The society profits from a variety of electronic devices, which rely on electrons and holes as the charge carriers for information transmission and processing. In contrast, biological systems operate via ions of varying size to handle complicated tasks, including massive parallel information sensing, processing, storing, and behavior controlling in nature, which inspire the development of iontronics (such as ionic transistors, ionic diodes, and ionic resistive memristors) for further bioelectronic interface, in-memory computing, and artificial intelligence hardware.[1]
In recent years, the electric double layer (EDL) formation has proven a powerful tool for the coupling of ions and electrons in iontronics. EDL electrically adsorbs/desorbs ions on the surface of electrodes to balance and store opposite charges in a controllable manner, which enables to operate ions and build iontronic devices. Nanoporous carbons with higher specific surface areas compared to widely-used metal electrodes in iontronics feature the higher volume and specific capacitances along with fine compatibility with biological systems, which are promising for ion manipulation in iontronics.[2,3] In recent years, a series of carbon-based capacitive iontronics were developed to realize the functions of conventional diodes and transistors.[4,5] Due to the demand of high performance (energy and power density) in above devices, toxic electrolytes were applied as the electrolytes,[4,5] which limits the implementation in biological applications.
Various functionally bioactive ions are a requisite for complicated psychological, physiological, and behavioral processes, such as neurotransmitters (ranging from amino acids (e.g., glycine (Gly) and gamma-aminobutyric acid (GABA)), biogenic amines (e.g., dopamine and acetylcholine), to peptides (e.g., vasopressin and somatostatin)).[6] Moreover, some bioactive ions such as sodium ibuprofen (NaIbu) and sodium salicylate (NaSal) are common analgesic and inflammation drugs for the human health.[7,8] So far, there have been few reports about applying bioactive ions as the charge carriers in carbon-based EDL iontronics. A deep molecular-level mechanism of the adsorption of bioactive ions and the deliberate concentration control via nanoporous carbons with and without polarization remain unclear and unsolved, but are crucial for the design of neuromorphic devices, neurotransmitter sensors, and transmitter delivery.
Given the varying sizes and structures of bioactive ions and the varying porosity structures of nanoporous carbons, there are some open questions for the interaction mechanism of bioactive ions and nanoporous carbons in the EDL devices as shown in the following: a) the influence of porosity structures of nanoporous carbons for the adsorption kinetics and thermodynamics of bioactive ions; b) the difference of the electrosorption and physisorption and their roles for manipulating ion behaviors; c) the influence of bioactive ion structure for the adsorption process; d) the adsorption mechanisms for electroneutral and charged neurotransmitters; e) the effects of the surface polarity and functional groups of nanoporous carbons for the bioactive ion adsorption process. This thesis focuses on revealing the interaction behaviors of bioactive ion electrolytes and nanoporous carbon electrodes from four main parts, with the aid of electrochemical methods and spectroscopic analyses.
In Chapter 5.1, the adsorption kinetics of bioactive choline chloride (ChCl) in ACC with a narrow pore size distribution (PSD) and ROX with a broad PSD is explored. The comparison indicates a faster diffusion process of ChCl in ROX with a broad PSD. The evaluation of physisorption and electrosorption of ChCl in ROX with a broad PSD is conducted, which show that the amount of physically adsorbed ChCl in ROX is less than 6 μmol/g, while the amount of electrosorption-induced concentration changes in the polarized ROX electrode is up to 30 μmol/g. Electrosorption dominates the adsorption process for ChCl. Consequently, it can be concluded that the capture and release of ChCl in aqueous solutions can be easily manipulated via electrochemical techniques.
Chapter 5.2 builds on the investigation of the ChCl interaction behavior in the ROX carbon. The investigation is extended to a series of ammonium-based ionic liquid salts with different alkyl chain lengths paired with Cl- anions (CxAmOMCl, where x=2, 6, and 12). The increasing physisorption of these cations in the ROX carbon is observed with the alkyl chain length increasing. The role of alkyl chain is clarified in bioactive cations for the adsorption in nanoporous carbons. However, the bioactive anions with long alkyl chains showed a quite weaker adsorption in the ROX carbon, compared with bioactive cations with long alkyl chains. These results illustrate the synergistic effect of the hydrophobic interaction and electrostatic attraction for the bioactive ions strong adsorption in nanoporous carbons.
In Chapter 5.3, the adsorption and charge balancing mechanism of electroneutral amino acids are further explored in ROX carbon electrodes. The weak physisorption of four amino acids (with linear structures) is observed, which results from the hydrophilic end groups and electroneutral properties. The charge balance mechanism of these electroneutral zwitterions (with amine and carboxylic acid groups) is clarified as the dissociation reaction of amino acid zwitterions, which produces anions to balance positive charges and cations to balance negative charges. In the buffered environment, the deliberate uptake and release of inhibitory neurotransmitters (Gly and GABA) are achieved by polarizing porous carbon electrodes, which implies the powerful abilities of electrosorption for controlling the concentration of neurotransmitters in aqueous and phosphate-buffered saline (PBS) solutions.
In Chapter 5.4, we investigate the impurity effects for the carbon properties and bioactive ion adsorption processes. The impurity contents are very high in some commercial porous carbons. The washing process leads to the decrease of O and N contents, and reduces wettability of porous carbons. Moreover, some O, N, and other non-carbon contents, which are commonly considered as surface functional groups of carbons, are not bonded but adsorbed inorganic impurities on the carbon surface. In-situ UV-Vis experiments clarify that the adsorbed ionic impurities play a role in the charge balance process during the electric polarization, which partly explains the capacitances of porous carbons in pure water electrolytes.
The questions addressed in this thesis provide a fundamental basis for the understanding of the interaction of various bioactive ions with nanoporous carbons, which benefit the development of EDL iontronics. Based on two different interaction modes (weak and strong adsorption), the interaction theory is further applied in the construction of iontronic devices. For weak adsorption, EDL transistors are deeply explored using bioactive ions (ChCl, NaIbu, Gly, and GABA). The capacitance switching behavior is confirmed in a 3D printed carbon-based ionic transistor. The concentration manipulation of bioactive ions in aqueous environments are promising for various potential applications, such as toxic ion removal, drug delivery, plant regulation, and bioelectronic devices. For strong adsorption, the confined cations with long alkyl chains (cations of C12AmOMCl) are irreversibly adsorbed and fixed on the porous carbon surface. The electric polarization cannot desorb confined cations, causing anion depletion and anion enrichment during electric polarization, which leads to the favorable memristive behavior for promising ionic memristors and in-memory computing applications in the future.
References
[1] C. Wan, K. Xiao, A. Angelin, M. Antonietti, X. Chen, Advanced Intelligent Systems 2019, 1, 1900073.
[2] S. Z. Bisri, S. Shimizu, M. Nakano, Y. Iwasa, Advanced Materials 2017, 29, 1607054.
[3] Y.-Z. Zhang, Y. Wang, T. Cheng, L.-Q. Yao, X. Li, W.-Y. Lai, W. Huang, Chemical Society Reviews 2019, 48, 3229.
[4] S. Lochmann, Y. Bräuniger, V. Gottsmann, L. Galle, J. Grothe, S. Kaskel, Advanced Functional Materials 2020, 30, 1910439.
[5] E. Zhang, N. Fulik, G.-P. Hao, H.-Y. Zhang, K. Kaneko, L. Borchardt, E. Brunner, S. Kaskel, Angewandte Chemie International Edition 2019, 58, 13060.
[6] S. E. Hyman, Current Biology 2005, 15, R154.
[7] S. A. Hawley, M. D. Fullerton, F. A. Ross, J. D. Schertzer, C. Chevtzoff, K. J. Walker, M. W. Peggie, D. Zibrova, K. A. Green, K. J. Mustard, B. E. Kemp, K. Sakamoto, G. R. Steinberg, D. G. Hardie, Science 2012, 336, 918.
[8] N. Azum, A. Ahmed, M. A. Rub, A. M. Asiri, S. F. Alamery, Journal of Molecular Liquids 2019, 290, 111187.:Table of Contents I
Abbreviations IV
1. Motivation 1
2. Background and Introduction 5
2.1. Biology and Ion-controlled Devices 5
2.2. Ion-related Biological Processes 5
2.2.1. Sensing and Signaling 5
2.2.2. Memory and Computing 7
2.2.3. Actuation Components 9
2.3. Bioinspired Iontronics 10
2.3.1. Ionic Diodes 11
2.3.2. Ionic Transistors 12
2.3.3. Ionic Resistive Memristors 14
2.4. Carbon-based Capacitive Iontronics 15
2.4.1. The Mechanism of Carbon-based Supercapacitors 15
2.4.2. Electrolytes for Supercapacitors 18
2.4.3. Nanoporous Carbons 22
2.4.4. Carbon-based Ionic Diodes 23
2.4.5. Carbon-based Ionic Transistors 24
2.4.6. The Interaction Mechanism of Bioactive Ions with Porous Carbons 26
3. Electrochemical Methods 28
3.1. Linear Sweep Voltammetry (LSV) 28
3.2. Cyclic Voltammetry (CV) 30
3.3. Electrochemical Impedance Spectroscopy (EIS) 31
4. Experimental Section 35
4.1. List of Used Chemicals 35
4.2. List of Used Materials 36
4.3. Preparation and Characterizations 37
4.3.1. Carbon Preparation 37
4.3.2. Electrode Preparation 38
4.3.3. 2-electrode Cells 38
4.3.4. 3-electrode Cells 38
4.3.5. 4-terminal Setups 39
4.3.6. Local pH Measurement 39
4.3.7. EIS Measurement 40
4.3.8. In-situ UV-Vis Measurement 40
4.3.9. Raman Spectroscopy 41
4.3.10. NMR and MS Measurement 41
4.3.11. Ninhydrin Reaction 42
4.3.12. Nitrogen Physisorption 42
4.3.13. Electrosorption Evaluation 42
5. Results and Discussion 43
5.1. Pore Structure and Ion Adsorption Kinetics 43
5.1.1. Introduction 43
5.1.2. Physiochemical Properties of Two Nanoporous Carbons 43
5.1.3. ChCl Physisorption Mechanism in Nanoporous Carbons 45
5.1.4. ChCl Electrochemical Stability and Performance 48
5.1.5. ChCl Electrosorption Mechanism in Nanoporous Carbons 52
5.1.6. Switchable Capacitive Transistor Analogues in Printed Structures 60
5.1.7. Summary 63
5.2. Ion Structures and Adsorption Kinetics 64
5.2.1. Introduction 64
5.2.2. Synthesis and Characterization of Ammonium-based ILs 65
5.2.3. Adsorption Behavior of Ammonium-based ILs in Nanoporous Carbons 67
5.2.4. Electrochemical Performance of Ammonium-based ILs 76
5.2.5. Adsorption Behavior of Organic Salts in Nanoporous Carbons 78
5.2.6. Strong Interaction and Ionic Memristor Behaviors 82
5.2.7. Weak Interaction and Ionic Transistor Applications 86
5.2.8. Summary 89
5.3. Electroneutral Neurotransmitter Adsorption Mechanism 90
5.3.1. Introduction 90
5.3.2. Amino Acid Physisorption Mechanism in Nanoporous Carbons 92
5.3.3. Amino Acid Electrochemical Behaviors in Electrically-polarized Nanoporous Carbons 96
5.3.4. Mechanism Investigation of Zwitterions in Electrically-polarized Nanoporous Carbons 99
5.3.5. Local pH Measurement of Amino Acid Electrolytes during Electric Polarization 105
5.3.6. Electrosorption-induced Capture and Release of Amino Acid Neurotransmitters 109
5.3.7 Neurotransmitter-based Bioinspired Iontronic Devices 113
5.3.8. Summary 115
5.4. Porous Carbon Impurities for Bioactive Ion Adsorption 116
5.4.1. Introduction 116
5.4.2. Qualitative Analysis of the Impurity Release from Porous Carbons 118
5.4.3. Electrochemical Evaluation for Ionic Impurities in Porous Carbons 121
5.4.4. The Effect of Adsorbed Ionic Impurities for Carbon Properties 126
5.4.5. The Charge Balance Mechanism of Ionic Impurities for Bioactive Ion Controlling 135
5.4.6. Summary 137
6. Conclusion and Outlook 139
7. References 142
A. Bibliography 152
B. List of Publications 154
C. Acknowledgements 155
D. Appendix 157
E. Versicherung und Erklärung 161
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa:de:qucosa:93821 |
| Date | 20 September 2024 |
| Creators | Li, Panlong |
| Contributors | Kaskel, Stefan, Balducci, Andrea, Technische Universität Dresden |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/publishedVersion, doc-type:doctoralThesis, info:eu-repo/semantics/doctoralThesis, doc-type:Text |
| Rights | info:eu-repo/semantics/openAccess |
| Relation | 10.1002/anie.202212250, 10.1002/anie.202412674, 10.1002/admt.202400439, 10.1016/j.cej.2023.146898, info:eu-repo/grantAgreement/European Research Council/European Union’s Horizon 2020 Research and Innovation Programme/101054940/ |
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