ZnO/ZIF-8@Au nanoarchitectures with nanoconfinement-enhanced plasmonic coupling for ultrasensitive photoelectrochemical detection of malondialdehyde.

Background

Malondialdehyde (MDA) is a pivotal oxidative stress biomarker implicated in cardiovascular diseases, neurodegeneration, and cancer; however, its trace quantification in complex biological matrices remains analytically daunting. Photoelectrochemical (PEC) sensing offers inherently low background noise and exceptional sensitivity for trace bioanalysis. Nevertheless, efficiently translating molecular recognition into amplified PEC signals remains a challenge.

Results

We report a nanoconfinement-mediated PEC interface that integrates covalent molecular conjugation with plasmonic amplification within a crystalline matrix scaffold. Within this nanoconfined environment, localized Au nanoparticles serve as plasmonic amplifiers that anchor 4-aminothiophenol (4-ATP) receptors. Upon MDA recognition, the optimized sensor exhibits dual linear detection ranges spanning 0.001 to 1.0 nmol L-1 (R12 = 0.9928) and 1.0 to 1000 nmol L-1 (R22 = 0.9992), yielding an ultralow detection limit of 0.3 pmol L-1.

Significance

The confined Schiff-base reaction between 4-ATP and MDA generates an interfacial reaction product, leading to a new absorption band at approximately 450 nm and modulation of the Au LSPR band. This change is mainly attributed to the altered local dielectric environment around Au NPs. Wavelength-dependent operando transient photovoltage spectroscopy (TPV) provides mechanistic evidence that plasmon-driven hot-carrier injection augments PEC signal output. Overall, this work establishes an interface-engineering paradigm that integrates molecular conjugation with plasmonic coupling, offering a promising blueprint for the PEC detection of small-molecule biomarkers.