Zhiwei Xiao

Versatile surface micropatterning and functionalization enabled by microcontact printing of poly(4-aminostyrene).

Microcontact printing (μCP) of polyelectrolytes is a facile and powerful method for surface micro/nanopatterning and functionalization. Poly(4-aminostyrene) (PAS) is a polyelectrolyte that can be converted to aryldiazonium salt and exhibits pH-dependent hydrophobicity. Here we demonstrate μCP of PAS and the expansion of this technique in various directions. First, the microcontact-printed PAS can be diazotized to micropattern biomolecules including DNA and protein and nanomaterials including single-walled carbon nanotubes and gold nanoparticles. Second, the diazotized PAS enables μCP of a metallic structure on a carbon surface. Third, the hydrophobic nature of PAS at the neutral pH allows the microcontact-printed PAS-based polyelectrolyte multilayer to be used as masks for wet etching. Lastly, this technique allows facile fabrication of highly engineered microparticles with a unique structure. Overall, this work has established a novel μCP platform with various potential applications.

Gel electrophoresis and Raman mapping for determining the length distribution of SWCNTs

By combining gel electrophoresis (GEP) and simultaneous Raman scattering and photoluminescence spectroscopy (SRSPL), a new method (GEP-SRSPL) was established, both theoretically and experimentally, to characterize the length distribution of individualized single-walled carbon nanotubes (SWCNTs). With an individualized SWCNT sample prepared by sonication and ultracentrifugation, both atomic force microscopy (AFM) and GEP-SRSPL were applied for examining its length distribution. The results show good agreement, which validates the GEP-SRSPL method as a viable and easy-to-operate technique in characterizing the length distribution of SWCNTs.