Catálogo de Investigaciones | 2011-2012

137 Catálogo de Investigaciones | Pontificia Universidad Católica de Puerto Rico “Adsorción de Compuestos Quinoides en Superficies Monocristalinas de Platino: Nuevas Sondas Moleculares Espectroelectroanalíticas” This Doctoral Thesis explores, from an analytical standpoint, the use of quinoidal compounds as molecular probes sensitive to the atomic structure of platinum electrode surfaces. The work is presented in the modality of a compendium of publications. For the first time, the direct electrochemical detection of the reductive desorption of ad layers derived from, I ,4- dihydroxybencene or 1,2-dihydroxybencene, is reported at well-ordered Pt (111) single crystal electrodes. In situ spectroelectrochemical techniques were used to study and to characterize the electrochemical reactivity of these molecular adlayers at Pt(111) electrode surfaces. The nature of the adsorbed and solution species was confirmed in situ using Substractively Normalized Intensity Fourier Transform InfraRed Spectroscopy. It was determined that both molecules chemisorb oxidatively generating the corresponding quinones. The adsorbed molecules are oriented with a vertical component with respect to the surface of the Pt( 111) electrode. The reductive desorption of the adsorbed molecules takes place reversibly generating the original reduced state of the molecules in solution. A novel electroanalytical strategy was developed, contrasting voltammetric results under hydrodynamic conditions imposed by using hanging meniscus rotating disk electrodes, and was used as an additional tool to corroborate the desorption/adsorption model proposed for the redox processes understudy. In addition, the work presented demonstrates that the reductive desorption redox process for 1, 4-dihydroxybencene or hydroquinone can be used to detect well-ordered surface domains with specific atom arrangements. The process takes place selective at well-ordered Pt(111) domains while being precluded in other surfaces such as well- ordered Pt(100) and Pt(110) basal planes, as well as disordered Pt(111). The hydroquinone electrochemical reactivity was systematically studied and the results demonstrate that it is possible to extrapolate the information obtained at single crystal Pt basal planes to understand the electrochemical behavior of these molecules at more complex electrode surfaces such as stepped Pt surfaces and preferentially oriented Pt nanoparticles. The presence of well-ordered (111) facets were detected and demonstrated to exist at preferentially oriented Pt nanoparticles. dra. margarita rodríguez-lópez mentor dr. juan m. feliú co-director dr. arnaldo carrasquillo, jr. palladium anticancer resistance