Painting, reading, and erasing processes of the RTPP ink. (a) Controllable RTPP emission process of M1-acid-0.3 mg PVA ink on a substrate. (b) Sensitive anticounterfeiting on a postcard after turning off 254 nm light. (c) Comparison of the ink emission observed from five different paper substrates. (d) Photos of ink-brushed leaf pattern on glazed printing paper, showing temperature-dependent changes between room temperature (RT) and 65°C for 50 times. Bright blue fluorescence emits when turning on the 254 nm UV lamp, and cobalt phosphorescence emission is observed when turning off the 254 nm UV lamp. (e) A hand-painted lotus flower pattern with M1-acid-0.3 mg PVA ink showing cobalt phosphorescence emission after heating treatment (65°C) and turning of the UV light.