In recent years, core shell fluorescent silica nanoparticles (F) have been used in many researches due to their high biocompatibility, high intensity fluorescent signals and ease of surface modification process and high stability. In this study fluorescent silica nanoparticles were prepared by Stober method using fluorescein isothiosyanate (FITC) dye. Fourier Transform Infrared Spectroscopy results showed that the fluorescent dye was attached to silica by a silane coupling agent. Field emission scanning electron microscopy (FESEM) and scanning electron microscopy (SEM) images showed that the size of the nanoparticles was uniform with average diameter of 326 nm. The fluorescent intensity measurements of F and FITC showed that intensity of fluorescent silica nanoparticles was four times higher than that of dye molecules. The synthesized F at pH 7.7 were characterized by FESEM and SEM and the results showed that the produced F had smaller size and their diameters were almost halved. The fluorescent intensity of nanoparticles in phosphate buffer solutions with different pH were measured. According to the results, the fluorescent intensity was increased with increasing pH and F with smaller size showed lower intensity. To produce pH-sensitive nanofibers, a 12% solution of PAN in DMF was prepared and 1.5% of nanoparticles were added to it and was dispersed in an ultrasonic bath and then nanofibers were produced using electrospinning technique. FESEM and SEM images showed that nanofibers containing different size of F had the same diameters. Fluorescent microscopy images showed the fluorescent properties of the nanofibers. Fluorescent intensity of nanofibers containing larger F was five times more than that of nonafibers containing smaller F. The fluorescent intensity of the nanofibers also was increased with increasing pH of the medium. Keywords: synthesis of core shell fluorescent silica nanoparticles, pH-sensitive
