The physical properties of matter change dramatically as atoms assemble into extended solids. Tracing the evolution of these properties as a function of material scale presents formidable challenges. Fortunately, low-dimensional materials can provide a vital link between these extremes of scale if their size, shape, and structure can be finely controlled. To do so, we have developed strategies for controlled crystallization of low-dimensional materials and have identified that even subtle tuning of their dimensionality and morphology yields substantial property changes. Notably, we can manipulate precisely the dimensionality of transition-metal dichalcogenide crystals by growing these model 2D materials on specially functionalized surfaces. The resulting 1D crystals emit light whose energy and profile show an unexpected progression as a function of crystal size. Expanding the scope of our methodologies, we also demonstrate the synthesis of 2D metal-organic frameworks. A reversible 1D-to-2D phase switching can be induced in these molecular frameworks with concomitant and substantial change in electronic transport. Our efforts underscore the importance of rational synthesis in the design of low-dimensional materials that link material lengthscales and advance the fields of optics, electronics, energy conversion, and quantum sensing.
Speaker: Thomas Kempa, Johns Hopkins Univ.
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