| Author | Shamim, Shadmani |
| Note | A thesis submitted in partial fulfillment of the requirements for the
degree of Master of Engineering in
Nanotechnology |
| Publisher | Asian Institute of Technology |
| Abstract | In this thesis, we synthesized porous silica (SiO2) nanoparticles and investigated their fluorescence properties. Silica nanoparticles are prepared in aqueous medium using a wet chemical synthesis route where cetyltrimethylammonium bromide (CTAB) is used as template and structure directing agent during the nanoparticle growth and TEOS was used as the precursor. The morphology, size and porosity of the silica nanoparticles were characterized by transmission electron microscopy (TEM), dynamic light scattering (DLS) and helium (He) pycnometry. The as prepared silica nanoparticles mostly showed slight anisotropic shape (near spherical or elongated spherical) with length varying between 40 to 160 nm and width varying in the range of 30 to 120 nm. Upon calcination of these synthesized silica nanoparticles at different temperatures from 200°C to 800 °C, the He pycnometry results indicated a gradual decrease in the porosity in the nanoparticles. The fluorescence properties of the silica nanoparticles were then investigated by modification of the nanoparticle with (3-Aminopropyl) triethoxysilane (APTES). The effect of calcination temperature on the fluorescence properties of the silica nanoparticles were investigated with various concentrations of APTES and the possible fluorescence source in the silica nanoparticles were probed by using X-ray photoelectron spectroscopy (XPS) technique. The APTES molecules were found to play an important role in the visible light fluorescence from silica nanoparticles by incorporating impurity defects in the silica lattice and at calcination temperatures above 600 °C these defects are found to be eliminated from the nanoparticles reducing their fluorescence intensity. However, the intrinsic defects in the silica nanoparticles were also responsible for fluorescence emission in the blue region. Therefore, the origin of the fluorescence in our samples was because of the independent yet combined actions of the intrinsic defects already present in the silica nanoparticles and the impurities introduced through the calcination of the aminopropyl groups in silica because of the surface modification. The results from this study will be useful for the controlled preparation of doping free porous and fluorescent silica nanoparticles, which has great potential in biomedical field of study as biomarkers and drug delivery agents. |
| Year | 2017 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Department of Industrial Systems Engineering (DISE) |
| Academic Program/FoS | Microelectronics (ME) |
| Chairperson(s) | Hornyak, Gabriel Louis ; |
| Examination Committee(s) | Loc Thai Nguyen;Bora, Tanujjal;Crespy, Daniel; |
| Scholarship Donor(s) | AIT Fellowship;Wisdom Scholarship; |
| Degree | Thesis (M.Eng.) -- Asian Institute of Technology, 2017 |