A method was developed to access the interior of light-guiding structures in order to exploit the enhanced sensing potential of the highly confined electromagnetic field distributions, located within the core of a waveguide. The work presented in this thesis explores therefore the possibilities of optical waveguide spectroscopy utilising transparent mesoporous thin-film waveguides deposited on top of athin gold layer. These multi-layer assemblies are employed in a prism-coupling attenuated total internal reflection (ATR) configuration. The angular read-out of the reflected light intensity allows label-free detection schemes with high sensitivity to changes of the dielectric environment in the case of the presence of analyte molecules within the probing region. This optical waveguide spectroscopy technique has been used to study the real-timediffusion of Ruthenium 535-bisTBA (N-719) dye into mesoporous nanocrystalline titaniumdioxide films. The porous films were prepared on top of gold substrates and prism coupling was used to create a guided wave in the nanocrystalline film. Dying was carried out by bring the film into contact with a 3 x 10-4 moldm-3 dye solution and using optical waveguide spectroscopy to monitor the change in both the refractive index and theextinction coefficient of the nanoporous layer as dye diffused into the porous network. Dyeuptake in a 1.27 μm film was slow with the refractive index of the film still increasing after 22 hours.

A broadband coupling approach applied to a single mode, sol-gel, planar integrated optical waveguide (IOW) was used to create a multichannel attenuated total reflection (ATR) spectrometer. Initial attempts to create an achromatic coupling element for sol-gel waveguides, based upon previous work applied to vacuum deposited glass devices, did not lead to an easily achievable design. Instead a simplified, non-achromatic approach based upon impinging an incident light beam with a large numerical aperture onto an incoupling prism was used. This simplified broadband coupling approach was used to create a sol-gel IOW-ATR spectrometer that transmitted light down to at least 400 nm, and produced a measurable bandwidth of ~ 250 nm; both phenomena are marked improvements upon the capabilities of previously reported devices. An experimental demonstration of this device proved it capable of measuring the visible spectrum of a thin film of horse heart cytochrome c adsorbed to the sol-gel surface at a submonolayer coverage. The broadband spectral capabilities of this sol-gel device were also used to experimentally validate a new method for determining the angular orientation of molecules bound to an arbitrary waveguide surface. In addition to the sol-gel IOW work, the simplified broadband coupling approach was applied to a previously reported multilayered electroactive waveguide device, which was used to collect electrically modulated, broadband spectra for thin films of cytochrome c, as well as a dicarboxyferrocene moiety. Both of these IOW-ATR spectrometers represent improved tools for probing the near-surface chemical environments of molecular assemblies.

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