Search

Your search keyword '"Grass, Michael E."' showing total 179 results
Start Over Author "Grass, Michael E."
179 results on '"Grass, Michael E."'

1. Observation of insulating–insulating monoclinic structural transition in macro‐sized VO2 single crystals [Phys. Status Solidi RRL 5, No. 3, R107–R109 (2011)]

Author

Mun, Bongjin Simon, Chen, Kai, Leem, Youngchul, Dejoie, Catherine, Tamura, Nobumichi, Kunz, Martin, Liu, Zhi, Grass, Michael E, Park, Changwoo, Yoon, Joonseok, Lee, Y Yvette, and Ju, Honglyoul

Subjects
Condensed Matter Physics, Materials Engineering, Nanotechnology, Applied Physics
Abstract

In our article, we reported the observation of monoclinic M2 to M1 structural phase transition in VO2 single crystal near the temperature of ∼49 °C. However, the re-examination of Laue patterns reveals that previously defined monoclinic M1 and M2 phases can be interpreted as monoclinic M2 and triclinic T phases instead. Careful experimental geometry calibration and further refinement of the lattice parameter ratios and angles show that monoclinic M2 and triclinic T phases fit better with the experimental data. On the other hand, our previous misidentification of the insulating phases does NOT affect the conclusions of our article.

Published
2015

2. Observation of new intrinsic properties of VO2

Author

Mun, Bongjin Simon, Chen, Kai, Leem, Youngchul, Dejoie, Catherine, Tamura, Nobumichi, Kunz, Martin, Liu, Zhi, Grass, Michael E., Park, Changwoo, Lee, Y. Yvette, and Ju, Honglyoul

Subjects
Condensed Matter - Materials Science
Abstract

The single crystal VO2, exihibiting a first-order metal-insulator transition (MIT) at 67.2 degrees C and an insulator-insulator transition (IIT) at ~49.7 degrees C, is grown. From synchrotron-based x-ray microdiffraction analysis, the IIT shows structural phase transition (SPT) of monoclinic M2 to M1 phases while the MIT displays M1 to rutile R phases. The IIT exhibits percolative SPT while the MIT shows abrupt transition width of < 0.02 degrees C, supporting Mott's prediction. The MIT occurs non-percolatively with a sharp boundary between R and M1 phases. The MIT onset temperature shows significant variation., Comment: This paper has been withdrawn by the authors. We would like to withdraw the paper since we arrived at different conclusion based on the re-interpretation of data. Thank you

Published
2010

12. Characterization of colloidal platinum nanoparticles by MALDI-TOF mass spectrometry

Author

Navin, Jason K., Grass, Michael E., Somorjai, Gabor A., and Marsh, Anderson L.

Subjects
Time-of-flight mass spectrometry -- Methods, Platinum -- Identification and classification, Platinum -- Measurement, Nanoparticles -- Identification and classification, Nanoparticles -- Measurement, Chemistry
Abstract

In this work, matrix assisted laser desorption ionization-time-of-flight (MALDI-TOF) mass spectrometry (MS) has been utilized to characterize colloidal platinum nanoparticles synthesized in the 1-4 nm size range. The nanoparticles were prepared via a solution-based method in which the size could be controlled by varying reaction conditions, such as the alcohol used as the reductant. Poly(vinylpyrrolidone), or PVP, (MW = 29 000 g/mol) was employed as a capping agent to stabilize the synthesized nanoparticles in solution. A model for determining the size of the metallic nanoparticle core from MALDI-TOF mass spectra has been developed and verified through correlation with particle sizes from transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurements. In this model it was assumed that 1.85 nm nanoparticles are capped by one PVP chain, which was verified through experiments performed with capped and uncapped nanoparticles. Larger nanoparticles are capped by either two (2.60 and 2.94 nm) or three (3.69 nm) PVP chains. These findings clearly indicate the usefulness of MALDI-TOF MS as a technique for fully characterizing nanoscale materials in order to elucidate structure-property relationships.

Published
2009

13. Acetic Acid as Processing Aid Dramatically Improves Organic Solvent Solubility of Weakly Basic Drugs for Spray Dried Dispersion Manufacture.

Author

Adam, Molly S., Miller, Warren K., Pluntze, Amanda M., Stewart, Aaron M., Cape, Jonathan L., Grass, Michael E., and Morgen, Michael M.

Subjects
SPRAY drying, ACETIC acid, SOLUBILITY, DISPERSION (Chemistry), ORGANIC solvents, SOLVENTS
Abstract

Many active pharmaceutical ingredients (APIs) in the pharmaceutical pipeline require bioavailability enhancing formulations due to very low aqueous solubility. Although spray dried dispersions (SDDs) have demonstrated broad utility in enhancing the bioavailability of such APIs by trapping them in a high-energy amorphous form, many new chemical entities (NCEs) are poorly soluble not just in water, but in preferred organic spray drying solvents, e.g., methanol (MeOH) and acetone. Spraying poorly solvent soluble APIs from dilute solutions leads to low process throughput and small particles that challenge downstream processing. For APIs with basic pKa values, spray solvent solubility can be dramatically increased by using an acid to ionize the API. Specifically, we show that acetic acid can increase API solubility in MeOH:H2O by 10-fold for a weakly basic drug, gefitinib (GEF, pKa 7.2), by ionizing GEF to form the transient acetate salt. The acetic acid is removed during drying, resulting in a SDD of the original GEF free base having performance similar to SDDs sprayed from solvents without acetic acid. The increase in solvent solubility enables large scale manufacturing for these challenging APIs by significantly increasing the throughput and reducing the amount of solvent required. [ABSTRACT FROM AUTHOR]

Published
2022
Full Text
View/download PDF

16. Oxidation and reduction of size-selected subnanometer Pd clusters on Al2O3 surface.

Author

Mao, Bao-Hua, Chang, Rui, Lee, Sungsik, Axnanda, Stephanus, Crumlin, Ethan, Grass, Michael E., Wang, Sui-Dong, Vajda, Stefan, and Liu, Zhi

Subjects
PALLADIUM, OXIDATION, CHEMICAL reduction, ALUMINUM oxide, SURFACE chemistry, METAL cluster size, BINDING energy
Abstract

In this paper, we investigate uniformly dispersed size-selected Pdn clusters (n = 4, 10, and 17) on alumina supports. We study the changes of clustered Pd atoms under oxidizing and reducing (O2 and CO, respectively) conditions in situ using ambient pressure XPS. The behavior of Pd in the clusters is quite different from that of Pd foil under the same conditions. For all Pd clusters, we observe only one Pd peak. The binding energy of this Pd 3d peak is ∼1-1.4 eV higher than that of metallic Pd species and changes slightly in CO and O2 environments. On the Pd foil however many different Pd species co-exist on the surface and change their oxidation states under different conditions. We find that the Pd atoms in direct contact with Al2O3 differ in oxidation state from the surface Pd atoms in a foil under reaction conditions. Compared to previous literature, we find that Pd 3d peak positions are greatly influenced by the different types of Al2O3 supports due to the combination of both initial and final state effects. [ABSTRACT FROM AUTHOR]

Published
2013
Full Text
View/download PDF

18. Evolution of structure and chemistry of bimetallic nanoparticle catalysts under reaction conditions

Author

Feng Tao, Zhongwei Zhu, Zhi Liu, Salmeron, Miquel, Somorjai, Gabor A., Altoe, Virginia, Alayoglu, Selim, Renzas, James R., Chia-Kuang Tsung, Yawen Zhang, Grass, Michael E., Butcher, Derek R., Aksoy, Funda, and Aloni, Shaul

Subjects
Chemical reactions -- Analysis, Rhodium -- Chemical properties, Rhodium -- Structure, Palladium -- Chemical properties, Palladium -- Structure, Chemistry
Abstract

One-step colloidal chemistry is used for preparing three series of bimetallic nanoparticle catalysts ([Rh.sub.x][Pd.sub.1-x], [Rh.sub.x][Pt.sub.1-x] and [Pd.sub.x][Pt.sub.1-x]). The structural evolution of bimetallic nanoparticles under different reaction conditions has highlighted the importance of in situ studies of surface structures of nanoparticle catalysts.

Published
2010

19. Highly selective synthesis of catalytically active monodisperse rhodium nanocubes

Author

Zhang, Yawen, Grass, Michael E., Kuhn, John N., Feng Tao, Habas, Susan E., Wenyu Huang, Peidong Yang, and Somorjai, Gabor A.

Subjects
Ammonium chloride -- Chemical properties, Ammonium compounds -- Chemical properties, Ammonium paratungstate -- Chemical properties, Catalysis -- Analysis, Nanotubes -- Chemical properties, Rhodium -- Chemical properties, Rhodium -- Electric properties, Chemistry
Abstract

The highly selective synthesis of catalytically active, monodisperse Rh nanocubes (NCs) is described by using a seedless polyol method. The {100} faces of the Rh NCs are stabilized by chemically adsorbed [Br.sup.-] ions from trimethyl(tetradecyl)ammonium bromide (TTAB).

Published
2008

22. Highly Enhanced Concentration and Stability of Reactive Ce^3+ on Doped CeO_2 Surface Revealed In Operando

Author

Chueh, William C., McDaniel, Anthony H., Grass, Michael E., Hao, Yong, Jabeen, Naila, Liu, Zhi, Haile, Sossina M., McCarty, Kevin F., Bluhm, Hendrik, and El Gabaly, Farid

Abstract

Trivalent cerium ions in CeO_2 are the key active species in a wide range of catalytic and electro-catalytic reactions. We employed ambient pressure X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy to quantify simultaneously the concentration of the reactive Ce^3+ species on the surface and in the bulk of Sm-doped CeO_2(100) in hundreds of millitorr of H2–H2O gas mixtures. Under relatively oxidizing conditions, when the bulk cerium is almost entirely in the 4+ oxidation state, the surface concentration of the reduced Ce^3+ species can be over 180 times the bulk concentration. Furthermore, in stark contrast to the bulk, the surface’s 3+ oxidation state is also highly stable, with concentration almost independent of temperature and oxygen partial pressure. Our thermodynamic measurements reveal that the difference between the bulk and surface partial molar entropies plays a key role in this stabilization. The high concentration and stability of reactive surface Ce^3+ over wide ranges of temperature and oxygen partial pressure may be responsible for the high activity of doped ceria in many pollution-control and energy-conversion reactions, under conditions at which Ce^3+ is not abundant in the bulk.

Published
2012

23. Observation of insulating-insulating monoclinic structural transition in macro-sized VO2single crystals [Phys. Status Solidi RRL5, No. 3, R107-R109 (2011)]

Author

Mun, Bongjin Simon, primary, Chen, Kai, additional, Leem, Youngchul, additional, Dejoie, Catherine, additional, Tamura, Nobumichi, additional, Kunz, Martin, additional, Liu, Zhi, additional, Grass, Michael E., additional, Park, Changwoo, additional, Yoon, Joonseok, additional, Lee, Y. Yvette, additional, and Ju, Honglyoul, additional

Published
2015
Full Text
View/download PDF

25. Mechanistic Studies of Water Electrolysis and Hydrogen Electro-Oxidation on High Temperature Ceria-Based Solid Oxide Electrochemical Cells

Author

Zhang, Chunjuan, primary, Yu, Yi, additional, Grass, Michael E., additional, Dejoie, Catherine, additional, Ding, Wuchen, additional, Gaskell, Karen, additional, Jabeen, Naila, additional, Hong, Young Pyo, additional, Shavorskiy, Andrey, additional, Bluhm, Hendrik, additional, Li, Wei-Xue, additional, Jackson, Gregory S., additional, Hussain, Zahid, additional, Liu, Zhi, additional, and Eichhorn, Bryan W., additional

Published
2013
Full Text
View/download PDF

31. Reversible formation of a PdCx phase in Pd nanoparticles upon CO and O2 exposure

Author

Balmes, Olivier, primary, Resta, Andrea, additional, Wermeille, Didier, additional, Felici, Roberto, additional, Messing, Maria E., additional, Deppert, Knut, additional, Liu, Zhi, additional, Grass, Michael E., additional, Bluhm, Hendrik, additional, Rijn, Richard van, additional, Frenken, Joost W. M., additional, Westerström, Rasmus, additional, Blomberg, Sara, additional, Gustafson, Johan, additional, Andersen, Jesper N., additional, and Lundgren, Edvin, additional

Published
2012
Full Text
View/download PDF

32. Impact of Drug-Rich Colloids of Itraconazole and HPMCAS on Membrane Flux in Vitroand Oral Bioavailability in Rats

Author

Stewart, Aaron M., Grass, Michael E., Brodeur, Timothy J., Goodwin, Aaron K., Morgen, Michael M., Friesen, Dwayne T., and Vodak, David T.

Abstract

Improving the oral absorption of compounds with low aqueous solubility is a common challenge that often requires an enabling technology. Frequently, oral absorption can be improved by formulating the compound as an amorphous solid dispersion (ASD). Upon dissolution, an ASD can reach a higher concentration of unbound drug than the crystalline form, and often generates a large number of sub-micrometer, rapidly dissolving drug-rich colloids. These drug-rich colloids have the potential to decrease the diffusional resistance across the unstirred water layer of the intestinal tract (UWL) by acting as rapidly diffusing shuttles for unbound drug. In a prior study utilizing a membrane flux assay, we demonstrated that, for itraconazole, increasing the concentration of drug-rich colloids increased membrane flux in vitro. In this study, we evaluate spray-dried amorphous solid dispersions (SDDs) of itraconazole with hydroxypropyl methylcellulose acetate succinate (HPMCAS) to study the impact of varying concentrations of drug-rich colloids on the oral absorption of itraconazole in rats, and to quantify their impact on in vitroflux as a function of bile salt concentration. When Sporanox and itraconazole/AFFINISOL High Productivity HPMCAS SDDs were dosed in rats, the maximum absorption rate for each formulation rank-ordered with membrane flux in vitro. The relative maximum absorption rate in vivocorrelated well with the in vitroflux measured in 2% SIF (26.8 mM bile acid concentration), a representative bile acid concentration for rats. In vitroit was found that as the bile salt concentration increases, the importance of colloids for improving UWL permeability is diminished. We demonstrate that drug-containing micelles and colloids both contribute to aqueous boundary layer diffusion in proportion to their diffusion coefficient and drug loading. These data suggest that, for compounds with very low aqueous solubility and high epithelial permeability, designing amorphous formulations that produce colloids on dissolution may be a viable approach to improve oral bioavailability.

Published
2017
Full Text
View/download PDF

34. Nonpercolative metal-insulator transition in VO2single crystals

Author

Mun, Bongjin Simon, primary, Chen, Kai, additional, Yoon, Joonseok, additional, Dejoie, Catherine, additional, Tamura, Nobumichi, additional, Kunz, Martin, additional, Liu, Zhi, additional, Grass, Michael E., additional, Mo, Sung-Kwan, additional, Park, Changwoo, additional, Lee, Y. Yvette, additional, and Ju, Honglyoul, additional

Published
2011
Full Text
View/download PDF

36. Cover Picture: Observation of insulating-insulating monoclinic structural transition in macro-sized VO2 single crystals (Phys. Status Solidi RRL 3/2011)

Author

Mun, Bongjin Simon, primary, Chen, Kai, additional, Leem, Youngchul, additional, Dejoie, Catherine, additional, Tamura, Nobumichi, additional, Kunz, Martin, additional, Liu, Zhi, additional, Grass, Michael E., additional, Park, Changwoo, additional, Yoon, Joonseok, additional, Lee, Y. Yvette, additional, and Ju, Honglyoul, additional

Published
2011
Full Text
View/download PDF

40. In Situ Characterization of Ceria Oxidation States in High-Temperature Electrochemical Cells with Ambient Pressure XPS

Author

DeCaluwe, Steven C., primary, Grass, Michael E., additional, Zhang, Chunjuan, additional, Gabaly, Farid El, additional, Bluhm, Hendrik, additional, Liu, Zhi, additional, Jackson, Gregory S., additional, McDaniel, Anthony H., additional, McCarty, Kevin F., additional, Farrow, Roger L., additional, Linne, Mark A., additional, Hussain, Zahid, additional, and Eichhorn, Bryan W., additional

Published
2010
Full Text
View/download PDF

41. Measuring fundamental properties in operating solid oxide electrochemical cells by using in situ X-ray photoelectron spectroscopy

Author

Zhang, Chunjuan, primary, Grass, Michael E., additional, McDaniel, Anthony H., additional, DeCaluwe, Steven C., additional, Gabaly, Farid El, additional, Liu, Zhi, additional, McCarty, Kevin F., additional, Farrow, Roger L., additional, Linne, Mark A., additional, Hussain, Zahid, additional, Jackson, Gregory S., additional, Bluhm, Hendrik, additional, and Eichhorn, Bryan W., additional

Published
2010
Full Text
View/download PDF

43. Evolution of Structure and Chemistry of Bimetallic Nanoparticle Catalysts under Reaction Conditions

Author

Tao, Feng, primary, Grass, Michael E., additional, Zhang, Yawen, additional, Butcher, Derek R., additional, Aksoy, Funda, additional, Aloni, Shaul, additional, Altoe, Virginia, additional, Alayoglu, Selim, additional, Renzas, James R., additional, Tsung, Chia-Kuang, additional, Zhu, Zhongwei, additional, Liu, Zhi, additional, Salmeron, Miquel, additional, and Somorjai, Gabor A., additional

Published
2010
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results