Dr. Silvio Rodriguez Physical Chemistry
Professor
E-mail: srodriguez@pacific.edu
Work phone: (209) 946-2598
Office Location: CR #118
Personal Link: http://web.pacific.edu/x13823.xml
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Research Interests: Energy transfer in multicomponent systems; Environmental chemistry
My present research interests lie mainly in the area of energy transfer in two and three component systems in fluid and solid media. For example, we have studied the multicomponent system coumarin 1 – fluorescein – rhodamine B in ethanol at room temperature. In the appropriate concentration ranges, upon the excitation of coumarin 1 at 377 nm, the ternary dye mixture solution emitted simultaneously with three bands centered at 443, 528, and 575 nm, respectively. The analysis of the data seems to indicate that there is significant energy transfer between these three dyes and that the main contribution corresponds to the Förster nonradiative mechanism. The critical transfer distances between each of two of the three components were calculated to be 48.4 Å for the coumarin 1 / fluorescein pair, 42.2 Å for the cooumarin 1 / rodamine B pair and 65.5 Å between fluorescein and rhodamine B dyes. The system can potentially be used to obtain three primary outputs at different wavelengths in a dye laser system.
I am also interested in environmental chemistry. Absorption and emission spectroscopy are used to determine speciation and fate of contaminants under conditions that simulate the environment.The extent to which aquatic biota are exposed to a toxicant such as a pesticide is largely controlled by its aqueous solubility. Solubility measurements can also be used to predict or extrapolate such parameters as transfer coefficients from residence in soils into runoff and ground water and systemic penetration into aqueous tissues. In addition, solubilities are of thermodynamic interest since they can provide information fundamental in understanding hydrophobic interactions and in calculating the transfer properties of solutes between various solvents. Solubility measurements can be affected by temperature, pressure or by the ionic strength of the dissolving medium. The magnitude of this effect can be calculated by using an empirical relation developed by Setchenov.
In this laboratory we have studied naphthalene and the pesticide 1-naphthyl-N-methylcarbamate as a function of temperature, pressure, and ionic strength of single electrolytes, combinations of electrolytes and seawater. We have determined Setchenov parameters as a function of temperature, pressure and ionic strength. We have also used different models in order to predict the Setchenov parameters for any given pair of electrolyte - nonelectrolyte cosolutes. Most thermodynamic models are based on the Tamman-Tait-Gibson treatment of electrolyte solutions which has been successful in the prediction of properties of aqueous electrolyte solutions and seawater.
Representative Publications
Pihong Zhao and Silvio Rodriguez, "Fluorescence Spectroscopic Studies on the Multi Component System Coumarin 1 / Fluorescein / Rhodamine B in Ethanol." Journal of Fluorescence Spectroscopy, 7, 121 (1997)