个人简介

Igor I. Slowing received his License degree in Chemistry at San Carlos University, Guatemala in 1995, and worked as a Professor of Chemistry in Guatemala until 2003. He obtained his Ph.D. at Iowa State University under Victor S.-Y. Lin in 2008, working in the development of smart nanoparticles for stimuli-responsive intracellular drug delivery. He joined the Ames Laboratory as a staff scientist in 2009 to develop multifunctionalized nanostructured materials for catalysis, and joined the Department of Chemistry in 2013 as an Adjunct Assistant Professor.

研究领域

Multitasking Nanostructured Materials

Multitasking nanostructured materials. The Slowing group seeks to understand and control chemical processes in confined domains. To this end our team develops porous nanostructured materials capable of constraining solvated species to dimensions within the range of five to ten times their molecular size. This allows us exploring the effects of partially restricted motion on molecular stability, supramolecular interactions and chemical reactivity. We investigate how local environment at the nanoscale affects the behavior of reactive species and influences the mechanism, kinetics and selectivity of reactions. We apply this understanding to develop nanodevices that are useful in various fields such as catalysis, sensing, biomedical research or environmental chemistry. Our research program is focused on three major areas that start with (1) the development of tools and materials to be used for (2) learning and understanding basic phenomena, which can then be applied to (3) create efficient platforms and devices to solve relevant problems in various fields. More specifically, our main areas of research are: (1) Synthesis and controlled multifunctionalization of mesoscale nanostructured materials. We are particularly interested in meso- and nanoporous structures. We synthesize materials using supramolecular interactions to guide the self-assembly of reactive precursors into well-defined structures with high control of particle and pore geometries. We are especially interested in controlling the assembly of different types of precursors at all size regimes: from individual molecules to nanometer sized structures, to mesoscale assemblies, to macroscopic objects. Bridging the gap between each length scale opens interesting research questions about new physical and chemical behaviors that may emerge from the interactions between the components that are assembled. We keep developing new materials with compositions as diverse as silicas, metal oxides, rare earths, carbons and polymers. Significant efforts are devoted to develop methods for controlling the location of multiple functional groups as they are chemically bound to the surface of nanostructured particles. Strong collaborations with analytical chemists and theoretical scientists allow understanding methods and properties of these materials and their assemblies. (2) Understanding and controlling chemical processes in confined domains. We are interested in learning how local environment and restricted mobility condition the behavior of small molecules. The fundamental questions our research tries to answer include whether confinement at the nanometer scale affects chemical reactivity and reaction selectivity, and if it can induce or inhibit sophisticated processes such as cooperativity or molecular organization. We have observed that simple conversions such as C-C coupling via carbonyl condensation or aza-Michael additions show a strong dependence on pore width when the catalysts are tethered to the pore surface. We have also observed a similar behavior as a function of pore length. These results suggest that confinement effects are significant even when the space within nanoreactor is up to ten times larger than the reactants. Solvents are well known to affect the stability of transition states and disrupt or favor intermolecular interactions to regulate chemical reactivity in homogeneous processes. While such effects are also valid for heterogeneous reactions, little is known if they behave the same in nanoconfined systems, where molecular crowding may also play an important role. We have observed that tethering organic groups to the nanopore surface and around confined catalytic nanoparticles leads to significant changes in the selectivity of hydrotreatment of fatty acids. The changes in product selectivity seem to be affected by acidity and steric constraints rather than by polarity of the surrounding groups. These observations suggest there is a significant amount of work needed to elucidate the effects of organic groups in the immediacy of active sites in heterogeneous catalysts. We perform structure-activity relationship studies within nanoporous materials to better understand the mechanistic aspects of environmental effects on catalytic sites. As in the previous area, this research enjoys the valuable contribution of our experimental and theoretical collaborators. (3) Developing multitasking nanodevices to solve chemical, biological and environmental problems. The synthetic capabilities and fundamental understanding obtained in the above research areas allow us to design and develop complex nanodevices capable of performing multiple tasks. These nanostructured materials can be co-assembled with components as diverse as biomolecules (enzymes, DNA, etc.), organocatalysts, and plasmonic nanoparticles to produce a wide range of functionalities. Ultimately, these hybrid nanodevices can be used to address practical problems in several different areas. Of particular advantage is the synthetic capacity of introducing multiple functional groups into single nanoparticles. Developing methods to control relative locations of multiple functionalities is key to synthesize advanced materials capable of displaying sophisticated behaviors like cooperativity between neighboring groups or co-localization of mutually incompatible species within the same material. Some of the multifunctionalized nanostructured materials we have assembled include multicatalytic systems that lead reactants through tandem processes behaving like nanosized assembly lines, or nanorefining units that selectively isolate and convert target substances from complex feedstocks like crude microalgal oil into renewable fuels. Tuning the properties of these materials allow also replacing expensive precious metal catalysts with inexpensive earth abundant elements, with the aim of improving the economy of important catalytic reactions: we have recently shown how hydrotreatment of crude microalgal oil can be efficiently performed with Ni or Fe catalysts as alternatives to Pd, Pt or sulfided metals. All these capabilities lead us to envision our nanostructured materials as general platforms for studying novel phenomena, obtaining fundamental understanding of chemical processes at the nano- to molecular scale, and extending unique behaviors characteristic of nanoscale confined systems to the macroscale. These research directions are significantly enhanced by strong collaborations with many theoretical and experimental research groups, and the practical application of some of our systems is facilitated by collaborations with various industrial partners.

近期论文

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Nelson, N.C.; Manzano, J.S.; Sadow, A.D.; Overbury, S.H.; Slowing, I.I. "Selective Hydrogenation of Phenol Catalyzed by Palladium on High-Surface-Area Ceria at Room Temperature and Ambient Pressure" ACS Catal., 5, 2051-2061, 2015. Opembe, N.N.; Guild, C.; King’ondu, C.; Nelson, N.N.; Slowing, I.I.; Suib, S.L. "Vapor-Phase Oxidation of Benzyl Alcohol Using Manganese Oxide Octahedral Molecular Sieves (OMS-2)" Ind. Eng. Chem. Res., 53, 19044–19051, 2014. Wang, C.-J.; Ackerman, D.M. Slowing, I.I., Evans, J.W. "Langevin and Fokker-Planck Analyses of Inhibited Molecular Passing Processes Controlling Transport and Reactivity in Nanoporous Materials" Phys. Rev. Lett., 113, 038301, 2014. Nelson, N.C.; Chaudhary, U.; Kandel, K.; Slowing, I.I. "Heterogeneous Multicatalytic System for Single-Pot Oxidation and C-C Coupling Reaction Sequences" Top. Catal., 57, 1000-1006, 2014. Kandel, K.; Anderegg, J.W.; Nelson, N.C.; Chaudhary, U.; Slowing, I.I. "Supported iron nanoparticles for the hydrodeoxygenation of microalgal oil to green diesel" J Catal., 314, 142-148, 2014. Kandel, K.; Frederickson, C.; Smith, E.A.; Lee, Y.J.; Slowing, I.I. "Bifunctional Sorbent-Catalytic Nanoparticles for the Refining of Renewable Feedstocks" ACS Catal., 3, 2750-2758, 2013. Fang, X.; Hansen, L.; Haso, F.; Yin, P.; Pandey, A.; Engelhardt, L.; Slowing, I.; Li, T.; Liu, T.; Luban, M.; Johnston. "{Mo24Fe12} Macrocycles: Anion Templation with Large Polyoxometalate Guests." Angew. Chem. Int. Ed., 52, 10500-10504, 2013. Kandel, K.; Althaus, S.M.; Pruski, M.; Slowing, I.I. "Supported Hybrid Enzyme-Organocatalysts for Upgrading the Carbon Content of Alcohols." in Novel Materials for Catalysis and Fuels Processing. ACS Symposium Series., 1132, 261-271, 2013. Kandel, K.; Althaus, S.M.; Peeraphatdit, C.; Kobayashi, T.; Trewyn, B.G.; Pruski, M.; Slowing, I.I. "Solvent-Induced Reversal of Activities between Two Closely Related Heterogeneous Catalysts in the Aldol Reaction." ACS Catal., 3, 265-271, 2013. Kobayashi, T.; Lafon, O.; Thankamony, A.S.L.; Slowing, I.I.; Kandel, K.; Carnavale, D.; Vitzthum, V.; Vezin, H.; Amoureux, J.-P.; Bodenhausen, G.; Pruski, M. "Analysis of sensitivity enhancement by dynamic nuclear polarization in solid state NMR: a case study of functionalized mesoporous materials." Phys. Chem. Chem. Phys., 15, 5553-5562, 2013. Lafon, O.; Thankamony, A.S.L.; Kobayashi, T.; Carnavale, D.; Vitzthum, V.; Slowing, I.I.; Kandel, K.; Vezin, H.; Amoureux, J.-P.; Bodenhausen, G.; Pruski, M. "Mesoporous Silica Nanoparticles Loaded with Surfactant: Low Temperature Magic Angle Spinning 13C and 29Si NMR Enhanced by Dynamic Nuclear Polarization." J. Phys. Chem. C, 117, 1375–1382, 2013. Kandel, K.; Althaus, S.M.; Peeraphatdit, C.; Kobayashi, T.; Trewyn, B.G.; Pruski, M.; Slowing, I.I. "Substrate Inhibition in the Heterogeneous Catalyzed Aldol Condensation: A Mechanistic Study of Supported Organocatalysts." J. Catal., 291, 63-68, 2012. Ruberu, T.P.A.; Nelson, N.C.; Slowing, I.I., Vela, J. "Selective Alcohol Dehydrogenationand Hydrogenolysis with Semicondutor-Metal Photocatalysts: Towards Solar-to-Chemical Energy Conversion of Biomass Relevant Substrates." J. Phys. Chem. Lett., 3, 2798-2802, 2012. Fang, I-J.; Slowing, I.I.; Wu, C.-W.; Lin, V.S.-Y.; Trewyn, B.G. "Ligand Conformation Dictates Membrane and EndosomalTrafficking of Arginine-Glycine-Aspartate (RGD)-Functionalized Mesoporous Silica Nanoparticles." Chem. Eur. J., 18, 7787-7792, 2012. Valenstein, J.S.; Kandel, K.; Melcher, F.; Slowing, I.I.; Lin, V.S.-Y.; Trewyn, B.G. "Functional Mesoporous Silica Nanoparticles for the Selective Sequestration of Free Fatty Acids from Microalgal Oil." ACS Appl. Mater. Interf., 4, 1003-1009, 2012. Knezevic, N.Z.; Slowing, I.I.; Lin, V.S.-Y. "Tuning the Release of Anticancer Drugs from Magnetic Iron Oxide/Mesoporous Silica Core/Shell Nanoparticles." ChemPlusChem, 77, 48-55, 2012. Wang, J.; Ackerman, D.M.; Kandel, K.; Slowing, I.I.; Pruski, M.; Evans, J.W. "Conversion Reactions in Surface-Functionalized Mesoporous Materials: Effect of Restricted Transport and Catalytic Site Distribution." Mater. Res. Soc. Symp. Proceed.s. 1423, mrsf11-1423-rr06-06, 2012. Sun, X.; Zhao, Y.; Lin, V.S.-Y.; Slowing, I.I.; Trewyn, B.G. "Luciferase and luciferin co-immobilized Mesoporous Silica Nanoparticle materials for Intracellular Biocatalysis." J. Am. Chem. Soc., 133, 18554-18557, 2011. Nedd, S.; Kobayashi, T.; Tsai, C-H.; Slowing, I.I.; Pruski, M.; Gordon, M.S."Using a reactive force field to correlate mobilities obtained from solid state 13C NMR on mesoporous silica nanoparticle systems." J. Phys. Chem. C, 115, 16333-16339, 2011. Tsai, C.; Vivero-Escoto, J.L.; Slowing, I.I.; Fang, I-J.; Trewyn, B.G.; Lin, V.S.-Y. "Surfactant-assisted controlled release of hydrophobic drugs using anionic surfactant templated mesoporous silica nanoparticles." Biomater., 32, 6234-6244, 2011.