Antimicrobial Property of Polypropylene Composites and Functionalized Copper Nanoparticles

Copper nanoparticles (CuNPs) functionalized with polyethyleneimine (PEI) and 4-aminobutyric acid (GABA) were used to obtain composites with isotactic polypropylene (iPP). The iPP/CuNPs composites were prepared at copper concentrations of 0.25-5.0 wt % by melt mixing, no evidence of oxidation of the CuNP was observed. Furthermore, the release of copper ions from iPP/CuNPs composites in an aqueous medium was studied. The release of cupric ions was higher in the composites with 2.5 and 5.0 wt %. These composites showed excellent antibacterial activity (AA) toward Pseudomona aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The incorporation of CuNP into the iPP polymeric matrix slightly decreased the thermal stability of the composite material but improved the crystallinity and the storage modulus. This evidence suggests that CuNPs could work as nucleating agents in the iPP crystallization process. The iPP/CuNPs composites presented better AA properties compared to similar composites reported previously. This behavior indicates that the new materials have great potential to be used in various applications that can be explored in the future.

Enhanced photocatalysts based on Ag-TiO2 and Ag-N-TiO2 nanoparticles for multifunctional leather surface coating

The Ag deposition on TiO2 nanoparticles (Ag-TiO2 NPs) and N-TiO2 nanoparticles (Ag-N-TiO2 NPs) has been made by electrochemical methodology in view of improved antibacterial properties and enhanced photocatalytic activity under visible light irradiation. The particle size in powder and in dispersion showed similar values and good stability in aqueous medium which made them suitable for use in leather surface covering for new multifunctional properties development. The diffuse reflectance spectra of Ag-TiO2 NPs, Ag-N-TiO2 NPs and TiO2 NPs have been investigated and correlated with their photocatalytic performances under UV and visible light against different silver concentrations. The leather surfaces treated with Ag-N-TiO2 NPs showed advanced self-cleaning properties under visible light exposure through the hydrophilic mechanism of organic soil decomposition. Moreover the bacterial sensitivity and proven fungitoxic properties of Ag-N-TiO2 NPs leads to the possibility of designing new multifunctional additives to extend the advanced applications for more durable and useable materials.

Antibacterial Additive for Polystyrene Based on Silver Nanoparticles Supported on Titanium Dioxide

Silver nanoparticles supported on titanium dioxide nanoparticles (Ag/TiO2) were incorporated and evaluated as antibacterial additive for polystyrene materials. These particles were synthesized using a deposition-precipitation method by adding silver nitrate as metallic precursor, sodium hydroxide as reducing agent, and commercial TiO2 (P25) as support. Rectangular pieces of polystyrene (PS) containing 100, 300, 500, and 700 ppm (wt.%) of the additive were made using an extrusion-injection molding process, and they were evaluated for their antibacterial properties against Escherichia coli using the Pour Plate method. Particles were distributed on the PS surface, and PS pieces presented a good antibacterial efficiency at 100, 300, and 500 ppm and decreased for 700 ppm due to an additive agglomeration on the PS surface. These results validate the antibacterial properties of Ag/TiO2, determine a concentration limit at which the additive is well distributed on the PS surface, and assess the importance of Ag in this system.