Chaoying Ni

Poly(ethylene oxide) Single Crystals as Templates for Au Nanoparticle Patterning and Asymmetrical Functionalization

Considerable attention has been paid to nanoparticle (NP) research because of their fascinating properties and potential applications in nanotechnology and biotechnology. Asymmetrically functionalizing NP is of particular interest because it could directly lead to controlled patterning of NPs for a variety of applications. In this article, we report using 2-dimensional poly(ethylene oxide) (PEO) lamellar single crystals to create a patterned functional (thiol) surface and to immobilize gold NPs (AuNPs). We demonstrate that patterning AuNPs could be achieved by incubating these single crystals with gold sol and the AuNP areal density could be easily controlled by polymer molecular weight as well as the incubation time. Melting and recrystallization of the AuNPcovered PEO single crystals led to dewetting of PEO. AuNP chains were also observed during the recrystallization process, which was attributed to the dendritic growth of edge-on PEO crystals. Furthermore, this unique technique also enables asymmetric functionalization of AuNPs. Free-standing bilayer AuNP/PEO films were obtained. Dissolving PEO single crystals led to free asymmetrically functionalized AuNPs and AuNP complexes. This approach provides a novel means to pattern AuNPs and synthesize asymmetrically functionalized AuNPs. We also anticipate that this methodology could be applied to other metal or semiconductor NPs.

In Situ Electrochemical Deposition of Poly(3,4-ethylenedioxythiophene) (PEDOT)

Conjugated polymers are widely used in organic solar cells, chemical sensors and biomedical devices because of their relatively high conductivity and soft mechanical properties [1,2,3]. Electrochemical deposition has long been an important method of fabricating conjugated polymer thin films for various applications. The morphology of the films, and the corresponding performance of the devices is particularly sensitive to the detailed fabrication conditions. Previous efforts have investigated the nucleation and growth mechanisms of electropolymerized conjugated polymers, however the results are usually obtained from in-direct and lower resolution methods like UV-vis and AFM [4,5]. More detailed information with ultra-high resolution is still needed. Electrochemical liquid electron microscopy makes it possible to analyze this initial nucleation and growth process in direct imaging method in a TEM with nanometer scale resolution. This method has proven effective for the analysis of electrochemical deposition mechanisms in copper and lead [6,7]. No previous studies have examined the in situ TEM electrochemical deposition of conjugated polymers, mostly probably due to the fact that polymers are highly electron beam sensitive. This high sensitivity makes the in situ TEM imaging of conjugated polymer electrodeposition much more experimentally difficult than for inorganic materials.