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Robertson H, Gresham IJ, Nelson ARJ, Prescott SW, Webber GB, Wanless EJ. Illuminating the nanostructure of diffuse interfaces: Recent advances and future directions in reflectometry techniques. Adv Colloid Interface Sci 2024; 331:103238. [PMID: 38917595 DOI: 10.1016/j.cis.2024.103238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Revised: 06/07/2024] [Accepted: 06/13/2024] [Indexed: 06/27/2024]
Abstract
Diffuse soft matter interfaces take many forms, from end-tethered polymer brushes or adsorbed surfactants to self-assembled layers of lipids. These interfaces play crucial roles across a multitude of fields, including materials science, biophysics, and nanotechnology. Understanding the nanostructure and properties of these interfaces is fundamental for optimising their performance and designing novel functional materials. In recent years, reflectometry techniques, in particular neutron reflectometry, have emerged as powerful tools for elucidating the intricate nanostructure of soft matter interfaces with remarkable precision and depth. This review provides an overview of selected recent developments in reflectometry and their applications for illuminating the nanostructure of diffuse interfaces. We explore various principles and methods of neutron and X-ray reflectometry, as well as ellipsometry, and discuss advances in their experimental setups and data analysis approaches. Improvements to experimental neutron reflectometry methods have enabled greater time resolution in kinetic measurements and elucidation of diffuse structure under shear or confinement, while innovation in analysis protocols has significantly reduced data processing times, facilitated co-refinement of reflectometry data from multiple instruments and provided greater-than-ever confidence in proposed structural models. Furthermore, we highlight some significant research findings enabled by these techniques, revealing the organisation, dynamics, and interfacial phenomena at the nanoscale. We also discuss future directions and potential advancements in reflectometry techniques. By shedding light on the nanostructure of diffuse interfaces, reflectometry techniques enable the rational design and tailoring of interfaces with enhanced properties and functionalities.
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Affiliation(s)
- Hayden Robertson
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, NSW 2308, Australia; Soft Matter at Interfaces, Technical University of Darmstadt, Darmstadt D-64289, Germany
| | - Isaac J Gresham
- School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia
| | - Andrew R J Nelson
- Australian Centre for Neutron Scattering, ANSTO, Locked Bag 2001, Kirrawee DC, NSW 2232, Australia
| | - Stuart W Prescott
- School of Chemical Engineering, UNSW Sydney, Sydney, NSW 2052, Australia
| | - Grant B Webber
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Erica J Wanless
- College of Science, Engineering and Environment, University of Newcastle, Callaghan, NSW 2308, Australia.
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Pothukuchi RP, Radhakrishna M. Understanding the stimuli responsive behavior of polyion grafted nanoparticles in the presence of salt and polyelectrolytes. SOFT MATTER 2022; 18:6124-6137. [PMID: 35943182 DOI: 10.1039/d2sm00650b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
The design of nanoparticles (NPs) that respond to external stimuli like pH, temperature, and electric or magnetic fields has found immense interest in various fields of nanotechnology like nanomedicine, drug delivery, and cancer therapy. Nanoparticles grafted with polymeric ligands have been extensively used as building blocks in the directed self assembly of nanoparticles. These moieties not only assemble into various morphologies but also respond to a wide range of external stimuli. In this work, we have used coarse grained molecular dynamics simulations to understand the stimuli-responsive behavior of assemblies of NPs grafted with oppositely charged polyions (PGNs) in the presence of salt and polyelectrolytes. At low grafting density, a transformation from ring morphology to form dimers/strings/dispersed NPs was observed upon addition of divalent/trivalent salts. NPs grafted with longer grafts showed higher stability to remain as rings compared to shorter grafts. The change in NP morphology was a direct consequence of preferential interaction of the polyaion grafts with the oppositely charged salt ions compared to the oppositely charged grafts on the NPs. At fixed salt valency, the size of the salt ion, concentration and molecular connectivity played a crucial role in the stimuli responsive behavior of polyion grafted NPs in solutions. Further, in the presence of polyelectrolytes, these transitions occurred at lower monomer valency due to the stronger electrostatic interactions between the grafted chains and oppositely charged free polyelectrolytes in solutions. Disordered and ordered aggregates assemblies formed at higher grafting density were broken into smaller NP assemblies in the presence of salt. Drug encapsulation studies in the presence of salt and polyelectrolytes were performed on model drug moieties in order to demonstrate the potential use of the modelled stimuli responsive nanoparticle assemblies in drug delivery applications.
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Affiliation(s)
- Rajesh Pavan Pothukuchi
- Discipline of Chemical Engineering, Indian Institute of Technology (IIT), Gandhinagar, Palaj, Gujarat 382355, India.
| | - Mithun Radhakrishna
- Discipline of Chemical Engineering, Indian Institute of Technology (IIT), Gandhinagar, Palaj, Gujarat 382355, India.
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Szuwarzyński M, Wolski K, Kruk T, Zapotoczny S. Macromolecular strategies for transporting electrons and excitation energy in ordered polymer layers. Prog Polym Sci 2021. [DOI: 10.1016/j.progpolymsci.2021.101433] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Nakamura S, Mitomo H, Ijiro K. Assembly and Active Control of Nanoparticles using Polymer Brushes as a Scaffold. CHEM LETT 2021. [DOI: 10.1246/cl.200767] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Affiliation(s)
- Satoshi Nakamura
- National Institute of Advanced Industrial Science and Technology (AIST), 2266-98 Anagahora, Shimo-Shidami, Moriyama-ku, Nagoya, Aichi 463-8560, Japan
| | - Hideyuki Mitomo
- Research Institute for Electronic Science, Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Kita 21, Nishi 11, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
| | - Kuniharu Ijiro
- Research Institute for Electronic Science, Hokkaido University, Kita 21, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
- Global Station for Soft Matter, Global Institution for Collaborative Research and Education, Hokkaido University, Kita 21, Nishi 11, Kita-ku, Sapporo, Hokkaido 001-0021, Japan
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Wang L, Wei P, Stumpf S, Schubert US, Hoeppener S. pH-responsive SERS substrates based on AgNP-polyMETAC composites on patterned self-assembled monolayers. NANOTECHNOLOGY 2020; 31:465604. [PMID: 32841206 DOI: 10.1088/1361-6528/abab2d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Patterned silver nanoparticle (NP)-poly[2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (AgNP-polyMETAC) composites were prepared by electrochemical lithography, surface-initiated atom-transfer radical polymerization (SI-ATRP) and NP growth inside the polymer brushes. For this purpose, polymer brushes of poly[2-(methacryloyloxy)ethyl] trimethyl ammonium chloride (polyMETAC) were utilized as strong electrolyte brush system. These were introduced in form of patterned polymer brushes to create pH-responsive surface enhanced Raman scattering SERS substrates. It is well-known that the charges of strong polyelectrolyte chains are usually insensitive to pH changes, hence, rarely strong polyelectrolyte brushes have been utilized so far to study pH-responsive properties of such films. Here pH-insensitive polyMETAC brushes exhibit pH-sensitive properties and can be used as pH-responsive surfaces for SERS applications due to the embedding of AgNPs into the polymer brushes. When increasing the pH, the assembly of the AgNPs transfers from quasi two-dimensional (2D) aggregates, attaching mainly to the polymer surface, into a three-dimensional (3D) assembly, where the particles are penetrating into the brushes. These changes result in significant alterations of the SERS efficiency of the polymer brush composite. At pH 5, the enhancement of the Raman scattering approaches its maximum. The fabricated SERS substrates show a high sensitivity as well as good experimental reliability at different pH values. Moreover, electrochemical lithography was utilized to fabricate patterned SERS substrate, which allows an easy combination of multiple other functionalities in hierarchical structuring steps. In addition, the microstructure is in our studies beneficial because of a simplified and reliable characterization of the polymer brushes at defined sample areas. The introduction of the microstructured brush system is regarded moreover attractive for the development of high-throughput platforms for rapid, automated screening and analysis applications.
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Affiliation(s)
- Limin Wang
- Laboratory of Organic and Macromolecular Chemistry (IOMC), Friedrich Schiller University Jena, Humboldtstr. 10, 07743, Jena, Germany. Jena Center for Soft Matter (JCSM), Friedrich Schiller University Jena, Philosophenweg 7, 07743, Jena, Germany
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De Acha N, Elía V, Delgado-Camón A, Arregui FJ, Elosúa C. Straightforward nano patterning on optical fiber for sensors development. OPTICS LETTERS 2020; 45:3877-3880. [PMID: 32667308 DOI: 10.1364/ol.397817] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Accepted: 06/05/2020] [Indexed: 06/11/2023]
Abstract
A simple method to prepare a nano pattern along the surface of an optical fiber is applied in this Letter to develop a pH sensor. The template is made of a block copolymer that defines specific locations where gold nano particles are adsorbed on forming clusters. The average diameter of the resulting agglomerates is 121 nm, and the mean distance between the centers is 182 nm. The morphology of the gold cluster array produces localized surface plasmon resonance. The absorbance spectrum is affected by pH variations, and the ratio between the absorption at two different wavelengths is used to characterize the response, which is repetitive and reversible. This Letter highlights the potentiality of this type of chemical nano patterning for the development of optical fiber sensors.
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Ryzhkov NV, Andreeva DV, Skorb EV. Coupling pH-Regulated Multilayers with Inorganic Surfaces for Bionic Devices and Infochemistry. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8543-8556. [PMID: 31018639 DOI: 10.1021/acs.langmuir.9b00633] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
This article summarizes more than 10 years of cooperation with Prof. Helmuth Möhwald. Here we describe how the research moved from light-regulated feedback sustainable systems and control biodevices to the current focus on infochemistry in aqueous solution. An important advanced characteristic of such materials and devices is the pH concentration gradient in aqueous solution. A major part of the article focuses on the use of localized illumination for proton generation as a reliable, minimal-reagent-consuming, stable light-promoted proton pump. The in situ scanning vibration electrode technique (SVET) and scanning ion-selective electrode technique (SIET) are efficient for the spatiotemporal evolution of ions on the surface. pH-sensitive polyelectrolyte (PEs) multilayers with different PE architectures are composed with a feedback loop for bionic devices. We show here that pH-regulated PE multilayers can change their properties-film thickness and stiffness, permeability, hydrophilicity, and/or fluorescence-in response to light or electrochemical or biological processes instead of classical acid/base titration.
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Affiliation(s)
| | - Daria V Andreeva
- Centre for Advanced 2D Materials and Graphene Research Centre , National University of Singapore , 117546 Singapore
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Górka W, Kuciel T, Nalepa P, Lachowicz D, Zapotoczny S, Szuwarzyński M. Homogeneous Embedding of Magnetic Nanoparticles into Polymer Brushes during Simultaneous Surface-Initiated Polymerization. NANOMATERIALS (BASEL, SWITZERLAND) 2019; 9:E456. [PMID: 30893829 PMCID: PMC6474101 DOI: 10.3390/nano9030456] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Revised: 03/14/2019] [Accepted: 03/15/2019] [Indexed: 11/17/2022]
Abstract
Here we present a facile and efficient method of controlled embedding of inorganic nanoparticles into an ultra-thin (<15 nm) and flat (~1.0 nm) polymeric coating that prevents unwanted aggregation. Hybrid polymer brushes-based films were obtained by simultaneous incorporation of superparamagnetic iron oxide nanoparticles (SPIONs) with diameters of 8⁻10 nm into a polycationic macromolecular matrix during the surface initiated atom transfer radical polymerization (SI-ATRP) reaction in an ultrasonic reactor. The proposed structures characterized with homogeneous distribution of separated nanoparticles that maintain nanometric thickness and strong magnetic properties are a good alternative for commonly used layers of crosslinked nanoparticles aggregates or bulk structures. Obtained coatings were characterized using atomic force microscopy (AFM) working in the magnetic mode, secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (XPS).
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Affiliation(s)
- Weronika Górka
- Faculty of Physics, Jagiellonian University, Astronomy and Applied Computer Science, S. Łojasiewicza 11, 30-348 Krakow, Poland.
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland.
| | - Tomasz Kuciel
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland.
| | - Paula Nalepa
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland.
| | - Dorota Lachowicz
- Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, A. Mickiewicza 30, 30-059 Krakow, Poland.
| | - Szczepan Zapotoczny
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland.
| | - Michał Szuwarzyński
- Academic Centre for Materials and Nanotechnology, AGH University of Science and Technology, A. Mickiewicza 30, 30-059 Krakow, Poland.
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Rathee VS, Sidky H, Sikora BJ, Whitmer JK. Role of Associative Charging in the Entropy-Energy Balance of Polyelectrolyte Complexes. J Am Chem Soc 2018; 140:15319-15328. [PMID: 30351015 DOI: 10.1021/jacs.8b08649] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Polyelectrolytes may be classified into two primary categories (strong and weak) depending on how their charge state responds to the local environment. Both of these find use in many applications, including drug delivery, gene therapy, layer-by-layer films, and fabrication of ion filtration membranes. The mechanism of polyelectrolyte complexation is, however, still not completely understood, though experimental investigations suggest that entropy gain due to release of counterions is the key driving force for strong polyelectrolyte complexation. Here we perform a comprehensive thermodynamic investigation through coarse-grained molecular simulations permitting us to calculate the free energy of complex formation. Importantly, our expanded-ensemble methods permit the explicit separation of energetic and entropic contributions to the free energy. Our investigations indicate that entropic contributions indeed dominate the free energy of complex formation for strong polyelectrolytes, but are less important than energetic contributions when weak electrostatic coupling or weak polyelectrolytes are present. Our results provide a new view of the free energy of polyelectrolyte complex formation driven by polymer association, which should also arise in systems with large charge spacings or bulky counterions, both of which act to weaken ion-polymer binding.
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Affiliation(s)
- Vikramjit S Rathee
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , Indiana 46556 , United States
| | - Hythem Sidky
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , Indiana 46556 , United States
| | - Benjamin J Sikora
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , Indiana 46556 , United States
| | - Jonathan K Whitmer
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , Indiana 46556 , United States
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