Sol-gel based optically active phenolphthalein encapsulated nanomatrices for sensing application

In this work, synthesis and characterization of phenolphthalein-immobilized titania (T-phph) and silica–titania (ST-phph) nanomatrix is reported. The thin films are deposited by sol–gel method at low temperature. The effect of host–guest chemistry in matrices, on the surface structures, optical and sensing activity of the resultant thin films is studied. The phenolphthalein-immobilized fabricated nanoparticles/nanomatrices are analyzed by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy, atomic-force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, surface analysis, thermogravimetric analysis, and UV–Vis spectroscopy. Thermally stable and high surface area homogeneous nanoparticles, containing nanocrystalline anatase phase with low refractive index (1.58), low roughness (5.5 nm), and high transparency (95 %) are obtained for phenolphthalein-immobilized ST-phph nanomatrix. Moreover, smaller nanoparticles (56–121 nm) with good incorporation of dye and good response of sensing are obtained. The sensor response is optimized at pH 12 with 10.1 pKa value at 555 nm. Graphical Abstract: [Figure not available: see fulltext