Monday, June 16, 2008 - 1:40 PM
Room 2 (McKimmon Conference Center)
89

Preparation and Self-Assembly of Dual-Patch Surface-Anisotropic Microspheres

Jing-Qin Cui1, Werner A. Goedel2, and Ilona Kretzschmar1. (1) the City College, the City University of New York, New York, NY, (2) Chemitz University of Technology, Chemnitz, Germany

Surface-anisotropic particles may act as building blocks for the “bottom up” assembly and self-assembly of particles into ordered structures taking advantage of their asymmetric functionalization. 1 The plasmonic 2 and electric 3 properties of surface-anisotropic particles have also been reported, as well as the widely proposed catalytic, photonic and biological applications.

Here, we present data on the preparation of dual-patch surface-anisotropic microspheres via physical vapor deposition (PVD) and electroless deposition (ELD) with the help of an acrylate membrane template 4 and a PDMS template 5. Following modification the dual-patch spheres are harvested, re-suspended in deionized water, and their convective assembly process is investigated. A specific volume of re-suspended anisotropically modified spheres is added to a cell consisting of a Teflon ring with a 1-cm inner diameter mounted on a piece of cleaned silicon (110) wafer. The liquid is allowed to evaporate and the dual-patch spheres assemble into a particle monolayer.

The silica spheres (75 ėm) trapped in the acrylate membrane are modified using PVD with gold and silver on the two exposed ends in a two-step process. The sulfate-terminated polystyrene (sPS) spheres (2.4 ėm) used in the experiments are asymmetrically modified with gold via PVD on one side followed by silver deposition via template-assisted ELD process on the opposite side. The two processes result in particles with caps of different surface morphology. The effect of combing surface roughness and asymmetric modification is of great interest to the study of particle assembly, in particular the self-orientation of the capped spheres within the monolayer.

1. G. M. Whitesides, J. P. Mathias, C. T. Seto, Science 1991, 254, 1312-1319

2. C. Charnay, A. Lee, S. Q. Man, C. E. Moran, C. Radloff, R. K. Bradley, N. J. Halas, J. Phys. Chem. B 2003, 107, 7327-7333

3. L. Hong, A. Cacciuto, E. Luijten et al, Nano Letters, 2006, 6, 2510-2514

4. H. Xu and W. A. Goedel, Langumuir 2003, 19, 4950-4952

5. J.-Q. Cui and I. Kretzschmar, Langmuir 2006, 22, 8281-8284


Back to Nanoscale and Microscale Engineering 2: Patchy and Janus Particles
Back to The 82nd ACS Colloid & Surface Science Symposium (June 15-18 2008)