title: Chemical compositions of black carbon particle cores and coatings via soot particle aerosol mass spectrometry with photoionization and electron ionization.
abstract: Black carbon is an important constituent of atmospheric aerosol particle matter (PM) with significant effects on the global radiation budget and on human health. The soot particle aerosol mass spectrometer (SP-AMS) has been developed and deployed for real-time ambient measurements of refractory carbon particles. In the SP-AMS, black carbon or metallic particles are vaporized through absorption of 1064 nm light from a CW Nd:YAG laser. This scheme allows for continuous "soft" vaporization of both core and coating materials. The main focus of this work is to characterize the extent to which this vaporization scheme provides enhanced chemical composition information about aerosol particles. This information is difficult to extract from standard SP-AMS mass spectra because they are complicated by extensive fragmentation from the harsh 70 eV EI ionization scheme that is typically used in these instruments. Thus, in this work synchotron-generated vacuum ultraviolet (VUV) light in the 8-14 eV range is used to measure VUV-SP-AMS spectra with minimal fragmentation. VUV-SP-AMS spectra of commercially available carbon black, fullerene black, and laboratory generated flame soots were obtained. Small carbon cluster cations (C(+)-C5(+)) were found to dominate the VUV-SP-AMS spectra of all the samples, indicating that the corresponding neutral clusters are key products of the SP vaporization process. Intercomparisons of carbon cluster ratios observed in VUV-SP-AMS and SP-AMS spectra are used to confirm spectral features that could be used to distinguish between different types of refractory carbon particles. VUV-SP-AMS spectra of oxidized organic species adsorbed on absorbing cores are also examined and found to display less thermally induced decomposition and fragmentation than spectra obtained with thermal vaporization at 200 °C (the minimum temperature needed to quantitatively vaporize ambient oxidized organic aerosol with a continuously heated surface). The particle cores tested in these studies include black carbon, silver, gold, and platinum nanoparticles. These results demonstrate that SP vaporization is capable of providing enhanced organic chemical composition information for a wide range of organic coating materials and IR absorbing particle cores. The potential of using this technique to study organic species of interest in seeded laboratory chamber or flow reactor studies is discussed.
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Manjula R
authors.initials: MR
authors.lastname: Canagaratna
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Paola
authors.initials: P
authors.lastname: Massoli
authors.affiliation: ‡Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Eleanor C
authors.initials: EC
authors.lastname: Browne
authors.affiliation: ‡Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Jonathan P
authors.initials: JP
authors.lastname: Franklin
authors.affiliation: ∥Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
authors.forename: Kevin R
authors.initials: KR
authors.lastname: Wilson
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Timothy B
authors.initials: TB
authors.lastname: Onasch
authors.affiliation: ⊥Environmental Energy and Technologies Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.|#Department of Civil and Environmental Engineering, University of California-Berkeley, Berkeley, California 94720, United States.
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Kirchstetter
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Edward C
authors.initials: EC
authors.lastname: Fortner
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Kolb
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: John T
authors.initials: JT
authors.lastname: Jayne
authors.affiliation: ‡Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
authors.forename: Jesse H
authors.initials: JH
authors.lastname: Kroll
authors.affiliation: †Center for Aerosol and Cloud Chemistry, Aerodyne Research Inc., Billerica, Massachusetts 01821, United States.
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Worsnop
mesh_terms: D000336:Aerosols / Q000032:analysis*; D002244:Carbon / Q000032:analysis; D002412:Cations / Q000032:analysis; D019343:Citric Acid / Q000032:analysis; D005030:Ethylenes / Q000032:analysis; D037741:Fullerenes / Q000032:analysis; D017612:Gold Compounds / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry; D017671:Platinum Compounds / Q000737:chemistry; D018030:Silver Compounds / Q000737:chemistry; D053260:Soot / Q000032:analysis*; D013696:Temperature; D014466:Ultraviolet Rays; D014618:Vacuum; D014835:Volatilization
chemical_list: D000336:Aerosols; D002412:Cations; D005030:Ethylenes; D037741:Fullerenes; D017612:Gold Compounds; D017671:Platinum Compounds; D018030:Silver Compounds; D053260:Soot; D019343:Citric Acid; D002244:Carbon; C036216:ethylene