A template-free method for preparation of cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure for oxygen reduction.

Designing and preparing porous materials without using any templates is a challenge. Herein, single-nozzle electrospinning technology coupled with post pyrolysis is applied to prepare cobalt nanoparticles embedded in N-doped carbon nanofibers with a hierarchical pore structure (HP-Co-NCNFs). The resultant HP-Co-NCNFs have lengths up to several millimeters with an average diameter of 200 nm and possess abundant micro/meso/macropores on both the surface and within the fibers. Such a microstructure endows the surface area as high as 115 m(2) g(-1) . When used as an electrocatalyst for the oxygen reduction reaction (ORR), the HP-Co-NCNFs exhibit outstanding electrochemical performance in terms of activity, methanol tolerance, and durability. The hierarchically porous structure and high surface area can effectively decrease the mass transport resistance and increase the exposed ORR active sites. The sufficient amount of exposed ORR active sites along with accessible transport channel and enhanced electrical conductivity may be responsible for the good electrocatalytic performance.

One-pot synthesis and Nb4N5 surface modification of Nb(4+) self-doped KNbO3 nanorods for enhanced visible-light-driven hydrogen production.

Herein, rhombohedral self-doped KNbO3 (S-KN) nanorods were fabricated via a one pot, solvothermal method without using any surfactant. The presence of Nb(4+) in S-KN greatly narrows its band gap and thus extends its photoresponse from UV to the visible light region. Moreover, S-KN/Nb4N5 nanorod heterostructures were obtained by nitriding S-KN nanorods for different times, which exhibited significantly enhanced photocatalytic activity for hydrogen production under visible light irradiation. The junction formed between S-KN and Nb4N5 and the Nb(4+) self-doping of KN are supposed to be responsible for the enhanced photocatalytic activity of S-KN/Nb4N5. This study also paves the way for the synthesis of other similar photocatalysts.

Improving water splitting performance of Cu2O through a synergistic "two-way transfer" process of Cu and graphene.

H2 evolution catalysis has drawn great consideration and effective separation and delivery of the photoelectrons are particularly crucial during the whole process. In this paper, we fabricate porous Cu-Cu2O-graphene nanocomposites via a simple reflux synthesis route, which possess porous structure and excellent catalytic performance for water splitting. With Cu species being added into Cu2O-graphene, the resultant catalyst exhibits improved activity for H2 evolution reaction as compared to Cu2O, Cu-Cu2O and Cu2O-graphene, indicating excellent catalytic performance and potential practical use. We attribute this performance to the synergistic effect of Cu component and graphene, which features: (i) a broader range of light absorption; (ii) faster electron transfer; and (iii) lower recombination possibility of photogenerated electrons and holes. We believe that the Cu species and graphene both contribute greatly to this catalysis process, in which Cu can cooperate with graphene support to extract electrons and pass them to the Pt cocatalyst to form a "two-way transfer" process. It is also believed that this strategy can be extended to other catalysts based on Cu-Cu2O-graphene composites.

Quantifying the discrepancies in the geometric and mechanical properties of the theoretically designed and additively manufactured scaffolds.

In recent years, the triply periodic minimal surface (TPMS) has emerged as a new method for producing open cell porous scaffolds because of the superior properties, such as the high surface-to-volume ratio, the zero curvature, etc. On the other hand, the additive manufacturing (AM) technique has made feasible the design and development of TPMS scaffolds with complex microstructures. However, neither the discrepancy between the theoretically designed and the additively manufactured TPMS scaffolds nor the underlying mechanisms is clear so far. The aims of the present study were to quantify the discrepancies between the theoretically designed and the AM produced TPMS scaffolds and to reveal the underlying mechanisms, e.g., the effect of building orientation on the discrepancy. 24 Gyroid scaffolds were produced along the height and width directions of the scaffold using the selective laser melting (SLM) technique (i.e., 12 scaffolds produced in each direction). The discrepancies in the geometric and mechanical properties of the TPMS scaffolds were quantified. Regarding the geometric properties, the discrepancies in the porosity, the dimension and the three-dimensional (3D) geometry of the scaffolds were quantified. Regarding the mechanical properties, the discrepancies in the effective compressive modulus and the mechanical environment (strain energy density) of the scaffolds were evaluated. It is revealed that the porosity in the AM produced scaffold is approximately 12% lower than the designed value. There are approximately 68.1 ± 8.6% added materials in the AM produced scaffolds and the added materials are mostly distributed in the places opposite to the building orientation. The building orientation has no effect on the discrepancy in the scaffold porosity and no effect on the distribution of the added materials (p > 0.05). Regarding the mechanical properties, the compressive moduli of the scaffolds are 24.4% (produced along the height direction) and 14.6% (produced along the width direction) lower than the designed value and are 49.1% and 43.6% lower than the µFE counterparts, indicating that the imperfect bonding and the partially melted powders have a large contribution to the discrepancy in the compressive modulus of the scaffolds. Compared to the values in the theoretically designed scaffold, the strain energy densities have shifted towards the higher values in the AM produced scaffolds. The findings in the present study provide important information for the design and additive manufacturing of TPMS scaffolds.

The anisotropic elastic behavior of the widely-used triply-periodic minimal surface based scaffolds.

The Triple Periodic Minimal Surface (TPMS) has emerged as a new approach for producing open cell porous scaffolds for biomedical applications. However, different from the traditional scaffolds, the TPMS scaffolds always exhibit anisotropic elastic behaviors and consequently the simple mechanical testing is not capable to provide a full characterization of their mechanical behaviors. Additionally, it is still unclear if the TPMS scaffolds possess the similar anisotropic behaviors as the natural bones. The aim of the present study was to analyze the anisotropic elastic behaviors of TPMS based scaffolds using the numerical homogenization method and the analytical analysis approach. Five widely-used TPMS scaffold topologies (Diamond, Gyroid, Fischer-Koch S, Schwarz P and F-RD) were investigated. The independent elastic constants were determined from the analytical analysis and then, the values for these independent constants were determined using the finite element (FE) unit cell models of the scaffolds combined with the periodic boundary condition. The analytical analysis revealed that the Diamond, Gyroid and Fischer-Koch S topologies are threefold rotational symmetric and consequently have seven independent elastic constants. The Schwarz P and F-RD topologies are cubic symmetric and have three independent elastic constants. The FE analysis showed that the Diamond, Gyroid and Fischer-Koch S based scaffolds have only three non-zero independent elastic constants, implying the cubic symmetric property of these scaffolds. All the independent elastic constants decreased quadratically with the increase of scaffold porosity. The absolute difference between the Zener anisotropic factor and one increased the most for the Gyroid based scaffold, while the value for the Fischer-Koch S based scaffold increased the least. The present study revealed that all the five TPMS scaffolds possess cubic symmetry, limiting their anisotropic behaviors. The information on the Zener anisotropic factor and the relationship between the scaffold elastic constants and the porosity can facilitate the selection and design of scaffolds in biomedicine and relevant fields.

Band Gap Engineering of In2TiO5 for H2 Production under Near-infrared Light.

In2TiO5, containing both early transition metal (d(0)) and p-block metal (d(10)), is a very promising candidate for possible application in H2 production because of its suitable edges of conduction and valence bands and the crystal structure, which is considered to favor mobility of charge carriers. Herein we report, for the first time, the synthesis of novel oxygen vacancies (OV), N-doped In2TiO5 (OV,N-In2TiO5) with controllable band gap. The resultant OV,N-In2TiO5 sample was prepared by a multistep sol-gel calcination process and studied as a near-infrared (NIR) light-driven photocatalyst for H2 production. OV and N-doping can effectively extend the photoresponse of In2TiO5 to the NIR region due to an interband springboard and the reduced band gap, thus leading to efficient NIR light photocatalytic H2 production activity with Pt as a cocatalyst.

Ultrasensitive electrochemical immunosensors for multiplexed determination using mesoporous platinum nanoparticles as nonenzymatic labels.

An ultrasensitive multiplexed immunoassay method was developed at a disposable immunosensor array using mesoporous platinum nanoparticles (M-Pt NPs) as nonenzymatic labels. M-Pt NPs were prepared by ultrasonic method and employed to label the secondary antibody (Ab2) for signal amplification. The immunosensor array was constructed by covalently immobilizing capture antibody (Ab1) on graphene modified screen printed carbon electrodes (SPECs). After the sandwich-type immunoreactions, the M-Pt-Ab2 was bound to immunosensor surface to catalyze the electro-reduction of H2O2 reaction, which produced detectable signals for readout of analytes. Using breast cancer related panel of tumor markers (CA125, CA153 and CEA) as model analytes, this method showed wide linear ranges of over 4 orders of magnitude with the detection limits of 0.002 U mL(-1), 0.001 U mL(-1) and 7.0 pg mL(-1) for CA125, CA153 and CEA, respectively. The disposable immunosensor array possessed excellent clinical value in cancer screening as well as convenient point of care diagnostics.

Two-step fabrication of a porous γ-In2Se3 tetragonal photocatalyst for water splitting.

A porous semiconductor photocatalyst, γ-In2Se3, was first synthesized by a two-step hydrothermal-calcining process. It was shown that the porous γ-In2Se3 tetragons have superior photocatalytic activity for water splitting over γ-In2Se3 nanoparticles and commercial counterparts, which might be attributed to the combined effect of stronger UV light absorption properties and a porous structure.