Alkaline water electrolysis is a sustainable way to produce green hydrogen using renewable electricity. Even though the rates of the cathodic hydrogen evolution reaction (HER) are 2-3 orders of magnitude less under alkaline conditions than under acidic conditions, the possibility of using non -precious metal catalysts makes alkaline HER appealing. We identify a novel and facile route for substantially improving HER performance via the use of commercially available NiTi shape memory alloys, which upon heating undergo a phase transformation from the monoclinic martensite to the cubic austenite structure. While the room -temperature performance is modest, austenitic NiTi outperforms Pt (which is the state-of-the-art HER electrocatalyst) in terms of current density by <= 50% at 80 degrees C. Surface ensembles presented by the austenite phase are computed with density functional theory to bind hydrogen more weakly than either metallic Ni or Ti and to have binding energies ideally suited for HER.

Proton-exchange-membrane (PEM) electrolyzers represent a promising technology for sustainable hydrogen production, owing to their efficiency and load flexibility. However, the acidic nature of PEM demands the use of platinum-group metal-electrocatalysts. Apart from the associated high capital costs, the scarcity of Ir hinders the large-scale implementation of the technology. Since low-cost replacements for Ir are not available at present, there is an urgent need to engineer catalyst-coated membranes (CCMs) with homogeneous catalyst layers at low Ir loadings. Efforts to realize this mainly rely on the development of advanced Ir nanostructures with maximized dispersion via wet chemistry routes. This study demonstrates the potential of an alternative vapor-based process, based on spark ablation and impaction, to fabricate efficient and durable Ir- and Pt-coated membranes. Our results indicate that spark-ablation CCMs can reduce the Ir demand by up to five times compared to commercial CCMs, without a compromise in activity. The durability of spark-ablation CCMs has been investigated by applying constant and dynamic load profiles for 150 h, indicating different degradation mechanisms for each case without major pitfalls. At constant load, an initial degradation in performance was observed during the first 30 h, but a stable degradation rate of 0.05 mV h−1 was sustained during the rest of the test. The present results, together with manufacturing aspects related to simplicity, costs and environmental footprint, suggest the high potential of spark ablation having practical applications in CCM manufacturing.

Sintering of nanoparticles is an important contributor to loss of activity in heterogeneous catalysts, such as those used for controlling harmful emissions from automobiles. But mechanistic details, such as the rates of atom emission or the nature of the mobile species, remain poorly understood. Herein we report a novel approach that allows direct measurement of atom emission from nanoparticles. We use model catalyst samples and a novel reactor that allows the same region of the sample to be observed after short-term heat treatments (seconds) under conditions relevant to diesel oxidation catalysts (DOCs). Monometallic Pd is very stable and does not sinter when heated in air (T <= 800 degrees C). Pt sinters readily in air, and at high temperatures (>= 800 degrees C) mobile Pt species emitted to the vapor phase cause the formation of large, faceted particles. In Pt Pd nanoparticles, Pd slows the rate of emission of atoms to the vapor phase due to the formation of an alloy. However, the role of Pd in Pt DOCs in air is quite complex: at low temperatures, Pt enhances the rate of Pd sintering (which otherwise would be stable as an oxide), while at higher temperature Pd helps to slow the rate of Pt sintering. DFT calculations show that the barrier for atom emission to the vapor phase is much greater than the barrier for emitting atoms to the support. Hence, vapor-phase transport becomes significant only at high temperatures while diffusion of adatoms on the support dominates at lower temperatures. (C) 2015 Elsevier Inc. All rights reserved.

Atomic force microscopy (AFM) force spectroscopy was used to study the single-molecule rupture events of the interaction between hyaluronan (HA) and the binding domain of its cell surface receptor CD44. AFM probes were amino terminated with 3-aminopropyl triethoxy silane (APTES) followed by covalent coupling of protein A, enabling the binding of the CD44–HA-binding domain, as part of a CD44–Fc fusion protein. HA was covalently bound to APTES-coated silicon surfaces. Single-rupture events were recorded at various loading rates revealing an energy barrier: E b = 24 ± 1 kT and characteristic distance: x β = 1.3 ± 0.1 nm for this interaction. This quantification will be of interest in applications and research involving the use of the CD44–Fc fusion protein since we observe a weaker interaction between HA and CD44–Fc than what has been reported for the entire native CD44 molecule.

4-Nitrobenzenediazonium (4-NBD) and 4-bromobenzenediazonium (4-BBD) salts were grafted electrochemically onto H-terminated, p-doped silicon (Si) surfaces. Atomic force microscopy (AFM) and ellipsometry experiments clearly showed layer thicknesses of 2-7 nm, which indicate multilayer formation. Decreasing the diazonium salt concentration and the reaction time resulted in a smaller layer thickness, but did not prevent the formation of multilayers. It was demonstrated, mainly by X-ray photoelectron spectroscopy (XPS), that the diazonium salts not only react with the H-terminated Si surface, but also with electrografted phenyl groups via azo-bond formation. These azo bonds can be electrochemically reduced at Ered = -1.5 V, leading to the corresponding amino groups. This reduction resulted in a modest decrease in layer thickness, and did not yield monolayers. This indicates that other coupling reactions, notably a biphenyl coupling, induced by electrochemically produced phenyl radicals, take place as well. In addition to the azo functionalities, the nitro functionalities in electrografted layers of 4-NBD were independently reduced to amino functionalities at a lower potential (Ered = -2.1 V). The presence of amino functionalities on fully reduced layers, both from 4-NBD- and 4-BBD-modified Si, was shown by the presence of fluorine after reaction with trifluoroacetic anhydride (TFAA). This study shows that the electrochemical reduction of azo bonds generates amino functionalities on layers produced by electrografting of aryldiazonium derivatives. In this way multifunctional layers can be formed by employing functional aryldiazonium salts, which is believed to be very practical in the fabrication of sensor platforms, including those made of multi-array silicon nanowires.

Nucleation and morphology development during the early stages of chemical vapor deposition (CVD) processes are believed to be of major importance for the overall film properties. Here, the authors have investigated the nucleation of tin oxide films, comparing different tin precursors (tin tetrachloride (TTC) and monobutyl tin trichloride (MBTC)) and focusing on the effect of methanol addition on the film morphology. Employing electron transparent silicon oxide membranes as substrates and combining transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis on the same set of samples, we describe a detailed picture of nucleation behavior and film growth during early stages of film formation. Our main conclusion is that methanol addition during deposition acts as surfactant, lowering the surface energy of the substrate and resulting in a higher nucleation grain density. Based on these results, we propose a film growth model based on surface energy to explain morphology differences in tin oxide films resulting from methanol addition. (C) 2014 Elsevier B.V. All rights reserved.

Indirect biomass gasification systems consist of two reactors: an oxidation reactor and a gasification reactor. A bed-material is used to transfer heat from the oxidation to the gasification reactor. Olivine has been widely studied as a reactive bed-material for this process. The iron in olivine can act as a catalyst for the decomposition of tars, produced during the gasification process. Moreover, iron is capable of transferring oxygen to the gasification reactor. In this study, we elucidate the role of iron in this chemical looping process. Mössbauer spectra show that during oxidation in O2/Ar at 750 °C, iron segregates out of the olivine matrix forming free iron oxide phases. These free iron phases form metallic iron upon subsequent reduction in hydrogen. Thermo gravimetric analysis (TGA) is used to quantify oxygen transport under alternating oxidizing/reducing conditions. TGA results indicate that at least 18% of all the iron, present in olivine, is capable of transferring oxygen on the time scale of minutes. X-ray photoelectron spectroscopy (XPS) combined with depth profiling provides insight in the dynamic behavior of olivine under relevant conditions. Iron enrichment at the surface is observed; oxidized olivine has an iron rich surface layer of 400 nm. The increased iron concentration is particularly pronounced at the outermost surface. Upon subsequent reduction, the iron quickly redistributes in the olivine toward the original, homogeneous distribution. These results show that oxygen transport should be taken into account when olivine is evaluated as a catalyst for indirect biomass gasification. Furthermore, both oxygen transport and catalytic properties are heavily dependent on the iron phases present in the material, which in turn depend on the gas environment.

The chemistry of atmospheric pressure chemical vapor deposition (APCVD) processes is believed to be complex, and detailed reports on reaction mechanisms are scarce. Here, the authors investigated the reaction mechanism of monobutyl tinchloride (MBTC) and water during SnO2 thin film growth using x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). XPS results indicate an acid–base hydrolysis reaction mechanism, which is tested with multilayer experiments, demonstrating self-terminating growth. In-house developed TEM wafers are used to visualize nucleation during these multilayer experiments, and results are compared with TEM results of APCVD samples. Results show almost identical nucleation behavior implying that their growth mechanism is identical. Our experiments suggest that in APCVD, when using MBTC and water, SnO2 film growth occurs via a heterolytic bond splitting of the Sn-Cl bonds without the need to invoke gas-phase radical or coordination chemistry of the MBTC precursor.

Many countries in South Europe region, like Montenegro, are suffering from the lack of energy. The increasing demand for energy is a consequence of switching to the new political system, democracy, free market, and sometimes uncontrolled development. However, only small steps are done to fulfill these requirements by implementing energy efficiencies, alternate renewable energy sources, new energy policy etc. Solar water heating (SWH) is probably the most promising, reliable and mature technology, where the price of saved electricity is less than the current price of electricity in this region. The main reason for that is in simplicity of use such energy without its transformation to the end use, and the savings in costs of energy distribution. Furthermore, the environmental impacts associated with its use, are much less harmful than in other energy sources. There is well developed methodology for estimating the attractiveness of implementation of such technology. Discount cash flow analysis is applied for calculation the price of such kind of energy. The critical factors of an economic analysis are the available quantity of solar energy in the region, the costs of solar system and its energy efficiencies, and the cost of operating conventional or backup water heating systems. These factors severely influence the final costs of energy. The analysis is conducted in accordance to current state of the prices of electrical energy in Montenegro and the current prices of solar water heating technologies. The preliminary results are very promising.

This paper describes a novel form of dynamic operation named pulsed activation method. It can be viewed as a form of periodic operation in which very fast temperature pulsing is used to induce chemical reactions directly and locally as needed. The main goal in this method is to activate catalytic reactions at will and within a time scale such that physical transport related dynamics cannot follow. A proof of principle experimental setup has been built to realize pulsed activation on heterogenous catalytic reactions. The temperature of the catalytic surface is pulsed at higher frequencies and amplitudes than have been reported before. As an example, oxidation of CO over a Pt catalyst is investigated. (C) 2012 Elsevier Ltd. All rights reserved.

The effect of water on iron-based nanoparticles under hydrogen and syngas was investigated by in situ X-ray absorption spectroscopy. The iron oxide (gamma-Fe2O3) nanoparticles, dispersed as a monolayer on flat silica surfaces, were readily converted into metallic iron in dry hydrogen at 350 degrees C and into iron carbide in dry syngas (H-2/CO 2/1 vol/vol) at 325 degrees C. However, in the presence of water, the reduction did not proceed beyond magnetite (Fe3O4) up to 350 degrees C. Wustite (Fe(II)O or FeO(1-x)) was formed at 450 degrees C in wet syngas and 550 degrees C in wet hydrogen. Once formed, the iron carbide nanoparticles proved remarkably stable against oxidation in wet syngas at 350 degrees C. However, we observed the formation of a surface iron(II) oxide phase that increases with increasing H2O/CO ratio. This implies that the active surface of iron-based Fischer-Tropsch catalysts is covered by considerable amounts of adsorbed oxygen during the Fischer-Tropsch reaction. Reducing the temperature by only 20 K results in complete and irreversible oxidation to magnetite. We propose that the surface iron(II) oxide plays an important role during Fischer-Tropsch synthesis by regulating the relative rates of CO hydrogenation versus water gas shift and by stabilizing the iron carbide catalyst against irreversible deactivation by oxidation to magnetite.

In this paper we present an experimental protocol for protein immobilization on polydimethylsiloxane (PDMS) polymer surfaces and the subsequent application of a chromatographic PDMS microfluidic chip to measure protein-protein interactions. The PDMS surface modification steps are quantitatively and qualitatively experimentally analyzed using an array of techniques (water contact angle measurement, fluorescence spectroscopy and X-ray photoelectron spectroscopy). The protocol involves PDMS acidic surface activation using a potassium disulfite/potassium peroxidisulfate/acrylic acid mixture, followed by amination with 3-aminopropyl diethoxymethylsilane, followed by glutaraldehyde grafting and subsequent covalent protein binding. The applicability of such a miniaturized PDMS-based microfluidic system has been exemplified by measuring protein-protein interactions in a fast and accurate fashion for three model proteins, namely: hen egg white lysozyme, bovine ribonuclease-A and alpha-chymotrypsinogen. The protein interaction results align well with existing literature data using different materials and techniques. As the fabrication process for PDMS-based microstructures is relatively cheap, quick and requires limited lab expertise/access to specialized equipments, we consider that the implementation of such a flexible, easy to fabricate, PDMS-based microfluidic system for estimating protein interactions an important step toward quickly mapping protein phase behavior and measuring protein (self/cross) interactions in complex biological systems. (C) 2012 Elsevier B.V. All rights reserved.

Atmospheric pressure CVD (APCVD) is a highly cost effective method of depositing transparent conductive oxides (TCOs). In this work, insights in alcohol addition in the widely applied SnO2 process are discussed, including high resolution TEM images. Furthermore, the APCVD process of ZnO:Al was demonstrated on an industrial moving belt APCVD system. A high deposition rate of 14 nm/s, a resistivity down to 0.5 mOhm cm and a transparency about 85% in the visible range were obtained. Furthermore, modeling of the CVD process clearly enhanced understanding of the process and is a good tool for process optimization in combination with experimental verification. A-Si solar cells approaching 8% were obtained, using the ZnO on glass as a superstrate.

Aerobic oxidation of a thin film of octadecanol at 105°C and ambient pressures to its corresponding carbonyl derivatives (a mixture of aldehyde and carboxylic acid) was for the first time performed over a flat-model (i.e. two-dimensional), silicon wafer-supported metallic silver catalyst. The experimental set-up was extraordinary simple. An open-to-the-atmosphere glass beaker was used as reactor. Just enough octadecanol was placed on the silicon-supported catalytic surface to cover it with a thin film when melted. Reaction progress was monitored by ATR-FTIR analyses to identify the appearance of octadecanal and octadecanoic acid carbonyl stretching peaks at 1730 and 1710cm−1 respectively. The successful demonstration of this simple approach in studying catalysed small-molecule condensed organic reactions opens a new avenue towards simplified catalytic mechanistic studies of such processes. The catalyst was prepared by spin coating silver nitrate on a flat silicon wafer with (100) surface orientation, pretreated to have 4−5 silanol (SiOH) groups per nm2. Reduction by hydrogen at 350°C afforded metallic silver particles on the two-dimensional support at a nominal surface concentration of ca. 21–23 silver atoms/nm2. XPS differentiation between the catalyst precursor, AgNO3, and the metallic silver catalytic surface required use of the Auger MNN kinetic energies. TEM studies of the active catalyst showed no serious aggregation of metallic Ag particles occurred during reduction.

New routes for the preparation of highly active TiO(2)-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, (63)Cu nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO(2) catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO(2) at 120 °C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO(2) at 140 °C, corresponding to an initial reaction rate of 104 mmol g(cat) (-1) s(-1). The activation energy on the Cu/mesoporous TiO(2) catalyst was found to be (144±5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123±3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO(2) support (75±2 kJ mol(-1)).

To study the surface structure of MgCl(2) support and its interaction with other active components in Ziegler-Natta catalyst, such as electron donors, we prepared a thin film analogue for Ziegler-Natta ethylene polymerization catalyst support by spin-coating a solution of MgCl(2) in ethanol, optionally containing a diester internal donor (diisobutyl-ortho-phthalate, DIBP) on a flat Si crystal surface. The donor content of these films was quantified by applying attenuated total internal reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). Changes in the interaction of DIBP with MgCl(2) at various temperatures were monitored by in situ ATR-FTIR. Upon increasing the temperature, a shift in the (C═O) band toward lower wavenumbers was observed together with the depletion of (O-H) stretching band due to the desorption of residual ethanol. We assign this shift to gradual redistribution of adsorbed DIBP from adsorption sites on the MgCl(2) (104) surface toward the more acidic MgCl(2) (110) surface. The morphologies of MgCl(2) and MgCl(2)/DIBP films were studied by transmission electron microscopy (TEM) revealing a preferential orientation of ClMgCl layers (001) parallel to the lateral film dimensions. This orientation becomes more pronounced upon annealing. In the absence of donor, the MgCl(2) grow in to large crystals aligned in large domains upon annealing. Both crystal growth and alignment is impeded by the presence of donor.

Olivine ((Mg,Fe)2SiO4) has been extensively explored as an active bed material for catalytic cracking of tars during gasification of biomass in dual fluidized bed reactors. It is known that both the elemental composition, addition of Fe and high temperature calcinations influence the catalytic properties of this mineral. However, it is not clear how olivine responds to the fairly hostile environments present during gasification or what chemical state Fe takes during operation. We have investigated the stability of Austrian olivine under model conditions, resembling those in a gasifier. Powder samples were heated to 750°C in a quartz-tube flow-reactor and sequentially exposed to oxidizing (O2, H2O, CO2) or reducing gases (CO, H2) or mixtures thereof, for various durations of time. Significant changes in phase composition of the material, depending on the gas composition and the duration of the treatments, were found using X-ray photo-electron spectroscopy (XPS), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and scanning electron microscopy (SEM). A large fraction of the Fe in the investigated material is present as free Fe-phases, which are sensitive to changes in the gas environment. After exposure to oxidizing gases, the free Fe phases are: Fe2O3 and Fe3O4 or MgFe2O4. Upon exposure to reducing gases, the iron oxides are converted into Fe0 and Fe3C and formation of graphitic carbon is observed. In addition, the elemental composition of the surface changes dramatically depending on the gas composition. After exposure to oxidizing environments, the amount of Fe at the surface is twice as high as after reduction. Both the change in chemical state of the Fe-phases, the amount of surface Fe and the build-up of surface carbon are fast processes under the applied conditions and significant changes are observed on the time scale of one minute. These observations have important implications for olivine as a tar cracking catalyst, especially when used in dual fluidized bed gasifiers. The fast reduction of the iron oxides upon switching from oxidizing to reducing conditions shows that olivine transports oxygen from the combustor into the gasifier. Furthermore, the catalytic properties of Fe depend strongly on its chemical state. Therefore, the catalytic function of olivine depends strongly on the gas environment and on the catalysts residence time in the gasifier. Finally, both the decreasing amount of surface-Fe and the carbon deposition observed after exposing olivine to reducing conditions can result in significant catalyst deactivation.

Bone metastases are usually treated by surgical removal, fixation and chemotherapeutic treatment. Bone cement is used to fill the resection voids. The aim of this study was to develop a local drug delivery system using a calcium phosphate cement (CPC) as carrier for chemotherapeutic agents. CPC consisted of alpha-tricalcium phosphate, calcium phosphate dibasic and precipitated hydroxyapatite powders and a 2% Na2HPO4 hardening solution. Scanning electron microscopy (SEM) was used to observe CPC morphology. X-ray diffraction (XRD) was used to follow CPC transformation. The loading/release capacity of the CPC was studied by a bovine serum albumin-loading model. Release/retention was measured by high performance liquid chromatography and X-ray photoelectron spectrometry. For chemotherapeutic loading, paclitaxel (PX) was loaded onto the CPC discs by absorption. Viability of osteosarcoma U2OS and metastatic breast cancer MDA-MB-231 cells was measured by an AlamarBlue assay. Results of SEM and XRD showed changes in CPC due to its transformation. The loading model indicated a high retention behavior by the CPC composition. Cell viability tests indicated a PX minimal lethal dose of 90 μg/ml. PX released from CPC remained active to influence cell viability. In conclusion, this study demonstrated that CPC is a feasible delivery vector for chemotherapeutic agents.

Extended abstract of a paper presented at Microscopy and Microanalysis 2011 in Nashville, Tennessee, USA, August 7–August 11, 2011.