prism coupling approach is limited only to within a certain period of time owing to the volatility of the coupling liquid used to span the prism/waveguide gap. The new prism-free geometry gives a more stable response with time and transmits a broad range of wavelengths from about 350 up to 750 nanometers. Using a representative dye, methylene blue, and a model protein, cytochrome c, the efficacy of the tapered end coupling approach in studying surface-bound molecules is established and results are reported in this paper.