Crack-free high surface area silica-titania nanocomposite coating as opto-chemical sensor device

•Sol-gel based matrix for functionalized dyes encapsulation was synthesized.•Strong interaction of dyes with matrix was examined without cracking/leaching.•Narrow particle size distributions were established.•High surface area 400 m2/g, has more capability to sense the broaden pH range.•The films show good optical qualities with tunable refractive index 1.57–1.52.•Sensor shows stability towards higher pH values and significant linear relationship. This work highlights the versatility of sol-gel-derived nanocomposite silica-titania host matrix along with functionalized organic dyes i.e., bromophenol blue (C19H10Br4O5S), phenol red (C19H14O5S), cresol red (C21H17NaO5S) and phenolphthalein (C20H14O4) encapsulation with surfactant CTAB for pH sensing. The synthesized matrices before and after heat treatment (at 150 °C and 250 °C) are analyzed for chemical and physical uniformity; observed as stable, homogeneous, low surface roughness and with functionalized nano-pore surfaces. Particle size distributions in the range of 2.28 nm, 2.73 nm and 2.54 nm are established. Surface analysis shows that the nanoparticles are uniformly distributed on the surface of the mesoporous channel systems with high surface area 400 m2/g, and highly accessible pore system which has more capability to sense the broad pH range. The films show good optical qualities in the visible region with tunable refractive indices 1.57, 1.52-and 1.56. The response of the prepared sensor even shows stability towards higher pH value 12 and has linear relationship with correlation coefficient R2 ∼0.9341. The sensitivity of the proposed pH sensor is observed to be 0.614 mV/pH.