Magnesium alloys attracted great attention as a new kind of degradable biomaterials. One research direction of biomedical magnesium alloys is based on the industrial magnesium alloys system, and another is the self-designed biomedical magnesium alloys from the viewpoint of biomaterials. The mechanical, biocorrosion properties and biocompatibilities of currently reported Mg alloys were summarized in the present paper, with the mechanical properties of bone tissue, the healing period postsurgery, the pathophysiology and toxicology of the alloying elements being discussed. The strategy in the future development of biomedical Mg alloys was proposed.

Recent developments and trends of sol–gel auto-combustion method for spinel ferrite nanomaterial synthesis are briefly discussed and critically analyzed. The analysis of various parameters of reaction which could be used for better understanding of synthesis process and control of microstructure and property of spinel ferrite nanopowder products was the main objective of this review article. Special attention was paid to variety of particle size and phase purity. For these purposes the correlation between complexant, oxygen balance and combustion process chemical additives, as well as heating mechanism and atmosphere, was established. These results are relevant from standpoints of both application and processing of ferrites.

Graphene is a remarkable material with great potential in many applications due to its chemical and physical properties. In this review we briefly present the recent research progress (2016–2018) in graphene and graphene-based nanomaterials synthesis and discuss the practical aspects of using the materials produced via these methods for different graphene-based applications.

Magnesium has been suggested as a revolutionary biodegradable metal for biomedical applications. The corrosion of magnesium, however, is too rapid to match the rates of tissue healing and, additionally, exhibits the localized corrosion mechanism. Thus it is necessary to control the corrosion behaviors of magnesium for their practical use. This paper comprehensively reviews the research progress on the development of representative magnesium based alloys, including Mg--Ca, Mg--Sr, Mg--Zn and Mg--REE alloy systems as well as the bulk metallic glass. The influence of alloying element on their microstructures, mechanical properties and corrosion behaviors is summarized. The mechanical and corrosion properties of wrought magnesium alloys are also discussed in comparison with those of cast alloys. Furthermore, this review also covers research carried out in the field of the degradable coatings on magnesium alloys for biomedical applications. Calcium phosphate and biodegradable polymer coatings are discussed based on different preparation techniques used. We also compare the effect of different coatings on the corrosion behaviors of magnesium alloys substrate.

In the past few decades, many novel non-metal doped ZnO materials have developed hasty interest due to their adaptable properties such as low recombination rate and high activity under the solar light exposure. In this article, we compiled recent research advances in non-metal (S, N, C) doped ZnO, emphasizing on the related mechanism of catalysis and the effect of non-metals on structural, morphological, optical and photocatalytic characteristics of ZnO. This review will enhance the knowledge about the advancement in ZnO and will help in synthesizing new ZnO-based materials with modified structural and photocatalytic properties.

Polypyrrole (PPy), the earliest prepared conducting polymer, has good biocompatibility, easy synthesis and flexibility in processing. Compared with metal and inorganic materials, doped PPy has better mechanical match with live tissue, resulting in its many applications in biomedical field. This mini-review presents some information on specific PPy properties for tissue engineering applications, including its synthesis, doping, bio-modification. Although some challenges and unanswered problems still remain, PPy as novel biomaterial has promoted the development tissue engineering for its clinical application in the future.

This paper gives a statistical view about important contributions and advances on semiconductor metal oxide (SMO) compounds based gas sensors developed to detect the air pollutants such as liquefied petroleum gas (LPG), H₂S, NH₃, CO₂, acetone, ethanol, other volatile compounds and hazardous gases. Moreover, it is revealed that the alloy/composite made up of SMO gas sensors show better gas response than their counterpart single component gas sensors, i.e., they are found to enhance the 4S characteristics namely speed, sensitivity, selectivity and stability. Improvement of such types of sensors used for detection of various air pollutants, which are reported in last two decades, is highlighted herein.

The microstructural evolutions of advanced 9--12%Cr ferrite/martensite heat-resistant steels used for power generation plants are reviewed in this article. Despite of the small differences in chemical compositions, the steels share the same microstructure of the as-tempered martensite. It is the thermal stability of the initial microstructure that matters the creep behavior of these heat-resistant steels. The microstructural evolutions involved? in? 9--12%Cr ?ferrite ?heat-resistant ?steels ?are ?elabo- rated, including (1) martensitic lath widening, (2) disappearance of prior austenite grain boundary, (3) emergence of subgrains, (4) coarsening of precipitates, and (5) formation of new precipitates, such as Laves-phase and Z-phase. The former three microstructural evolutions could be retarded by properly disposing the latter two. Namely improving the stability of precipitates and optimizing their size distribution can effectively exert the beneficial influence of precipitates on microstructures. In this sense, the microstructural stability of the tempered martensite is in fact the stability of precipitates during the creep. Many attempts have been carried out to improve the microstructural stability of 9--12%Cr steels and several promising heat-resistant steels have been developed.

It was assumed for a long time that organisms produce minerals directly from a saturated solution. A few exceptions were known, including the well documented mineralized teeth of the chiton. In 1997 it was demonstrated that sea urchin larva form their calcitic spicules by first depositing a highly unstable mineral phase called amorphous calcium carbonate. This strategy has since been shown to be used by animals from other phyla and for both aragonite and calcite. Recent evidence shows that vertebrate bone mineral may also be formed via a precursor phase of amorphous calcium carbonate. This strategy thus appears to be widespread. The challenge now is to understand the mechanisms by which these unstable phases are initially formed, how they are temporarily stabilized and how they are destabilized and transform into a crystalline mature product.

A Zn–Al layered double hydroxide (ZnAl-LDH) coating consisted of uniform hexagonal nano-plates was firstly synthesized by co-precipitation and hydrothermal treatment on the AZ31 alloy, and then a poly(lactic acid) (PLA) coating was sealed on the top layer of the ZnAl-LDH coating using vacuum freeze-drying. The characteristics of the ZnAl-LDH/PLA composite coatings were investigated by means of XRD, SEM, FTIR and EDS. The corrosion resistance of the coatings was assessed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results showed that the ZnAl-LDH coating contained a compact inner layer and a porous outer layer, and the PLA coating with a strong adhesion to the porous outer layer can prolong the service life of the ZnAl-LDH coating. The excellent corrosion resistance of this composite coating can be attributable to its barrier function, ion-exchange and self-healing ability.

The ductility of as-fabricated Ti–6Al–4V falls far short of the requirements for biomedical titanium alloy implants and the heat treatment remains the only applicable option for improvement of their mechanical properties. In the present study, the decomposition of as-fabricated martensite was investigated to provide a general understanding on the kinetics of its phase transformation. The decomposition of as-fabricated martensite was found to be slower than that of water-quenched martensite. It indicates that specific heat treatment strategy is needed to be explored for as-fabricated Ti–6Al–4V. Three strategies of heat treatment were proposed based on different phase transformation mechanisms and classified as subtransus treatment, supersolvus treatment and mixed treatment. These specific heat treatments were conducted on selective laser melted samples to investigate the evolutions of microstructure and mechanical properties. The subtransus treatment leaded to a basket-weave structure without changing the morphology of columnar prior β grains. The supersolvus treatment resulted in a lamellar structure and equiaxed β grains. The mixed treatment yielded a microstructure that combines both features of the subtransus treatment and supersolvus treatment. The subtransus treatment is found to be the best choice among these three strategies for as-fabricated Ti–6Al–4V to be used as biomedical implants.

Catalytic nanomotors are nano-to-micrometer-sized actuators that carry an on-board catalyst and convert local chemical fuel in solution into mechanical work. The location of this catalyst as well as the geometry of the structure dictate the swimming behaviors exhibited. The nanomotors can occur naturally in organic molecules, combine natural and artificial parts to form hybrid nanomotors or be purely artificial. Fabrication techniques consist of template directed electroplating, lithography, physical vapor deposition, and other advanced growth methods. Various physical and chemical propulsion mechanisms have been proposed to explain the motion behaviors including diffusiophoresis, bubble propulsion, interfacial tension gradients, and self-electropho-resis. The control and manipulation based upon external fields, catalytic alloys, and motion control through thermal modulation are discussed as well. Catalytic nanomotors represent an exciting technological challenge with the end goal being practical functional nanomachines that can perform a variety of tasks at the nanoscale.

Oil spills in the sea have caused many serious environmental problems worldwide. In this study, carbon nanotube (CNT) sponges were used to cleanup oil slicks on sea waters. This method was compared with two traditional representative sorbents, including polypropylene fiber fabric and woolen felt. The CNT sponges had a larger oil sorption capacity than the other two sorbents. The maximum oil sorption capacity (Q_m) of the CNT sponge was 92.30 g/g, which was 12 to 13.5 times larger than the Q_m of the other two sorbents (the Q_m of the polypropylene fiber fabric and woolen felt were 7.45 and 6.74 g/g, respectively). In addition, unlike the other two sorbents, the CNT sponge was super-hydrophobic and did not adsorb any water during oil spill cleanup. CNT sponges are potentially very useful for cleaning up oil spills from sea water.

Increasing evidence shows that magnetic fields and magnetic responsive scaffolds can play unique roles in promoting bone repair and regeneration. This article addresses the synergistic effects of magnetic scaffolds in response to external magnetic fields on the bone regeneration in situ. Additionally, the exploration of using magnetic scaffolds as tools in the bone implant fixation, local drug delivery and mimicking microenvironment of stem cell differentiation are introduced. We also discussed possible underlying mechanisms and perspectives of magnetic responsive scaffolds in the bone repair and regeneration.

Resistive switching (RS) behaviors have attracted great interest due to their promising potential for the data storage. Among various materials, oxide-based devices appear to be more advantageous considering their handy fabrication and compatibility with CMOS technology, though the underlying mechanism is still controversial due to the diversity of RS behaviors. In this review, we focus on the oxide-based RS memories, in which the working mechanism can be understood basically according to a so-called filament model. The filaments formation/rupture processes, approaches developed to detect and characterize filaments, several effective attempts to improve the performances of RS and the quantum conductance behaviors in oxide-based resistive random access memory (RRAM) devices are addressed, respectively.

This review investigates the current application limitations of Mg and Mg alloys. The key issues hindering the application of biodegradable Mg alloys as implants are their fast degradation rate and biological consideration. We have discussed the effect of some selected alloying element additions on the properties of the Mg-based alloy, especially the nutrient elements in human (Zn, Mn, Ca, Sr). Different grain sizes, phase constituents and distributions consequently influence the mechanical properties of the Mg alloys. Solution strengthening and precipitation strengthening are enhanced by the addition of alloying elements, generally improving the mechanical properties. Besides, the hot working process can also improve the mechanical properties. Combination of different processing steps is suggested to be adopted in the fabrication of Mg-based alloys. Corrosion properties of these Mg-based alloys have been measured in vitro and in vivo. The degradation mechanism is also discussed in terms of corrosion types, rates, by-products and response of the surrounding tissues. Moreover, the clinical response and requirements of degradable implants are presented, especially for the nutrient elements (Ca, Mn, Zn, Sr). This review provides information related to different Mg alloying elements and presents the promising candidates for an ideal implant.

Silk fibroin (SF) from the Bombyx mori silkworm exhibits attractive potential applications as biomechanical materials, due to its unique mechanical and biological properties. This review outlines the structure and properties of SF, including of its biocompatibility and biodegradability. It highlights recent researches on the fabrication of various SF-based composites scaffolds that are promising for tissue engineering applications, and discusses synthetic methods of various SF-based composites scaffolds and valuable approaches for controlling cell behaviors to promote the tissue repair. The function of extracellular matrices and their interaction with cells are also reviewed here.

Chitin is a thermostable biopolymer found in various inorganic--organic skeletal structures of numerous invertebrates including sponges (Porifera). The occurrence of chitin within calcium- and silica-based biominerals in organisms living in extreme natural conditions has inspired development of new (extreme biomimetic) synthesis route of chitin-based hybrid materials in vitro. Here, we show for the first time that 3D-α-chitin scaffolds isolated from skeletons of the marine sponge Aplysina aerophoba can be effectively mineralized under hydrothermal conditions (150°C) using ammonium zirconium(IV) carbonate as a precursor of zirconia. Obtained chitin--ZrO₂ hybrid materials were characterized by FT-IR, SEM, HRTEM, as well as light and confocal laser microscopy. We suggest that formation of chitin--ZrO₂ hybrids occurs due to hydrogen bonds between chitin and ZrO₂.

Magnesium alloy has similar mechanical properties with natural bone, but its high susceptibility to corrosion has limited its application in orthopedics. In this study, a calcium phosphate coating is formed on magnesium alloy (AZ31) to control its degradation rate and enhance its bioactivity and bone inductivity. Samples of AZ31 plate were placed in the supersaturated calcification solution prepared with Ca(NO₃)₂, NaH₂PO₄ and NaHCO₃, then the calcium phosphate coating formed. Through adjusting the immersion time, the thickness of uniform coatings can be changed from 10 to 20 ?m. The composition, phase structure and morphology of the coatings were investigated. Bonding strength of the coatings and substrate was 2–4 MPa in this study. The coatings significantly decrease degradation rate of the original Mg alloy, indicating that the Mg alloy with calcium phosphate coating is a promising degradable bone material.

Tumor micro-environment responsive drug delivery systems (DDSs) have been developed as a potential approach to reduce the side effects of cancer chemotherapy. Glutathione (GSH) has been supposed to the most significant signal of the difference between the normal tissue and the tumor cells, besides the media pH and temperature. In recent years, the reduction-responsive DDSs have attracted more and more attention for delivery of anti-cancer drugs, based on such physiological signal. Among them, disulfide bond-containing polymers have been designed as the main tool for the purpose. The recent progress in the synthesis strategies for the disulfide bond-containing polymer-based DDS is focused in the present review.

In this study, we investigated the interface contacting inhibition behaviors of chitosan against bacterial in the dispersing state. For that purpose, chitosan microspheres (CMs) in the dispersing state was prepared by the emulsification cross-linking method. The CMs had smooth surface and spherical shape with the diameter of about 124 ?m. They were stable after sterilization at 121°C and 150 kPa for 20 min. The CMs had similar antibacterial activity to that of chitosan in the solution form. Their antibacterial activities increased with the increase of the CM concentration, while decreased with the increase of pH of the system. It was found that the CMs with the degree of deacetylation (DD) of 63.6% exhibited the highest antibacterial activity, while the CMs with the DD of 83.7% exerted the lowest antibacterial activity among the three tested samples.

Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the implants, resulting from the degradation, arouses a major concern. Micro-arc oxidation (MAO) and poly(lactic acid) (PLA) composite (MAO/PLA) coating on biomedical Mg--1.21Li--1.12Ca--1.0Y alloy was prepared to manipulate the pH variation in an appropriate range. Surface morphologies were discerned using SEM and EMPA. And corrosion resistance was evaluated via electrochemical polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predominantly consisted of MgO, Mg₂SiO₄ and Y₂O₃. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5--7.8. The neutralization caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The result designates that MAO/PLA composite coating on Mg--1.21Li--1.12Ca--1.0Y alloys may be a promising biomedical coating.

Graphene has attracted much attention as a new nano-carbon for its unique structure and properties. However, production and dispersion of unfunctionalized graphene are still big challenges. Herein, we demonstrate a simple method for preparation and dispersion of such graphene with low cost and non toxicum. This approach is achieved by exfoliating graphite in an ethanol/water mixture and forming stable dispersion of mono- and few-layer graphenes. The ratio of ethanol/water in the mixture is found to be crucial to both the exfoliation and dispersion processes. Exfoliation in pure water or pure ethanol produces no graphene. This method avoids the conventional use of harsh oxidants and surfactants; therefore, the graphitic structure is well maintained without destruction. Benefiting from the use of ethanol and water, it can be easy to prepare transparent and conductive graphene films by vacuum filtering or spray method, and does not need special post-treatment to remove the impurity, which could be beneficial for potential applications in electronic, optic and energy areas.

This manuscript focuses on bone repair/regeneration using tissue engineering strategies, and highlights nanobiotechnology developments leading to novel nanocomposite systems. About 6.5 million fractures occur annually in USA, and about 550,000 of these individual cases required the application of a bone graft. Autogenous and allogenous bone have been most widely used for bone graft based therapies; however, there are significant problems such as donor shortage and risk of infection. Alternatives using synthetic and natural biomaterials have been developed, and some are commercially available for clinical applications requiring bone grafts. However, it remains a great challenge to design an ideal synthetic graft that very closely mimics the bone tissue structurally, and can modulate the desired function in osteoblast and progenitor cell populations. Nanobiomaterials, specifically nanocomposites composed of hydroxyapatite (HA) and/or collagen are extremely promising graft substitutes. The biocomposites can be fabricated to mimic the material composition of native bone tissue, and additionally, when using nano-HA (reduced grain size), one mimics the structural arrangement of native bone. A good understanding of bone biology and structure is critical to development of bone mimicking graft substitutes. HA and collagen exhibit excellent osteoconductive properties which can further modulate the regenerative/healing process following fracture injury. Combining with other polymeric biomaterials will reinforce the mechanical properties thus making the novel nano-HA based composites comparable to human bone. We report on recent studies using nanocomposites that have been fabricated as particles and nanofibers for regeneration of segmental bone defects. The research in nanocomposites, highlight a pivotal role in the future development of an ideal orthopaedic implant device, however further significant advancements are necessary to achieve clinical use.

Solar cells represent a principal energy technology to convert light into electricity. Commercial solar cells are at present predominately produced by single- or multi-crystalline silicon wafers. The main drawback to silicon-based solar cells, however, is high material and manufacturing costs. Dye-sensitized solar cells (DSSCs) have attracted much attention during recent years because of the low production cost and other advantages. The photoanode (working electrode) plays a key role in determining the performance of DSSCs. In particular, nanostructured photoanodes with a large surface area, high electron transfer efficiency, and low electron recombination facilitate to prepare DSSCs with high energy conversion efficiency. In this review article, we summarize recent progress in the development of novel photoanodes for DSSCs. Effect of semiconductor material (e.g. TiO₂, ZnO, SnO₂, N₂O₅, and nano carbon), preparation, morphology and structure (e.g. nanoparticles, nanorods, nanofibers, nanotubes, fiber/particle composites, and hierarchical structure) on photovoltaic performance of DSSCs is described. The possibility of replacing silicon-based solar cells with DSSCs is discussed.

Novel barium tungstate/nitrogen-doped reduced graphene oxide?graphitic carbon nitride (BaWO₄/NRGO?g-C₃N₄) nanocomposite has been synthesized by a simple one-pot microwave technique. The synthesized nanocomposites are well characterized by diffraction, microscopic and spectroscopic techniques to study its crystal structure, elemental composition, morphological features and optical properties. The material prepared is tested for its performance as an electrocatalyst, photocatalyst and reduction catalyst. The nanocomposite catalyzed the photodegradation of methylene blue (MB) dye in 120 min, reduction of 4-nitro phenol (4-NP) to 4-amino phenol (4-AP) in 60 s, showed an impressive Tafel slope of 62 mV/dec for hydrogen evolution reaction (HER). The observed results suggest that the nanocomposite acts as an efficient multifunctional catalyst. The reported approach provides fundamental insights which can be extended to other metal tungstate-based ternary composites for applications in the field of clean energy and environment in the future.

The objective of the present study is to systematically evaluate the role of polymer crystallinity on fibroblast and osteoblast adhesion and proliferation using a series of poly(caprolactone-co-glycolide) (PCL/PGA) polymers. PCL/PGA polymers were selected since they reflect both highly crystalline and amorphous materials. PCL/PGA polymeric materials were fabricated by compression molding into thin films. Five compositions, from PCL or PGA to intermediate copolymeric compositions of PCL/PGA in ratios of 25:75, 35:65 and 45:55, were studied. Pure PCL and PGA represented the crystalline materials while the copolymers were amorphous. The polymers/copolymers were characterized using DSC to assess crystallinity, contact angle measurement for hydrophobicity, and AFM for nanotopography. The PCL/PGA films demonstrated similar hydrophobicity and nanotopography whereas they differed significantly in crystallinity. Cell adhesion to and proliferation on PCL/PGA films and proliferation studies were performed using osteoblasts and NIH-3T3 fibroblasts. It was observed that highly crystalline and rigid PCL and PGA surfaces were significantly more efficient in supporting fibroblast growth, whereas amorphous/flexible PCL/PGA 35:65 was significantly more efficient in supporting growth of osteoblasts. This study demonstrated that while chemical composition, hydrophobicity and surface roughness of PCL/PGA polymers were held constant, crystallinity and rigidity of PCL/PGA played major roles in determining cell responses.

The curcumin loaded chitosan/poly (lactic acid) (PLA) nanofibers were produced using electrospinning. Box-Behnken experimental design was used for the optimization of variables (–1, 0, +1 coded level) like chitosan/PLA strength (% w/v), curcumin strength (% w/v) and applied voltage (kV) to obtain uniform fiber diameter. The morphology of nanofibers was shown by SEM. Molecular interactions and the presence of each chemical compound of curcumin loaded chitosan/PLA fibers were characterized by FTIR and EDX analysis. Antioxidant, drug release and in vitro cytotoxicity tests were performed to evaluate the suitability of nanofibers that would be used for wound healing. In vivo wound healing studies on excision and incision wounds created on rat model showed significant reduction of wound area when compared to untreated. The better healing efficiency can be attributed to the presence of curcumin and chitosan.

A stent is a medical device designed to serve as a temporary or permanent internal scaffold to maintain or increase the lumen of a body conduit. The researchers and engineers diverted to investigate biodegradable materials due to the limitation of metallic materials in stent application such as stent restenosis which requires prolonged anti platelet therapy, often result in smaller lumen after implantation and obstruct re-stenting treatments. Biomedical implants with temporary function for the vascular intervention are extensively studied in recent years. The rationale for biodegradable stent is to provide the support for the vessel in predicted period of time and then degrading into biocompatible constituent. The degradation of stent makes the re-stenting possible after several months and also ameliorates the vessel wall quality. The present article focuses on the biodegradable materials for the cardiovascular stent. The objective of this review is to describe the possible biodegradable materials for stent and their properties such as design criteria, degradation behavior, drawbacks and advantages with their recent clinical and preclinical trials.

We report a green and facile approach for the synthesis of NiFe₂O₄ (NF) nanoparticles with good crystallinity. The prepared materials are studied by various techniques in order to know their phase structure, crystallinity, morphology and elemental state. The BET analysis revealed a high surface area of 80.0 m²·g⁻¹ for NF possessing a high pore volume of 0.54 cm³·g⁻¹, also contributing to the amelioration of the electrochemical performance. The NF sample is studied for its application in supercapacitors in an aqueous 2 mol·L⁻¹ KOH electrolyte. Electrochemical properties are studied both in the three-electrode method and in a symmetrical supercapacitor cell. Results show a high specific capacitance of 478.0 F·g⁻¹ from the CV curve at an applied scan rate of 5 mV·s⁻¹ and 368.0 F·g⁻¹ from the GCD analysis at a current density of 1 A·g⁻¹ for the NF electrode. Further, the material exhibited an 88% retention of its specific capacitance after continuous 10000 cycles at a higher applied current density of 8 A·g⁻¹. These encouraging properties of NF nanoparticles suggest the practical applicability in high-performance supercapacitors.