Additive-Mediated Splitting of Lanthanide Orthovanadate Nanocrystals in Water: Morphological Evolution from Rods to Sheaves and to Spherulites

Ethylenediaminetetraacetic acid (EDTA) is shown to mediate the splitting of LnVO(4) (Ln = Ce and Nd) nanocrystals from rods to sheaves and to spherulites under hydrothermal conditions with remarkable controllability and uniformity. The roles of EDTA are thought to be to (1) chelate the Ln(3+) ions in solution, thus decreasing the nanocrystal nucleation rate but increasing the growth rate, and (2) interfere with the nanocrystal growth by capping the nanocrystal surfaces. Upconverted avalanche luminescence from LnVO(4) nanoplates, nanowires, and straw-nanosheaves has been demonstrated and compared. We found that the LnVO(4) strawsheaves have a relatively more efficient upconversion due to the smaller avalanche excitation threshold caused by the strong cross-relaxation between the bundled nanorods in the sheaves.