Dielectric measurement of two-dimensional nanoconfined liquids

Project Information

Dielec2DNanoLiquids

Grant agreement ID: 793394

DOI

10.3030/793394

Project closed

EC signature date 31 July 2018

Start date 1 September 2018

End date 31 August 2020

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 195 454,80

EU contribution

€ 195 454,80

Coordinated by

THE UNIVERSITY OF MANCHESTER
United Kingdom

Periodic Reporting for period 1 - Dielec2DNanoLiquids (Dielectric measurement of two-dimensional nanoconfined liquids)

Reporting period: 2018-09-01 to 2020-08-31

Summary of the context and overall objectives of the project

The possibility of combining 2D materials in heterostructures allows the fabrication of new devices with novel functionalities, further expanding the opportunities of new science and new technologies. The properties of 2D crystals provide a unique platform to observe molecules under confinement, to artificially create new molecular phases and to exploit them to develop devices with new functionalities.
SPM techniques are the ideal tool for probing the properties of novel 2D nano-confined systems, in particular, the dielectric properties of nano-confined molecules, since they have a strong impact on many important physical phenomena. However, experimental evidence is lacking because dielectric measurements at such a small scale are technically challenging. To overcome this lack of experimental information, the overall objectives of this project were:
-Fabrication of 2D nanoenclosures/nanochannels that allow measurement of the dielectric properties of nanoconfined liquids with the scanning probe approach.
-Development of SPM tools/setups for in situ dielectric characterization of 2D nanoconfined liquids and chemical reactions under controlled conditions (temperature, liquid flow/concentration).
-Study of local electric polarization properties of 2D nanoconfined molecular fluids and their link to molecular organization (structure, phase) at solid interfaces by using the developed SPM tools.
We have developed and built new setups for the study of the dielectric properties of nanoconfined liquids, observing a decrease of the out-of-plane dielectric constant of confined water. Additionally, we studied the possible influence of topographic features and alignment in the electric and dielectric properties of 2D crystal devices.
In conclusion, the action has been successfully implemented by the unique combination of 2D materials-based confining structures with customized scanning probe tools for the characterization of liquids under extreme confinement at the nanoscale.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

We have produced two different set of devices by van der Waals assembly using atomically flat crystals: 2D nanoenclosures that confine liquids in nanodroplets and adlayers and heterostructures with nanochannels that have apertures to allow varying the solutions and their molecular/ion concentration.
We have designed and fabricated customized tip/sample holders for our nanoenclosures and nanochannels. They allow working in a variable temperature range and to control the molecular/ion concentration of the confined liquids inside the nanochannels.
We have carried out morphological and dielectric characterization of the 2D nanoenclosures and nanochannels with the developed tools, yielding low dielectric constant values in the range 3, which is found in ordered ice. Importantly, the value is obtained on nanoslits with different crystals. Due to the shutdown of the labs for 5 months, we were not able to fully complete the experimental characterization of the new nanoenclosures and nanochannels. This is currently under progress and publications are in preparation. The results obtained in this project are a new important step in our understanding of the dielectric properties of confined water. Furthermore, additional important results were obtained during dielectric characterization of our devices and their topographic features (wrinkles and bubbles). In particular, we observed for the first time piezoelectricity in monolayer hBN and interfacial ferroelectricity in hBN marginally twisted crystals
The dissemination of the results of the action includes publication in several high profile journals, talks at international conferences and seminars in recognized international institutions. Dr. Ares has also been frequently engaged in outreach activities before and during the project, such as an appearance in a Spanish TV show showing the National Graphene Institute (NGI), carrying out lab tours for students and visitors at the NGI, training students on the use of scanning probe microscopies and writing press articles on our research. He also won the first prize of the Royal Microscopical Society (RMS) SPM International Scientific Imaging Competition 2019 (and donated all image merchandising royalties towards funding the RMS Microscope Activity Kits for primary schools). The main results of the research activity are also disseminated through social media, having active profiles on Twitter, reaching a variety of both specific and general audiences.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

Once the action is finished, we can conclude that it has successfully achieved most of its objectives and milestones for the period. The experimental achievements on the dielectric constant of confined water provide much-needed feedback for theories describing water-mediated surface interactions, and helps the understanding the physics of these systems, with implications in many fields. We have also developed new tools for the characterization on the nanoscale, which can be used for wider studies of multiple properties with applications on different areas.
Our findings on the role of topographical features and alignment in 2D materials and van der Waals heterostrucutures lead to adding piezoelectricity to the known properties of hBN, highlight the important role of the residual strain in optical properties, provide an invaluable, indirect metrological probe for vdW heterostructures mechanical properties and promote the appearance of interfacial ferroelectric domains when two thin hBN crystals are marginally twisted.
Finally, we also started the development of a prototype for a unique experimental multiplatform for simultaneous dielectric and optical measurements that is expected to have great scientific impact and commercial potential in multiple fields of research, from physical sciences to chemistry and biology.
In conclusion, the results at the end of the action have gone well beyond the state of the art, providing new knowledge on topics of high interest for the society and new tools for the characterization of the nanoscale.

Diagram illustrating the use of scanning probe tools for the characterisation of nanoconfined liquid