A simple strategy for one-step fabrication of tris(bipyridine)ruthenium(II) (Ru(bpy))-functionalized metal-organic framework (Ru-MOF) thin films using a self-assembly approach assisted by an electrochemical way was introduced. In this protocol, the electrochemically driven cooperative reaction of Ru(bpy) as an electrochemiluminescent (ECL) probe and a structure-directing agent, trimesic acid (Hbtc) as a ligand, and Zn(NO) as the Zn source leads to an one-step and simultaneous synthesis and deposition of the MOF onto the electrode surface. Characterization of the Ru-MOF thin films was performed with scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Scanning ion conductance microscopy was specially applied in situ to image the topography and thickness of the Ru-MOF thin films. The Ru-MOF thin films as a sensing platform show excellent ECL behavior because of plenty of Ru(bpy) molecules encapsulated in the frameworks. On the basis of the Ru-MOF modified electrodes, an ultrasensitive label-free ECL immunosensing method for the human heart-type fatty-acid-binding protein has been developed with a wide linear response range (150 fg mL-150 ng mL) and a very low limit of detection (2.6 fg mL). The prepared immunosensor also displayed excellent stability and good specificity in the test of practical samples.

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The study of behaviors of ionic current rectification (ICR) in organic solutions with quartz nanopipettes is reported. ICR can be observed even in organic solutions using quartz pipettes with diameters varied from several to dozens of nanometers, and the direction of ICR is quite different from the ICR observed in aqueous phase. The influences of pore size, electrolyte concentration, and surface charge on the ICR have been investigated carefully. Water in organic solutions affects the direction and extent of ICR significantly. Mechanisms about the formation of an electrical double layer (EDL) on silica in organic solutions with different amount of water have been proposed. An improved method, which can be employed to detect trace water in organic solutions, has been implemented based on Au ultramicroelectrodes with cathodic differential pulse stripping voltammetry.