Reduced photon quenching in Ce doped NaYF4:Yb/Ho upconversion nanoparticles with

The use of red light or near-infrared radiation as a luminescent probe for in vivo bio imaging is crucial in order to restrict the strong absorption of short-wavelength light below 600 nm in tissue. It is demonstrated that the emission color of Yb/Ho codoped NaYF4 nanoparticles can be tuned from gre