Single-crystal micro/nanostructures and thin films of lamellar molybdenum oxide by solid-state pyrolysis of organometallic derivatives of a cyclotriphosphazene

The solid-state pyrolysis of organometallic derivatives of a cyclotriphosphazene is demonstrated to be a new, simple and versatile solid-state templating method for obtaining single-crystal micro- and nanocrystals of transition and valve metal oxides. The technique, when applied to Mo-containing organometallics N3P3[OC6H4CH2CN.Mo(CO)5]6 and N3P3[OC6H4CH2CN.Mo(CO)4 py]6, results in stand-alone and surface-deposited lamellar MoO3 single crystals, as determined by electron and atomic force microscopies and X-ray diffraction. The size and morphology of the resulting crystals can be tuned by the composition of the precursor. X-ray photoelectron and infrared spectroscopies indicate that the deposition of highly lamellar MoO3 directly on an oxidized (400 nm SiO2) surface or (100) single-crystal silicon surfaces yields a layered uniphasic single-crystal film formed by cluster diffusion on the surface during pyrolysis of the metal-carbonyl derivatives. For MoO3 in its layered form, this provides a new route to an important intercalation material for high energy density battery materials. - Graphical abstract: Lamellar MoO3 micro- and nanocrystals are prepared by pyrolysis of the organometallics N3P3[OC6H4CH2CN.Mo(CO)5]6 (I) and N3P3[OC6H4CH2CN.Mo(CO)4 py]6 (II), in air at 800 oC. The single-crystal products exhibit a high degree of turbostratic layering (see image). Deposition and subsequent pyrolysis of uniphasic MoO3 from the precursors is also possible on suitable substrates and supports.