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Murphy E, Zhang C, Bates CM, Hawker CJ. Chromatographic Separation: A Versatile Strategy to Prepare Discrete and Well-Defined Polymer Libraries. Acc Chem Res 2024; 57:1202-1213. [PMID: 38530881 PMCID: PMC11025024 DOI: 10.1021/acs.accounts.4c00059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Revised: 03/06/2024] [Accepted: 03/08/2024] [Indexed: 03/28/2024]
Abstract
ConspectusThe preparation of discrete and well-defined polymers is an emerging strategy for emulating the remarkable precision achieved by macromolecular synthesis in nature. Although modern controlled polymerization techniques have unlocked access to a cornucopia of materials spanning a broad range of monomers, molecular weights, and architectures, the word "controlled" is not to be confused with "perfect". Indeed, even the highest-fidelity polymerization techniques─yielding molar mass dispersities in the vicinity of Đ = 1.05─unavoidably create a considerable degree of structural and/or compositional dispersity due to the statistical nature of chain growth. Such dispersity impacts many of the properties that researchers seek to control in the design of soft materials.The development of strategies to minimize or entirely eliminate dispersity and access molecularly precise polymers therefore remains a key contemporary challenge. While significant advances have been made in the realm of iterative synthetic methods that construct oligomers with an exact molecular weight, head-to-tail connectivity, and even stereochemistry via small-molecule organic chemistry, as the word "iterative" suggests, these techniques involve manually propagating monomers one reaction at a time, often with intervening protection and deprotection steps. As a result, these strategies are time-consuming, difficult to scale, and remain limited to lower molecular weights. The focus of this Account is on an alternative strategy that is more accessible to the general scientific community because of its simplicity, versatility, and affordability: chromatography. Researchers unfamiliar with the intricacies of synthesis may recall being exposed to chromatography in an undergraduate chemistry lab. This operationally simple, yet remarkably powerful, technique is most commonly encountered in the purification of small molecules through their selective (differential) adsorption to a column packed with a low-cost stationary phase, usually silica. Because the requisite equipment is readily available and the actual separation takes little time (on the order of 1 h), chromatography is used extensively in small-molecule chemistry throughout industry and academia alike. It is, therefore, perhaps surprising that similar types of chromatography are not more widely leveraged in the field of polymer science as well.Here, we discuss recent advances in using chromatography to control the structure and properties of polymeric materials. Emphasis is placed on the utility of an adsorption-based mechanism that separates polymers based on polarity and composition at tractable (gram) scales for materials science, in contrast to size exclusion, which is extremely common but typically analyzes very small quantities of a sample (∼1 mg) and is limited to separating by molar mass. Key concepts that are highlighted include (1) the separation of low-molecular-weight homopolymers into discrete oligomers (Đ = 1.0) with precise chain lengths and (2) the efficient fractionation of block copolymers into high-quality and widely varied libraries for accelerating materials discovery. In summary, the authors hope to convey the exciting possibilities in polymer science afforded by chromatography as a scalable, versatile, and even automated technique that unlocks new avenues of exploration into well-defined materials for a diverse assortment of researchers with different training and expertise.
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Affiliation(s)
- Elizabeth
A. Murphy
- Materials
Research Laboratory, Department of Chemistry & Biochemistry, Department of Chemical
Engineering, andMaterials Department, University of California
Santa Barbara, Santa
Barbara, California 93106, United States
| | - Cheng Zhang
- Materials
Research Laboratory, Department of Chemistry & Biochemistry, Department of Chemical
Engineering, andMaterials Department, University of California
Santa Barbara, Santa
Barbara, California 93106, United States
- Australian
Institute for Bioengineering and Nanotechnology and Centre for Advanced
Imaging University of Queensland, Brisbane, Queensland 4072, Australia
| | - Christopher M. Bates
- Materials
Research Laboratory, Department of Chemistry & Biochemistry, Department of Chemical
Engineering, andMaterials Department, University of California
Santa Barbara, Santa
Barbara, California 93106, United States
| | - Craig J. Hawker
- Materials
Research Laboratory, Department of Chemistry & Biochemistry, Department of Chemical
Engineering, andMaterials Department, University of California
Santa Barbara, Santa
Barbara, California 93106, United States
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2
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Jara Fornerod M, Alvarez-Fernandez A, Michalska M, Papakonstantinou I, Guldin S. Glucose Oxidase Loading in Ordered Porous Aluminosilicates: Exploring the Potential of Surface Modification for Electrochemical Glucose Sensing. CHEMISTRY OF MATERIALS : A PUBLICATION OF THE AMERICAN CHEMICAL SOCIETY 2023; 35:7577-7587. [PMID: 37780408 PMCID: PMC10536975 DOI: 10.1021/acs.chemmater.3c01202] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Revised: 08/22/2023] [Indexed: 10/03/2023]
Abstract
Enzymatic electrochemical sensors have become the leading glucose detection technology due to their rapid response, affordability, portability, selectivity, and sensitivity. However, the performance of these sensors is highly dependent on the surface properties of the electrode material used to store glucose oxidase and its ability to retain enzymatic activity under variable environmental conditions. Mesoporous thin films have recently attracted considerable attention as promising candidates for enzyme storage and activity preservation due to their well-defined nanoarchitecture and tunable surface properties. Herein, we systematically compare pathways for the immobilization of glucose oxidase (GOx) and their effectiveness in electrochemical glucose sensing, following modification protocols that lead to the electrostatic attraction (amino functionalization), covalent bonding (aldehyde functionalization), and electrostatic repulsion (oxygen plasma treatment) of the ordered porous aluminosilicate-coated electrodes. By direct comparison using a quartz crystal microbalance, we demonstrate that glucose oxidase can be loaded in a nanoarchitecture with a pore size of ∼50 nm and pore interconnections of ∼35 nm using the native aluminosilicate surface, as well as after amino or aldehyde surface modification, while oxygen plasma exposure of the native surface inhibits glucose oxidase loading. Despite a variety of routes for enzyme loading, quantitative electrochemical glucose sensing between 0 and 20 mM was only possible when the porous surface was functionalized with amino groups, which we relate to the role of surface chemistry in accessing the underlying substrate. Our results highlight the impact of rational surface modification on electrochemical biosensing performance and demonstrate the potential of tailoring porous nanoarchitecture surfaces for biosensing applications.
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Affiliation(s)
| | - Alberto Alvarez-Fernandez
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Martyna Michalska
- Department
of Electronic & Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.
| | - Ioannis Papakonstantinou
- Department
of Electronic & Electrical Engineering, University College London, Torrington Place, London WC1E 7JE, U.K.
| | - Stefan Guldin
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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3
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Jara Fornerod M, Alvarez-Fernandez A, Williams ER, Skoda MWA, Prieto-Simon B, Voelcker NH, Stefik M, Coppens MO, Guldin S. Enhanced Structural Control of Soft-Templated Mesoporous Inorganic Thin Films by Inert Processing Conditions. ACS APPLIED MATERIALS & INTERFACES 2022; 14:56143-56155. [PMID: 36503231 PMCID: PMC9782354 DOI: 10.1021/acsami.2c18090] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2022] [Accepted: 11/28/2022] [Indexed: 06/17/2023]
Abstract
Mesoporous thin films are widely used for applications in need of high surface area and efficient mass and charge transport properties. A well-established fabrication process involves the supramolecular assembly of organic molecules (e.g., block copolymers and surfactants) with inorganic materials obtained by sol-gel chemistry. Typically, subsequent calcination in air removes the organic template and reveals the porous inorganic network. A significant challenge for such coatings is the anisotropic shrinkage due to the volume contraction related to solvent evaporation, inorganic condensation, and template removal, affecting the final porosity as well as pore shape, size, arrangement, and accessibility. Here, we show that a two-step calcination process, composed of high-temperature treatment in argon followed by air calcination, is an effective fabrication strategy to reduce film contraction and enhance structural control of mesoporous thin films. Crucially, the formation of a transient carbonaceous scaffold enables the inorganic matrix to fully condense before template removal. The resulting mesoporous films retain a higher porosity as well as bigger pores with extended porous order. Such films present favorable characteristics for mass transport of large molecules. This is demonstrated for lysozyme adsorption into the mesoporous thin films as an example of enzyme storage.
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Affiliation(s)
| | - Alberto Alvarez-Fernandez
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Eric R. Williams
- Department
of Chemistry and Biochemistry, University
of South Carolina, Columbia, South Carolina 29208, United States
| | - Maximilian W. A. Skoda
- ISIS
Pulsed Neutron and Muon Source, Rutherford
Appleton Laboratory, Harwell, Oxfordshire OX11 OQX, U.K.
| | - Beatriz Prieto-Simon
- Department
of Electronic Engineering, Universitat Rovira
i Virgili, 43007 Tarragona, Spain
- ICREA, Pg. Lluís Companys 23, 08010 Barcelona, Spain
| | - Nicolas H. Voelcker
- Monash Institute
of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia
- Melbourne
Centre for Nanofabrication, Victorian Node
of the Australian National Fabrication Facility, Clayton, Victoria 3168, Australia
| | - Morgan Stefik
- Department
of Chemistry and Biochemistry, University
of South Carolina, Columbia, South Carolina 29208, United States
| | - Marc-Olivier Coppens
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
- Centre
for Nature Inspired Engineering, University
College London, Torrington
Place, London WC1E 7JE, U.K.
| | - Stefan Guldin
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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4
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Suthar J, Alvarez-Fernandez A, Taylor A, Fornerod MJ, Williams GR, Guldin S. Silica Inverse Opal Nanostructured Sensors for Enhanced Immunodetection of Extracellular Vesicles by Quartz Crystal Microbalance with Dissipation Monitoring. ACS APPLIED NANO MATERIALS 2022; 5:12951-12961. [PMID: 36185167 PMCID: PMC9513796 DOI: 10.1021/acsanm.2c02775] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 08/05/2022] [Indexed: 05/02/2023]
Abstract
Extracellular vesicles (EVs) are nanosized circulating assemblies that contain biomarkers considered promising for early diagnosis within neurology, cardiology, and oncology. Recently, acoustic wave biosensors, in particular based on quartz crystal microbalance with dissipation monitoring (QCM-D), have emerged as a sensitive, label-free, and selective EV characterization platform. A rational approach to further improving sensing detection limits relies on the nanostructuration of the sensor surfaces. To this end, inorganic inverse opals (IOs) derived from colloidal self-assembly present a highly tunable and scalable nanoarchitecture of suitable feature sizes and surface chemistry. This work systematically investigates their use in two-dimensional (2D) and three-dimensional (3D) for enhanced QCM-D EV detection. Precise tuning of the architecture parameters delivered improvements in detection performance to sensitivities as low as 6.24 × 107 particles/mL. Our findings emphasize that attempts to enhance acoustic immunosensing via increasing the surface area by 3D nanostructuration need to be carefully analyzed in order to exclude solvent and artifact entrapment effects. Moreover, the use of 2D nanostructured electrodes to compartmentalize analyte anchoring presents a particularly promising design principle.
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Affiliation(s)
- Jugal Suthar
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
- UCL
School of Pharmacy, University College London,
Bloomsbury, 29-39 Brunswick
Square, London WC1N 1AX, U.K.
| | - Alberto Alvarez-Fernandez
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Alaric Taylor
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Maximiliano J. Fornerod
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
| | - Gareth R. Williams
- UCL
School of Pharmacy, University College London,
Bloomsbury, 29-39 Brunswick
Square, London WC1N 1AX, U.K.
| | - Stefan Guldin
- Department
of Chemical Engineering, University College
London, Torrington Place, London WC1E 7JE, U.K.
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5
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Augurio A, Alvarez-Fernandez A, Panchal V, Pittenger B, De Wolf P, Guldin S, Briscoe J. Controlled Porosity in Ferroelectric BaTiO 3 Photoanodes. ACS APPLIED MATERIALS & INTERFACES 2022; 14:13147-13157. [PMID: 35271773 PMCID: PMC8949718 DOI: 10.1021/acsami.1c17419] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 01/14/2022] [Indexed: 05/17/2023]
Abstract
The use of ferroelectric polarization to promote electron-hole separation has emerged as a promising strategy to improve photocatalytic activity. Although ferroelectric thin films with planar geometry have been largely studied, nanostructured and porous ferroelectric thin films have not been commonly used in photo-electrocatalysis. The inclusion of porosity in ferroelectric thin films would enhance the surface area and reactivity, leading to a potential improvement of the photoelectrochemical (PEC) performance. Herein, the preparation of porous barium titanate (pBTO) thin films by a soft template-assisted sol-gel method is reported, and the control of porosity using different organic/inorganic ratios is verified by the combination of scanning electron microscopy and ellipsometry techniques. Using piezoresponse force microscopy, the switching of ferroelectric domains in pBTO thin films is observed, confirming that the ferroelectric polarization is still retained in the porous structures. In addition, the presence of porosity in pBTO thin films leads to a clear improvement of the PEC response. By electrochemical poling, we also demonstrated the tuning of the PEC performance of pBTO thin films via ferroelectric polarization. Our work offers a simple and low-cost approach to control the morphology optimization of ferroelectric thin films, which could open up the development of materials with great potential for PEC applications.
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Affiliation(s)
- Adriana Augurio
- School
of Engineering and Material Science and Materials Research Institute, Queen Mary University of London, E1 4NS London, U.K.
| | - Alberto Alvarez-Fernandez
- Department
of Chemical Engineering, University College
London, Torrington Place, WC1E 7JE London, U.K.
| | | | - Bede Pittenger
- AFM
Unit, Bruker Nano Surfaces, 93117 Santa Barbara, California, United States
| | - Peter De Wolf
- AFM
Unit, Bruker Nano Surfaces, 93117 Santa Barbara, California, United States
| | - Stefan Guldin
- Department
of Chemical Engineering, University College
London, Torrington Place, WC1E 7JE London, U.K.
| | - Joe Briscoe
- School
of Engineering and Material Science and Materials Research Institute, Queen Mary University of London, E1 4NS London, U.K.
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Alvarez-Fernandez A, Fornerod MJ, Reid B, Guldin S. Solvent Vapor Annealing for Controlled Pore Expansion of Block Copolymer-Assembled Inorganic Mesoporous Films. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:3297-3304. [PMID: 35235337 PMCID: PMC9097528 DOI: 10.1021/acs.langmuir.2c00074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 02/23/2022] [Indexed: 05/18/2023]
Abstract
Mesoporous inorganic thin films are promising materials architectures for a variety of high-value applications, ranging from optical coatings and purification membranes to sensing and energy storage devices. Having precise control over the structural parameters of the porous network is crucial for broadening their applicability. To this end, the use of block copolymers (BCP) as sacrificial structure-directing agents via micelle coassembly is a particularly attractive route, since the resultant pore size is directly related to scaling laws for the radius of gyration of the pore-forming macromolecule. However, tailoring the molecular weight of the BCP via bespoke synthesis is an elaborate process that requires precise control over highly sensitive reactions conditions. Alternative methods have emerged, based on supramolecular assembly or the addition of different swelling agents. Nevertheleses, to date, these present a negative impact on the structural order and pore size dispersity of the final inorganic mesoporous films. In this work, we propose a novel and effective method for control over pore size, porosity, and structural order, which relies on a synergistic combination of BCP selective swelling via solvent vapor annealing (SVA) and locking of the structure by condensation of the inorganic sol-gel precursors. The results obtained in this work for TiO2 establish SVA as a new, straightforward, simple, and powerful route for the fabrication of mesoporous thin-film materials with controllable structural characteristics.
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7
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Islam MS, Wakabayashi R, Kimura T. Enhanced γ-phase crystallinity of Al 2O 3 frameworks at the concave surface of PS- b-PEO templated spherical pores. Dalton Trans 2021; 50:7191-7197. [PMID: 33871514 DOI: 10.1039/d1dt00719j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The crystallinity of inorganic solids like metal oxides after the porosity design is the crucial factor that should be investigated for enhancing their physicochemical properties. In most cases, metal oxide frameworks around mesopores, that are designed through the supramolecular mediated approach, are resulted to be amorphous. Accordingly, a rational guideline has been required for enhancing the crystallinity of frameworks at such concave surfaces. We have so far surveyed a crystallization behavior of alumina (Al2O3) frameworks to its γ-phase around spherical mesopores (∼40 nm) and discussed further transition to the α-phase around much larger pores (∼200 nm). In this paper, we prepared new and helpful Al2O3 powders having PS-b-PEO templated pores (∼25 nm and ∼75 nm) smaller than those of our previous case. After careful discussion of the pore size variation by considering the molecular structure of PS-b-PEO, we explained the crystallization behavior of the Al2O3 frameworks to enhance its γ-crystallinity. This knowledge is quite beneficial for designing highly porous Al2O3 powders with abundant crystallinity for use as catalyst supports, which is very useful for assessing synthetic procedures of other mesoporous metal oxides having high crystallinity.
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Affiliation(s)
- Md Saidul Islam
- Innovative Functional Material Research institute, National Institute of Advanced Industrial Science and Technology (AIST), Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan.
| | - Ryutaro Wakabayashi
- Innovative Functional Material Research institute, National Institute of Advanced Industrial Science and Technology (AIST), Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan.
| | - Tatsuo Kimura
- Innovative Functional Material Research institute, National Institute of Advanced Industrial Science and Technology (AIST), Shimoshidami, Moriyama-ku, Nagoya 463-8560, Japan.
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