Elektrochemische Untersuchungen zur Porosität von Nanoschichten auf Kohlenstoff-Basis

Die Porosität unterschiedlich hergestellter Schichten auf Kohlenstoff-Basis wurde mit Hilfe der Zyklovoltammetrie untersucht und verglichen. Die Bestimmung der Porosität erfolgte zunächst anhand der Auflösestromdichte des metallischen Substrats, auf dem die verschiedenen Schichtsysteme abgeschieden wurden. Dazu wurde das Schicht/Substrat-System einem für das Substrat Eisen korrosiven Medium ausgesetzt und der Substrat-Auflösestrom durch die Poren hindurch elektrochemisch gemessen. Als Beschichtungsverfahren kamen Aufdampfen mit anschließendem Ionenbeschuss, Plasma-aktivierte Chemische Gasphasenabscheidung sowie die Gasphasenpolymerisation zum Einsatz. Alle diese Prozesse fanden unter Vakuumbedingungen statt, bei niedrigen, substratschonenden Temperaturen. Die erhaltenen Schichten wurden mit Hilfe der Raman-Spektroskopie, Sekundärionen-Massenspektrometrie, Rasterelektronen-Mikroskopie und eines Profilometers in ihren Eigenschaften wie Zusammensetzung, Struktur und Dicke charakterisiert. Anhand der gemessenen Stromdichte-Potenzial-Kurven konnte der Einfluss verschiedener Herstellungsparameter auf die Schichtporosität untersucht werden. Dabei zeigte sich, dass sich die Porosität der meisten untersuchten Schichtsysteme mit zunehmender Schichtdicke verringert, oberhalb einer bestimmten Dicke aber wieder zunimmt, bedingt durch Rissbildung aufgrund von intrinsischem Stress. Nur bei den Polymerschichten aus Poly(para-xylylen) nimmt die Porosität mit zunehmender Schichtdicke stetig ab und es konnten schließlich porenfreie Polymerfilme ab einer Dicke von 700 nm erhalten werden. Des weiteren konnte anhand der in den Zyklovoltammogrammen beobachteten Potenzial-verschiebungen ein Modell entwickelt werden, welches die Verschiebungen erklärt und zudem weitere, komplementäre Informationen über die Gestalt der Poren in der Schicht liefern kann

Analyse des elektrochemischen Potentialrauschens zur Untersuchung des korrosiven Angriffs auf dünne Schutzschichten am Beispiel von Kohlenstoff auf Aluminium

In der vorliegenden Arbeit wurde das elektrochemische Potentialrauschen untersucht. Hierzu wurde die statistische Analyse in Form der Schnellen Fourier Transformation (FFT) genutzt. Diese Analysentechnik wurde auf beschichtete Aluminiumoberflächen angewendet. Es wurde ein Verfahren zur Analyse des elektrochemischen Potentialrauschens etabliert. Bei den Untersuchungen stand die Übertragbarkeit der Ergebnisse des reinen Metalls auf die beschichteten Oberflächen im Vordergrund. Dies erforderte den Aufbau einer elektrochemischen Messeinrichtung zur Erfassung schneller Änderungen des Potentials. Hieran wurde ein System zur Datenerfassung mit einer schnellen Messkarte und einem großen Datenspeicher angeschlossen. Das aufgebaute Messsystem und die entwickelte Software wurde mit einem Präzisionsspannungsgeber und einem Funktionsgenerator auf ihre Genauigkeit überprüft. Mit dem aufgebauten Messsystem wurden im weiteren Verlauf der Arbeit mehrere Untersuchungsreihen an unbeschichteten Aluminiumoberflächen durchgeführt. Hierbei wurde der Einfluss der Temperatur, des Oberflächenzustandes der Aluminiumproben (Poliergrad) und der Konzentration an Chloridionen in dem korrosiven Medium untersucht. Weiterhin wurden Proben in einer Sputteranlage mit unterschiedlich dünnen Kohlenstoffschichten versehen und diese sowohl mit Polarisationsmessungen wie auch mit der neuen Methode der Analyse des elektrochemischen Potentialrauschens untersucht. Wie die Ergebnisse gezeigt haben, induziert Lochkorrosion bei Aluminium niederfrequente Potentialschwankungen mit großen Amplituden. Dies zeigt sich in den FFT-Diagrammen in einem Anstieg im Niederfrequenzbereich. Die Fluktuationen entstehen aus Bruch- / Heil-Vorgängen des Oxids aus der lokalen Auflösung des Oxids, durch Anionenangriffe und aus der Entstehung von Wasserstoff in den Löchern. Diese Vorgänge setzen in den Poren der Beschichtung ein sowie an Bereichen, wo die Schicht adhäsiv versagt. Eine höhere Rate dieser Ereignisse führt zu einer höheren Anstiegsfrequenz im FFT-Diagramm. Hier bieten sich mit der Technik der statistischen Analyse des elektrochemischen Rauschens neue Untersuchungsmöglichkeiten für die Korrosion von Schicht / Substrat-Systemen

Analytik aromatischer Amine in wässrigen und biologischen Matrices. Neue Verfahren zur Anreicherung und selektiven Detektion

Aromatische Amine stellen aufgrund ihrer weiten Verbreitung und hohen Toxizität eine wichtige Gruppe von Umweltchemikalien dar. Ihre Analytik gestaltet sich schwierig, da sie als polare Verbindungen bei der erforderlichen Anreicherung Probleme bereiten. Im Rahmen dieser Arbeit wurde deshalb ein Derivatisierungsverfahren entwickelt, bei dem die Verbindungen direkt in wässriger Lösung diazotiert und durch Zugabe von Iodid zu aromatischen Iod-Verbindungen umgesetzt werden. Die Polarität der Analyten wird dadurch gemessen an den Oktanol-Wasser Verteilungskoeffizienten um durchschnittlich 2 Größenordnungen je Aminogruppe vermindert, so dass selbst polare aromatische Amine sehr gut mit Festphasenmikroextraktion (SPME) angereichert werden können. Das Verfahren ist auf ein breites Spektrum aromatischer Amine anwendbar, die sich zusammen derivatisieren und analysieren lassen. Neben alkylierten und halogenierten aromatischen Aminen ist die Derivatisierung gleichermaßen für desaktivierte nitrierte und dinitrierte sowie Diamino-Verbindungen geeignet. Die Derivate wurden mit Flüssig- wie Gaschromatographie getrennt. Mit GC-MS wurden für die untersuchten aromatischen Amine Nachweisgrenzen im unteren ng/L-Bereich erzielt. Durch die Detektion im fullscan-Modus war neben einer sicheren Identifizierung gleichzeitig der Nachweis unbekannter Verbindungen möglich. Dabei genügte ein Probevolumen von nur 10 mL, was zugleich die Voraussetzung zur Analyse biologischer Matrices schaffte. Trotz der zusätzlichen Derivatisierung waren die Reproduzierbarkeiten mit denen etablierter Verfahren zur Bestimmung aromatischer Amine vergleichbar. Mit dem Verfahren konnten zahlreiche aromatische Amine erstmals mit SPME im Abwasser von Rüstungsaltlasten bestimmt werden. Die Iod-Verbindungen ließen sich nach gaschromatographischer Trennung gezielt über einen elementselektiven Atomemissionsdetektor (GC-AED) detektieren, ohne dass Beeinträchtigungen durch Matrixkomponenten auftraten. Auf diese Weise ließen sich aromatische Amine schnell und einfach im Abwasser von Rüstungsaltlasten ausfindig machen. Die Übertragung auf komplexe Matrices erfordert zum Schutz der SPME-Faser die Extraktion aus dem Headspace. Dabei wurde das Gleichgewicht rascher erreicht, so dass bereits nach 25 min die Extraktion vieler Analyten unter Gleichgewichtsbedingungen erfolgte. Dadurch ließen sich für die Mehrzahl der Analyten die Empfindlichkeit und die Reproduzierbarkeit weiter verbessern. Mit dem Ziel einer umfassenden Untersuchung aromatischer Amine wurde das in-situ Derivatisierung-SPME-Verfahren auf Urin angewendet. Nach saurer Hydrolyse wurde eine Vielzahl iodierter Verbindungen im Urin von Rauchern gefunden. Die Derivatisierung erwies sich dabei als hochgradig selektiv, da selbst in einer derart komplexen Matrix ausschließlich die Derivate aromatischer Amine auftraten. Bei der Detektion der Iod-Verbindungen über GC-AED wurden keinerlei Störungen durch biogene Iod-Verbindungen oder andere Amine beobachtet, so dass die Belastung mit aromatischen Aminen leicht beurteilt werden konnte. Beim Vergleich der Urinproben von Rauchern und Passivrauchern wurden nur geringe Unterschiede beobachtet, wohingegen im Urin von Nichtrauchern wesentlich weniger aromatische Amine enthalten waren. Durch die parallele Detektion mit GC-AED/MS konnte anhand der Massenspektren jedem Iod-Signal ein aromatisches Amin zugeordnet werden. Insgesamt konnte die Zahl der in Urin nachgewiesenen aromatischen Amine erheblich erweitert werden. So wurden über das in-situ Derivatisierungsverfahren mit GC-MS im Urin eines Rauchers über 200 aromatische Amine als iodierte Derivate identifiziert. Es handelte sich vorwiegend um alkylierte und chlorierte Aniline. Erstmals wurden neben den Aminobiphenylen und Naphthylaminen zahlreiche alkylierte Homologe identifiziert. Das Verfahren eignete sich zudem auch für die polaren Diamino-Verbindungen und Aminophenole, von denen einige in Urin nachgewiesen wurden. Gleichzeitig wurden mit Aminopyridinen und Aminochinolinen auch einige heteroaromatische Amine gefunden

A simple and effective method for the accurate extraction of kinetic parameters using differential Tafel plots

The practice of estimating the transfer coefficient (α) and the exchange current (i0) by arbitrarily placing a straight line on Tafel plots has led to high variance in these parameters between different research groups. Generating Tafel plots by finding kinetic current, ik from the conventional mass transfer correction method does not guarantee an accurate estimation of the α and i0. This is because a substantial difference in values of α and i0 can arise from only minor deviations in the calculated values of ik. These minor deviations are often not easy to recognise in polarisation curves and Tafel plots. Recalling the IUPAC definition of α , the Tafel plots can be alternatively represented as differential Tafel plots (DTPs) by taking the first order differential of Tafel plots with respect to overpotential. Without further complex processing of the existing raw data, many crucial observations can be made from DTP which is otherwise very difficult to observe from Tafel plots. These for example include a) many perfectly looking experimental linear Tafel plots (R2 > 0.999) can give rise to incorrect kinetic parameters b) substantial differences in values of α and i0 can arise when the limiting current (iL) is just off by 5% while performing the mass transfer correction c) irrespective of the magnitude of the double layer charging current (ic), the Tafel plots can still get significantly skewed when the ratio of i0/ic is small. Hence, in order to determine accurate values of α and i0, we show how the DTP approach can be applied to experimental polarisation curves having well defined iL, poorly defined iL and no iL at all

Logic Functions with Stimuli-Responsive Single Nanopores

"This is the peer reviewed version of the following article: Logic Functions with Stimuli-Responsive Single Nanopores, which has been published in final form at https://doi.org/10.1002/celc.201300255. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."[EN] We present the concept of logic functions based on a single stimuli-responsive nanopore and analyze its potential for electrochemical transducers and actuators. The responsive molecules at the surface of the polymeric nanopore immersed in an electrolyte solution are sensitive to thermal, chemical, electrical, and optical stimuli, which are the input signals required to externally tune the conductance of the nanopore (the logical output). A single nanostructure can be operated as a resistor or as a diode with a broad range of rectifying properties, allowing for logical information-processing schemes that are useful pH and temperature sensors, electro-optical detectors, and electrochemical actuators and transducers. Some of the limitations to be addressed in practical applications are also cited.P. R., J. C., and S. M. acknowledge financial support from the Generalitat Valenciana (Project Prometeo/GV/0069), the Ministry of Economy and Competitiveness of Spain (Materials Program, project No. MAT2012-32084), and FEDER. M. A. and W. E. gratefully acknowledge financial support by the Beilstein-Institut, Frankfurt/Main, Germany, within the research collaboration NanoBiC.Ramirez Hoyos, P.; Cervera Montesinos, J.; Ali, M.; Ensinger, W.; Mafé, S. (2014). Logic Functions with Stimuli-Responsive Single Nanopores. ChemElectroChem. 1(4):698-705. https://doi.org/10.1002/celc.201300255S69870514Siwy, Z., Gu, Y., Spohr, H. 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Biomimetic smart nanopores and nanochannels. Chemical Society Reviews, 40(5), 2385. doi:10.1039/c0cs00053aWen, L., Liu, Q., Ma, J., Tian, Y., Li, C., Bo, Z., & Jiang, L. (2012). Malachite Green Derivative-Functionalized Single Nanochannel: Light-and-pH Dual-Driven Ionic Gating. Advanced Materials, 24(46), 6193-6198. doi:10.1002/adma.201202673Wen, L., Ma, J., Tian, Y., Zhai, J., & Jiang, L. (2012). A Photo-induced, and Chemical-Driven, Smart-Gating Nanochannel. Small, 8(6), 838-842. doi:10.1002/smll.201101661Jiang, Y., Liu, N., Guo, W., Xia, F., & Jiang, L. (2012). Highly-Efficient Gating of Solid-State Nanochannels by DNA Supersandwich Structure Containing ATP Aptamers: A Nanofluidic IMPLICATION Logic Device. Journal of the American Chemical Society, 134(37), 15395-15401. doi:10.1021/ja3053333Andréasson, J., Pischel, U., Straight, S. D., Moore, T. A., Moore, A. L., & Gust, D. (2011). All-Photonic Multifunctional Molecular Logic Device. 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Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism

[EN] We design and characterize a nanofluidic device for the label-free specific detection of histamine neurotransmitter based on a metal ion displacement mechanism. The sensor consists of an asymmetric polymer nanopore fabricated via ion track-etching technique. The nanopore sensor surface having metal-nitrilotriacetic (NTA-Ni2+) chelates is obtained by covalent coupling of native carboxylic acid groups with N-alpha,N-alpha-bis(carboxymethyl)-L-lysine (BCML), followed by exposure to Ni2+ ion solution. The BCML immobilization and subsequent Ni2+ ion complexation with NTA moieties change the surface charge concentration, which has a significant impact on the current-voltage (I-V) curve after chemical modification of the nanopore. The sensing mechanism is based on the displacement of the metal ion from the NTA-Ni2+ chelates. When the modified pore is exposed to histamine solution, the Ni2+ ion in NTA-Ni2+ chelate recognizes histamine through a metal ion coordination displacement process and formation of stable Ni-histamine complexes, leading to the regeneration of metal-free NTA groups on the pore surface, as shown in the current-voltage characteristics. Nanomolar concentrations of the histamine in the working electrolyte can be detected. On the contrary, other neurotransmitters such as glycine, serotonin, gamma-aminobutyric acid, and dopamine do not provoke significant changes in the nanopore electronic signal due to their inability to displace the metal ion and form a stable complex with Ni2+ ion. The nanofluidic sensor exhibits high sensitivity, specificity and reusability towards histamine detection and can then be used to monitor the concentration of biological important neurotransmitters.M.A., I.D., S.N. and W.E. acknowledge the funding from the Hessen State Ministry of Higher Education, Research and the Arts, Germany, under the LOEWE project iNAPO. P. R. and S. M. acknowledge financial support by the Spanish Ministry of Economic Affairs and Competitiveness (MAT2015-65011-P) and FEDER. The authors are also thankful to Prof. C. Trautmann, Department of Materials Research from GSI, for support with irradiation experiments.Ali, M.; Ramirez Hoyos, P.; Duznovic, I.; Nasir, S.; Mafe, S.; Ensinger, W. (2017). Label-free histamine detection with nanofluidic diodes through metal ion displacement mechanism. Colloids and Surfaces B Biointerfaces. 150:201-208. https://doi.org/10.1016/j.colsurfb.2016.11.038S20120815

Recycling of beta-Li3PS4-based all-solid-state Li-ion batteries: Interactions of electrode materials and electrolyte in a dissolution-based separation process

All-solid-state batteries are currently developed at high pace and show a strong potential for market introduction within the next years. Though their performance has improved considerably over the last years, investigation of their sustainability and the development of suitable recycling strategies have received less attention. However, their potential for efficient circular processes must be accessed comprehensively. In this article, we investigate the separation of the solid electrolyte beta-Li3PS4 from different lithium transition metal oxide electrode materials (LiCoO2, LiMn2O4, LiNi0.8Mn0.1Co0.1O2, LiFePO4, LiNi0.85Co0.1Al0.05O2 and Li4Ti5O12) via an approach based on the dissolution and subsequent recrystallization of the thiophosphate using N-methylformamide as solvent. A combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma-mass spectrometry, iodometric titration and X-ray photoelectron spectroscopy as well as electrochemical impedance spectroscopy and electrochemical characterization was used to characterize the electrolyte and electrode materials before and after separation. We find that the presence of electrode materials in the dissolution process can lead to significant chemical reactions. These interactions can (but most not) lead to strong alteration of the electrochemical characteristics of the individual compounds. Thus, we show that an efficient recovery of materials will likely depend on the precise material combination within an all-solid-state battery

Nanoparticle-induced rectification in a single cylindrical nanopore: Net currents from zero time-average potentials

Copyright 2014 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.Rectification in nanopores is usually achieved by a fixed asymmetry in the pore geometry and charge distribution. We show here that nanoparticle blocking of a cylindrical pore induces rectifying properties that can support significant net currents with zero time-average potentials. To describe experimentally this effect, the steady-state current-voltage curves of a single nanopore are obtained for different charge states and relative sizes of the pore and the charged nanoparticles, which are present only on one side. The rectification phenomena observed can find applications in the area of nanofluidics and involves physical concepts that are also characteristic of the blocking of protein ion channels by ionic drugs. © 2014 AIP Publishing LLC.M.A., S.N., Q.H.N., and W. E. acknowledge the Beilstein-Institut, Frankfurt/Main, Germany, within the research collaboration NanoBiC. P. R. and S. M. acknowledge the Ministry of Economy and Competitiveness (project MAT2012-32084) and the Generalitat Valenciana (project PROMETEO/GV/0069). The authors thank Professor Christina Trautmann from GSI for support with the heavy ion irradiation experiments.Ali, M.; Ramirez Hoyos, P.; Nasir, S.; Nguyen, Q.; Ensinger, W.; Mafé, S. (2014). Nanoparticle-induced rectification in a single cylindrical nanopore: Net currents from zero time-average potentials. Applied Physics Letters. 104(4):437031-437034. https://doi.org/10.1063/1.4863511S4370314370341044Astumian, R. D., & Hänggi, P. (2002). Brownian Motors. Physics Today, 55(11), 33-39. doi:10.1063/1.1535005Magnasco, M. O. (1993). Forced thermal ratchets. Physical Review Letters, 71(10), 1477-1481. doi:10.1103/physrevlett.71.1477Hänggi, P., & Marchesoni, F. (2009). Artificial Brownian motors: Controlling transport on the nanoscale. Reviews of Modern Physics, 81(1), 387-442. doi:10.1103/revmodphys.81.387Ramirez, P., Gomez, V., Ali, M., Ensinger, W., & Mafe, S. (2013). Net currents obtained from zero-average potentials in single amphoteric nanopores. Electrochemistry Communications, 31, 137-140. doi:10.1016/j.elecom.2013.03.026Queralt-Martín, M., García-Giménez, E., Aguilella, V. M., Ramirez, P., Mafe, S., & Alcaraz, A. (2013). Electrical pumping of potassium ions against an external concentration gradient in a biological ion channel. Applied Physics Letters, 103(4), 043707. doi:10.1063/1.4816748Siwy, Z., & Fuliński, A. (2002). Fabrication of a Synthetic Nanopore Ion Pump. Physical Review Letters, 89(19). doi:10.1103/physrevlett.89.198103Vlassiouk, I., & Siwy, Z. S. (2007). Nanofluidic Diode. Nano Letters, 7(3), 552-556. doi:10.1021/nl062924bSiwy, Z. S. (2006). Ion-Current Rectification in Nanopores and Nanotubes with Broken Symmetry. Advanced Functional Materials, 16(6), 735-746. doi:10.1002/adfm.200500471Guan, W., Fan, R., & Reed, M. A. (2011). Field-effect reconfigurable nanofluidic ionic diodes. Nature Communications, 2(1). doi:10.1038/ncomms1514Ali, M., Ramirez, P., Mafé, S., Neumann, R., & Ensinger, W. (2009). A pH-Tunable Nanofluidic Diode with a Broad Range of Rectifying Properties. ACS Nano, 3(3), 603-608. doi:10.1021/nn900039fGuo, W., Cao, L., Xia, J., Nie, F.-Q., Ma, W., Xue, J., … Jiang, L. (2010). Energy Harvesting with Single-Ion-Selective Nanopores: A Concentration-Gradient-Driven Nanofluidic Power Source. Advanced Functional Materials, 20(8), 1339-1344. doi:10.1002/adfm.200902312Ramirez, P., Ali, M., Ensinger, W., & Mafe, S. (2012). Information processing with a single multifunctional nanofluidic diode. Applied Physics Letters, 101(13), 133108. doi:10.1063/1.4754845Yusko, E. C., An, R., & Mayer, M. (2009). Electroosmotic Flow Can Generate Ion Current Rectification in Nano- and Micropores. 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Rectification and signal averaging of weak electric fields by biological cells. Proceedings of the National Academy of Sciences, 92(9), 3740-3743. doi:10.1073/pnas.92.9.3740Manzanares, J. A., Cervera, J., & Mafé, S. (2011). Processing weak electrical signals with threshold-potential nanostructures showing a high variability. Applied Physics Letters, 99(15), 153703. doi:10.1063/1.3650712Blackiston, D. J., McLaughlin, K. A., & Levin, M. (2009). Bioelectric controls of cell proliferation: Ion channels, membrane voltage and the cell cycle. Cell Cycle, 8(21), 3527-3536. doi:10.4161/cc.8.21.9888Levin, M., & Stevenson, C. G. (2012). Regulation of Cell Behavior and Tissue Patterning by Bioelectrical Signals: Challenges and Opportunities for Biomedical Engineering. Annual Review of Biomedical Engineering, 14(1), 295-323. doi:10.1146/annurev-bioeng-071811-150114Davenport, M., Healy, K., Pevarnik, M., Teslich, N., Cabrini, S., Morrison, A. P., … Létant, S. E. (2012). The Role of Pore Geometry in Single Nanoparticle Detection. ACS Nano, 6(9), 8366-8380. doi:10.1021/nn303126nYu Apel, P., Blonskaya, I. V., Orelovitch, O. L., Sartowska, B. A., & Spohr, R. (2012). Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements. Nanotechnology, 23(22), 225503. doi:10.1088/0957-4484/23/22/225503Wanunu, M., Morrison, W., Rabin, Y., Grosberg, A. Y., & Meller, A. (2009). Electrostatic focusing of unlabelled DNA into nanoscale pores using a salt gradient. Nature Nanotechnology, 5(2), 160-165. doi:10.1038/nnano.2009.379Macrae, M. X., Blake, S., Mayer, M., & Yang, J. (2010). Nanoscale Ionic Diodes with Tunable and Switchable Rectifying Behavior. Journal of the American Chemical Society, 132(6), 1766-1767. doi:10.1021/ja909876hTagliazucchi, M., Rabin, Y., & Szleifer, I. (2013). Transport Rectification in Nanopores with Outer Membranes Modified with Surface Charges and Polyelectrolytes. 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Current rectification by nanoparticle blocking in single cylindrical nanopores

Blocking of a charged pore by an oppositely charged nanoparticle can support rectifying properties in a cylindrical nanopore, as opposed to the usual case of a fixed asymmetry in the pore geometry and charge distribution. We present here experimental data and model calculations to confirm this fundamental effect. The nanostructure imaging and the effects of nanoparticle concentration, pore radius, and salt concentration on the electrical conductance–voltage (G–V) curves are discussed. Logic responses based on chemical and electrical inputs/outputs could also be implemented with a single pore acting as an effective nanofluidic diode. To better show the generality of the results, different charge states and relative sizes of the nanopore and the nanoparticle are considered, emphasizing those physical concepts that are also found in the ionic drug blocking of protein ion channels.M. A., S. N., Q.-H. N., and W. E. acknowledge the Beilstein-Institut, Frankfurt/Main, Germany, within the research collaboration NanoBiC. P. R. and S. M. acknowledge the Ministry of Economy and Competitiveness (project MAT2012-32084), FEDER, and Generalitat Valenciana (project PROMETEO/GV/0069). The authors thank Prof. Dr Christina Trautmann from GSI for support with the heavy ion irradiation experiments and an anonymous referee for helpful suggestions.Ali, M.; Ramirez Hoyos, P.; Nasir, S.; Nguyen, Q.; Ensinger, W.; Mafé, S. (2014). Current rectification by nanoparticle blocking in single cylindrical nanopores. Nanoscale. 6(18):10740-10745. https://doi.org/10.1039/c4nr02968b1074010745618Vlassiouk, I., & Siwy, Z. S. (2007). Nanofluidic Diode. Nano Letters, 7(3), 552-556. doi:10.1021/nl062924bAli, M., Ramirez, P., Mafé, S., Neumann, R., & Ensinger, W. (2009). A pH-Tunable Nanofluidic Diode with a Broad Range of Rectifying Properties. ACS Nano, 3(3), 603-608. doi:10.1021/nn900039fCervera, J., Ramirez, P., Mafe, S., & Stroeve, P. (2011). Asymmetric nanopore rectification for ion pumping, electrical power generation, and information processing applications. Electrochimica Acta, 56(12), 4504-4511. doi:10.1016/j.electacta.2011.02.056Guo, W., Cao, L., Xia, J., Nie, F.-Q., Ma, W., Xue, J., … Jiang, L. (2010). Energy Harvesting with Single-Ion-Selective Nanopores: A Concentration-Gradient-Driven Nanofluidic Power Source. Advanced Functional Materials, 20(8), 1339-1344. doi:10.1002/adfm.200902312Nestorovich, E. M., Danelon, C., Winterhalter, M., & Bezrukov, S. M. (2002). Designed to penetrate: Time-resolved interaction of single antibiotic molecules with bacterial pores. Proceedings of the National Academy of Sciences, 99(15), 9789-9794. doi:10.1073/pnas.152206799Mafé, S., Ramı́rez, P., & Alcaraz, A. (2003). Simple molecular model for the binding of antibiotic molecules to bacterial ion channels. The Journal of Chemical Physics, 119(15), 8097-8102. doi:10.1063/1.1606438Karginov, V. A., Nestorovich, E. M., Moayeri, M., Leppla, S. H., & Bezrukov, S. M. (2005). Blocking anthrax lethal toxin at the protective antigen channel by using structure-inspired drug design. Proceedings of the National Academy of Sciences, 102(42), 15075-15080. doi:10.1073/pnas.0507488102Aguilella-Arzo, M., Cervera, J., Ramírez, P., & Mafé, S. (2006). Blocking of an ion channel by a highly charged drug: Modeling the effects of applied voltage, electrolyte concentration, and drug concentration. Physical Review E, 73(4). doi:10.1103/physreve.73.041914Yu Apel, P., Blonskaya, I. V., Orelovitch, O. L., Sartowska, B. A., & Spohr, R. (2012). Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements. Nanotechnology, 23(22), 225503. doi:10.1088/0957-4484/23/22/225503Ali, M., Ramirez, P., Nguyen, H. Q., Nasir, S., Cervera, J., Mafe, S., & Ensinger, W. 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Tetraalkylammonium Cations Conduction through a Single Nanofluidic Diode: Experimental and Theoretical Studies

[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 equilibriaM. A., S. N., and W. E. acknowledge the funding from the Hessen State Ministry of Higher Education, Research and the Arts, Germany, under the LOEWE project iNAPO. P. R., J. C., and S. M. acknowledge financial support by the Spanish Ministry of Economic Affairs and Competitiveness (MAT2015-65011-P) and FEDER. The authors are also thankful to Prof. C. Trautmann, Department of Materials Research from GSI, for support with irradiation experiments.Ali, M.; Ramirez Hoyos, P.; Nasir, S.; Cervera Montesinos, J.; Mafe, S.; Ensinger, W. (2017). Tetraalkylammonium Cations Conduction through a Single Nanofluidic Diode: Experimental and Theoretical Studies. ELECTROCHIMICA ACTA. 250:302-308. https://doi.org/10.1016/j.electacta.2017.08.078S30230825