Professor of Chemistry
Classes for Spring 2013
Light emitting systems
One of our main interests is studying light emitting systems using photo-, chemi- and electrogenerated chemiluminescence (ECL) with an emphasis on ECL. ECL is the process where species generated at electrodes undergo electron transfer reactions to form excited states that emit light. Application of a voltage to an electrode in the
presence of an ECL luminophore such as Ru(bpy)32+ (where bpy = 2,2’-bipyridine) results in light emission and allows detection of the emitter at very low concentrations (ï‚£10-11 M). By employing ECL-active species as labels on biological molecules, ECL is being used in commercial applications for immunoassays and DNA analyses.
Our goals are to discover new light emitting systems, study and develop new applications, improve the sensitivity and selectivity, and better understand the mechanisms of the light-generation and light-emission.
For example, we have studied the electrochemistry, spectroscopy (e.g., UV-Vis absorbance), photoluminescence and ECL of a series of ortho-metalated iridium(III) systems (e.g., Ir(ppy)3 where ppy = 2-phenylpyridine). These compounds often have high photoluminescent efficiencies, long excited state lifetimes, and readily accessible excited states. A series of complexes have been shown to undergo ECL in aqueous and nonaqueous solvents at reasonable voltage and pH levels and to give a wide color range of emission (red, green and blue). This raises the possibility of using these as internal standards and for the analysis of multiple analytes in the same solution. Other ECL emitters that have been recently studied incorporate metals such as osmium, copper, lead, ruthenium and aluminum. Organic ECL systems have also been explored.
We continue to explore analytical methods based on ECL for the detection of environmental pollutants (e.g., phenols, surfactants and heavy metal ions), for the determination of small amounts of DNA, and to study the surfactant effect on ECL where large increases in ECL emission are observed in the presence of nonionic surfactants. We are also incorporating light emitters onto carbon nanotubes to explore the changes that occur upon binding.
Laboratories and Case Studies
Another focus has been the development of laboratories and chemical demonstrations. Representative examples include peer-led team learning labs that incorporate semester long projects, an ECL laboratory for use in instrumental analysis, and incorporating a commercial ECL analyzer in lower division courses including those for non science majors. Recently, a laboratory was developed to detect DNA using voltammetry and spectroscopy was used to generate quality control charts. We are also exploring the use of a semi-automatic titration system in these courses. Chemical demonstrations have included ECL and chemiluminescence from inorganic complexes.
Case studies are stories that convey an educational message. They also help shift the focus from the ‘sage on the stage’ model to active student engagement in the classroom. We have been using case studies available from the National Center for Case Study Teaching in the Sciences, and are currently developing our own case studies. For example, one under development titled “Can you supersize my cancer please?” explores the presence of acrylamide in fried foods from both the public perception and scientific view points.