Hybrid polysaccharide film infused with polyoxometalates for inkless printing and solar ultraviolet sensing

Inkless paper made from photochromic materials has garnered significant interest owing to its potential to reduce both ink and paper pollution during production. In this research, we synthesized a dual-material film (EC-PVP/PGMEA/PMoA) and conducted a detailed investigation of its photochromic response to visible light and its microstructural properties. Initially, the film appeared as a translucent yellow, but upon exposure to visible light, it shifted to blue with a maximum absorption peak of 2.04 a.u. The film returned to its stable yellow state either by heating at 100 °C for 1 h or by being kept in the dark at RT conditions for 20 days, aided by PGMEA. The film's hydrophobicity decreased, attributed to PEG, and its hydrophilicity was confirmed by a reduction in water contact angle from 69.9° to 37.8°. XPS and ESR analyses revealed a Mo⁵⁺ ratio of 0.42 and a signal at g = 2.017, indicating proton transfer and photo reductive interactions between PMoA particles and the EC-PVP/PGMEA matrix. This innovative study underscores the hybrid film's potential for applications in inkless printing and UV solar detection.