Higher alkali metal polyphosphides, MP15 (M = Li, Na, K) contain infinite tubular phosphorus anions that are reminiscent of the structure of violet phosphorus, with the alkali metal ions situated between the tubes. These materials have been synthesized by chemical vapor transport reactions that lead to ruby-red needle-shaped crystals. An examination of the crystal packing reveals that alkali metal ions are missing in every other (002) plane, in which case the phosphorus tubes interact with each other only weakly through van der Waals contacts. Hence, these materials should render themselves to mechanical delamination along those crystal planes. In this contribution we confirm that KP15 can be mechanically delaminated to produce nanowires of varying sizes, as confirmed by optical, scanning probe, and electron microscopy methods. The use of Raman spectroscopy showed that the tubular structure remains intact in the nanowires for all values of thickness examined. The photoluminescence peak, however, is shifted to higher energies as the nanowires become thinner, thus providing the evidence for the thickness dependence of the material’s electronic band gap. Thus, MP15 polyphosphides represent interest for the development of low-dimensional semiconducting devices.

Size-dependent properties of polyphosphide nanowires

256th National Meeting (2018)

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