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Co3O4 nanoparticles were supported on different TiO2 polymorphs, namely, rutile, anatase, and a 15 : 85 mixture of rutile and anatase (also known as P25), via incipient wetness impregnation. The Co3O4/TiO2 catalysts were evaluated in the preferential oxidation of CO (CO-PrOx) in a H2-rich gas environment and characterised in situ using PXRD and magnetometry. Our results show that supporting Co3O4 on P25 resulted in better catalytic performance, that is, a higher maximum CO conversion to CO2 of 72.7% at 200 °C was achieved than on rutile (60.7%) and anatase (51.5%). However, the degree of reduction (DoR) of Co3O4 to Co0 was highest on P25 (91.9% at 450 °C), with no CoTiO3 detected in the spent catalyst. The DoR of Co3O4 was lowest on anatase (76.4%), with the presence of TixOy-encapsulated CoOx nanoparticles and bulk CoTiO3 (13.8%) also confirmed in the spent catalyst. Relatively low amounts of CoTiO3 (8.9%) were detected in the spent rutile-supported catalyst, while a higher DoR (85.9%) was reached under reaction conditions. The Co0 nanoparticles formed on P25 and rutile existed in the fcc and hcp crystal phases, while only fcc Co0 was detected on anatase. Furthermore, undesired CH4 formation took place over the Co0 present in the P25- and rutile-supported catalysts, while CH4 was not formed over the Co0 on anatase possibly due to encapsulation by TixOy species. For the first time, this study revealed the influence of different TiO2 polymorphs (used as catalyst supports) on the chemical and crystal phase transformations of Co3O4, which in turn affect its activity and selectivity during CO-PrOx.

The Fischer-Tropsch synthesis as a large-scale industrial process converts a mixture of carbon monoxide and hydrogen in a surface polymerization reaction to mostly hydrocarbons and water. In fact, water is the most abundant product on a per mole basis. The major deactivation mechanisms for cobalt-based catalysts in the Fischer-Tropsch synthesis regarding the active metallic phase are various forms of carbon deposition, sintering, and oxidation to Fischer-Tropsch inactive oxidic phases. In particular high concentrations of the product water may cause oxidation and sintering of the active metallic cobalt phase, but are inherent to high conversion levels in the Fischer-Tropsch synthesis. Not only can cobalt be oxidized to CoO, it may also form mixed metal oxides such as cobalt aluminates in the presence of a metal oxide support. However, literature only provides limited information on the formation and morphology of such metal-support compounds due to the challenging (direct) characterization of these phases in the spent catalysts. Herein, thermodynamic predictions summarize and discuss the feasibility of water-induced deactivation of cobalt-based Fischer-Tropsch catalysts by oxidation. Further, identified mechanisms for hydrothermal sintering and recent findings on water-induced oxidation of metallic cobalt to CoO are discussed. However, the main emphasis of the review concerns the formation of metal-support compounds and the applicability of various in situ and ex situ characterization techniques on their identification. In particular X-ray absorption spectroscopy has recently provided significant insights into the formation of metal-support compounds in (simulated) high conversion Fischer-Tropsch environment, while high resolution microscopy was successfully applied to elucidate corresponding catalyst morphologies.

Increasing the comparability to large scale fermentations is a constant aim during scale-down, including growth-limiting feeding of the carbon source. Minibioreactor facilities greatly increase the throughput and offer many advantages. However, online measurements in this small scale often do not include critical process variables, necessary to control the feed rate. State estimators utilize mathematical models to estimate non-measurable states applying existing information about the inputs, outputs, and measurement uncertainties. Though, existing applications focus on bench-top or production-scale applications, where advanced process analytical technologies such as spectroscopic methods are available. Here, we present a concept for model-based nonlinear state estimation in a high-throughput platform with 24 parallel experiments in the mL-scale. An extended and a sigma-point Kalman filter are implemented based on online measurements only. The dissolved oxygen concentration and a relation of biomass growth and nitrogen consumption are used as measurement input. The current state of the cultivation is estimated iteratively throughout Escherichia coli cultivations and used to maintain predefined growth setpoints by adapting the feed rate. With this, we bring a further level of monitoring and process understanding to minibioreactor systems, and therefore enable automatization and optimization of miniaturized bioprocesses under controlled cultivation conditions.

[EN] Four Mo-based catalysts were prepared via three different synthesis techniques supported on SiO2 and/or SBA-15. By means of complementary in situ characterization techniques, the carburization process and the final characteristics of these catalysts were investigated. Additionally, the four catalysts were evaluated for the activation of CO2 in the absence and presence of H-2 (reverse water-gas shift, RWGS). The results suggest that CO2 reacts via a dissociation on the carbide surface, forming adsorbed oxygen surface species. Severe oxidation of the carbide into its oxidic phases (MoO2 or MoO3) only occurs at temperatures above 850 K in the presence of CO2. O-2 dissociates on the carbide surface when introduced at low concentrations (1 vol %) at room temperature, but when exposed to higher concentrations, a strong exothermic bulk re-oxidation reaction occurs, forming MoO2. All four catalysts show high RWGS activity in terms of CO2 conversions with a minimum CO selectivity of 98% without any signs of bulk catalyst oxidation. Although minimal, the observed deactivation is suggested to be primarily due to phase changes between Mo2C allotropes (beta-phase, oxycarbide, and eta-phase) and/or sintering of the active phase., All members affiliated with the Catalysis Institute and c*change would like to gratefully acknowledge the financial support received from the DST-NRF Centre of Excellence in Catalysis (c*change) and the University of Cape Town (UCT). We acknowledge Diamond Light Source for time on B18 as part of the Block Allocation Group beamtime of the UK Catalysis Hub in December 2018. A special thanks goes out to R. Cerpath and M. Malatji for their contributions in RWGS catalyst testing as part of their B.Sc. final year project; S. Govender, R. Geland, S. Klink, and S. Nyimbinya of the Analytical Laboratory in the Department of Chemical Engineering at UCT for the BET and ICP-OES analysis. M. Jaffer (UCT) for his support with the TEM analysis; M. Waldron for her assistance in the offline Raman analysis; and J. Callison and M. Panchal for their assistance in the offline XAS data acquisition. A. Mun~oz and I. Lopez (ITQ) are acknowledged for technical assistance with in situ Raman studies. We would like to thank the Institute for Beam Physics and Technology (IBPT) for the operation of the storage ring, the Karlsruhe Research Accelerator (KARA).

The identification of specific biomarkers for Zika infection and its clinical complications is fundamental to mitigate the infection spread, which has been associated with a broad range of neurological sequelae. We present the characterization of antibody responses in serum samples from individuals infected with Zika, presenting non-severe (classical) and severe (neurological disease) phenotypes, with high-density peptide arrays comprising the Zika NS1 and NS2B proteins. The data pinpoints one strongly IgG-targeted NS2B epitope in non-severe infections, which is absent in Zika patients, where infection progressed to the severe phenotype. This differential IgG profile between the studied groups was confirmed by multivariate data analysis. Molecular dynamics simulations and circular dichroism have shown that the peptide in solution presents itself in a sub-optimal conformation for antibody recognition, which led us to computationally engineer an artificial protein able to stabilize the NS2B epitope structure. The engineered protein was used to interrogate paired samples from mothers and their babies presenting Zika-associated microcephaly and confirmed the absence of NS2B IgG response in those samples. These findings suggest that the assessment of antibody responses to the herein identified NS2B epitope is a strong candidate biomarker for the diagnosis and prognosis of Zika-associated neurological disease.

The effect of both the Fe : Ni ratio (5 to 1 : 1) and the relative Lewis acidity of a metal oxide support on catalytic activity, selectivity and stability was investigated in the CO2 mediated oxidative dehydrogenation of ethane (CO2-ODH). To avoid effects of varying pore sizes, shapes and volumes of the supports, chromia and zirconia overlayers were coated onto a common γ-Al2O3 carrier (CrOx@Al2O3 and ZrOx@Al2O3). Separately, oxidic FexNiy alloy precursor nanoparticles were prepared using a nonaqueous surfactant-free method and deposited by sonication onto the carrier. In comparison to previous studies in the field, this synthesis technique yields closely associated iron and nickel increasing the chances for alloy formation. During reduction, a mixture of a bcc and a fcc alloy phase was formed, with the content of bcc increasing with increasing iron content as predicted by the bulk phase diagram. Upon exposure to carbon dioxide at elevated temperatures, the bcc metallic phase is selectively oxidised to an inverse spinel structure via the dissociation of CO2. When exposed to CO2-ODH conditions, the bare ZrOx@Al2O3 support shows no activity. The presence of FeNi phases increases the conversion of ethane and CO2 marginally ( 80%). The CrOx@Al2O3 support shows some initial activity (XC2H6 90%) but deactivates with time on stream. Comparison of the ethane and carbon dioxide conversions suggests that direct dehydrogenation rather than the oxidative pathway is taking place. When FeNi particles with the highest Fe content are added, the ethane conversion behavior hardly changes, but the CO2 conversion is increased now supporting the stoichiometric CO2-ODH reaction (SC2H4 > 95%). It is therefore evident that a tandem catalyst system between a reducible oxide carrier and the FeNi species is required. Increasing the Ni content results in an increase in activity and stability while changing the dominant reaction pathway to a combination of dry reforming, CO2-ODH and possibly the reverse Boudouard reaction, with the latter countering catalyst deactivation through carbon deposition.

The performance of Mo2C-based catalysts in CO2 assisted oxidative dehydrogenation (CO2-ODH) of ethane was evaluated. Mo2C on SiO2 was synthesized via three different techniques: wet impregnation (WI), hybrid nanocrystal technique (HNC) and sol–gel method (SG) and exposed to the same carburization conditions. In terms of characteristic properties, the allotrope composition was the most affected, with the SG sample containing MoOxCy and the WI and HNC samples containing β-Mo2C. The two different allotropes were suggested to follow different reaction pathways, leading to small differences in the catalytic performance. However, overall, all three catalysts showed a decrease in activity (below 6%) and an increase in C2H4 selectivity (from 60 to 80 C%) with time on stream (TOS). The deactivation mechanism was suggested to be mainly due to oxidation of the carbide to MoOx and carbon deposition. Mo2C was also supported on various metal oxide materials via the wet impregnation technique. Mo2C supported on Al2O3 and ZrO2 increased initial activity (about 8% C2H6 conversion) but a faster deactivation with TOS was observed. Mo2C/Ga2O3 favoured the direct dehydrogenation reaction achieving high C2H4 selectivities (above 80 C%), but deactivation with TOS due to carbon deposition was significant. Mo2C supported on CeO2 and TiO2 had lower activity (about 3% C2H6 conversion). Oxidation to MoO2 and carbon deposition is again suggested to be the main deactivation mechanism. H2 co-feeding, on Mo2C/SiO2 and Mo2C/ZrO2, increased the stability of the catalysts but C2H4 yield was affected (from 5 to 2%). At 17 vol% H2 co-feeding, Mo2C/ZrO2 showed promising catalyst stability over a 20 h period, paralleled by a stable C2H4 yield.

Transition metal alloys are receiving considerable attention in heterogeneous catalysis as they hold promise to combine advantageous properties of the constituting metals and, therefore, provide at...

The Fischer–Tropsch product, water, is regularly hypothesized to be the driving force for catalyst deactivation. Cobalt nanoparticles may be oxidized to CoO, form mixed-metal oxides with supports, or sinter to larger particles. This Comment discusses the feasibility of these deactivation pathways, highlighting the importance of in situ characterization.

The preferential oxidation of CO (CO-PrOx) with co-fed O2 is an attractive route for removing trace amounts of CO in the H2-rich reformate gas prior to being used for power generation in proton-exc...

We have studied the effect of different supports (CeO2, ZrO2, SiC, SiO2 and Al2O3) on the catalytic performance and phase stability of Co3O4 nanoparticles during the preferential oxidation of CO (CO-PrOx) under different H2-rich gas environments and temperatures. Our results show that Co3O4/ZrO2 has superior CO oxidation activity, but transforms to Co0 and consequently forms CH4 at relatively low temperatures. The least reduced and least methanation active catalyst (Co3O4/Al2O3) also exhibits the lowest CO oxidation activity. Co-feeding H2O and CO2 suppresses CO oxidation over Co3O4/ZrO2 and Co3O4/SiC, but also suppresses Co0 and CH4 formation. In conclusion, weak nanoparticle-support interactions (as in Co3O4/ZrO2) favour high CO oxidation activity possibly via the Mars-van Krevelen mechanism. However, stronger interactions (as in Co3O4/Al2O3) help minimise Co0 and CH4 formation. Therefore, this work reveals the bi-functional role required of supports used in CO-PrOx, i.e., to enhance catalytic performance and improve the phase stability of Co3O4.

Only little is known about the formation and morphology of metal-support compounds (MSCs) in heterogeneous catalysis. This fact can be mostly ascribed to the challenges in directly identifying these phases. In the present study, a series of Co/SiO2 model catalysts with different crystallite sizes was thoroughly characterised with focus on the identification of cobalt silicate, which is the expected metal-support compound for this particular catalyst system. The catalysts were exposed to simulated high conversion Fischer-Tropsch environment, i.e. water-rich conditions in the presence of hydrogen. The transformation of significant amounts of metallic cobalt to a hard-to-reduce phase has been observed. This particular MSC, Co2SiO4, was herein identified as needle- or platelet-type cobalt silicate structures by means of X-ray spectroscopy (XAS) and high-resolution scanning transmission electron microscopy (HRSTEM) in combination with elemental mapping. The metal-support compounds formed on top of fully SiO2-encapsulated nanoparticles, which are hypothesised to represent a prerequisite for the formation of cobalt silicate needles. Both, the encapsulation of cobalt nanoparticles by SiO2 \ud via creeping, as well as the formation of these structures, were seemingly induced by high concentrations of water.

Two NiO based oxygen carrier materials (OCMs) were synthesized and tested for use as potential materials in chemical looping reforming applications. Redox properties of these materials were evaluated in successive methane reduction – air oxidation (redox) cycles in a thermogravimetric analyzer unit (TGA) and an in situ magnetometer. Zirconia supported (Ni–Zr) OCM exhibited excellent redox activity (high degree of reduction and oxidation) and stability during ten CH4 reduction-air oxidation cycles. The degree of reduction of the alumina supported (Ni–Al) OCM increased gradually during cycling experiments, due to the formation of easily reducible NiO from nickel aluminate species with successive reduction/re-oxidation. The Ni–Al OCM exhibited excellent stability with respect to oxidation resulting in nearly complete oxidation of reduced Ni in all cycles. Results from measurements in the magnetometer were in good agreement with those in the TGA for the Ni–Zr OCM (both with regards to the degree of reduction and oxidation) and the degree of oxidation of the Ni–Al OCM. A moderate crystallite growth with cycling was observed for Ni–Al, whereas a decrease in nickel crystallite size was observed for Ni–Zr.

Supported nano-sized metal crystallites as catalysts in the Fischer-Tropsch synthesis have become a major research focus due to their high mass specific surface area and resulting lower cost. Such small supported cobalt crystallites have been reported to show a very different resistance with regard to deactivation compared to larger cobalt particles. The Fischer-Tropsch product water is reported to have a severe effect on the deactivation of cobalt-based Fischer-Tropsch catalysts. Compared to other water-induced deactivation mechanisms, hydrothermal sintering of cobalt nanoparticles is fairly well established in literature. A previously hypothesised interconnection between oxidation of cobalt nanoparticles and hydrothermal sintering has – for the first time – been captured in situ in the presented study. High concentrations of water induce oxidation of the cobalt nanoparticles increasing their mobility and resulting in crystallite growth via particle migration and coalescence whilst in the oxidised state. A well-defined model catalyst comprising highly dispersed cobalt nanoparticles on a relatively inert exfoliated graphite support in combination with an in situ magnetometer allowed for these observations, which resulted in irreversible deactivation of the catalyst.

High-density peptide arrays are an excellent means to profile anti-plasmodial antibody responses. Different protein intrinsic epitopes can be distinguished, and additional insights are gained, when compared with assays involving the full-length protein. Distinct reactivities to specific epitopes within one protein may explain differences in published results, regarding immunity or susceptibility to malaria. We pursued three approaches to find specific epitopes within important plasmodial proteins, (1) twelve leading vaccine candidates were mapped as overlapping 15-mer peptides, (2) a bioinformatical approach served to predict immunogenic malaria epitopes which were subsequently validated in the assay, and (3) randomly selected peptides from the malaria proteome were screened as a control. Several peptide array replicas were prepared, employing particle-based laser printing, and were used to screen 27 serum samples from a malaria-endemic area in Burkina Faso, West Africa. The immunological status of the individuals was classified as “protected” or “unprotected” based on clinical symptoms, parasite density, and age. The vaccine candidate screening approach resulted in significant hits in all twelve proteins and allowed us (1) to verify many known immunogenic structures, (2) to map B-cell epitopes across the entire sequence of each antigen and (3) to uncover novel immunogenic epitopes. Predicting immunogenic regions in the proteome of the human malaria parasite Plasmodium falciparum, via the bioinformatics approach and subsequent array screening, confirmed known immunogenic sequences, such as in the leading malaria vaccine candidate CSP and discovered immunogenic epitopes derived from hypothetical or unknown proteins.

The performance of Mo2C-based catalysts in CO2 assisted oxidative dehydrogenation (CO2-ODH) of ethane was evaluated. Mo2C on SiO2 was synthesized via three different techniques: wet impregnation (WI), hybrid nanocrystal technique (HNC) and sol-gel method (SG) and exposed to the same carburization conditions. In terms of characteristic properties, the allotrope composition was the most affected, with the SG sample containing MoOxCy and the WI and HNC samples containing β-Mo2C. The two different allotropes were suggested to follow different reaction pathways, leading to small differences in the catalytic performance. However, overall, all three catalysts showed a decrease in activity (below 6%) and an increase in C2H4 selectivity (from 60 to 80 C%) with time on stream (TOS). The deactivation mechanism was suggested to be mainly due to oxidation of the carbide to MoOx and carbon deposition. Mo2C was also supported on various metal oxide materials via the wet impregnation technique. Mo2C supported on Al2O3 and ZrO2 increased initial activity (about 8% C2H6 conversion) but a faster deactivation with TOS was observed. Mo2C/Ga2O3 favoured the direct dehydrogenation reaction achieving high C2H4 selectivities (above 80 C%), but deactivation with TOS due to carbon deposition was significant. Mo2C supported on CeO2 and TiO2 had lower activity (about 3% C2H6 conversion). Oxidation to MoO2 and carbon deposition is again suggested to be the main deactivation mechanism. H2 co-feeding, on Mo2C/SiO2 and Mo2C/ZrO2, increased the stability of the catalysts but C2H4 yield was affected (from 5 to 2%). At 17 vol% H2 co-feeding, Mo2C/ZrO2 showed promising catalyst stability over a 20 h period, paralleled by a stable C2H4 yield.

The presented study investigated the effects of temperature (350–650 °C) and gas environment (pure Ar versus a H2O/H2 partial pressure ratio (PH2O/PH2) of 5) on the extent of sintering and oxidation of Al2O3-supported Ni0 nanoparticles (≈4 nm). We note that a PH2O/PH2 of 5 corresponds to a simulated CO conversion of 94% during methanation. Sintering and oxidation were studied using in situ magnetometry, while ex situ TEM analyses confirmed the particle sizes before and after the magnetometry-based experiments. It was found that increasing the temperature from 350 to 650 °C in Ar at atmospheric pressure causes a negligible change to the average size and degree of reduction (DOR) of the starting Ni0 nanoparticles. However, studying the same temperature window under hydrothermal conditions at 10 bar causes significant particle growth (≈9 nm) and the development of a bimodal distribution. Furthermore, the presence of steam decreases the DOR of Ni0 from 86.2% after initial activation to 22.2% due to oxidation. In summary, this study reports on the expected sintering and oxidation of Ni-based catalysts under high CO conversion conditions at elevated temperatures during methanation. Importantly, we were able to demonstrate how magnetometry-based analyses can provide similar size information (and changes thereof) as those observed with TEM but with the added advantage that this information can be obtained in situ.

In this manuscript we describe the engineering of a biomarker for the diagnosis and prognosis of Zika-associated neurological disease. Although the causal association between congenital Zika virus (ZIKV) infection and neurological manifestations has been well documented in the recent years, biomarkers for proper diagnostic and disease outcome still remain to be defined. Combining high-density peptide array and multivariate analysis, we have identified an ZIKV epitope that is associated to a lack of IgG antibody response in patients with severe neurological symptoms. An engineered chimera was developed to discriminate between mild and severe clinical forms of the disease.

The effect of both the Fe : Ni ratio (5 to 1 : 1) and the relative Lewis acidity of a metal oxide support on catalytic activity, selectivity and stability was investigated in the CO

Pancreatic &beta, cell-specific clock knockout mice develop &beta, cell oxidative-stress and failure, as well as glucose-intolerance. How inflammatory stress affects the cellular clock is under-investigated. Real-time recording of Per2:luciferase reporter activity in murine and human pancreatic islets demonstrated that the proinflammatory cytokine interleukin-1&beta, (IL-1&beta, ) lengthened the circadian period. qPCR-profiling of core clock gene expression in insulin-producing cells suggested that the combination of the proinflammatory cytokines IL-1&beta, and interferon-&gamma, (IFN-&gamma, ) caused pronounced but uncoordinated increases in mRNA levels of multiple core clock genes, in particular of reverse-erythroblastosis virus &alpha, (Rev-erb&alpha, ), in a dose- and time-dependent manner. The REV-ERB&alpha, /&beta, agonist SR9009, used to mimic cytokine-mediated Rev-erb&alpha, induction, reduced constitutive and cytokine-induced brain and muscle arnt-like 1 (Bmal1) mRNA levels in INS-1 cells as expected. SR9009 induced reactive oxygen species (ROS), reduced insulin-1/2 (Ins-1/2) mRNA and accumulated- and glucose-stimulated insulin secretion, reduced cell viability, and increased apoptosis levels, reminiscent of cytokine toxicity. In contrast, low (&lt, 5,0 &mu, M) concentrations of SR9009 increased Ins-1 mRNA and accumulated insulin-secretion without affecting INS-1 cell viability, mirroring low-concentration IL-1&beta, mediated &beta, cell stimulation. Inhibiting nitric oxide (NO) synthesis, the lysine deacetylase HDAC3 and the immunoproteasome reduced cytokine-mediated increases in clock gene expression. In conclusion, the cytokine-combination perturbed the intrinsic clocks operative in mouse and human pancreatic islets and induced uncoordinated clock gene expression in INS-1 cells, the latter effect associated with NO, HDAC3, and immunoproteasome activity.

In this study, the effect of the presence of Pt in supported Co-based Fischer–Tropsch catalysts is investigated. To this end, the effect of the addition of 0.1 wt% Pt to the formulation of Al2O3-supported catalysts containing “large” (≈20 nm) or “small” (≈10 nm) Co3O4 crystallites is presented. The cobalt particle size can be changed by the presence of diethylene glycol (DEG) in Co-nitrate precursor solution. Pt is deposited on the support by following either the sequential deposition order (SDO), according to which Pt is impregnated onto the calcined Co-catalyst, or the reverse sequential deposition order (RSDO), according to which Pt is impregnated onto the support before Co. We show that despite the small amount of Pt used and regardless of the initial Co3O4 crystallite size and of the deposition order of Pt and Co, the catalyst reducibility is significantly improved when Pt is added to the catalyst formulation. Indeed, Pt favors the reduction of the smallest Co oxide particles, which are hardly reducible in the unpromoted samples, thus shifting the average Co0 particle size towards smaller values. In particular, in the case of “large” Co3O4 particles, Pt has a larger effect when added according to the RSDO method, very likely due to the stronger interaction that is established between Pt and Co. In comparison, the sample with smaller Co3O4 particles (prepared with DEG) shows a higher reducibility when prepared according to the SDO method, due to the presence of a significant fraction of small and difficult to reduce Co3O4 particles. The effect of Pt on the catalytic performance depends on a complex interplay involving the catalyst reducibility, number of Co metal sites and size of the Co0 particle aggregates. Pt strongly improves the performance of the samples originating from the larger cobalt oxide crystallites but on the other hand decreases the reactivity of the samples from the smaller particles. This is due to the fact that the small Co0 sites formed in the presence of Pt are in the size-range where the FTS is known to be structure sensitive and the intrinsic activity (TOF) is reduced.

The inert nature of graphitic samples allows for characterisation of rather isolated supported nanoparticles in model catalysts, as long as sufficiently large inter-particle distances are obtained. However, the low surface area of graphite and the little interaction with nanoparticles result in a challenging application of conventional preparation routes in practice. In the present study, a set of graphitic carbon materials was characterised in order to identify potential support materials for the preparation of model catalyst systems. Various sizes of well-defined Co3O4 nanoparticles were synthesised separately and supported onto exfoliated graphite powder, that is graphite after solvent-assisted exfoliation via ultrasonication resulting in thinner flakes with increased specific surface area. The stability of the supported nanoparticles during reduction to metallic cobalt in H2 was monitored in situ by means of X-ray diffraction and smaller crystallite sizes were found to be harder to reduce than their larger counterparts. A low cobalt loading of 1 wt% was required to avoid aggregates in the parent catalyst, and this allowed for the preparation of supported cobalt nanoparticles which were resistant to sintering at reduction temperatures below 370 °C. The developed model catalysts are ideally suited for sintering studies of isolated nano-sized cobalt particles as the graphitic support material does not provide distinct metal–support interaction. Furthermore, the differently sized cobaltous particles in the various model systems render possible studies on structural dependencies of activity, selectivity, and deactivation in cobalt oxide or cobalt catalysed reactions.

A surfactant-free synthesis of highly monodisperse Co3O4 nanoparticles via a sol-gel route was scaled-up in order to yield up to one gram of nanoparticles with a narrow size distribution. Parameters allowing for an accurate control of the crystallite size were identified and systematically evaluated. Application of Taguchi's method for experimental design revealed an increase in crystallite size with increasing synthesis temperature or concentration of the cobalt precursor. However, the amount of additive NH4OH(aq), respectively the associated water, has the most pronounced effect on the resulting crystallite size. Water was identified as the main source of oxygen and is required to yield single-phase Co3O4 nanoparticles. An ideal mixing of the reaction mixture is crucial for the availability of water during the synthesis. The outcome allows for the controlled synthesis of monodisperse, single-phase Co3O4 nanoparticles in the range of 2.8 to 9.8 nm with relative standard deviations ranging from 13 to 19%. Further, conducting the synthesis in the absence of water yields monodisperse, single-phase, and highly crystalline CoO nanoparticles.

The effectiveness of the addition of diethylene glycol (DEG) to the impregnating solution in synthesizing highly dispersed Co-based catalysts supported on stabilized alumina (Al2O3(s)) is investigated. Both the properties and catalytic performance in the Fischer-Tropsch synthesis (FTS) of the material obtained using DEG (CoDEG/Al2O3(s)) are compared with those of a catalyst with the same formulation but prepared without the addition of DEG in the impregnating solution (Co/Al2O3(s)). When using Co-nitrate as Co-precursor, the addition of DEG leads to a very fast and exothermic decomposition of Co-nitrate into Co oxides during the calcination step. This prevents the agglomeration of Co3O4 particles, thus generating highly dispersed Co3O4 crystallites on the support. In line with the decrease of the Co3O4 crystallites size, the CoDEG/Al2O3(s) catalyst is more difficult to reduce than the Co/Al2O3(s) catalyst. As a result, the metallic surface of the two catalysts is very similar. Nonetheless, when tested in the FTS, the CoDEG/Al2O3(s) catalyst shows CO conversion higher than the Co/Al2O3(s) sample. This is attributed to the high intrinsic activity (i.e. high Turnover Frequency, TOF) of the small Co0 crystallites of the CoDEG/Al2O3(s) catalyst. We explain this result assuming that the combustion phenomenon occurring during the fast calcination induced by the presence of DEG may generate structural defects on the catalyst surface that are beneficial for the FTS. Notably, the product distribution of CoDEG/Al2O3(s) catalyst is only slightly affected.

The Fischer–Tropsch (FT) process, producing long chained waxes and transportation fuels, is competing with fuels derived from crude oils and its profitability is therefore dependent on the global oil price. However, increasing the value of synthesized products could render the profitability of the FTS independent of the common fluctuations in the commodity price (which are mostly due to global political trends and only to a lesser extent due to market requirements). One way to achieve this, is to target the more valuable products of the Fischer–Tropsch spectrum, for example oxygenates. This study investigates the effect of synthesis protocols on the surface characteristics of molybdenum carbide and the use of potassium promoted Mo2C as a catalyst for higher oxygenate (C2+ oxygenates) synthesis in CO hydrogenation. A graphitic surface layer was observed with TEM, XPS and Raman analysis for Mo2C samples carburized at ≥760 °C. The graphitic carbon, blocking active sites and therefore significantly lowering catalytic activity, could be partially removed by means of a temperature programmed hydrogenation, forming methane. An unpromoted β-Mo2C catalyst, carburized at 630 °C, reached CO conversions up to ±40% at the conditions applied. Initial 6.2 wt% K/Mo promotion of the catalyst with potassium showed a significant drop in catalyst activity, however, an increase in potassium content did not further decrease catalyst activity. The selectivity towards oxygenates was enhanced, yet it has a certain optimum with regards to promotor concentration. Simultaneously, the oxygenate distribution shifted towards higher alcohols. The initial methanol content in the total oxygenate product was around 60 C% and decreased to approximately 20 C% upon potassium promotion.

Emergence and re-emergence of pathogens bearing the risk of becoming a pandemic threat are on the rise. Increased travel and trade, growing population density, changes in urbanization, and climate have a critical impact on infectious disease spread. Currently, the world is confronted with the emergence of a novel coronavirus SARS-CoV-$_{2}$, responsible for yet more than 800 000 deaths globally. Outbreaks caused by viruses, such as SARS-CoV-$_{2}$, HIV, Ebola, influenza, and Zika, have increased over the past decade, underlining the need for a rapid development of diagnostics and vaccines. Hence, the rational identification of biomarkers for diagnostic measures on the one hand, and antigenic targets for vaccine development on the other, are of utmost importance. Peptide microarrays can display large numbers of putative target proteins translated into overlapping linear (and cyclic) peptides for a multiplexed, high-throughput antibody analysis. This enabled for example the identification of discriminant/diagnostic epitopes in Zika or influenza and mapping epitope evolution in natural infections versus vaccinations. In this review, we highlight synthesis platforms that facilitate fast and flexible generation of high-density peptide microarrays. We further outline the multifaceted applications of these peptide array platforms for the development of serological tests and vaccines to quickly encounter pandemic threats.

We consider massless fields of arbitrary spin in de Sitter space. We introduce a spinor-helicity formalism, which encodes the field data on a cosmological horizon. These variables reduce the free S-matrix in an observer's causal patch, i.e. the evolution of free fields from one horizon to another, to a simple Fourier transform. We show how this result arises via twistor theory, by decomposing the horizonhorizon problem into a pair of (more symmetric) horizontwistor problems., Comment: 5 pages; v2: improved references, introduction

Different supporting procedures were followed to alter the nanoparticle–support interactions (NPSI) in two Co3O4/Al2O3 catalysts, prepared using the reverse micelle technique. The catalysts were tested in the dry preferential oxidation of carbon monoxide (CO-PrOx) while their phase stability was monitored using four complementary in situ techniques, viz., magnet-based characterization, PXRD, and combined XAS/DRIFTS, as well as quasi in situ XPS, respectively. The catalyst with weak NPSI achieved higher CO2 yields and selectivities at temperatures below 225 °C compared to the sample with strong NPSI. However, relatively high degrees of reduction of Co3O4 to metallic Co were reached between 250 and 350 °C for the same catalyst. The presence of metallic Co led to the undesired formation of CH4, reaching a yield of over 90% above 300 °C. The catalyst with strong NPSI formed very low amounts of metallic Co (less than 1%) and CH4 (yield of up to 20%) even at 350 °C. When the temperature was decreased from 350 to 50 °C under the reaction gas, both catalysts were slightly reoxidized and gradually regained their CO oxidation activity, while the formation of CH4 diminished. The present study shows a strong relationship between catalyst performance (i.e., activity and selectivity) and phase stability, both of which are affected by the strength of the NPSI. When using a metal oxide as the active CO-PrOx catalyst, it is important for it to have significant reduction resistance to avoid the formation of undesired products, e.g., CH4. However, the metal oxide should also be reducible (especially on the surface) to allow for a complete conversion of CO to CO2 via the Mars–van Krevelen mechanism.

The inert nature of graphitic samples allows for characterisation of rather isolated supported nanoparticles in model catalysts, as long as sufficiently large inter-particle distances are obtained. However, the low surface area of graphite and the little interaction with nanoparticles result in a challenging application of conventional preparation routes in practice. In the present study, a set of graphitic carbon materials was characterised in order to identify potential support materials for the preparation of model catalyst systems. Various sizes of well-defined Co3O4 nanoparticles were synthesised separately and supported onto exfoliated graphite powder, that is graphite after solvent-assisted exfoliation via ultrasonication resulting in thinner flakes with increased specific surface area. The developed model catalysts are ideally suited for sintering studies of isolated nano-sized cobaltous particles as the graphitic support material does not provide distinct metal-support interaction. Furthermore, the differently sized cobaltous particles in the various model systems render possible studies on structural dependencies of activity, selectivity, and deactivation in cobalt oxide or cobalt catalysed reactions.

The formation of mixed-metal cobalt oxides, representing potential metal-support compounds for cobalt-based catalysts, has been observed at high conversion levels in the Fischer-Tropsch synthesis over metal oxide-supported cobalt catalysts. An often observed increase in the carbon dioxide selectivity at Fischer Tropsch conversion levels above 80% has been suggested to be inter-linked to the formation of water-gas shift active oxidic cobalt species. Mixed-metal cobalt oxides, namely cobalt aluminate and cobalt titanate, were therefore synthesised and tested for potential catalytic activity towards the water-gas shift reaction. We present a preparation route for amorphous mixed-metal oxides via thermal treatment of metal precursors in benzyl alcohol. Calcination of the as prepared nanoparticles results in highly crystalline phases. The nano-particulate mixed-metal cobalt oxides were thoroughly analysed by means of X-ray diffraction, Raman spectroscopy, temperature-programmed reduction, X-ray absorption near edge structure spectroscopy, and high-resolution scanning transmission electron microscopy. This complementary characterisation of the synthesised materials allows for a distinct identification of the phases and their properties. The cobalt aluminate prepared has a cobalt-rich composition (Co1+xAl2-xO4) with a homogeneous atomic distribution throughout the nano-particulate structures, while the perovskite-type cobalt titanate (CoTiO3) features cobalt-lean smaller particles being associated with larger ones with an increased concentration of cobalt. The cobalt aluminate prepared showed no water-gas shift activity in the medium-shift temperature range, while the cobalt titanate sample was shown to catalyse the conversion of water and carbon monoxide to hydrogen and carbon dioxide after an extended activation period. However, this perovskite underwent vast restructuring forming metallic cobalt, a known catalyst for the water-gas shift reaction at temperatures exceeding typical conditions for the cobalt-based Fischer-Tropsch synthesis, and anatase-TiO2 via a partial reduction of the mixed-metal cobalt oxide and segregation as identified by means of post-run X-ray diffraction.

The preferential oxidation of carbon monoxide has been identified as an effective route to remove trace amounts of CO (approx. 0.5–1.0 vol%) in the H2-rich reformate gas stream after the low-temperature water–gas shift. Instead of noble metal-based catalysts, Co3O4-based catalysts were investigated in this study as cheaper and more readily available alternatives. This study aimed at investigating the effect of crystallite size on the mass- and surface area-specific CO oxidation activity as well as on the reduction behaviour of Co3O4. Model Co3O4 catalysts with average crystallite sizes between 3 and 15 nm were synthesised using the reverse micelle technique. Results from the catalytic tests revealed that decreasing the size of the Co3O4 crystallites increased the mass-specific CO oxidation activity in the 50–200 °C temperature range. On the other hand, the surface area-specific CO oxidation activity displayed a volcano-type behaviour where crystallites with an average size of 8.5 nm were the most active within the same temperature range. In situ characterisation in the magnetometer revealed that the Co3O4 crystallites are partially reduced to metallic Co above 225 °C with crystallites larger than 7.5 nm showing higher degrees of reduction under the H2-rich environment of CO-PrOx. In situ PXRD experiments further showed the presence of CoO concurrently with metallic fcc Co in all the catalysts during the CO-PrOx runs. In all experiments, the formation of fcc Co coincided with the formation of CH4. Upon decreasing the reaction temperature below 250 °C under the reaction gas, both in situ techniques revealed that the fcc Co previously formed is partially re-oxidised to CoO.

The preferential oxidation (PrOx) of carbon monoxide is an effective process for the removal of trace amounts of CO in a hydrogen-rich gas stream originating from steam reforming or gasification processes. CO can act as catalyst poison in various downstream processes such as the ammonia synthesis or PEM fuel cells for power generation. The effect on activity and selectivity of different cobalt oxide morphologies (cubes, sheets and belts) in Co3O4/SiO2 model catalysts was studied against conventional near-spherical nanoparticles. With a combination of offline and specialized in situ characterisation techniques the stability and catalytic performance of the model catalysts was monitored. With TEM and XRD, the prepared nanosheets and nanobelts were identified as superstructures constituted by small crystallites with similar catalytic activity to conventional nanoparticles. The nanocubes however, consisting of single crystals or at least large crystalline domains, display a superior surface specific CO oxidation activity which is attributed to the preferential exposure of {001} planes. Catalytic sites on these plains seem to support the formation of the Co3+/2+ redox pair required for the underlying Mars-van Krevelen mechanism.