In this work, NaYF₄:Eu@TiO₂:Er nanomaterial is synthesized via sol–gel method. Various characterization techniques such as FESEM, HRTEM, XRD, EDS FTIR and XPS confirmed the successful formation of NaYF₄:Eu@TiO₂:Er nanoparticles. The average particle size is found to be 15 nm. Also, UV–Vis–IR and PL spectrometry verified the biluminescent properties of the synthesized material. It is then investigated as biluminescent security ink to be used for anti-counterfeiting applications. The results showed that the designed biluminescent security ink exhibits strong yellow and purple emission under 275 nm and 325 nm excitations, respectively. A written material was kept for 3 months under hot (40 °C) and humid (85%) environment and the obtained results were identical without any deterioration in their luminescence intensities even after such a prolonged time. Moreover, this written material also showed stability under the exposure of different chemical solvents (ethanol, glycerol and acetone).