Multicolor and white light upconversion luminescence in α-NiMoO4:Yb3+/Ln3+ (Ln = Tm, Ho, Tm/Ho) nanoparticles

•Synthesis of the α-NiMoO4:Yb3+/Ln3+ (LnTm, Ho, Tm/Ho) nanoparticles using the microwave hydrothermal method.•Generation of multicolor and white emissions by the samples under a 980 nm excitation.•An explanation of the photonic process, energy transfer mechanism, and CIE color chromaticity.•Cytotoxicity investigation of the phosphors in the bovine skeleton muscle cells via the MTT assays.