Volumetric flame synthesis of well-defined molybdenum oxide nanocrystals

Abstract

Well-defined faceted inorganic Mo oxide nanocrystals are synthesized in the gasphase using a solid-fed-precursor flame synthesis method. The solid crystals haverectangular cross-section with characteristic size of 10–20 nm and with lengths rangingfrom 50 nm to a few hundred nanometres. A 1 mm diameter high purity Mo probeintroduced in the oxygen-rich part of the flame serves as the material source. Acombination of the strong temperature gradient and varying chemical speciesconcentrations within the flame volume provides the ideal conditions for the rapidand direct formation of these unique nanocrystals. Oxidation and evaporation ofMoO3 in the oxygen-rich zone are followed by reduction toMoO2 in the lower temperature, more fuel-rich zone. TheMoO3 vapours formed are pushed in the direction of the gas flow and transformed into maturewell-defined convex polyhedron nanocrystals bounded with six faces resembling rectangularparallelepipeds.