Hybrid A-B-A type nanowires (NWs) with Ag 5Te 3-HgTe- Ag 5Te 3 composition have been created by the reaction of Hg 2+ with Ag 2Te NWs. The NW morphology of Ag 2Te is preserved upon reaction with minor changes and the two separate phases formed are spatially separated within the same NW. The reaction of Hg 2+ with Ag 2Te 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 Ag 5Te 3 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 Pb 2+, Cd 2+, and Zn 2+ whose reactivity towards Ag 2Te NWs is different from that of Hg 2+. These ions form a passivating Te oxide layer upon reaction with other metal ions. The mechanism of reactivity of Hg 2+ is explained on the basis of free energy of formation of the ionic solid. Phase transition of Hg 2+-reacted NWs occurs at a lower temperature than the parent (Ag 2Te NWs) and other metal ions-reacted Ag 2Te 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. © 2011 The Royal Society of Chemistry.