title: Single cigar-shaped nanopores functionalized with amphoteric amino acid chains: experimental and theoretical characterization.
abstract: We present an experimental and theoretical characterization of single cigar-shaped nanopores with pH-responsive carboxylic acid and lysine chains functionalized on the pore surface. The nanopore characterization includes (i) optical images of the nanostructure obtained by FESEM; (ii) different chemical procedures for the nanopore preparation (etching time and functionalizations; pH and electrolyte concentration of the external solution) allowing externally tunable nanopore responses monitored by the current-voltage (I-V) curves; and (iii) transport simulations obtained with a multilayer nanopore model. We show that a single, approximately symmetric nanopore can be operated as a reconfigurable diode showing different rectifying behaviors by applying chemical and electrical signals. The remarkable characteristics of the new nanopore are the sharp response observed in the I-V curves, the improved tunability (with respect to previous designs of symmetric nanopores) which is achieved because of the direct external access to the nanostructure mouths, and the broad range of rectifying properties. The results concern both fundamental concepts useful for the understanding of transport processes in biological systems (ion channels) and applications relevant for tunable nanopore technology (information processing and drug controlled release).
authors.affiliation: Department of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, D-64287 Darmstadt, Germany. m.ali@gsi.de
authors.forename: Mubarak
authors.initials: M
authors.lastname: Ali
authors.forename: Patricio
authors.initials: P
authors.lastname: Ramirez
authors.forename: Hung Quoc
authors.initials: HQ
authors.lastname: Nguyen
authors.forename: Saima
authors.initials: S
authors.lastname: Nasir
authors.forename: Javier
authors.initials: J
authors.lastname: Cervera
authors.forename: Salvador
authors.initials: S
authors.lastname: Mafe
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Ensinger
mesh_terms: D002264:Carboxylic Acids / Q000737:chemistry*; D004553:Electric Conductivity; D004563:Electrochemistry; D006863:Hydrogen-Ion Concentration; D008128:Logic; D008239:Lysine / Q000737:chemistry*; D008962:Models, Theoretical; D058608:Nanopores; D013499:Surface Properties
chemical_list: D002264:Carboxylic Acids; D008239:Lysine