1：Experimental Design and Method Selection:

The study involved designing and synthesizing a perylenediimide-based fluorescent probe (PDI-HY) for formaldehyde detection, utilizing a condensation reaction mechanism. Theoretical models included density functional theory (DFT) calculations to understand the photo-induced electron transfer (PET) process.

2：Sample Selection and Data Sources:

Formaldehyde solutions of varying concentrations were used, along with other biologically relevant species for selectivity tests. HeLa cell lines were employed for live cell imaging.

3：List of Experimental Equipment and Materials:

Instruments included a fluorescence spectrometer for optical measurements, NMR and MS for characterization, and a confocal microscope for cell imaging. Materials included PDI derivatives, hydrazine, formaldehyde, and various buffers.

4：Experimental Procedures and Operational Workflow:

The probe was synthesized via amidation reaction. Optical responses were measured by adding formaldehyde to probe solutions and monitoring absorption and emission spectra. Time-dependent fluorescence changes, pH dependence, and selectivity tests were conducted. DFT calculations were performed to analyze molecular orbitals. Live cell imaging involved incubating HeLa cells with the probe and formaldehyde, followed by fluorescence observation.

5：Data Analysis Methods:

Fluorescence titration curves were used to determine detection limits. Statistical analysis included linear regression for concentration-response relationships. Quantum yields were calculated using standard methods.