Preparation of novel core-shell silica particles for pH sensing using ratiometric fluorescence approach

Core-shell silica particles encapsulating two luminescent dyes with different emission wavelengths were prepared for ratiometric fluorescence sensing of pH. The composite core-shell structure particles contained a polyacrylonitrile (PAN) core surrounding a silica shell. Fluorescein isothiocyanate (FITC) encapsulated in the silica shell was taken as an indicator, Fluorescence emission from Ru(dpp)3(ClO4)2 immobilized in PAN core was used as a reference light. The ratiometric fluorescence signal from the core-shell silica particles were found with a linear range from pH 5.80 to 7.50 (R2 = 0.997). In addition, the morphology of the core-shell silica particles, the effects of temperature and co-existing substances were investigated. The core-shell silica particles were successfully applied to determination of pH value in water and urine samples.