Electrochemical Synthesis and Analytical Characterization of Hybrid Zinc/Calcium Antimicrobial Nano-Oxides for Cultural Heritage Applications

The present study proposes the one-step synthesis of Zn/Ca hybrid nano-oxides combining an electrochemical route to ZnO nanostructures (NSs) with the wet chemical production of Ca(OH)(2) NSs. ZnO is a known antimicrobial and Ca(OH)(2) has consolidating properties, both appealing for stone artwork preservation in the field of cultural heritage. Two concentrations of the electrolytic bath (NaOH 0.1 and 0.4 M) were studied resulting in distinct final nanomaterials (Zn-Ca0.1 and Zn-Ca0.4). Fourier transform infrared, X-ray photoelectron spectroscopies, and transmission electron microscopy demonstrated that Zn-Ca0.1 consisted of lamellar calcium hydroxyzincate NSs, whereas Zn-Ca0.4 showed hexagonal Ca(OH)(2) (similar to 500 nm) and ZnO (similar to 50 nm) NSs. Nanocoatings prepared with Zn-Ca0.1 exhibited a Zn2+ release increasing up to 1 mu mol cm(-2) in 24 h. Instead, Zn-Ca0.4-based nanocoatings released a constant value of about 0.35 mu mol/cm(2). Both types of nanocoatings showed good antimicrobial activity against Bacillus subtilis after 48 h and hydrophilic behavior over 28 days.