A single heterojunction enables dual functionality: engineered ZrO2@CNT nanocomposites for visible-light pharmaceutical degradation and photodetection

Dual-functional ZrO2@CNT heterojunctions are designed and synthesized to achieve efficient light-induced charge separation for both environmental remediation and optoelectronics. Comprehensive structural characterization confirms a high-purity, crystalline heterostructure with intimate interfacial contact between monoclinic ZrO2 and carbon nanotubes (CNT), which is critical for synergistic functionality. The optimized nanocomposite degrades 96% of the antibiotic isoniazid within 60 min under visible light, with near-complete mineralization (95.3% total carbon content (TOC) removal), confirming true pollutant destruction to CO2, H2O, and inorganic ions. Mechanistic studies reveal pseudo-first-order kinetics dominated by hydroxyl radicals (•OH), enabled by suppressed electron–hole recombination at the intimately coupled monoclinic ZrO2/CNT interface. Simultaneously, the same heterostructure delivers high-performance visible-light photodetection at 635 nm (below the ZrO2 bandgap of 3.7 eV), achieving a responsivity of 6.06 × 10⁻1 A/W, specific detectivity of 7.11 × 106 Jones, and external quantum efficiency of 1.4 × 10⁻2. This strong sub-bandgap photoresponse arises from direct CNT absorption, defect-mediated transitions, and photoconductive gain amplification. The material exhibits excellent operational stability and recyclability over multiple cycles. By unifying efficient photocatalytic degradation of emerging contaminants with sensitive visible-light detection in a single, robust nanocomposite, this work establishes a new material platform for next-generation environmental monitoring and protection technologies.