Enhanced Chemiluminescence Induced by Natural Light-Driven MIL-100(Fe)/TiO₂ for Dopamine Detection

Luminol-based chemiluminescence (CL) systems, as a powerful tool for bioanalysis, are limited owing to their weak CL intensity and self-decomposition of the classic oxidant H₂O₂. Herein, we introduced a new luminol CL enhancer, the natural light-driven photocatalyst MIL-100(Fe)/TiO₂, for the selective determination of dopamine (DA). By employing MIL-100(Fe)/TiO₂ for the first time as an efficient enhancer, the MIL-100(Fe)/TiO₂-luminol CL intensity was 100 times higher than that of the classical H₂O₂-luminol system. The CL spectrum, UV-vis absorption spectroscopy, radical scavenger experiments, and electron spin resonance spectroscopy were utilized to investigate the possible CL mechanism of the MIL-100(Fe)/TiO₂-luminol system. All of the results indicated that MIL-100(Fe)/TiO₂ can generate reactive oxygen species under mild natural light, which could react rapidly with the luminol anion radical and result in direct CL emission. The sensitive plate for DA was developed based on its inhibiting effect on CL intensity, and the linear range between CL intensity and DA concentration was 100 nM-1000 μM with a detection limit of 16.7 μM (S/N = 3). This study successfully achieved a stable reactant that can directly trigger the CL of luminol without the need for additional oxidizing agents under mild natural light and offers new possibilities for photoinduced amplification technology.