1：Experimental Design and Method Selection:

Gelatine gels were prepared by gelation in solutions of NiCl2·6H2O, CoCl2·6H2O, and CrCl3·6H2O at concentrations of 5% to 50%. Properties were analyzed using FTIR spectroscopy, TGA, UV-vis spectroscopy, and colorimetry.

2：0%. Properties were analyzed using FTIR spectroscopy, TGA, UV-vis spectroscopy, and colorimetry. Sample Selection and Data Sources:

2. Sample Selection and Data Sources: Gelatine type B food-grade powder (E. Merck) and metal chlorides (Strem Chemicals Inc.) were used. Samples were classified into three groups based on salt type.

3：List of Experimental Equipment and Materials:

Gelatine powder, metal chlorides, double-distilled water, autoclave (HL-320), water bath, glass dishes, micro-analytical balance (Sartorius), TGA instrument (TA-50, Shimadzu), FTIR spectrophotometer (FTIR-8400S, Shimadzu), UV-vis spectrophotometer (Perkin-Elmer 4-B).

4：Experimental Procedures and Operational Workflow:

Gelatine and salts were dissolved separately, sterilized, mixed, sterilized again, poured into dishes, and incubated to form gels. TGA was performed in nitrogen atmosphere, FTIR from 400 to 4000 cm?1, UV-vis from 200 to 800 nm.

5：Data Analysis Methods:

TGA data analyzed using Coats-Redfern equation for thermodynamic parameters; FTIR spectra interpreted for structural changes; UV-vis data used for Tauc plots to calculate band gaps and Urbach energies; color parameters calculated using CIE 1931 system.