Fabrizio Caprioli

Copper protection by self-assembled monolayers of aromatic thiols in alkaline solutions

Copper corrosion in alkaline solutions is inhibited by the formation of self-assembled monolayers of aromatic thiols, made of either benzenethiol or 2-naphthalenethiol or 4-acetamidothiophenol. Electrochemical experiments, based on voltammetry and impedance spectroscopy, point out the much lower reactivity of copper surfaces towards oxidation, when covered by compact adlayers of the above molecules bonded through the S atom. The peculiar shape and peak position in the voltammetric reduction of residual oxides grown on modified metal surfaces suggest that they are due to Cu(I) suboxides, probably grown on reactive metal defects. XPS experiments have confirmed that the aromatic adlayers are still covering most of the Cu surface even after 1 h immersion in 0.5 M NaOH. The main changes in Auger and XP spectra indicate the formation of much less Cu(2)O in the protected samples than in the corresponding bare Cu aged in NaOH. From the experimental data the presence of defective copper oxides on modified Cu has been deduced.

Electrochemically deposited ZnO films: an XPS study on the evolution of their surface hydroxide and defect composition upon thermal annealing

Electrodeposition from ZnCl2 aqueous solution was performed to grow ZnO thin films on the surface of polycrystalline copper plates. Electrochemical parameters for deposition were optimized by means of cyclic voltammetry (CV). The morphology of the deposits was studied via scanning electron microscopy (SEM), and their chemical composition was ascertained by means of X-ray photoelectron spectroscopy (XPS). The effects of changing the deposition bath temperature (Tbath) and the role played by post-deposition treatments, such as temperature and time of annealing in air, were studied. SEM images of freshly deposited vs. annealed samples have shown that in the former case the films display a rough morphology with mixed grain/hexagonal platelets structures and in the latter smaller but more uniformly dispersed cubic grains. Tbath is found to be the key parameter to induce the different morphology in the deposited films, which reflects in a different chemical reactivity of surface species, as found on the basis of the binding energies and relative quantitative ratios between Zn 2p and O 1s peaks. In fact, a higher Tbath favours a more efficient desorption of OH groups upon annealing, the O 1s peak resulting to much more drastically modified oxide/hydroxide intensity ratio with respect to the case of the sample deposited at lower Tbath.

Wet Adhesion of Buckypaper Produced from Oxidized Multiwalled Carbon Nanotubes on Soft Animal Tissue

Buckypaper (BP) is the general definition of a macroscopic assembly of entangled carbon nanotubes. In this paper, a new property of a BP film produced from oxidized multiwalled carbon nanotubes was investigated. In particular, BP shows to be able to promptly and strongly adhere to animal internal soft and wet tissues, as evaluated by peeling and shear tests. BP adhesion strength is higher than that recorded for a commercial prosthetic fabric (sealed to the tissue by fibrin glue) and comparable with that of other reported optimized nanopatterned surfaces. In order to give an interpretation of the observed behavior, the BP composition, morphology, porosity, water wettability, and mechanical properties were analyzed by AFM, X-ray photoelectron spectroscopy, wicking tests, contact angle, and stress-strain measurements. Although further investigations are needed to assess the biocompatibility and safety of the BP film used in this work, the obtained results pave the way for a possible future use of buckypaper as adhesive tape in abdominal prosthetic surgery. This would allow the substitution of conventional sealants or the reduction in the use of perforating fixation.