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The intrinsic carbon defects including pentagons, vacancies and sp3-hybridized carbon have recently been proposed as efficient reactive sites for oxygen reduction reaction (ORR). Nevertheless, it is still a great challenge to controllably introduce the intrinsic defects into carbon materials. Herein, a universal defect-engineering method via vaporized salt is reported to modify the N-doped carbon surface with abundant sp3-hybridized carbon defects. At an elevated temperature, the vaporized sodium chloride is found to selectively modulate the surface structure of carbon material. The obtained carbon-based electrocatalyst delivers an outstanding electrocatalytic ORR property with a half-wave potential (E1/2) of 0.85 V vs. RHE and an excellent performance in zinc air battery (ZAB) test. The analysis of components and structures of surface elements via XANES and XPS reveals that the increasing sp3-hybridized carbon defects, induced by the vaporized-salt modification, are responsible for the enhancement of ORR performance. The theoretical calculations further suggest the sp3 component hybridizes with original sp2 carbon, forming efficient sp2/sp3 hybridized carbon sites towards ORR. Additionally, other halide salts are proved to have the similar effect on promoting ORR activity and this method can expand to other carbon-based materials, suggesting its universality and significance in synthesis of defect-rich carbon-based materials.

Developing an efficient catalyst for hydrogen (H2) generation from hydrolysis of ammonia borane (AB) to significantly improve the activity for the hydrogen generation from AB is important for its practical application. Herein, we report a novel hybrid nanostructure composed of uniformly dispersed Co@Co2P core-shell nanoparticles (NPs) embedded in N-doped carbon nanotube polyhedron (Co@Co2P/N–CNP) through a carbonization-phosphidation strategy derived from ZIF-67. Benefiting from the electronic effect of P doping, high dispersibility and strong interfacial interaction between Co@Co2P and N-CNTs, the Co@Co2P/N–CNP catalyst exhibits excellent catalytic performance towards the hydrolysis of AB for hydrogen generation, affording a high TOF value of 18.4 mol H2 mol metal−1 min−1 at the first cycle. This work provides a promising lead for the design of efficient heterogeneous catalysts towards convenient H2 generation from hydrogen-rich substrates in the close future.

Ammonia synthesis by the electrochemical technique is a promising solution to replace the energy-intensive Haber–Bosch process in industry, which inevitably requires high-performance catalysts. However, the development of catalysts is still limited by the inferior activation of the stable NN bond. Herein, a robust N2-activation mode is proposed, which addresses the electron donation mechanism to both the N2 antibonding orbitals of py and pz, simultaneously. Following this strategy, the single cluster catalyst (SCC) of Fe4/GaS has realized remarkable nitrogen reduction reaction (NRR) performance with an ultra-low overpotential (η) of 0.08 V by density functional theory (DFT) calculations. N2 is completely activated in a side-on adsorption configuration on the hollow site of Fe4/GaS, where both degenerate N2–π* orbitals are properly hybridized to the frontier orbitals of the Fe4 cluster, as proven by fragment orbital analysis. This work proposes an efficient strategy for N2 activation, and also provides a valid design guideline for further research.

Highly efficient bifunctional electrocatalysts towards sluggish oxygen reduction and evolution reactions (ORR and OER) are of great significance for cathode catalysis of rechargeable metal–air batteries. Herein, we report a one-pot pyrolysis strategy to construct binary transition metal oxide (TMO) interfaces on a nitrogen doped porous carbon framework (CN) for bifunctional oxygen reaction catalysis. The constructed Fe3O4/Co3O4 interfaces not only help promote the stabilization of Fe2+ ions, but also generate abundant oxygen vacancies on the surface of composite catalysts (Fe3O4/Co3O4-CN), which boost the intrinsic oxygen reaction activity. The Fe3O4/Co3O4-CN catalyst exhibits a bifunctional electrocatalytic performance with a significantly lowered potential difference (ΔE) of 0.68 V between the half-wave potential of the ORR (E1/2) and the potential of the OER at a current density of 10 mA cm−2 (Ej=10), rivaling the best performance of previously reported bifunctional TMO catalysts to the best of our knowledge. The rechargeable Zn–air battery with Fe3O4/Co3O4-CN as the cathode catalyst exhibits superior performance with an energy density of 1045.82 W h kgZn−1 and a peak power density of 105.7 mW cm−2, as well as excellent cycling stability (over 80 h at a current density of 10 mA cm−2), demonstrating our new bifunctional oxygen electrocatalyst as a promising candidate for practical energy storage applications.

It is of great importance to develop efficient and low-cost oxygen evolution reaction (OER) electrocatalysts for electrochemical water splitting. Herein, S doped NiCoVOx nanosheets grown on Ni-Foam (S-NiCoVOx/NF) with a modified electronic structure have been prepared through a facile one-step hydrothermal method. The as-prepared S4.06-NiCoVOx/NF exhibits outstanding OER activity with low overpotentials of 248 mV and 289 mV to deliver current densities of 10 mA cm−2 and 100 mA cm−2, respectively, and a small Tafel slope of 46.2 mV dec−1 in 1.0 M KOH electrolyte. These values are much lower than those obtained for most of the recently reported non-noble metal-based electrocatalysts under similar experimental conditions. This study provides a simple approach to rational design of efficient and cost-effective OER electrocatalysts for practical application of electrochemical water splitting.

Circulating tumor cells (CTCs) are an important part of liquid biopsy as they represent a potentially rich source of information for cancer diagnosis, monitoring, prognosis, and treatment guidance. It has been proved that the nanotopography interaction between cells and the surface of CTC detection platforms can significantly improve the capture efficiency of CTCs, whereas many mature nanostructure substrates have been developed based on chemistry materials. In this work, a natural biointerface with unique biological properties is fabricated for efficient isolation and nondestructive release of CTCs from blood samples using the cancer cell membranes. The cell membrane interfaces are proved to have a good antiadhesion property for nonspecific cells because of their own electronegativity. A natural surface nanostructure is provided by the cancer cell membrane to nicely match with the surface nanotopography of CTCs. Bovine serum albumin (BSA) as a linker and DNA aptamer against the epithelial cell adhesion molecule (EpCAM) as a specific affinity molecule are then introduced onto the cell membrane interfaces to achieve the highly efficient and specific capture of CTCs. Finally, the captured target cells can be intactly released from the substrate using the complementary DNA sequence with controlling the incubation time. This study provides a smart strategy in the development of a natural biological interface for the isolation and release of CTCs with high purity.

One of the key challenges with atomic catalysts (single, double, and triple atom catalysts) is the relatively low loading of active materials, resulting in the low mass or volume activity of catalysts, which hinders their rapid development in the field of catalysis. Herein, using density functional theory (DFT), we explore a series of atomic catalysts with heterostructured substrate, graphdiyne and graphene (GDY/Gra), for the nitrogen reduction reaction (NRR). The theoretical mass loading of active metal atoms can exceed 35.0 wt% in the triple atom catalyst (TAC), which could be reached through the optimal substrate and suitable precursors in experiments. Among the designed atomic catalysts, Fe3-GDY/Gra with a theoretical mass loading of 35.8 wt% shows outstanding catalytic activity for the electrocatalytic NRR with a potential of −0.26 V vs. the reversible hydrogen electrode (RHE). Moreover, the proposed TACs show better catalytic activity for the NRR than single atom catalysts (SACs) and double atom catalysts (DACs) due to the unique properties of M3 (M = Mn, Fe, Co, and Ni) active sites, which provide more electrons for activating N2, but also have a weak adsorption to more easily release products. These findings provide a new strategy for designing atomic catalysts with high loading, high stability, and high activity.

The recent development in plasmon-enhanced electrochemical hydrogen production provides an alternative approach to address the bottleneck of low hydrogen production efficiency in the conventional photocatalysis. To achieve high-efficiency plasmonic catalysis, the development of catalytically active Schottky heterostructure is essential. Herein, we propose a 3D bicontinuous nanoporous plasmonic heterostructure for hydrogen evolution reaction (HER) by growing HER-active monolayer MoS2 on the internal surfaces of plasmonic 3D nanoporous gold (MoS2@NPG). The catalytically active plasmonic heterostructure with a large specific surface area and high electric conductivity exhibits superior photoelectrochemical activities towards electrochemical hydrogen production at both low onset potential of −70 mV vs RHE and the Tafel slope of 38 mV dec−1 under visible light illumination. The outstanding HER performance can be attributed to the efficient transfer of plasmon-generated hot electrons from NPG to monolayer MoS2 as well as the effective electron–hole separation by the Schottky barriers at MoS2/NPG interfaces.

Localized surface plasmon resonance (LSPR) excitation enhanced chemical and electrochemical reactions represent a promising pathway for solar-to-chemical energy conversion. However, plasmonic catalysts usually suffer from low collection efficiency of hot charge carries generated by LSPR excitation due to short lifetime of hot carriers and fast electron-hole recombination. Schottky barriers between plasmonic catalysts and semiconducting supports have been utilized to prevent the electron-hole recombination. However, the interfacial barriers also hinder low-energy hot charge collection and thus affect solar-to-chemical energy conversion efficiency. Here we report that bicontinuous nanoporous gold as a Schottky barriers-free direct plasmonic catalyst can significantly enhance electro-oxidation of alcohol molecules. A high energetic hole yield of 0.486% is achieved, which is 4 times higher than that of discrete plasmonic AuAg nanoparticles. The direct plasmonic catalyst offers the highest methanol oxidation current density of 531 µA cm−2 among all known Au catalysts. This work provides compelling evidence that higher hot carrier collection efficiency can be achieved from direct plasmonic electrocatalysis without the assistance of Schottky junctions and has important implications in developing high efficiency plasmonic catalysts for photo-enhanced electrochemical reactions.

Three-dimensional porous materials with bicontinuous open porosity represent a new class of functional materials for various applications. Top-down dealloying has been demonstrated to be one of the most effective ways to fabricate 3D porous materials. Vapor phase dealloying, which makes use of the saturated vapor pressure difference between the constituent components in an alloy for selectively removing a less stable element or phase, is a promising versatile method for fabricating porous materials from active metals to inorganic elements. Here, using nickel-zinc and germanium-zinc alloys as the prototypes of single-phase and two-phase precursors, respectively, we report the fabrication of 3D bicontinuous porous Ni and Ge by vapor phase dealloying on the basis of selective element or selective phase evaporations. We also show the incorporation of vapor phase dealloying with chemical vapor deposition for the one-pot growth of 3D nanoporous graphene and the functional applications of vapor phase dealloyed porous Ge as Li ion battery electrodes. This study shines lights on the versatility of vapor phase dealloying for the fabrication of bicontinuous porous materials for a wide range of functional applications.

The majority of current methods of isolating circulating tumor cells (CTCs) rely on a biomarker. However, the isolation efficiency may be compromised due to the heterogeneity of CTCs. In this work, a simple and broad-spectrum method is established to efficiently isolate the heterogeneous CTCs from patient blood samples using tannic acid (TA)-functionalized magnetic nanoparticles (MNPs). The TA-functionalized MNPs (MNPs-TA) inhibit the nonspecific adhesion of peripheral blood mononuclear cell (PBMC) and enhance cancer cell capture, resulting from the unique interaction between TA and glycocalyx on cancer cells. The MNPs-TA was demonstrated to effectively capture seven kinds of cancer cells (HeLa, PC-3, T24, MAD-MB-231, MCF-7, HT1080, A549) from artificial samples (62.3-93.7%). Moreover, this epithelial cell adhesion molecule (EpCAM)-independent CTC isolation method was also tested using clinical blood samples from patients with different cancers (21 patients), which may provide a universal tool to detect CTCs in the clinic.

The electrochemical reduction of nitrogen (N2) to ammonia (NH3) has attracted attention as an emerging alternative to the traditional Haber–Bosch process to synthesize NH3. Unfortunately, electrocatalytic N2 reduction processes are still very inefficient. Here we report three-dimensional nanoporous gold (NPG) as an efficient and stable electrocatalyst for the N2 reduction reaction at room temperature and atmospheric pressure. NPG can deliver a high NH3 yield rate of 45.7 μg h−1 mg−1cat. and a high faradaic efficiency of 3.41% at an ultralow potential of −0.10 V versus the reversible hydrogen electrode, in 0.1 M HCl solution. These values are much higher than those obtained for most of the reported electrocatalysts under similar experimental conditions. Structural characterization and density functional theory calculations reveal that the excellent electrocatalytic activity of NPG mainly results from the high density of geometrically required surface steps and kinks.

We studied the formation and attenuation of GHz elastic waves in free-standing nanoporous gold films by MeV ultrafast electron diffraction and finite element simulations. By tracing the evolution of the high frequency acoustic waves in time domain, we found that the bicontinuous nanoporous structure in nanoporous gold films results in three-dimensionally acoustic response with low coherence, leading to fast attenuation of the elastic waves in comparison with solid gold films. The morphologically dominated dynamics indicates the nanoporosity plays an important role in the high-frequency acoustic energy relaxation, which shines a light on the applications of dealloyed nanoporous materials in nanodevices and sensors as GHz and THz acoustic filters and dampers.

Electrochemical nitrogen reduction reaction (NRR) at ambient conditions is a highly attractive route for ammonia (NH3) synthesis. However, the NRR suffers from low NH3 yield and Faradaic efficiency (FE) due to the lack of effective electrocatalyst. Here Ag-doped Cu nanosheets grown on carbon paper (Ag-CuNS/CP) have been synthesized and utilized as efficient electrocatalysts for NRR. The doping of Ag leads to the formation of electron-deficient Cu atoms in Ag-CuNS/CP, which can suppress hydrogen evolution reaction and enhance N2 adsorption in neutral media, leading to enhanced NRR activity. In 0.1 M Na2SO4 electrolyte, the Ag-CuNS/CP catalyst exhibits a high FE of 20.9% and a NH3 yield rate of 61.5 µg h-1 mg-1cat. at -0.4 V versus the reversible hydrogen electrode. This study offers a simple but effective approach to design highly active and selective NRR electrocatalysts for NH3 synthesis.

Electrocatalytic nitrogen reduction reaction (NRR) is a highly attractive route for the synthesis of ammonia. However, the efficiency of the electrocatalytic NRR remains low because of the lack of effective catalyst. Here we use density functional theory (DFT) to investigate the effect of alloying Cu with Mn on NRR performance, showing that the incorporation of Mn into Cu structure can greatly improve the NRR performance. Based on the DFT results, we employ a dealloying method to prepare nanoporous CuMn (np-CuMn) alloy as the electrocatalyst for NRR. Thanks to the synergy between Cu and Mn and the nanoporous structure, the as-prepared np-CuMn alloy exhibits a high ammonia yield rate of 28.9 μg h−1 cm−2 with a Faradaic efficiency of 9.83% at −0.3 V versus reversible hydrogen electrode under ambient conditions. Both values are higher than those obtained for most of the reported noble metal catalysts under similar conditions. Our findings offer an opportunity to design high performance NRR catalyst for ammonia synthesis.

Efficient, durable and low-cost electrocatalysts that accelerate sluggish oxygen reduction reaction kinetics are urgently needed for the energy conversion techniques, such as metal-air batteries and fuel cells. In this work, we develop a molten-salt-assisted thermal emitting approach to transform the cheap and easily obtainable bulk ferric (III) oxide powder into a highly efficient Fe single atom catalyst for cathodic oxygen reduction reaction. Benefiting from the strong polarity force of ionized cations and anions, the molten salt effectively facilitates breakage of chemical bonding in bulk Fe2O3 and volatilization of Fe species far below the melting point of Fe2O3 (1841 K), lowering the consumption of energy and time needed in the synthetic procedure. The vaporized Fe species are subsequently anchored onto the surface of nitrogen-doped porous carbon, evolving the single-atom “Fe-N4-O2” site catalyst. The obtained catalyst presents an excellent oxygen reduction reaction performance with half-wave potential of 0.896 V vs RHE in alkaline media, comparable to the most efficient non-precious metal catalysts and outperforming the benchmark system Pt/C. Furthermore, this method is demonstrated to be valid for synthesis of non-noble-metal single atom catalysts (metal = Co, Mn, Cu, Ni) by changing different metal oxides precursors.

Soot particles strongly absorb sunlight and hence act as a short-lived warming agent. Atmospheric aging of soot particles changes their morphology and mixing state and consequently alters their optical properties. Here we collected soot particles at tunnel, urban, mountaintop, and background sites in the North China Plain and analyzed their mixing structures and morphology using transmission electron microscopy. Soot particles were further classified into three types: bare-like, partly coated, and embedded. Bare-like soot particles were dominant at the tunnel site, while most soot particles were of the partly coated or embedded type at other sites. Fractal dimensions (Df) of different types of soot particles ranged from 1.80 to 2.16 and increased in the following order: bare-like < partly coated < embedded. Moreover, their average Df changed from 1.8 to 2.0 from the tunnel to the background site. We conclude that the Df can characterize the shape of soot aggregates reasonably well, and its variation refle...

Tuning surface structures by bottom-up synthesis has been demonstrated as an effective strategy to improve the catalytic performances of nanoparticle catalysts. Nevertheless, the surface modification of three-dimensional nanoporous metals, fabricated by a top-down dealloying approach, has not been achieved despite great efforts devoted to improving the catalytic performance of three-dimensional nanoporous catalysts. Here we report a surfactant-modified dealloying method to tailor the surface structure of nanoporous gold for amplified electrocatalysis toward methanol oxidation and oxygen reduction reactions. With the assistance of surfactants, {111} or {100} faceted internal surfaces of nanoporous gold can be realized in a controllable manner by optimizing dealloying conditions. The surface modified nanoporous gold exhibits significantly enhanced electrocatalytic activities in comparison with conventional nanoporous gold. This study paves the way to develop high-performance three-dimensional nanoporous catalysts with a tunable surface structure by top-down dealloying for efficient chemical and electrochemical reactions., Tuning the ratio of facets in materials can affect catalytic activity but methods to achieve this can be difficult to control. Here, using surfactants during dealloying, the authors prepare nanoporous gold with controlled facet ratios and show how it can significantly improve electrocatalytic activity.

Recovering pure and viable circulating tumor cells (CTCs) from blood has been a challenging task for molecular characterization and functional analysis, which has attracted wide attention these days. Herein, we fabricate a thermoresponsive chitosan nanofiber substrate to effectively capture, purify, and release the target cancer cells, assisted by PNIPAAm brushes and DNA hybridization. The PNIPAAm brushes are designed to enable WBCs to detach from aptamer-PNIPAAm-chitosan-nanofiber (aptamer-P-CNFs) surfaces during the conformational transition. Meanwhile these specific captured CTCs are retained at a high purity. Moreover, effective and intact release of CTCs from the substrates without any foreign agents is realized by complementary sequences efficiently hybridizing with aptamers, and the specific cell release makes CTCs further purified. The present work provides a new strategy in the design of biointerface for recovering target CTCs from whole blood samples with high purity.

Extreme rarity and inherent heterogeneity of circulating tumor cells (CTCs) result in a tremendous challenge for the CTC isolation from patient blood samples with high efficiency and purity. Current CTC isolation approaches mainly rely on the epithelial cell adhesion molecule (EpCAM), which may significantly reduce the ability to capture CTCs when the expression of EpCAM is lost or down-regulated in epithelial-mesenchymal transition. Here, a rapid and highly efficient method is developed to isolate and identify heterogeneous CTCs with high efficiency from patient blood samples using the fluorescent-magnetic nanoparticles (F-MNPs). A dual-antibody interface targeting EpCAM and N-cadherin is fabricated onto the F-MNPs to capture epithelial CTCs as well as mesenchymal CTCs from whole blood samples. The poly(carboxybetaine methacrylate) brushes of excellent antifouling properties are employed to decrease nonspecific cell adhesion. Moreover, the F-MNPs provide a prompt identification strategy for heterogeneous CTCs (F-MNPs+, Hoechst 33342+, and CD45-) that can directly identify CTCs in a gentle one-step processing within 1 h after isolation from patient blood samples. This has been demonstrated through artificial samples as well as patient samples in details.

Dual phase grating x-ray interferometry is compatible with common imaging detectors, and abandons the use of an absorption analyzer grating to reduce the radiation dose. When using x-ray tubes, an absorbing source grating must be introduced into the dual phase grating interferometer. In order to attain a high fringe visibility, in this work we conduct a quantitative coherence analysis of dual phase grating interferometry to find how the source grating affects the fringe visibility. Theoretical analysis shows that with the generalized Lau condition satisfied, the fringe visibility is influenced by the duty cycle of the source grating and the transmission through the grating bar. And the influence of the source grating profile on the fringe visibility is independent of the phase grating type. Numerical results illustrate that the maximum achievable fringe visibility decreases significantly with increasing transmission in the grating bar. Under a given transmission, one can always find an optimal duty cycle to maximize the fringe visibility. These results can be used as general guidelines for designing and optimizing dual phase grating x-ray interferometers for potential applications.

We present a moment-based alternative approach to retrieve multiple scattering contrasts from x-ray analyzer-based imaging. By use of the properties of moments of convolutions, the multiple-image radiography approach is theoretically validated. Furthermore, higher order moments of the object scattering distribution, inaccessible in multiple-image radiography, are simultaneously provided by this alternative approach. It is experimentally demonstrated that the skew and kurtosis information related to the distribution of sub-pixel features within the object can be obtained from those complementary contrasts. Finally, the sensitivity of the retrieved multiple scattering contrasts is investigated experimentally. The finding that the sensitivity is inversely proportional to the square root of the detected photon number essentially indicates that the retrieval of moments with an order higher than two can be achieved without increasing exposure time or dose. The presented alternative approach provides an access to the exploitation of multiple scattering contrasts, which is expected to be useful in biomedical research, materials science, security screening, etc.

Over the last decade, significant progress has been made to develop sensitive devices for the capture of circulating tumor cells (CTCs) from blood of cancer patients. However, simple capture and counting of CTCs cannot provide effective information for understanding the biology of them. In this work, a functional biointerface is fabricated for specific capture and nondestructive release of CTCs from blood samples. A nanostrucure of porous network based on chitosan nanofibers is fabricated by electrospinning, to mimic the function of extracellular matrices, and then the poly(carboxybetaine methacrylate) (pCBMA) brushes integrating onto nanofiber interface provide the effect of interfacial properties to control nonspecific cell adhesion and the multivalent immobilization of aptamers to induce high efficient and specific CTC capture. Furthermore, a complementary sequence is used to efficiently hybridize with the aptamer to achieve nondestructive release of the captured target cells, assisted by the flexible space provided by pCBMA brushes. This work also shows how nanostructure and the interface molecules regulate the morphology of the captured CTCs, and reveals the importance of the controllable cell morphology on biointerface for an effective nondestructive release of the captured CTCs.

Recently, a novel three-image algorithm has been proposed to retrieve the sample’s absorption, refraction, and scattering properties in x-ray analyzer-based imaging. The feasibility of the three-image algorithm was validated by synchrotron radiation experiments. However, it is unclear yet whether the estimated refraction and scattering signals are biased or not and how the analyzer angular position affects the biases in the estimated signals. For this purpose, the biases of the extracted refraction and scattering signals are theoretically derived for the three-image algorithm. The theoretical models are further confirmed by numerical experiments. The results show that both the estimated refraction and scattering signals are biased, and the biases are strongly dependent on the analyzer angular position. Besides, the biases also show dependence on the sample’s refraction and scattering properties locally. Those results can be used as general guidelines to optimize experimental parameters for bias reduction and accurate imaging of different features within the sample.

Nitrogen-doped graphene exhibits high electrocatalytic activity toward the oxygen reduction reaction (ORR), which is essential for many renewable energy technologies. To maximize the catalytic efficiency, it is desirable to have both a high concentration of robust nitrogen dopants and a large accessible surface of the graphene electrodes for rapid access of oxygen to the active sites. Here, 3D bicontinuous nitrogen-doped mesoporous graphene synthesized by a low-temperature carbide-mediated graphene-growth method is reported. The mesoporous graphene has a mesoscale pore size of ≈25 nm and large specific surface area of 1015 m2 g-1 , which can effectively host and stabilize a high concentration of nitrogen dopants. Accordingly, it shows an excellent electrocatalytic activity toward the ORR with an efficient four-electron-dominated pathway and high durability in alkaline media. The synthesis route developed herein provides a new economic approach to synthesize bicontinuous porous graphene materials with tunable characteristic length, porosity, and chemical doping as high efficiency electrocatalysts for a wide range of electrochemical reactions.

Well-ordered MCM-41 materials with different loadings of NiO were prepared combining hydrothermal method using cetyltrimethylammonia bromide as the structure-directing agent in an ammonia aqueous solution with calcination. A series of characterization of the resulting samples revealed that the materials maintained ordered mesostructure of MCM-41 after loading NiO and NiO nanoparticles were highly dispersed in the mesoporous wall and on the external surface of MCM-41. Characterization results also unveiled that $$\hbox {Ni}^{2+ }$$ prefer to enter the pores that formed by silicone gel during the hydrothermal reaction and incorporated into the pore wall and then formed NiO during the calcination process. And the TEM images indicated that smaller size NiO nanoparticles are easier to be formed on the MCM-41 materials. Catalytic results revealed that NiO should be the catalytic active centers for the oxidation of styrene and Ni-based materials showed the efficient catalytic property. Synopsis Owing to high dispersion of nickel oxide on the MCM-41 support and synergistic effect between NiO nanoparticles and the support, 6Ni-MCM-41 gave higher conversion and selectivity compared to pure NiO nanoparticles.

Three-dimensional bicontinuous open (3DBO) nanoporosity has been recognized as an important nanoarchitecture for catalysis, sensing, and energy storage. Dealloying, i.e., selectively removing a component from an alloy, is an efficient way to fabricate nanoporous materials. However, current electrochemical and liquid-metal dealloying methods can only be applied to a limited number of alloys and usually require an etching process with chemical waste. Here, we report a green and universal approach, vapor-phase dealloying, to fabricate nanoporous materials by utilizing the vapor pressure difference between constituent elements in an alloy to selectively remove a component with a high partial vapor pressure for 3DBO nanoporosity. We demonstrate that extensive elements, regardless of chemical activity, can be fabricated as nanoporous materials with tunable pore sizes. Importantly, the evaporated components can be fully recovered. This environmentally friendly dealloying method paves a way to fabricate 3DBO nanoporous materials for a wide range of structural and functional applications., Conventional dealloying methods to produce bicontinuous open nanoporous structures for catalysis are limited to very few alloys and produce chemical waste. Here, the authors develop a green process, vapor-phase dealloying, to selectively remove high partial vapor pressure components and create nanoporosity in a wide range of alloys.

Three different internal mixing methods (Core–Shell, Maxwell-Garnett, and Bruggeman) and one external mixing method are used to study the impact of mixing methods of black carbon (BC) with sulfate aerosol on their optical properties, radiative flux, and heating rate. The optical properties of a mixture of BC and sulfate aerosol particles are considered for three typical bands. The results show that mixing methods, the volume ratio of BC to sulfate, and relative humidity have a strong influence on the optical properties of mixed aerosols. Compared to internal mixing, external mixing underestimates the particle mass absorption coefficient by 20–70% and the particle mass scattering coefficient by up to 50%, whereas it overestimates the particle single scattering albedo by 20–50% in most cases. However, the asymmetry parameter is strongly sensitive to the equivalent particle radius, but is only weakly sensitive to the different mixing methods. Of the internal methods, there is less than 2% difference in all optical properties between the Maxwell-Garnett and Bruggeman methods in all bands; however, the differences between the Core–Shell and Maxwell-Garnett/Bruggeman methods are usually larger than 15% in the ultraviolet and visible bands. A sensitivity test is conducted with the Beijing Climate Center Radiation transfer model (BCC-RAD) using a simulated BC concentration that is typical of east-central China and a sulfate volume ratio of 75%. The results show that the internal mixing methods could reduce the radiative flux more effectively because they produce a higher absorption. The annual mean instantaneous radiative force due to BC–sulfate aerosol is about –3.18 W/m 2 for the external method and –6.91 W/m 2 for the internal methods at the surface, and –3.03/–1.56/–1.85 W/m 2 for the external/Core–Shell/(Maxwell-Garnett/Bruggeman) methods, respectively, at the tropopause.

In recent years, increasing attention has been devoted to X-ray phase contrast imaging, since it can provide high-contrast images by using phase variations. Among the different existing techniques, Zernike phase contrast microscopy is one of the most popular phase-sensitive techniques for investigating the fine structure of the sample at high spatial resolution. In X-ray Zernike phase contrast microscopy, the image contrast is indeed a mixture of absorption and phase contrast. Therefore, this technique just provides qualitative information on the object, which makes the interpretation of the image difficult. In this contribution, an approach is proposed for quantitative phase retrieval in X-ray Zernike phase contrast microscopy. By shifting the phase of the direct light by π/2 and 3π/2, two images of the same object are measured successively. The phase information of the object can then be quantitatively retrieved by a proper combination of the measured images. Numerical experiments were carried out and the results confirmed the feasibility of the proposed method. It is expected that the proposed method will find widespread applications in biology, materials science and so on.

3D dealloyed nanoporous metals have emerged as a new class of catalysts for various chemical and electrochemical reactions. Similar to other heterogeneous catalysts, the surface atomic structure of the nanoporous metal catalysts plays a crucial role in catalytic activity and selectivity. Through surfactant-assisted bottom-up synthesis, the surface-structure modification has been successfully realized in low-dimensional particulate catalysts. However, the surface modification by top-down dealloying has not been well explored for nanoporous metal catalysts. Here, a surfactant-free approach to tailor the surface structure of nanoporous gold by surface relaxation via electrochemical redox cycling is reported. By controlling the scan rates, nanoporous gold with abundant {111} facets or {100} facets can be designed and fabricated with dramatically improved electrocatalysis toward the ethanol oxidation reaction.

X-ray phase contrast imaging using grating interferometry has shown increased contrast over conventional absorption imaging, and therefore the great potential of dose reduction. The extent of the dose reduction depends on the geometry of grating interferometry, the photon energy, the properties of the sample under investigation and the utilized detector. These factors also determine the capability of grating interferometry to distinguish between different tissues with a specified statistical certainty in a single raw image. In this contribution, the required photon number for imaging and the resulting surface absorbed dose are determined in X-ray grating interferometry, using a two-component imaging object model. The presented results confirm that compared to conventional radiography, phase contrast imaging using grating interferometry indeed has the potential of dose reduction. And the extent of dose reduction is strongly dependent on the imaging conditions. Those results provide a theoretical framework for dose estimation under given imaging conditions before experimental trials, and general guidelines for optimization of grating interferometry for those dose-sensitive applications. (C) 2014 Elsevier B.V. All rights reserved.

It is one of the ultimate goals in cell biology to understand the complex spatio-temporal interplay of biomolecules in the cellular context. To this end, there have been great efforts on the development of various probes to detect and localize specific biomolecules in cells with a variety of microscopic imaging techniques. In this Research News, we first summarize several types of microscopy for visualizing specific biomolecular targets. Then we focus on recent advances in the design of X-ray sensitive nanoprobes for applications in synchrotron-based cellular imaging. With the availability of advanced synchrotron techniques, there has been rapid progress toward high-resolution and multi-color X-ray imaging in cells with various types of functional nanoprobes.

CeO x -induced amorphization of CoPt nanoparticles (NPs) is achieved by a facile co-reduction method using sodium borohydride (NaBH 4 ) as the reducing agent at room temperature (298 K) under ambient atmosphere. The investigation results indicate that CeO x plays a critical role in transferring the crystalline CoPt nanoalloy into the amorphous one. To our surprise, the resultant Co 0.65 Pt 0.30 (CeO x ) 0.05 NPs exhibit high catalytic kinetic performance with 72.1% hydrogen (H 2 ) selectivity for the H 2 generation from hydrous hydrazine (N 2 H 4 ) within only a few minute at 298 K. Although complete conversion is not achieved, but the initial turnover frequency value of 194.8 h −1 for the present amorphous catalyst is much higher than that of crystalline one. Moreover, such a highly rapid catalyst may greatly encourage the practical application of hydrous N 2 H 4 as a hydrogen storage material.

One of the main benefits of a fractal plate is the formation of a sequence of subsidiary foci when used as a condenser. In order to further demonstrate the reliable use of a fractal zone plate in transmission X-ray microscopy, we studied how a condenser fractal zone plate produces the focal spot in a transmission X-ray microscope layout. We present and discuss the comparison in the X-ray region with a normal condenser zone plate and a numerical simulation that points out that the efficiency of the condenser depends on the structure and the material of the zone plate, and on the energy. This analysis paves a way for foreseen optical applications of modified zone plates in real microscope layouts.

Enamel cannot heal by itself if damaged. Hydroxyapatite (HAP) is main component of human enamel. Formation of enamel-like materials for healing enamel defects remains a challenge. In this paper, we successfully isolated the abalone water-soluble matrix (AWSM) with 1.53wt% the abalone water-soluble protein (AWSPro) and 2.04wt% the abalone water-soluble polysaccharide (AWSPs) from abandoned abalone shell, and self-healing biomineralization of tooth defects was successfully achieved in vitro. Based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), hot field emission scanning electron microscopy (HFESEM) and energy dispersive spectrometer (EDS) analysis, the results showed that the AWSM can efficiently induce remineralization of HAP. The enamel-like HAP was successfully achieved onto etched enamel's surface due to the presence of the AWSM. Moreover, the remineralized effect of eroded enamel was growing with the increase of the AWSM. This study provides a solution to the resource waste and environmental pollution caused by abandoned abalone shell, and we provides a new method for self-healing remineralization of enamel defects by AWSM and develops a novel dental material for potential clinical dentistry application.

A full-field transmission X-ray microscope (TXM) operating continuously from 5 keV to 12 keV with fluorescence mapping capability has been designed and constructed at the Beijing Synchrotron Radiation Facility, a first-generation synchrotron radiation facility operating at 2.5 GeV. Spatial resolution better than 30 nm has been demonstrated using a Siemens star pattern in both absorption mode and Zernike phase-contrast mode. A scanning-probe mode fluorescence mapping capability integrated with the TXM has been shown to provide 50 p. p. m. sensitivity for trace elements with a spatial resolution (limited by probing beam spot size) of 20 mm. The optics design, testing of spatial resolution and fluorescence sensitivity are presented here, including performance measurement results.

X-ray microscopy based on synchrotron radiation has become a fundamental tool in biology and life sciences to visualize the morphology of a specimen. These studies have particular requirements in terms of radiation damage and the image exposure time, which directly determines the total acquisition speed. To monitor and improve these key parameters, we present a novel X-ray microscopy method using a high-resolution zone plate as the objective and the matching condenser. Numerical simulations based on the scalar wave field theory validate the feasibility of the method and also indicate the performance of X-ray microscopy is optimized most with sub-10-nm-resolution zone plates. The proposed method is compatible with conventional X-ray microscopy techniques, such as computed tomography, and will find wide applications in time-resolved and/or dose-sensitive studies such as living cell imaging.

This paper investigates a facile and one-step synthesis of trimetallic magnetic Cu@FeNi core–shell nanoparticles, which are composed of crystalline Cu cores and amorphous FeNi shells, at room temperature under ambient atmosphere within 2 min. It is found that among the Cu@FeNi system, Cu 0.4 @Fe 0.1 Ni 0.5 shows the best synergistic performance for catalyzing the hydrolytic dehydrogenation of ammonia borane with the activation energy of 32.9 kJ/mol, being lower than most of the reported data, and the catalytic activity of Cu 0.4 @Fe 0.1 Ni 0.5 is much better than its monometallic, bimetallic and trimetallic counterparts whether in states of pure metals, alloys or physical mixtures. Further, the present catalyst has a good recycle stability with an easy magnetic separation method.

In this contribution we discuss the possibility of designing a modified transmission X-ray microscope by using fractal zone plates (Fzps) as diffractive optical elements. In the modified transmission X-ray microscope optical layout, we first introduced a fractal zone plate as the microscope objective. Indeed, a fractal zone plate cannot only be used as an image-forming component but also as a condenser element to achieve an extended depth of field. Numerical analysis reveals that fractal zone plates and conventional Fresnel zone plates have similar imaging capabilities under different coherent illumination. Using a fractal zone plate as a condenser we also simulated axial irradiance. Results confirm that fractal zone plates can improve focusing capability with an extended depth of field. Although preliminary, these simulations clearly reveal that fractal zone plates, when available, will be of great help in microscope layouts, in particular for foreseen high-resolution applications in the "water window" as strongly required in biological research.

Open-celled aluminum foams with different pore sizes were fabricated. A plasma electrolytic oxidation (PEO) treatment was applied on the aluminum foams to create a layer of ceramic coating. The sound absorption coefficients of the foams were measured by an impedance tube and they were calculated by a transfer function method. The experimental results show that the sound absorption coefficient of the foam increases gradually with the decrease of pore size. Additionally, when the porosity of the foam increases, the sound absorption coefficient also increases. The PEO coating surface is rough and porous, which is beneficial for improvement in sound absorption. After PEO treatment, the maximum sound absorption of the foam is improved to some extent.

Dual-energy X-ray absorptiometry (DEXA) has been widely applied to measure bone mineral density (BMD) and soft-tissue composition of human body. However, the use of DEXA is greatly limited for low-Z materials such as soft tissues due to their weak absorption. While X-ray phase-contrast imaging (XPCI) shows significantly improved contrast in comparison with the conventional standard absorption-based X-ray imaging for soft tissues. In this paper, we propose a novel X-ray phase-contrast method to measure the area density of low-Z materials, including a single-energy method and a dual-energy method. The single-energy method is for the area density calculation of one low-Z material, while the dual-energy method is aiming to calculate the area densities of two low-Z materials simultaneously. Comparing the experimental and simulation results with the theoretic ones, the new method proves to have the potential to replace DEXA in area density measurement. The new method sets the prerequisites for future precise and low-dose area density calculation method of low-Z materials., 7 pages, 5 figures

For the first time, the three-dimensional (3D) ultrastructure of an intact rice pollen cell has been obtained using a full-field transmission hard X-ray microscope operated in Zernike phase contrast mode. After reconstruction and segmentation from a series of projection images, complete 3D structural information of a 35 µm rice pollen grain is presented at a resolution of ∼100 nm. The reconstruction allows a clear differentiation of various subcellular structures within the rice pollen grain, including aperture, lipid body, mitochondrion, nucleus and vacuole. Furthermore, quantitative information was obtained about the distribution of cytoplasmic organelles and the volume percentage of each kind of organelle. These results demonstrate that transmission X-ray microscopy can be quite powerful for non-destructive investigation of 3D structures of whole eukaryotic cells.

Several spiral groove gas film face seals (SGFS) with different layouts are compared quantitatively to analyze their merits and faults and application behaviors. In addition, a parametric study on downstream mode SGFS is conducted to determine its optimal parameters under certain working conditions. In the computation of gas film pressure on the face, finite element method (FEM) is applied to adapt to complicated geometrical boundary.

The hydroxyapatite nanorods (about 80 nm in length and 15 nm in width) with uniform size were achieved by hydrothermal method at 100 °C and pH 10 in the presence of alanine and glutamic acid. A special instillment order was used and the prepared powders were characterized for phase composition by X-ray diffraction and Fourier Transform infrared spectroscopy. The size and morphology of HAP nanoparticles were studied by Transmission electron microscopy. The characterization showed that the amino acid could induce the synthesis of hydroxyapatite nanoparticle and control HAP crystal growth when HAP crystal was formed. An instable monetite phase (CaPO 3 OH) was found in the progress of ACP transforming to HAP.

Poly(lactic co-glycolic acid) (PLGA) is widely used in diverse fields, especially in delivering biologically active proteins and drugs. For these applications, the knowledge of morphology and microstructure of PLGA micro-porous microspheres is of great importance since they strongly influence the drug delivering efficiency. In this study, micro-porous PLGA microspheres loaded by bovine serum albumin are investigated by using a full-field Zernike phase contrast transmission hard X-ray microscope. From three-dimensional reconstructions and segmentations, fundamental microstructural parameters such as size, shape, distribution and volume ratio among pores and proteins inside PLGA microspheres were obtained. These parameters are useful to understand the relationship between the internal microstructure and drug encapsulation, as well as the drug release efficiency of PLGA microspheres. The presented results demonstrate the capability of hard X-ray nano-tomography to characterize porous microspheres loaded with proteins and drugs, and also open a way to analyse, optimize and design new PLGA microspheres for specific applications.

We present a x-ray microscopy technique based on structured illumination in a microscope that characterizes the size of the subresolution-limit features. The technique is effective for characterizing fine structures substantially beyond the Rayleigh resolution of the microscope. We carried out optical experiments to demonstrate the basic principle of this new technique. Experimental results show good agreement with theoretical predictions. This technique should find a wide range of important imaging applications with a feature size down to nanometer scale, such as oil and gas reservoir rocks, advanced composites, and functional nanodevices and materials.