Enhanced Electrochemical Cu Release from Commercial Cu-Sn Alloys: Fate of the Alloying Elements in Artificial Perspiration

Effects of Ageing in Disinfectant Solution on the Corrosion Resistance and Antimicrobial Behavior of Copper Alloys

This work studies two copper-based alloys as potential antimicrobial weapons for sectors where surface hygiene is essential. Effects of different alloying elements addition at the same Cu content (92.5% by weight) on the corrosion resistance and the antibacterial performance of two copper alloys were studied in an aerated disinfectant solution (0.25% v/v Aniosurf Premium (D)) by electrochemical corrosion, X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectroscopy (ToF-SIMS) and antibacterial tests. Results showed that the nature of the alloying elements had a clear influence on the corrosion resistance and antibacterial performance. Electrochemical impedance results and surface analyses demonstrate the presence of organic compounds bound on the substrate and that a film covers part of the total active surface and may act as a protective barrier by preventing the interaction between metal and solution, decreasing the antimicrobial performance of copper-based materials. Low zinc and silicon contents in copper alloys allows for better aging behavior in D solution while maintaining good antibacterial performance. The XPS and ToF-SIMS results indicated that artificial aging in disinfectant enhanced Cu enrichment in the organic film formed, which could effectively stimulate the release of Cu ions from the surface.

A Tribological and Ion Released Research of Ti-Materials for Medical Devices

The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can release metal ions or particles harmful to human health. The mechanisms are not well understood yet and may involve wear and/or corrosion. Therefore, in this work, commercial pure titanium and a Ti-6Al-4V alloy were investigated before and after being exposed to a simulated biological fluid through tribological tests, surface analysis, and ionic dissolution characterization by ICP-AES. Before exposure, X-ray diffraction and optical microscopy revealed equiaxed α-Ti in both materials and β-Ti in Ti-6Al-4V. Scratch tests exhibited a lower coefficient of friction for Ti-6Al-4V alloy than commercially pure titanium. After exposure, X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy results showed an oxide film formed by TiO₂, both in commercially pure titanium and in Ti-6Al-4V, and by TiO and Al₂O₃ associated with the presence of the alloys. Furthermore, inductively coupled plasma atomic emission spectroscopy revealed that aluminum was the main ion released for Ti-6Al-4V, giving negligible values for the other metal ions.

Effect of TiO2 Concentration on Microstructure and Properties of Composite Cu-Sn-TiO2 Coatings Obtained by Electrodeposition

In this work, Cu–Sn–TiO₂ composite coatings were electrochemically obtained from a sulfate bath containing 0–10 g/L of TiO₂ nanoparticles. The effect of TiO₂ particles on kinetics of cathodic electrodeposition has been studied by linear sweep voltammetry and chronopotentiometry. As compared to the Cu–Sn alloy, the Cu–Sn–TiO₂ composite coatings show rougher surfaces with TiO₂ agglomerates embedded in the metal matrix. The highest average amount of included TiO₂ is 1.7 wt.%, in the case of the bath containing 5 g/L thereof. Composite coatings showed significantly improved antibacterial properties towards E. coli ATCC 8739 bacteria as compared to the Cu–Sn coatings of the same composition. Such improvement has been connected with the corrosion resistance of the composites studied by linear polarization and electrochemical impedance spectroscopy. In the bacterial media and 3% NaCl solutions, Cu–Sn–TiO₂ composite coatings have lower corrosion resistance as compared to Cu–Sn alloys, which is caused by the nonuniformity of the surface.

Efficient photoelectrochemical CO2 conversion for selective acetic acid production

Amidst the development of photoelectrochemical (PEC) CO₂ conversion toward practical application, the production of high-value chemicals beyond C₁ compounds under mild conditions is greatly desired yet challenging. Here, through rational PEC device design by combining Au-loaded and N-doped TiO₂ plate nanoarray photoanode with Zn-doped Cu₂O dark cathode, efficient conversion of CO₂ to CH₃COOH has been achieved with an outstanding Faradaic efficiency up to 58.1% (91.5% carbon selectivity) at 0.5 V vs. Ag/AgCl. Temperature programmed desorption and in situ Raman spectra reveal that the Zn-dopant in Cu₂O plays multiple roles in selective catalytic CO₂ conversion, including local electronic structure manipulation and active site modification, which together promote the formation of intermediate *CH₂/*CH₃ for C-C coupling. Apart from that, it is also unveiled that the sufficient electron density provided by the Au-loaded and N-doped TiO₂ plate nanoarray photoanode plays an equally important role by initiating multi-electron CO₂ reduction. This work provides fresh insights into the PEC system design to reach the multi-electron reduction reaction and facilitate the C-C coupling reaction toward high-value multicarbon (C₂₊) chemical production via CO₂ conversion.

Ultrasonic-assisted electrodeposition of Cu-Sn-TiO2 nanocomposite coatings with enhanced antibacterial activity

Copper-based coatings are known for their high antibacterial activity. In this study, nanocomposite Cu-Sn-TiO₂ coatings were obtained by electrodeposition from an oxalic acid bath additionally containing 4 g/dm³ TiO₂ with mechanical and ultrasonic agitation. Ultrasound treatment was performed at 26 kHz frequency and 32 W/dm³ power. The influence of agitation mode and the current load on the inclusion and distribution of the TiO₂ phase in the Cu-Sn metallic matrix were evaluated. Results indicated that ultrasonic agitation decreases agglomeration of TiO₂ particles and allows for the deposition of dense Cu-Sn-TiO₂ nanocomposites. It is shown that nanocomposite Cu-Sn-TiO₂ coatings formed by ultrasonic-assisted electrodeposition exhibit excellent antimicrobial properties against E. coli bacteria.

Spinel Zn3V3O8 nanosheets via a one-step hydrothermal synthesis with peroxidase-like activity for high sensitivity glucose colorimetric detection in synthetic perspiration

Due to their specific spinel structure, ternary oxides with multi-catalytic sites on a highly active exposed surface are recommended as alternative bio-catalysts. Spinel zinc vanadate with two-dimensional nanosheets (Zn3V3O8 NSs) was synthesised using a one-step hydrothermal route with CTAB and glycine as a bi-surfactant, where each NS has a thin thickness (25 nm) and wide cross section (2 μm). As a key parameter for peroxidase-like activity, the Michaelis-Menten constant (Km) for Zn3V3O8 NSs was calculated to be 0.271 mM with TMB and 1.317 mM with H2O2 at optimum conditions, indicating a higher affinity for the exposed (011) facet towards horseradish peroxidases. This affinity is related to the geometric matching between V4+ active sites and the terminal amino groups of TMB. The V4+ ions on the (011) facet act as dangling bonds and readily react with H2O2 in a Fenton-like reaction. The peroxidase-like activity for Zn3V3O8 NSs is verified by the formation of [V(IV)-OO˙] by the ˙O2- and V5+ near V4+ sites, but oxidase activity for Zn3V3O8 NSs. Based on the peroxidase-like activity, Zn3V3O8 NSs were used as a colorimetric glucose sensor with a wide linear range from 0.01 to 0.5 mM and a detection limit (LOD = 3σ/S) of 2.81 × 10-7 M. The colorimetric sensor also exhibited high accuracy and selectivity in synthetic perspiration samples.

The Protection Role of Cysteine for Cu-5Zn-5Al-1Sn Alloy Corrosion in 3.5 wt.% NaCl Solution

In this work, the corrosion mechanism of a Cu-5Zn-5Al-1Sn alloy was examined in a 3.5 wt.% NaCl solution. At the same time, the effect of a cysteine inhibitor was also investigated through a multi-analytical approach. Electrochemical results suggested that inhibition efficiency increased with the increase of cysteine concentration. From potentiodynamic polarization (PD) analysis, a decrease in corrosion current and corrosion potential shift toward a more negative direction was observed. The potential difference between the blank and inhibited surface was found to be 46 mV, which is less than 85 mV, revealing a mixed type inhibition effect of cysteine for the Cu-5Zn-5Al-1Sn alloy. The inhibition mechanism of cysteine (Cys) and the effect of alloying elements were investigated by fitting experimental impedance data according to a projected equivalent circuit for the alloy/electrolyte interface. A Langmuir adsorption isotherm was proposed to explain the inhibition phenomenon of cysteine on the Cu-5Zn-5Al-1Sn alloy surface. Surface morphology observation confirmed that the Cu-5Zn-5Al-1Sn alloy was damaged in 3.5 wt.% NaCl solution and could be inhibited by using the cysteine inhibitor. The impact of alloying elements on the corrosion mechanism was further examined by surface analysis techniques such as X-Ray photoelectron spectroscopy (XPS)/Auger spectra, the results of which indicated that the corrosion inhibition was realized by the adsorption of the inhibitor molecules at the alloy/solution interface.

A literature review of in situ transmission electron microscopy technique in corrosion studies

One of the biggest challenges in corrosion investigation is foreseeing precisely how and where materials will degenerate in a designated condition owing to scarceness of accurate corrosion mechanisms. Recent fast development of in situ transmission electron microscopy (TEM) technique makes it achievable to better understand the corrosion mechanism and physicochemical processes at the interfaces between samples and gases or electrolytes by dynamical capture the microstructural and chemical changes with high resolution within a realistic or near-realistic environment. However, a detailed and in-depth account summing up the development and latest achievements of in situ TEM techniques, especially the application of emerging liquid and electrochemical cells in the community of corrosion study in the last several years is lacking and is urgently needed for its heathy development. To fill this gap, this critical review summarizes firstly the key scientific issues in corrosion research, followed by introducing the configurations of several typical closed-type cells. Then, the achievements of in situ TEM using open-type or closed-type cells in corrosion study are presented in detail. The study directions in the future are commented finally in terms of spatial and temporal resolution, electron radiation, and linkage between microstructure and electrochemical performance in corrosion community.