@article {54,
	title = {Hematite decorated multi-walled carbon nanotubes (α-Fe2O3/MWCNTs) as sorbents for Cu(II) and Cr(VI): comparison of hybrid sorbent performance to its nanomaterial building blocks.},
	journal = {RSC Advances},
	volume = {6},
	year = {2016},
	note = {CAPLUS AN 2016:1655141(Journal; Online Computer File)},
	month = {2016},
	pages = {99997 - 100007},
	publisher = {Royal Society of Chemistry},
	abstract = {Major hurdles in the application of engineered nanomaterials for water treatment include loss of reactive surface area arising from particle aggregation and the development of application platforms that limit their potential release into the treated water supply.  Here, we develop hybrid nanostructures through the growth of hematite (α-Fe2O3) nanoparticles, which are recognized sorbents for various heavy metals, on multi-walled carbon nanotubes (MWCNTs).  The hybrid nanostructures were synthesized via hydrolysis of ferric nitrate in the presence of carboxylated MWCNTs, and their activity as sorbents toward Cu(II) and chromate (CrO42-) was examd. as a function of pH (i.e., pH-edge expts.) and initial metal concn. (i.e., adsorption isotherms).  Characterization of α-Fe2O3/MWCNT nanostructures via Raman spectroscopy and transmission electron microscopy (TEM) with selected area electron diffraction (SAED) confirmed the deposited iron phase as α-Fe2O3.  Further, complementary acid digestions and TEM imaging revealed that the amt. (0.1 and 0.5 g g-1 α-Fe2O3/MWCNT) and size [5.9 ({\textpm}1.1) and 8.9 ({\textpm}1.5) nm, resp.] of α-Fe2O3 nanoparticles immobilized on MWCNTs were tunable during synthesis.  Generally, mass-normalized concns. of adsorbed Cu(II) and CrO42- were greatest for α-Fe2O3/MWCNT hybrids relative to adsorption on either carboxylated MWCNTs or freely suspended α-Fe2O3 nanoparticles, with evidence implicating α-Fe2O3 as the active sorbent phase in hybrid materials.  Indeed, per unit mass of available α-Fe2O3, hybrid sorbents exhibited capacities comparable to or exceeding most other iron-based sorbents for Cu(II) and CrO42- (from 220 to 470 mg Cu(II) per g α-Fe2O3 and 60 mg CrO42- per g α-Fe2O3, resp., at pH 6 and 20 {\textdegree}C).  The enhanced sorption capacity of the hybrid nanostructures is due, at least in part, to the greater available surface area of α-Fe2O3 nanoparticles immobilized on MWCNTs when compared to their more extensively aggregated state in suspension.  Notable differences in the pH-dependent trends of Cu(II) and CrO42- uptake on α-Fe2O3/MWCNT hybrids, along with differences in zeta potential measurements across pH, also suggest that the immobilized α-Fe2O3 nanoparticles may exhibit unique surface reactivity relative to their freely suspended analogs as a result of their assocn. with the neg. charged MWCNT surface. [on SciFinder(R)]},
	keywords = {hematite MWCNT copper chromium hybrid sorbent nanomaterial building block},
	isbn = {2046-2069},
	author = {Verdugo, Edgard M. and Xie, Yang and Baltrusaitis, Jonas and Cwiertny, David M.}
}
@article {56,
	title = {Reversible Photohydration of Trenbolone Acetate Metabolites: Mechanistic Understanding of Product-to-Parent Reversion through Complementary Experimental and Theoretical Approaches.},
	journal = {Environmental Science \& Technology},
	volume = {50},
	year = {2016},
	note = {CAPLUS AN 2016:126331(Journal; Online Computer File)},
	month = {2016},
	pages = {6753 - 6761},
	publisher = {American Chemical Society},
	abstract = {Photolysis expts. (in H2O and D2O) and quantum chem. calcns. were performed to explore the pH-dependent, reversible photohydration of trenbolone acetate (TBA) metabolites.  Photohydration of 17α-trenbolone (17α-TBOH) and 17β-trenbolone (17β-TBOH) occurred readily in simulated sunlight to yield hydrated products with incorporated H+ at C4 and OH- at either C5 (5-OH-TBOH) or C12 (12-OH-TBOH) in the tetracyclic steroid backbone.  Although unable to be elucidated anal., theory suggests preferred orientations of cis-12-OH-TBOH (relative to C13 methyl) and trans-5-OH-TBOH, with the former most thermodynamically stable overall.  Both expt. and theory indicate limited stability of trans-5-OH-TBOH at acidic pH where it undergoes concurrent, carbocation-mediated thermal rearrangement to cis-12-OH-TBOH and dehydration to regenerate its parent structure.  Expts. revealed cis-12-OH-TBOH to be more stable at acidic pH, which is the only condition where its reversion to parent TBA metabolite occurred.  At basic pH cis-12-OH-TBOH decayed quickly via hydroxide/water addn., behavior that theory attributes to the formation of a stable enolate resistant to dehydration but prone to thermal hydration.  In a noteworthy deviation from predicted theor. stability, 17α-TBOH photohydration yields major trans-5-OH-TBOH and minor cis-12-OH-TBOH, a distribution also opposite that obsd. for 17β-TBOH.  Because H+ and OH- loss from adjacent carbon centers allows trans-5-OH-TBOH to dehydrate at all pH values, the presumed kinetically controlled yield of 17α-TBOH photohydrates results in a greater propensity for 17α-TBOH reversion than 17β-TBOH.  Addnl. calcns. explored minor, but potentially bioactive, trenbolone analogs that could be generated via alternative rearrangement of the acidic carbocation intermediate. [on SciFinder(R)]},
	keywords = {trenbolone acetate metabolite reversible photohydration mechanism},
	isbn = {0013-936X},
	author = {Baltrusaitis, Jonas and Patterson, Eric V. and O{\textquoteright}Connor, Meghan and Qu, Shen and Kolodziej, Edward P. and Cwiertny, David M.}
}
@article {88,
	title = {N-Functionalized Carbon Nanotubes As a Source and Precursor of N-Nitrosodimethylamine: Implications for Environmental Fate, Transport, and Toxicity.},
	journal = {Environmental Science \& Technology},
	volume = {48},
	year = {2014},
	note = {CAPLUS AN 2014:1233176(Journal; Online Computer File)},
	pages = {9279 - 9287},
	publisher = {American Chemical Society},
	abstract = {Hazardous byproducts may be generated during the environmental processing of engineered nanomaterials.  Here, we explore the ability of carbon nanotubes with nitrogen-contg. surface groups (N-CNTs) to generate N-nitrosodimethylamine (NDMA) during chem. disinfection.  Unexpectedly, we obsd. that com. N-CNTs with amine, amide, or N-contg. polymer (PABS) surface groups are a source of NDMA.  As-received powders can leach up to 50 ng of NDMA per mg of N-CNT in aq. suspension; presumably NDMA originates as a residue from N-CNT manufg.  Furthermore, reaction of N-CNTs with free chlorine, monochloramine, and ozone generated byproduct NDMA at yields comparable to those reported for natural org. matter.  Chlorination also altered N-CNT surface chem., with XPS indicating addn. of Cl, loss of N, and an increase in surface O.  Although these changes can increase N-CNT suspension stability, they do not enhance their acute toxicity in E. coli bioassays above that obsd. for as-received powders.  Notably, however, dechlorination of reacted N-CNTs with sulfite completely suppresses N-CNT toxicity.  Collectively, our work demonstrates that N-CNTs are both a source and precursor of NDMA, a probable human carcinogen, while chem. disinfection can produce CNTs exhibiting surface chem. and environmental behavior distinct from that of native (i.e., as-received) materials. [on SciFinder(R)]},
	keywords = {nitrogen functionalized carbon nanotube arsenic source precursor nitrosodimethylamine toxicity},
	isbn = {0013-936X},
	author = {Verdugo, Edgard M. and Krause, Caitlin and Genskow, Kelly and Han, Ying and Baltrusaitis, Jonas and Mattes, Timothy E. and Valentine, Richard L. and Cwiertny, David M.}
}
@article {106,
	title = {Horizontal Attenuated Total Reflectance Fourier Transform Infrared and X-ray Photoelectron Spectroscopy Measurements of Water Adsorption on Oxidized Tin(II) Sulfide (SnS) Surfaces.},
	journal = {Journal of Physical Chemistry C},
	volume = {117},
	year = {2013},
	note = {CAPLUS AN 2012:1849049(Journal; Online Computer File)},
	pages = {472 - 482},
	publisher = {American Chemical Society},
	abstract = {Tin(II) sulfide (SnS) is considered to be a promising optoelectronic material due to its narrow band gap, strong optical absorption, low cost and nontoxic and chem. inert characteristics.  As an inherently stable compd., SnS surfaces are expected to be hydrophobic by nature.  However, exposure of pristine SnS surfaces to air inevitably leads to surface oxidn. which can affect the mineral{\textquoteright}s dissoln., reactivity, optical and electronic properties as well as hydrophobicity.  In the present study, water adsorption measurements on oxidized SnS thin films were performed using horizontal attenuated total reflection Fourier transform IR (HATR-FTIR) spectroscopy.  XPS anal. allowed for characterization of the SnS surface compn. before water vapor exposure and identification of any changes that occurred to the surface after water vapor exposure.  XPS results are consistent with water adsorption occurring on SnS surfaces contg. hydroxyl and carbonate groups.  Addnl., XPS anal. showed that exposure of SnS to water vapor resulted in no significant changes to the original surface compn.  Quant. water adsorption measurements using HATR-FTIR spectroscopy show that the oxidized SnS surface exhibits a slightly hydrophilic nature, demonstrating multilayer water adsorption at high relative humidity (RH) values.  Exptl. water adsorption data were fit using the Brunauer-Emmett-Teller (BET) and Freundlich adsorption models.  From these model fits, details of monolayer water adsorption and the water adsorption mechanisms were extd. to provide a better understanding of gas/surface adsorption on oxidized SnS surfaces.  Results suggest that water adsorption on SnS powder occurs in three distinct regimes, including sub-monolayer water adsorption up to monolayer coverage at 13\% RH, followed by filling of mesopores (13-76\% RH) and finally multilayer water adsorption ( > 76\% RH) via filling of macropores.  This study represents the first report of in situ water adsorption measurements on SnS as a function of relative humidity, illustrating how oxidized surface species can alter the hydrophobic nature of SnS surfaces. [on SciFinder(R)]},
	keywords = {horizontal attenuated total reflectance FTIR XPS, water adsorption oxidized tin sulfide surface},
	isbn = {1932-7447},
	author = {Hatch, Courtney D. and Christie, Matthew J. and Weingold, Robert M. and Wu, Chia-Ming and Cwiertny, David M. and Baltrusaitis, Jonas.}
}
@article {107,
	title = {Identification and Environmental Implications of Photo-Transformation Products of Trenbolone Acetate Metabolites.},
	journal = {Environmental Science \& Technology},
	volume = {47},
	year = {2013},
	note = {CAPLUS AN 2013:623700(Journal; Online Computer File)},
	pages = {5031 - 5041},
	publisher = {American Chemical Society},
	abstract = {Despite the widespread use of the anabolic androgen trenbolone acetate (TBA) in animal agriculture, evidence demonstrating the occurrence of TBA metabolites such as 17β-trenbolone (17β-TBOH), 17α-trenbolone (17α-TBOH), and trendione (TBO) is relatively scarce, potentially due to rapid transformation processes such as direct photolysis.  Therefore, we investigated the phototransformation of TBA metabolites and assocd. ecol. implications by characterizing the photoproducts arising from the direct photolysis of 17β-TBOH, 17α-TBOH, and TBO and their assocd. ecotoxicity.  LC-HRMS/MS anal. identified a range of hydroxylated products that were no longer photoactive, with primary photoproducts consisting of monohydroxy species and presumptive diastereomers.  Also obsd. were higher-order hydroxylated products probably formed via subsequent reaction of primary photoproducts.  NMR anal. confirmed the formation of 12,17-dihydroxy-estra-5(10),9(11),dien-3-one (12-hydroxy-TBOH; 2.2 mg), 10,12,17-trihydroxy-estra-4,9(11),dien-3-one (10,12-dihydroxy-TBOH; 0.7 mg), and a ring-opened 11,12-dialdehyde oxidn. product (TBOH-11,12-dialdehyde; 1.0 mg) after irradn. of \~{}14 mg of 17β-trenbolone.  Though unconfirmed by NMR, our data suggest that the formation of addnl. isomeric products may occur, likely due to the reactivity of the unique 4,9,11 conjugated triene structure of trenbolone.  In vivo exposure studies employing Japanese medaka (Oryzias latipes) indicate that low concns. of 17α-TBOH photoproduct mixts. can alter ovarian follicular development, and photoproducts alter whole-body 17β-estradiol levels.  Therefore, direct photolysis yields photoproducts with strong structural similarity to parent steroids, and these photoproducts still retain enough biol. activity to elicit observable changes to endocrine function at trace concns.  These data indicate that environmental transformation processes do not necessarily reduce steroid hormone ecotoxicity. [on SciFinder(R)]},
	keywords = {photodegrdn trenbolone acetate metabolite Oryzias ecotoxicity},
	isbn = {0013-936X},
	author = {Kolodziej, Edward P. and Qu, Shen and Forsgren, Kristy L. and Long, Sarah A. and Gloer, James B. and Jones, Gerrad D. and Schlenk, Daniel and Baltrusaitis, Jonas and Cwiertny, David M.}
}
@article {113,
	title = {Product-to-parent reversion of trenbolone: Unrecognized risks for endocrine disruption.},
	journal = {Science (Washington, DC, United States)},
	volume = {342},
	year = {2013},
	note = {CAPLUS AN 2013:1616444(Journal)},
	pages = {347 - 351},
	publisher = {American Association for the Advancement of Science},
	abstract = {Trenbolone acetate (TBA) is a high-value steroidal growth promoter often administered to beef cattle, whose metabolites are potent endocrine-disrupting compds.  We performed lab. and field phototransformation expts. to assess the fate of TBA metabolites and their photoproducts.  Unexpectedly, we obsd. that the rapid photohydration of TBA metabolites is reversible under conditions representative of those in surface waters (pH 7, 25{\textdegree}C).  This product-to-parent reversion mechanism results in diurnal cycling and substantial regeneration of TBA metabolites at rates that are strongly temp.- and pH-dependent.  Photoproducts can also react to produce structural analogs of TBA metabolites.  These reactions also occur in structurally similar steroids, including human pharmaceuticals, which suggests that predictive fate models and regulatory risk assessment paradigms must account for transformation products of high-risk environmental contaminants such as endocrine-disrupting steroids. [on SciFinder(R)]},
	keywords = {trenbolone metabolite reversion endocrine disruption environment risk},
	isbn = {0036-8075},
	author = {Qu, Shen and Kolodziej, Edward P. and Long, Sarah A. and Gloer, James B. and Patterson, Eric V. and Baltrusaitis, Jonas and Jones, Gerrad D. and Benchetler, Peter V. and Cole, Emily A. and Kimbrough, Kaitlin C. and Tarnoff, Matthew D. and Cwiertny, David M.}
}
@article {131,
	title = {Dissolution of Hematite Nanoparticle Aggregates: Influence of Primary Particle Size, Dissolution Mechanism, and Solution pH.},
	journal = {Langmuir},
	volume = {28},
	year = {2012},
	note = {CAPLUS AN 2012:1538096(Journal; Online Computer File)},
	month = {2012///},
	pages = {15797 - 15808},
	publisher = {American Chemical Society},
	abstract = {The size-dependent dissoln. of nanoscale hematite (8 and 40 nm α-Fe2O3) was examd. across a broad range of pH (pH 1-7) and mechanisms including proton- and ligand- (oxalate-) promoted dissoln. and dark (ascorbic acid) and photochem. (oxalate) reductive dissoln.  Empirical relations between dissoln. rate and pH revealed that suspensions of 8 nm hematite exhibit between 3.3- and 10-fold greater reactivity per unit mass than suspensions of 40 nm particles across all dissoln. modes and pH, including circumneutral.  Complementary suspension characterization (i.e., sedimentation studies and dynamic light scattering) indicated extensive aggregation, with steady-state aggregate sizes increasing with pH but being roughly equiv. for both primary particles.  Thus, while the reactivity difference between 8 and 40 nm suspensions is generally greater than expected from sp. surface areas measured via N2-BET or estd. from primary particle geometry, loss of reactive surface area during aggregation limits the certainty of such comparisons.  Probably the relative reactivity of 8 and 40 nm hematite suspensions is best explained by differences in the fraction of aggregate surface area that is reactive.  This scenario is consistent with TEM images revealing uniform dissoln. of aggregated 8 nm particles, whereas 40 nm particles within aggregates undergo preferential etching at edges and structural defects.  Ultimately, comparably sized hematite aggregates can exhibit vastly different dissoln. activity depending on the nature of the primary nanoparticles from which they are constructed, a result with wide-ranging implications for iron redox cycling. [on SciFinder(R)]},
	keywords = {dissoln hematite nanoparticle aggregate particle size mechanism pH effect},
	isbn = {0743-7463},
	author = {Lanzl, Caylyn A. and Baltrusaitis, Jonas and Cwiertny, David M.}
}
@article {180,
	title = {Characterization and acid-mobilization study of iron-containing mineral dust source materials.},
	journal = {Journal of Geophysical Research, [Atmospheres]},
	volume = {113},
	year = {2008},
	note = {CAPLUS AN 2008:617952(Journal)},
	month = {2008///},
	pages = {D05202/1-D05202/18},
	publisher = {American Geophysical Union},
	abstract = {Processes that solubilize iron in mineral dust aerosol may increase the amt. of iron supplied to ocean surface waters, and thereby stimulate phytoplankton productivity.  In particular, the uptake of acids such as H2SO4 and HNO3 on mineral dust surfaces can produce extremely acidic environments that promote iron dissoln.  Here, four samples that represent source materials for mineral dust (Saudi Beach sand (SB), Inland Saudi sand (IS), Saharan Sand (SS) and China Loess (CL)) and one com. ref. material (Arizona Test Dust (AZTD)) were characterized, and examd. in dissoln. studies in solns. of sulfuric, nitric and hydrochloric acid ranging from pH 1 to 3.  Mossbauer spectroscopy revealed Fe(III) in all samples, whereas SB, CL and AZTD also contained appreciable Fe(II).  Spectra suggest that both Fe(II) and Fe(III) were substituted into aluminosilicates, although CL, AZTD and IS also contained Fe(III) oxide phases.  Total iron soly. measured after 24 h ranged between 4-16\% of the initial iron content for each material, but did not scale with either the sp. surface area or the total iron content of the samples.  Instead, we show that Fe(II)-contg. solid phases such as Fe(II)-substituted aluminosilicates represent a significant, and sometimes dominant, source of sol. Fe in acidic environments.  Results of dissoln. studies also show that the nature of the acid influences iron solubilization, as elevated concns. of nitrate encountered from nitric acid at pH 1 suppressed Fe(II) formation.  We propose a surface-mediated, non-photochem. redox reaction between nitrate and Fe(II), which may contribute to Fe(II)/Fe(III) cycling in the atm. [on SciFinder(R)]},
	keywords = {iron mineral dust source material acid mobilization},
	author = {Cwiertny, David M. and Baltrusaitis, Jonas and Hunter, Gordon J. and Laskin, Alexander and Scherer, Michelle M. and Grassian, Vicki H.}
}
@article {182,
	title = {Adsorption of sulfur dioxide on hematite and goethite particle surfaces.},
	journal = {Physical Chemistry Chemical Physics},
	volume = {9},
	year = {2007},
	note = {CAPLUS AN 2007:1196084(Journal)},
	month = {2007///},
	pages = {5542 - 5554},
	publisher = {Royal Society of Chemistry},
	abstract = {The adsorption of sulfur dioxide (SO2) on iron oxide particle surfaces at 296 K has been investigated using XPS.  A custom-designed XPS ultra-high vacuum chamber was coupled to an environmental reaction chamber so that the effects of adsorbed water and mol. oxygen on the reaction of SO2 with iron oxide surfaces could be followed at atmospherically relevant pressures.  In the absence of H2O and O2, exposure of hematite (α-Fe2O3) and goethite (α-FeOOH) to SO2 resulted predominantly in the formation of adsorbed sulfite (SO32-), although evidence for adsorbed sulfate (SO42-) was also found.  At satn., the coverage of adsorbed sulfur species was the same on both α-Fe2O3 and α-FeOOH as detd. from the S2p:Fe2p ratio.  Equivalent satn. coverages and product ratios of sulfite to sulfate were obsd. on these oxide surfaces in the presence of water vapor at pressures between 6 and 18 Torr, corresponding to 28 to 85\% relative humidity (RH), suggesting that water had no effect on the adsorption of SO2.  In contrast, mol. oxygen substantially influenced the interactions of SO2 with iron oxide surfaces, albeit to a much larger extent on α-Fe2O3 relative to α-FeOOH.  For α-Fe2O3, adsorption of SO2 in the presence of mol. oxygen resulted in the quant. formation of SO42- with no detectable SO32-.  Furthermore, mol. oxygen significantly enhanced the extent of SO2 uptake on α-Fe2O3, as indicated by the greater than two-fold increase in the S2p:Fe2p ratio.  Although SO2 uptake is still enhanced on α-Fe2O3 in the presence of mol. oxygen and water, the enhancement factor decreases with increasing RH.  In the case of α-FeOOH, there is an increase in the amt. of SO42- in the presence of mol. oxygen, however, the predominant surface species remained SO32- and there is no enhancement in SO2 uptake as measured by the S2p:Fe2p ratio.  A mechanism involving mol. oxygen activation on oxygen vacancy sites is proposed as a possible explanation for the non-photochem. oxidn. of sulfur dioxide on iron oxide surfaces.  The concn. of these sites depends on the exact environmental conditions of RH. [on SciFinder(R)]},
	keywords = {adsorption sulfur dioxide hematite goethite particle surface},
	isbn = {1463-9076},
	author = {Baltrusaitis, Jonas and Cwiertny, David M. and Grassian, Vicki H.}
}
