CdTe nanoparticles encapsulation in mesoporous titania-silica nanocomposite for phenol red pH sensing

Owing to phenol red (PR) pH sensing, cadmium telluride (CdTe) nanoparticles are encapsulated in titania-silica nanocomposite (CdTe-TSNC) at low temperatures by sol-gel method. Scanning electron microscopy (SEM) revealed the dense and porous colonial nanostructures of CdTe-TSNC. Atomic force microscopy (AFM) possessed an average surface roughness of around 4 nm and a thickness 25 nm for TSNC (titania-silica nanocomposite) which reduced to 1 nm and 4 nm, respectively, after CdTe encapsulation. Thermally stable CdTe-TSNC possessed a large surface area 411 m2/g, transmittance 77 %, and refractive index 1.4 at 550 nm. The PR/CdTe-TSNC (PR immobilized CdTe-TSNC) exhibited large pKa 9.4 with fast time response 0.21 s in pH 12 without leaching.