Structural Characterization of Silica and Amino-Silica Nanoparticles by Fourier Transform Infrared (FTIR) and Raman Spectroscopy

Mesoporous silica nanoparticles were synthesized via the sol-gel method using hexadecyltrimethylammonium bromide (CTAB) micelles as a template and a similar method was used for amino-silica nanoparticle synthesis. Compositional and structural analysis of materials involved Fourier transform infrared (FTIR) and Raman spectroscopies. A comparative study of the two spectra revealed the distinctive pattern for the samples, such as a strong peak from 1030 to 1050 cm−1 in the FTIR spectra, characteristic of Si–O–Si stretching vibration and the specific pattern of silica between 90 and 500 cm−1 and 2880 and 2980 cm−1 in the Raman spectra. A point of interest in this study was the control of CTAB removal during the second stage of synthesis that was highlighted in the FTIR spectra by decreasing intensity or disappearance of the peaks 2850 and 2930 cm−1 for - CH2 absorption. The presence of – NH2 groups in the amino-silica was evidenced by the changes from 1000 to 1500 cm−1 and the sharp band at 2900 cm−1 in the Raman spectra. The peaks at 1050, 1230, 1421, and 1464 cm−1 are present only in the spectra of the amino-silica as well as the higher and sharp band around 2900 cm−1, unlike the pattern in the spectra of silica without amino groups. The two spectroscopic methods offer valuable information concerning the structure of silica and amino-silica. Moreover, thermogravimetric analyses were confirmed these findings and the stability of silica nanoparticles in solution was investigated.