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Electrodeposition from an environmentally friendly iron sulfate electrolyte with citric acid as carbon source has gained attention recently, because of excellent mechanical properties of the resulting Fe–C coatings with intentionally codeposited high-carbon concentrations. While being very attractive as protective coatings and sustainable alternatives for hard chrome coatings, comprehensive understanding of the coatings' chemical constitution including the type and location of carbon-containing phases is still lacking. The amount of codeposited carbon of up to about 0.8 wt.% significantly exceeds the solubility of carbon in ferrite, although carbon-free ferrite is the only unambiguously reported phase in as-deposited Fe–C coatings so far. In the present work, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and soft X-ray emission spectroscopy have been applied to identify the carbon-containing phases, which are present as minor secondary phases in the coatings but are known to have an important influence on the coatings' properties. Three carbon-containing phases could be distinguished, homogeneously distributed in the nanocrystalline ferrite base material. Iron acetates, amorphous carbon, and carbides were found in both as-deposited and annealed Fe–C coatings up to 300°C, but their fraction changes during postdeposition annealing.

Calcium oxalate precipitation is a common pathological calcification in the human body, whereby crystallite morphology is influenced by the chelating properties of biological ions such as citrate.

Amino-alkylphosphonic acid-grafted TiO2 materials are of increasing interest in a variety of applications such as metal sorption, heterogeneous catalysis, CO2 capture, and enzyme immobilization. To date, systematic insights into the synthesis-properties-performance correlation are missing for such materials, albeit giving important know-how towards their applicability and limitations. In this work, the impact of the chain length and modification conditions (concentration and temperature) of amino-alkylphosphonic acid-grafted TiO2 on the surface properties and adsorption performance of palladium is studied. Via grafting with aminomethyl-, 3-aminopropyl-, and 6-aminohexylphosphonic acid, combined with the spectroscopic techniques (DRIFT, 31P NMR, XPS) and zeta potential measurements, differences in surface properties between the C1, C3, and C6 chains are revealed. The modification degree decreases with increasing chain length under the same synthesis conditions, indicative of folded grafted groups that sterically shield an increasing area of binding sites with increasing chain length. Next, all techniques confirm the different surface interactions of a C1 chain compared to a C3 or C6 chain. This is in line with palladium adsorption experiments, where only for a C1 chain, the adsorption efficiency is affected by the precursor concentration used for modification. The absence of a straightforward correlation between the number of free NH2 groups and the adsorption capacity for the different chain lengths indicates that other chain-length-specific surface interactions are controlling the adsorption performance. The increasing pH stability in the order of C1 < C3 < C6 can possibly be associated to a higher fraction of inaccessible hydrophilic sites due to the presence of folded structures. Lastly, the comparison of adsorption performance and pH stability with 3-aminopropyl(triethoxysilane)-grafted TiO2 reveals the applicability of both grafting methods depending on the envisaged pH during sorption. ispartof: ACS OMEGA vol:7 issue:49 pages:45409-45421 ispartof: location:United States status: published

Carbon nanofibers (CNFs) is a typical electrical loss material with strong permittivity that has been widely used in the field of electromagnetic shielding, attenuation, and reception. However, studies have demonstrated that the unstable anisotropic EM behavior exhibited by CNFs in the terahertz domain hinders its application in the tremendously high frequency domain. In this study, ZnO is used to perform surface modification of CNFs based on the sputtering method, which effectively eliminate the anisotropic EM behavior of CNFs at different irradiation angles in the sub-terahertz band. ZnO coated the surface of fiber wall comprehensively in the form of nano-scale. The results show that after the surface modification, the composite sample exhibits a stable isotropic EM response in the sub-terahertz band of 500-750 GHz. Also, in the frequency range of 551-563 GHz (bandwidth: 12 GHz), ZnO not only acts as a stabilizer, but also enhances the absorption performance of the original CNFs by 6%, which is up to 92%. In the frequency range of 660-690 GHz (bandwidth: 30 GHz), the composite sample and the pure CNFs sample have similar wave absorption performance with about 75%, the maximum difference is less than 5%, and the minimum is about 2.6%.

Vapor-phase film deposition of metal-organic frameworks (MOFs) would facilitate the integration of these materials into electronic devices. We studied the vapor-phase layer-by-layer deposition of zeolitic imidazolate framework 8 (ZIF-8) by consecutive, self-saturating reactions of diethyl zinc, water, and 2-methylimidazole on a substrate. Two approaches were compared: (1) Direct ZIF-8 "molecular layer deposition" (MLD), which enables a nanometer-resolution thickness control and employs only self-saturating reactions, resulting in smooth films that are crystalline as deposited, and (2) two-step ZIF-8 MLD, in which crystallization occurs during a postdeposition treatment with additional linker vapor. The latter approach resulted in a reduced deposition time and an improved MOF quality, i.e., increased crystallinity and probe molecule uptake, although the smoothness and thickness control were partially lost. Both approaches were developed in a modified atomic layer deposition reactor to ensure cleanroom compatibility.

Sulfur particles coated by activation of metal alkoxide precursors, aluminum-sulfur (Alu-S) and vanadium-sulfur (Van-S), were produced by dielectric barrier discharge (DBD) plasma technology under low temperature and ambient pressure conditions. We report a safe, solvent-free, low-cost, and low-energy consumption coating process that is compatible for sustainable technology up-scaling. NMR, XPS, SEM, and XRD characterization methods were used to determine the chemical characteristics and the superior behavior of Li-S cells using metal oxide-based coated sulfur materials. The chemical composition of the coatings is a mixture of the different elements present in the metal alkoxide precursor. The presence of alumina Al 2 O 3 within the coating was confirmed. Multi-C rate and long-term galvanostatic cycling at rate C/10 showed that the rate capability losses and capacity fade could be highly mitigated for the Li-S cells containing the coated sulfur materials in comparison to the references uncoated (raw) sulfur. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) confirm the lower charge-transfer resistance and potential hysteresis in the electrodes containing the coated sulfur particles. Our results show that the electro-chemical performance of the Li-S cells based on the different coating materials can be ranked as Alu-S > VanS > Raw sulfur.

Modification of metal oxides with organophosphonic acids (PAs) provides the ability to control and tailor the surface properties. The metal oxide phosphonic acid bond (M-O-P) is known to be stable under harsh conditions, making PAs a promising candidate for the recovery of metals from complex acidic leachates. The thiol functional group is an excellent regenerable scavenging group for these applications. However, the research on organophosphonic acid grafting with thiol groups is very limited. In this study, four different metal sorbent materials were designed with different thiol surface coverages. An aqueous-based grafting of 3-mercaptopropylphosphonic acid (3MPPA) on mesoporous TiO

Composites formed by a metal–organic framework (MOF) and an ionic liquid (IL) are potentially interesting materials for applications ranging from gas separation to electrochemical devices. Consequently, there is a need for robust and low-cost preparation procedures that are compatible with the desired applications. We herein report a solvent-free, one-step, and vapor-based ship-in-bottle synthesis of the IL@MOF composite 1-butyl-3-methylimidazolium bromide@ZIF-8 in powder and thin film forms. In this approach, volatile IL precursors evaporate and subsequently adsorb and react within the MOF cages to form the IL.

This work aims at the elucidation of the interfacial interactions established between an epoxy-amine coating and hot-dip galvanized (HDG) steel. The influence of the Zr-based conversion treatment of the substrate and the use of the Cu(II) additive on interfacial bonding is studied. To this purpose, an amine-functionalized molecule – diethylenetriamine (DETA) – is adsorbed. The complex multi-metal oxide surface of the Cu-modified Zr-based converted substrate is decomposed in derivative (simpler) systems. The resulting DETA-adsorbed model and multi-metal surfaces are investigated by X-ray photo-electron spectroscopy (XPS), and by examination of the N 1s peak, the interfacial bond density is determined. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) is performed to discriminate between the different metal oxide contributions present on the substrate surface. Preferential adsorption of the DETA molecule on the zinc atoms is found on converted substrates. The interfacial bonding with the Cu cationic sites introduced by the copper additive is proven.

Amino-alkylphosphonic acid-grafted TiO

This research unravels the formation mechanism of a hybrid conversion treatment including the well-established Zr conversion coating with a silane-based organic additive and Cu-based inorganic additive. The deposition mechanism of this coating was investigated on the thermal oxide film of Advanced High Strength Stainless Steels (AHSSS). This coating has been characterized using advanced surface analytical techniques such as XPS, FEG-AES, GDOES, and ToF-SIMS. The results showed that the simultaneous presence of these two additives results in the formation of a donor-acceptor complex between amine groups and Cu ions. The final coating contains Cu oxide together with a Cu-aminosilane complex, Zr oxide deposited mainly around Cu oxide and the aminosilane layer on the outer surface.

In the production of hydrogen gas, the removal of hydrogen chloride (HCl) is of particular relevance for the chemical industry. Here we report the HCl removal performance of ZIF-8 metal organic framework demonstrated via fixed-bed (dynamic) measurements under process conditions. The measurements revealed an HCl removal capacity of 1.02 g/g, outperforming by far all traditional materials and other metal-organic framework previously tested. The ZIF-8, before and after the HCl contact, was characterized via SEM-EDX, XRD, TGA, ATR-FTIR, XPS and Raman spectroscopy. The results showed a dramatic change in textural, structural and chemical properties of ZIF-8 after HCl contact, where the MOF material undergoes a reaction and re-crystalizes into a salt complex.

As the fabrication scale of graphene continues to expand, the limitations of existing mass characterization techniques such as Raman spectroscopy, AFM, and other microscopic characterization techniques for large-scale homogeneity characterization of graphene films become more and more prominent. Although the line-shaped defects (primarily grain boundaries and folds) distributed on the graphene film can be observed using the above techniques, it is difficult to comprehensively evaluate their distribution state on the entire film surface using these instruments. Based on this background, the author’s group has been aiming at the above problems by combining terahertz vector network analysis technology with the detection of large-area homogeneity of graphene films and quantitative characterization of line-shaped defects on the film surface, to explore a quality inspection technology that can be used in the production line of graphene films. The results demonstrate that the terahertz transverse electric (TE) wave is extremely sensitive to the variation of local thickness and electrical conductivity, which can be used in the homogeneity testing for the graphene; distributed line-shaped defects on graphene surface can exhibit anisotropic EM behavior with respect to THz TE waves, which can be exploited to identify the defect distribution states.

In this work, the separate diffusion of water and ions through a polyethylene glycol diacrylate (PEGDA) coating was characterized using an integrated spectro-electrochemical technique. The ions ingress front position profile along the thickness of the coating was derived from fitting odd random phase electrochemical impedance spectroscopy (ORP-EIS) data using a physically relevant electrochemical equivalent circuit (EEC). The arrival time of the ions at the coating/metal oxide buried interface obtained from EEC and rapid uptake of water was verified using in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) measurements in Kretschmann geometry integrated in the ORP-EIS set-up.

Many papers dealing with the surface analysis of plasma polymers or plasma-modified polymers report the use of X-ray photoelectron spectroscopy (XPS) to quantify the surface composition. However, most of the time, quantification is performed using software that includes an equation based on the assumption that the sample is homogeneous in composition. However, for plasma-treated samples, this is often not the case. The usual analysis of XPS spectra does not allow the exact quantification in the case of an inhomogeneous sample. In this paper, we show that it is possible to obtain a depth profile of the composition, and a more accurate surface composition by using another mathematical approach for surface quantification, being QUASES Tougaard.

The interactions of polymeric methylene diphenyl di-isocyanate (pMDI) and a model Fe–Cr alloy have been studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Films of two different thicknesses have been investigated: one with an extremely thin pMDI layer in which the interfacial chemistry can be probed directly and a thicker one in which sputter profiling using cluster ions is necessary to expose the interface chemistry for direct analysis. Multivariate analysis (MVA), using principal component analysis (PCA) and nonnegative matrix factorisation (NMF), has been used to identify specific ions associated with the interfacial region of the ToF-SIMS sputter depth profile and chemical species from the XPS sputter depth profile. As an unsupervised method, this avoids an unconscious bias on the part of the analyst. Specific ions associated with pMDI interactions with both Fe and Cr allow the proposal of two complementary reaction mechanisms, supported by theXPS data. A range of cluster ions is used in this investigation, but the bulk of the work used argon clusters for the XPS depth profiles and Buckminster Fullerene projectiles for the ToF-SIMS analyses. To ensure that such data were directly comparable, the ToF-SIMS sputter profiles were repeated in a different system of the same type using argon cluster ions.

A Vector Network Analyzer (VNA) is an indispensable piece of equipment for the electromagnetic characterization of materials. With continuous development, the testing frequency band of the VNA has entered the terahertz domain. Previous studies have shown that carbon nanofibers (CNFs) prepared by the vapor method have excellent absorbing characteristics for both the microwave and the millimeter wave. This study is the first to characterize CNFs using a VNA in the 500–750 GHz band. The results show that CNFs with a random orientation distribution have an obvious polarization-sensitive absorption behavior in the 500–750 GHz band test, and this effect also causes a phenomenon of polarized reflection. As a comparison, the CNF sample was also tested in the W-band by the same test method. However, the result tested in the W-band showed a strong absorbing characteristic without any polarization response. The mechanism of the above phenomena was analyzed from the perspective of crystal growth and the principle of the antenna and polarizer. For further exploration and proof, CST Microwave Studio was used for the first time to model and simulate CNFs according to the actual parameters of the CNF sample.

Organofunctional silanes are applied as coupling agents between organic coatings and low carbon steel substrates to promote adhesion. Although the metal oxide-silane interface plays an important role in the performance of the entire overlying coating system, it remains challenging to obtain a clear understanding of the interfacial molecular bonding mechanism and its influence on adhesion. In this work, time-of-flight secondary ion mass spectrometry is used to study interfacial interactions between aminopropyl triethoxysilane (APS) and low carbon steel. APS is shown to bond to the steel substrate through silanol steel and amine-steel interactions, and coatings are cured at varying temperatures to evaluate the influence of curing on these different types of bonding interactions. Unambiguous evidence for hydrogen bond interactions between APS silanol groups and steel surface hydroxyl groups is provided for the first time in this work through deuteration of the steel substrate and allows to tackle long-lasting doubts about the most wide-spread bonding theory that has been postulated for silane adsorption on metals.

The role of prior austenite grain size (PAGS) on the passive layer properties of martensitic steels is studied. Electron backscatter diffraction analysis shows that PAGS between 5 and 66 µm were obtained after applying different heat treatments. The barrier properties of passive film deteriorate with grain refinement up to 28 µm, attributed to increased donor density and a decrease in the fraction of γ-Fe2O3 in passive films. However, the further refinement of PAGS to 5 µm leads to improvement in the barrier properties due to the changes within the martensite structure. This improvement stems from the increase in γ-Fe2O3 fraction.

Modification of metal oxides with organophosphonic acids (PAs) provides the ability to control and tailor the surface properties. The metal oxide phosphonic acid bond (M-O-P) is known to be stable under harsh conditions, making PAs a promising candidate for the recovery of metals from complex acidic leachates. The thiol functional group is an excellent regenerable scavenging group for these applications. However, the research on organophosphonic acid grafting with thiol groups is very limited. In this study, four different metal sorbent materials were designed with different thiol surface coverages. An aqueous-based grafting of 3-mercaptopropylphosphonic acid (3MPPA) on mesoporous TiO2 was employed. Surface grafted thiol groups could be obtained in the range from 0.9 to 1.9 groups per nm(2). The different obtained surface properties were studied and correlated to the Pd adsorption performance. High Pd/S adsorption efficiencies were achieved, indicating the presence of readily available sorption sites. A large difference in their selectivity towards Pd removal from a spend automotive catalyst leachate was observed due to the co-adsorption of Fe on the titania support. The highest surface coverage showed the highest selectivity (K-d: 530 mL g(-1)) and adsorption capacity (Q(max): 0.32 mmol g(-1)) towards Pd, while strongly reducing the co-adsorption of Fe on remaining TiO2 sites. This work is supported by the Research Foundation Flanders (FWO) and Hasselt University via the Hercules project AUHL/15/ 2 – GOH3816N. Part of the presented work was executed within the PLATIRUS project, which has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 730224. This work reects only the author's views and the agency is not responsible for any use that may be made of the information it contains. The authors are grateful to all project partners for discussions and input, and in particular to Monolithos Ltd (Athens. Greece) for providing the spend automotive catalyst material used in this work. V. Meynen acknowledges the Research FoundationFlanders (FWO) for project K801621N. All calculations were performed using the Hopper HPC infrastructure at the CalcUA core facility of the University of Antwerp, a division of the Flemish Supercomputer Center VSC, funded by the Hercules Foundation, the Flemish Government (department EWI) and the University of Antwerp. Furthermore, the authors would like to acknowledge S. Defoss´e and K. Leyssens for the N2 sorption measurements, J. Lievens and A. Deibe Varela for the Pd sorption experiments, K. Duyssens and W. Brusten for the ICP measurements and M. Mertens for the XRD measurements.

A promising strategy for the inhibition of the hydrogen evolution reaction along with the stabilization of the electrocatalyst in electrochemical CO2 reduction cells involves the application of a nanoscale amorphous carbon layer on top of the active catalyst layer in a gas diffusion electrode. Without modifying the chemical nature of the electrocatalyst itself, these amorphous carbon layers lead to the stabilization of the electrocatalyst, and a significant improvement with respect to the inhibition of the hydrogen evolution reaction was also obtained. The faradaic efficiencies of hydrogen could be reduced from 31.4 to 2.1% after 1 h of electrolysis with a 5 nm thick carbon layer. Furthermore, the impact of the carbon layer thickness (5–30 nm) on this inhibiting effect was investigated. We determined an optimal thickness of 15 nm where the hydrogen evolution reaction was inhibited and a decent stability was obtained. Next, a thickness of 15 nm was selected for durability measurements. Interestingly, these durability measurements revealed the beneficial impact of the carbon layer already after 6 h by suppressing the hydrogen evolution such that an increase of only 37.9% exists compared to 56.9% without the use of an additional carbon layer, which is an improvement of 150%. Since carbon is only applied afterward, it reveals its great potential in terms of electrocatalysis in general.

Ag-based semiconductors have attracted significant attention as promising visible-light photocatalysts for environmental purification. In this study, electronic and photocatalytic properties of AgTi2(PO4)3 NASICON-type phosphate, have been addressed in detail, combining experimental results and theoretical calculations. The as-prepared sample was characterized for its morphological, structural and optical properties by various techniques. The generalized gradient approximation by Perdew-Burke-Ernzerhof (GGA-PPE) within density functional theory (DFT) was used to investigate the electronic structure. We have applied corrective Hubbard U terms to Ti 3d orbitals in order to better reproduce the experimental band gap of 2.6 eV. The photocatalytic activity has then been performed for rhodamine B dye degradation under visible light illumination. Efficient dye degradation up to 97.2% was achieved in 120 min. In addition, the catalyst exhibited good stability over four consecutive cycles. Finally, combining experimental and theoretical findings, the origin of the photocatalytic activity was identified and a photodegradation mechanism was proposed.

This research investigates the deposition mechanism of a hybrid Zr-aminosilane conversion coating as a replacement for the conventional pretreatment systems on a zinc substrate. The traditional Zr-based conversion treatment has been optimized by the addition of both Cu as an accelerator and aminosilane as an adhesion promotor. The deposition mechanism was unraveled using complementary surface analytical techniques such as XPS, FEG-AES, EDX, GDOES, and ToF-SIMS. The results showed the addition of aminosilane has resulted in the incorporation of N into the Zr oxide layer. This suggests that the influence of aminosilane is not only on the top surface, as an adhesion promoter, but also on the chemistry of the deposited layer. Additionally, the properties of this pretreatment on zinc is compared to Advanced High Strength Stainless Steel (AHSSS) as another automotive material. This was done in order to compare the behavior of active and passive substrates in the same conversion treatment. This comparison shows thatzinc as an active material can show higher interaction with the conversion treatment which results in a ticker film formation.

Film deposition and high-resolution patterning of ionic liquids (ILs) remain a challenge, despite a broad range of applications that would benefit from this type of processing. Here, we demonstrate for the first time the chemical vapor deposition (CVD) of ILs. The IL-CVD method is based on the formation of a non-volatile IL through the reaction of two vaporized precursors. Ionogel micropatterns can be easily obtained via the combination of IL-CVD and standard photolithography, and the resulting microdrop arrays can be used as microreactors. The IL-CVD approach will facilitate leveraging the properties of ILs in a range of applications and microfabricated devices. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:60 issue:49 pages:25668-25673 ispartof: location:Germany status: published

Copper producers face increased demand associated with increasing complexity in feedstock composition, including high amounts of impurity metals. In this work, linear sweep voltammetry was used to study the electrodeposition behavior of copper and arsenic, define strategies for the production of grade A copper, and the removal of arsenic from complex electrolytes. Our results show that the copper concentration is a key parameter to control in the electrodeposition process. The continuous deposition of arsenic from the electrolyte requires copper in solution (≤10 g L−1 Cu(II) for 2 g L−1 As(III)) to form copper arsenides. The deposition of metallic arsenic does not occur readily. Conversely, the use of a concentrated Cu(II) solution (e.g. 40 g L−1) resulted in grade A copper from an electrolyte with a maximum of 2 g L−1 As(III) under galvanostatic control at a current density of – 42 mA cm−2. Time-of-Flight Secondary Ion Mass Spectrometry depth profile measurements on copper deposits revealed that arsenic contamination was entirely concentrated near the substrate side of the deposit and progressively decreased further into the deposit. The codeposition of arsenic occurred along with the initial copper nucleation, when the electrochemical potential for electrodepostion under galvanostatic control is temporarily lower. These findings provide important insights for future sustainable copper electrodeposition technologies from complex feedstocks.

Recently, interest has been directed towards the grafting of metal oxides with organophosphonic acids bearing terminal amine groups to extend the functionality and applicability of these materials. Previous reports mainly focus on the application perspective, while a detailed characterization of the surface properties at the molecular level and the correlation with the synthesis conditions are missing. In this work, mesoporous TiO2 powder is grafted with 3-aminopropylphosphonic acid (3APPA) under different concentrations (20, 75, 150 mM) and temperatures (50, 90 °C) and compared with propylphosphonic acid (3PPA) grafting to unambiguously reveal the impact of the amine group on the surface properties. A combination of complementary spectroscopic techniques and Density Functional Theory-Periodic Boundary Conditions (DFT/PBC) calculations are used. At 90 °C and high concentrations, lower modification degrees are obtained for 3APPA compared to 3PPA, due to amine-induced surface interactions. Both X-ray Photoelectron Spectroscopy (XPS) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy reveal that both NH2 and NH3+ groups are present, with also contributions of NH2 groups involved in hydrogen bonding interactions. A similar ratio of NH2/NH3+ (65:35) is obtained irrespective of the modification conditions, suggesting similar relative contributions of different surface conformations. Calculated adsorption energies from DFT calculations on 3APPA adsorption on anatase (1 0 1) in relation to the water coverage reveals a coexistence of various structures with the amine group involved in intra-adsorbate, inter-adsorbate and adsorbate–surface interactions. Further validation is obtained from the strong overlap of different 31P environments represented by the broad band (35-12 ppm) in experimental 31P Nuclear Magnetic Resonance (NMR) spectra and calculated 31P chemical shifts of all modelled monodentate and bidentate structures. Structures related to the tridentate binding mode are not formed due to geometric restrictions of the anatase (1 0 1) facet applied as model support in the calculations. Nevertheless, they could be present in the experimental samples as they are composed of anatase (representing multiple crystal facets) and an amorphous titania fraction.

In this work, a new methodology is developed to study the initial behaviour of model organic coatings shortly after coming into contact with an aqueous solution, using odd random phase electrochemical impedance spectroscopy (ORP-EIS). The impedance results are resolved over time via the calculation of the instantaneous impedance and fitted with a physically meaningful equivalent circuit. Many physical parameters could be obtained, such as the rapid water uptake, the resistivity of the coatings and the penetration depth of ions in the coatings. The fitting results were verified using differential scanning calorimetry (DSC) and gravimetry.

Colloidal Cu-Ag nanocrystals measuring less than 10 nm across are promising candidates for integration in hybrid CO

Made available in DSpace on 2022-05-01T04:55:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-08-15 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) This work investigates the effect of Ce(III) and Ce(IV) additives on the structure and anti-corrosion properties of poly(methyl methacrylate) (PMMA)-silica coatings on AA7075 aluminium alloy. The results revealed that intermediate Ce(IV) loadings (500 and 1000 ppm) result in a dense hybrid network with a less defective polymeric phase, extending the service time of AA7075 up to 835 days in 3.5% NaCl. Although both additives provide long-term protection, the self-healing ability was observed only for Ce(IV) addition, favoured by the formation of oxides/hydroxides at pH∼3. These properties make the 4 μm-thick PMMA-silica-Ce(IV) coatings very interesting for chromium-free protection technologies. Sao Paulo State University Institute of Chemistry Vrije Universiteit Brussel Department of Electrochemical and Surface Engineering, Pleinlaan 2 Sao Paulo State University Institute of Chemistry FAPESP: 2014/12182-9 FAPESP: 2015/09342-7 FAPESP: 2015/11907-2

Filamentous cable bacteria display long-range electron transport, generating electrical currents over centimeter distances through a highly ordered network of fibers embedded in their cell envelope. The conductivity of these periplasmic wires is exceptionally high for a biological material, but their chemical structure and underlying electron transport mechanism remain unresolved. Here, we combine high-resolution microscopy, spectroscopy, and chemical imaging on individual cable bacterium filaments to demonstrate that the periplasmic wires consist of a conductive protein core surrounded by an insulating protein shell layer. The core proteins contain a sulfur-ligated nickel cofactor, and conductivity decreases when nickel is oxidized or selectively removed. The involvement of nickel as the active metal in biological conduction is remarkable, and suggests a hitherto unknown form of electron transport that enables efficient conduction in centimeter-long protein structures., Filamentous cable bacteria conduct electrical currents over centimeter distances through fibers embedded in their cell envelope. Here, Boschker et al. show that the fibers consist of a conductive core containing nickel proteins that is surrounded by an insulating protein shell.

Zinc oxide (ZnO), a wide direct band gap semiconductor, has attracted extensive attention for its potential optoelectronic applications, such as coherent ultraviolet light emitters. Pure one-dimensional ZnO, structures such as nanorods and nanowires, etc. inevitably have some crystal defects, which makes them to emit not only in the ultraviolet region but also in the visible range. Photoluminescent ZnO‑carbon nanocomposites are an emerging class of nanomaterials that has spurred a lot of interests due to its attractive optical properties. It has been shown that these composite structures yield an enhanced ultraviolet to visible emission ratio due to improved surface plasmon emission and a new defect emission mechanism. Hence, a novel one-dimensional structure of ZnO and carbon nanofibers composite material has been designed and prepared. The scaly ZnO is completely coated with carbon nanofibers. This new composite structure has strong ultraviolet emission photoluminescence characteristics in combination with low visible emission.

Although deep eutectic solvents (DES) and ethylene glycol (EG) electrolytes are gaining ground as media for the electrodeposition of metals, the influence of these electrolytes on the electrode and electrodeposits has not been elaborated before. In this work, we investigate how choline chloride: ethylene glycol based (ChCl:EG) electrolytes interact with the glassy carbon (GC) working surface at different potentials and, how these interactions change during the electrodeposition of iron from 1:2 and 1:4 ChCl:EG electrolytes. GC substrates are exposed to both electrolytes in absence of iron in order to study the pure electrolyte-substrate interactions. Linear sweep voltammetry was used to determine the potential range in which the different reactions occur, while time-of-flight secondary ion mass spectrometry (ToF-SIMS) was used to detect and identify the molecules adsorbed on the surface. In all systems, there is an accumulation of either choline or its derivatives on the electrode surface, with 1:4 ChCl:EG electrolytes showing different decomposition products from 1:2 ChCl:EG electrolytes. Choline accumulation and decomposition was also found on iron electrodeposits. The electrolyte composition has a major impact on the chemical speciation of iron, and on the deposit's adherence to the substrate. These are two crucial characteristics that define the efficiency of iron deposition from DES.

Copper dicarboxylate metal-organic framework films are deposited via chemical vapour deposition. Uniform films of CuBDC and CuCDC with an out-of-plane orientation and accessible porosity are obtained from the reaction of Cu and CuO with vaporised dicarboxylic acid linkers. ispartof: CHEMICAL COMMUNICATIONS vol:55 issue:55 pages:10056-10059 ispartof: location:England status: Published online

Chemical vapor deposition of metal-organic frameworks (MOF-CVD) will facilitate the integration of porous and crystalline coatings in electronic devices. In the two-step MOF-CVD process, a precursor layer is first deposited and subsequently converted to a MOF through exposure to linker vapor. We herein report the impact of different metal oxide and metalcone layers as precursors for zeolitic imidazolate framework ZIF-8 films. ispartof: DALTON TRANSACTIONS vol:50 issue:20 pages:6784-6788 ispartof: location:England status: published

The role of microstructural defects (dislocation density and grain boundary areas) on the passive film properties formed on cold- and hot-rolled interstitial free (IF) steels is investigated in 0.1 M NaOH solution. Electron backscattered diffraction (EBSD) shows higher microstructural defect density on cold-rolled samples. Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) results exhibit the lower barrier properties of passive films with the increase in microstructural defects. This is attributed to the increase in donor density measured with Mott-Schottky analysis and the lower relative quantity of protective γ-Fe2O3 in passive films (composed of Fe3O4,γ-Fe2O3 and FeO(OH)) with the increase in microstructural defect density.

Eleven series of water kefir fermentation processes differing in the presence of oxygen and the type and concentration of inoculum and substrate, were followed as a function of time to quantify the impact of these parameters on the kinetics of this process via a modeling approach. Increasing concentrations of the water kefir grain inoculum increased the water kefir fermentation rate, so that the metabolic activity during water kefir fermentation was mainly associated with the grains. Water kefir liquor could also be used as an alternative means of inoculation, but the resulting fermentation process progressed slower than the one inoculated with water kefir grains, and the production of water kefir grain mass was absent. Substitution of sucrose with glucose and/or fructose reduced the water kefir grain growth, whereby glucose was fermented faster than fructose. Lacticaseibacillus paracasei (formerly known as Lactobacillus paracasei), Lentilactobacillus hilgardii (formerly known as Lactobacillus hilgardii), Liquorilactobacillus nagelii (formerly known as Lactobacillus nagelii), Saccharomyces cerevisiae, and Dekkera bruxellensis were the main microorganisms present. Acetic acid bacteria were present in low abundances under anaerobic conditions and only proliferated under aerobic conditions. Visualization of the water kefir grains through scanning electron microscopy revealed that the majority of the microorganisms was attached onto their surface. Lactic acid bacteria and yeasts were predominantly associated with the grains, whereas acetic acid bacteria were predominantly associated with the liquor.

Colloidal Cu-Ag nanocrystals measuring less than 10 nm across are promising candidates for integration in hybrid CO2 reduction reaction (CO2RR) interfaces, especially in the context of tandem catalysis and selective multicarbon (C2-C3) product formation. In this work, we vary the synthetic-ligand/copper molar ratio from 0.1 to 1.0 and the silver/copper atomic ratio from 0 to 0.7 and study the variations in the nanocrystals' size distribution, morphology and reactivity at rates of ≥100 mA cm-2 in a gas-fed recycle electrolyzer operating under neutral to mildly basic conditions (0.1-1.0 M KHCO3). High-resolution electron microscopy and spectroscopy are used in order to characterize the morphology of sub-10 nm Cu-Ag nanodimers and core-shells and to elucidate trends in Ag coverage and surface composition. It is shown that Cu-Ag nanocrystals can be densely dispersed onto a carbon black support without the need for immediate ligand removal or binder addition, which considerably facilitates their application. Although CO2RR product distribution remains an intricate function of time, (kinetic) overpotential and processing conditions, we nevertheless conclude that the ratio of oxygenates to hydrocarbons (which depends primarily on the initial dispersion of the nanocrystals and their composition) rises 3-fold at moderate Ag atom % relative to Cu NCs-based electrodes. Finally, the merits of this particular Cu-Ag/C system and the recycling reactor employed are utilized to obtain maximum C2-C3 partial current densities of 92-140 mA cm-2 at -1.15 VRHE and liquid product concentrations in excess of 0.05 wt % in 1 M KHCO3 after short electrolysis periods.

Argon gas cluster ion beams (Ar-GCIBs) provide new opportunities for molecular depth profiling and imaging of organic materials and biological samples, thanks to recent technological developments that have led to the construction of new SIMS spectrometers where the traditional issues related to their low lateral resolution along with poor mass resolution and mass accuracy are overcome. The present fundamental contribution on SIMS molecular depth profiling investigates the variations of the secondary ion signals observed at the organic–inorganic hybrid interface when using Ar-GCIB as the analytical beam. With this in mind, depth profiling experiments were performed with a ToF-SIMS spectrometer using different analysis beams: 30-keV Bi5+ versus 10-keV Arn+ with a cluster size (n) of 800, 1500, 3000 and 5000 atoms, respectively. A 10-keV Ar3000+ beam was used for sputtering in all the experiments. Irganox 1010 and model polymers such as polystyrene (PS) and poly (methyl methacrylate) (PMMA) oligomers were chosen. Silicon wafer and a polymer-based substrates were employed to test materials with different stiffness, which is directly related to their Young’s moduli, an important parameter in this study. Ar-GCIB depth profiles systematically show ion signal enhancement of the characteristic fragments of PS and Irganox 1010 when approaching the interface with the silicon substrate, that can reach up to 60% for [M1010-H]− in Irganox films deposited onto silicon wafers. This enhancement increases with increasing n in both ion polarities. These results point out some ionization effects on the observed signal enhancement at the interface. The experimental observations will be explained on the basis of the physics of the impact of large argon clusters on different target materials and the energy confinement of the ion projectile in the organic overlayers. Finally, the thickness of organic films on rigid substrates in the nanoscale appears to be a crucial parameter to dramatically improve the sensitivity to molecular fragments when using large Ar cluster ions as analysis beams.

The use of electronic waste or low grade materials as feedstock for the electrolytic production of copper is challenging because impurity metals such as Sb(III) are introduced in the electrolyte. In this work, the mechanisms that lead to antimony contamination in electrolytic copper are studied. Linear sweep voltammetry experiments indicate that the reduction of Sb(III) is kinetically slow in the absence of Cu(II). In the presence of Cu(II), however, reduction of Sb(III) can occur readily by the codeposition of Cu(II) and Sb(III) as demonstrated by chronoamperometry. The ToF-SIMS analyses confirmed the codeposition of antimony in the very first micrometer of the copper deposit, enabled by the nucleation overpotential for galvanostatic copper electrodeposition under conditions relevant for the commercial production of copper. Based on potentiostatic electrodeposition experiments, we suggest that a copper concentration of ≥40 g L−1 Cu(II) in Sb(III) containing electrolytes is beneficial to obtain high purity copper. Codeposition reactions were impacted by the presence of additives (thiourea, glue and chloride ions). In particular, the addition of 0.02 g L−1 chloride mitigated the codeposition of antimony (0.02 g L−1 Sb(III)) to produce grade A copper. For optimal removal of Sb(III) from bleed electrolytes, a molar ratio of ~3 Cu(II)/Sb(III) should be maintained (e.g. 0.3 g L−1 Cu(II) for a typical concentration of 0.2 g L−1 Sb(III)).

In this work, immobilization of the often unwanted filaments in dielectric barrier discharges (DBD) is achieved and used for one-step deposition of patterned coatings. By texturing one of the dielectric surfaces, a discharge containing stationary plasma filaments is ignited in a mix of argon and propargyl methacrylate (PMA) in a reactor operating at atmospheric pressure. From PMA, hydrophobic and hydrophilic chemical and topographical contrasts at sub-millimeter scale are obtained on silicon and glass substrates. Chemical and physical characterizations of the samples are performed by micrometer-scale X-ray photoelectron spectroscopy and infrared imaging and by water contact angle and profilometry, respectively. From the latter and additional information from high-speed imaging of the plasma phase and electrical measurements, it is suggested that filaments, denser in energetic species, lead to higher deposition rate with higher fragmentation of the precursor, while surface discharges igniting outwards the filaments are leading to smoother and slower deposition. This work opens a new route for a one-step large-area chemical and morphological patterning of surfaces at sub-millimeter scales. Moreover, the possibility to separately deposit coatings from filaments and the surrounding plasma phase can be helpful to better understand the processes occurring during plasma polymerization in filamentary DBD.

Metal–organic frameworks (MOFs) offer disruptive potential in micro- and optoelectronics because of the unique properties of these microporous materials. Nanoscale patterning is a fundamental step in the implementation of MOFs in miniaturized solid-state devices. Conventional MOF patterning methods suffer from low resolution and poorly defined pattern edges. Here, we demonstrate the resist-free, direct X-ray and electron-beam lithography of MOFs. This process avoids etching damage and contamination and leaves the porosity and crystallinity of the patterned MOFs intact. The resulting high-quality patterns have excellent sub-50-nm resolution, and approach the mesopore regime. The compatibility of X-ray and electron-beam lithography with existing micro- and nanofabrication processes will facilitate the integration of MOFs in miniaturized devices. The low dielectric constants and high porosity of MOFs are of interest for applications in electronics and sensors, but patterning techniques for these materials are in their infancy. Here, direct X-ray and electron-beam lithography at sub-50-nm resolution are reported that leave porosity and crystallinity intact.

The overall performance of any organic coating system on a metal is largely dependent on the primer coating which has the crucial function to ensure adhesion to the metal substrate. Although performance in terms of adhesion can be empirically measured, the underlying chemical adhesion mechanism is difficult to unravel. A detailed molecular characterization of interfacial chemistry is required for this purpose, but brings up the challenge to reach the buried interface without inducing excessive damage to its molecular structure. In this work, argon gas cluster ions are being applied to sputter through an aminosilane coating on steel, in order to access the steel oxide-silane interface with time-of-flight secondary ion mass spectrometry (ToF-SIMS). In situ atomic force microscopy measurements during the sputter process demonstrate the importance of optimizing the Ar gas cluster ion beam in order to minimize sputter-induced roughness and molecular damage. ToF-SIMS spectra obtained at the buried steel oxide-aminosilane interface accessed by sputtering were compared to spectra from a steel oxide-aminosilane interface that was directly accessible without the need for sputtering. This comparison allowed us to identify contributions from sputter-induced damage in the buried interface spectra. Fragments characteristic for interfacial bonding interactions could be extracted, although there is a significant loss of molecular information because of sputtering. Nevertheless, insights into the role of steel surface hydroxyl groups in the adsorption mechanism of aminosilanes could be obtained through deuteration of the steel substrate.

The bonding properties of zirconium- and titanium-based conversion coatings were evaluated using model conversion solutions of H2ZrF6 and H2TiF6 with addition of various organic additives (PAA, PVA, PVP). Macroscopic testing techniques such as contact angle and pull-off adhesion measurements were performed on galvanized steel sheets. Complementary to this, molecular studies were performed on model zinc substrates using ATR-FTIR in the Kretschmann configuration. The macroscopic and molecular approaches showed a good correlation demonstrating ATR-FTIR in the Kretschmann configuration to be a valuable tool to gain fundamental insights in metal oxide-polymer interfacial phenomena. Zirconium-treated galvanized steel substrates were shown to have a higher bonding affinity for the polyester coil coat primer than titanium-treated galvanized steel substrates. The presence of organic additives did not further improve the bonding properties. Yet, organic additives initially improved the interfacial stability of titanium-treated substrates. However, on the long term, organic additives are shown to be detrimental for polyester coil coat adhesion. This adverse effect of organic additives on the long term was assigned to its selective dissolution during immersion and was most pronounced for titanium-treatments. The limited effect of organic additives in case of zirconium-treatments was attributed to the higher portion of chemical interfacial bonds, as well as its tendency for crosslinking reactions causing entanglement of polymeric compounds in the zirconium oxide structure.

Because of their molecular sieving properties, metal–organic frameworks have a high potential for application in gas storage, separation, and sensing. However, their real-world implementation will require robust and low-cost synthetic approaches. We herein report the solvent-free synthesis of ultramicroporous α-magnesium formate (α-MgFm) based on the solid–vapor reaction of magnesium oxide (MgO) and formic acid and establish the requirement for a structure-directing agent. Translated into a chemical vapor deposition protocol, this method enables the fabrication of high-quality, pinhole-free films of α-MgFm.

The effect of zirconium-based conversion of thermally vaporized zinc, aluminium and magnesium on the chemisorption of dimethylsuccinate was studied using attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Two competing chemisorption mechanisms contribute to interfacial bond formation. Hydrogen interactions on one hand were shown to occur between metal hydroxides and non-hydrolysed ester-groups of the molecule. On the other hand, both native and zirconium-treated substrates were shown to form interfacial carboxylate bonds with dimethylsuccinate, evidencing their capability of hydrolysing ester groups towards more reactive acid groups. Both interactions were shown to correlate to the metal oxide acid-base properties.

In this work, in-situ ATR-FTIR in the Kretschmann configuration is proposed as an interfacial sensitive technique able to probe molecular processes at the buried interface of an industrial relevant polyester primer. Zinc, aluminium and magnesium oxide were used to represent oxides present at galvanized steel sheets used in coil coating. Two competing interactions with polyester resin and melamine-based crosslinker were shown to take place at metal hydroxide sites. This highlights the increased complexity of interfacial phenomena at metal–paint interfaces. Furthermore, in-situ ATR-FTIR was performed in deuterated water (D2O) to study the evolution of interfacial carboxylate bond degradation, without overlap of dominant water signals. For the first time, interfacial bond formation of paints and its degradation in an aqueous environment is studied in-situ. It is shown that the introduction of D2O at the interface initially increases the amount of interfacial carboxylate bonds, whereas upon longer exposure times bond degradation occurs. Significant delay of interfacial bond degradation on hexafluorozirconic acid treated oxides indicate successful stabilization of the metal-polymer interface by zirconium-based conversion coatings. Consequently, in-situ ATR-FTIR is able to demonstrate improved interfacial stability due to zirconium-based treatment in real-time and on a molecular level.