Molecular Structural Transformation from the D–A to D–D’ of an AIEgen for the Highly Sensitive Detection of Hydrogen Peroxide in Exhaled Breath Condensate

Hydrogen peroxide (H 2 O 2 ) plays a vital role in various physiological activities. Its efficient detection in exhaled breath condensate (EBC), a highly promising noninvasive diagnostic matrix, is of great significance for the early diagnosis of diseases. However, complex biological components present in EBC impede efficient H 2 O 2 detection. Herein, we synthesize an H 2 O 2 probe, TPEB , which demonstrates excellent sensing performance in phosphate-buffered saline (PBS) and EBC. TPEB exhibits turn-on fluorescence signal generated through H 2 O 2 -triggered hydrolysis, releasing TPEN , a compound with characteristic aggregation-induced emission properties. Density functional theory (DFT) and time-dependent DFT calculations reveal a molecular transformation from the donor–acceptor (D–A) structure of TPEB to the D–D′ structure of TPEN . Leveraging this transformation, the probe achieves a limit of detection (LOD) of approximately 0.1   μM in a DMSO/PBS buffer solution for H 2 O 2 , with excellent selectivity and stability. To enhance its portability and applicability, a probe film is fabricated by depositing TPEB nanoparticles onto a filter paper. This film exhibits stronger emission than TPEB in the DMSO/PBS buffer solution and achieves a lower LOD of 0.01   μM. The probe film enables effective H 2 O 2 detection in complex matrices, such as cell culture medium and EBC, demonstrating potential for practical point-of-care testing applications.