Slow release realized in 40 min? Assembly of lanthanide hydroxycarbonates and oxycarbonates based on multiple irradiations

It has been well documented that urea would be slowly hydrolyzed to produce OH− and the reaction equilibrium requires relatively long times. Sometimes the samples have been achieved under high temperature (such as hydrothermal method). Here we describe systematic preparation of lanthanide hydroxycarbonate series through a facile and effective route (supersonic and microwave co-assistance) at 80 °C in less than 40 min. Product formation can be observed directly by the naked eye. Synthetic conditions were identical for all tested lanthanide elements, and corresponding nano- or micro-scale materials with different structures were obtained. A three-stage-effect was observed in crystalline phases and morphologies. More importantly, the intensive red and green emissions from europium and terbium oxycarbonates, respectively, were observed under relatively long wavelength excitations (365 or 394 nm).