Browsing by Author "Palza, Humberto"

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    A three step recipe for designing auxetic materials on demand
    (2022) Acuna, Daniel; Gutierrez, Francisco; Silva, Rodrigo; Palza, Humberto; Nunez, Alvaro S.; During, Gustavo
    Auxetics are an unusual family of materials that, for instance, when stretched in a particular direction will exhibit an expansion of the dimensions that are perpendicular to the applied stress; however, despite many known examples of auxectics there is no universal description of the material properties. Here, the authors report a model based on antiferromagnetic spins and demonstrate how this can be used to design a auxetic material with a Poisson ratio of -1 over a range of finite strain.
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    Antibacterial Silver Nanoparticles Supported on Graphene Oxide with Reduced Cytotoxicity
    (2019) Angulo-Pineda, Carolina; Palma, Patricia; Bejarano, Julian; Riveros, Ana; Kogan, Marcelo; Palza, Humberto
    The effect of graphene oxide (GO) on both the antibacterial and cytotoxicity behavior of silver nanoparticles (Ag NPs) has been studied. Ag NPs supported on GO were synthesized by two methods, ex situ and in situ. These nanocomposites were characterized by transmission electron microscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, and Fourier-transform infrared spectroscopy. The antibacterial activity of the nanomaterials was evaluated against Escherichia coli and Staphylococcus aureus by the disk-diffusion method and dynamic contact assays. While GO flakes showed antibacterial behavior only in the dynamic contact test, both GO-Ag NPs nanohybrids eradicated bacteria independent of the condition. Noteworthily, the high cytotoxicity of Ag NPs to human-derived cells was dramatically decreased by the GO layers in the nanocomposite. The in situ hybrid particles showed the lowest cytotoxicity without losing the strong antibacterial effect. These results demonstrate that growth of Ag NPs on GO layers could enable the development of a new family of antibacterial materials with low cytotoxicity to human cells.