Fabrication and characterization of FITC-modified naturalbased silica nanoparticles using sol-gel method

This research aimed to synthesize fluorescent silica nanoparticles (SiFITC) modified with the fluorescein isothiocyanate (FITC) dye using sol-gel method. The FITC dye was used as the fluorophore to produce fluorescent silica nanoparticles. The precipitate from geothermal power plant containing SiO₂ was used as a precursor and added with NaOH at 90°C generating sodium silicate. FITC solution was added with various concentrations ranging from 0.1, 0.2, 1, 5 to 10 mg/mL and the mixture was allowed to age for 18 hours. Characterization of SiFITC was measured using fluorescence spectrophotometer to obtain the fluorescence intensity, Fourier Transform Infra-Red (FT-IR) spectroscopy to determine the functional group of SiFITC, Brauner Emmett-Teller (BET) adsorption method to calculate the specific area of the nanoparticles, and X-ray diffraction (XRD) to analyze the crystallographic phases. Fluorescent intensity showed that SiFITC with 1 mg/mL of FITC had the lowest fluorescence intensity indicating self-quenching mechanism due to the overloading of the dye in the silica matrix. The FT-IR spectra showed vibration at wavenumber of 956 (Si-O); 1073 and 798 (Si-O-Si); 3396 (OH) and 1631 cm⁻¹ (Si-OH). BET analysis showed that the specific surface of the SiFITC 480 m²/g and XRD results showed that the samples were in amorphous phase with uniform pore distribution. The results showed that the FITC-modified silica nanoparticles have great potential for further investigation in biosensing applications, particularly fluorescence or optical based detection of antibiotic resistant bacteria.