1：Experimental Design and Method Selection:

The study involved synthesizing a rhodanine-based probe (2-OxI-Rh) via a green approach and evaluating its sensing properties for metal ions using colorimetric and fluorometric techniques. Theoretical models include Job's plot for binding ratio and Benesi-Hildebrand equation for binding constants.

2：Sample Selection and Data Sources:

Samples included the synthesized probe 2-OxI-Rh and various metal ions (e.g., Hg2+, Cu2+) as chloride salts. Data were acquired from UV-Vis and fluorescence spectroscopy measurements.

3：List of Experimental Equipment and Materials:

Equipment included a Buchi 539 capillary melting apparatus for melting points, Mattson 1000 FT-IR spectrophotometer for IR spectra, Varian and Bruker spectrometers for NMR, LECO CHNS-932 for elemental analysis, silica gel for chromatography, TLC plates, JEOL JES-FA300 ESR spectrometer for ESR, Shimadzu UV-3101PL UV-Vis-NIR spectrometer for UV-Vis, and Perkin-Elmer LS 55 Fluorescence Spectrophotometer for fluorescence. Materials included chemicals from Sigma-Aldrich or Merck, ethanol, HEPES buffer, HClO4, NaOH, and various metal salts.

4：Experimental Procedures and Operational Workflow:

Synthesis of 2-OxI-Rh involved heating 3-amino-rhodanine and isatin in ethanol. Sensing studies involved preparing solutions of probe and ions, recording UV-Vis and fluorescence spectra after adding ions, performing titrations, Job's plot measurements, and competitive experiments. pH studies were conducted using HClO4 or NaOH to modulate pH.

5：Data Analysis Methods:

Data were analyzed using Job's plot for binding stoichiometry, Benesi-Hildebrand equation for binding constants, and standard formulas for LOD and LOQ. Statistical techniques included linear regression (R2 values).