Spectroelectrochemistry is a well-known technique used to achieve multimode selectivity in one sensor. The sensor usually consists of an optically transparent electrode (OTE) coated with a charge selective polymer film. These polymer films are employed to pre-concentrate analyte at the OTE surface so that it can be sufficiently detected optically through electrochemical modulation. OTEs such as Indium Tin Oxide (ITO) have been used extensively in this method but little is known about the applicability of such sensors using other OTE materials, such as Boron Doped Diamond (BDD). One distinct advantage of BDD OTEs over ITO OTEs is their significant increase in sensitivity for organic compounds, such as para-aminophenol and hydroquinone. With this, we have developed absorption and fluorescence-based sensing methods with a BDD OTE coated with a sulfonated ionomer film, Nafion. This is demonstrated with tris(2,2’-bipyridyl)ruthenium(II) ion [Ru(bpy)32+] using an attenuated total reflectance (ATR) flow cell setup for both absorbance and fluorescence. With a Nafion coated BDD optically transparent thin layer electrode (OTTLE), we developed a fluorescence based sensor for a common polyaromatic hydrocarbon (PAH), 1-hydroxypyrene (1-pyOH), achieving a detection limit of 80 nM (17 ppb). Using these techniques, we were able to manifest new sensing applications while broadening the use of spectroelectrochemistry, OTEs, and BDD as an electrode material.