Anderson, United States
Anderson, United States

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Laskin J.,Chemical and Materials science Division | Eckert P.A.,Pacific Northwest National Laboratory | Roach P.J.,Chemical and Materials science Division | Heath B.S.,Pacific Northwest National Laboratory | And 2 more authors.
Analytical Chemistry | Year: 2012

Reactive nanospray desorption electrospray ionization (nano-DESI) combined with high-resolution mass spectrometry was utilized for the analysis of secondary organic aerosol produced through ozonolysis of limonene (LSOA). Previous studies have shown that LSOA constituents are multifunctional compounds containing at least one aldehyde or ketone groups. In this study, we used the selectivity of the Girard's reagent T (GT) toward carbonyl compounds to examine the utility of reactive nano-DESI for the analysis of complex organic mixtures. In these experiments, 100 μM GT solutions were used as the working solvents for reactive nano-DESI analysis. Abundant products from the single addition of GT to LSOA constituents were observed at GT concentrations in excess of 10 μM. We found that LSOA dimeric and trimeric compounds react with GT through a simple addition reaction resulting in formation of the carbinolamine derivative. In contrast, reactions of GT with monomeric species result in the formation of both the carbinolamine and the hydrazone derivatives. In addition, several monomers did not react with GT on the time scale of our experiment. These molecules were characterized by relatively high values of the double bond equivalent and low oxygen content. Furthermore, because addition of a charged GT tag to a neutral molecule eliminates the discrimination against the low proton affinity compounds in the ionization process, reactive nano-DESI analysis enables quantification of individual compounds in the complex mixture. For example, we were able to estimate for the first time the amounts of dimers and trimers in the LSOA mixture. Specifically, we found that the most abundant LSOA dimer was detected at the ∼0.5 pg level and the total amount of dimers and trimers in the analyzed sample was ∼11 pg. Our results indicate that reactive nano-DESI is a valuable approach for examining the presence of specific functional groups and for the quantification of compounds possessing these groups in complex mixtures. © 2012 American Chemical Society.

Lin J.,Vanderbilt University | Lin J.,Vanderbilt Institute of Nanoscale Science and Engineering | He W.,Vanderbilt Institute of Nanoscale Science and Engineering | He W.,Vanderbilt University | And 14 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Through thermally annealing well-arrayed, circular, nanoscale thin films of gold, deposited onto [111] silicon/silicon dioxide substrates, both solid and hollow gold particles of different morphologies with controllable sizes were obtained. The circular thin films formed individual particles or clusters of particles by tuning their diameter. Hollow gold particles were characterized by their diameter, typically larger than 400 nm; these dimensions and properties were confirmed by cross-section scanning electron microscopy. Hollow gold particles also exhibited plasmonic field enhancement under photoemission electron microscopy. Potential growth mechanisms for these structures were explored. © 2013 American Chemical Society.

Bateman A.P.,University of California at Irvine | Laskin J.,Chemical and Materials science Division | Laskin A.,Pacific Northwest National Laboratory | Nizkorodov S.A.,University of California at Irvine
Environmental Science and Technology | Year: 2012

The applicability of high-resolution electrospray ionization mass spectrometry (HR ESI-MS) to measurements of the average oxygen to carbon ratio (O/C) in secondary organic aerosols (SOAs) was investigated. Solutions with known average O/C containing up to 10 standard compounds representative of low-molecular-weight SOA constituents were analyzed and the corresponding electrospray ionization efficiencies were quantified. The assumption of equal ionization efficiency commonly used in estimating O/C ratios of SOAs was found to be reasonably accurate. We found that the accuracy of the measured O/C ratios increases by averaging the values obtained from both the posive and negative modes. A correlation was found between the ratio of the ionization efficiencies in the positive (+) and negative (̄) ESI modes and the octanol-water partition constant and, more importantly, the compound's O/C. To demonstrate the utility of this correlation for estimating average O/C values of unknown mixtures, we analyzed the ESI (+) and ESI (̄) data for SOAs produced by oxidation of limonene and isoprene and compared them online to O/C measurements using an aerosol mass spectrometer (AMS). This work demonstrates that the accuracy of the HR ESI-MS method is comparable to that of the AMS with the added benefit of molecular identification of the aerosol constituents. © 2012 American Chemical Society.

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