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Abstract
The immobilization of pH-sensitive organic dyes within sol–gel silica matrices has attracted considerable attention due to its potential in the development of solid-state optical sensing systems. In the present study, methyl orange (MO) was encapsulated into a HYPR-modified silica matrix prepared through an acid-catalyzed sol–gel process using tetraethyl orthosilicate (TEOS) as the silica precursor. The incorporation of a cationic surfactant during matrix formation was intended to improve the structural characteristics and accessibility of the porous silica network.
The resulting monolithic silica materials were transparent and mechanically stable, demonstrating successful immobilization of methyl orange within the inorganic–organic hybrid framework. Spectroscopic evaluation revealed that the encapsulated indicator preserved its pH-responsive behavior after immobilization, exhibiting optical characteristics comparable to those of the free indicator in solution. Surface morphology analysis suggested a homogeneous distribution of methyl orange molecules within the modified silica structure and indicated weak interactions between the indicator molecules and the host network.
The findings confirm that HYPR-modified sol–gel silica matrices provide a suitable environment for the immobilization of methyl orange while maintaining its sensing functionality. The developed hybrid material shows promising potential for application in solid-state pH monitoring and optical sensing technologies.
References
1. Alenazi, M. H., Mubarak, A. T., & Abboud, M. (2024). Incorporation of organic photochromic molecules in mesoporous silica materials: Synthesis and applications. Nanotechnology Reviews, 13(1), 20240032.
2. Brinker, C. J., & Scherer, G. W. (1989). Sol-Gel Science: The Physics and Chemistry of Sol-Gel Processing. Academic Press, San Diego, CA.
3. El-Nahhal, I. M., Zourab, S. M., & El-Ashgar, N. M. (2001). Immobilization of acid–base indicators in silica matrices prepared by the sol–gel process. Journal of Dispersion Science and Technology, 22(6), 583–590.
4. Faraji, M., Mansouri, F., Karimi, B., & Vali, H. (2025). A magnetic hybrid sol–gel ionic network catalyst for direct alcohol esterification under solvent-free conditions. Nanoscale, 17(31), 18161–18172.
5. Ferreira, B., Sousa, S., Sousa, R. P., Costa, S. P., Raposo, M. M. M., Parpot, P., et al. (2022). Organic–inorganic hybrid sol–gel membranes for pH sensing in highly alkaline environment. Construction and Building Materials, 360, 129493.
6. Hench, L. L., & West, J. K. (1990). The sol–gel process. Chemical Reviews, 90(1), 33–72.
7. Koç Keşir, M., Yıldız, İ. S., Bilgen, S., & Sökmen, M. (2022). Role of a novel cationic gemini surfactant on a one-step sol–gel process and photocatalytic properties of TiO₂ powders. Journal of Water and Health, 20(11), 1629–1643.
8. Lobnik, A., Oehme, I., Murkovic, I., & Wolfbeis, O. S. (1998). pH optical sensors based on sol–gel immobilized dyes. Analytica Chimica Acta, 367, 159–165.
9. Tong, M., & Febles, J. (2024). The Sensitive Spectrophotometric Determination of Trifluoperazine Hydrochloride via Ion-Association with Aniline Blue in Acidic Medium. Journal of Advancements in Interdisciplinary Sciences (JAISS), 1(1), 12-12.
10. Wolfbeis, O. S., & Rodriguez, N. V. T. (1992). Optical sensors based on immobilized indicators. Mikrochimica Acta, 108, 133–141.
11. Zaggout, F. R., El-Nahhal, I. M., Zourab, S. M., El-Ashgar, N. M., & Motaweh, H. J. (2005). Immobilization of organic indicators in sol–gel silica matrices and their sensing behavior. Journal of Dispersion Science and Technology, 26(5).
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Copyright (c) 2026 Farid Rafiq (Author)