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A network of one-dimensional (1D) Au nanoparticle necklaces is synthesized and shown to exhibit electronic switching, that is, gating, by the metabolic activity of yeast cells deposited on the structure. Without the cells, the network exhibits the Coulomb blockade effect at room temperature with a sharp threshold voltage, V(T) of approximately 0.45 V, which corresponds to a switching energy of approximately 20 kT. Although the enhancement in V(T) from approximately 70 mV for a single (10 nm) Au particle to >1 V is well-known for a 2D array, the uniqueness of the network topology is the relatively weak dependence of V(T) on temperature that leads to room temperature switching behavior, in contrast to an array where the blockade effect vanishes at ambient temperatures. The coupling between the biochemical process of the cell and the electronics of the network has potential applications for making electrodes for biofuel cells and highly sensitive biosensors using the cell as the specific sensing moiety.

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In inkless microcontact printing (IμCP) by soft lithography, the poly(dimethylsiloxane) (PDMS) stamp transfers uncured polymer to a substrate corresponding to its pattern. The spontaneous diffusion of PDMS oligomers to the surface of the stamp that gives rise to this deleterious side effect has been leveraged to fabricate a variety of devices, such as organic thin film transistors, single-electron devices, and biomolecular chips. Here we report an anomalous observation on a partially cured PDMS stamp where the transfer of oligomers onto Au occurred on regions that were not in contact with the stamp, while the surface in contact with the stamp was pristine with no polymer. On the SiO2 surface of the same chip, as expected, the transfer of PDMS occurred exclusively on regions in contact with the stamp. The printing on Au was quantified by a novel method where the submonolayer of PDMS transfer was measured by probing the local electrochemical passivation of the Au. The local transfer of polymer on SiO2 (and also Au) was measured by selective deposition of Au nanoparticle necklaces that exclusively deposited on PDMS at submonolayer sensitivity. It was discovered that the selectivity and sharpness of PDMS deposition on Au for inkless printing (i.e., negative) is significantly better than the traditional (positive) microcontact printing where the stamp is "inked" with low molecular weight PDMS.

Improvement of dye sensitized solar cell was investigated using methyl-violet dye and nanocrystalline ZnO thin film electrodes. A low cost fabrication method and low cost materials were used to prepare this photocell. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the microstructure and surface properties of dye coated ZnO electrodes. According to the XRD and SEM measurements, nanosize particles were found in ZnO film. Smaller nano-particles enhance the effective surface area; therefore the photo-current. ZnO film coated with methyl-violet dye was measured in electrolyte of KI/I 2 with secondary electrode of platinum. Cell thickness and dye coating time were varied in order to obtain optimum photo-current and photovoltage. Photo-current density around 1.33 mA/cm 2 was obtained for the ZnO films sensitized with methyl-violet dye.