Oil|Water Interfacial Phosphate Transfer Facilitated by Boronic Acid: Observation of Unusually Fast Oil|Water Lateral Charge Transport

Anion transfer for highly hydrophilic phosphate and hydroxide anions into a water-immiscible organic phase, 3-(4-phenylpropyl)-pyridine (or PPP), is driven with the tetraphenylporphyrinato manganese(II/III) (or TPPMn) redox system and facilitated with a hydrophobic oil-based boronic acid ((3-(1,3-dioxo-6-propylamino-1H-benzo[de]isoquinolin-2(3 H)-yl)phenyl)boronic acid). Both 1) experiments with random arrays of microdroplets (transient) and 2) experiments in a gold–gold dual-plate oil-filled microtrench generator-collector configuration (approaching steady state), show that phosphate transfer is facilitated by boronic acid. At pH 7.5 a switch in mechanism occurs from phosphate transfer to hydroxide transfer. Accelerated charge transport is observed lateral to the oil|water interface. Improved boronic acid facilitators and nanotrench electrodes are discussed in terms of future feasibility for phosphate sensing applications.