Visible light-driven photoelectrochemical sensor based on CuPc/TiO nanotube arrays for ultrasensitive hexavalent chromium detection.

A visible light-driven photoelectrochemical (PEC) sensor based on copper phthalocyanine-sensitized TiO nanotube arrays (CuPc/TiO NTAs) was successfully fabricated and applied to the detection of hexavalent chromium (Cr(VI)) in aqueous environments. The CuPc/TiO NTAs were synthesized via a combination of electrochemical anodization followed by high-vacuum thermal evaporation deposition, providing precise control over the structural and optical properties of the material. Compared with pristine TiO NTAs, the introduction of CuPc not only enhanced visible-light harvesting and charge separation but also improved specific Cr(VI) adsorption, thereby significantly improving the sensitivity and selectivity for Cr(VI) detection. Under optimized conditions, the developed PEC sensor exhibited excellent analytical performance, including a broad linear detection range (0.01-80 µM) and a low detection limit of 0.0056 µM (S/N = 3). Moreover, the sensor displayed superior reproducibility with a maximum relative standard deviation of 6.1%, remarkable selectivity, and exceptional long-term stability. Practical feasibility was further demonstrated by successfully detecting Cr(VI) ions in environmental water samples (lake, river, and tap water), achieving satisfactory recoveries of 90%-116%. Overall, the CuPc/TiO NTA-based PEC sensor represents a robust, cost-effective, and highly promising tool for rapid, selective, and sensitive environmental monitoring of Cr(VI), providing new insights into advanced PEC sensor design and environmental remediation strategies.