Lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals: Synthesis, characterization, and photocatalytic properties

Highlights: • Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) are synthesized by hydrothermal method. • Light absorption edge shows red shift with decreasing Ln{sup 3+} radius from Nd{sup 3+} to Yb{sup 3+}. • Ln{sub 2}Sn{sub 2}O{sub 7} shows increasing photocatalytic activity with the decease of Ln{sup 3+} radius. • Electronic configuration reaches 4f{sup 14} under light irradiation may decrease photocatalytic activity. • Hydroxyl radicals are detected to be the major reactive species. - Abstract: A series of lanthanide stannate pyrochlores Ln{sub 2}Sn{sub 2}O{sub 7} (Ln = Nd, Sm, Eu, Gd, Er, Yb) nanocrystals have been successfully synthesized via a facile hydrothermal route. With the decrease of Ln{sup 3+} radius, the light absorption edge of the as-prepared Ln{sub 2}Sn{sub 2}O{sub 7} shows a red shift from Nd{sup 3+} to Yb{sup 3+}. Their photocatalytic activities are found to be improved with the decrease of Ln{sup 3+} radius. However, the photocatalytic activity of Yb{sub 2}Sn{sub 2}O{sub 7} is a little lower than Er{sub 2}Sn{sub 2}O{sub 7}, although the Yb{sup 3+} radius is smaller than Er{sup 3+}, which may be attributed to the full-filled electronic configuration (4f{sup 14}) of surface Yb{sup 2+} intermediates (formed by Yb{sup 3+} trapping a photo-excited electron). The crystallite size and surface area play the most important role in determining the activities. Furthermore, hydroxyl radicals are detected to be the major reactive species during the photo-degradation process. Our findings provide insights in the fabrication of highly efficient stannate photocatalysts, thus enlarging the family of photocatalysts available.