Effects of solvent and excitation power on ratiometric upconversion luminescence based temperature sensing using NaYF4:Yb3+,Er3+

Thermal sensing using the luminescence intensity ratio of the green Er3+ emissions is affected by the solvent and requires steady-state conditions during the excitation. It is important to keep the excitation power at a moderate level or short exposure times to avoid local heating of aqueous samples. The solvent also determines whether the red emission of Er3+ is excited via a two- or three-photon process.