Hybrid A-B-A type nanowires through cation exchange

Abstract

Hybrid A-B-A type nanowires (NWs) with Ag₅Te₃-HgTe-Ag₅Te₃ composition have been created by the reaction of Hg²⁺ with Ag₂Te NWs. The NW morphology of Ag₂Te is preserved upon reaction with minor changes and the two separate phases formed are spatially separated within the same NW. The reaction of Hg²⁺ with Ag₂Te NWs was monitored at different concentrations and the reactivity was attributed to cationic exchange depending on solubility products. Hybrid NWs were formed by partial cation exchange only at low concentrations (below 50 ppm) resulting in Ag₅Te₃ and HgTe within the same NW. However, at high concentrations (above 100 ppm), the HgTe phase alone was formed. These studies have been extended to other metal ions such as Pb²⁺, Cd²⁺, and Zn²⁺ whose reactivity towards Ag₂Te NWs is different from that of Hg²⁺. These ions form a passivating Te oxide layer upon reaction with other metal ions. The mechanism of reactivity of Hg²⁺ is explained on the basis of free energy of formation of the ionic solid. Phase transition of Hg²⁺-reacted NWs occurs at a lower temperature than the parent (Ag₂Te NWs) and other metal ions-reacted Ag₂Te NWs. Details of the process were elucidated using microscopic and spectroscopic investigations. The physical and chemical properties of the individual components within a NW are expected to provide a novel functionality to the metal chalcogenide systems.