Sensitive determination of chromium (VI) based on the inner filter effect of upconversion luminescent nanoparticles (NaYF4:Yb3+, Er3+)

► Upconversion NaYF4:Yb3+, Er3+ (λem=551 nm, λex=980 nm) were synthesized. ► NaYF4:Yb3+, Er3+ nanoparticles were used as fluorescence probe. ► The chelate generated by the reaction between DPC and Cr(VI) was used as absorbent. ► A new inner filter effect method was developed for determination chromium (VI).