Fröhlich, Kristina (2022)
Fabrication and Ion-Conducting Behavior of Heavy Ion Track-Etched Nanochannels under Aqueous and Non-Aqueous Conditions.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00021614
Dissertation, Erstveröffentlichung, Verlagsversion
Kurzbeschreibung (Abstract)
Inspired by biological ion channels embedded in cell membranes, which enable the selective transport of water, ions and organic molecules, synthetic ion channels fabricated in ion-tracked polymer membranes are attractive in a wide field of applications. Besides electrochemical sensing and stimuli-responsive devices, recently, molecular separation and purification processes as well as energy conversion systems gained much attention. All these applications necessitate a precise control over the channel dimensions and surface properties to meet the specific requirements. The fabrication process is proceeded by swift heavy ion irradiation of polymer films to generate latent tracks, which are converted into nanochannels using a suitable chemical etchant. A careful adjustment of the track-etching conditions allows producing channels with the desired diameter and geometry. In this thesis, new track-etching methods are developed to generate nanochannels in polyimide (PI), a polymer with excellent chemical and mechanical stability. The newly developed soft-etching technique allows a selective removal of damaged material from the latent track without affecting the bulk material, enabling the formation of sub-nanometer sized channels. These membranes exhibit an efficient and selective transport of small cationic species like alkali, NH4* and lithium-crown ether [Li(12C4)]+ ions, while the passage of divalent metal ions or bigger cationic analytes is hindered. Furthermore, the role of organic solvents in the chemical track-etching of PI membranes is investigated. Significantly higher etch rates can be achieved by using organic solvents, either as a pretreatment or as an additive during standard NaOCl etching. The ion permeation across the polymer membrane is performed in aqueous and aprotic organic electrolytes. The effect of surface charge density on the transport behavior of polymeric nanochannels in water is demonstrated using PAMAM dendrimers of various generations. The deposition of dendrimer molecules with positively charged amino groups on the channel walls induces an anion-selective ion transport, reaching the highest anion-flux for PAMAM of second generation. In organic electrolytes, the formation of solvated metal cations [M-(solvent)4]+ causes a dramatic reduction of the ion conductivity in soft-etched PI membranes, whereas track-etched PI membranes follow the same trend of the corresponding bulk solution conductivities. Track-etched polymer membranes show anion selectivity due to the deposition of [M-(solvent)4]+ in anhydrous propylene carbonate and acetonitrile, while similar anion and cation fluxes are measured in dimethylformamide. The presented results can be useful for membrane-based molecular filtration and purification processes in liquids and gases as well as in energy conversion nanofluidic devices operating in water and organic solvents.
Typ des Eintrags: | Dissertation | ||||
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Erschienen: | 2022 | ||||
Autor(en): | Fröhlich, Kristina | ||||
Art des Eintrags: | Erstveröffentlichung | ||||
Titel: | Fabrication and Ion-Conducting Behavior of Heavy Ion Track-Etched Nanochannels under Aqueous and Non-Aqueous Conditions | ||||
Sprache: | Englisch | ||||
Referenten: | Ensinger, Prof. Dr. Wolfgang ; Biesalski, Prof. Dr. Markus | ||||
Publikationsjahr: | 2022 | ||||
Ort: | Darmstadt | ||||
Kollation: | XVIII, 169 Seiten | ||||
Datum der mündlichen Prüfung: | 20 Juni 2022 | ||||
DOI: | 10.26083/tuprints-00021614 | ||||
URL / URN: | https://tuprints.ulb.tu-darmstadt.de/21614 | ||||
Kurzbeschreibung (Abstract): | Inspired by biological ion channels embedded in cell membranes, which enable the selective transport of water, ions and organic molecules, synthetic ion channels fabricated in ion-tracked polymer membranes are attractive in a wide field of applications. Besides electrochemical sensing and stimuli-responsive devices, recently, molecular separation and purification processes as well as energy conversion systems gained much attention. All these applications necessitate a precise control over the channel dimensions and surface properties to meet the specific requirements. The fabrication process is proceeded by swift heavy ion irradiation of polymer films to generate latent tracks, which are converted into nanochannels using a suitable chemical etchant. A careful adjustment of the track-etching conditions allows producing channels with the desired diameter and geometry. In this thesis, new track-etching methods are developed to generate nanochannels in polyimide (PI), a polymer with excellent chemical and mechanical stability. The newly developed soft-etching technique allows a selective removal of damaged material from the latent track without affecting the bulk material, enabling the formation of sub-nanometer sized channels. These membranes exhibit an efficient and selective transport of small cationic species like alkali, NH4* and lithium-crown ether [Li(12C4)]+ ions, while the passage of divalent metal ions or bigger cationic analytes is hindered. Furthermore, the role of organic solvents in the chemical track-etching of PI membranes is investigated. Significantly higher etch rates can be achieved by using organic solvents, either as a pretreatment or as an additive during standard NaOCl etching. The ion permeation across the polymer membrane is performed in aqueous and aprotic organic electrolytes. The effect of surface charge density on the transport behavior of polymeric nanochannels in water is demonstrated using PAMAM dendrimers of various generations. The deposition of dendrimer molecules with positively charged amino groups on the channel walls induces an anion-selective ion transport, reaching the highest anion-flux for PAMAM of second generation. In organic electrolytes, the formation of solvated metal cations [M-(solvent)4]+ causes a dramatic reduction of the ion conductivity in soft-etched PI membranes, whereas track-etched PI membranes follow the same trend of the corresponding bulk solution conductivities. Track-etched polymer membranes show anion selectivity due to the deposition of [M-(solvent)4]+ in anhydrous propylene carbonate and acetonitrile, while similar anion and cation fluxes are measured in dimethylformamide. The presented results can be useful for membrane-based molecular filtration and purification processes in liquids and gases as well as in energy conversion nanofluidic devices operating in water and organic solvents. |
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Status: | Verlagsversion | ||||
URN: | urn:nbn:de:tuda-tuprints-216142 | ||||
Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften | ||||
Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Materialanalytik |
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Hinterlegungsdatum: | 13 Jul 2022 12:10 | ||||
Letzte Änderung: | 14 Jul 2022 05:23 | ||||
PPN: | |||||
Referenten: | Ensinger, Prof. Dr. Wolfgang ; Biesalski, Prof. Dr. Markus | ||||
Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 20 Juni 2022 | ||||
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