The present results demonstrate that transparent conductive epitaxial ITO films with atomically flat and stepped surfaces are vital for the lateral growth of organic molecules, taking vanadyl phthalocyanine (VOPc) as an example. Laterally grown organic molecules on transparent conductive substrates are essential for an emerging molecular electronics technology. Further, an epitaxial layer of VOPc on ITO films would provide new information to clarify the mechanism of improved hole-injection performance in OLEDs.Experimental YSZ (111) substrate was annealed at 1350 C in air to obtain an atomically flat surface [24]. The substrate temperature was maintained at 900 C during the film growth. An ITO (In 2 O 3 doped with 10 wt.-% SnO 2 ) ceramic target was set at the center of a PLD chamber. A YSZ substrate was positioned opposite to the target. The distance between the substrate and the target was 30 mm. The background pressure of the PLD chamber was 2 10 ±6 Pa, while the oxygen pressure during the growth was fixed at 3.0 10 ±3 Pa. An ITO film was grown on the rotating substrate by focusing a KrF excimer laser beam (k = 248 nm, pulse duration 20 ns, repetition frequency 10 Hz, photon energy density~1 J cm ±2 per pulse) onto the rotating target. The growth rate was 2 nm min ±1. The ITO film used as a substrate for VOPc layer growth was placed in an ultrahigh-vacuum MBE vessel (Eiko EVA-1000) [25] and preheated at 300 C for 2 h in the vessel. The base pressure of the vessel was 1 10 ±7 Pa. The substrate temperature was kept at 150 C [26] during the VOPc layer growth, while K-cell temperature was set at 245 C. The growth rate of VOPc, monitored by a quartz oscillator, was~1 nm min ±1. The crystalline quality and orientation of VOPc and ITO were analyzed by high-resolution X-ray diffraction measurements (HR-XRD, ATX-G, Rigaku Co.). Out-of-plane XRD (separate scan of 2h and x in the horizontal plane), inplane XRD (separate scan of 2hv and u in the azimuthal plane), out-of-plane rocking curve (2h fixed x scan), and in-plane rocking curve (2hd fixed u scan) measurements were performed. Surface morphologies of the VOPc layers were observed by AFM (SPI-3800N, S.I.I.) at room temperature in air.

Model surfaces with switchable functionality based on nanopatterned, thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes were fabricated using interferometric lithography combined with surface-initiated polymerization. The temperature-triggered hydration and conformational changes of nanopatterned PNIPAAm brushes reversibly modulate the spatial concealment and exposure of molecules that are immobilized in the intervals between nanopatterned brushes. A biocidal quaternary ammonium salt (QAS) was used to demonstrate the utility of nanopatterned PNIPAAm brushes to control biointerfacial interactions with bacteria. QAS was integrated into polymer-free regions of the substrate between nanopatterned PNIPAAm brushes. The biocidal efficacy and release properties of these surfaces were tested against Escherichia coli K12. Above the lower critical solution temperature (LCST) of PNIPAAm, desolvated, collapsed polymer chains facilitate the attachment of bacteria and expose QAS moieties that kill attached bacteria. Upon a reduction of the temperature below the LCST, swollen PNIPAAm chains promote the release of dead bacteria. These results demonstrate that nanopatterned PNIPAAm/QAS hybrid surfaces are model systems that exhibit an ability to undergo noncovalent, dynamic, and reversible changes in structure that can be used to control the attachment, killing, and release of bacteria in response to changes in temperature.

A series of water soluble, cationic conjugated polyelectrolytes (CPEs) with backbones based on a poly(phenylene ethynylene) repeat unit structure and tetraakylammonium side groups exhibit a profound light-induced biocidal effect. The present study examines the biocidal activity of the CPEs, correlating this activity with the photophysical properties of the polymers. The photophysical properties of the CPEs are studied in solution, and the results demonstrate that direct excitation produces a triplet excited-state in moderate yield, and the triplet is shown to be effective at sensitizing the production of singlet oxygen. Using the polymers in a format where they are physisorbed or covalently grafted to the surface of colloidal silica particles (5 and 30 microm diameter), we demonstrate that they exhibit light-activated biocidal activity, effectively killing Cobetia marina and Pseudomonas aeruginosa. The light-induced biocidal activity is also correlated with a requirement for oxygen suggesting that interfacial generation of singlet oxygen is the crucial step in the light-induced biocidal activity.

This report presents a study of electrokinetic transport in a series of integrated macro- to nano-fluidic chips that allow for controlled injection of molecular mixtures into high-density arrays of nanochannels. The high-aspect-ratio nanochannels were fabricated on a Si wafer using interferometric lithography and standard semiconductor industry processes, and are capped with a transparent Pyrex cover slip to allow for experimental observations. Confocal laser scanning microscopy was used to examine the electrokinetic transport of a negatively charged dye (Alexa 488) and a neutral dye (rhodamine B) within nanochannels that varied in width from 35 to 200 nm with electric field strengths equal to or below 2000 V m-1. In the negatively charged channels, nanoconfinement and interactions between the respective solutes and channel walls give rise to higher electroosmotic velocities for the negatively charged dye than for the neutral dye, towards the negative electrode, resulting in an anomalous separation that occurs over a relatively short distance (<1 mm). Increasing the channel widths leads to a switch in the electroosmotic transport behavior observed in microscale channels, where neutral molecules move faster because the negatively charged molecules are slowed by the electrophoretic drag. Thus a clear distinction between "nano-" and "microfluidic" regimes is established. We present an analytical model that accounts for the electrokinetic transport and adsorption (of the neutral dye) at the channel walls, and is in good agreement with the experimental data. The observed effects have potential for use in new nano-separation technologies.