Reversible morphological transition between nano-rods to micro-flowers through micro-hexagonal crystals in a sonochemical synthesis based on a polyoxovanadate compound

We report ultra-sonication assisted morphological evolution in hexagonal macrocrystals of {V10O28} type polyoxometalate system [C5H11N]6[V10O28]·[CH3COOH]4·2H2O (1) as a function of sonication temperatures. Field emission scanning electron microscopy (FESEM) as well as transmission electron microscopy (TEM) studies reveal that at room temperature, sonication of macrocrystals results in the formation of spherical nanoparticles, that are transformed to nano-rods at the sonication temperature of 50 °C. The morphology is transformed from nano-rods to micro-flowers through hexagonal shaped microcrystals as the sonication temperature rose from 50 to 80 °C. It is observed that the hexagonal morphology of the original crystal is retained after a complete cycle (from 80 °C to complete evaporation of solvent) of morphological transitions. Compound 1 is unambiguously characterized by single crystal X-ray structure determination.