Epoxy-silica/clay nanocomposite for silver-based antibacterial thin coatings: structure and ionic mobility
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ORIGINAL PAPER
Epoxy-silica/clay nanocomposite for silver-based antibacterial thin coatings: structure and ionic mobility Hugo Fernando Giraldo Mejía 1 & Emilio Jiménez-Piqué 2 & Matías Valdés 1 & Raúl Procaccini 1 & Sergio Pellice 1 Received: 30 March 2020 / Revised: 21 July 2020 / Accepted: 22 July 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract A novel material was developed using sol-gel chemistry and an environmental-friendly grafting process of clay nanoparticles. In a previous work of our group, highly compact coatings had been generated using silicon alkoxides, as tetraethoxysilane (TEOS) and 3-glycidoxypropyl-trimethoxysilane (GPTMS), with the incorporation of silver ions and synthetic smectite-type clay nanoparticles, demonstrating antibacterial behaviour against Escherichia coli cultures. By controlling the loading, the exfoliation and the grafting processes of the clay nanoparticles, it was possible to control the migration kinetics of silver ions from the coating matrix to the surface. Morphological and structural studies, through SEM-FIB, revealed the effect of clay nanoparticles leading to the development of a homogeneous structure in 2-μm thickness coatings. Grazing incidence small angle X-ray scattering (GISAXS) experiments demonstrated that silver is distributed in a strongly anisotropic arrangement when clay nanosheets are absent. The size of the silver particles developed on the surface is rather different from that of those developed in the bulk of the coating. Scattering patterns also revealed that the incorporation of clay nanosheets promotes the development of less anisotropic structures. Electrochemical impedance spectroscopy (EIS) measurements confirmed the integrity of the material and the applicability of a physical model with normal distribution of resistive and capacitive elements. Keywords Sol-gel . Silanization . Ionic mobility . GISAXS . EIS
Introduction Materials science plays a key role in the development of antimicrobial materials that help to solve different health issues [1–4]. It provides a wide variety of synthesis methods and deposition techniques. Nowadays, sol-gel chemistry is no longer an exploratory method and has positions itself as a synthesis route to obtain hybrid materials. These silica-based inorganic systems avoid thermal instability and present the advantage of good mechanical properties [5, 6]. The incorporation of silver ions into these materials provides a highly beneficial property: the antimicrobial effect. It has been
* Raúl Procaccini [email protected] 1
Instituto de Investigación en Ciencia y Tecnología de Materiales (INTEMA), CONICET-UNMdP, Av. Colón 10850, 7600 Mar del Plata, Argentina
2
Departament de Ciència dels Materials i Enginyeria Metallúrgica, Universitat Politècnica de Catalunya, Avda. Diagonal, 647 (ETSEIB), 08028 Barcelona, Spain
demonstrated that, even for low silver contents (less than 5%), silver-loaded materials present good enough antibacterial behaviour, avoiding possible problems associated wi
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