Low Bond Energy Research Articles

Highly selective aromatic ring hydrogenation of lignin-derived compounds over macroporous Ru/Nb2O5 with the lost acidity at room temperature

Selective aromatic ring hydrogenation is an important process for the valorization of lignin and designing the high active and selective catalyst is still a challenge. At present, it is reported that such catalysts generally have some shortcomings including strict reaction conditions, complicated catalyst preparation and low reaction efficiency. Herein, Ru/Nb2O5 catalyst with the macropore structure prepared by an incipient wetness impregnation method could effectively promote the aromatic rings hydrogenation of various lignin-derived compounds under extremely mild condition (30 °C). The resulting aliphatic compounds with the high yield provided abundant raw materials for the production of fine chemicals and biofuels. In this case, further experiments revealed that it was H2 rather than solvents provided the only hydrogen source. A relatively low bond energy of Ru0 in Ru/Nb2O5 promoted the formation of active hydrogen from H2. Due to the acid loss of Ru/Nb2O5 catalyst, the hydrodeoxygenation reaction did not occur. Moreover, the catalyst was investigated under different influence parameters in order to obtain the optimal reaction conditions (30 °C, 3 MPa H2). The application of Ru/Nb2O5 catalyst may provide a promising approach to the value-added utilization of lignin-derived fragments.

Facile preparation of persistently hydrophilic poly(vinylidene fluoride-co-trifluorochloroethylene) membrane based on in-situ substitution reaction

The predominant method to mitigate membrane fouling is based on hydrophilic modification such as additive blending and surface treatment. But the disadvantages such as prone to leaching from membrane, high cost of amphiphilic copolymer, may cause membrane damage and may decrease water flux are stumbling blocks to the further development and application of polymer membranes. Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) is attracting ncreasing attention due to its good chemical resistance, excellent alkali resistance, high thermal stability and membrane forming properties. Herein, a novel and simple one-step strategy to prepare persistently hydrophilic PVDF-CTFE membrane based on in-situ substitution reaction is reported. In this method, hydrophilic polyhydroxy meglumine is immobilized in PVDF-CTFE membrane via grafting reaction with the low bond energy C–Cl bond of PVDF-CTFE during casting solution preparation. The results show that meglumine is successfully immobilized in membrane surface and matrix, thus obviously improving the membrane hydrophilicity. Moreover, the water flux is increased (up to 185%) and the mechanical strength and pore size are maintained simultaneously. The optimum membrane exhibits excellent fouling resistance (almost 100% flux recovery ratio). The simple one-step method not only improves the hydrophilicity, but also avoids the obvious negative effect normally accompanied by conventional methods on the mechanical strength and permeability.

Structure-Sensitive Electrocatalytic Reduction of CO2 to Methanol over Carbon-Supported Intermetallic PtZn Nano-Alloys.

The electrochemical reduction of CO2 (CO2RR) to produce valuable synthetic fuel like CH3OH not only mitigates the accumulated greenhouse gas from the environment but is also a promising direction toward attenuating our continuous reliance on fossil fuels. However, CO2RR to yield CH3OH suffers because of large overpotential, competitive H2 evolution reaction (HER), and poor product selectivity. In this regard, intermetallic alloy catalysts open up a wide possibility of fine-tuning the electronic property and attain appropriate structures that facilitate selective CO2RR. Here, we report for the first time the CO2RR over carbon-supported PtZn nano-alloys and probed the crucial role of structures and interfaces as active sites. PtZn/C, Pt3Zn/C, and PtxZn/C (1 < x < 3) synthesized from the metal-organic framework material were characterized structurally and morphologically. The catalysts demonstrated structure dependency toward CH3OH selectivity, as the mixed-phase PtxZn/C outperformed the phase-pure PtZn/C and Pt3Zn/C. The structure-dependent reaction mechanism and the kinetics were elucidated over the synthesized catalysts with the help of detail experiments and associated density functional theory calculations. Results showed that in spite of low electrochemically active surface area, PtxZn could not only have facilitated the single electron transfer to adsorbed CO2 but also showed better binding of the intermediate CO2•- over its surface. Moreover, the lower bond energy between the mixed-phase surface and -OCH3 compared to the phase-pure catalysts has enabled higher CH3OH selectivity over PtxZn. This work opens a wide possibility of studying the role of interfaces between phase-pure nano-alloys toward CO2RR.

Polyacrylamide stabilized alkenyl succinic anhydride emulsion as sizing agent for various cellulosic pulps and fillers

Cellulosic fiber is hydrophilic in nature and making it hydrophobic represents a process called sizing in papermaking. Alkenyl succinic anhydride (ASA) sizing is dominating over other sizing processes due to its high reactivity and economy. The shelf life of conventionally used cationic starch (CS) stabilized ASA emulsion is 20−25 min. In our previous study, the ASA emulsion was found to be stable up to 4 h using anionic polyacrylamide (APAM) as stabilizer. Present communication was aimed to utilize, the APAM stabilized ASA emulsion with most commonly utilized cellulosic pulps (mixed hardwood, bagasse and recycled) and fillers to assist its commercial utilization in papermaking. APAM stabilized ASA emulsion facilitated back water utilization with improved sizing degree unlike CS based ASA emulsion. Lower amount of ASA sizing was required in bagasse pulp compared to other pulps which might be attributed to low crystallinity ratios and hydrogen bond energy.

“One for two” strategy to prepare MOF-derived NiCo2S4 nanorods grown on carbon cloth for high-performance asymmetric supercapacitors and efficient oxygen evolution reaction

Metal-organic frameworks (MOFs) have recently emerged as promising hierarchical structured porous materials for high-performance energy storage and conversion devices due to their unique tunable structure and excellent porosity. Herein, we reported a “one for two” strategy to prepare NiCo2S4 nanorods directly grown on carbon cloth (NiCo2S4@CC) via a simply modified MOFs-derived approach for high-performance asymmetric supercapacitors and efficient oxygen evolution reaction (OER). As an electrode for asymmetric supercapacitors, the NiCo2S4@CC electrode showed excellent electrochemical performance with high specific capacitance and good rate capability. The asymmetric supercapacitor using NiCo2S4@CC as a cathode electrode and N-doped porous carbon nanosheets grown on the CC (NC@CC) as an anode electrode achieved a superior energy density and power density and a long cycle life. Furthermore, the NiCo2S4@CC exhibited a notable electrocatalytic activity as an electrocatalyst for OER. The remarkable electrochemical performance of as-prepared NiCo2S4@CC could be mainly attributed to its hierarchical structure, sufficient active sites and low metal-anion bond energy after sulfuration reaction. This work could provide an unprecedented opportunity to fabricate functional materials under rational design for various applications.

Structure of MF-AlF3-ZrO2 (M = K, Na, Li) ionic melts

Quantum-mechanical calculations by the DFT method and a physical experiment were performed to clarify the type of complexes and their role when using ZrO2 as a source of zirconium to producing Al-Zr master alloys. The binding energy of complex anions formed from the components Zr-F, Al-O-F and Zr-O-F, whose formation is associated with the dissolution of ZrO2 and Al2O3 oxides in fluoride melts MF-AlF3 (M = K, Na, Li) was calculated using the program Siesta. The influence of the elemental composition of anions and cation from the second coordination sphere on the binding energy of complex anions is determined. It is shown that filling of the second coordination sphere with Na+ and K+ cations shifts the stability from the [Zr2O2F6]2− to [Zr2O2F7]3− complex compound. Replacement of the cation in the second coordination sphere in the row from K to Li leads to lower bond energy in all considered anions. Replacement of aluminium in [ZrFx]z- and [Zr2O2Fx]z- complex groups leads to increasing of ion's size.The available experimental data on the interaction of ZrO2 with MF-AlF3 (M = K, Na, Li) fluoride melts are presented and some new results have been obtained via Raman spectroscopy and XRD.Based on the comparative analysis of calculations, available and new experimental data concerning interactions in MF-AlF3-ZrO2 (M = K, Na, Li) systems it is shown that ZrO2 dissolution in the MF-AlF3 melts significantly depends on the radius of the cation of the second coordination sphere. Thus, the ZrO2 dissolution in the KF-AlF3 melt takes place with the formation of the K2ZrF6 and Al2O3 compounds, white in the NaF-AlF3-ZrO2 system zirconium complexes and Al2O3 appears.

Research of the thermal decomposition mechanism and pyrolysis pathways from macromonomer to small molecule of waste printed circuit board

Pyrolysis is an important pre-treatment technology for pyrometallurgy, which could reduce pollution and recover materials from waste printed circuit boards (WPCBs). However, present studies on mechanism of pyrolysis were insufficient, which results in the unclear of controlling reaction rate and inhibiting side reaction. To further develop pyrolysis technology, the in-depth research on the pyrolysis mechanism is necessary. In this study, we investigated the thermal decomposition process and pyrolysis pathways from macromonomers to products of WPCBs. The results showed that HBr was produced at the initial stage of pyrolysis. Then, the resin body depolymerized into macromonomers, followed by random rupture and free radical reactions to form pyrolysis products. Besides, possible mechanism for bisphenol A thermal decomposing was analyzed by bond energy. The results suggested that methyl groups in bisphenol A would be preferentially removed because of low bond energy. The six possible pathways may occur simultaneously when energy sufficient. Moreover, the mechanism function was determined by Škvára-Šesták method as: G(α)=-ln 1-α2, which indicated pyrolysis reaction agreed with the model of random nucleation followed by random growth. This study provided the theoretical basis for pollution control, process optimization and reactor design of WPCBs pyrolysis.

Organosulfides: An Emerging Class of Cathode Materials for Rechargeable Lithium Batteries.

Lithium-ion batteries have received significant attention over the last decades due to the wide application of portable electronics and increasing deployment of electric vehicles. In order to further increase the energy density of batteries and overcome the capacity limitations (<250 mAh g-1) of inorganic cathode materials, it is imperative to explore new cathode materials for rechargeable lithium batteries. Organic compounds including organic carbonyl, radicals, and organosulfides are promising as they have advantages of high capacities, abundant resources, and tunable structures. In the 1980s, a few organosulfides, in particular organodisulfides, as cathode materials were studied to a certain extent in rechargeable lithium batteries. However, they showed low capacities and poor cycling performance, which made them unappealing then in comparison to transition metal oxide cathode materials. As a result, organosulfides have not been extensively studied like other cathode materials including organic carbonyls and radicals. In recent years, organosulfides with long sulfur chains (e.g., trisulfide, tetrasulfide, pentasulfide, etc.) in the structures have been receiving more attention in conjunction with the development of lithium-sulfur batteries. As a major class of sulfur derivatives, they have versatile structures and unique properties in comparison with elemental sulfur. In this Account, we first generalize the working principles of organosulfides in lithium batteries. We then discuss organosulfide molecules, which have precise lithiation sites and tunable capacities. The organic functional groups can provide additional benefits, such as discharge voltage and energy efficiency enhancement by phenyl groups and cycling stability improvement by N-heterocycles. Furthermore, replacing sulfur by selenium in these compounds can improve their electrochemical properties due to the high electronic conductivity and low bond energy associated with selenium. We list organosulfide polymers consisting of phenyl rings, N-heterocycles, or aliphatic segments. Organosulfides as electrolyte additives or components for forming a solid-electrolyte interphase layer on lithium metal anode are also presented. Carbon materials such as carbon nanotubes and reduced graphene oxide can enhance the battery performance of organosulfide cathodes. We discuss the synthesis methods for polysulfide molecules and polymers. Finally, we show the advantages of organosulfides over sulfur as cathode materials in lithium batteries. This Account provides a summary of recent development, in-depth analysis of structure-performance relationship, and guidance for future development of organosulfides as promising cathode materials for next generation rechargeable lithium batteries.

Effects of supercritical CO2 on micropores in bituminous and anthracite coal

The effects of supercritical CO2 (ScCO2) on coal micropores play a critical role in determining the CO2 capacity of coalbeds. To investigate the effects of ScCO2 on micropores in coals of different ranks under a range of temperature and pressure conditions, CO2 sequestration processes are replicated using a ScCO2 geochemical reactor. Four samples of coal of different ranks are exposed to ScCO2 and water for 240 h at 62.5 °C and 15 MPa, and CO2 adsorption tests, Fourier transform infrared spectroscopy, and X-ray diffraction are performed to determine the volume and pore size distribution of the micropores, the types and contents of the organic groups, and the aromatic crystallite structures of the coal samples before and after the ScCO2-H2O treatment. The influence of the chemical structure and the organic groups of the coal on the coal micropores is then studied. Micropores with widths <0.46 nm are mainly associated with the inter-layer spacing of the aromatic layers. Swelling caused by ScCO2 detaches heterocycles and non-condensed polynuclear aromatics of high-volatile bituminous coal, resulting in slight increases in the volume of micropores with widths <0.46 nm. The falling off of cross-links with low bond energies caused by swelling and the formation of CArCAr cross-links between the aromatic layers caused by polyaddition reactions together cause a decrease in the volume of micropores with widths <0.46 nm in semi-anthracite and anthracite coal. Micropores with widths >0.46 nm are pores in the macromolecular structure of coal and are known as intermolecular pores, and their volumes are determined by the directional arrangement of aromatic crystallites and the aliphatic hydrocarbon chain length. The broken bonds caused by ScCO2 in high-volatile bituminous coal form new aliphatic or aromatic compounds via addition and polyaddition reactions. These processes increase the directional arrangement of aromatic crystallites, resulting in a decrease in the volume of micropores with widths >0.46 nm. As the coal rank increases, the aliphatic hydrocarbon chain length gives priority to the macromolecular structure of coal after the ScCO2 treatment, resulting in an increase in the volume of micropores with widths >0.46 nm in semi-anthracite and anthracite coal.

Density Gradient Strategy for Preparation of Broken In2O3 Microtubes with Remarkably Selective Detection of Triethylamine Vapor.

Tubule-like structured metal oxides, combined with macroscale pores onto their surfaces, can fast facilitate gas-accessible diffusion into the sensing channels, thus leading a promoted utilization ratio of sensing layers. However, it generally remains a challenge for developing a reliable approach to prepare them. Herein, this contribution describes a density gradient strategy for obtaining broken In2O3 microtubes from the In2O3 products prepared using a chemical conversion method. These In2O3 microtubes hold a diameter about 1.5 μm with many broken regions and massive ultrafine nanopores onto their surfaces. When employed as a sensing element for detection of triethylamine (TEA) vapor, these broken In2O3 microtubes exhibited a significant response toward TEA at 1-100 ppm and the lowest detected concentration can reach 0.1 ppm. In addition, an excellent selectivity of the sensor to TEA was also displayed, though upon exposure of other interfering vapors, including ammonia, methanol, ethanol, isopropanol, acetone, toluene, and hydrogen. Such promoted sensing performances toward TEA were ascribed to the broken configuration (superior gas permeability and high utilization ratio), one-dimensional configuration with less agglomerations, and low bond energy for C-N in a TEA molecule.

Temporary Bonding Technologies for Thin Wafer Handling

Thin glass substrates offer low dielectric constant and high temperature process capability for faster and thinner packages but handling is challenging due to lack of mechanical stiffness. Temporary bonding of thin wafers to stiffer carrier substrates offers a solution and has been an active area of research and development in recent years. Polymeric and tape wafer bonding solutions are available but usually for low temperature processes. In Corning, we have developed an array of surface treatment/coating technologies that offer high temperature capability (as high as 700°C). The common theme of all these technologies entails surface treatment or coating of a carrier substrate to achieve strong non-covalent bonding with the thin wafer. The desired attributes are: (a) high enough bond energy at room temperature to withstand vacuum, thermal, and wet processing steps, (b) low enough bond energy after the thermal processing steps rendering the pair mechanically separable, (c) spontaneous bonding via self-propagating bond wave, and (d) minimal outgassing or bubble formation between carrier and thin wafer due to degradation of bonding material. The technologies range from vacuum based sub-monolayer surface functionalization to vacuum based organometallic coating to high throughput solution processed ultra-thin molecular coatings. In this talk we will first describe the theoretical underpinnings of various surface and chemical forces that control the bond energy between the carrier and the thin wafer, models to predict the bond energy as function of surface chemistry and surface energy parameters, influence of surface chemistry on various process attributes such as bond wave propagation and outgassing during thermal treatment. We will also briefly review various processes developed and their relative strengths and applicability.

Study on the effects of carrier and modifier on mercury adsorption behavior over halides modified sorbents using temperature programmed desorption method

Halides modified sorbents injection equipped with dust removal units is considered as the most promising technology for elemental mercury (Hg0) removal from coal-fired flue gas. However, Hg0 adsorption behavior over different halides modified sorbents remains controversial. In this study, the effects of carriers (activated carbon and neutral Al2O3) and modifiers (NaCl, NaBr, CuCl2, and CuBr2) on the behavior of Hg0 adsorption over modified sorbents were investigated using temperature programmed desorption (TPD) method. Both mercury adsorption experiments and TPD experiments were conducted in the bench-scale fixed bed. The results indicated that CuBr2-modified activated carbon (AC) showed the best mercury removal performance due to the lower bond energy of CuBr2. The decomposition temperature of mercury compounds generated on AC was different from that on neutral Al2O3. Further analysis indicated that the modifiers with lower bond energy could release halogens during modification. The released halogens could react with AC to form active CCl or CBr group. Moreover, the lower bond energy of modifiers made it easier for halogens to release. But Al2O3 carrier could not react with modifiers to form active group during modification. The Hg0 adsorption process over modified Al2O3 could be explained by Langmuir-Hinshelwood mechanism.

Rubber pyrolysis: Kinetic modeling and vulcanization effects

Kinetic studies and the effect of the vulcanization process on the pyrolysis of natural rubber (NR), butadiene rubber (BR) and styrene-butadiene rubber (SBR) were investigated in this work. A comprehensive kinetic study using a model-based method, a model-free method and the distribution activation energy model (DAEM) was applied and a comparison between the different models was drawn. The DAEM showed a better fitting of the experimental results than the model-based method. The activation energy distribution of the DAEM verified by the model-free method indicated that the main decomposition of rubbers followed a chain reaction mechanism. Pyrolysis of raw rubbers and their corresponding vulcanized rubbers were conducted in a fixed-bed reactor. The sulfur content and product yields were quantified. Pyrolysis oils were characterized and compared. The oil yields reached a maximum at 430 °C for NR (90.82%), 470 °C for both BR (90.61%) and SBR (92.80%). Pyrolytic oils of raw rubbers were mainly composed of their corresponding monomer or dimer, trimer compounds. However, the results of vulcanized rubbers pyrolysis were significantly different. Sulfur in the vulcanized rubbers was released at low temperatures due to the lower bond energy. Higher temperatures led to the conversion of sulfur-containing oils to gaseous compounds. Vulcanization promoted the decomposition of rubbers at low temperatures but had an insignificant influence on pyrolysis products distribution at high temperature. Pyrolysis oils of vulcanized rubbers were more complex, constituting various aromatic hydrocarbons and thiophenes.

Wide-range infrared transparency of hydrated magnesium-carbon films with high mobility for enhanced conductivity

The hydrated magnesium-carbon films fabricated in this study demonstrated that grain growth and crystallinity modification by substrate temperature treatment crystallization produce films with fewer internal imperfections. This results in high mobility of the solution-deposited hydrated magnesium-carbon electrical conductance, with a corresponding dramatic harmonious transmittance in the infrared range. An investigation of the hydrated magnesium-carbon films shows that the temperature treatment dramatically improves the electron mobility and decreases the carrier concentration, which in turn simultaneously increases the conductivity and transparency. The hydrated magnesium-carbon films exhibit a mobility of up to 85.2 cm2/(V·s) and the resistivity declines rapidly to 1.72 × 10−2 Ω·cm. The transmittance of the visible spectrum increased to 90%. Although the conductivity of hydrated magnesium-carbon films is not prominent comparing to the conventional and widely-used n-type TCO materials, e.g. ITO, the films also showed excellent optical properties, which can be attributed to their low bond energy, with the infrared transmittance of the films being greater than 70% for a plasma wavelength of approximately 10 μm.

Simultaneous generation of oxygen vacancies on ultrathin BiOBr nanosheets during visible-light-driven CO2 photoreduction evoked superior activity and long-term stability

Under the tremendous pressure of imminent energy crisis and anthropogenic climate change, photocatalytic conversion of abandoned CO2 into energy-rich hydrocarbon fuels is highly desirable. However, this solar-to-fuel conversion is unavoidably suppressed by the fast recombination of electron-hole pairs and lack of stability of photocatalysts. To overcome this, we have developed ultrathin BiOBr nanosheets (BOB-NS) with primarily exposed {001} facets. The {001} facets of BOB-NS are comprised of high density O atoms, which are linked to the neighbouring Bi atoms via weak BiO bonds with long bond length and low bond energy. After visible-light-driven CO2 photoreduction over BOB-NS, we found that the BiO bonds were broken and oxygen vacancy (OV) defects formed on the sample surface. The presence of these OVs was proven to be beneficial for photoactivities as photoinduced electrons were effectively trapped at the OV sites and recombination of charge carriers were inhibited. Generally, the free O atoms from dissociation of CO2 would reoxidize the sample surface, thereby deteriorating the performance of photocatalysts. In contrast, we demonstrated in this study that the OV sites on BOB-NS could be simultaneously regenerated and refreshed as the reactions proceeded, leading to a sustainable activity and long-term stability for CO2 photoreduction.

Hydrated magnesium-carbon films with conductivity and wide-range visible-to-far-infrared transparency

The hydrated magnesium-carbon films fabricated in this study are the novel-innovative non-oxide-type transparent electronic material. The films, which have a structure similar to that of magnesium hydroxide, were produced by making Mgx-Cy films deposited by magnetron co-sputtering react with water vapor. As the extrinsic defect of hydration magnesium-carbon films, C atoms provided redundant electrons, resulting in a conductivity of approximately 3.31 × 10−2 Ω·cm. Although the conductivity of hydrated magnesium-carbon films is not prominent comparing to the conventional and widely-used n-type TCO materials, e.g. ITO, the films also showed excellent optical properties, which can be attributed to their low bond energy, with the infrared transmittance of the films being greater than 72% for a plasma wavelength of approximately 10 μm. By varying the atomic C content of the films, a visible-region transmittance greater than 80% could be realized. The optical bandgap of the films was approximately 4.04–6.87 eV and was blue-shifted because of the Moss-Burstein effect.

Synthesis and characterization of diselenide linked poly(ethylene glycol) nanogel as multi-responsive drug carrier

Diselenide containing polymeric-nanoparticles considered as stimuli-responsive due to their low bond energy of SeSe linkage with stimuli-sensitive properties SeSe bond. Recently, diselenide bond containing amphiphilic block copolymers based nanoparticles become emerging materials as drug carrier. In this work, biocompatible, redox and gamma (γ)-ray sensitive diselenide-linked polymeric-nanogel (PEGSeSe)n was developed from alpha, omega-Bis-Bromo poly(ethylene glycol) (Br-PEG-Br) for anticancer drug carrier. A stimuli-responsive anti-cancer drug, doxorubicin (Dox) releasing of the nanogel was evaluated using an ultraviolet-visible spectrophotometer. The drug loading efficiency of the nanogel was found to be 32.7%. Redox-stimuli-drug release study was conducted in the presence of 0.1% (w/w) hydrogen peroxide (H2O2), and 1 mg/mL of glutathione (GSH) in phosphate-buffered saline (PBS) pH of 7.4 at 37 °C, as well as 5 Gy γ-ray was applied for understand their radiation responsive release of Dox. The drug release profiles indicated that fast release were observed during the initial few hours and maximum release 54% were shown after 48 h and 52.5% after 24 h in the presence of GSH and H2O2 respectively, and gradually drug release were decreased as the time increases. Interestingly, γ-ray irradiation drug release also showed that maximum of 46% the drug released within 12 h after irradiation. Based on the obtained results, it can be concluded that the synthesized nanogel could be a promising redox and radiation-sensitive nanocarrier biomaterial for high loading amount of anticancer drug and could be used for anticancer drugs delivery in redox environment and a low dose of γ-ray radiation.

Nanoindentation and Deformation of Multilayered Au/Cu Films

The mechanical properties of single and multilayer gold and copper films are studied using molecular dynamics and deformation, the slip effect, the load bearing capacity and energy differences are also discussed. Results showed that as the indentation depth increases in a multilayer model, the grain boundaries of the first layer are broken and the atoms diffuse into the lower layer, thereby leading the change of the amount of slip. Single-crystal Au and Cu models generate more slippage due to lower bond energy between atoms. The larger the amount of atomic flow under indentation is, the larger the amount of slip is. As the depth of the indentation increases, the area influenced by indentation increases and the maximum load bearing capacity and potential energy also increase. Plastic deformation from indentation at high speed does not result from dislocation slip, but from a larger force that destroys the bonds between atoms. At higher temperature, the amount of slip around the indenter is less obvious and the structure is gradually softened. Moreover, the same depth of indentation can be achieved with a smaller load force for higher temperature.

4-Chloro-α-cyanocinnamic acid is an efficient soft matrix for cyanocobalamin detection in foodstuffs by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS).

4-Chloro-α-cyanocinnamic acid (ClCCA) is a very useful matrix able to give the protonated adduct [M+H](+) of intact cyanocobalamin (CNCbl) as the base peak (m/z 1355.58) in matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). The only fragment observed is [M-CN + H](+•) formed through the facile (•) CN neutral loss reflecting the fairly low Co-C bond energy. All other investigated proton transfer matrices, including α-cyano-4-hydroxycinnamic acid, para-nitroaniline and 2,5-dihydroxybenzoic acid, give rise to a complete decyanation of CNCbl with concomitant formation of [M-CN + H](+•) , [M-CN + Na](+•) and [M-CN + K](+•) adducts at m/z 1329.57, 1351.55 and 1367.51, respectively. Depending on the matrix used, a variable degree of fragmentation involving the α-side axial ligand was observed. A plausible explanation of the specific behaviour of 4-chloro-α-cyanocinnamic acid as a soft matrix is discussed. Tandem mass spectra of both [M + H](+) and [M-CN + H](+•) ions were obtained and product ions successfully assigned. The possibility of detecting the protonated adduct of intact CNCbl was exploited in foodstuff samples such as cow milk and hen egg yolk by MALDI tandem MS upon sample extraction. We believe that our data provide strong basis for the application of MALDI tandem MS in the qualitative analysis of natural CNCbl, including fish, liver and meat samples. Copyright © 2016 John Wiley & Sons, Ltd.

Structural stability and magnetic properties of WFeH phases

First principles calculation reveals that hydrogen at the tetrahedral site of B2 W50Fe50 is energetically unstable and will relax to the octahedral site, which is quite different from the stable tetrahedral site of BCC W and Fe. It is also shown that the WH bond is generally stronger with lower bond energy than the FeH bond, and that zero-point energy of hydrogen has a negligible effect on structural stability of WH, FeH, and W50Fe50H phases. Moreover, both W and H atoms have important effects to reduce magnetic moments of W50Fe50 and Fe, while their intrinsic mechanisms are quite different, i.e., the addition of W induces the decrease of the bond number of FeFe, and the addition of H brings about the decrease of FeFe bond length. The calculated results are in good agreements with experimental observations in the literature, and are discussed in terms of electronic structures and bond characteristics.