Tetraphenylethylene‐Equipped Graphene Quantum Dots Heterostructure With Enhanced Cathodic Photoelectrochemical Signal for Hydrogen Peroxide Detection in Plants

ABSTRACT Hydrogen peroxide (H 2 O 2 ) monitoring in plants is essential for elucidating stress signaling and related physiology. However, the performance of current detection methods is often compromised by the complex plant matrix. Photoelectrochemical (PEC) sensing utilizing p‐type semiconductors facilitates rapid electron transfer from the electrode interface to electron acceptors, resulting in a cathodic photocurrent and offering a notable anti‐interferent ability for H 2 O 2 detection. Herein, we report a novel tetraphenylethylene‐equipped graphene quantum dots (TEGQDs) heterostructure to construct cathodic PEC sensors for H 2 O 2 detection. By π – π stacking assembly of π ‐electron‐rich TPE molecules with p‐type GQDs, fast electron channels are established within the heterostructure, endowing the TEGQDs with an enhanced cathodic photocurrent signal. Moreover, in the presence of H 2 O 2 , the peroxidase‐like enzyme activity of TEGQDs inherited from GQDs catalyzes oxidation of 4‐chloro‐1‐naphthol to produce an insoluble precipitate, decreasing the photocurrent response. This strategy endows the PEC sensor with exceptional selectivity and a low detection limit of 70.2 nM for H 2 O 2 . Assisted by a minimally invasive microneedle extraction, this sensor is successfully applied to investigate H 2 O 2 fluctuations in tomato leaves subjected to various biotic ( Botrytis cinerea ) and abiotic (wounding, heat) stresses. This study presents a robust and versatile PEC sensor for monitoring plant health in agricultural management.