Communications film, resulting in terraces of bilayer steps. The regions of arachidic acid in the mixed LB film can be removed by washing in ethanol to leave behind islands of cadmium arachidate molecules. ExperimentalLangmuir-Blodgett films of arachidic acidicadmium arachidate were prepared using a constant-perimeter barrier trough (purpose-built) located in a Class 10000 microelectronics clean room. The subphase was ultrapure water obtained from a commercial reverse osmosisideionizationiUV sterilization system. The arachidic acid (eicosanoic acid) was obtained from Sigma (99 % purity). For salt formation, CdCIp (BDH, Analar Grade) was added to the suhphase to give an overall concentration of 2.5 x lo4 M. The pH was adjusted to 5.7i0.1 by the addition of HCI (BDH, Aristar Grade) or ammonia solution (BDH, Aristar Grade). Transfer of the floating monolayers onto hydrophilic silicon wafers ((100) orientation) was undertaken at a suhphase temperature of 19i1 "C and a deposition pressure of 30 mN m-'. The dipping speed was 2 mm m i d . Transfer ratios for all the monolayers deposited were 1.0oi0.05.A Digital Instruments Nanoscope Ill atomic force microscope was used to examine the topographical nature of the arachidic acidicadmium arachidate LB film surface following dipping and after washing in ethanol (to remove the free acid). All of the high resolution AFM images were acquired in air at room temperature using the contact mode and a 1 pm x 1 pm piezoelectric scan head. A 200 pm narrow-legged silicon nitride cantilever with a small spring-constant ( k = 0.06 Nm-') was used to minimize film damage due to high contact forces. The lower resolution images were acquired in air using the tapping mode in conjunction with a 10 ym x 10 Fm piezoelectric scan head. This technique employs a stiff silicon cantilever oscillating at a large amplitude near its resonance frequency (several hundred kilohertz) which is detected by an optical beam system. AFM images are presented as unfiltered data in gray-scale and were found to be stable and unchanged over long periods of observation.

Anisotropic textured surfaces allow water striders to walk on water, butterflies to shed water from their wings and plants to trap insects and pollen. Capturing these natural features in biomimetic surfaces is an active area of research. Here, we report an engineered nanofilm, composed of an array of poly(p-xylylene) nanorods, which demonstrates anisotropic wetting behaviour by means of a pin-release droplet ratchet mechanism. Droplet retention forces in the pin and release directions differ by up to 80 μN, which is over ten times greater than the values reported for other engineered anisotropic surfaces. The nanofilm provides a microscale smooth surface on which to transport microlitre droplets, and is also relatively easy to synthesize by a bottom-up vapour-phase technique. An accompanying comprehensive model successfully describes the film's anisotropic wetting behaviour as a function of measurable film morphology parameters.

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A new approach for the selective electroless (EL) metallization of surfaces is described. Surfaces are modified with a chemisorbed ligand-bearing organosilane film, and then catalyzed with an aqueous Pd(II) catalyst solution. The catalyzed substrate is then immersed in an EL metal deposition bath to complete the metallization process. The ligating surfaces are produced by molecular self-assembly of 2-(trimethoxysilyl)ethyl-2-pyridine (PYR) on silicon or silica substrates. The catalyst consists of chloride-containing aqueous Pd(II) solutions buffered at pH 5.0 to 6.4; oligomeric chloro and/or hydroxo-bridged Pd(II) complexes act as the catalytic species at the surface. The activity of the catalyst has been characterized and modeled as a function of solution pH, [C1-], and time from preparation. Adhesion of the Pd(II) EL catalyst to the substrate involves covalent bond formation with the surface ligand. An average minimum Pd(II) level on the surface of -10 '~ Pd atom cm 2 is shown to be necessary to initiate EL metallization of the substrate with an EL Co bath. This process involves fewer steps and displays improved selectivity compared to processes that involve a conventional Pd/Sn catalyst. Fabrication of high resolution metal patterns using the new metallization chemistry in conjunction with deep UV patterning of PYR films is demonstrated.

Designing coupled vibrational-cavity polariton systems modify chemical reaction rates and paths requires an understanding of how this coupling depends on system parameters (i.e. absorber strength, modal distribution, and vibrational absorber and cavity linewidths). Here, we evaluate the impact of absorption coefficient and cavity design on normal mode coupling between a FabryPérot cavity and a molecular vibration. For a vibrational band of urethane in a polymer matrix, the coupling strength increases with its concentration so that the system spans the weak and strong coupling regimes. The experimentally-determined Rabi splitting values are in excellent agreement with an analytical expression derived for classical coupled oscillators that includes no fitting parameters. Also, the cavity mode profile is altered through choice of mirror type with metal mirrors resulting in stronger confinement, and thus coupling, while dielectric stack mirrors provide higher transmission for a given cavity quality factor, and decreased coupling due to greater mode penetration into the dielectric mirror. In addition to polymers, the cavities can couple to molecular vibrational bands of dissolved species in solution, which greatly expands the range of systems that can be explored. Finally, longer pathlength cavities are used to demonstrate the pathlength-independence of the coupling strength. The ability to adjust the cavity linewidth, through the use of higher order modes, represents a route to match the cavity dephasing time to that of the molecular vibration and may be applied to a range of molecular systems. Understanding the roles of cavity design and validating empirical and analytical descriptions of absorber properties on coupling strength will facilitate application of these strong coupling effects to enable currently unreachable chemistries.Coupling between an optically-driven material excitation (e.g., a semiconductor quantum dot excitonic absorption) and a confined optical-mode (e.g., an optical microcavity) can drastically alter the behavior of both modes. Strong coupling, which occurs when the two modes are in resonance and the interaction between the two exceeds the damping rate, produces two hybridized states whose fundamental character is a quantum-mechanical superposition of the two original modes. Each of these mixed-character eigenstates is shifted from the original resonant frequency by half the Rabi splitting, Ω. 1 Such coupled systems are variously referred to as cavity polaritons, 2 coupled normal modes, 1 plexcitons 3 , or simply coupled normal modes. If the system consists of a single quantum oscillator (twolevel atom, single quantum dot, etc.) interacting with a single cavity photon, nonlinear effects such as photon blocking and climbing of the Jaynes-Cummings ladder may occur. The splitting in such a system is referred to as vacuum Rabi splitting 1,4,5 as opposed to simply Rabi or polariton splitting associated with ensembles of individual oscillators, as described herein. Relaxation lifetimes, 6,7 linewidt...