Dispersion and Sorting of Nanomaterials
Solid State and Surface Chemistry, Material Synthesis
Final Report Abstract
In summary, the highly prosperous scientific environment at the host institution TCD with its strong dedication to research on layered materials has proven to be the ideal platform to achieve the ambitious goals of the research proposal. Intense collaboration with researchers from in total six groups have been readily established to take the core research of this proposal beyond initial goals and anticipation. This is manifested in 11 joint publications published or submitted to date in high ranking journals (for example 2 x Nature Communications, Nature Materials, Angewandte Chemie). It should be noted that the research environment was highly dynamic so that some parts of the initial proposal were redirected and substituted with other projects to adjust to the interests at the host institution and to fully exploit the capacities available. The main scientific achievements include: - Better understanding of liquid exfoliation and subsequent size control by centrifugation - Development of quantitative in situ spectroscopic metrics to assess mean lateral dimensions and thickness of liquid-exfoliated MoS2/TMDs in dispersion by extinction and absorbance spectroscopy. - Use of the high throughput spectroscopic metrics of TMDs to i) Prepare monolayer-rich TMD dispersions that allow for the study of monolayer photoluminescence in liquids; ii) Develop new scalable size selection techniques based on salting out iii) Establish quantitative metrics based on liquid Raman and photoluminescence to determine the monolayer content in a dispersion. - Development of quantitative metrics based on Raman and absorbance spectroscopy to determine mean number of layers and lateral dimensions of LPE graphene. - Insights in highly scalable alternative exfoliation techniques using shear exfoliation (including size control during the exfoliation). - Demonstration of the exfoliation of 2D materials beyond TMDs and graphene (MoO3, GaS, black phosphorus) including the quantification of lateral dimensions and/or thickness by spectroscopic metrics based on absorbance, extinction and scattering spectra. - Development of two novel routes to functionalise the basal plane of MoS2. In general, this means that the ideal foundation has now been laid to fine-tune and control sizes and thicknesses of liquid-exfoliated nanosheets – either by post exfoliation size selection or careful process optimisation. High throughput spectroscopic protocols were establish that can now be applied. Without such metrics, each step in a process chain would need to be monitored by time-consuming statistical microscopic analysis. Up until now, this was the reason why progress in controlling size and thickness of exfoliated nanomaterials was rather slow and a general understanding of the exfoliation process itself was lacking. Since the properties of the 2D materials are so sensitive to their size and thickness, it is very important to be able to have good control over their dimensions. This will be extremely useful to test the application potential of these materials in a number of areas and to develop new and efficient size selection techniques in the future. In addition, the sample quality in terms of monolayer content has already been significantly improved the past two years. For example, monolayer-rich dispersions can be produced that show notable photoluminescence in the liquid. The photoluminescence response will be extremely sensitive to the chemical environment of the nanosheets. Thus, it can be used as fingerprint to study the interaction between different nanosheets or with molecules/polymers in noncovalent functionalisation. This can be a game-changer in general materials design and the foundation to build hybrid structures and hierarchical architectures especially in combination with the elaborated basal-plane functionalisation techniques.
Publications
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Edge and Confinement Effects Allow in situ Measurement of Size and Thickness of Liquid-Exfoliated Nanosheets. Nature Communications 2014, 5, 4576
Backes, C.; Smith, R. J.; McEvoy, N.; Berner, N. C.; McCloskey, D.; Nerl, H. C.; O’Neill, A.; King, P. J.; Higgins, T.; Hanlon, D.; Scheuschner, N.; Maultzsch, J.; Houben, L.; Duesberg, G. S.; Donegan, J. F.; Nicolosi, V.; Coleman, J. N.
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Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids. Nature Materials 2014, 13 (6), 624-630
Paton, K. R.; Varrla, E.; Backes, C.; Smith, R. J.; Khan, U.; O’Neill, A.; Boland, C.; Lotya, M.; Istrate, O. M.; King, P.; Higgins, T.; Barwich, S.; May, P.; Puczkarski, P.; Ahmed, I.; Moebius, M.; Pettersson, H.; Long, E.; Coelho, J.; O’Brien, S. E.; McGuire, E. K.; Sanchez, B. M.; Duesberg, G. S.; McEvoy, N.; Pennycook, T. J.; Downing, C.; Crossley, A.; Nicolosi, V.; Coleman, J. N.
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Functionalization of liquid-exfoliated two-dimensional 2H- MoS2 Angewandte Chemie, International Edition 2015, 54(9), 2638-2642
Backes, C.; Berner, N. C.; Chen, X.; Lafargue, P.; LaPlace, P.; Freeley, M.; Duesberg, G. S.; Coleman, J. N.; McDonald, A. R.
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Large-Scale Production of Size-Controlled MoS2 Nanosheets by Shear Exfoliation. Chemistry of Materials 2015, 27 (3), 1129–1139
Varrla, E.; Backes, C.; Paton, K. R.; Harvey, A.; Gholamvand, Z.; McCauley, J.; Coleman, J. N.
