The twists and turns in 1D: Developing chemical strategies towards uniqueelectronic landscapes in atomically precise one-dimensional solids
Dr. Maxx Arguilla, Assistant Professor, UC Irvine Department of Chemistry
The discovery of complex phenomena and strongly correlated behavior in solids has incessantly relied upon the creation of stable low-dimensional crystals approaching the atomic limit. Whereas 2D van der Waals (vdW) materials have gained widespread interest, very little has been known about the chemistry and physics of their more confined 1D counterparts. These lower dimensional structures could be thought of as freestanding “edge states” and could bridge the knowledge gap towards understanding physical states in atomically precise 2D and 0D solids. To this end, I will present our efforts in elucidating the distinct chemical interactions which define the structure, dimensionality, assembly, and physical properties of crystals comprised of vdW-bound sub-nanometer-thick 1D chains. First, by gaining chemical influence over inter-chain interactions via a bottom-up vapor growth route, we establish the synthetic design rules to access dimensionally resolved nanostructures with various thicknesses ranging from 1D nanowire bundles to quasi-2D nanoribbons and nanosheets, all based on the same quasi-1D vdW chain building block. I will talk about how precise synthetic control over the structure, dimensionality, and size of the resulting nanostructures led to our discovery of optical signatures that suggest the elusive indirect-to-direct band gap crossover in ultrathin nanowires derived from the Sb2S3 quasi-1D vdW model phase.
Furthermore, I will describe how our findings generally translate to direct the assembly of other 1D and q-1D vdW solids from bottom-up. Second, I will present a distinct class of exfoliable 1D vdW solids that crystallize as well-defined atomic-scale helical structures. I will describe how atomic level control of the local coordination environment along the covalent chain direction in these lattices induces helical aperiodicity and the rare Boerdijk-Coxeter motif from a periodic tetrahelix. Owing to the intrinsic non-centrosymmetry of aperiodic helices and the vdW interactions that hold them together, I will discuss how these tetrahelices exhibit visible range second harmonic generation in freestanding bulk and nanoscale crystals. Through these convergent efforts, we define the synthetic and materials design rules that dictate directed synthesis, complex atomic scale ordering, and anisotropic physical properties of these classes of emergent 1D vdW-derived materials.