Unconventional Reaction Media: A Solvent-Based Discovery Lab for First-Year Undergraduates
A general chemistry laboratory that illustrates the effectiveness and benign nature of unconventional reaction media is outlined in a three step procedure: 1) a solventless condensation reaction between two solids, 2) an oxidative coupling reaction in the presence of a liquid carbon dioxide solvent, and 3) the synthesis of an organic-transition metal complex in aqueous media. This laboratory exercise is designed to illustrate the advantages and utility of alternative reaction media through a straightforward procedure with visually qualitative results while further exploring the function of solvents in the synthetic process. The laboratory experiments address waste prevention and the use of innocuous auxiliary substances, thus also providing students with an excellent introduction to several principles of green chemistry.
Dye Sensitization of TiO2 Single Electrodes
Colin Bradley II - Chemistry, Honors Scholar Program
Solar power is the most widely available and abundant source of energy on the planet. Using solar power on a large scale to meet energy needs would require a significant reduction in the cost of solar energy conversion devices. Dye sensitized solar cells (DSSC) made of inexpensive large band-gap semiconductors (such as TiO2) are being investigated to fulfill this need. In this study, TiO2 single crystals were sensitized with poly(arylene ethylene) conjugated polyelectrolytes (CPEs), which allowed for electron injection into the semiconductor conduction band and generation of small (nA) photocurrent. The concentration of sensitizer was serially diluted and the photocurrent was measured at varied concentrations. A mathematical model was developed to relate photocurrent to concentration while considering the saturation of sensitizer on the TiO2 substrate. The photocurrent was compared to a ruthenium-based dye, N3. Higher photocurrent was generated using electrodes sensitized with CPEs, but electrodes sensitized with N3 dye had a wider range of absorption than those sensitized with CPEs. Additionally, the CPEs were less robust than N3 dye, which has consequences for use in a DSSC.