Zn-based Materials Research Articles

A review on the mechanical and biocorrosion behaviour of iron and zinc-based biodegradable materials fabricated using powder metallurgy routes

Abstract Over the past two decades, research on alloys and composites based on Mg, Fe, and Zn has focused on biodegradable orthopaedic implants. Mg-based materials face issues like excessive corrosion rates and hydrogen gas evolution, while Fe and Zn-based materials show lower corrosion rates. However, these rates are slower than the optimal rate, which can be modified using powder metallurgy (PM) manufacturing. The PM process offers precise control over porosity distribution which in turn affects the mechanical and corrosion properties of the fabricated specimen. The highest rate of corrosion i.e. 0.944 mmpy was observed with the alloying of 2 wt% Pd in Fe and by using conventional sintering technique. Similarly, Zn-based samples fabricated by conventional sintering was found to exhibit higher corrosion rate as compared to microwave and spark plasma sintered specimen. PM-fabricated Fe and Zn-based bone scaffolds have been investigated for in-vitro corrosion and osseointegration. A higher porosity in the Fe and Zn scaffolds (>60 %) resulted in high corrosion rate which adversely impacted the cell proliferation. This timely review critically assessed PM-fabricated Fe and Zn-based materials that have the potential to transform regenerative medicine and patient care by redefining the field of biodegradable implants.

Self-templated formation of ZnNC microtube with high oxygen reduction reaction overpotential for Zn-based catalyst

The synthesis of hollow morphologies without employing templates and addressing the high overpotential of the oxygen reduction reaction in Zn-N4-C-based materials poses a significant challenge. In this study, we present a straightforward yet robust approach based on a self-templated metal-organic framework (MOF-based) to synthesize ZnNC microtubes and explore the reason behind its high oxygen reduction (ORR) overpotential through density functional theory (DFT) calculation. ZnNC microtubes, benefiting from the abundant Zn-N4 active sites, hierarchical porosity, and a reasonable degree of graphitization, exhibited superior ORR activity and methanol tolerance compared to the traditional precious Pt/C catalyst. On the other hand, DFT calculation shows that Zn exhibits a d10 electronic configuration and diamagnetic nature in Zn-N4 moieties confirmed by the partial density of state (PDOS), hence the main reason behind the high ORR overpotential. This study provides a novel roadmap for further engineering efforts to achieve an ideal ORR catalyst in Zn-based materials.

Corrosion Resistance of Biodegradable Zinc Surfaces Enhanced by UV-Grafted Polydimethylsiloxane Coating.

Improved living conditions have led to an increase in life expectancy worldwide. However, as people age, the risk of vascular disease tends to increase due to the accumulation and buildup of plaque in arteries. Vascular stents are used to keep blood vessels open. Biodegradable stents are designed to provide a temporary support vessel that gradually degrades and is absorbed by the body, leaving behind healed blood vessels. However, biodegradable metals can suffer from reduced mechanical strength and/or inflammatory response, both of which can affect the rate of corrosion. Therefore, it is essential to achieve a controlled and predictable degradation rate. Here, we demonstrate that the corrosion resistance of biodegradable Zn surfaces is improved by electroless deposition of zinc hydroxystannate followed by UV-grafting with silicone oil (PDMS). Potentiodynamic polarization, electrochemical impedance spectroscopy, respiratory kinetic measurements, and long-term immersion in three simulated body fluids were applied. Although zinc hydroxystannate improves the corrosion resistance of Zn to some extent, it introduces a high surface area with hydroxyl units used to UV-graft PDMS molecules. Our results demonstrate that hydrophobic PDMS causes a 3-fold reduction in corrosion of Zn-based materials in biological environments and reduces cytotoxicity through the uncontrolled release of Zn ions.

Quaternary Zinc Alloys with Magnesium, Calcium and Strontium after Hydrostatic Extrusion-Microstructure and Its Impact on Mechanical and Corrosion Properties.

The development of bioabsorbable implants from Zn alloys is one of the main interests in the new generation of biomaterials. The main drawbacks of Zn-based materials are their insufficient mechanical properties. In the presented studies, a quaternary alloy composed of zinc with magnesium (0.2-1 wt. %), calcium (0.1-0.5 wt. %) and strontium (0.05-0.5 wt. %) was prepared by gravity casting followed by hot extrusion and then by hydrostatic extrusion. Microstructural characterization using scanning electron microscopy (SEM) and X-ray diffraction (XRD) phase analysis was performed. The mechanical properties were examined, using static tensile tests. Corrosion properties were analyzed using immersion tests. Samples were immersed in Hanks' solution (temperature = 37 °C, pH = 7.4) for 14 days. All alloys were subjected after corrosion to SEM observations on the surface and cross-section. The corrosion rate was also calculated. The microstructure of the investigated quaternary alloy consists of the α-Zn grains and intermetallic phases Mg2Zn11, CaZn13 and SrZn13 with different grain sizes and distribution, which impacted both mechanical and corrosion properties. Thanks to the alloying by the addition of Mg, Ca, and Sr and plastic deformation using hydrostatic extrusion, outstanding mechanical properties were obtained along with improvement in uniformity of corrosion rate.

Microstructure-properties relation of hydrostatically extruded absorbable zinc alloys: Effect of Mg and Cu addition on corrosion properties and biocompatibility

Pure Zn is well-known for its appropriate corrosion rate, making it suitable for use as future absorbable implants. Yet, it suffers from insufficient strength, thus, both plastic deformation and alloying are required. Hydrostatic extrusion has proven to be an efficient technique, providing high mechanical properties for zinc alloys. However, its effect on degradation rate and biocompatibility of Zn alloys remains unknown. Thus, within the present study, an attempt to evaluate those properties has been made on hydrostatically extruded pure Zn, Zn–Mg and Zn–Mg–Cu alloys. The materials were characterized by advanced microscopy techniques and uniaxial tensile tests. Corrosion properties were assessed based on electrochemical and static immersion tests. Finally, the cytotoxic effect of zinc extracts on endothelial cells were examined by standard MTT assays combined with confocal imaging.The results showed that hydrostatic extrusion results in significant refinement of α-Zn grains and the intermetallic phase Mg2Zn11 for the investigated alloys. The alloys exhibited ultimate tensile strength exceeding 300 MPa and elongation higher than 20%. Corrosion tests demonstrated that all the materials showed a similar level of degradation rate. Moreover, the uniform distribution of the intermetallic phase contributed to homogeneous corrosion of Zn alloys. Biological studies indicated that the least cytotoxic response in endothelial cells was obtained for the Zn–Mg alloy. Such an effect was caused by the limited amount of released Zn ions in the favor of Mg ions.The refinement of α-Zn grains and intermetallic phases caused by hydrostatic extrusion were key factors determining the performance of Zn-based materials.

Maximizing the potential of commercial zinc stearate for one-pot esterification and transesterification for high-acidity biodiesel production

Meeting the growing demand for energy while combating the adverse effects of global warming remains challenging today, and biodiesel offers a potential solution to help mitigate the impact of global warming. In this scenario, our primary goal was to optimize biodiesel production from highly acidic soybean oil using a one-pot esterification and transesterification process, addressing the challenges associated with high-acidity substrates. To start, X-ray Diffraction (XRD) guaranteed us just one phase for each commercial catalyst, and we conducted catalytic experiments to select the most suitable Zn-based material for the process, choosing zinc stearate (ZnSt2) as the best candidate. Our study demonstrated that a nano-sized zinc oxide (ZnO) catalyst, which was anticipated to be the most suitable choice, did not exhibit optimal performance. Subsequently, a Full Factorial Design of Experiments (DOE) was employed to optimize reaction parameters, specifically, the reaction temperature and the oil-to-methanol (O:M) molar ratio. The results consistently showed that increased O:M ratio and temperature promoted enhanced fatty acid methyl esters (FAME) production and reduced acidity. Then, experiments were conducted to maximize FAME production and minimize free fatty acid (FFA) content. The results showed that increasing the catalyst concentration from 5 wt% to 10 wt% did not significantly impact FAME production or acidity reduction. Also, while increased methanol should theoretically enhance FAME production and reduce acidity, the results were inconsistent across all experiments. Excess methanol interfered with glycerol separation, leading to decreased FAME yield. Thus, this study underscores the complexity of biodiesel production and highlights the importance of selecting suitable catalysts and optimizing process parameters.

Fabrication of a Nanoscale Magnesium/Copper Metal-Organic Framework on Zn-Based Guided Bone Generation Membranes for Enhancing Osteogenesis, Angiogenesis, and Bacteriostasis Properties.

Recently, zinc (Zn) and its alloys have demonstrated great potential as guided bone regeneration (GBR) membranes to treat the problems of insufficient alveolar bone volume and long-term osseointegration instability during dental implantology. However, bone regeneration is a complex process consisting of osteogenesis, angiogenesis, and antibacterial function. For now, the in vivo osteogenic performance and antibacterial activity of pure Zn are inadequate, and thus fabricating a platform to endow Zn membranes with multifunctions may be essential to address these issues. In this study, various bimetallic magnesium/copper metal-organic framework (Mg/Cu-MOF) coatings were fabricated and immobilized on pure Zn. The results indicated that the degradation rate and water stability of Mg/Cu-MOF coatings could be regulated by controlling the feeding ratio of Cu2+. As the coating and Zn substrate degraded, an alkaline microenvironment enriched with Zn2+, Mg2+, and Cu2+ was generated. It significantly improved calcium phosphate deposition, differentiation of osteoblasts, and vascularization of endothelial cells in the extracts. Among them, Mg/Cu1 showed the best comprehensive performance. The superior antibacterial activity of Mg/Cu1 was demonstrated in vitro and in vivo, which indicated significantly enhanced bacteriostatic activity against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli as compared to that of the bare sample. Bimetallic Mg/Cu-MOF coating could properly coordinate the multifunction on a Zn membrane and could be a promising platform for promoting its bone regeneration, which could pave the way for Zn-based materials to be used as barrier membranes in oral clinical trials.

Recent insights on the use of modified Zn-based catalysts in eCO2RR.

Converting CO2 into valuable chemicals can provide a new path to mitigate the greenhouse effect, achieving the aim of "carbon neutrality" and "carbon peaking". Among numerous electrocatalysts, Zn-based materials are widely distributed and cheap, making them one of the most promising electrocatalyst materials to replace noble metal catalysts. Moreover, the Zn metal itself has a certain selectivity for CO. After appropriate modification, such as oxide derivatization, structural reorganization, reconstruction of the surfaces, heteroatom doping, and so on, the Zn-based electrocatalysts can expose more active sites and adjust the d-band center or electronic structure, and the FE and stability of them can be effectively improved, and they can even convert CO2 to multi-carbon products. This review aims to systematically describe the latest progresses of modified Zn-based electrocatalyst materials (including organic and inorganic materials) in the electrocatalytic carbon dioxide reduction reaction (eCO2RR). The applications of modified Zn-based catalysts in improving product selectivity, increasing current density and reducing the overpotential of the eCO2RR are reviewed. Moreover, this review describes the reasonable selection and good structural design of Zn-based catalysts, presents the characteristics of various modified zinc-based catalysts, and reveals the related catalytic mechanisms for the first time. Finally, the current status and development prospects of modified Zn-based catalysts in eCO2RR are summarized and discussed.

Effect of laser power on microstructure and mechanical properties of pure Zn fabricated via laser powder bed fusion

The preparation of biodegradable pure Zn porous scaffolds using additive manufacturing technology has great potential for application. However, the mechanical properties of pure Zn are not sufficient for the clinical application of stents. An object of this paper was to investigate the effect of laser power on microstructural evolution and tensile properties of pure Zn fabricated via laser powder bed fusion (LPBF). The results demonstrated that the temperature gradient and heat storage were the main factors determining the microstructure. The formation of columnar grains was due to the high temperature gradient in the early printing stage, and the equiaxed grains in the middle and top region were attributed to the heat storage induced recrystallization and columnar-to-equiaxed transition (CET), respectively. In addition, as the laser power increased from 40 W to 60 W, the recrystallization degree increased, and the Kernel average misorientation value and Taylor factor decreased gradually, resulting in a significant increase in the ductility. The mechanical properties were maximized at the laser power of 60 W and the scanning rate of 150 mm/s (yield strength, tensile strength and elongation of samples can reach 82.02 MPa, 116.20 MPa and 37.16 %, respectively). This work provides theoretical support for optimizing the mechanical properties of LPBF Zn-based materials by microstructural regulation.

A Dose-Dependent Spatiotemporal Response of Angiogenesis Elicited by Zn Biodegradation during the Initial Stage of Bone Regeneration.

Zinc (Zn) plays a crucial role in bone metabolism and imbues biodegradable Zn-based materials with the ability to promote bone regeneration in bone trauma. However, the impact of Zn biodegradation on bone repair, particularly its influence on angiogenesis, remains unexplored. This study reveals that Zn biodegradation induces a consistent dose-dependent spatiotemporal response in angiogenesis,both in vivo and in vitro. In a critical bone defect model, an increase in Zn release intensity from day 3 to 10 post-surgery is observed. By day 10, the CD31-positive area around the Zn implant significantly surpasses that of the Ti implant, indicating enhanced angiogenesis. Furthermore,angiogenesis exhibits a distance-dependent pattern closely mirroring the distribution of Zn signals from the implant. In vitro experiments demonstrate that Zn extraction fosters the proliferation and migration of human umbilical vein endothelial cells and upregulates the key genes associated with tube formation, such as HIF-1α and VEGF-A, peaking at a concentration of 22.5 µM. Additionally, Zn concentrations within the range of 11.25-45 µM promote the polarization of M0-type macrophages toward the M2-type, while inhibiting polarization toward the M1-type. These findings provide essential insights into the biological effects of Zn on bone repair, shedding light on its potential applications.

Fabrication and Properties of a Biodegradable Zn-Ca Composite.

In recent years, Zn and its alloys have become some of the most promising degradable metals as in vivo implants due to their acceptable biocompatibility and more suitable degradation rate compared with Mg-based and Fe-based alloys. However, the degradation rate of Zn-based materials after implantation in the body for orthopedic applications is relatively slow, leading to long-term retention of the implants after fulfilling their missions. Moreover, the excessive release of Zn2+ during the degradation process of Zn-based implants usually leads to high cytotoxicity and delayed osseointegration. To provide a feasible solution to the problem faced by Zn-based implants, a Zn-Ca composite was fabricated by an air pressure infiltration method in this work. The XRD pattern of the composite suggests that the composite is fully composed of Zn-Ca intermetallic compounds. The degradation tests in vitro show that the composite has a much higher degradation rate than pure Zn, and the high Ca content regions in the composite can preferentially degrade as sacrificial anodes. In addition, the composite can efficiently induce Ca-P deposition during immersion tests in Hank's solution. Cytotoxicity tests indicate that L-929 cells exhibit around 82% cell viability (Grade 1) even after being cultured in the 100% extract prepared from the Zn-Ca composite for 1 day and show excellent cell viability.

Zinc as a potential bio-degradable temporary implant material

This paper discusses the possibility of developing metallic zinc (Zn) and its alloys as temporary bio-implants by improving its properties through alloying, mechanical deformations and surface modifications. Even though the research on Mg and Fe as potential temporary implant materials started over two decades ago, Zn is a comparatively newer candidate in this arena. The scope for Zn-based materials for bio-related applications is immense due to their metabolically essential status, ideal biodegradation rates and the possibility of proper excretion by the kidneys. This paper covers the unique favourable properties of Zn and its alloys, which can be explored for bio-applications, along with its limitations and possible options to overcome the limitations. The mechanical properties of Zn implants can be improved to the set standards of load-bearing applications by alloying and mechanical deformations like extrusion, rolling and severe plastic deformations. As a result, the microstructure of the metal alters by grain refinement, formation and redistribution of intermetallic phases, resulting in enhanced hardness, Young's modulus and elastic modulus of the material. The Zn implant surface can be made fully bioactive and corrosion-resistant by engineering its surfaces with biocompatible polymers, bioactive materials like hydroxyapatite and bio-inductive elements like Si. The biochemical treatments, sol–gel techniques and plasma electrolytic oxidation (PEO) processes are effective for surface modification of Zn-based materials. Alloying, mechanical treatments and surface modification techniques are reported to be effective in improving the function of Zn-based implant materials, as discussed in this paper.

Biodegradable porous Zn-1Mg-3βTCP scaffold for bone defect repair: In vitro and in vivo evaluation

Zn-based materials are promising as bone repair materials, but their poor mechanical property and bioactivity as well as low degradation rate render the potential application. Rational structural and material design can address the concerns. In this study, porous Zn-1 wt.%Mg-3 vol.%β-TCP scaffolds with 40% and 60% preset porosities were fabricated via heating-press sintering using NaCl particles as space holders, and their mechanical properties, in vitro degradation behavior, cytotoxicity and in vivo osteogenic activities were evaluated. The results showed that the actual porosities of the scaffolds were 22% and 50%. Mg exists in the form of Zn2Mg and Zn11Mg2, while β-TCP evenly distributed in the matrix. The compressive yield strength of scaffolds ranges from approximately 58.46 to 71.04 MPa, which is close to that of cancellous bone. The in vitro degradation tests showed that the corrosion rate of the scaffolds was in the range of about 2.73–4.28 mm y–1. Moreover, the scaffolds not only provided great space for osteoblasts adhesion and proliferation in vitro but also possessed favorable degradability and osteogenic activity in vivo. The porous Zn-1 wt.%Mg-3 vol.%β-TCP scaffolds manifest reliable mechanical properties, desirable degradability, and osteogenic activity, which are promising as next-generation bone repair materials.

Densification, microstructure, tribological and electrochemical properties of pure Zn fabricated by laser powder bed fusion

The fabrication of Zn-based materials by laser powder bed fusion (LPBF) has been proved to be feasible. In this work, high relative density (98.10 %) of LPBF pure Zn samples were successfully obtained by optimizing the process parameters at low power (30–60 W). The microstructural formation mechanism and evolution of LPBF pure Zn under different power were investigated. With the increase of power, the recrystallization during the printing process became more completely, resulting in the increase of equiaxed grains integral number of the sample. The microhardness of the samples increases with the increase of the power, but the tribological properties change unobvious and the coefficient of friction of LPBF pure Zn in SBF solution is about 0.56–0.57. The electrochemical test manifests that, with the increase of power, the electrochemical corrosion rate of LPBF pure Zn increased, and the corresponding corrosion resistance decreased.

Cytotoxicity of Biodegradable Zinc and Its Alloys: A Systematic Review.

Zinc-based biodegradable metals (BMs) have been developed for biomedical implant materials. However, the cytotoxicity of Zn and its alloys has caused controversy. This work aims to investigate whether Zn and its alloys possess cytotoxic effects and the corresponding influence factors. According to the guidelines of the PRISMA statement, an electronic combined hand search was conducted to retrieve articles published in PubMed, Web of Science, and Scopus (2013.1-2023.2) following the PICOS strategy. Eighty-six eligible articles were included. The quality of the included toxicity studies was assessed utilizing the ToxRTool. Among the included articles, extract tests were performed in 83 studies, and direct contact tests were conducted in 18 studies. According to the results of this review, the cytotoxicity of Zn-based BMs is mainly determined by three factors, namely, Zn-based materials, tested cells, and test system. Notably, Zn and its alloys did not exhibit cytotoxic effects under certain test conditions, but significant heterogeneity existed in the implementation of the cytotoxicity evaluation. Furthermore, there is currently a relatively lower quality of current cytotoxicity evaluation in Zn-based BMs owing to the adoption of nonuniform standards. Establishing a standardized in vitro toxicity assessment system for Zn-based BMs is required for future investigations.

Reconstructed anti-poisoning surface for enhanced electrochemical CO2 reduction on Cu-incorporated ZnO

Zn-based materials are regarded as a family of promising electrocatalysts for electrochemical CO2 reduction reaction (e-CO2RR), especially for the CO2-to-CO conversion. However, their electrocatalytic performances should be improved and the conversion mechanism needs to be further studied. In this work, we fabricate Cu-incorporated ZnO (Cu25Zn-A) on Zn plate for e-CO2RR catalyst by a facile annealing method. We find that Cu25Zn-A achieves a high CO Faraday efficiency > 90% with a CO yield rate of 0.49 mmol cm−2 h−1. The improved catalytic activity on Cu25Zn-A is mainly attributed to the Cu steps on the reconstructed surface in the reaction: (1) that weakens the OH-/CO32- adsorption, leading to the anti-poisoning surface by preventing the formation of Zn hydroxide/carbonates; and (2) that enhances the adsorption/activation of reactants and stabilizes the intermediates. Additionally, the density of defects in Zn oxide is increased by the Cu-incorporation, resulting in improved deoxygenation step. Our findings may provide insightful understanding on the mechanism and guide the design of novel electrocatalyst for effective CO2 reduction.

Interfacial strengthening and antibacterial behavior in an ultrafine-grained Zn-Ag-based biocomposites fabricated by the Cu2O-induced in situ wetting approach

Nowadays, Zinc (Zn)-based biocomposites as biodegradable implant materials have been recognized as a promising approach to overcome the insufficient mechanical performance of Zn matrix and to endow the Zn-based materials with biofunctionality. However, the strengthening effect on Zn-based matrix composite remains far from expectation mainly due to the poor interfacial bonding between the reinforcement and Zn matrix, and the relatively coarse grain size of the Zn matrix. Herein, we have developed a novel in situ wetting strategy to ameliorate the interfacial bonding and mechanical performance of Zn-Ag-based composites using cuprous oxide-modified graphene oxide (Cu2O-GO) sheets as reinforcement. The enhanced interfacial bonding between GO sheets and Zn matrix owing to the in situ generated ZnO interlayer and the ultrafine microstructure with an average grain size of 360 nm were simultaneously achieved in the hot extruded (HEed) 1 wt%Cu2O-GO/Zn-2 wt%Ag biocomposites. Consequently, HEed biocomposites possessed excellent tensile properties, including ultimate tensile strength (UTS) of 344.0 ± 2.4 MPa, yield stress (YS) of 314.0 ± 4.8 MPa, and elongation at failure of 15.5% ± 1.3%. Ultrafine and uniform microstructure of the HEed biocomposites resulted in a relatively uniform corrosion morphology and a degradation rate of 0.195 ± 0.004 mm y−1 in simulated body fluid (SBF) solution. The 2-fold diluted extract of the HEed biocomposites exhibited satisfying cytocompatibility with MC3T3-E1 pre-osteoblast comparable to that of Ti-6Al-4 V ELI alloys. More importantly, the synergistic effect of metallic ions, Ag-rich nanoparticles, and GO sheets contributed to the remarkable antibacterial activity of the experimental biocomposites against both S. aureus and E. coli. These results demonstrated that the 1Cu2O-GO/Zn-2Ag biocomposites should be anticipated as a promising biodegradable material for orthopedic applications.

Tunability of mechanical and biodegradation properties of zinc-based biomaterial with calcium Micronutrient alloying

Biodegradable metals are being investigated as temporary implants that dissolve safely in the body after bone regeneration. Zinc (Zn) has an intermediate biodegradation rate between magnesium and stainless steels, yet its degradation rate is too slow to function as a temporary orthopedic implant. Alloying with nutrient elements is considered a strategy to tune its mechanical properties and in vivo biodegradability. Zn/calcium (Zn/Ca) alloys (with 0.5, 1, and 2 wt% Ca) were processed by spark plasma sintering and their microstructure, mechanical, and biodegradation properties were investigated. Ca was distributed in the grain boundary regions of Zn due to its low miscibility in Zn. Furthermore, the corrosion rates of Zn/Ca alloys determined from linear polarization measurements (0.164–0.325 mm/yr) accelerated by at least 10% compared with pure sintered Zn (0.149 mm/yr) with simultaneous dissolution of Zn and Ca, as verified from X-ray diffraction analysis of the corrosion products. The alloy specimens exhibited hardness (52–58 HV) and compressive strength (93–119 MPa) comparable with those of human cortical and cancellous bones (49 HV; 90–209 MPa). This study demonstrated the tunability of the mechanical and biodegradation properties of Zn-based materials by alloying them with a nutrient element for potential application as temporary orthopedic implants.

Degradation behavior, biocompatibility and antibacterial activity of plasma electrolytic oxidation treated zinc substrates

A ZnO/Zn(OH)2 hybrid coating was fabricated in situ via plasma electrolytic oxidation (PEO) in Na2CO3 electrolyte on pure Zn surface for elucidating the influence of PEO treatment on the degradation behavior of Zn and Zn-based materials. Degradation effects, including surface morphology evolution, corrosion product generation and degradation rate, were systematically investigated through simulated body fluid (SBF) immersion and Hank's solution immersion tests. The results confirm that PEO treatment accelerates the degradation of Zn. With the rise in applied voltage, the initial degradation rate decreases from 0.60 to 0.20 mm/year, whereas the long-term degradation rate can reach 0.50–0.70 mm/year. Especially, the degradation rate acquired at 400 V could meet the general design criteria for degradation rate of biodegradable metallic devices. The corrosion products mainly consist of Zn(OH)2, ZnO, Zn3(PO4)2 and CaP matters. They aggregate to form a bi-layer on the as-formed PEO coating surface. Furthermore, the good in vitro biocompatibility and antibacterial properties of the PEO-treated Zn indicate that PEO is a promising method to treat Zn and Zn-based implants for orthopedic application. When the applied voltage is 400 V, the increased hydrophilicity (WCA <25°), good biocompatibility (cell viability >100 %) and the best enhanced antibacterial performance (53.3 % for S. aureus, 88.3 % for E. coli) compared to that of pure Zn are observed.

Investigations on the interconnection between chemical reactions and experimental results of Zn-based quantum dots

ZnS-10H polytype, ZnO quantum dots, and mixed ZnS/ZnO obtained using zinc sulfate, zinc chloride, and zinc acetate as precursors, respectively. Nanoparticles, nanosheets, and nanoflowers were formed by changing zinc precursors and capping agents.