title: Van der Waals pressure and its effect on trapped interlayer molecules.
abstract: Van der Waals assembly of two-dimensional crystals continue attract intense interest due to the prospect of designing novel materials with on-demand properties. One of the unique features of this technology is the possibility of trapping molecules between two-dimensional crystals. The trapped molecules are predicted to experience pressures as high as 1 GPa. Here we report measurements of this interfacial pressure by capturing pressure-sensitive molecules and studying their structural and conformational changes. Pressures of 1.2±0.3 GPa are found using Raman spectrometry for molecular layers of 1-nm in thickness. We further show that this pressure can induce chemical reactions, and several trapped salts are found to react with water at room temperature, leading to two-dimensional crystals of the corresponding oxides. This pressure and its effect should be taken into account in studies of van der Waals heterostructures and can also be exploited to modify materials confined at the atomic interfaces.
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: K S
authors.initials: KS
authors.lastname: Vasu
authors.affiliation: School of Materials, University of Manchester, Manchester M13 9PL, UK.
authors.forename: E
authors.initials: E
authors.lastname: Prestat
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: J
authors.initials: J
authors.lastname: Abraham
authors.affiliation: School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: J
authors.initials: J
authors.lastname: Dix
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Kashtiban
authors.affiliation: Department of Physics, Shahid Rajaee Teacher Training University, 16875-163, Lavizan, Tehran, Iran.
authors.forename: J
authors.initials: J
authors.lastname: Beheshtian
authors.affiliation: Department of Physics, University of Warwick, Coventry CV4 7AL, UK.
authors.forename: J
authors.initials: J
authors.lastname: Sloan
authors.affiliation: School of Chemical Engineering and Analytical Science, University of Manchester, Manchester M13 9PL, UK.
authors.forename: P
authors.initials: P
authors.lastname: Carbone
authors.affiliation: Department of Physics, Shahid Rajaee Teacher Training University, 16875-163, Lavizan, Tehran, Iran.
authors.forename: M
authors.initials: M
authors.lastname: Neek-Amal
authors.affiliation: School of Materials, University of Manchester, Manchester M13 9PL, UK.
authors.forename: S J
authors.initials: SJ
authors.lastname: Haigh
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: A K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: School of Physics and Astronomy, University of Manchester, Manchester M13 9PL, UK.
authors.forename: R R
authors.initials: RR
authors.lastname: Nair