White-light emission in Yb3+/Er3+/TM3+- and Yb3+/Er3+/Tm3+/Ho3+-doped alpha-NiMoO4 nanoparticles

Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-doped alpha-NiMoO4 nanoparticles were synthesized using a microwave hydrothermal method and studied for white-light emission under 980 nm laser diode excitation. White upconversion (UC) light was successfully obtained with the appropriate control of blue, green, and red emissions by successfully tuning the Er3+ and Ho3+ concentrations in Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-doped alpha-NiMoO4, respectively. In addition, the white color emission was shown by the CIE chromaticity coordinates of samples. The energy transfer mechanisms are explained in detail based on the emission spectra and pump power density-dependent UC luminescence intensity in rare earth (Yb3+/Er3+/Tm3+ and Yb3+/Er3+/Tm3+/Ho3+)-doped alpha-NiMoO4 nanoparticles. The results indicate that Yb3+/Er3+/Tm3+- and Yb3+/Er3+/Tm3+/Ho3+-doped alpha-NiMoO4 nanoparticles can be good candidates for white-light devices.