In situ monitoring of crystal growth and dissolution of oriented layered double-hydroxide crystals immobilized on silicon

Layered double-hydroxide (LDH) minerals have recently attracted attention through their potential industrial application as fillers in mineral-polymer nanocomposite materials and, separately, as solid base catalysts to promote a range of reactions in an environmentally sound way. Little research has been undertaken on the crystal growth mechanism of LDHs using in situ methods. Recently, advances have been made in the controlled deposition and immobilisation of nanometre-sized LDH crystals onto a silicon substrate with preferred orientation. In this work we present initial studies using atomic force microscopy to image in real time immobilised LDH crystals during stages of hydration, growth and dissolution. The various stages were recorded by adjusting the reactant concentrations of the surrounding aqueous solution, allowing crystal dynamics to be visualised. Under certain conditions preferred stability of certain-sized LDH crystals relative to others was observed, indicating the operation of an Ostwald ripening process in samples containing a heterogeneous distribution of crystallite sizes.