Inactivation of bacteria from contaminated streams in Limpopo, South Africa by silver- or copper-nanoparticle paper filters.

There is an urgent need for inexpensive point-of-use methods to purify drinking water in developing countries to reduce the incidence of illnesses caused by waterborne pathogens. Previously, our work showed the deactivation of laboratory-cultured bacteria by percolation through a thick paper sheet containing either silver (Ag) or copper (Cu) nanoparticles (NP). In this study, these paper filters containing AgNPs or CuNPs have been tested with water sourced from contaminated streams in Limpopo, South Africa.

Microwave-assisted incorporation of silver nanoparticles in paper for point-of-use water purification.

This work reports an environmentally benign method for the preparation of silver nanoparticles (AgNPs) in paper using microwave irradiation. Through thermal evaporation, microwave heating with an excess of glucose relative to the silver ion precursor yields nanoparticles on the surface of cellulose fibers within three minutes. Paper sheets were characterized by electron microscopy, UV-Visible reflectance spectroscopy, and atomic absorption spectroscopy.

Incorporation of copper nanoparticles into paper for point-of-use water purification.

As a cost-effective alternative to silver nanoparticles, we have investigated the use of copper nanoparticles in paper filters for point-of-use water purification. This work reports an environmentally benign method for the direct in situ preparation of copper nanoparticles (CuNPs) in paper by reducing sorbed copper ions with ascorbic acid. Copper nanoparticles were quickly formed in less than 10 min and were well distributed on the paper fiber surfaces.

Bactericidal paper impregnated with silver nanoparticles for point-of-use water treatment.

There is an urgent need for cheap point-of-use methods to purify drinking water. We describe a method to deactivate pathogenic bacteria by percolation through a paper sheet containing silver nanoparticles. The silver nanoparticles are deposited by the in situ reduction of silver nitrate on the cellulose fibers of an absorbent blotting paper sheet.

Tensile properties of twisted hair fibers.

Hair is routinely twisted during grooming processes, which can cause tangles and lead to breakage of hair fibers. To evaluate the damage caused by twisting hair, the tensile stress-strain properties of single twisted hair fibers were measured by two different experimental procedures: (A) twist at constant length, followed by extension to break (without untwisting); and (B) twist and untwist at constant length, followed by extension to break. In procedure (A), the strength, extension, and initial modulus decreased with increase in twist factor, whereas in procedure (B), the strength and extension did not significantly change from control values, although the initial modulus decreased with increase in twist factor.