Electrostatic-Gated Transport in Chemically Modified Glass Nanopore Electrodes

Abstract

Electrostatic-gated transport in chemically modified glass nanopore electrodes with orifice radii as small as 15 nm is reported. A single conical-shaped nanopore in glass, with a approximately 1 microm radius Pt disk located at the pore base, is prepared by etching the exposed surface of a glass-sealed Pt nanodisk. The electrochemical response of the nanopore electrode corresponds to diffusion of redox-active species through the nanopore orifice to the Pt microdisk. Silanization of the exterior glass surface with Cl(Me)(2)Si(CH(2))(3)CN and the interior pore surface with EtO(Me)(2)Si(CH(2))(3)NH(2) introduces pH-dependent ion selectivity at the pore orifice, a consequence of the electrostatic interactions between the redox ions and protonated surface amines. Nanopore electrodes with very small pore orifice radii (< approximately 50 nm) display anion permselectively at pH < 4, as demonstrated by electrochemical measurement of transport through the pore orifice. Ion selective transport vanishes at pH > 6 or when the pore radius is significantly larger than the Debye screening length, consistent with the observed ion selectivity resulting from electrostatic interactions. The ability to introduce different surface functionalities to the interior and exterior surfaces of glass nanopores is demonstrated using fluorescence microscopy to monitor the localized covalent attachment of 5- (and 6)-carboxytetramethylrhodamine succinimidyl ester to interior pore surfaces previously silanized with EtO(Me)(2)Si(CH(2))(3)NH(2).

Electrochemical attosyringe

“…The surface tension effects largely responsible for the liquid flow are not limited to the liquid/liquid interface but also depend on the water/glass and organic solvent/glass boundaries, and a three-phase water/organic/glass boundary. The properties of the inner pipette wall can be changed by modifying its surface (17,19). Rendering the glass surface more hydrophobic, e.g., via silanization, inhibits the ingress of water into the capillary (17).…”

Resistive-pulse and rectification sensing with glass and carbon nanopipettes

“…an antibody or a DNA aptamer) to selectively capture and detect analyte molecules with high selectivity and sensitivity [35,36] and with chemical functionalities that respond to external stimuli (e.g. pH or light) [37,38].…”

Resistive pulse sensing of magnetic beads and supraparticle structures using tunable pores

“…16 Within this range, many particle types present opportunities for improved characterization or quality control-drug delivery capsules, viruses, functionalized particles for diagnostic assays, blood platelets, emulsions, and magnetic beads are a few important examples. The sophistication of resistive pulse sensing has also increased, making use of channels made from carbon nanotubes, 17,18 glass, [19][20][21][22][23] silicon, 5,8,15,24 polymers, [25][26][27][28] and elastomers. [29][30][31][32][33][34][35][36][37][38] Resistive pulses can now be used for study and measurement of particle size, 2,3,17,18,20,21,34 concentration, 33 and charge.…”