A new probe,2exhibit quenching with Co²⁺(∼80% at 634 nm) while2·Co²⁺ensemble exhibit enhancement with NO₃⁻(∼82% at 632.5 nm). On–Off–On behavior of2(Co²⁺and NO₃⁻ions) the function of a sequential XNOR gate and can be utilized in live cell imaging.

Ti₃C₂-MXene material, known for its strong electronic conductivity and optical properties, has emerged as a promising alternative to noble metals as a cocatalyst for the development of efficient photocatalysts used in environmental cleanup. In this study, we investigated the photodegradation of crystal-violet (CV) dye when exposed to UV light using a newly developed photocatalyst known as Ti₃C₂-MXene/NiO nanocomposite-decorated CsPbI₃ perovskite, which was synthesized through a hydrothermal method. Our research investigation into the structural, morphological, and optical characteristics of the Ti₃C₂-MXene/NiO/CsPbI₃ composite using techniques such as FTIR, XRD, TEM, SEM–EDS mapping, XPS, UV–Vis, and PL spectroscopy. The photocatalytic efficacy of the Ti₃C₂-MXene/NiO/CsPbI₃ composite was assessed by evaluating its ability to degrade CV dye in an aqueous solution under UV-light irradiation. Remarkably, the Ti₃C₂-MXene/NiO/CsPbI₃ composite displayed a significant improvement in both the degradation rate and stability of CV dye when compared to the Ti₃C₂-MXene/NiO nanocomposite and CsPbI₃ perovskite materials. Furthermore, the UV–visible absorption spectrum of the Ti₃C₂-MXene/NiO/CsPbI₃ composite demonstrated a reduced band gap of 2.41 eV, which is lower than that of Ti₃C₂-MXene/NiO (3.10 eV) and Ti₃C₂-MXene (1.60 eV). In practical terms, the Ti₃C₂-MXene/NiO/CsPbI₃ composite achieved an impressive 92.8% degradation of CV dye within 90 min of UV light exposure. We also confirmed the significant role of photogenerated holes and radicals in the CV dye removal process through radical scavenger trapping experiments. Based on our findings, we proposed a plausible photocatalytic mechanism for the Ti₃C₂-MXene/NiO/CsPbI₃ composite. This research may open up new avenues for the development of cost-effective and high-performance MXene-based perovskite photocatalysts, utilizing abundant and sustainable materials for environmental remediation.