• People
• Publications
• Research
• Collaborators
• Alumni
• Acknowledgements
• Press
• Group
• Classes

Braun Group People

Colloidal Crystal Self-Assembling of

Photoswitchable DNQ conjugated

Silica and Polymer Colloids

Dong-Guk Yu,
Post-Doctoral Researcher (10/05-7/07)

M. S.: Department of Polymer Science and Engineering, SungKyunKwan University (SKKU), Korea (2001)

Dissertation title: “Fabrication of porous biodegradable polyurethane-urea scaffolds by emulsion freeze drying methods”

Ph. D.: Department of Polymer Science and Engineering, SungKyunKwan University (SKKU), Korea (2004)

Dissertation title: “Preparation and Characterization Electronic Inks for Electrophoretic Displays (EPDs)

Post-Doc.: Department of Materials Science and Engineering, Univ. of Illinois at Urbana-Champaign (UIUC), USA (2005 ~ )

 

In recent years the preparation of functionalized surface amphiphlic (hydrophilic-hydrophobic) spheres has attracted much interest due to the potential applications such as photonic crystals and photonic band gap materials.

One common approach is to alter their electrostatic interactions by varying either the pH or ionic strength of the solution in which they are suspended. Here, we exhibit an approach to adjust the surface charge of colloidal particles and then their electrostatic interaction by exposure UV light.[1] And then, we demonstrate the oppositely charged gold nanoparticles are decorated on the colloids. Figure 1 shows that the overall reaction procedures of photoswitchable DNQ conjugated silica and polymer colloids. First, amine fuctionalized silica colloids are manufactured by modified stober reaction, and amine functionalized PS colloids are synthesized by emulsifier-free emulsion polymerizations. In these amine groups containing colloids are reacted with photoswithchable DNQ molecules on the colloid surfaces. Upon UV irradiation, the DNQ-conjugated silica and polymer colloids was rendered hydrophilic carboxylic acid or carboxyl ions due to photogeneration of the indenecarboxylic acid groups from the hydrophobic DNQ via photochemical Wolff rearrangement. The typical example results show that colloidal suspensions of DNQ-conjugated aminated PS particles were systematically exposure to UV light as increasing the time variations. The zeta potential varied from initially positively charged (+18mV) and reached in negatively charged (-35mV). In these state, we can successively positively charge gold nanoparticles decorated on the photoswitched PS colloids. (Figure 2).

Figure 1 Overall reaction procedures of photoswitchable DNQ conjugated colloidal crystals

Figure 2 TEM images of DNQ-conjugated silica (a) and polymer (e) colloids: (b), (c), (f), and (g) image shows that positively charged gold nanoparticles are decorated on the DNQ-conjugated silica and polymer colloids after exposure UV light. (d) and (h) shows that TEM image of the same samples after the growth of a thin outer gold layer.

Now, we are also interesting colloidal crystal assembling of DNQ-conjugated silica and polymer colloids.

Reference

1 K. N. Plunkett, A. Mohraz, R. T. Haasch, J. A. Lewis, And J. S. Moore, JACS, 2005, 127, 14574.

 

---