Braun Group People
Dara Van Gough
Graduate Student in the Materials Science and Engineering
B.S. in Materials Science and Engineering from North Carolina State University (2005)
My research focuses on mesostructured core-shell particles for applications in catalysis, drug delivery, encapsulation, and low dielectric constant materials for microelectronics. The synthesis of these particles takes advantage of a room temperature process involving a lyotropic liquid crystal template to controllably mineralize a ZnS shell on a removable silica core. The advantage to this synthetic approach is the formation of a mesostructured hollow material at room temperature, which enables us to study the interaction of organic species with the particles.
Additional research interests include surface chemistry, drug delivery, and nanostructured materials.
Mesostructured materials have attracted much attention due to their high surface to volume ratio. These structures are achieved by various methods, which include removable templates. Employing this synthetic route, it is possible to attain a uniform pore structure with a variety of materials. Another class of materials that has attracted a great deal of interest is hollow structured materials (or hollow spheres). Achieving these hollow particles has been accomplished primarily via sacrificial core templating- core materials include air-water interfaces, oil-water interfaces, and colloids. Mesostructured and hollow particles have been independently constructed of silica, titania, metal oxides, metal sulfides, etc.
My research takes advantage of the properties of both of these structures, yielding mesoporous hollow spheres for applications that include encapsulation, drug delivery, low dielectric constant materials for microelectronics, and catalysis. Synthesizing the mesoporous hollow spheres (MHS) entails mineralizing zinc sulfide on a sacrificial polymer or silica core within a lyotropic liquid crystalline template (Figure 1).
Figure 1: General scheme for the synthesis of mesoporous hollow spheres (MHS). First, the sacrificial core and precursors (zinc acetate and thioacetamide) are dispersed in the lyotropic liquid crystal. Next, ZnS is mineralized onto the surface of the sacrificial core. Finally, the core is removed. (Figure adopted from reference 1.)
In order to achieve the desired applications, it is necessary to encapsulate a desired species within the MHS. Presently, this is accomplished by methods previously described by many authors, including Mulvaney et al. [2] and Kamata et al. [3], in which the species of interest were encapsulated within a silica matrix. Encapsulating gold nanoparticles within ZnS MHS was previously demonstrated, Figure 2 [1].
Figure 2: TEM images of MHS: (a) after etching of the polystyrene colloidal template, (b) higher magnification image and FFT of the region marked in the white square of (a), (c) after etching of the Au nanoparticle (visible in the lower right of white square) contained in the silica colloidal template, and (d) higher magnification of the white square in (c). (Figure and caption from reference 1.)
Currently, I am interested in expanding our control of the shell material and in varying the materials that can be entrapped within the MHS. Increasing control of the shell material will enable us to vary the size of both the species entrapped and the size of the species diffusing into the MHS. It is also necessary to broaden the range of materials contained within the shell in order to achieve the potential of MHS in the previously stated applications.
References:
[1] Wolosiuk et al. JACS (2005) 127, 16536-7.
[2] Mulvaney et al. J. Mater. Chem. (2000) 10, 1259-70.
[3] Kamata et al. JACS (2003) 125, 2384-5
Professor Paul Braun • Phone: +1.217.244.7293 • Fax: +1.217.333.2736 • Email: pbraun@illinois.edu
Department of Materials Science and Engineering • University of Illinois at Urbana-Champaign