Fluorescence properties of a carminic acid-based composite embedded in a silica matrix

Harnessing the outstanding properties of carminic acid in developing hybrid materials requires studying its physical properties and its interaction with the matrix. It is also desirable to prevent its degradation under different conditions, particularly when it is subjected to a high work temperature. In this work, the behavior of the fluorescence properties was investigated from a carminic acid hybrid composite subjected to different temperatures. The carminic acid was extracted from the Mexican cochineal and stabilized using sucrose to avoid its degradation. Then, the resulting dye was embedded in a silica matrix using the sol-gel method. The hydrolysis reaction was experimentally established using the ratios of 4:1 ethanol to TEOS and 11:1 water to TEOS. The obtained red-colored powder contains carminic acid in equilibrium with the silica. The characterization of the hybrid particles was carried out using scanning electron microscopy (SEM), fluorescence emission, FT-IR, UV-vis, and XRD. The organic-inorganic components show an intense interaction capable of changing the fluorescence emission and improving the thermal stability of the organic molecules embedded in the silica. Results also show that carminic acid remains functional at 500 C; however, the fluorescence spectrum shows its maximum intensity at 400 C. These behaviors have been attributed to the structural evolution of the inorganic matrix and its close interaction shown with the organic dye.