Formation of Stable Gel Colors of Calcium Alginate

By a newly developed gel-preparation method using binary aqueous mixed solvents, such as a methanol–water or an ethanol–water mixture, before gelation as a sol solvent and after gelation as a gel environmental solvent, stable gel colors and xerogel colors of calcium alginate (Ca alg.) including photosensitive chlorophyll a (chl.a) were obtained. Ca alg. gel containing leucomalachite green (leuco-M) was made by using the same mixed solvents; after gelation by immersion in mixed solvents or in an acidic solution of various pH values, color development was investigated under ultraviolet irradiation (365 nm). From gel rupture stress measurements, absorption spectral measurements, and an X-ray diffraction study, etc., it was found that such gel-color stability mainly depends on the conformational stability of the host gel.

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