Nanomaterial-Enabled Disinfection and Microbial Control

Picture of (a) nAg membrane and (b) control membranes showing the E. coli stained by DAPI. Cell growth was significantly inhibited in the presence of  nAg in membranes.

Ensuring inexpensive and clean water for everyone is one of the Millennium Development Goals of the United Nations.  We seek to help meet this challenge by developing and testing nanotechnologies that are affordable and easy to use in decentralized water and wastewater treatment and reuse systems.  Here, we examined fullerene-based nanomaterials (colloidal C60, encapsulated C60, and functionalized C60) for their photocatalytic activity, nano-sized magnetite for its adsorptivity, the addition of silver nanoparticles to water treatment membranes for increased virus adsorption and antimicrobial activity, adsorption of particles onto silica structures, and disinfection of viruses by nAg-doped TiO2. Through this research, we have shown that the production of reactive oxygen species (ROS) in water by fullerene nanoparticles varies significantly depending on the form of C60 and the chemistry of the aqueous medium. Water-soluble amine-functionalized C60 (tetrakis- and hexakis adducts) were photoexcited with visible light and exhibited much higher photoreactivity relative to fullerol and unmodified C60, which makes these C60 derivatives attractive for use for photodegradation of water pollutants and disinfection. The effective virus removal by magnetite nanoparticles (previously shown to remove arsenic, project 9.3.1.1) was demonstrated, and the removal efficiency increased with increasing concentrations of divalent cations, specifically Ca2+.  Silver is a potent antimicrobial agent and is used in a variety of consumer products for antimicrobial control.  In our previous work, we added nanosilver to a polysulfone membrane to produce a membrane that is resistant to biofouling.(Zodrow, Brunet et al. 2009)  Additionally, we observed that these membranes enhanced virus removal through local electrostatic interactions between the virus particles and the silver oxides.  We showed that adsorption of particles onto silica can be reduced by modifications in the silica structure, and that virus deactivation by ultraviolet light can be enhanced in the presence of nAg-doped TiO2.  In upcoming studies, we will explore (1) the application of water-soluble functionalized C60 as an environmentally-benign and reusable photocatalyst through its immobilizing on the supporting materials such as beads and polymers, (2) interaction between viruses on metal and metal oxide nanoparticles via analytical techniques (QCM-D, DLS, and AFM) to further elucidate viral removal on the surface of nanoparticulate metals and metal oxides, (3) the mechanism of bacteria attachment onto different surfaces, taking into account electrostatic interactions and roughness, and (4) the mechanism of virus inactivation and possible ROS production by nAg-TiO2.

Participating Researchers:

• Pedro Alvarez
  
• Vicki Colvin
• Qilin Li
• Jun Lou