Lead monoxide (beta-PbO) nanowires with extreme aspect ratio by vapour phase growth

Metal-oxides and their nanostructures are today widely investigated because of their multiple functional properties and possible application in different fields. In this context, lead oxides are not yet completely explored and their nanostructures are rarely reported in literature. Part of this lack may be probably ascribed to the complexity of Pb-O thermodynamic system [1], in which several stoichiometry (PbO, PbO?, Pb?O?, Pb??O??, Pb??O??, etc.) and phase are present. Among these, lead monoxide (PbO), which is a promising high-Z material for radiation detection, is a good example: it exists in two different forms, i.e. tetragonal (?-PbO, red PbO, Litharge) and orthorhombic (?-PbO, yellow PbO, Massicot) phases, and the complexity of stoichiometry and phase strong limits the growth of this material in form of single crystal nanostructures. Aim of this work has been the investigation of synthesis approaches to obtain PbO nanostructures. As solution growth methods resulted to be strongly affected by a poor stoichiometric control, vapour phase growth has been then exploited. Optimal results have been found by vapor approach evaporating Pb metal source in a O2 low pressure atmosphere. In particular nanowires, or better "nanoribbons", of ?-PbO with an extreme length-to-thickness aspect ratio (10000:1) have been obtained in a reproducible way.