Effect of diamond-like carbon (DLC) on the properties of the NiTi alloys

NiTi alloy has found wide application in the biomedical field due to its unique shape memory effect, superelasticity and biocompatibility. However, the materials are vulnerable to surface corrosion and the most serious issue is out-diffusion of toxic Ni ions from the substrate into body tissues and fluids. In this paper, NiTi alloys were coated with diamond-like carbon (DLC) fabricated by plasma immersion ion implantation and deposition (PIIID) to improve their corrosion resistance and blood compatibility without sacrificing their shape memory effect and superelasticity. The structure of the films and the depth profiles between the films and substrate were studied using Raman spectroscopy and XPS, respectively. The phase transformation temperature, superelasticity, anticorrosion behavior and Ni ions release of the coated and uncoated sample were investigated by DSC, tensile tests, potentiodynamic polarization and AAS, respectively. The hemocompatibilty of the coated and uncoated samples was measured using clotting time and platelet adhesion. The results shows that the films is DLC accompanying with the formation of the mixing layer, and the DLC films can markedly improve the corrosion resistance and the hemocompatibility, obviously increase the ratio of albumin-to-fibrinogen and effectively block the Ni ions release of the NiTi alloys without sacrificing its superelasticity and changing its phase transformation temperature. The research results suggest DLC films prepared by PIIID could improve the in vivo performance of NiTi alloys implanted into the human body.     

New Insight into Procedure of Interface Electron Transfer through Cascade System with Enhanced Photocatalytic Activity

Recombination of photogenerated electron–hole pairs is extremely limited in the practical application of photocatalysis toward solving the energy crisis and environmental pollution. A rational design of the cascade system (i.e., rGO/Bi₂WO₆/Au, and ternary composites) with highly efficient charge carrier separation is successfully constructed. As expected, the integrated system (rGO/Bi₂WO₆/Au) shows enhanced photocatalytic activity compared to bare Bi₂WO₆ and other binary composites, and it is proved in multiple electron transfer (MET) behavior, namely a cooperative electron transfer (ET) cascade effect. Simultaneously, UV–vis/scanning electrochemical microscopy is used to directly identify MET kinetic information through an in situ probe scanning technique, where the “fast” and “slow” heterogeneous ET rate constants (K_eff) of corresponding photocatalysts on the different interfaces are found, which further reveals that the MET behavior is the prime source for enhanced photocatalytic activity. This work not only offers a new insight to study catalytic performance during photocatalysis and electrocatalysis systems, but also opens up a new avenue to design highly efficient catalysts in photocatalytic CO₂ conversion to useful chemicals and photovoltaic devices.     

A novel self-assembly with two acetohydrazide zinc porphyrins coordination polymer for supramolecular solar cells

Two new acetohydrazide zinc porphyrin with different donor units based Mn (Ⅱ) ion coordination polymers (CPsx, x=1,2) have been designed, synthesized, and well-characterized. Two coordination polymers and anchor porphyrin (ZnPA) self-assembly by metal-ligand axial coordination to modify the nano-structured TiO₂ electrode surface has been investigated in photoelectrochemical device. Our results reveal that the self-assemblies devices show significantly improved photocurrent conversion efficiency. Particularly, CPs1 based solar cell showed higher short circuit current density and conversion efficiency. Their optical performance, electrochemical impedance spectroscopy and transient photovoltage decay were also investigated to further understand the photoelectrochemical results. In addition, the assembled modes of the assemblies immobilized on TiO₂ electrode surfaces were also verified by transmission electron microscopy (TEM), theory calculations and energy dispersive X-ray spectroscopy (EDX).     

Facile fabrication of a binary NiCo phosphide with hierarchical architecture for efficient hydrogen evolution reactions

Exploring and designing efficient non-noble catalysts formed by element doping and nanostructure modification for the hydrogen evolution reaction (HER) is of critical importance with respect to sustainable resources. Herein, we have prepared a three-dimensional binary NiCo phosphide with hierarchical architecture (HA) composed of NiCoP nanosheets and nanowires grown on carbon cloth (CC) via a facile hydrothermal method followed by oxidation and phosphorization. Due to its unique hierarchical nanostructure, the NiCoP HA/CC electrocatalyst exhibits excellent performance and good working stability for the HER in both acidic and alkaline conditions. The obtained NiCoP HA/CC shows excellent HER activity with a low potential of 74 and 89 mV at 10 mA cm⁻², a small Tafel slope of 77.2 and 99.8 mV dec⁻¹ and long-term stability up to 24 h in acidic and alkaline electrolyte, respectively. NiCoP HA/CC, a non-noble metal material, is a promising electrocatalyst to replace noble metal-based electrocatalysts for the HER.     

Side chain effect on photovoltaic properties of dibenzo[a,c]phenazine based donor–acceptor polymers

The electron–donor polymers containing dibenzo[a,c]phenazine (BPz) derivatives with 2,7-alkyl and 11,12-alkoxy substituted, PBDT-BPzC and PBDT-OBPz, respectively, were synthesized to investigate the photovoltaic effect of different side chain substitutions. The polymers exhibit similar physical properties, except the HOMO and LUMO of PBDT-BPzC are 0.18 and 0.15 eV deeper than PBDT-OBPz, resulting in the V_oc of polymer solar cells (PSCs) based on PBDT-BPzC are above 0.1 V higher than that of PBDT-OBPz. With the contribution of the superior V_oc, polymer PBDT-BPzC showed preferable photovoltaic performances, and the PCE reached 4.44%, which is 0.49% higher than PBDT-OBPz. This research reveals a preferred side chain substituted way to modify BPz unit, and gives an optimally developing the dibenzo[a,c]phenazine derivatives based electron–donor polymers.     

Salmonella typhimurium resistance on pulsed electric fields associated with membrane fluidity and gene regulation

Effects of different growth temperatures on cytoplasmic membrane fluidity and phospholipids phase transition temperature (T_m) of Salmonella typhimurium and resistance to pulsed electric field (PEF) inactivation, as well as the expression of stress-related genes and fatty acid biosynthesis-associated genes were investigated. Results indicated that the PEF resistance of S. typhimurium increased as growth temperature increased. S. typhimurium cultivated at 10 °C exhibited the lowest PEF resistance with the reduction of 4.23 log₁₀ CFU/mL, while the reduction of 2.10 log₁₀ CFU/mL was found in S. typhimurium cultivated at 45 °C under the same PEF treatment, due to the up-regulation of the expression of fabA gene, which was characterized by the lowest T_m of membrane phospholipids and the greatest membrane fluidity. Although the expression of alternative sigma factors were altered by growth temperature, these genes were not essential for S. typhimurium to develop PEF resistance, suggesting that the PEF resistance modified by growth temperature could be caused by alterations in membrane fluidity.Industrial relevancePulsed electric fields (PEF) treatment has been widely applied in nonthermal pasteurization and increasingly focused on synergistic combinations with other techniques such as thermal treatment, sonication and antibacterial agents to improve the efficacy of PEF to inactivate micro-organisms. Our results indicated that S. typhimurium cultivated at relatively lower temperature was easily inactivated by PEF, due to the up-regulation of the expression of fabA gene, which was characterized by the lowest phase transition temperature of cytoplasmic membrane phospholipids and the greatest membrane fluidity. Therefore, the underlying mechanism of alterations in PEF resistance of S. typhimurium induced by growth temperature was explored to achieve better understanding of microbial inactivation by PEF.     

NanoSIMS investigation of passive oxide films on high-Cr cast iron

The discrete depth characteristics of thin passive oxide films were investigated using high-resolution electron microprobe and nanoscale secondary ion mass spectrometry (NanoSIMS). A novel NanoSIMS method involving a Cs layer deposition before Cs⁺ sputtering was employed for the first time to determine the elemental distribution at different sub-layers of a passive film. The film was formed in air on the surface of a multi-phase microstructure of high-chromium cast iron (HCCI). It was found that the film composition and thickness varied according to the underlying microstructure phase. Based on the microprobe and NanoSIMS results, the influence of the HCCI passive film thickness and composition on the localized passivity breakdown has been proposed.     

Synergism of molecular weight,crystallization and morphology of poly(3-butylthiophene) for photovoltaic applications

A serial of poly(3-butylthiophene) (P3BTs) with molecular weights (MWs) ranged from 7 kDa to 50 kDa is synthesized and characterized. The DSC studies show that the thermal property and crystallinity of P3BT increase with MWs within the range from 7 kDa to 25 kDa, then decrease with further higher MW. The characteristic morphologies of incontinuous crystalline nanofibrils, interconnected nanofibrillar networks, and relative large clusters associate to low, medium and high MW P3BTs, respectively, demonstrate the strong correlation between MW, crystallinity and morphology of P3BT. It is found that the P3BT could be re-considered as the promising candidate for applications in organic optoelectronics if synergism of the crystallinity and morphology could be precisely controlled via tuning molecular weight. The polymer solar cells (PSCs) device based on P3BT with medium MW achieves an attractive power conversion efficiency of 3.5%, which is, to the best of our knowledge, the record for P3BT/PC₆₁BM PSCs and comparable to the well-studied P3HT devices.     

An ELIME-array for detection of aflatoxin B1 in corn samples

The aim of the present work was the development of an ELIME-array to achieve simple and rapid detection of AFB₁ in corn samples. The system is based on an indirect competitive ELISA format using magnetic beads as immobilisation support and eight magnetised screen-printed electrodes as electrochemical transducers.After an optimisation study, a corn sample treatment, employing an extraction in acetonitrile/water followed by a clean-up step and solvent evaporation, was selected.For the construction of the calibration curve, which was used to evaluate both evaluation of the matrix effect on the performances of the ELIME-array and for the analysis of Certified Reference Materials (CRMs), standard solutions of AFB₁ were added to blank dried corn extracts reconstituted in PBS. The detection limit and the sensitivity of the assay were calculated to be 0.6 ng mL^?1 and 1.5 ng mL^?1, respectively.Precision (11–26%) and recovery (95–114%) data of the ELIME-array, determined by analysing four CRMs, have shown that the proposed system appears suitable as a screening tool for the analysis of AFB₁ in corn samples.     

Facile synthesis of MoS2/N-doped macro-mesoporous carbon hybrid as efficient electrocatalyst for hydrogen evolution reaction

A novel three-dimensional (3D) hybrid consisting of molybdenum disulfide nanosheets (MoS₂) uniformly bound at N-doped macro-mesoporous carbon (N-MMC) surface was fabricated by the solvothermal method. The resulting MoS₂/N-MMC hybrid possesses few-layer MoS₂ nanosheets structure with abundant edges of MoS₂ exposed as active sites for hydrogen evolution reaction (HER), in sharp contrast to large aggregated MoS₂ nanoflowers without N-MMC. The high electric conductivity of N-MMC and an abundance of exposed edges on the MoS₂ nanosheets make the hybrid excellent electrocatalytic performance with a low onset potential of 98 mV, a small Tafel slope of 52 mV/decade, and a current density of 10 mA cm^?2 at the overpotential of 150 mV. Moreover, the MoS₂/N-MMC hybrid exhibits outstanding electrochemical stability and structural integrity owing to the strong bonding between MoS₂ nanosheets and N-MMC.