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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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Jones SH, King MD, Rennie AR, Ward AD, Campbell RA, Hughes AV. Aqueous Radical Initiated Oxidation of an Organic Monolayer at the Air-Water Interface as a Proxy for Thin Films on Atmospheric Aerosol Studied with Neutron Reflectometry. J Phys Chem A 2023; 127:8922-8934. [PMID: 37830513 PMCID: PMC10614302 DOI: 10.1021/acs.jpca.3c03846] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 09/12/2023] [Indexed: 10/14/2023]
Abstract
Neutron reflectometry has been used to study the radical initiated oxidation of a monolayer of the lipid 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) at the air-solution interface by aqueous-phase hydroxyl, sulfate, and nitrate radicals. The oxidation of organic films at the surface of atmospheric aqueous aerosols can influence the optical properties of the aerosol and consequently can impact Earth's radiative balance and contribute to modern climate change. The amount of material at the air-solution interface was found to decrease on exposure to aqueous-phase radicals which was consistent with a multistep degradation mechanism, i.e., the products of reaction of the DSPC film with aqueous radicals were also surface active. The multistep degradation mechanism suggests that lipid molecules in the thin film degrade to form progressively shorter chain surface active products and several reactive steps are required to remove the film from the air-solution interface. Bimolecular rate constants for oxidation via the aqueous phase OH radical cluster around 1010 dm3 mol-1 s-1. Calculations to determine the film lifetime indicate that it will take ∼4-5 days for the film to degrade to 50% of its initial amount in the atmosphere, and therefore attack by aqueous radicals on organic films could be atmospherically important relative to typical atmospheric aerosol lifetimes.
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Affiliation(s)
- Stephanie H. Jones
- Centre
of Climate, Ocean and Atmosphere, Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, U.K.
- STFC,
Central Laser Facility, Research Complex
at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Martin D. King
- Centre
of Climate, Ocean and Atmosphere, Department of Earth Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, U.K.
| | - Adrian R. Rennie
- Department
of Chemistry, Angström Laboratory, Uppsala University, 75121 Uppsala, Sweden
| | - Andrew D. Ward
- STFC,
Central Laser Facility, Research Complex
at Harwell, Rutherford Appleton Laboratory, Harwell Oxford, Didcot, Oxfordshire OX11 0FA, U.K.
| | - Richard A. Campbell
- Institut
Laue-Langevin, BP 156, 6, 71 avenue des Martyrs, CS 20156, F-38042
Cedex 9 Grenoble, France
| | - Arwel V. Hughes
- ISIS
Pulsed Neutron and Muon source, Rutherford
Appleton Laboratory, Harwell Oxford, Oxfordshire OX11 0QX, U.K.
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McGrory MR, Shepherd RH, King MD, Davidson N, Pope FD, Watson IM, Grainger RG, Jones AC, Ward AD. Mie scattering from optically levitated mixed sulfuric acid-silica core-shell aerosols: observation of core-shell morphology for atmospheric science. Phys Chem Chem Phys 2022; 24:5813-5822. [PMID: 35226003 DOI: 10.1039/d1cp04068e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Sulfuric acid is shown to form a core-shell particle on a micron-sized, optically-trapped spherical silica bead. The refractive indices of the silica and sulfuric acid, along with the shell thickness and bead radius were determined by reproducing Mie scattered optical white light as a function of wavelength in Mie spectroscopy. Micron-sized silica aerosols (silica beads were used as a proxy for atmospheric silica minerals) were levitated in a mist of sulfuric acid particles; continuous collection of Mie spectra throughout the collision of sulfuric acid aerosols with the optically trapped silica aerosol demonstrated that the resulting aerosol particle had a core-shell morphology. Contrastingly, the collision of aqueous sulfuric acid aerosols with optically trapped polystyrene aerosol resulted in a partially coated system. The light scattering from the optically levitated aerosols was successfully modelled to determine the diameter of the core aerosol (±0.003 μm), the shell thickness (±0.0003 μm) and the refractive index (±0.007). The experiment demonstrated that the presence of a thin film rapidly changed the light scattering of the original aerosol. When a 1.964 μm diameter silica aerosol was covered with a film of sulfuric acid 0.287 μm thick, the wavelength dependent Mie peak positions resembled sulfuric acid. Thus mineral aerosol advected into the stratosphere would likely be coated with sulfuric acid, with a core-shell morphology, and its light scattering properties would be effectively indistinguishable from a homogenous sulfuric acid aerosol if the film thickness was greater than a few 100 s of nm for UV-visible wavelengths.
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Affiliation(s)
- Megan R McGrory
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK. .,Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Rosalie H Shepherd
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK. .,Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Martin D King
- Department of Earth Sciences, Royal Holloway, University of London, Egham, Surrey, TW20 0EX, UK
| | - Nicholas Davidson
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - Francis D Pope
- School of Geography, Earth & Environmental Sciences, University of Birmingham, Birmingham, B15 2TT, UK
| | - I Matthew Watson
- School of Earth Science, University of Bristol, Wills Memorial Building, Bristol, BS8 1RJ, UK
| | - Roy G Grainger
- National Centre for Earth Observation, Atmospheric, Oceanic and Planetary Physics, University of Oxford, Parks Road, Oxford OX1 3PU, UK
| | - Anthony C Jones
- Met Office, Fitzroy Road, Exeter, EX1 3PB, UK.,College of Engineering Maths and Physical Sciences, University of Exeter, Exeter, EX4 4PY, UK
| | - Andrew D Ward
- Central Laser Facility, Research Complex, STFC Rutherford Appleton Laboratory, Oxford, OX11 0FA, UK.
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