MOF-templated hollow Pd/CdS@Co3S4 nanocages with synergistic Z-scheme/Schottky effects for photoelectrochemical biosensing of chlorpyrifos featuring exceptional dynamic range

Abstract

A novel ternary synergistic photoelectrochemical (PEC) probe is presented utilizing metal–organic framework (MOF)-templated Pd/CdS@Co₃S₄ nanocages for sensing chlorpyrifos (CPF) using chronoamperometry under an applied bias of − 65 mV with 465-nm LED illumination. Derived from ZIF-67 via in situ sulfidation, the hollow nanocage architecture integrated CdS nanoparticles with Co₃S₄ to form a direct Z-scheme heterojunction, while decorating Pd quantum dots (QDs) created a Schottky barrier, implementing a crucial dual charge-transfer enhancement strategy. Density functional theory (DFT) simulations confirmed a 0.36-eV Fermi level difference at heterojunction interface, verifying a forced built-in electric field. The optimized Pd/CdS@Co₃S₄ nanocomposite exhibited a remarkable 4.63-fold photocurrent amplification over its pristine Co₃S₄, establishing a high-intensity signal baseline essential for accommodating wide-range concentration-dependent signal attenuation. Acetylcholinesterase (AChE)-immobilized biosensor quantified CPF via inhibition-triggered competitive electron consumption to attenuate photocurrent. The sensor demonstrated exceptional performance for CPF detection, most notably featuring a linear dynamic range spanning four orders of magnitude (0.1 ~ 2000 ng·mL⁻¹). Furthermore, it achieved a low detection limit (0.05 ng·mL⁻¹, S/N = 3), outstanding specificity against interfering species, excellent long-term stability, and reliable accuracy in complex real water samples (96.5 ~ 104.5%). This study proposes dual charge-transfer enhancement strategy and hollow architecture, addressing the broad-concentration-range in environmental pesticide detection with good sensitivity and adaptability to real-world matrices.

Graphical Abstract