Dr. Albert E. StiegmanProfessor
Ph.D. (1984) Columbia University
Research InterestINORGANIC MATERIALS CHEMISTRY:
SOL-GEL DERIVED GLASSES AND CERAMICS
We are principally interested in exploring the interface between traditional inorganic chemistry and materials science. To this end, techniques for studying the reactivity, structure, and bonding of inorganic complexes, which have their roots in traditional inorganic chemistry, are applied to important classes of inorganic materials. From the understanding gleaned from such studies, new and potentially useful materials can ultimately be engineered. Particular classes of materials that are both technologically important and amenable to study by our approach are glasses derived from the sol-gel process. This process utilizes the condensation reactions of silicon or metal alkoxides to afford a low-temperature, synthetically flexible route to inorganic glasses and ceramics. For the synthesis of a silicate glass, for example, tetramethylorthosilicate is simply treated with water, which causes it to gel.
The gelled materials are then aged and dried, producing a material known as a "xerogel." Xerogels are hard and optically transparent much like conventional silicate glass; however, they are also highly porous, allowing small molecules to permeate them. By exploiting the synthetic flexibility of the sol-gel process, we have succeeded in incorporating a broad range of transition metal centers into the silica matrix.
mSi(OR)4 + n(RO)xM + (xs) 2O —
[Sim MnO(2m+2.5x)] + (4m+nx) ROH
The resultant material has remarkable properties that are a hybrid of the chemical reactivity of the transition metal center and the structural and morphological properties of the silica matrix. For example they undergo a variety of both thermal and photochemical reactions depending on the metal center present. Our studies of these hybrid materials have focused on their controlled synthesis and on their characterization utilizing electronic, vibrational, and magnetic resonance spectroscopic techniques. Ongoing areas of study in our laboratory include:
First-row, high-valent transition metal centers such as Ti(IV), V(V), and Cr(VI) catalyze a variety of thermal and photochemical transformations including the oxidation of aliphatic and aromatic hydrocarbons, phenols, and alcohols. By exploiting the superior optical properties of the xerogel materials we are able to spectroscopically characterize the active catalytic metal site and to detect and monitor key intermediates in catalytic processes.
POLYMER/SILICA NANOSTRUCTURED MATERIALS
Porous metal silica xerogels made with V(V) have also been found to photoinitiate the polymerization of vinyl and acetylenic functional groups. When photopolymerization is carried out on gaseous or liquid-phase monomers infused into the xerogel glass, a nanocomposite structure results where the organic polymer fills the pores of the silica xerogel matrix. By applying the sol-gel as a thin film coating and polymerizing a fluorinated monomer, we have developed a new, tightly bound, low-surface energy coating for glass and other oxide substrates. Research in our lab is currently directed toward developing new composites containing different polymers and toward exploring their chemical and optical properties.
|Park, C. D., M. Mileham, L. J. van de Burgt, E. A. Muller, and A. E. Stiegman. The Effects of Stoichiometry and Sample Density on Combustion Dynamics and Initiation Energy of Al/Fe2O3 Metastable Interstitial Composites. Journal of Physical Chemistry C 2010|
|Lita, A., A. L. Washington Ii, L. van de Burgt, G. F. Strouse, and A. E. Stiegman. Stable Efficient Solid-State White-Light-Emitting Phosphor with a High Scotopic/Photopic Ratio Fabricated from Fused CdSe-Silica Nanocomposites. Adv. Mater. (Weinheim, Ger.) 2010, 22(36), 3987-3991|
|Adrian Lita, Aaron L. Washington II, Lambertus van de Burgt, Geoffrey F. Strouse and A. E. Stiegman. Stable Efficient Solid-State White-Light-Emitting Phosphor with a High Scotopic/Photopic Ratio Fabricated from Fused CdSe-Silica Nanocomposites. Adv. Mater. (Weinheim, Ger.) 2010, 22, 3987-3991|
|Chi-Dong Park, Melissa Mileham, Lambertus J. van de Burgt, Erik A. Muller and A. E. Stiegman. The Effects of Stoichiometry and Sample Density on Combustion Dynamics and Initiation Energy of Al/Fe2O3 Metastable Interstitial Composites. J.Phys. Chem. C 2010, 114, 2814-2820|
|Stiegman, A.E., C.-D. Park, M. Mileham, L.J. van de Burgt, and M.P. Kramer. Dynamics of Al/Fe2O3 MIC Combustion from Short Single-Pulse Photothermal Initiation and Time-Resolved Spectroscopy. Propellants, Explosives, Pyrotechnics 2009, 34, 293-296|