AuxAgy@ZrO2 core–shell nanoparticles: synthesis, characterization, reactivity and optical limiting

AuxAgy@ZrO2 redispersible core–shell nanoparticles were prepared by a single step synthesis using the dimethyl formamide (DMF) reduction procedure. The material is stable for extended periods of time. The core–shell alloy nanoparticles were characterized by UV–vis spectroscopy, transmission electron microscopy, X-ray diffraction, differential scanning calorimetry and cyclic voltammetry. The as prepared particles are nanocrystalline in nature, but they give well-defined diffraction patterns upon heating to 100 °C for 8 h. The average diameter of the core is ∼35 nm and typical shell thickness is 2–3 nm. The materials show interesting reactivity with halocarbons as in the case of naked metal nanoparticles, which vary with the composition of the alloy. Our experiments show that oxide-protected alloy nanoparticles are excellent optical limiters in the nanosecond regime. Optical nonlinearity of these systems has been investigated in detail and a qualitative model has been proposed. To the best of our knowledge, this is the first report of nanoparticles having a true alloy core and an oxide shell.