Search

The fabrication and properties of 'fluoroalkylated paper' ('RF paper') by vapor-phase silanization of paper with fluoroalkyl trichlorosilanes is reported. RF paper is both hydrophobic and oleophobic: it repels water ( θappH2 O>140°), organic liquids with surface tensions as low as 28 mN m-1, aqueous solutions containing ionic and non-ionic surfactants, and complex liquids such as blood (which contains salts, surfactants, and biological material such as cells, proteins, and lipids). The propensity of the paper to resist wetting by liquids with a wide range of surface tensions correlates with the length and degree of fluorination of the organosilane (with a few exceptions in the case of methyl trichlorosilane-treated paper), and with the roughness of the paper. RF paper maintains the high permeability to gases and mechanical flexibility of the untreated paper, and can be folded into functional shapes (e.g., microtiter plates and liquid-filled gas sensors). When impregnated with a perfluorinated oil, RF paper forms a 'slippery' surface (paper slippery liquid-infused porous surface, or 'paper SLIPS') capable of repelling liquids with surface tensions as low as 15 mN m-1. The foldability of the paper SLIPS allows the fabrication of channels and flow switches to guide the transport of liquid droplets. [ABSTRACT FROM AUTHOR]

Analysis of rates of tunneling across self-assembled monolayers (SAMs) of n-alkanethiolates SCn (with n = number of carbon atoms) incorporated in junctions having structure AgTS-SAM//Ga2O3/EGaIn leads to a value for the injection tunnel current density J0 (i.e., the current flowing through an ideal junction with n = 0) of 103.6±0.3 A·cm-2 (V = +0.5 V). This estimation of J0 does not involve an extrapolation in length, because it was possible to measure current densities across SAMs over the range of lengths n = 1-18. This value of J0 is estimated under the assumption that values of the geometrical contact area equal the values of the effective electrical contact area. Detailed experimental analysis, however, indicates that the roughness of the Ga2O3 layer, and that of the AgTS-SAM, determine values of the effective electrical contact area that are ~10-4 the corresponding values of the geometrical contact area. Conversion of the values of geometrical contact area into the corresponding values of effective electrical contact area results in J0(+0.5 V) = 107.6±0.8 A·cm-2, which is compatible with values reported for junctions using top-electrodes of evaporated Au, and graphene, and also comparable with values of J0 estimated from tunneling through single molecules. For these EGaIn-based junctions, the value of the tunneling decay factor β (β = 0.75 ± 0.02 Å-1; β = 0.92 ± 0.02 nC-1) falls within the consensus range across different types of junctions (β = 0.73-0.89 Å-1; β = 0.9-1.1 nC-1). A comparison of the characteristics of conical Ga2O3/EGaIn tips with the characteristics of other top-electrodes suggests that the EGaIn-based electrodes provide a particularly attractive technology for physical-organic studies of charge transport across SAMs. [ABSTRACT FROM AUTHOR]