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Jancke S, Liu C, Wang R, Sarkar S, Besford QA, König TAF, Popp J, Cialla-May D, Rossner C. Turning on hotspots: supracolloidal SERS probes made brilliant by an external activation mechanism. NANOSCALE 2023; 15:18687-18695. [PMID: 37941432 DOI: 10.1039/d3nr05121h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2023]
Abstract
We achieved external activation of local hot-spot sites in supracolloidal assembly structures. The concept was demonstrated by boosting surface-enhanced Raman scattering (SERS) efficiency by one order of magnitude through a heating-induced process. Our approach involves assembling gold nanoparticles with distinct dimensions, i.e. 16 and 80 nm, into well-defined planet-satellite-type arrangement structures using thermoresponsive (poly(N-isopropylacrylamide)) star polymer linkers. Insights into the assembly process were obtained by calculations within the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory framework. We observe one order of magnitude increase in SERS enhancement by a heating-induced volume-phase transition. This magnification aligns with simulations run using the finite-difference time-domain (FDTD) method. The implications of this adaptive supracolloidal concept are twofold: Firstly, our approach bypasses limitations of existing systems that are associated with the limited accessibility of electromagnetic hot-spot sites in strongly coupled, static assemblies of plasmonic nanoparticles, by providing the capability of dynamic hot-spot re-configuration. Second, these externally activated probes offer promising opportunities for the development of messenger materials and associated sensing strategies.
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Affiliation(s)
- Sophie Jancke
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Physikalische Chemie und Physik der Polymere, D-01069 Dresden, Germany.
| | - Chen Liu
- Leibniz Institute of Photonic Technology, Member of Leibniz Health Technologies, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Albert Einstein Straße 9, 07745 Jena, Germany
- Institute of Physical Chemistry (IPC) and Abbe Center of Photonics (ACP), Friedrich Schiller University Jena, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Helmholtzweg 4, 07743 Jena, Germany
| | - Ruosong Wang
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Physikalische Chemie und Physik der Polymere, D-01069 Dresden, Germany.
| | - Swagato Sarkar
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Physikalische Chemie und Physik der Polymere, D-01069 Dresden, Germany.
| | - Quinn A Besford
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Physikalische Chemie und Physik der Polymere, D-01069 Dresden, Germany.
| | - Tobias A F König
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Physikalische Chemie und Physik der Polymere, D-01069 Dresden, Germany.
- Dresden Center for Intelligent Materials (DCIM), Technische Universität Dresden, D-01069 Dresden, Germany
- Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany
- Center for Advancing Electronics Dresden (cfaed), Technische Universität Dresden, Helmholtzstraße 18, 01069 Dresden, Germany
| | - Jürgen Popp
- Leibniz Institute of Photonic Technology, Member of Leibniz Health Technologies, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Albert Einstein Straße 9, 07745 Jena, Germany
- Institute of Physical Chemistry (IPC) and Abbe Center of Photonics (ACP), Friedrich Schiller University Jena, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Helmholtzweg 4, 07743 Jena, Germany
| | - Dana Cialla-May
- Leibniz Institute of Photonic Technology, Member of Leibniz Health Technologies, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Albert Einstein Straße 9, 07745 Jena, Germany
- Institute of Physical Chemistry (IPC) and Abbe Center of Photonics (ACP), Friedrich Schiller University Jena, Member of the Leibniz Centre for Photonics in Infection Research (LPI), Helmholtzweg 4, 07743 Jena, Germany
| | - Christian Rossner
- Leibniz-Institut für Polymerforschung Dresden e.V., Institut für Physikalische Chemie und Physik der Polymere, D-01069 Dresden, Germany.
- Dresden Center for Intelligent Materials (DCIM), Technische Universität Dresden, D-01069 Dresden, Germany
- Faculty of Chemistry and Food Chemistry, Technische Universität Dresden, Bergstraße 66, 01069 Dresden, Germany
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Nagai S, Urata S, Suga K, Fukuma T, Hayashi Y, Miyazawa K. Three-dimensional ordering of water molecules reflecting hydroxyl groups on sapphire (001) and α-quartz (100) surfaces. NANOSCALE 2023; 15:13262-13271. [PMID: 37539559 DOI: 10.1039/d3nr02498a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/05/2023]
Abstract
Water molecules on oxide surfaces influence the chemical reactivity and molecular adsorption behavior of oxides. Herein, three-dimensional atomic force microscopy (3D-AFM) and molecular dynamics simulations are used to visualize the surface hydroxyl (OH) groups and their hydration structures on sapphire (001) and α-quartz (100) surfaces at the atomic-scale. The obtained results revealed that the spatial density distributions and hydrogen-bonding strengths of surface OH groups affect their local hydration structures. In particular, the force curves obtained by 3D-AFM suggest that the hydration forces of water molecules intensify at sites where water molecules strongly interact with the surface OH groups. The insights obtained in this study deepen our understanding of the affinities of Al2O3 and SiO2 for water molecules and contribute to the use of 3D-AFM in the investigation of atomic-scale hydration structures on various surfaces, thereby benefiting a wide range of research fields dealing with solid-liquid interfaces.
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Affiliation(s)
- Sho Nagai
- Innovative Technology Laboratories, AGC Inc., 1-1 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Shingo Urata
- Planning Division, AGC Inc., 1-1 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Kent Suga
- Innovative Technology Laboratories, AGC Inc., 1-1 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Takeshi Fukuma
- Faculty of Frontier Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
| | - Yasuo Hayashi
- Innovative Technology Laboratories, AGC Inc., 1-1 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa 230-0045, Japan
| | - Keisuke Miyazawa
- Faculty of Frontier Engineering, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan.
- Nano Life Science Institute (WPI-NanoLSI), Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan
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3
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Besford QA, Van den Heuvel W, Christofferson AJ. Dipolar Dispersion Forces in Water-Methanol Mixtures: Enhancement of Water Interactions upon Dilution Drives Self-Association. J Phys Chem B 2022; 126:6231-6239. [PMID: 35976055 DOI: 10.1021/acs.jpcb.2c04638] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mixtures of short-chain alcohols and water produce anomalous thermodynamic and structural quantities, including molecular segregation into water-rich and alcohol-rich components. Herein, we used molecular dynamics simulations with polarizable models to investigate interactions that could drive the self-association of water molecules in mixtures with methanol (MeOH). As water was diluted with MeOH, significant changes in the distribution of molecules and solvation properties occurred, where water exhibited a clear preference for self-association. When common structural quantities were analyzed, it was found that there was a clear reduction in water-water hydrogen bonding and tetrahedral order (both in terms of typical bulk behavior), contrary to the observed water self-association. However, when dipolar dispersion forces between all molecules as a function of system composition were analyzed, it was found that water-water dipolar interactions became significantly stronger with dilution (6-fold stronger interaction in 75% MeOH compared to 0% MeOH). This was only observed for water, where MeOH-MeOH interactions became weaker as the systems were more dilute in MeOH. These forces result from specific dipole orientations, likely occurring to adopt lower energy configurations (i.e., head-to-tail or antiparallel). For water, this may result from lost other interactions (e.g., hydrogen bonding), leading to more rotational freedom between the dipole moments. These intriguing changes in dipolar interactions, which directly result from structural changes, can therefore explain, in part, the driving force for water self-association in MeOH-water mixtures.
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Affiliation(s)
- Quinn A Besford
- Leibniz-Institut für Polymerforschung e.V., Hohe Str. 6, 01069 Dresden, Germany
| | - Willem Van den Heuvel
- Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, DK-5230 Odense M, Denmark
| | - Andrew J Christofferson
- School of Science, STEM College, RMIT University, Melbourne, Victoria 3001, Australia.,ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, Victoria 3001, Australia
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4
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Long Z, You L, Xu F, Tang X, Ding Y, Khanal A, Miao Y. Nanomechanical-atomistic insights on interface interactions in asphalt mixtures with various chloride ion erosion statuses using AFM and MD simulation. J Colloid Interface Sci 2022; 628:891-909. [DOI: 10.1016/j.jcis.2022.08.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 07/16/2022] [Accepted: 08/02/2022] [Indexed: 10/16/2022]
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Bulk and interfacial nanostructure and properties in deep eutectic solvents: Current perspectives and future directions. J Colloid Interface Sci 2021; 608:2430-2454. [PMID: 34785053 DOI: 10.1016/j.jcis.2021.10.163] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2021] [Revised: 10/25/2021] [Accepted: 10/26/2021] [Indexed: 12/25/2022]
Abstract
Deep eutectic solvents (DESs) are a tailorable class of solvents that are rapidly gaining scientific and industrial interest. This is because they are distinct from conventional molecular solvents, inherently tuneable via careful selection of constituents, and possess many attractive properties for applications, including catalysis, chemical extraction, reaction media, novel lubricants, materials chemistry, and electrochemistry. DESs are a class of solvents composed solely of hydrogen bond donors and acceptors with a melting point lower than the individual components and are often fluidic at room temperature. A unique feature of DESs is that they possess distinct bulk liquid and interfacial nanostructure, which results from intra- and inter-molecular interactions, including coulomb forces, hydrogen bonding, van der Waals interactions, electrostatics, dispersion forces, and apolar-polar segregation. This nanostructure manifests as preferential spatial arrangements of the different species, and exists over several length scales, from molecular- to nano- and meso-scales. The physicochemical properties of DESs are dictated by structure-property relationships; however, there is a significant gap in our understanding of the underlying factors which govern their solvent properties. This is a major limitation of DES-based technologies, as nanostructure can significantly influence physical properties and thus potential applications. This perspective provides an overview of the current state of knowledge of DES nanostructure, both in the bulk liquid and at solid interfaces. We provide definitions which clearly distinguish DESs as a unique solvent class, rather than a subset of ILs. An appraisal of recent work provides hints towards trends in structure-property relationships, while also highlighting inconsistencies within the literature suggesting new research directions for the field. It is hoped that this review will provide insight into DES nanostructure, their potential applications, and development of a robust framework for systematic investigation moving forward.
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Kadaoluwa Pathirannahalage SP, Meftahi N, Elbourne A, Weiss ACG, McConville CF, Padua A, Winkler DA, Costa Gomes M, Greaves TL, Le TC, Besford QA, Christofferson AJ. Systematic Comparison of the Structural and Dynamic Properties of Commonly Used Water Models for Molecular Dynamics Simulations. J Chem Inf Model 2021; 61:4521-4536. [PMID: 34406000 DOI: 10.1021/acs.jcim.1c00794] [Citation(s) in RCA: 56] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Water is a unique solvent that is ubiquitous in biology and present in a variety of solutions, mixtures, and materials settings. It therefore forms the basis for all molecular dynamics simulations of biological phenomena, as well as for many chemical, industrial, and materials investigations. Over the years, many water models have been developed, and it remains a challenge to find a single water model that accurately reproduces all experimental properties of water simultaneously. Here, we report a comprehensive comparison of structural and dynamic properties of 30 commonly used 3-point, 4-point, 5-point, and polarizable water models simulated using consistent settings and analysis methods. For the properties of density, coordination number, surface tension, dielectric constant, self-diffusion coefficient, and solvation free energy of methane, models published within the past two decades consistently show better agreement with experimental values compared to models published earlier, albeit with some notable exceptions. However, no single model reproduced all experimental values exactly, highlighting the need to carefully choose a water model for a particular study, depending on the phenomena of interest. Finally, machine learning algorithms quantified the relationship between the water model force field parameters and the resulting bulk properties, providing insight into the parameter-property relationship and illustrating the challenges of developing a water model that can accurately reproduce all properties of water simultaneously.
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Affiliation(s)
- Sachini P Kadaoluwa Pathirannahalage
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia.,Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, CNRS, Lyon 69342, France
| | - Nastaran Meftahi
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Aaron Elbourne
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Alessia C G Weiss
- Leibniz-Institut für Polymerforschung e.V., Hohe Straße 6, 01069 Dresden, Germany
| | - Chris F McConville
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia.,Institute for Frontier Materials, Deakin University, Geelong, Victoria 3220, Australia
| | - Agilio Padua
- Laboratoire de Chimie, Ecole Normale Supérieure de Lyon, CNRS, Lyon 69342, France
| | - David A Winkler
- School of Biochemistry and Genetics, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.,Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria 3052, Australia.,School of Pharmacy, University of Nottingham, Nottingham NG7 2QL, U.K
| | | | - Tamar L Greaves
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia
| | - Tu C Le
- School of Engineering, RMIT University, Melbourne, Victoria 3001, Australia
| | - Quinn A Besford
- Leibniz-Institut für Polymerforschung e.V., Hohe Straße 6, 01069 Dresden, Germany
| | - Andrew J Christofferson
- School of Science, RMIT University, Melbourne, Victoria 3000, Australia.,ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, Victoria 3000, Australia
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Hammons JA, Besford QA, Ilavsky J, Christofferson AJ. Manipulating meso-scale solvent structure from Pd nanoparticle deposits in deep eutectic solvents. J Chem Phys 2021; 155:074505. [PMID: 34418930 DOI: 10.1063/5.0058605] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Deep Eutectic Solvents (DESs) are complex solutions that present unique challenges compared to traditional solvents. Unlike most aqueous electrolytes and ionic liquids, DESs have delicate hydrogen bond networks that are responsible for their highly sensitive compositional dependence on the melting point. Prior work has demonstrated a unique nanoscale structure both experimentally and theoretically that brings both challenges and opportunities to their adoption in traditional electrochemical processes. In this study, we use in situ sample-rotated ultra-small angle x-ray scattering to resolve the near-interface solvent structure after electrodepositing Pd nanoparticles onto a glassy carbon electrode in choline chloride:urea and choline chloride:ethylene glycol DESs. Our results indicate that a hierarchical solvent structure can be observed on the meso-scale in the choline chloride:urea and choline chloride:ethylene glycol systems. Importantly, this extended solvent structure increases between -0.3 V and -0.5 V (vs Ag/AgCl) and remains high until -0.9 V (vs Ag/AgCl). Experimentally, the nature of this structure is more pronounced in the ethylene glycol system, as evidenced by both the x-ray scattering and the electrochemical impedance spectroscopy. Molecular dynamics simulations and dipolar orientation analysis reveal that chloride delocalization near the Pd interface and long-range interactions between the choline and each hydrogen bond donor (HBD) are very different and qualitatively consistent with the experimental data. These results show how the long-range solvent-deposit interactions can be tuned by changing the HBD in the DES and the applied potential.
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Affiliation(s)
- Joshua A Hammons
- Lawrence Livermore National Laboratory, Livermore, California 94550, USA
| | - Quinn A Besford
- Leibniz-Institut für Polymerforschung e. V., Hohe Straße 6, 01069 Dresden, Germany
| | - Jan Ilavsky
- Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA
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Elbourne A, Besford QA, Meftahi N, Crawford RJ, Daeneke T, Greaves TL, McConville CF, Bryant G, Bryant SJ, Christofferson AJ. The Impact of Water on the Lateral Nanostructure of a Deep Eutectic Solvent–Solid Interface. Aust J Chem 2021. [DOI: 10.1071/ch21078] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Deep eutectic solvents (DESs) are tuneable solvents with attractive properties for numerous applications. Their structure–property relationships are still under investigation, especially at the solid–liquid interface. Moreover, the influence of water on interfacial nanostructure must be understood for process optimization. Here, we employ a combination of atomic force microscopy and molecular dynamics simulations to determine the lateral and surface-normal nanostructure of the DES choline chloride:glycerol at the mica interface with different concentrations of water. For the neat DES system, the lateral nanostructure is driven by polar interactions. The surface adsorbed layer forms a distinct rhomboidal symmetry, with a repeat spacing of ~0.9 nm, comprising all DES species. The adsorbed nanostructure remains largely unchanged in 75 mol-% DES compared with pure DES, but at 50 mol-%, the structure is broken and there is a compromise between the native DES and pure water structure. By 25 mol-% DES, the water species dominates the adsorbed liquid layer, leaving very few DES species aggregates at the interface. In contrast, the near-surface surface-normal nanostructure, over a depth of ~3 nm from the surface, remains relatively unchanged down to 25 mol-% DES where the liquid arrangement changed. These results demonstrate not only the significant influence that water has on liquid nanostructure, but also show that there is an asymmetric effect whereby water disrupts the nanostructure to a greater degree closer to the surface. This work provides insight into the complex interactions between DES and water and may enhance their optimization for surface-based applications.
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Monet G, Bresme F, Kornyshev A, Berthoumieux H. Nonlocal Dielectric Response of Water in Nanoconfinement. PHYSICAL REVIEW LETTERS 2021; 126:216001. [PMID: 34114838 DOI: 10.1103/physrevlett.126.216001] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Revised: 04/19/2021] [Accepted: 04/29/2021] [Indexed: 06/12/2023]
Abstract
Recent experiments reporting a very low dielectric permittivity for nanoconfined water have renewed the interest in the structure and dielectric properties of water in narrow gaps. Here, we describe such systems with a minimal Landau-Ginzburg field theory composed of a nonlocal bulk-determined term and a local water-surface interaction term. We show how the interplay between the boundary conditions and intrinsic bulk correlations encodes the dielectric properties of confined water. Our theoretical analysis is supported by molecular dynamics simulations and comparison with the experimental data.
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Affiliation(s)
- G Monet
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée (LPTMC, UMR 7600), F-75005 Paris, France
| | - F Bresme
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, W12 0BZ 2AZ London, United Kingdom
| | - A Kornyshev
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, W12 0BZ 2AZ London, United Kingdom
| | - H Berthoumieux
- Sorbonne Université, CNRS, Laboratoire de Physique Théorique de la Matière Condensée (LPTMC, UMR 7600), F-75005 Paris, France
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Elbourne A, Meftahi N, Greaves TL, McConville CF, Bryant G, Bryant SJ, Christofferson AJ. Nanostructure of a deep eutectic solvent at solid interfaces. J Colloid Interface Sci 2021; 591:38-51. [PMID: 33592524 DOI: 10.1016/j.jcis.2021.01.089] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/26/2021] [Accepted: 01/27/2021] [Indexed: 12/24/2022]
Abstract
HYPOTHESIS Deep eutectic solvents (DESs) are an attractive class of tunable solvents. However, their uptake for relevant applications has been limited due to a lack of detailed information on their structure-property relationships, both in the bulk and at interfaces. The lateral nanostructure of the DES-solid interfaces is likely to be more complex than previously reported and requires detailed, high-resolution investigation. EXPERIMENTS We employ a combination of high-resolution amplitude-modulated atomic force microscopy and molecular dynamics simulations to elucidate the lateral nanostructure of a DES at the solid-liquid interface. Specifically, the lateral and near-surface nanostructure of the DES choline chloride:glycerol is probed at the mica and highly-ordered pyrolytic graphite interfaces. FINDINGS The lateral nanostructure of the DES-solid interface is heterogeneous and well-ordered in both systems. At the mica interface, the DES is strongly ordered via polar interactions. The adsorbed layer has a distinct rhomboidal symmetry with a repeat spacing of ~0.9 nm comprising all DES species. At the highly ordered pyrolytic graphite interface, the adsorbed layer appears distinctly different, forming an apolor-driven row-like structure with a repeat spacing of ~0.6 nm, which largely excludes the chloride ion. The interfacial nanostructure results from a delicate balance of substrate templating, liquid-liquid interactions, species surface affinity, and packing constraints of cations, anions, and molecular components within the DES. For both systems, distinct near-surface nanostructural layering is observed, which becomes more pronounced close to the substrate. The surface nanostructures elucidated here significantly expand our understanding of DES interfacial behavior and will enhance the optimization of DES systems for surface-based applications.
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Affiliation(s)
- Aaron Elbourne
- School of Science, RMIT University, Melbourne, VIC 3000, Australia.
| | - Nastaran Meftahi
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Tamar L Greaves
- School of Science, RMIT University, Melbourne, VIC 3000, Australia
| | - Christopher F McConville
- School of Science, RMIT University, Melbourne, VIC 3000, Australia; Institute for Frontier Materials, Deakin University, Geelong, Victoria 3216, Australia
| | - Gary Bryant
- School of Science, RMIT University, Melbourne, VIC 3000, Australia
| | - Saffron J Bryant
- School of Science, RMIT University, Melbourne, VIC 3000, Australia.
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