| Mar 06, 2025 |
An international research project has used nanotube compression to transform the underlying chemistry and physics of a compound, creating a promising new one-dimensional material.
(Nanowerk News) An international research project, led by The University of Warwick and University of Lille, has used carbon nanotube compression to transform the underlying chemistry and physics of a compound, creating a promising new one-dimensional material.
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In this study published in JACS (“Differential Packing of Cs2Mo6Br14 Cluster-Based Halide in Variable Diameter Carbon Nanotubes with Elimination and Polymerization to 1D [Mo2Br6]x Ising Model Structures by Steric Confinement”), a large cluster-based compound (Cs2Mo6Br14) underwent nanoconfinement in a series of carbon nanotubes, the smallest of which measured as small as ten Ångstroms (i.e., Å) or one billionth of a metre.
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With nanotubes this small, the inside of the tube measured smaller than the compounds themselves. Under extreme confinement, the compound became compressed to the point of breaking down (in a process called elimination), creating a new smaller compound [Mo2Br6]x, inside the tube.
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Dr. Jeremy Sloan, Reader in Electron Microscopy at Warwick and senior author of this paper, said: “This research is unique and important in two different respects. In the first instance, we see how confinement of an inorganic cluster-based material in narrow nanotubes causes that material, in a steric or confined structural limit, to eliminate or shed some of its chemicals to form a polymerised inorganic compound. Secondly, and serendipitously, the inorganic polymer has a 1D Ising-like structure, which are of great interest in statistical physics and in forming ferromagnetic arrays with potential utility in information storage at the atomic level.”
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| Nanotubes gradually compress the compounds until it eliminates into a new structure. (Image: University of Warwick)
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Remarkably, the physical properties of the new compound were also completely modified because of this confinement effect. The new smaller compounds are likely magnetic and arranged themselves into a linear polymer (linked) structure, which can be thought of as a compound ‘conga line’ within the tube.
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In the conga line of compounds, each compound can only interact with its two nearest neighbours, which means they act like row of bar magnets, either pointing magnetically up or down. If their neighbouring compound turns one way, the compound will be influenced to turn that way also, because of the magnetic pull.
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This arrangement can also be described as a 1D Ising model. (The Ising model (or Lenz–Ising model), named after the physicists Ernst Ising and Wilhelm Lenz, is a mathematical model of ferromagnetism in statistical mechanics. The model consists of discrete variables that represent magnetic dipole moments of atomic “spins” that can be in one of two states (+1 or −1). The spins are arranged in a graph, usually a lattice (where the local structure repeats periodically in all directions), allowing each spin to interact with its neighbours. Neighbouring spins that agree have a lower energy than those that disagree; the system tends to the lowest energy, but heat disturbs this tendency, thus creating the possibility of different structural phases. The model allows the identification of phase transitions as a simplified model of reality. The two-dimensional square-lattice Ising model is one of the simplest statistical models to show a phase transition.)
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Since each compound only exists in one of two states (up/down, on/off), and small changes can ripple through the system, this binary Ising-like structure lends itself to exciting quantum computing and molecular electronic applications.
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Dr. Sloan added: “Our work illustrates how confining nanomaterials inside small volumes profoundly modifies their structural chemistry, while also creating scientifically interesting, and potentially functional new nanoscale objects.”
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If nanoconfinement can fundamentally alter the behaviour of materials and lead to unexpected transformations, including gaining electrical and magnetic properties, it presents a promising synthetic route for nanomaterials with exciting properties.
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