Ramirez Hoyos, Patricio
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- PublicationElectrical conductance of conical nanopores: Symmetric and asymmetric salts and their mixtures(American Institute of Physics, 2022-10-14) Ramirez Hoyos, Patricio; Cervera, Javier; Manzanares, José A.; Nasir, Saima; Ali, Mubarak; Ensinger, Wolfgang; Mafe, Salvador; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Agencia Estatal de Investigación; European Regional Development Fund; Ministerio de Ciencia, Innovación y Universidades; Hessisches Ministerium für Wissenschaft und Kunst, Alemania[EN] We have studied experimentally the electrical conductance-voltage curves of negatively and positively charged conical nanopores bathed in ionic solutions with monovalent, divalent, and trivalent cations at electrochemically and biologically relevant ionic concentrations. To better understand the interaction between the pore surface charge and the mobile ions, both single salts and salt mixtures have been considered. We have paid attention to the effects on the conductance of the cation valency, the pore charge asymmetry, and the pore charge inversion phenomena due to trivalent ions, both in single salts and salt mixtures. In addition, we have described how small concentrations of multivalent ions can tune the nanopore conductance due to monovalent majority ions, together with the effect of these charges on the additivity of ionic conductance and fluoride-induced negative differential conductance phenomena. This compilation and discussion of previously presented experimental data offers significant insights on the interaction between fixed and mobile charges confined in nanoscale volumes and should be useful in establishing and checking new models for describing ionic transport in the vicinity of charged surfaces.
- PublicationEnergy transduction and signal averaging of fluctuating electric fields by a single protein ion channel(The Royal Society of Chemistry, 2017) Verdia-Baguena, Carmina; Gómez Lozano, Vicente; Cervera, J.; Ramirez Hoyos, Patricio; Mafe, S.; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Ministerio de EconomÃa, Industria y Competitividad[EN] We demonstrate the electrical rectification and signal averaging of fluctuating signals using a biological nanostructure in aqueous solution: a single protein ion channel inserted in the lipid bilayer characteristic of cell membranes. The conversion of oscillating, zero time-average potentials into directional currents permits charging of a load capacitor to significant steady-state voltages within a few minutes in the case of the outer membrane porin F (OmpF) protein, a bacterial channel of Escherichia coli. The experiments and simulations show signal averaging effects at a more fundamental level than the traditional cell and tissue scales, which are characterized by ensembles of many ion channels operating simultaneously. The results also suggest signal transduction schemes with bio-electronic interfaces and ionic circuits where soft matter nanodiodes can be coupled to conventional electronic elements.
- PublicationSurface charge regulation of functionalized conical nanopore conductance by divalent cations and anions(Elsevier, 2019-12-01) Ramirez Hoyos, Patricio; Manzanares, José A.; Cervera Montesinos, Javier; Gómez Lozano, Vicente; Ali, Mubarak; Nasir, Saima; Ensinger, Wolfgang; Mafé, Salvador; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Agencia Estatal de Investigación; Hessisches Ministerium für Wissenschaft und Kunst, Alemania[EN] The surface charge regulation in nanoscale volumes is a subject of wide interest to biological and chemical soft matter systems. Also, electrolyte mixtures with monovalent and divalent ions are commonplace in practical applications with micro and nanoporous ion-exchange membranes. We have studied experimentally and theoretically the conductance of conical nanopores functionalized with negative and positive surface charges that are bathed by electrolyte mixtures of the monovalent ions K+ and Cl- and the divalent ions Mg2+, Ba2+, Ca2+, and SO42-. Small concentrations of these ions can modulate the nanopore selectivity and conductance because of their interaction with the charged groups on the pore surface. We have also given a qualitative description of the surface charge regulation using a simplified model for multivalent ion mixtures.
- PublicationBiomolecular conjugation inside synthetic polymer nanopores via glycoprotein-lectin interactions(Royal Society of Chemistry, 2011-03-18) Mubarak, Ali; Ramirez Hoyos, Patricio; Tahir, Muhammad Nawaz; Mafé, Salvador; Siwy, Zuzanna S.; Neumann, Reinhard; Tremel, W.; Ensinger, Wolfgang J.; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsicaWe demonstrate the supramolecular bioconjugation of concanavalin A (Con A) protein with glycoenzyme horseradish peroxidase (HRP) inside single nanopores, fabricated in heavy ion tracked polymer membranes. Firstly, the HRP-enzyme was covalently immobilized on the inner wall of the pores using carbodiimide coupling chemistry. The immobilized HRP-enzyme molecules bear sugar (mannose) groups available for the binding of Con A protein. Secondly, the bioconjugation of Con A on the pore wall was achieved through its biospecific interactions with the mannose residues of the HRP enzyme. The immobilization of biomolecules inside the nanopore leads to the reduction of the available area for ionic transport, and this blocking effect can be exploited to tune the conductance and selectivity of the nanopore in aqueous solution. Both cylindrical and conical nanopores were used in the experiments. The possibility of obtaining two or more conductance states (output), dictated by the degree of nanopore blocking resulted from the different biomolecules in solution (input), as well as the current rectification properties obtained with the conical nanopore, could also allow implementing information processing at the nanometre scale. Model simulations based on the transport equations further verify the feasibility of the sensing procedure that involves concepts from supramolecular chemistry, molecular imprinting, recognition, and nanotechnology. © 2011 The Royal Society of Chemistry.
- PublicationSingle cigar-shaped nanopores functionalized with amphoteric amino acid chains: experimental and theoretical characterization(American Chemical Society, 2012) Ali, Mubarak; Ramirez Hoyos, Patricio; Nguyen, Hung Quoc; Nasir, Saima; Cervera, Javier; Mafe, Salvador; Ensinger, Wolfgang; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Ministerio de Ciencia e InnovaciónWe 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). © 2012 American Chemical Society.
- PublicationNanopore charge inversion and current-voltage curves in mixtures of asymmetric electrolytes(Elsevier, 2018) Ramirez Hoyos, Patricio; Manzanares, José Antonio; Cervera Montesinos, Javier; Gómez Lozano, Vicente; Ali, Mubarak; Pause, Isabelle; Ensinger, Wolfgang; Mafé, Salvador; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Ministerio de EconomÃa y Competitividad[EN] We consider the screening of the negative charges (carboxylic acid groups) fixed on the surface of a conical-shaped track-etched nanopore by divalent magnesium (Mg2+) and trivalent lanthanum (La3+). The experimental current (I)-voltage (V) curves and current rectification ratios allow discussing fundamental questions about the overcompensation of spatially-fixed charges by multivalent ions over nanoscale volumes. The effects of charge inversion or reversal on nanopore transport are discussed in mixtures of asymmetric electrolytes (LaCl3 and MgCl2 with KCl). In particular, pore charge inversion is demonstrated for La3+ as well as for mixtures of this trivalent ion at low concentrations with monovalent potassium (K+) and divalent Mg2+ ions at biologically relevant concentrations. It is found that small concentrations of multivalent ions can modulate the nanopore rectification and the transport of other majority ions in the solution. We study also the kinetics of the nanopore electrical recovery when the electrolyte solutions bathing the single-pore membrane are changed and show the hysteretic effects observed in the I-V curves. Finally, we describe the hysteresis observed in the I-V curves of CaCl2, MgCl2, and BaCl2 and mixtures. We also give a qualitative description of the effects of charge reversal on the pore rectification using the Nernst-Planck flux equations for multivalent ion mixtures.
- PublicationMemristive arrangements of nanofluidic pores(American Physical Society, 2024-04-24) Ramirez Hoyos, Patricio; Portillo, Sergio; Cervera, Javier; Bisquert, Juan; Mafe, Salvador; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Generalitat Valenciana; Agencia Estatal de Investigación[EN] We demonstrate that nanofluidic diodes in multipore membranes show a memristive behavior that can be controlled not only by the amplitude and frequency of the external signal but also by series and parallel arrangements of the membranes. Each memristor consists of a polymeric membrane with conical nanopores that allow current rectification due to the electrical interaction between the ionic solution and the pore surface charges. This surface charge-regulated ionic transport shows a rich nonlinear physics, including memory and inductive effects, which are characterized here by the current-voltage curves and electrical impedance spectroscopy. Also, neuromorphiclike potentiation of the membrane conductance following voltage pulses (spikes) is observed. The multipore membrane with nanofluidic diodes shows physical concepts that should have application for information processing and signal conversion in iontronics hybrid devices.
- PublicationHybrid Circuits with Nanofluidic Diodes and Load Capacitors(American Physical Society, 2017) Ramirez Hoyos, Patricio; GarcÃa-Morales, V.; Gómez Lozano, Vicente; Ali, Mubarak; Nasir, Saima; Ensinger, Wolfgang; Mafe, Salvador; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Ministerio de EconomÃa, Industria y Competitividad[EN] The chemical and physical input signals characteristic of micro- and nanofluidic devices operating in ionic solutions should eventually be translated into output electric currents and potentials that are monitored with solid-state components. This crucial step requires the design of hybrid circuits showing robust electrical coupling between ionic solutions and electronic elements. We study experimentally and theoretically the connectivity of the nanofluidic diodes in single-pore and multipore membranes with conventional capacitor systems for the cases of constant, periodic, and white-noise input potentials. The experiments demonstrate the reliable operation of these hybrid circuits over a wide range of membrane resistances, electrical capacitances, and solution pH values. The model simulations are based on empirical equations that have a solid physical basis and provide a convenient description of the electrical circuit operation. The results should contribute to advance signal transduction and processing using nanoporebased biosensors and bioelectronic interfaces.
- PublicationTetraalkylammonium Cations Conduction through a Single Nanofluidic Diode: Experimental and Theoretical Studies(2017) Ali, Mubarak; Ramirez Hoyos, Patricio; Nasir, Saima; Cervera Montesinos, Javier; Mafe, Salvador; Ensinger, Wolfgang; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Hessisches Ministerium für Wissenschaft und Kunst, Alemania; Ministerio de EconomÃa, Industria y Competitividad; European Regional Development Fund[EN] We describe experimentally and theoretically the concentration-dependent conduction of tetraalkylammonium (TAA+) cations through a nanofluidic diode fabricated in a polymer membrane via asymmetric track-etching techniques. This single-pore membrane exhibits current rectification characteristics because of the ionized carboxylate groups on the pore surface. We use aqueous solutions of potassium (K+ ), ammonium (A+ ), tetramethylammonium (TMA+ ), tetraethylammonium (TEA+ ), and tetrabutylammonium (TBA+ ) ions with concentrations ranging from 50 to 500 mM under acidic (pH 3.5) and physiological (pH 6.5) conditions. Compared with the K+ and A+ ions, the TMA+ , TEA+ , and TBA+ ions show relatively low rectified ion currents because the cation hydrophobicity increases with the alkyl chain. At low concentrations and acidic conditions, an inversion in the current rectification characteristics is observed, which is attributed to the adsorption of the organic cations on the pore surfaces. The experimental results can be analyzed in terms of the Poisson-Nernst-Planck equations and the geometrical and electrical single pore characteristics for the different ions, pH values, and salt concentrations employed. This theoretical approach is qualitative and could be extended further to include a self-consistent theoretical treatment of the ionic adsorption and surface charge equilibria
- PublicationNet currents obtained from zero-average potentials in single amphoteric nanopores(Elsevier, 2013-06) Ramirez Hoyos, Patricio; Gómez Lozano, Vicente; Ali, Mubarak; Ensinger, Wolfgang; Mafé, Salvador; Departamento de FÃsica Aplicada; Escuela Técnica Superior de Arquitectura; Centro de TecnologÃas FÃsicas: Acústica, Materiales y AstrofÃsica; Ministerio de EconomÃa y CompetitividadWe have studied experimentally and theoretically the rectifying properties of a single asymmetric nanopore functionalized with amphoteric lysine groups and characterized the net current obtained with zero-average time dependent potentials. The pH-controlled rectification phenomena may be relevant to bio-electrochemistry, pH sensing and regulation, and energy conversion. (C) 2013 Elsevier B.V. All rights reserved.