A novel nano-sensor based on rhodamine-β-isothiocyanate -: Doped silica nanoparticle for pH measurement

The preparation of fluorescent pH-sensitive nanoparticles and monitoring the pH in real samples is described. A novel fluorescent core-shell nanoparticle was developed by encapsulating the rhodamine-beta-isothiocyanate (RITC) in a silica shell with a reverse microemulsion technique. The RITC encapsulation reduces RITC leaching from the silica matrix when immersed in water. The hydrophilic silica shells are made by hydrolyzing and polymerizing tetraethoxysilane (TEOS). The fluorescent core-shell nanoparticles are pH-sensitive, and the pH dynamic range of the sensing nanoparticles is between 5.0-10.0. The method offers the advantages of adequate sensitivity, accuracy and rapid detection of pH. The results are in good agreement with those using the standard glass electrode method. They show excellent stability and high reproducibility when used as pH sensors.