Additional active Raman modes in α-PbO nanoplates

In this work we report the structural and morphological properties of α-PbO nanoplates obtained by high energy ball milling from commercial PbO powder. The high energy ball milling process induces a PbO crystalline phase transfomation from initial massicot (β-PbO) to litharge (α-PbO) after 5 h. The PbO nanoplates have litharge crystalline phase and thickness between 20-30 nm. The Raman spectrum of the α-PbO nanoplates displays the bands related to bulk PbO and two additional bands at frequencies 464 and 530 cm ^-1, which were associated to size effects in the nanoplates. Density functional theory calculations of the vibration properties of small α-PbO clusters predicted vibration modes at frequencies which agree with the experimental results.