1：Experimental Design and Method Selection:

The study involved designing and synthesizing a Schiff-base compound (CECA) for Al3+ detection. Methods included colorimetry (naked eye observation), ultraviolet absorption spectroscopy, and fluorescence spectroscopy to detect Al3+ qualitatively and quantitatively. The mechanism was investigated using Job's plot, 1H NMR, EI-MS, and fluorescence methods.

2：Sample Selection and Data Sources:

Metal ions (Ag+, Al3+, Ca2+, Cd2+, Co2+, Cu2+, Fe3+, Hg2+, K+, Na+, Ni2+, Pb2+, Zn2+) were used as nitrates in ultrapure water. The solvent for in vitro tests was ethanol. HeLa cells were cultured for imaging experiments.

3：List of Experimental Equipment and Materials:

Materials included carbazole, N,N-Dimethylformamide (DMF), phosphorus oxychloride, metal nitrates, ethanol, DMSO, PBS, H-DMEM, penicillin/streptomycin, Fetal Bovine Serum. Equipment: Bruker Avance 400 spectrometer (1H NMR), Nicolet Avatar 370 infrared spectrometer (FTIR), Agilent-6510-Q-TOF (EI-MS), Perkin 2400 (II) auto-analyzer (elemental analysis), Olympus FV-300 confocal microscope (cellular imaging), UV-2500 spectrophotometer (ultraviolet absorption), F-7000 spectrophotometer (fluorescence).

4：Experimental Procedures and Operational Workflow:

Synthesis of CECA involved refluxing intermediates in ethanol, filtration, washing, and vacuum drying. Spectral measurements were conducted in 1 cm quartz cells. For cell imaging, HeLa cells were incubated with CECA and Al3+, washed with PBS, and imaged using a confocal microscope with excitation at 405 nm and emission from 425-500 nm.

5：Data Analysis Methods:

Detection limits were calculated using LOD = 3Sb/K. Binding constant (Ka) was determined using the Benesi-Hildebrand equation. Stoichiometry was assessed via Job's plot. Data analysis involved linear regression for concentration relationships.