SURFACE MODIFICATION OF SILICA NANOPARTICLES USING SURFACE COUPLING AGENTS

Open Access
Author:
AlJama, Hassan
Area of Honors:
Chemical Engineering
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Themis Matsoukas, Thesis Supervisor
  • Themis Matsoukas, Honors Advisor
  • Darrell Velegol, Faculty Reader
Keywords:
  • Silica
  • nanopaticles
  • surface modifications
  • surface coupling agents
  • colloid
Abstract:
The effects of surface treatment of three aminosilanes on silica nanoparticles was investigated: 3-aminopropyltriethoxysilane (APES), aminopropyldimethylethoxysilane (APMS), and N-[3-(Trimethoxysilyl)propyl]ethylenediamine (TMPE). Aminosilanes attach to the surface of silica nanoparticles via a hydrolysis reaction of the ethoxy group(s). Surface modification was characterized through Dynamic Light Scattering (DLS), which measures the diameter of the particles, Zeta potential, which measures the charge of the particles, and Transmission Electron Microscopy (TEM), which gives images of the particles at the nanoscale level. It was proposed that surface modification will further stabilize the particles due to the formation of an unreactive steric layer. Zeta potential measurements showed different isoelectric point for each aminosilane, with the highest being for TMPE (pH=8.6), followed by APMS (pH=7.4), and lastly APES (pH=4.9). Zeta potential results indicate that even though surface of the particles is modified upon adding the aminosilane, surface treatment with all the 3 aminosilanes destabilize particles in the near neutral pH region due to electrostatic forces, where zeta potential exhibits values <|20mV|. Hence, electrostatic forces seem more dominate than steric hinderance. A two-step modification process using an aminosilane followed by glutaric anhydride was also investigated. Results showed that there is not a direct relationship between glutaric anhydride concentration and shifts in IEP. However, particle’s charge was further improved in the neutral pH region (by up to 10 mV in the cases of APMS and APES, and by up to 15 mV in the case of TMPE). This was achieved at certain glutaric anhydride concentrations.