Tunable states of interlayer cations in two-dimensional materials

Abstract

Structural response of a highly viscous aluminoborosilicate melt to isotropic and anisotropic compressionsThe local state of cations inside the Å ngstrom-scale interlayer spaces is one of the controlling factors for designing sophisticated two-dimensional (2D) materials consisting of 2D nanosheets. In the present work, the molecular mechanism on how the interlayer cation states are induced by the local structures of the 2D nanosheets is highlighted. For this purpose, the local states of Na cations in inorganic 2D materials, in which the compositional fluctuations of a few percent are introduced in the tetrahedral and octahedral units of the 2D nanosheets, were systematically studied by means of 23 Na magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) and 23 Na multiple-quantum MAS (MQMAS) NMR spectroscopy. In contrast with an uniform distribution of Na cations expected so far, various well-defined cation states sensitive to the local structures of the 2D nanosheets were identified. The tunability of the interlayer cation states along with the local structure of the 2D nanosheets, as the smallest structural unit of the 2D material, is discussed. V C 2014 AIP Publishing LLC. [http://dx.

Long-term self-assembly of inorganic layered materials influenced by the local states of the interlayer cations

“…The states of interlayer cation induced by the local structure of the 2D nanosheets in these smectites were studied by solid-state 23 Na NMR spectroscopy in our former work. 12 Basically, the O and Si atoms are located at the vertices and the central site of each tetrahedron, respectively. The vertices of the octahedra are occupied by O atoms and OH groups, whereas metallic elements, such as Mg and Li atoms, occupy the central sites.…”

“…In our former work, 12 the relationship between the interlayer cation states and the local structure of the 2D nanosheets was investigated by solid-state 23 Na nuclear magnetic resonance (NMR) spectroscopy for three kinds of smectites: saponite, stevensite, and hectorite, in which minor compositional fluctuations were introduced into the 2D nanosheets. Various well-defined cation states, susceptible to the local structure of the 2D nanosheets, were identified in the interlayer spaces.…”

Carbon dioxide adsorption in open nanospaces formed by overlap of saponite clay nanosheets

“…This results in the formation of nanoscale open spaces (see Fig. 1b), which have been identified by positronium (Ps) annihilation spectroscopy together with molecular dynamics simulation as is detailed later [15][16][17] . Naturally, there exist local molecular sites in the interior of above open spaces such as nanosheet edges that are chemically active owing to the presence of unpaired electrons at ionically bound octahedron 18 .…”

“…The relative intensity of large open space I 2 for the Cs-type sample is~25%, much higher than that of the Na-type sample, though the intensities I 1 of small open spaces at 5% are similar to each other. The high intensity I 2 for the Cs-type sample indicating the large amount of 9 Å open space is resultant from insufficient self-assembly toward densification, which originates from interlayer Cs cations with low hydration degree 16,17 . Figure 2 shows the 133 Cs MAS NMR spectra obtained for the Cs-type saponite before (black curve) and after CO 2 loading (red curve), and their difference spectrum (blue curve).…”

Instantaneous Ex Situ Mineral Carbonation Relevant to Alkali Metals in Clay Nanoparticles

“…Radioactive Cs released from a nuclear power plant migrates through the soil environment together with groundwater in a geochemically complex manner. − It has been reported that the radioactivity of 137 Cs in groundwater sampled in the area ∼35 km northwest of the Fukushima Dai-ichi Nuclear Power Plant ranges from 0.0025 to 0.038 Bq L –1 in 2011–2013 . It is known that the concentration of 137 Cs in the soil environment is influenced by a number of environmental factors such as heavy rains caused by Typhoon Roke and geological conditions .…”