1
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Ramirez P, Portillo S, Mafe S, Siwy ZS, Cervera J. Characterization of negative differential resistance in asymmetric nanopores obtained from two soluble electrolytes. J Chem Phys 2025; 162:194707. [PMID: 40377189 DOI: 10.1063/5.0255394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2024] [Accepted: 04/03/2025] [Indexed: 05/18/2025] Open
Abstract
Negative differential resistance (NDR) phenomena in nanofluidic diodes are characterized by a decrease in the electrical current with the increase in the transmembrane potential beyond a system-dependent threshold voltage. Here, we describe the NDR due to a nanoscale salt precipitation that occurs in a conical nanopore in contact with two highly soluble salts in the external solutions. The new experimental design permits tunable and reproducible NDR effects that can be characterized from the I-V curves for different pairs of soluble salts reacting at the pore tip to form the salt precipitate. The effects of pH and salt concentration on the precipitation, together with the use of electrolytes with different temperature-dependent solubilities, provide a complete description of the chemical NDR mechanism. In addition, the good reproducibility and stability observed over different voltage cycles suggest that the threshold potential needed for precipitation can be used for Ca2+ sensing in the range 1-1000 mM.
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Affiliation(s)
- Patricio Ramirez
- Departament de Física Aplicada, Universitat Politècnica de València, E-46022 Valencia, Spain
| | - Sergio Portillo
- Departament de Física de la Terra i Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
| | - Salvador Mafe
- Departament de Física de la Terra i Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
| | - Zuzanna S Siwy
- Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Javier Cervera
- Departament de Física de la Terra i Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
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2
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Smook LA, de Beer S. Molecular Design Strategies to Enhance the Electroresponse of Polyelectrolyte Brushes: Effects of Charge Fraction and Chain Length Dispersity. Macromolecules 2025; 58:1185-1195. [PMID: 39958485 PMCID: PMC11823628 DOI: 10.1021/acs.macromol.4c02579] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2024] [Revised: 12/13/2024] [Accepted: 01/17/2025] [Indexed: 02/18/2025]
Abstract
Polyelectrolyte brushes are functional surface coatings that react to external stimuli. The response of these brushes in electric fields is nearly immediate as the field acts directly on the charges in the polyion, while the response to bulk stimuli such as temperature, acidity, and ionic composition is intrinsically capped by transport limitations. However, the response of fully charged brushes is limited because large field strengths are required to achieve a response. This limits the application of these brushes to architectures such as small pores or nanojunctions because small biases can generate large field strengths over small distances. Here, we propose a design strategy that enhances the response and lowers the field strength required in these applications. Our coarse-grained simulations highlight two approaches to increase the electroresponse of polyelectrolyte brushes: dispersity in the chain length enhances the electroresponse and a reduction in the number of charged monomers does the same. With these approaches, we increase the relative brush height variation from only 28% to as much as 227% since in partially charged brushes, more chains need to respond to screen the imposed field and the longer chains in disperse brushes can reorganize over large distances. Additionally, we find that disperse brushes show a stratified response where short chains collapse first and long chains stretch first because this stratification minimizes the change in conformational energy. We envision that our insights will enable the application of electroresponsive polyelectrolyte brushes in larger architectures or in small architectures using smaller biases, which could enable a stimulus-responsive pore size modulation that could be used for filtration and molecular separations.
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Affiliation(s)
- Leon A. Smook
- Department of Molecules and
Materials, MESA+ Institute, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
| | - Sissi de Beer
- Department of Molecules and
Materials, MESA+ Institute, University of
Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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3
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Smook LA, de Beer S. Electrical Chain Rearrangement: What Happens When Polymers in Brushes Have a Charge Gradient? LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:4142-4151. [PMID: 38355408 PMCID: PMC10906002 DOI: 10.1021/acs.langmuir.3c03127] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 01/30/2024] [Accepted: 01/30/2024] [Indexed: 02/16/2024]
Abstract
Under the influence of electric fields, the chains in polyelectrolyte brushes can stretch and collapse, which changes the structure of the brush. Copolymer brushes with charged and uncharged monomers display a similar behavior. For pure polyelectrolyte and random copolymer brushes, the field-induced structure changes only the density of the brush and not its local composition, while the latter could be affected if charges are distributed inhomogeneously along the polymer backbone. Therefore, we systematically study the switching behavior of gradient polyelectrolyte brushes in electric fields for different solvent qualities, grafting densities, and charges per chain via coarse-grained molecular dynamics simulations. Similar to random copolymers and pure polyelectrolytes, these brushes show a mixed-phase transition: intermediate states between fully stretched and collapsed are characterized by a bimodal chain-end distribution. Additionally, we find that the total charge of the brush plays a key role in the critical field required for a complete transition. Finally, we find that gradient polyelectrolyte brushes are charge-enriched at the brush-solvent interface under stretched conditions and charge-depleted under collapsed conditions, allowing for control over the local composition and thus the surface charge of the brush due to the inhomogeneous charge along the grafted chains.
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Affiliation(s)
- Leon A. Smook
- Department of Molecules and Materials,
MESA+ Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands
| | - Sissi de Beer
- Department of Molecules and Materials,
MESA+ Institute for Nanotechnology, University
of Twente, P.O. Box 217, Enschede 7500 AE, The Netherlands
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4
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Balzer C, Wang ZG. Electroresponse of weak polyelectrolyte brushes. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:82. [PMID: 37707751 PMCID: PMC10501941 DOI: 10.1140/epje/s10189-023-00341-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/18/2023] [Accepted: 08/24/2023] [Indexed: 09/15/2023]
Abstract
End-tethered polyelectrolytes are widely used to modify substrate properties, particularly for lubrication or wetting. External stimuli, such as pH, salt concentration, or an electric field, can induce profound structural responses in weak polyelectrolyte brushes, which can be utilized to further tune substrate properties. We study the structure and electroresponsiveness of weak polyacid brushes using an inhomogeneous theory that incorporates both electrostatic and chain connectivity correlations at the Debye-Hückel level. Our calculation shows that a weak polyacid brush swells under the application of a negative applied potential, in agreement with recent experimental observation. We rationalize this behavior using a scaling argument that accounts for the effect of the surface charge. We also show that the swelling behavior has a direct influence on the differential capacitance, which can be modulated by the solvent quality, pH, and salt concentration.
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Affiliation(s)
- Christopher Balzer
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125, USA
| | - Zhen-Gang Wang
- Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E California Blvd, Pasadena, CA, 91125, USA.
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5
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Dai Y, Zhang Y, Ma Q, Lin M, Zhang X, Xia F. Inner Wall and Outer Surface Distinguished Solid-State Nanopores for Sensing. Anal Chem 2022; 94:17343-17348. [PMID: 36473027 DOI: 10.1021/acs.analchem.2c04216] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Solid-state nanopores, inspired by biological nanopores, have the advantages of good mechanical properties, stability, and easy modification. They have attracted wide attention in the fields of sequencing, sensing, molecular sieving, nanofluidic devices, nanoelectrochemistry, and energy conversion. Because of the ion/molecule transport characteristic of the pore, the research on solid-state nanopores mainly focuses on the functional modification of its inner wall. In recent years, the outer surface of nanopores has also attracted the attention of researchers, and the functional elements on the outer surface have the functions of anti-interference and ionic signal enhancement. In this perspective, we review research progress of inner wall and outer surface distinguished solid-state nanopores, highlight their processing and advantages, summarize their functions and applications in sensing, and give insight into further research.
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Affiliation(s)
- Yu Dai
- State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China
| | - Yiwei Zhang
- State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China
| | - Qun Ma
- State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China
| | - Meihua Lin
- State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China
| | - Xiaojin Zhang
- State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China
| | - Fan Xia
- State Key Laboratory of Biogeology and Environmental Geology, Engineering Research Center of Nano-Geomaterials of Ministry of Education, Faculty of Materials Science and Chemistry, China University of Geosciences, Wuhan 430074, P. R. China
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6
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Zaldivar G, Perez Sirkin YA, Debais G, Fiora M, Missoni LL, Gonzalez Solveyra E, Tagliazucchi M. Molecular Theory: A Tool for Predicting the Outcome of Self-Assembly of Polymers, Nanoparticles, Amphiphiles, and Other Soft Materials. ACS OMEGA 2022; 7:38109-38121. [PMID: 36340074 PMCID: PMC9631762 DOI: 10.1021/acsomega.2c04785] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Accepted: 10/05/2022] [Indexed: 06/16/2023]
Abstract
The supramolecular organization of soft materials, such as colloids, polymers, and amphiphiles, results from a subtle balance of weak intermolecular interactions and entropic forces. This competition can drive the self-organization of soft materials at the nano-/mesoscale. Modeling soft-matter self-assembly requires, therefore, considering a complex interplay of forces at the relevant length scales without sacrificing the molecular details that define the chemical identity of the system. This mini-review focuses on the application of a tool known as molecular theory to study self-assembly in different types of soft materials. This tool is based on extremizing an approximate free energy functional of the system, and, therefore, it provides a direct, computationally affordable estimation of the stability of different self-assembled morphologies. Moreover, the molecular theory explicitly incorporates structural details of the chemical species in the system, accounts for their conformational degrees of freedom, and explicitly includes their chemical equilibria. This mini-review introduces the general ideas behind the theoretical formalism and discusses its advantages and limitations compared with other theoretical tools commonly used to study self-assembled soft materials. Recent application examples are discussed: the self-patterning of polyelectrolyte brushes on planar and curved surfaces, the formation of nanoparticle (NP) superlattices, and the self-organization of amphiphiles into micelles of different shapes. Finally, prospective methodological improvements and extensions (also relevant for related theoretical tools) are analyzed.
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Affiliation(s)
- Gervasio Zaldivar
- Departamento
de Química Inorgánica Analítica y Química
Física, Ciudad Universitaria, Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Pabellón 2 C1428EGA, Buenos Aires, Argentina
- Instituto
de Química de los Materiales, Ambiente y Energía (INQUIMAE).
Ciudad Universitaria, CONICET, Universidad
de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Pabellón 2 C1428EGA, Buenos Aires, Argentina
| | - Yamila A. Perez Sirkin
- Departamento
de Química Inorgánica Analítica y Química
Física, Ciudad Universitaria, Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Pabellón 2 C1428EGA, Buenos Aires, Argentina
- Instituto
de Química de los Materiales, Ambiente y Energía (INQUIMAE).
Ciudad Universitaria, CONICET, Universidad
de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Pabellón 2 C1428EGA, Buenos Aires, Argentina
| | - Gabriel Debais
- Instituto
de Química de los Materiales, Ambiente y Energía (INQUIMAE).
Ciudad Universitaria, CONICET, Universidad
de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Pabellón 2 C1428EGA, Buenos Aires, Argentina
| | - Maria Fiora
- INTI-Micro
y Nanotecnologías, Instituto Nacional
de Tecnología Industrial (INTI), San Martín, Buenos Aires B1650WAB, Argentina
| | - Leandro L. Missoni
- Departamento
de Química Inorgánica Analítica y Química
Física, Ciudad Universitaria, Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Pabellón 2 C1428EGA, Buenos Aires, Argentina
- Instituto
de Química de los Materiales, Ambiente y Energía (INQUIMAE).
Ciudad Universitaria, CONICET, Universidad
de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Pabellón 2 C1428EGA, Buenos Aires, Argentina
| | - Estefania Gonzalez Solveyra
- Universidad
Nacional de San Martin, Instituto de Nanosistemas, UNSAM-CONICET, Av. 25 de Mayo 1021, 1650 San Martín, Buenos Aires, Argentina
| | - Mario Tagliazucchi
- Departamento
de Química Inorgánica Analítica y Química
Física, Ciudad Universitaria, Facultad de Ciencias Exactas
y Naturales, Universidad de Buenos Aires, Pabellón 2 C1428EGA, Buenos Aires, Argentina
- Instituto
de Química de los Materiales, Ambiente y Energía (INQUIMAE).
Ciudad Universitaria, CONICET, Universidad
de Buenos Aires, Facultad de Ciencias Exactas y Naturales, Pabellón 2 C1428EGA, Buenos Aires, Argentina
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7
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Chen X, Goh K. Quantifying the coupled monovalent and divalent ions sorption in dense ion exchange membranes. J Memb Sci 2022. [DOI: 10.1016/j.memsci.2022.121140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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8
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Qin S, Nap RJ, Huang K, Szleifer I. Influence of Membrane Permittivity on Charge Regulation of Weak Polyelectrolytes End-Tethered in Nanopores. Macromolecules 2022. [DOI: 10.1021/acs.macromol.2c01391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shiyi Qin
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
| | - Rikkert J. Nap
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
| | - Kai Huang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen 518107, China
| | - Igal Szleifer
- Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208, United States
- Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
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9
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Senechal V, Rodriguez-Hernandez J, Drummond C. Electroresponsive Weak Polyelectrolyte Brushes. Macromolecules 2022. [DOI: 10.1021/acs.macromol.1c02377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | - Carlos Drummond
- CNRS, CRPP, UMR 5031, Univ. Bordeaux, F-33600 Pessac, France
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10
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Qin S, Huang K, Szleifer I. Design of Multifunctional Nanopore Using Polyampholyte Brush with Composition Gradient. ACS NANO 2021; 15:17678-17688. [PMID: 34708653 DOI: 10.1021/acsnano.1c05543] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Molecular organizations and charge patterns inside biological nanopores are optimized by evolution to enhance ionic and molecular transport. Inspired by the nuclear pore complex that employs asymmetrically arranged disordered proteins for its gating, we here design an artificial nanopore coated by an asymmetric polyampholyte brush as a model system to study the asymmetric mass transport under nanoconfinement. A nonequilibrium steady-state molecular theory is developed to account for the intricate charge regulation effect of the weak polyampholyte and to address the coupling between the polymer conformation and the external electric field. On the basis of this state-of-the-art theoretical method, we present a comprehensive theoretical description of the stimuli-responsive structural behaviors and transport properties inside the nanopore with all molecular details considered. Our model demonstrates that by incorporating a gradient of pH sensitivity into the polymer coatings of the nanopore, a variety of asymmetric charge patterns and functional structures can be achieved, in a pH-responsive manner that allows for multiple functions to be implemented into the designed system. The asymmetric charge pattern inside the nanopore leads to an electrostatic trap for major current carriers, which turns the nanopore into an ionic rectifier with a rectification factor above 1000 at optimized pH and salt concentration. Our theory further predicts that the nanopore design behaves like a double-gated nanofluidic device with pH-triggered opening of the gates, which can serve as an ion pump and pH-responsive molecular filter. These results deepen our understanding of asymmetric transport in nanoconfined systems and provide guidelines for designing polymer-coated smart nanopores.
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Affiliation(s)
- Shiyi Qin
- Department of Biomedical Engineering, Department of Chemistry, and Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
| | - Kai Huang
- Institute of Systems and Physical Biology, Shenzhen Bay Laboratory, Shenzhen 518107, China
| | - Igal Szleifer
- Department of Biomedical Engineering, Department of Chemistry, and Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, United States
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11
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Perez-Grau JJ, Ramirez P, Garcia-Morales V, Cervera J, Nasir S, Ali M, Ensinger W, Mafe S. Fluoride-Induced Negative Differential Resistance in Nanopores: Experimental and Theoretical Characterization. ACS APPLIED MATERIALS & INTERFACES 2021; 13:54447-54455. [PMID: 34735108 PMCID: PMC9131425 DOI: 10.1021/acsami.1c18672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 10/25/2021] [Indexed: 06/13/2023]
Abstract
We describe experimentally and theoretically the fluoride-induced negative differential resistance (NDR) phenomena observed in conical nanopores operating in aqueous electrolyte solutions. The threshold voltage switching occurs around 1 V and leads to sharp current drops in the nA range with a peak-to-valley ratio close to 10. The experimental characterization of the NDR effect with single pore and multipore samples concern different pore radii, charge concentrations, scan rates, salt concentrations, solvents, and cations. The experimental fact that the effective radius of the pore tip zone is of the same order of magnitude as the Debye length for the low salt concentrations used here is suggestive of a mixed pore surface and bulk conduction regime. Thus, we propose a two-region conductance model where the mobile cations in the vicinity of the negative pore charges are responsible for the surface conductance, while the bulk solution conductance is assumed for the pore center region.
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Affiliation(s)
- Jose J. Perez-Grau
- Departament
de Física Aplicada, Universitat Politècnica
de València, E-46022 Valencia, Spain
| | - Patricio Ramirez
- Departament
de Física Aplicada, Universitat Politècnica
de València, E-46022 Valencia, Spain
| | - Vladimir Garcia-Morales
- Departament
de Física de la Terra i Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
| | - Javier Cervera
- Departament
de Física de la Terra i Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
| | - Saima Nasir
- Department
of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, Alarich-Weiss-Str. 02, D-64287 Darmstadt, Germany
- Materials
Research Department, GSI Helmholtzzentrum
für Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt, Germany
| | - Mubarak Ali
- Department
of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, Alarich-Weiss-Str. 02, D-64287 Darmstadt, Germany
- Materials
Research Department, GSI Helmholtzzentrum
für Schwerionenforschung, Planckstrasse 1, D-64291 Darmstadt, Germany
| | - Wolfgang Ensinger
- Department
of Material- and Geo-Sciences, Materials Analysis, Technische Universität Darmstadt, Alarich-Weiss-Str. 02, D-64287 Darmstadt, Germany
| | - Salvador Mafe
- Departament
de Física de la Terra i Termodinàmica, Universitat de València, E-46100 Burjassot, Spain
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12
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Reaction-diffusion model to quantify and visualize mass transfer and deactivation within core-shell polymeric microreactors. J Colloid Interface Sci 2021; 608:1999-2008. [PMID: 34749148 DOI: 10.1016/j.jcis.2021.10.092] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 10/15/2021] [Accepted: 10/16/2021] [Indexed: 12/13/2022]
Abstract
HYPOTHESIS The performance of a polymeric core-shell microreactor depends critically on (i) mass transfer, (ii) catalyzed chemical reaction, and (iii) deactivation within the nonuniform core-shell microstructure environment. As such, these three basic working principles control the active catalytic phase density in the reactor. THEORY We present a high-fidelity, image-based nonequilibrium computational model to quantify and visualize the mass transport as well as the deactivation process of a core-shell polymeric microreactor. In stark contrast with other published works, our microstructure-based computer simulation can provide a single-particle visualization with a micrometer spatial accuracy. FINDINGS We show how the interplay of kinetics and thermodynamics controls the product-induced deactivation process. The model predicts and visualizes the non-trivial, spatially resolved active catalyst phase patterns within a core-shell system. Moreover, we also show how the microstructure influences the formation of foulant within a core-shell structure; that is, begins from the core and grows radially onto the shell section. Our results suggest that the deactivation process is highly governed by the porosity/microstructure of the microreactor as well as the affinity of the products towards the solid phase of the reactor.
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13
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Sachar HS, Chava BS, Pial TH, Das S. All-Atom Molecular Dynamics Simulations of the Temperature Response of Densely Grafted Polyelectrolyte Brushes. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00922] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Harnoor Singh Sachar
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Bhargav Sai Chava
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Turash Haque Pial
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, College Park, Maryland 20742, United States
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14
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Perez Sirkin YA, Tagliazucchi M, Szleifer I. Nanopore gates via reversible crosslinking of polymer brushes: a theoretical study. SOFT MATTER 2021; 17:2791-2802. [PMID: 33544104 DOI: 10.1039/d0sm01760d] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Polymer-brush-modified nanopores are synthetic structures inspired by the gated transport exhibited by their biological counterparts. This work theoretically analyzes how the reversible crosslinking of a polymer network by soluble species can be used to control transport through nanochannels and pores. The study was performed with a molecular theory that allows inhomogeneities in the three spatial dimensions and explicitly takes into account the size, shape and conformations of all molecular species, considers the intermolecular interactions between the polymers and the soluble crosslinkers and includes the presence of a translocating particle inside the pore. It is shown than increasing the concentration of the soluble crosslinkers in bulk solution leads to a gradual increase of its number within the pore until a critical bulk concentration is reached. At the critical concentration, the number of crosslinkers inside the pore increases abruptly. For long chains, this sudden transition triggers the collapse of the polymer brush to the center of the nanopore. The resulting structure increases the free-energy barrier that a translocating particle has to surmount to go across the pore and modifies the route of translocation from the axis of the pore to its walls. On the other hand, for short polymer chains the crosslinkers trigger the collapse of the brush to the pore walls, which reduces the translocation barrier.
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Affiliation(s)
- Yamila A Perez Sirkin
- INQUIMAE-CONICET and DQIAQF, University of Buenos Aires, School of Sciences, Ciudad Universitaria, Pabellón 2, Ciudad Autónoma de Buenos Aires C1428EHA, Argentina.
| | - Mario Tagliazucchi
- INQUIMAE-CONICET and DQIAQF, University of Buenos Aires, School of Sciences, Ciudad Universitaria, Pabellón 2, Ciudad Autónoma de Buenos Aires C1428EHA, Argentina.
| | - Igal Szleifer
- Department of Biomedical Engineering, Department of Chemistry and Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208, USA.
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15
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Sachar HS, Pial TH, Chava BS, Das S. All-atom molecular dynamics simulations of weak polyionic brushes: influence of charge density on the properties of polyelectrolyte chains, brush-supported counterions, and water molecules. SOFT MATTER 2020; 16:7808-7822. [PMID: 32747883 DOI: 10.1039/d0sm01000f] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
All atom molecular dynamics (MD) simulations of planar Na+-counterion-neutralized polyacrylic acid (PAA) brushes are performed for varying degrees of ionization (and thereby varying charge density) and varying grafting density. Variation in the PE charge density (or degree of ionization) and grafting density leads to massive changes of the properties of the PE molecules (quantified by the changes in the height and the mobility of the PE brushes) as well as the local arrangement and distribution of the brush-supported counterions and water molecules within the brushes. The effect on the counterions is manifested by the corresponding variation of the counterion mobility, counterion concentration, extent of counterion binding to the charged site of the PE brushes, water-in-salt-like structure formation, and counterion-water-oxygen radial distribution function within the PE brushes. On the other hand, the effect on water molecules is manifested by the corresponding variation of water-oxygen-water-oxygen RDF, local water density, water-water and water-PE functional group hydrogen bond networks, static dielectric constant of water molecules, orientational tetrahedral order parameter, and water mobility. Enforcing such varying degree of ionization of weak polyelectrolytes is possible by changing the pH of the surrounding medium. Thus, our results provide insights into the changes in microstructure (at the atomistic level) of weak polyionic brushes at varying pH. We anticipate that this knowledge will prove to be vital for the efficient design of several nano-scale systems employing PE brushes such as nanomechanical gates, current rectifiers, etc.
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Affiliation(s)
- Harnoor Singh Sachar
- Department of Mechanical Engineering, University of Maryland, 4298 Campus Drive, College Park, MD 20742, USA.
| | - Turash Haque Pial
- Department of Mechanical Engineering, University of Maryland, 4298 Campus Drive, College Park, MD 20742, USA.
| | - Bhargav Sai Chava
- Department of Mechanical Engineering, University of Maryland, 4298 Campus Drive, College Park, MD 20742, USA.
| | - Siddhartha Das
- Department of Mechanical Engineering, University of Maryland, 4298 Campus Drive, College Park, MD 20742, USA.
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