Switch-type photoelectrochemical aptasensor for microplastics and nanoplastics detection based on two-dimensional organic−inorganic heterojunction

Microplastics and nanoplastics (MNPs) as emerging pollutants present substantial risks to both the environment and human health. Developing highly sensitive methods to rapidly identify and detect low concentrations of MNPs in complex systems remains a considerable challenge. Here, an "off-on" switch-type photoelectrochemical (PEC) aptasensor was employed for the sensitive detection of polyvinyl chloride (PVC) and polystyrene (PS) MNPs. This PEC aptasensor was based on a two-dimensional organic-inorganic Z-scheme heterojunction and utilized an acetylferrocene-modified aptamer (Apt-AcFc) as PEC recognition and quencher probes. In general, combining Apt-AcFc with the photoelectrode efficiently quenches the photocurrent, transitioning it to the 'off' state. Conversely, the presence of MNPs greatly increases the photocurrent because the MNPs were specifically recognized by Apt-AcFc, causing Apt-AcFc detaching from the photoelectrode and transition to the 'on' state. The developed PEC aptasensor was employed for the detection of MNPs released from food packaging materials. Although the aptasensor displayed distinct sensitivities toward PVC and PS, it demonstrated a consistent linear dynamic range of 1-200 μg mL and a low detection limit of 0.1 μg mL. This switching-type PEC aptasensor provides a rapid, sensitive, and reliable analytical platform for the determination of MNPs in food and environmental matrices.