Browsing by Author "Castañeda Parra, Erik Alexander"

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    An ionic polymer route to a stable unpinning of the Fermi level of highly doped graphene
    (2025) Pradeepkumar, Aiswarya; Yang, Yang; Castañeda Parra, Erik Alexander; Ángel Figueroa, Felipe Alfonso; Iacopi, Francesca
    Epitaxial graphene on cubic silicon carbide on silicon could enable unique optical metasurface devices seamlessly integrated with CMOS technologies. However, one of the most promising methods to obtain large-scale epitaxial graphene on this challenging system typically leads to a highly p-type-doped graphene with a Fermi level pinned at ∼0.55 eV below the Dirac point. Hence, the use of conventional gate dielectric materials such as SiO2 and Si3N4 precludes the tuning of the graphene carrier concentration. We demonstrate that this limitation can be overcome with the use of polyethyleneimine (PEI) as a gate dielectric material for graphene field-effect transistors. We achieve significant tuning of the graphene's Fermi level, enabling ambipolar operation exceeding a 3 eV window. In addition, we demonstrate that excellent stability of the PEI-based devices can be achieved, thanks to the addition of a thin protective oxide film. These findings highlight the potential of ionic polymers for advancing reconfigurable graphene-based devices for photonic applications.
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    Conducting polymer applied in a label-free electrochemical immunosensor for the detection prostate-specific antigen using its redox response as an analytical signal
    (2020) Martínez Rojas, Francisco Javier; Castañeda Parra, Erik Alexander; Armijo Mancilla, Juan Francisco
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    Hierarchical surface texturing increases the contact-killing effect of marine bacteria Pseudomonas sp. on 316 L Stainless steel
    (2025) Castillo Lagos, Javiera Camila; Ramos Moore, Esteban; Castañeda Parra, Erik Alexander; Díaz, Donovan; Fernández Adell, José Ignacio; Vargas Cucurella, Ignacio Tomás; Pizarro Puccio, Gonzalo E.
    Bacterial attachment to material surfaces can lead to biofilm formation and corrosion, causing severe economic and health problems. Understanding the first step is crucial to proposing a surface that prevents bacterial adhesion and even obtaining bactericidal effects. In this study, photolithography and wet etching were used to texture stainless steel 316 L surfaces with a hierarchical pattern. The effects of texturing on the surfaces were characterized using atomic force microscopy, X-ray photoelectron spectroscopy, glow discharge optical emission spectroscopy, and contact angle analyses. Antimicrobial properties were assessed using a live/dead test performed on Pseudomonas sp. isolated from a marine environment. Our main results highlight that texturing using hierarchical patterns promotes changes in the chemical surface, wettability behavior, and antimicrobial response, highly depending on the length scale of the patterns.