Electrochemical and corrosion properties of ZnO/Zn electrode in atmospheric environments

Photocatalytic activity and photoelectrochemical properties of Ag/ZnO core/shell nanorods under low-intensity white light irradiation

Zinc oxide (ZnO) nanorod thin films were prepared by CBD onto glass and FTO/glass substrates. Silver (Ag) nanoparticles were synthesized on the surface of the prepared ZnO nanorod thin films using electrochemical methods. The scanning electron microscopy images of the Ag/ZnO/glass core/shell nanostructure confirmed that the average particles size is 20 nm while it was 41 nm for Ag NPs that synthesized onto ZnO/FTO NRs. The photocatalytic activity of the prepared Ag/ZnO core/shell nanostructure was studied by analyzing the degradation of methylene blue (MB) dye under visible light. Various pH values (6 and 10) and exposure time (30-240) min were controlled to investigate the photocatalytic activity of as-prepared Ag/ZnO core/shell nanostructure and that annealed at 200 °C and 300 °C for 1 h. It was observed that when the pH was 6, the degradation rate increased with the annealing temperature and irradiation time reaching 51% at the annealing temperature of 300 °C and exposure time of 240 min. In other hands, when the pH was 10, and the sample was annealed at 200 °C, it showed a good degradation rate of 100% at the irradiation time of 90 min. By contrast, the sample annealed at 300 °C required 180 min to degrade the MB dye completely. The photoelectrochemical cell measurement based on photocurrent density revealed a slight response to light. Cycle voltammetry (CV) measurement was conducted, and the CV curves of the Ag/ZnO core/shell electrodes indicated nonfaradaic and pseudocapacitance behavior. The electrodes showed nearly rectangular CV curves, which indicated the dominance of the nonfaradaic capacitance behavior. The specific capacitance of the electrodes remained at approximately 99%. Mott-Schottky analysis revealed that the semiconductor was an n-type with dependence on flat band potential V _FB deviation in the negative direction.

Strong Volta potential change in doped zinc oxide as a photoresponse to UV irradiation

Doped ZnO thin films on ITO substrates were prepared by reactive co-sputtering of ZnO and several dopant metals, namely Al, Mn, Ti, W or Zr. To elucidate the influence of the dopant, morphological and compositional investigations were performed applying SEM/EDX, XRD and AFM. The optical band gaps of the materials were determined by UV-VIS measurements and the subsequent analysis of the derived Tauc plots. SKP (Scanning Kelvin Probe) measurements were performed under alternating illumination periods in order to measure the CPD (contact potential difference) response on UV irradiation; effective donor concentrations were calculated from the SKP results. The obtained X-ray diffractograms revealed that W : ZnO is amorphous, whereas all other dopants form crystalline structures with diffraction angles shifted towards lower values. SEM and AFM imaging revealed a significant influence of the dopant on the film morphology. The optical band gap values are in the range of the ZnO value (∼3.30 eV), with the lowest value of 3.29 eV being measured for Mn : ZnO. An exception was found for W : ZnO, which exhibits significant band gap widening reaching 4.35 eV. The effective donor concentrations are low for all samples under dark conditions, whereas they showed enhanced values under illumination. The sensitivity of all materials towards illumination makes them promising candidates for future research activities in the field of photovoltaics.

Doped ZnO thin films on ITO substrates were prepared by reactive co-sputtering of ZnO and several dopant metals, namely Al, Mn, Ti, W or Zr.

The Prospects for Biodegradable Zinc in Wound Closure Applications

Zinc is identified as a promising biodegradable metal along with magnesium and iron. In the last 5 years, considerable progress is made on understanding the mechanical properties, biodegradability, and biocompatibility of zinc and its alloys. A majority of these studies have focused on using zinc for absorbable cardiovascular and orthopedic device applications. However, it is likely that zinc is also suitable for other biomedical applications. In this work, the prospects for zinc in the fabrication of wound closure devices such as absorbable sutures, staples, and surgical tacks are critically assessed, with the aim of inspiring future research on biodegradable Zn for this medical application.

The influence of alloying and fabrication techniques on the mechanical properties, biodegradability and biocompatibility of zinc: A comprehensive review

Zinc has been identified as one of the most promising biodegradable metals along with magnesium and iron. Zinc appears to address some of the core engineering problems associated with magnesium and iron when applied to biomedical implant applications; hence the increase in the amount of research investigations on the metal in the last few years. In this review, the current state-of-the-art on biodegradable Zn, including recent developments, current opportunities and future directions of research are discussed. The discussions are presented with a specific focus on reviewing the relationships that exist between mechanical properties, biodegradability, and biocompatibility of zinc with alloying and fabrication techniques. This work hopes to guide future studies on biodegradable Zn that will help in advancing this field of research. STATEMENT OF SIGNIFICANCE: (i) The review offers an up-to-date and comprehensive review of the influence of alloying and fabrication technique on mechanical properties, biodegradability and biocompatibility of Zn; (ii) the work cites the most relevant biodegradable Zn fabrication processes including additive manufacturing techniques; (iii) the review includes a listing of research gap and future research directions for the field of biodegradable Zn.

Influence of macroscopic defects on the corrosion behavior of U-0.79 wt%Ti alloy in sodium chloride solution

Uranium alloys containing a low concentration of titanium have received wide attention due to their greatly enhanced corrosion resistance and outstanding mechanical performances. Herein, we investigated the effect of macroscopic defects on the corrosion behavior of U-0.79 wt%Ti (denoted as U-Ti) alloy in 0.01 M NaCl solution using traditional electrochemical testing technologies and a novel scanning electrochemical composite probe (SECP). The results demonstrate that pitting corrosion occurs rapidly on the alloy surface due to macroscopic defects. Moreover, macroscopic defects led to a decrease in corrosion potential and polarization resistance, and an increase in corrosion current density. Furthermore, the potential and pH value distributions were detected in the same region using the composite probe. The results show that the region around the macroscopic defects become corrosion-active positions and the potential difference (vs. the average potential of the alloy surface) in this area is significantly higher than that at positions without macroscopic defects, while the opposite was observed for the pH value distribution. In addition, the distribution of the vertical direction (Z) potential at the active point was clearly different from that at the inactive point. A possible reason for this could lie in the difference in the electric field distribution and electrode reaction type between the active point and inactive point on the alloy surface.

Evolution of the in vitro degradation of Zn–Mg alloys under simulated physiological conditions

Primary reactions occurring upon Zn-derived materials insertion inside an organism are of utmost importance as chemical species resulting from the degradation of resorbable biomaterials are crucial for the interaction with the surrounding tissues.

In vitro corrosion behaviour and anti-Candida spp. activity of Zn coated with ZnO-nanostructured 'Anastacia' flowers

Rejection and colonization by microbes are two problematic issues that often require the surgical removal of medical implants with increased risks for patients. In this work it is shown that functionalization of Zn surfaces with ZnO-nanostructured 'Anastacia' flowers (NAF) resulted in improved biomaterials that can potentially overcome these important drawbacks, which can further boost the use of Zn in biomedical implants. The in vitro degradation of NAF-coated Zn under simulated physiological conditions resulted in the formation of a biomimetic corrosion layer rich in a hydroxyapatite analogue that, being an important bone component, may potentially decrease implant rejection. Colonization of the NAF-coated Zn surface by Candida parapsilosis and Candida albicans, two of the more relevant microbial species colonizing medical devices, was significantly reduced on the NAF-coated Zn surface. The mechanism by which this colonization inhibition occurred was distinct since for C. parapsilosis cells this was attributed to reduced cell viability, while for C. albicans the reduced colonization was related to impaired biofilm formation. This ZnO-derived coating is an expeditious strategy to improve the resilience of Zn-based resorbable biomaterials towards Candida spp. colonization, paving the way for the design of bioactive ZnO-derived coatings with potential for clinical applications on bone.

Fabrication of novel TiO2 nanoparticles/Mn(III) salen doped carbon paste electrode: application as electrochemical sensor for the determination of hydrazine in the presence of phenol

Hydrazine and phenol are two important environmental pollutants. In this work, an electrochemical sensor for the selective and sensitive detection of hydrazine in presence of phenol was developed by the bulk modification of carbon paste electrode (CPE) with TiO2 nanoparticles and Mn(III) salen. Large peak separation, good sensitivity, and stability allow this modified electrode to analyze hydrazine individually and simultaneously along with phenol. Applying square wave voltammetry (SWV), a linear dynamic range of 3 × 10(-8)-4.0 × 10(-4) M with detection limit of 10.0 nM was obtained for hydrazine. Finally, the proposed method was applied to the determination of hydrazine and phenol in some real samples.