Facile synthesis of GdBO3 spindle assemblies and microdisks as versatile host matrices for lanthanide doping

Rare-earth borates are important luminescent materials owing to their high damage threshold, high stability and low toxicity. Although some conventional ReBO3 nano-/micro- structures have been developed previously, the synthesis of uniform and ordered assemblies of GdBO3 nanocrystals still remains challenging. Herein we report a facile method for synthesizing GdBO3 assemblies with a spindle-like profile which consist of small GdBO3 nanorods. Investigation of the formation mechanism suggests that these interesting nanostructures are formed accompanied with a spontaneous pH change in solution during synthesis. Single-crystal GdBO3 microdisks have been also obtained by aging these assemblies in solution through Ostwald ripening. The GdBO3 assemblies and microdisks can display various emissions through down-shifting, up-conversion or down-conversion processes when doped with different lanthanide ions. It is anticipated that the developed nano-/micro-GdBO3 crystals not only possess potential in traditional luminescence applications but could also be implemented in biomedical engineering and the solar cell industry.