The synthesis and the spectroscopy of upconverting nanocolloidal solutions have recently generated considerable interest due to their potential application as biolevels and in biological assays. This paper reports the synthesis of lanthanides doped transparent colloidal solution via pulsed laser ablation (PLA) which is highly fluorescing. Er 3+ , Yb 3+ co-doped Gd 2 O 3 phosphor has been laser ablated to synthesize the colloidal solution in triply distilled water. Spherical shaped nanoparticles of the average diameter in the range of 8–26nm have been synthesized and characterized. Efficient multicolor upconversion (UC) emission has been observed and possible UC mechanism has been suggested. This approach will provide a method to synthesize highly UC efficient, non-agglomerated, pure transparent nanocolloidal solution for biological applications from already reported efficient phosphors.