Abstract
Understanding the colloidal properties of nanometer-sized particles is essential to successful processing of manufactured nanophase materials. The small length scale at which particles interact presents new and unique challenges. Dispersion and stability can be difficult goals at the nanoscale. Nanoparticles always tend to agglomerate, decreasing the surface-to-volume ratio and, as a result, the free energy of the system. The force that drives the agglomeration process is the van der Waals attraction. The forces that may prevent the agglomeration and increase colloidal stability are the electrostatic and steric repulsions between the surfaces. Suspensions with strong repulsive forces between particles are generally well dispersed and stable. A variety of techniques have been employed to increase the stability of dispersions. Simple mechanical stirring is used to break up soft agglomeration. Sonication can be used as a temporary measure to break up agglomerates, especially if they are large and the particles are weakly bonded. In a simple liquid environment, interparticle forces can be adjusted or tailored by using a suitable dispersion media, adjusting solution pH and ionic concentration, or by using surfactants or polymers that adsorb on particle surfaces. These different approaches to dispersion stabilizations can work quite well in many circumstances; however, their use is often limited. We focused on studies of the colloidal behaviors of titanium dioxide (TiO2) nanoparticles in aqueous systems, which were analyzed by dynamic light scattering (DLS) and UV- vis spectrometry. In this study, types of titanium dioxide and effects of ultra-sonication, irradiation time, and storage time were investigated systematically. It was found that ultrasonication can help to break up agglomeration. Also, upon pretreatment of UV irradiation, the dispersion and stability of TiO2 nanoparticles in deioned water was greatly enhance by increasing the zeta potential. Furthermore, the titanium dioxide were characterized by Brunauer-Emmett-Teller (BET), X-Ray Powder Diffractometer(XRPD), temperature programmed reduction (TPR), Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS). It was found that after UV irradiation, the amount of hydroxyl group increased, which induced hydrophilicity and improved the dispersion and stability of titanium dioxide.