On-demand green/red light-responsive self-doped SnO₂ nanoparticles for single/multi-color transitioning fabrics

Semiconductor/redox-based dual light-induced color switching systems (LCSs) with a visible light response at different wavelengths are highly sought after for efficient redox reactions. In this work, Sn²⁺ self-doped SnO₂ has been designed as nanophotocatalysts for preparing visible light-responsive inks/fabrics with single/multi-color abilities. The self-doping of SnO₂ nanoparticles results in the formation of oxygen vacancies due to charge compensation effects leading to electron-driven photoreduction and photooxidation of LSC inks. By mixing SnO_2-x nanoparticles dispersions with specific redox-sensitive dyes can lead to the creation of well-designed sets of visible light-responsive semiconductor-driven LCS systems with both single-color (RGB) and multi-color (violet and green) changes. The exposure of LCS inks to green (550 nm) light culminates in the rapid photoreduction of the inks to decolorized state, while red (660 nm) light initiates the photooxidation in air. The combination of the LCS inks with -OH-rich polymers can be coated on the hydrophobic surface of the layered fabric to produce photo-responsive fabrics with single/multi-color response. The interaction of green light with the semiconductor-driven LCS systems allows the remote photo-printing of different images/letters on the LCS fabrics. Spontaneous erasure can be achieved by red light with high stability and repeatability (>35 cycles). The research in this paper provides new perspectives and insights for the development of new color-changing materials with potential applications as light-activated sensors and display units.