Electrostatic Self-Assembly Synthesis of Three-Dimensional Mesoporous Lepidocrocite-Type Layered Sodium Titanate as a Superior Adsorbent for Selective Removal of Cationic Dyes via an Ion-Exchange Mechanism.

Three-dimensional mesoporous lepidocrocite-type layered sodium titanate (LST) was constructed at room temperature by the electrostatic interaction between Ti1-δO24δ- nanosheets and Na+ ions. The results of a systematic X-ray diffraction investigation manifested the transition from the Ti1-δO24δ- nanosheets phase to the titanate/titania phase, which determined a phase diagram as a function of the temperature and NaCl concentration. In addition, scanning electron microscopy, inductively coupled plasma-mass spectrometry, thermogravimetric and differential thermal, N2 adsorption-desorption, Raman spectroscopy, Fourier transform infrared spectroscopy, as well as ζ-potential analyses were utilized for adequate characterization of the LST physical and chemical properties. Furthermore, batch adsorption experiments demonstrated that LST had superior adsorption property and adsorption selectivity toward cationic dyes compared to those of anionic dyes. A multifarious influencing effect on the cationic dye adsorption behavior during the adsorption process was systematically investigated. Moreover, the pseudo-second-order kinetic model felicitously depicted the cationic dye adsorption behavior through an elaborate kinetic study, namely, chemisorption was the main adsorption action. Meanwhile, different adsorption isotherm models were utilized to process the experimental data, uncovering that the adsorption isotherms of cationic dyes on LST were suitable for a Langmuir isothermal model. More importantly, an ion-exchange mechanism was proposed for the cationic dye adsorption on LST, and the ion-exchange reaction occurred with a stoichiometric exchange between 1 mol of Na+ ions in the LST interlayer and 1 mol of MB molecules in the solution. In parallel, the electrochemical impedance spectroscopy and cyclic voltammogram measurements verified that the high ionic conductivity of Na+ ions in the LST interlayer resulted in a superior adsorption property. A two-step acid-base procedure was ultimately adopted to effectively regenerate LST adsorbent. This work provides not only an alternative adsorbent with superior adsorption capacity and adsorption selectivity but also some guiding significance for research on the adsorption mechanism of layered titanates.

Tailored Hydrothermal Synthesis of Specific Facet-Dominated TiO2 Nanocrystals from Lepidocrocite-Type Layered Titanate Nanosheets: Systematical Investigation and Enhanced Photocatalytic Performance.

A series of samples including leaf-like and rod-like rutile TiO2 nanoparticles with various facets exposed on the surface, parallelepiped-shaped anatase nanoparticles with [111] vertical facet exposed on the surface, irregular anatase nanoparticles, microsized six-point star-like anatase aggregates, and almond-like brookite aggregates had been hydrothermally synthesized from lepidocrocite-type layered titanate nanosheets. A systematical investigation was established to uncover the phase transition and morphological evolution from nanosheets to TiO2 polymorphs, and a phase diagram was determined by adjusting the synthesis parameters of the pH value and temperature. Two kinds of mechanisms composed of the dissolution-deposition process following Ostwald's ripening mechanism and the in situ topochemical conversion process following Ostwald's step rule had been proposed based on the time-dependent hydrothermal experiments. Briefly, the formation of the single-crystalline rutile phase appeared only at high temperatures with very low pH values, and similarly, the brookite phase strictly formed at high temperatures with a very high pH value. Nevertheless, the anatase phase could moderately appear in a wide range of temperatures and pH values. In addition, the single-crystalline rutile adopted a leaf-like morphology at low temperatures with high pH values and a rod-like morphology at high temperatures with low pH values, while the morphological evolution of anatase particles proceeded from irregular to parallelepiped-shaped and finally to six-point star-like morphology, and the crystal size was reduced from 1000 to 5 nm with decreasing pH values. Meanwhile, with the prolongation of the hydrothermal time, the layered titanate nanosheets first dissolved into the amorphous state and further converted into small anatase nanoparticles and finally to rutile or anatase nanoparticles based on the dissolution-deposition process, or the {010}-faceted layered titanate structure first converted into the [111]-vertical faceted anatase nanosheets by the topochemical transformation reaction and then split into the [111]-vertical faceted anatase nanoparticles. More importantly, the mesoporous [111]-vertical faceted anatase nanoparticles exhibited enhanced photocatalytic performance compared to that of Degussa P25, which was ascribed to its superior electronic band structure and effective charge separation. The systematical investigation in this work would be significant for consummating the preparation of the TiO2 polymorphs from layered titanate nanosheets and provided some reference values and guide schemes for the preparation of TiO2 nanoparticles with outstanding photocatalytic performance.

[Recent development of research on the biotribology of carbon fiber reinforced poly ether ether ketone composites].

Carbon fiber reinforced poly ether ether ketone (CF/PEEK) composite possesses excellent biocompatible, biomechanical and bioribological properties. It is one of the most promising implant materials for artificial joint. Many factors influence the bioribological properties of CF/PEEK composites. In this paper, the authors reviewed on the biotribology research progress of CF/PEEK composites. The influences of various factors such as lubricant, reinforcement surface modification, functional particles, friction counterpart and friction motion modes on the bio-tribological properties of CF/PEEK composites are discussed. Based on the recent research, the authors suggest that the further research should be focused on the synergistic effect of multiple factors on the wear and lubrication mechanism of CF/PEEK.

Effect of graphene oxide on sodium alginate hydrogel as a carrier triggering release of ibuprofen.

The design and preparation of safe wound dressings with antibacterial and controlled drug release abilities is valuable in medicine. This research focuses on the fabrication of a hydrogel carrier with graphene oxide (GO)-triggered ibuprofen (IBU) release to control inflammation. The hydrogel was prepared by cross-linking the base polymer sodium alginate (SA) and functionalized GO. The morphology of the gel was observed by a scanning electron microscope (SEM), and its structure was analyzed through X-ray diffraction (XRD) and Fourier transform infrared reflection (FTIR) spectroscopy. The effects of GO on swelling capacity, IBU release behavior and antibacterial activity were investigated by using the prepared GO/SA hydrogel as a drug carrier and IBU as a drug model. In vitro studies confirmed that the GO/SA hydrogel had good antimicrobial activity and excellent cytotoxicity. The analysis of cumulative IBU release rates revealed that the addition of GO could promote the release of IBU, and the change in GO content did not have a prominent effect on IBU release. At the same time, the rate of IBU release from the GO/SA hydrogel was affected by near-infrared light. Under a light source, the release rate of IBU increased, and the release amount of IBU showed a clear stepwise increase under light on-off conditions. These results suggest that the GO/SA hydrogel could be a potential antibacterial and anti-inflammatory wound dressing.

A self-assembling graphene oxide coating for enhanced bactericidal and osteogenic properties of poly-ether-ether-ketone.

Poly-ether-ether-ketone (PEEK) is a biomedical plastic that can be used for orthopedic implants, but it offers poor antibacterial properties and bioactivity. In this study, PEEK was sulfonated with the obtained porous structure adsorbing graphene oxide (GO). The surface microstructures and properties of the original PEEK, sulfonated PEEK (SPEEK), and GO-grafted PEEK (GO-SPEEK) were characterized. The results revealed that the GO-SPEEK surface is a 3D porous structure exhibiting superior hydrophilicity to the original PEEK. Although SPEEK was shown to possess antimicrobial properties against both Escherichia coli and Staphylococcus aureus, the bactericidal effect was even more significant for GO-SPEEK, at about 86% and 94%, respectively. In addition, the in vitro simulated-body-fluid immersion and cell experiments indicated that GO-SPEEK had much better hydroxyapatite (HA)-precipitation induction capacity and cell-material interactions (e.g., cell adhesion, proliferation, osteodifferentiation, and extracellular matrix mineralization. The tensile test revealed that the mechanical properties of PEEK were maintained after surface modification, as GO-SPEEK has comparable values of elastic modulus and tensile strength to PEEK. Our investigation sought a method to simultaneously endow PEEK with both good antimicrobial properties and bioactivity as well as mechanical properties, providing a theoretical basis for developing high-performance orthopedic implants in the clinic.

[Research on tissue engineered cartilage for repairing of articular cartilage damage and defects].

Articular cartilage damage is very common in clinical practices. Due to the low self healing abilities of articular cartilage, it must be repaired or substituted by implants once natural articular cartilage is damaged. On the other hand, the various technologies currently used for healing damaged articular cartilage are little satisfactory, and rarely restore full function or return the tissue to its natively normal state. Tissue engineering technology holds great promise for the healing of damage or defects of articular cartilage. Tissue engineered articular cartilage is one of the most promising methods for repairing articular cartilage trauma and defects. In this paper, the authors review the research progress of three elements such as seed cells, growth factors and scaffolds which constitute tissue engineered articular cartilage.

Hierarchical spheroidal MOF-derived MnO@C as cathode components for high-performance aqueous zinc ion batteries.

Aqueous zinc-ion batteries (AZIBs) have shown great potential as energy storage devices owing to their high energy density, low cost, and low toxicity. Typically, high performance AZIBs incorporate manganese-based cathode materials. Despite their advantages, these cathodes are limited by significant capacity fading and poor rate performance due to the dissolution and disproportionation of manganese. Herein, hierarchical spheroidal MnO@C structures were synthesized from Mn-based metal-organic frameworks, which benefit from a protective carbon layer to prevent manganese dissolution. The spheroidal MnO@C structures were incorporated onto a heterogeneous interface to act as a cathode material for AZIBs, which exhibited excellent cycling stability (160 mAh g-1 after 1000 cycles at 3.0 A g-1), good rate capability (165.9 mAh g-1 at 3.0 A g-1), and appreciable specific capacity (412.4 mAh g-1 at 0.1 A g-1) for AZIBs. Moreover, the Zn2+ storage mechanism in MnO@C was comprehensively investigated using ex-situ XRD and XPS studies. These results demonstrate that hierarchical spheroidal MnO@C is a potential cathode material for high-performing AZIBs.

Proton Self-Doped Polyaniline with High Electrochemical Activity for Aqueous Zinc-Ion Batteries.

Aqueous zinc-ion batteries are promising energy storage devices due to their low cost, good ionic conductivity, and high safety. Conductive polyaniline is a promising cathode because of its redox activity, but because the neutral electrolyte protonates only weakly, it displays limited electrochemical activity. A polyaniline cathode is developed with proton self-doping from manganese metal-organic frameworks (Mn-MOFs) that alleviates the deprotonation and electrochemical activity concerns arising during the charge/discharge process. The MOFs carboxyl group provides protons to prevent deprotonation and allows the polyaniline to reach a high zinc storage redox activity. The proton self-doped polyaniline cathode has a superior specific capacity (273 mAh g-1 at 0.5 A g-1 ), a high rate property (154 mAh g-1 at 20 A g-1 ), and excellent cyclability retention (87% over 4000 cycles at 15 A g-1 ). This research provides fresh insight into the development of innovative polymers as cathode materials for high-performance AZIBs.

Proton-self-doped PANI@CC as the cathode for high-performance aqueous zinc-ion battery.

Aqueous zinc-ion batteries (AZIB) have several advantages such as low cost, large theoretical capacity and good safety. However, the development of polyaniline (PANI) cathode materials has been limited by slow diffusion kinetics. Herein, proton-self-doped polyaniline@carbon cloth (CC) (PANI@CC) was prepared via in-situ polymerization, where polyaniline was deposited on an activated carbon cloth. The PANI@CC cathode exhibits a high specific capacity of 234.3 mA h g-1 at 0.5 A g-1, and excellent rate performance, delivering a capacity of 143 mA h g-1 at 10 A g-1. Furthermore, the reversible redox conversion during the charge-discharge process was studied using ex-situ X-ray photoelectron spectroscopy (XPS) and ex-situ Raman spectra. The results show that the excellent performance of the PANI@CC battery can be attributed to the formation of a conductive network between the carbon cloth and polyaniline. Also, a mixing mechanism involving insertion/extraction of Zn2+/H+ and a double-ion process is proposed. PANI@CC electrode is a novel idea for developing high-performance batteries.

[Research on surface modification and bio-tribological properties of artificial joint].

The bio-tribological properties of an artificial joint can be obviously improved by surface modification technologies. In this paper, the benefits and disadvantages of various surface modification methods-such as surface coating, plasma treatment, surface texture and surface grafting modification-are discussed. The aim of surface coating and/or plasma treatment is to improve the surface hardness of the materials, thus enhancing the wear resistance of artificial joints. However, these technologies do not effectively alleviate stress concentration of material in the short times in which artificial joints bear physiological impact load, resulting in easy fracture. Surface texture serves mainly to improve the lubrication properties through micro-concavities on the material surface for storage lubricant. Surface texturing can realize improvements in bio-tribological properties, but it does not enhance the impact resistance of the joint. Surface grafting modification is implemented mainly by grafting hydrophilic or other specific functional groups to improve the surface hydrophilicity and wetability, thus enhancing lubricating performance and reducing the coefficient of friction.

Using a two-step method of surface mechanical attrition treatment and calcium ion implantation to promote the osteogenic activity of mesenchymal stem cells as well as biomineralization on a ß-titanium surface.

Surface treatment is known as a very efficient measure by which to modulate the surface properties of biomaterials in terms of grain structure, topography, roughness and chemistry to determine the osseointegration of implants. In this work, a two-step method of surface modification was employed to impart high osteogenic activity and biomineralization capacity on a Ti-25Nb-3Mo-2Sn-3Zr alloy (a type of ß-titanium named TLM). The preliminary surface mechanical attrition treatment (SMAT) refined the average grain size from 170 ± 19 µm to 74 ± 8 nm in the TLM surface layer and promoted the surface to be much rougher and more hydrophilic. The subsequent Ca-ion implantation did not change the surface roughness and topography obviously, but enhanced the surface wettability of the SMAT-treated TLM alloy. The in vitro evaluations of the adhesion, proliferation, osteogenic genes (RUNX2, ALP, BMP-2, OPN, OCN and COL-I) and protein (ALP, OPN, OCN and COL-I) expressions, as well as extracellular matrix (ECM) mineralization of mesenchymal stem cells (MSCs) revealed that the initial SMAT-treated sample significantly enhanced the adhesion and osteogenic functions of MSCs compared to an untreated TLM sample, and the subsequent introduction of Ca ions onto the SMAT-derived nanograined sample further promotes the MSC adhesion, proliferation, osteo-differentiation and ECM mineralization due to the adsorption of more proteins such as laminin (Ln), fibronectin (Fn) and vitronectin (Vn) on the surface, as well as the increase in extracellular Ca concentrations. In addition, the biomineralization capacity of the samples was also evaluated by soaking them in simulated bodily fluid (SBF) at 37 °C for 28 days, and the results showed that the Ca-ion implanted sample significantly boosted the deposition of Ca and P containing minerals on its surface, which was associated with the generation of more Ti-OH groups on the surface after ion implantation. The combination of the SMAT technique and Ca-ion implantation thus endowed the TLM alloy with outstanding osteogenic and biomineralization properties, providing a potential means for its future use in the orthopedic field.

Coordinately Unsaturated Manganese-Based Metal-Organic Frameworks as a High-Performance Cathode for Aqueous Zinc-Ion Batteries.

The slow Zn2+ intercalation/deintercalation kinetics in cathodes severely limits the electrochemical performance of aqueous zinc-ion batteries (ZIBs). Herein, we demonstrate a new kind of coordinately unsaturated manganese-based metal-organic framework (MOF) as an advanced cathode for ZIBs. Coordination unsaturation of Mn is performed with oxygen atoms of two adjacent -COO-. Its proper unsaturated coordination degree guarantees the high-efficiency Zn2+ transport and electron exchange, thereby ensuring high intrinsic activity and fast electrochemical reaction kinetics during repeated charging/discharging processes. Consequently, this MOF-based electrode possesses a high capacity of 138 mAh g-1 at 100 mA g-1 and a long life span (93.5% capacity retention after 1000 cycles at 3000 mA g-1) due to the above advantages. Such distinct Zn2+ ion storage performance surpasses those of most of the recently reported MOF cathodes. This concept of adjusting the coordination degree to tune the energy storage capability provides new avenues for exploring high-performance MOF cathodes in aqueous ZIBs.

Regulating the Interlayer Spacing of Vanadium Oxide by In Situ Polyaniline Intercalation Enables an Improved Aqueous Zinc-Ion Storage Performance.

Vanadium pentoxide (V2O5) possesses great potential for application as cathode materials for aqueous zinc-ion batteries due to abundant valences of vanadium. Unfortunately, the inferior electronic conductivity and confined interlayer spacing of pristine V2O5 are not able to support fast Zn2+ diffusion kinetics, leading to significant capacity degradation, the dissolution of active species, and unsatisfactory cycling life. Herein, Zn2+ (de)intercalation kinetics is improved by the design of in situ polyaniline (PANI)-intercalated V2O5. The intercalated PANI can not only improve the conductivity and structural stability of V2O5 but also efficiently expand its interlayer spacing (1.41 nm), offering more channels for facile Zn2+ diffusion. Benefiting from these virtues, a high specific capacity of 356 mA h g-1 at 0.1 A g-1 is achieved for the PANI-intercalated V2O5 (PVO) cathode as well as a superior cycling performance (96.3% capacity retention after 1000 cycles at 5 A g-1) in an aqueous electrolyte. Furthermore, the Zn2+ storage in PVO is mainly dominated by the capacitive contribution. This work suggests that intercalating PANI in V2O5 may aid in the future development of advanced cathodes for other multivalent metal ion batteries.

Study on compressive mechanical properties of nanohydroxyapatite reinforced poly(vinyl alcohol) gel composites as biomaterial.

Nanohydroxyapatite reinforced poly(vinyl alcohol) (nano-HA/PVA) gel composites has been proposed as a promising biomaterial to replace diseased or damaged articular cartilage. In this paper, nano-HA/PVA gel composites were prepared by in situ synthesis nano-HA particles in PVA solution and accompanied with freeze/thaw method. The influence of nano-HA content, PVA concentration and freeze/thaw cycle times on the compressive mechanical behavior of nano-HA/PVA gel composites were evaluated using mechanical test equipment. The results showed that the compressive mechanical behavior of nano-HA/PVA gel composites was similar to that of natural articular cartilage, which held special viscoelastic characteristics. Both the compressive strength and modulus of the composites improved correspondingly with the rise of freeze/thaw cycle times and PVA concentration. The compressive strength and modulus of nano-HA/PVA gel composites firstly increased and then presented decreasing trend with the rise of nano-HA content. Furthermore, the compressive modulus of the composites improved exponentially with the rise of compressive strain ratio.

Core-shell structured NaYF4:Yb,Tm@CdS composite for enhanced photocatalytic properties.

NaYF4:Yb,Tm upconversion nanocrystals with hexagonal structure possess excellent photoluminescence emission characteristics. Under near infrared (NIR) light irradiation, the Yb3+ ions act as sensitizers to absorb the NIR light and transform NIR light into ultraviolet (UV) and visible (Vis) light continuously. Hybrid NIR-activated photocatalysts can be fabricated by combining upconversion nanocrystals with various semiconductor nanocrystals. In this paper, NaYF4:Yb,Tm micro-rods were hydrothermally synthesized with oleic acid as capping ligand. The NaYF4:Yb,Tm@CdS composite was fabricated by in situ generation of CdS nanoclusters on the surface of NaYF4:Yb,Tm micro-rods. The morphologies and structures of NaY4:Yb,Tm and NaYF4:Yb,Tm@CdS were characterized by XRD, SEM, TEM, XPS, UV-Vis and PL spectroscopy. The results of photocatalytic experiments indicated that the NaYF4:Yb,Tm@CdS composite displayed photocatalytic activity under NIR irradiation. In comparison with pure CdS, the photocatalytic ability of NaYF4:Yb,Tm@CdS composite under Vis-NIR irradiation was obviously enhanced. 82% of RhB was degraded by NaYF4:Yb,Tm@CdS catalyst within 75 min under Vis-NIR irradiation, which was more effective than pure CdS (65% degradation of RhB).

[Effect of surface modification on biotribological properties of ultra-high molecular weight polyethylene artificial joints].

Friction and wear of ultra-high molecular weight polyethylene is a major cause of artificial joint failure. According to mechanism of surface modification method, friction reduction and wear-resistance properties of UHMWPE were improve by several kinds of surface modification methods. Meanwhile, this do not damage the internal structure and properties of UHMWPE. In the process, condition is easy to control and operation is simple. However, reaction time of radiation crosslinking method is too long, the material will be oxidized embrittlement; Monomer itself homopolymerization are seriously in the process of surface grafting; The injection layer of ion implantation methods is very thin and easy to be destroyed. Objective in order to provide a reference for further research on the biotribological properties of ultra-high molecular weight polyethylene artificial joints. At present, as the researches of UHMWPE material main focus on abrasion resistance, and application in the clinical trial is the focus of research, it has a wide prospect in the future.

Threshold Dependence of Deep- and Near-subwavelength Ripples Formation on Natural MoS2 Induced by Femtosecond Laser.

Deep sub-wavelength ripples (DSRs) and near sub-wavelength ripples (NSRs) with uniform periods of ~160 nm and ~660 nm generated at the MoS2-vacuum interface is reported for the first time by the processing of femtosecond laser (800 nm, 120 fs, 1 kHz) in this paper. The DSRs and NSRs formation fluence thresholds are experimentally determined as 160 mJ/cm(2) and 192 mJ/cm(2), respectively. In addition, the ripple period is insensitive to the pulse number. Moreover, Raman analyses show that the MoS2 lattice in the irradiated area does not exhibit oxidation at room environment and the crystalline representation is well preserved in NSRs region. We attribute our result to the joint interactions of the spallation and sublimation of layered MoS2 together with the laser induced surface plasmon polaritons and propose an explanation to the threshold dependence of the ripple period. Our study provides some insights for ultrafast laser-matter interactions and indicates a simple effective method for future nano-fabrication of MoS2.

[Research on repair strategies for articular cartilage defects].

Articular cartilage damage is very common in clinical practices. Due to the low self-healing abilities of articular cartilage, the repair strategies for articular cartilage such as arthroscopic lavage and debridement,osteaochondral or chondrocytes transplantation, tissue engineering and hydrogel based artificial cartilage materials are the primary technologies of repairing articular cartilage defect. In this paper,the main repair strategies for the articular cartilage damage and the advantages or disadvantages of each repair technology are summarized. The arthroscopic lavage and debridement is successful in treating the early stage of osteoarthritis. Osteochondral and chondrocytes transplantation are beneficial to treat small full thickness defects. The technology of tissue engineering becomes a new method to heal articular cartilage damage, but the major problem is the absence of bonding strength between the implants and natural defect surfaces. Hydrogel based artificial cartilage possesses similar bio-mechanical and bio-tribological performances to that of natural articular cartilage. However, both bioactivity and interfacial bonding strength between the implant and natural cartilage could be further improved. How to simultaneously optimize the mechanical and bioactive as well as biotribological properties of hydrogel based materials is a focus problem concerned.

A heterometallic sandwich complex of europium(II) for luminescent studies.

A divalent europium complex [(L(Ph))(2)Eu{K(THF)(2)}(2)] (L(Ph) = Ph(2)Si(NAr)(2), Ar = 2,6-(i)Pr(2)C(6)H(3)) (THF = Tetrahydrofuran) (2), which has a sandwich structure with potassium-arene π interactions, was synthesized in high yield via a one-pot process. This complex has been fully characterized, and luminescent studies showed that the 528 nm emission peak can be attributed to the 4f-5d transition of Eu(2+).

Cubic and doubly-fused cubic samarium clusters from Sm(II)-mediated reduction of organic azides and azobenzenes.

A polynuclear samarium imido complex [(L)Sm(4)(µ(3)-NSiMe(3))(4)] (2) featuring a cubane-like cluster has been synthesized from the reaction of an organic azide and a samarium(II) complex [(L)SmI(2)Li(2)(THF)(Et(2)O)(2)] (1). In addition, this divalent samarium starting material (1) reacts with azobenzene to give the first example of a well-defined doubly-fused cubic imido-cluster [(L)Sm(6)(µ(3)-NPh)(4)(µ(4)-NPh)(2)I(2)(THF)(2)] (4) in addition to a major cubic complex [(L)Sm(4)(µ(3)-NPh)(4)] (3).