Abstract <p>A new Tb³⁺/Ho³⁺ co-doped with GdVO₄, vanadates without standing luminous characteristics that exhibit both up-conversion (UC) and down-conversion (DC) prepared through polyol synthesis which shows the applications in degradation studies helps for water purification. Although the average crystallitesizes in the samples lightly differ, X-ray diffraction patterns verify that a pure phase formed in the samples produced using polyol technique. Scanning electron microscopy (SEM) is used to measure the grain sizes, and it demonstrates that when the calcination temperature rises, the grain size increases. The bandgap of the samples is about 2.25 eV, which is deduced by Tau’s plot of UV Vis absorption spectra. The photoluminescence spectra shown green emissions from Ho³⁺ at about 540 nm when exposed to UV light, which corresponded to the ⁵S₂→⁵I₈ transition, while Tb³⁺ it shows about 545 nm when exposed to UV light, which corresponds to the ⁵D₄→⁷F₅ transition. Because of their variable emission properties, Ho³⁺ and Tb³⁺ are suitable for photodegradation technologies and lifespan of the lanthanide ions are with 6.94 m-sec.</p>