Multifunctional composites have been investigated for destruction of bio-agents. These materials’ unique properties at the nano scale, including their abrasive character and high surface area leading to very close contact with cells, and their unusual surface morphology leading to high surface reactivity, make them promising biocides. Nanoparticles can also be prepared in a variety of forms such as powders, slurries, pellets, and membranes, making them more convenient and widely applicable for bio-agent destruction. Additionally, nanoparticles can generally be easily stored, which increases their flexibility.

The multifunctional metal oxide-silica composite nanoparticles developed for destruction or neutralization of targeted biomolecules.

Although metal oxide nanoparticles perform well in destroying vegetative bacteria, the reactivity of the pure metal oxide nanoparticles may not be strong enough to destroy non-vegetative bacteria (e.g., spores) that would be more vulnerable to additional attack. Therefore, formation of efficient agents for destruction of bio-agents necessitates incorporating strong conventional biocides that synergistically function with metal oxide nanoparticles. This concept becomes very important in the case of spores, where a combination of two agents is usually much more efficient than one agent alone, and very often necessary. Ideal nanoparticle-based biocides should be equipped with desirable multifunctionality including the ability to deliver large amounts of biocides, efficient co-encapsulation of one or more agents, and reactive or energetic destruction of bio-agents.

The objective of this research is to develop a new, efficient bio-agent neutralizer or destructor based on multifunctional composite nanoparticles in large scale; and to gain a fundamental understanding of the basic science of how structure, surface chemistry, and catalytic species affect chemical absorption and deactivation of bio-agents by dissecting structureproperty- performance relationships of these materials, and by understanding their synthesis and resulting structure and composition of the materials.

Reactive and multifunctional porous metal oxide-silica composite nanoparticles (ZnO-SiO2 nanoparticles) were developed for efficient destruction or neutralization of targeted biomolecules (chemical warfare agents, bio-agents, and other toxics) by aero-oxidation, electro-oxidation, or photo-catalytic oxidation. In the composite nanoparticles, metal oxides crosslink surfactant or polymer into core-shell micellar composite nanoparticles. The surface of the porous silica is covalently bonded with an organic functional group through silane chemistry.

Finally, reactive and multifunctional porous silicon (PSi)-Titania (TiO2) or PSi-silver (Ag) heterojunctions were developed. There materials have efficient destruction and neutralization of targeted biomolecules (chemical warfare agents, bio-agents, and other toxics) by combined effects of aero-oxidation, electro- oxidation, photo-catalytic oxidation and absorption. The reactive and multifunctional porous silicon (PSi)-Titania (TiO2) or PSi-silver (Ag) heterojunctions were synthesized. In the composite nanoparticles, Titania and/or silver nanodots were dispersed on the surface of silicon particles instead of the coreshell structure to utilize mass transmission.

This project focused on synthesis and characterization of multifunctional composite nanoparticles, such as micellar Au-metal oxide core-shell nanoparticles, metal oxide (ZnO)-silica composite nanoparticles, porous silicon (PSi)-Titania (TiO2), and PSi-silver (Ag) heterojunctions.

This work was done by Donghai Wang of Pennsylvania State University for the Defense Threat Reduction Agency. DTRA-0003

Aerospace & Defense Technology Magazine

This article first appeared in the December, 2015 issue of Aerospace & Defense Technology Magazine.

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