Halide-mediated electrochemical modification of copper phthalocyanine for humidity sensing applications†

This work presents a one-step electrochemical halogenation and exfoliation of copper phthalocyanine (CuPc), producing thin-layered halogenated CuPc with tunable physicochemical properties. By incorporating halogen into the CuPc structure, the copper centers acquire an enhanced positive charge, which significantly improves their affinity for water molecules. Coupled with the strong water-interactive properties of polyvinylpyrrolidone, this halogenation-driven modification creates a synergistic effect, resulting in markedly increased sensitivity and responsiveness for humidity sensing applications. As a proof of concept, chlorinated CuPc integrated with polyvinylpyrrolidone on flexible interdigitated electrodes achieves high sensitivity (1.2 × 10⁴%), excellent reproducibility (<5% RSD), and a broad dynamic range (11–94%RH), firmly establishing its potential as a high-performance humidity sensor.