Search

Poly(anilineboronic acid) (PABA)/ribonucleic acid (RNA) multilayer films were prepared under neutral condition using a layer-by-layer deposition of PABA and RNA. RNA was used both as a polyelectrolyte for multilayer formation as well as dopant for PABA. Photoelastic modulated infrared reflection absorption spectroscopy measurements suggest that PABA interacts covalently with RNA through the formation of a boronate ester, a boron-nitrogen dative bond, as well as electrostatic interactions of anionic phosphates with cationic amines. The deposition procedure was monitored with UV-vis absorption spectroscopy, showing a linear dependence of absorbance with the number of PABA/RNA bilayers deposited. The multilayer films were further characterized using X-ray photoelectron spectroscopy and ellipsometry, which yielded a PABA/RNA bilayer thickness of approximately 10 nm. The PABA/RNA multilayer films are redox-active at neutral pH, consistent with the formation of a self-doped polymer. Electrochemical control of PABA under these conditions allows potential-induced controlled release of RNA from a multilayer at neutral pH, suggesting that this may serve as a novel method for controlled release of RNA under physiological conditions.

Selective preparation of self-assembled monolayers (SAMs) on gold was accomplished by electrolysis of alkylthiosulfates (Bunte salts) in tetrahydrofuran in the presence of tetrabutylammonium tetrafluoroborate as the supporting electrolyte. Tetrafluoroborate ions inhibited the spontaneous chemisorption of alkylthiosulfates to form monolayers, so that monolayers formed only on gold electrodes at a sufficiently oxidative potential. This oxidative potential was applied using square-wave pulses, and as expected, the degree of completeness of the monolayers depended upon both the voltage and the period during which it was applied. Using this method, monolayers could be formed quickly, in only twenty 5-s pulses. X-ray photoelectron spectroscopy and infrared spectroscopy supported our hypothesis that this process involves formation of stable gold−thiolate bonds at the gold surface and that (bi)sulfate is a side-product under our experimental conditions. Unlike the preparation of SAMs from alkanethiols, clean gold...

Alkanethiolates in self-assembled monolayers on gold oxidize in air, in the dark, to form sulfinates and sulfonates. The kinetics of oxidation, however, vary depending on the morphology of the underlying gold, with the rate of oxidation increasing dramatically with a decrease in the size of the grains and the amount of Au(111) on the surface. This difference in kinetics of oxidation is sufficiently great that it may provide insight into discrepancies among previous reports in the literature regarding the inertness of these SAMs in air. The oxidized products also desorb readily, and these species decompose under prolonged X-ray irradiation in ultrahigh vacuum.