Applied anti-counterfeiting with strontium molybdate up-conversion phosphor synthesized via co-precipitation at low sintering temperature

The precursor prepared by the co-precipitation method was sintered at 600°C to synthesize crystalline SrMoO₄ powder. In this study, ytterbium and erbium rare-earth ions were doped to synthesize an up-conversion phosphor. The synthesized SrMoO₄:(Er³⁺)/(Yb³⁺) phosphor showed a strong green light emission at 530 and 551 nm when excited at 980 nm. The synthesized phosphor exhibited a change in luminescence intensity based on the amount of Er doped and showed strong luminescence as the laser pump power increased. Also, as the temperature increased, the luminescence intensity changed. This is thought to be due to the two-photon process as a result of the excited state absorption and energy transfer processes. To use the SrMoO₄:(Er³⁺)/(Yb³⁺) phosphor with these characteristics for anti-counterfeiting, the ink prepared by mixing it with PVP 10 wt% ethanol solution was applied to banknotes and artwork. Although it was impossible to confirm with the naked eye, green light emission could be confirmed when excited at 980 nm. In addition, the composite made by mixing with polydimethylsiloxane showed a change in luminescence intensity based on the laser pump power and temperature change. (author)