Corrosion Rate and Mechanism of Degradation of Chitosan/TiO2 Coatings Deposited on MgZnCa Alloy in Hank's Solution.

Overly fast corrosion degradation of biodegradable magnesium alloys has been a major problem over the last several years. The development of protective coatings by using biocompatible, biodegradable, and non-toxic material such as chitosan ensures a reduction in the rate of corrosion of Mg alloys in simulated body fluids. In this study, chitosan/TiO2 nanocomposite coating was used for the first time to hinder the corrosion rate of Mg19Zn1Ca alloy in Hank's solution. The main goal of this research is to investigate and explain the corrosion degradation mechanism of Mg19Zn1Ca alloy coated by nanocomposite chitosan-based coating. The chemical composition, structural analyses, and corrosion tests were used to evaluate the protective properties of the chitosan/TiO2 coating deposited on the Mg19Zn1Ca substrate. The chitosan/TiO2 coating slows down the corrosion rate of the magnesium alloy by more than threefold (3.6 times). The interaction of TiO2 (NPs) with the hydroxy and amine groups present in the chitosan molecule cause their uniform distribution in the chitosan matrix. The chitosan/TiO2 coating limits the contact of the substrate with Hank's solution.

Determination of the Influence of Various Factors on the Character of Surface Functionalization of Copper(I) and Copper(II) Oxide Nanosensors with Phenylboronic Acid Derivatives.

In this work, we attempt to determine the influence of the oxidation state of copper [Cu(I) vs Cu(II)], the nature of the interface (solid/aqueous vs solid/air), the incubation time, and the structure of N-substituted phenylboronic acids (PBAs) functionalizing the surface of copper oxide nanostructures (NSs) on the mode of adsorption. For this purpose, 4-[(N-anilino)(phosphono)-S-methyl]phenylboronic acid (1-PBA) and its two analogues (2-PBA and bis{1-PBA}) and the copper oxide NSs were synthesized in a surfactant-/ion-free solution via a synthetic route that allows controlling the size and morphology of NSs. The NSs were characterized by scanning electron microscopy, ultraviolet-visible spectroscopy, Raman spectroscopy, and X-ray diffraction, which confirmed the formation of spherical Cu2O nanoparticles (Cu2ONPs) with a size of 1.5 µm to 600 nm crystallized in a cubic cuprite structure and leaf-like CuO nanostructures (CuONSs) with dimensions of 80-180 nm in width and 400-700 nm in length and crystallized in a monoclinic structure. PBA analogues were deposited on the surface of the copper oxide NSs, and adsorption was investigated using surface-enhanced Raman spectroscopy (SERS). The changes in the orientation of the molecule relative to the substrate surface caused by the abovementioned factors were described, and the signal enhancement on the copper oxide NSs was determined. This is the first study using vibrational spectroscopy for these compounds.

Corrosion Resistance of MgZn Alloy Covered by Chitosan-Based Coatings.

Chitosan coatings are deposited on the surface of Mg20Zn magnesium alloy by means of the spin coating technique. Their structure was investigated using Fourier Transform Infrared Spectroscopy (FTIR) an X-ray photoelectron spectroscopy (XPS). The surface morphology of the magnesium alloy substrate and chitosan coatings was determined using Scanning Electron Microscope (FE-SEM) analysis. Corrosion tests (linear sweep voltamperometry and chronoamperometry) were performed on uncoated and coated magnesium alloy in the Hank's solution. In both cases, the hydrogen evolution method was used to calculate the corrosion rate after 7-days immersion in the Hank's solution at 37 °C. It was found that the corrosion rate is 3.2 mm/year and 1.2 mm/year for uncoated and coated substrates, respectively. High corrosion resistance of Mg20Zn alloy covered by multilayer coating (CaP coating + chitosan water glass) is caused by formation of CaSiO3 and Ca3(PO4)2 compounds on its surface.

SERS activity and spectroscopic properties of Zn and ZnO nanostructures obtained by electrochemical and green chemistry methods for applications in biology and medicine.

This work for the first time evaluates the ability of homogeneous, stable, and pure zinc oxide nanoparticles (ZnONPs-GS) synthesized by "green chemistry" - an environmentally friendly, cheap, and easy method that allows efficient use of plant waste, such as banana peels, for the selective detection of four neurotransmitters present in body fluids and promotion of the SERS effect. Selective adsorption on ZnONPs-GS was compared with adsorption on the surface of (1) ZnONPs, which were obtained by electrochemical dissolution of zinc in a solution free of surfactants and (2) mechanically polished surface of bare Zn. The study showed that SERS spectroscopy using unique marker bands allows distinguishing whether the adsorbate is deposited on the surface of zinc or zinc oxide. Thus, the combination of the SERS technique with an optical probe can allow an in vivo determination of the condition of galvanized implants. The use of SERS has been extended to monitor the photocatalytic properties of surface-functionalized ZnO nanoparticles. It has been shown that despite the same structure, purity, and adsorption properties, ZnONPs-GS obtained using "green chemistry" are more bio-friendly for biological material than those obtained by the electrochemical method. This is because the surface of ZnONPs-GS is free of hydroxyl groups, which can easily form reactive oxygen species when the surface is exposed to visible radiation. Thus, surface-functionalized ZnONPS-GS can protect the biological material from the damage caused by the production and attack of an excess of ROS. Also, for an exemplary neurotransmitter, structural changes when it is not-covalently bound to Zn/ZnO were compared with the structural changes of this neurotransmitter deposited on the surface of various metals (Cu, α-Ti, and α-Fe) and metal oxides (leaf-like CuO, rutile-TiO2, and γ-Fe2O3). It has been shown that adsorption only slightly depends on the type of metallic surface and the development of this surface for roughness up to 1 micron. Metal substrates were characterized before and after the neurotransmitters' adsorption. UV-Vis, Raman, and ATR-FTIR confirmed the formation of ZnO nanoparticles. XRD showed a high crystalline structure of wurtzite. TEM and DLS showed that nanoparticles are spherical, well dispersed, and have a uniform size.

Ions-free electrochemically synthetized in aqueous media flake-like CuO nanostructures as SERS reproducible substrates for the detection of neurotransmitters.

The process of catalytic destruction of tumor cells can be strengthened by introducing copper(II) oxide nanostructures (CuONSs) with receptor's agonists/antagonists immobilized on their surface. Here we show a simple and reliable electrochemical method for the fabrication ions-free flake-like CuO nanostructures in a surfactant/ions free aqueous environment. For the determination of the metal surface plasmon, size, rheology, and structure of the fabricated nanostructures ultraviolet-visible (UV-Vis), Fourier-transform infrared (FT-IR), Raman, and X-ray photoelectron (XPS) spectroscopies as well as scanning electron microscope (SEM), high-resolution transmission electron microscopy with energy dispersive X-ray (HDTEM-EDS), X-ray powder diffraction (XRD), and dynamic light scattering (DLS) analysis were used. The fabricated nanostructures were used as highly sensitive, uniform, and reproducible sensors of a natural ligand (bombesin) of some types of metabotropic seven transmembrane G protein-coupled superfamily receptors (GPCRs), which are over-express on the surface of many malignant tumors. Surface-enhanced Raman scattering (SERS) was used to monitor the geometry of adsorbate, separate, enrich, and detect various bombesin C-terminal fragments. It has been shown that the type of used substrate, surface development, and ions present in the solution have little effect on the mode of adsorption.

Electrochemical synthesis of magnetic iron oxide nanoparticles with controlled size.

We present a novel and facile method enabling synthesis of iron oxide nanoparticles, which are composed mainly of maghemite according to X-ray diffraction (XRD) and Mössbauer spectroscopy studies. The proposed process is realized by anodic iron polarization in deaerated LiCl solutions containing both water and ethanol. Water seems to play an important role in the synthesis. Morphology of the product was studied by means of transmission electron microscopy and XRD. In the solution containing almost 100% of water a black suspension of round shaped maghemite nanoparticles of 20-40 nm size is obtained. Regulating water concentration allows to control nanoparticle size, which is reduced to 4-6 nm for 5% of water with a possibility to reach intermediate sizes. For 3% or lower water concentration nanoparticles are of a needle-like shape and form a reddish suspension. In this case phase determination is problematic due to a small particle size with the thickness of roughly 3 nm. However, XRD studies indicate the presence of ferrihydrite. Coercivities of the materials are similar to those reported for nanoparticle magnetite powders, whereas the saturation magnetization values are considerably smaller.