Investigation on the upconversion emission in 2D BiOBr:Yb(3+)/Ho(3+) nanosheets

As lanthanide doped upconverting host, two dimensional (2D) nanostructure materials have remarkable advantages compare with the bulk materials, but excellent 2D upconversion nanohost is still few up to date. In this work, Yb(3+)/Ho(3+) co-doped BiOBr nanosheets have been successfully prepared via a facile hydrothermal method, which were characterized by X-ray diffraction, transmission electron microscopy, Atomic Force Microscope, Raman spectra, Fourier transform infrared absorption and UC luminescence spectra. Under excitation at 980 nm, bright green UC emission centered at 550 nm accompanied with weak red (663 nm) and near infrared (NIR) UC emissions (760 nm) were observed. Power dependence studies revealed that NIR and red UC emissions were both dominated by a two and one-photon process due to saturation effects that is related to the special crystal structure of BiOBr nanosheets, and a different UC mechanism of NIR emission from Ho(3+) was proposed accordingly.