Impact of luminescent-ion doping on the crystallographic and photo-physical properties of the CaMoO₄ nanoparticles

Luminescent lanthanide (Ln³⁺ = Pr, Nd, Sm, Eu, and Tb)-ions doped calcium molybdate(CaMoO₄) nanoparticles(NPs) were prepared by the polyol wet-chemical route. X-ray diffraction (XRD) pattern of all samples showed the formation of a single-phase scheelite type tetragonal structure with an average crystalline size over 21.6–33.4 nm. Thermal stability was evaluated to study the surface-anchored functional groups by weight loss measurement. Fourier transform infrared (FTIR) spectra were recorded to identify the adsorbed functional groups. Aqueous dispersibility and colloidal stability were recorded with the help of the UV/visible absorption spectra. These nanocrystals formed semi-transparent colloidal solutions after being evenly disseminated in aqueous media. The doping of the luminescent ions significantly affects the crystal structure and photoluminescence (PL) properties of the CaMoO₄:Ln³⁺ NPs. In a comparative analysis of the absorption spectra, bandgap, Raman-active modes, and luminescent properties, they were greatly influenced by altering the dopant ion due to the variation in the atomic radius of the element. The doping of smaller atomic radius Ln³⁺-ions distorts the unit cell, and, subsequently, bond angle/length alters the symmetry of the host crystal. The distorted crystal lattice affects the crystalline, size, lattice parameter, band gap values, Raman active vibrational modes, and luminescent efficiency. The distorted crystal structure of the host lattices facilitates the movement of the oxygen vacancies through charge transfer, resulting in efficiently suppressed emission efficiency. Graphical abstract[Figure not available: see fulltext.].