Comment on “Bi-functional Li 2 B 12 H 12 for energy storage and conversion applications: solid-state electrolyte and luminescent down-conversion dye” by J. A. Teprovich Jr, H. Colón-Mercado, A. L. Washington II, P. A. Ward, S. Greenway, D. M. Missimer, H. Hartman, J. Velten, J. H. Christian and R. Zidan, J. Mater. Chem. A , 2015, 3 , 22853

The photoluminescent properties of selected metal closo -boranes have been assessed. Group 3 elements Sc, Y, and La as well as Li, Na, and Eu-based B 10 H 10 2− and B 12 H 12 2− compounds displayed photoluminescence in the ultraviolet (emission λ max ≈ 350 nm) that was not visible to the human eye, in contrast to previous reports. We attribute these earlier results to arachno -borane impurities, which are more readily observed due to their longer wavelength emission spectra.