Giovanni Meloni, University of San Francisco
During the September 1, 2011 – August 31, 2012 period we were successful in carrying out experiments, collecting data for several systems at the Advanced Light Source (ALS) of Lawrence Berkeley National Laboratory. Specifically, we used the multiplex time- and energy-resolved photoionization mass spectrometer located at the Chemical Dynamics Beamline. We also performed experiments at the Swiss Light Source (SLS) in Switzerland, where we received beamtime allocation to study some biofuel molecules.
Using the multiplex time- and energy-resolved photoionization mass spectrometer at the ALS in conjunction with pulsed-photolytic Cl-initiated oxidation we investigated the low temperature (550-750 K) and low pressure (8 Torr) combustion of isopentanol, which was published this year. Formation of isopentanal (3-methylbutanal) and unsaturated alcohols (including enols) associated with HO2 production was observed. Cyclic ether channels were not observed, although such channels dominate OH formation in alkane oxidation. Rather, products were observed that correspond to formation of OH via β-C–C bond fission pathways of QOOH species derived from β- and γ-hydroxyisopentylperoxy (RO2) radicals. Isomer-resolved branching ratios were deduced, showing evolution of the main products from 550 to 750 K, which can be qualitatively explained by the dominance of RO2 chemistry at lower temperature and hydroxyisopentyl decomposition at higher temperature.
Mesitylene, tert-amyl methyl ether, and ethyl tert-butyl ether oxidations using different photolytic initiators are currently under study. We are also preparing a scientific paper on the measurement of absolute photoionization cross sections of selected furans and lactones.
Three graduate MS Chemistry students and three undergraduates, two Physics majors and one Chemistry major, were supported during summer 2012 with stipends. One of the Physics major is a Chemistry minor, and the other one is a Chemical Physics minor. The undergraduates worked for a 10-week period. In addition, one MS student and one undergraduate had the financial support to travel to the SLS in Villigen, Switzerland to carry out experiments, which are a new scientific direction we are interested in pursuing. We studied the photoionization behavior of some biofuel molecules via imaging photoelectron photoion coincidence (iPEPICO) spectrometry.
I have been highly motivated in engaging undergraduate students in my research program. Even though they perform experiments and are actively involved in the data analysis, undergraduates do not possess the in-depth knowledge required to put results in context. Therefore, I feel that working with undergraduates is truly a service to the department and the society, in general, making them more aware of how research can change our world. During my appointment at the University of San Francisco I have accepted seven undergraduates, three this past summer. The enthusiasm of an undergraduate can be contagious, not only for me but also for my graduate students. Three undergraduates who have worked in my group were accepted into PhD programs in Chemistry, at UC Davis, University of Texas Austin, and Yale. All my undergraduate students also participated in our experiments at the Advanced Light Source in Berkeley and became familiar with the instrumentation and safety procedures needed to operate in a Department of Energy facility.
This ACS-PRF grant gave me the opportunity to branch out in a different experimental technique (iPEPICO) with the work performed at the SLS, allowing me to further develop my scientific research. I recently reapplied for beamtime allocation at the SLS for next summer where I plan to go with two students for a total of 10 days. We proposed to investigate the pyrolysis behavior of selected biofuels. This international experience for my students is priceless and possible only thanks to this grant. In addition, the funds permitted the purchase of three computers much needed for data analysis and continuous training of my students. From the experiments at the ALS four posters were presented at several venues: the “59th Annual Western Spectroscopy Association Conference,” Asilomar Conference Center, Pacific Grove, California, January 25 – 27, 2012 (“Investigation of 2-Me-THF and 2,5-DMF Oxidation Using Synchrotron Photoionization Mass Spectrometry,” Matthew McManus (graduate student, awarded graduate student scholarship), David L. Osborn, Craig A. Taatjes, and Giovanni Meloni); the “243rd ACS National Meeting,” San Diego, California, March 25-29, 2012 (“Investigation of Low Temperature Oxidation Reactions of Methyl Butyrate and Ethyl Butyrate Using Photoionization Mass Spectrometry,” Joseph Czekner (graduate student), David L. Osborn, Craig A. Taatjes, and Giovanni Meloni; and “Low Temperature Combustion of Ethyl Tert-Butyl Ether Characterization Using Synchrotron Photoionization Mass Spectrometry,” Katherine Catani (undergraduate student), Martin Y. Ng (graduate student), David L. Osborn, Craig A. Taatjes, and Giovanni Meloni); the “2012 Northern California ACS Undergraduate Research Symposium,” Oakland, California, April 28, 2012 (“Low Temperature Combustion of Ethyl Tert-Butyl Ether Characterization Using Synchrotron Photoionization Mass Spectrometry,” Katherine Catani (undergraduate student), Martin Y. Ng (graduate student), David L. Osborn, Craig A. Taatjes, and Giovanni Meloni). Of particular pride is the award of best Physical Chemistry poster to one of my graduate student, Joseph Czekner, at the 243rd ACS National Meeting in San Diego in March 2012. He competed against 130 presenters from institutions all over the US, including major PhD granting schools.