“Plasma-catalytic dry reforming of methane: Screening of catalytic materials in a coaxial packed-bed DBD reactor”. Andersen Ja, Christensen Jm, Østberg M, Bogaerts A, Jensen Ad, Chemical Engineering Journal 397, 125519 (2020). http://doi.org/10.1016/j.cej.2020.125519
Abstract: The combination of catalysis with non-thermal plasma is a promising alternative to thermal catalysis. A dielectric-barrier discharge reactor was used to study plasma-catalytic dry reforming of methane at ambient pressure and temperature and a fixed plasma power of 45 W. The effect of different catalytic packing materials was evaluated in terms of conversion, product selectivity, and energy efficiency. The conversion of CO2 (~22%) and CH4 (~33%) were found to be similar in plasma-only and when introducing packing materials in plasma. The main reason is the shorter residence time of the gas due to packing geometry, when compared at identical flow rates. H2, CO, C2-C4 hydrocarbons, and oxygenates were identified in the product gas. High selectivity towards H2 and CO were found for all catalysts and plasma-only, with a H2/CO molar ratio of ~0.9. The lowest syngas selectivity was obtained with Cu/Al2O3 (~66%), which instead, had the highest alcohol selectivity (~3.6%).
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 15.1
DOI: 10.1016/j.cej.2020.125519
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“Plasma-Based CO2Conversion: To Quench or Not to Quench?”.Vermeiren V, Bogaerts A, Journal Of Physical Chemistry C 124, 18401 (2020). http://doi.org/10.1021/acs.jpcc.0c04257
Abstract: Plasma technology is gaining increasing interest for CO2 conversion. The gas temperature in (and after) the plasma reactor largely affects the performance. Therefore, we examine the effect of cooling/quenching, during and after the plasma, on the CO2 conversion and energy efficiency, for typical “warm” plasmas, by means of chemical kinetics modeling. For plasmas at low specific energy input (SEI ∼ 0.5 eV/molecule), it is best to quench at the plasma end, while for high-SEI plasmas (SEI ∼ 4 eV/molecule), quenching at maximum conversion is better. For low-SEI plasmas, quenching can even increase the conversion beyond the dissociation in the plasma, known as superideal quenching. To better understand the effects of quenching at different plasma conditions, we study the dissociation and recombination rates, as well as the vibrational distribution functions (VDFs) of CO2, CO, and O2. When a high vibrational−translational (VT) nonequilibrium exists at the moment of quenching, the dissociation and recombination reaction rates both increase. Depending on the conversion degree at the moment of quenching, this can lead to a net increase or decrease of CO2 conversion. In general, however, and certainly for equilibrium plasmas at high temperature, quenching after the plasma helps prevent recombination reactions and clearly enhances the final CO2 conversion. We also investigate the effect of different quenching cooling rates on the CO2 conversion and energy efficiency. Finally, we compare plasma-based conversion to purely thermal conversion. For warm plasmas with typical temperatures of 3000−4000 K, the conversion is roughly thermal.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.7
DOI: 10.1021/acs.jpcc.0c04257
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“The 2020 plasma catalysis roadmap”. Bogaerts A, Tu X, Whitehead JC, Centi G, Lefferts L, Guaitella O, Azzolina-Jury F, Kim H-H, Murphy AB, Schneider WF, Nozaki T, Hicks JC, Rousseau A, Thevenet F, Khacef A, Carreon M, Journal Of Physics D-Applied Physics 53, 443001 (2020). http://doi.org/10.1088/1361-6463/ab9048
Abstract: Plasma catalysis is gaining increasing interest for various gas conversion applications, such as CO2 conversion into value-added chemicals and fuels, CH4 activation into hydrogen, higher hydrocarbons or oxygenates, and NH3 synthesis. Other applications are already more established, such as for air pollution control, e.g. volatile organic compound remediation, particulate matter and NOx removal. In addition, plasma is also very promising for catalyst synthesis and treatment. Plasma catalysis clearly has benefits over ‘conventional’ catalysis, as outlined in the Introduction. However, a better insight into the underlying physical and chemical processes is crucial. This can be obtained by experiments applying diagnostics, studying both the chemical processes at the catalyst surface and the physicochemical mechanisms of plasma-catalyst interactions, as well as by computer modeling. The key challenge is to design cost-effective, highly active and stable catalysts tailored to the plasma environment. Therefore, insight from thermal catalysis as well as electro- and photocatalysis is crucial. All these aspects are covered in this Roadmap paper, written by specialists in their field, presenting the state-of-the-art, the current and future challenges, as well as the advances in science and technology needed to meet these challenges.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.4
DOI: 10.1088/1361-6463/ab9048
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“H2S Decomposition into H2 and S2 by Plasma Technology: Comparison of Gliding Arc and Microwave Plasma”. Zhang Q-Z, Wang WZ, Thille C, Bogaerts A, Plasma Chemistry And Plasma Processing 40, 1163 (2020). http://doi.org/10.1007/s11090-020-10100-3
Abstract: We studied hydrogen sulfide (H2S) decomposition into hydrogen (H2) and sulfur (S2) in a gliding arc plasmatron (GAP) and microwave (MW) plasma by a combination of 0D and 2D models. The conversion, energy efficiency, and plasma distribution are examined for different discharge conditions, and validated with available experiments from literature. Furthermore, a comparison is made between GAP and MW plasma. The GAP operates at atmospheric pressure, while the MW plasma experiments to which comparison is made were performed at reduced pressure. Indeed, the MW discharge region becomes very much contracted near atmospheric pressure, at the conditions under study, as revealed by our 2D model. The models predict that thermal reactions play the most important role in H2S decomposition in both plasma types. The GAP has a higher energy efficiency but lower conversion than the MW plasma at their typical conditions. When compared at the same conversion, the GAP exhibits a higher energy efficiency and lower energy cost than the MW plasma.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.6
DOI: 10.1007/s11090-020-10100-3
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“How gas flow design can influence the performance of a DBD plasma reactor for dry reforming of methane”. Uytdenhouwen Y, Hereijgers J, Breugelmans T, Cool P, Bogaerts A, Chemical Engineering Journal 405, 126618 (2021). http://doi.org/10.1016/j.cej.2020.126618
Abstract: DBD plasma reactors are commonly used in a static ‘one inlet – one outlet’ design that goes against reactor design principles for multi-component reactions, such as dry reforming of methane (DRM). Therefore, in this paper we have developed a novel reactor design, and investigated how the shape and size of the reaction zone, as well as gradual gas addition, and the method of mixing CO2 and CH4 can influence the conversion and product com position of DRM. Even in the standard ‘one inlet – one outlet’ design, the direction of the gas flow (i.e. short or long path through the reactor, which defines the gas velocity at fixed residence time), as well as the dimensions of the reaction zone and the power delivery to the reactor, largely affect the performance. Using gradual gas addition and separate plasma activation zones for the individual gases give increased conversions within the same operational parameters, by optimising mixing ratios and kinetics. The choice of the main (pre-activated) gas and the direction of gas flow largely affect the conversion and energy cost, while the gas inlet position during separate addition only influences the product distribution.
Keywords: A1 Journal article; Engineering sciences. Technology; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 6.216
DOI: 10.1016/j.cej.2020.126618
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“On the kinetics and equilibria of plasma-based dry reforming of methane”. Uytdenhouwen Y, Bal Km, Neyts Ec, Meynen V, Cool P, Bogaerts A, Chemical Engineering Journal 405, 126630 (2021). http://doi.org/10.1016/j.cej.2020.126630
Abstract: Plasma reactors are interesting for gas-based chemical conversion but the fundamental relation between the plasma chemistry and selected conditions remains poorly understood. Apparent kinetic parameters for the loss and formation processes of individual components of gas conversion processes, can however be extracted by performing experiments in an extended residence time range (2–75 s) and fitting the gas composition to a firstorder kinetic model of the evolution towards partial chemical equilibrium (PCE). We specifically investigated the differences in kinetic characteristics and PCE state of the CO2 dissociation and CH4 reforming reactions in a dielectric barrier discharge reactor (DBD), how these are mutually affected when combining both gases in the dry reforming of methane (DRM) reaction, and how they change when a packing material (non-porous SiO2) is added to the reactor. We find that CO2 dissociation is characterized by a comparatively high reaction rate of 0.120 s−1 compared to CH4 reforming at 0.041 s−1; whereas CH4 reforming reaches higher equilibrium conversions, 82% compared to 53.6% for CO2 dissociation. Combining both feed gases makes the DRM reaction to proceed at a relatively high rate (0.088 s−1), and high conversion (75.4%) compared to CO2 dissociation, through accessing new chemical pathways between the products of CO2 and CH4. The addition of the packing material can also distinctly influence the conversion rate and position of the equilibrium, but its precise effect depends strongly on the gas composition. Comparing different CO2:CH4 ratios reveals the delicate balance of the combined chemistry. CO2 drives the loss reactions in DRM, whereas CH4 in the mixture suppresses back reactions. As a result, our methodology provides some of the insight necessary to systematically tune the conversion process.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.216
DOI: 10.1016/j.cej.2020.126630
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“Modeling plasmas in analytical chemistry—an example of cross-fertilization”. Bogaerts A, Analytical And Bioanalytical Chemistry 412, 6059 (2020). http://doi.org/10.1007/s00216-020-02587-8
Abstract: This paper gives an overview of the modeling work developed in our group in the last 25 years for various plasmas used in analytical spectrochemistry, i.e., glow discharges (GDs), inductively coupled plasmas (ICPs), and laser ablation (LA) for sample introduction in the ICP and for laser-induced breakdown spectroscopy (LIBS). The modeling approaches are briefly presented, which are different for each case, and some characteristic results are illustrated. These plasmas are used not only in analytical chemistry but also in other applications, and the insights obtained in these other fields were quite helpful for us to develop models for the analytical plasmas. Likewise, there is now a huge interest in plasma–liquid interaction, atmospheric pressure glow discharges (APGDs), and dielectric barrier discharges (DBDs) for environmental, medical, and materials applications of plasmas. The insights obtained in these fields are also very relevant for ambient desorption/ionization sources and for liquid sampling, which are nowadays very popular in analytical chemistry, and they could be very helpful in developing models for these sources as well.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.3
DOI: 10.1007/s00216-020-02587-8
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“Mechanisms of selective nanocarbon synthesis inside carbon nanotubes”. Khalilov U, Neyts EC, Carbon 171, 72 (2021). http://doi.org/10.1016/j.carbon.2020.08.060
Abstract: The possibility of confinement effects inside a carbon nanotube provides new application opportunities, e.g., growth of novel carbon nanostructures. However, the understanding the precise role of catalystfeedstock in the nanostructure synthesis is still elusive. In our simulation-based study, we investigate the Ni-catalyzed growth mechanism of encapsulated carbon nanostructures, viz. double-wall carbon nanotube and graphene nanoribbon, from carbon and hydrocarbon growth precursors, respectively. Specifically, we find that the tube and ribbon growth is determined by a catalyst-vs-feedstock competition effect. We compare our results, i.e., growth mechanism and structure morphology with all available theoretical and experimental data. Our calculations show that all encapsulated nanostructures contain metal (catalyst) atoms and such structures are less stable than their pure counterparts. Therefore, we study the purification mechanism of these structures. In general, this study opens a possible route to the controllable synthesis of tubular and planar carbon nanostructures for today’s nanotechnology.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.337
DOI: 10.1016/j.carbon.2020.08.060
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“Metal-insulator transition of SrVO 3 ultrathin films embedded in SrVO 3 / SrTiO 3 superlattices”. Wang J, Gauquelin N, Huijben M, Verbeeck J, Rijnders G, Koster G, Applied Physics Letters 117, 133105 (2020). http://doi.org/10.1063/5.0020615
Abstract: The metal-insulator transition (MIT) in strongly correlated oxides is a topic of great interest for its potential applications, such as Mott field effect transistors and sensors. We report that the MIT in high quality epitaxial SrVO3 (SVO) thin films is present as the film thickness is reduced, lowering the dimensionality of the system, and electron-electron correlations start to become the dominant interactions. The critical thickness of 3 u.c is achieved by avoiding effects due to off-stoichiometry using optimal growth conditions and excluding any surface effects by a STO capping layer. Compared to the single SVO thin films, conductivity enhancement in SVO/STO superlattices is observed. This can be explained by the interlayer coupling effect between SVO sublayers in the superlattices. Magnetoresistance and Hall measurements indicate that the dominant driving force of MIT is the electron–electron interaction.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 4
Times cited: 8
DOI: 10.1063/5.0020615
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“Simultaneous heteroepitaxial growth of SrO (001) and SrO (111) during strontium-assisted deoxidation of the Si (001) surface”. Jovanović, Z, Gauquelin N, Koster G, Rubio-Zuazo J, Ghosez P, Verbeeck J, Suvorov D, Spreitzer M, Rsc Advances 10, 31261 (2020). http://doi.org/10.1039/D0RA06548J
Abstract: Epitaxial integration of transition-metal oxides with silicon brings a variety of functional properties to the well-established platform of electronic components. In this process, deoxidation and passivation of the silicon surface are one of the most important steps, which in our study were controlled by an ultra-thin layer of SrO and monitored by using transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), synchrotron X-ray diffraction (XRD) and reflection high energy electron diffraction (RHEED) methods. Results revealed that an insufficient amount of SrO leads to uneven deoxidation of the silicon surface<italic>i.e.</italic>formation of pits and islands, whereas the composition of the as-formed heterostructure gradually changes from strontium silicide at the interface with silicon, to strontium silicate and SrO in the topmost layer. Epitaxial ordering of SrO, occurring simultaneously with silicon deoxidation, was observed. RHEED analysis has identified that SrO is epitaxially aligned with the (001) Si substrate both with SrO (001) and SrO (111) out-of-plane directions. This observation was discussed from the point of view of SrO desorption, SrO-induced deoxidation of the Si (001) surface and other interfacial reactions as well as structural ordering of deposited SrO. Results of the study present an important milestone in understanding subsequent epitaxial integration of functional oxides with silicon using SrO.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 3.9
Times cited: 1
DOI: 10.1039/D0RA06548J
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“Hidden Markov model for atom-counting from sequential ADF STEM images: Methodology, possibilities and limitations”. De wael A, De Backer A, Van Aert S, Ultramicroscopy 219, 113131 (2020). http://doi.org/10.1016/j.ultramic.2020.113131
Abstract: We present a quantitative method which allows us to reliably measure dynamic changes in the atomic structure of monatomic crystalline nanomaterials from a time series of atomic resolution annular dark field scanning transmission electron microscopy images. The approach is based on the so-called hidden Markov model and estimates the number of atoms in each atomic column of the nanomaterial in each frame of the time series. We discuss the origin of the improved performance for time series atom-counting as compared to the current state-of-the-art atom-counting procedures, and show that the so-called transition probabilities that describe the probability for an atomic column to lose or gain one or more atoms from frame to frame are particularly important. Using these transition probabilities, we show that the method can also be used to estimate the probability and cross section related to structural changes. Furthermore, we explore the possibilities for applying the method to time series recorded under variable environmental conditions. The method is shown to be promising for a reliable quantitative analysis of dynamic processes such as surface diffusion, adatom dynamics, beam effects, or in situ experiments.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 2.2
DOI: 10.1016/j.ultramic.2020.113131
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“Cold Atmospheric Plasma Treatment for Pancreatic Cancer–The Importance of Pancreatic Stellate Cells”. Verloy R, Privat-Maldonado A, Smits E, Bogaerts A, Cancers 12, 2782 (2020). http://doi.org/10.3390/cancers12102782
Abstract: Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease with low five-year survival rates of 8% by conventional treatment methods, e.g., chemotherapy, radiotherapy, and surgery. PDAC shows high resistance towards chemo- and radiotherapy and only 15–20% of all patients can have surgery. This disease is predicted to become the third global leading cause of cancer death due to its significant rise in incidence. Therefore, the development of an alternative or combinational method is necessary to improve current approaches. Cold atmospheric plasma (CAP) treatments could offer multiple advantages to this emerging situation. The plasma-derived reactive species can induce oxidative damage and a cascade of intracellular signaling pathways, which could lead to cell death. Previous reports have shown that CAP treatment also influences cells in the tumor microenvironment, such as the pancreatic stellate cells (PSCs). These PSCs, when activated, play a crucial role in the propagation, growth and survival of PDAC tumors. However, the effect of CAP on PSCs is not yet fully understood. This review focuses on the application of CAP for PDAC treatment and the importance of PSCs in the response to treatment.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Center for Oncological Research (CORE)
DOI: 10.3390/cancers12102782
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“Structural modification of NADPH oxidase activator (Noxa 1) by oxidative stress: An experimental and computational study”. Attri P, Park J-H, De Backer J, Kim M, Yun J-H, Heo Y, Dewilde S, Shiratani M, Choi EH, Lee W, Bogaerts A, International Journal Of Biological Macromolecules 163, 2405 (2020). http://doi.org/10.1016/j.ijbiomac.2020.09.120
Abstract: NADPH oxidases 1 (NOX1) derived reactive oxygen species (ROS) play an important role in the progression of cancer through signaling pathways. Therefore, in this paper, we demonstrate the effect of cold atmospheric plasma (CAP) on the structural changes of Noxa1 SH3 protein, one of the regulatory subunits of NOX1. For this purpose, firstly we purified the Noxa1 SH3 protein and analyzed the structure using X-ray crystallography, and subsequently, we treated the protein with two types of CAP reactors such as pulsed dielectric barrier discharge (DBD) and Soft Jet for different time intervals. The structural deformation of Noxa1 SH3 protein was analyzed by various experimental methods (circular dichroism, fluorescence, and NMR spectroscopy) and by MD simulations. Additionally, we demonstrate the effect of CAP (DBD and Soft Jet) on the viability and expression of NOX1 in A375 cancer cells. Our results are useful to understand the structural modification/oxidation occur in protein due to reactive oxygen and nitrogen (RONS) species generated by CAP.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 8.2
DOI: 10.1016/j.ijbiomac.2020.09.120
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“Free energy barriers from biased molecular dynamics simulations”. Bal KM, Fukuhara S, Shibuta Y, Neyts EC, Journal Of Chemical Physics 153, 114118 (2020). http://doi.org/10.1063/5.0020240
Abstract: Atomistic simulation methods for the quantification of free energies are in wide use. These methods operate by sampling the probability density of a system along a small set of suitable collective variables (CVs), which is, in turn, expressed in the form of a free energy surface (FES). This definition of the FES can capture the relative stability of metastable states but not that of the transition state because the barrier height is not invariant to the choice of CVs. Free energy barriers therefore cannot be consistently computed from the FES. Here, we present a simple approach to calculate the gauge correction necessary to eliminate this inconsistency. Using our procedure, the standard FES as well as its gauge-corrected counterpart can be obtained by reweighing the same simulated trajectory at little additional cost. We apply the method to a number of systems—a particle solvated in a Lennard-Jones fluid, a Diels–Alder reaction, and crystallization of liquid sodium—to demonstrate its ability to produce consistent free energy barriers that correctly capture the kinetics of chemical or physical transformations, and discuss the additional demands it puts on the chosen CVs. Because the FES can be converged at relatively short (sub-ns) time scales, a free energy-based description of reaction kinetics is a particularly attractive option to study chemical processes at more expensive quantum mechanical levels of theory.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 4.4
DOI: 10.1063/5.0020240
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“Entropic and enthalpic factors determining the thermodynamics and kinetics of carbon segregation from transition metal nanoparticles”. Fukuhara S, Bal KM, Neyts EC, Shibuta Y, Carbon 171, 806 (2021). http://doi.org/10.1016/j.carbon.2020.09.059
Abstract: The free energy surface (FES) for carbon segregation from nickel nanoparticles is obtained from advanced molecular dynamics simulations. A suitable reaction coordinate is developed that can distinguish dissolved carbon atoms from segregated dimers, chains and junctions on the nanoparticle surface. Because of the typically long segregation time scale (up to ms), metadynamics simulations along the developed reaction coordinate are used to construct FES over a wide range of temperatures and carbon concentrations. The FES revealed the relative stability of different stages in the segregation process, and free energy barriers and rates of the individual steps could then be calculated and decomposed into enthalpic and entropic contributions. As the carbon concentration in the nickel nanoparticle increases, segregated carbon becomes more stable in terms of both enthalpy and entropy. The activation free energy of the reaction also decreases with the increase of carbon concentration, which can be mainly attributed to entropic effects. These insights and the methodology developed to obtain them improve our understanding of carbon segregation process across materials science in general, and the nucleation and growth of carbon nanotube in particular.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 6.337
DOI: 10.1016/j.carbon.2020.09.059
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“Pore Chemistry of Metal–Organic Frameworks”. Ji Z, Wang H, Canossa S, Wuttke S, Yaghi OM, Advanced Functional Materials 30, 2000238 (2020). http://doi.org/10.1002/adfm.202000238
Abstract: The pores in metal–organic frameworks (MOFs) can be functionalized by placing chemical entities along the backbone and within the backbone. This chemistry is enabled by the architectural, thermal, and chemical robustness of the frameworks and the ability to characterize them by many diffraction and spectroscopic techniques. The pore chemistry of MOFs is articulated in terms of site isolation, coupling, and cooperation and relate that to their functions in guest recognition, catalysis, ion and electron transport, energy transfer, pore‐dynamic modulation, and interface construction. It is envisioned that the ultimate control of pore chemistry requires arranging functionalities into defined sequences and developing techniques for reading and writing such sequences within the pores.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT)
Impact Factor: 19
DOI: 10.1002/adfm.202000238
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“Standard Practices of Reticular Chemistry”. Gropp C, Canossa S, Wuttke S, Gándara F, Li Q, Gagliardi L, Yaghi OM, Acs Central Science 6, 1255 (2020). http://doi.org/10.1021/acscentsci.0c00592
Abstract: Since 1995 when the first of metal−organic frameworks was crystallized with the strong bond approach, where metal ions are joined by charged organic linkers exemplified by carboxylates, followed by proof of their porosity in 1998 and ultrahigh porosity in 1999, a revolution in the development of their chemistry has ensued. This is being reinforced by the discovery of two- and three-dimensional covalent organic frameworks in 2005 and 2007. Currently, the chemistry of such porous, crystalline frameworks is collectively referred to as reticular chemistry, which is being practiced in over 100 countries. The involvement of researchers from various backgrounds and fields, and the vast scope of this chemistry and its societal applications, necessitate articulating the “Standard Practices of Reticular Chemistry”.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
Impact Factor: 18.2
DOI: 10.1021/acscentsci.0c00592
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“Efficient Phase Contrast Imaging via Electron Ptychography, a Tutorial”. Pennycook TJ, Martinez GT, O'Leary CM, Yang H, Nellist PD, Microscopy and microanalysis 25, 2684 (2019). http://doi.org/10.1017/S1431927619014156
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT)
DOI: 10.1017/S1431927619014156
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“Risk Evaluation of EMT and Inflammation in Metastatic Pancreatic Cancer Cells Following Plasma Treatment”. Freund E, Spadola C, Schmidt A, Privat-Maldonado A, Bogaerts A, von Woedtke T, Weltmann K-D, Heidecke C-D, Partecke L-I, Käding A, Bekeschus S, Frontiers in physics 8 (2020). http://doi.org/10.3389/fphy.2020.569618
Abstract: The requirements for new technologies to serve as anticancer agents go far beyond their toxicity potential. Novel applications also need to be safe on a molecular and patient level. In a broader sense, this also relates to cancer metastasis and inflammation. In a previous study, the toxicity of an atmospheric pressure argon plasma jet in four human pancreatic cancer cell lines was confirmed and plasma treatment did not promote metastasis in vitro and in ovo. Here, these results are extended by additional types of analysis and new models to validate and define on a molecular level the changes related to metastatic processes in pancreatic cancer cells following plasma treatment in vitro and in ovo. In solid tumors that were grown on the chorion-allantois membrane of fertilized chicken eggs (TUM-CAM), plasma treatment induced modest to profound apoptosis in the tissues. This, however, was not associated with a change in the expression levels of adhesion molecules, as shown using immunofluorescence of ultrathin tissue sections. Culturing of the cells detached from these solid tumors for 6d revealed a similar or smaller total growth area and expression of ZEB1, a transcription factor associated with cancer metastasis, in the plasma-treated pancreatic cancer tissues. Analysis of in vitro and in ovo supernatants of 13 different cytokines and chemokines revealed cell line-specific effects of the plasma treatment but a noticeable increase of, e.g., growth-promoting interleukin 10 was not observed. Moreover, markers of epithelial-to-mesenchymal transition (EMT), a metastasis-promoting cellular program, were investigated. Plasma-treated pancreatic cancer cells did not present an EMT-profile. Finally, a realistic 3D tumor spheroid co-culture model with pancreatic stellate cells was employed, and the invasive properties in a gel-like cellular matrix were investigated. Tumor outgrowth and spread was similar or decreased in the plasma conditions. Altogether, these results provide valuable insights into the effect of plasma treatment on metastasis-related properties of cancer cells and did not suggest EMT-promoting effects of this novel cancer therapy.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.1
DOI: 10.3389/fphy.2020.569618
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“3D Characterization and Plasmon Mapping of Gold Nanorods Welded by Femtosecond Laser Irradiation”. Milagres de Oliveira T, Albrecht W, González-Rubio G, Altantzis T, Lobato Hoyos IP, Béché, A, Van Aert S, Guerrero-Martínez A, Liz-Marzán LM, Bals S, Acs Nano 14, acsnano.0c02610 (2020). http://doi.org/10.1021/acsnano.0c02610
Abstract: Ultrafast laser irradiation can induce morphological and structural changes in plasmonic nanoparticles. Gold nanorods (Au NRs), in particular, can be welded together upon irradiation with femtosecond laser pulses, leading to dimers and trimers through the formation of necks between individual nanorods. We used electron tomography to determine the 3D (atomic) structure at such necks for representative welding geometries and to characterize the induced defects. The spatial distribution of localized surface plasmon modes for different welding configurations was assessed by electron energy loss spectroscopy. Additionally, we were able to directly compare the plasmon line width of single-crystalline and welded Au NRs with single defects at the same resonance energy, thus making a direct link between the structural and plasmonic properties. In this manner, we show that the occurrence of (single) defects results in significant plasmon broadening.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 17.1
Times cited: 25
DOI: 10.1021/acsnano.0c02610
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“A Benzocaine‐Induced Local Near‐Surface pH Effect: Influence on the Accuracy of Voltammetric Cocaine Detection”. de Jong M, Sleegers N, Schram J, Daems D, Florea A, De Wael K, Analysis &, Sensing , anse.202000012 (2020). http://doi.org/10.1002/anse.202000012
Abstract: This work reports on a local induced near-surface pH effect (pHS), due to the presence of one analyte, leading to an influence or even suppression of redox signals of a second analyte present in solution. This concept and its impact on voltammetric sensing is illustrated by focusing on the detection of cocaine in the presence of the common adulterant benzocaine. An in-depth study on the occurring interference mechanism and why it occurs for benzocaine specifically and not for other adulterants was performed through the use of multiple electrochemical strategies. It was concluded that the potential shift and loss of intensity of the squarewave voltammetric cocaine signal in the presence of benzocaine was caused by a local pHS effect. A cathodic pretreatment strategy was developed to nonetheless allow accurate cocaine detection. The gathered insights are useful to explain unidentified phenomena involving compounds with properties similar to benzocaine in voltammetric electroanalysis.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
DOI: 10.1002/anse.202000012
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“Plasma-Catalytic Ammonia Synthesis in a DBD Plasma: Role of Microdischarges and Their Afterglows”. van ‘t Veer K, Engelmann Y, Reniers F, Bogaerts A, Journal Of Physical Chemistry C 124, 22871 (2020). http://doi.org/10.1021/acs.jpcc.0c05110
Abstract: Plasma-catalytic ammonia synthesis is receiving ever increasing attention, especially in packed bed dielectric barrier discharge (DBD) reactors. The latter typically operate in the filamentary regime when used for gas conversion applications. While DBDs are in principle well understood and already applied in the industry, the incorporation of packing materials and catalytic surfaces considerably adds to the complexity of the plasma physics and chemistry governing the ammonia formation. We employ a plasma kinetics model to gain insights into the ammonia formation mechanisms, paying special attention to the role of filamentary microdischarges and their afterglows. During the microdischarges, the synthesized ammonia is actually decomposed, but the radicals created upon electron impact dissociation of N2 and H2 and the subsequent catalytic reactions cause a net ammonia gain in the afterglows of the microdischarges. Under our plasma conditions, electron impact dissociation of N2 in the gas phase followed by the adsorption of N atoms is identified as a rate-limiting step, instead of dissociative adsorption of N2 on the catalyst surface. Both elementary Eley−Rideal and Langmuir−Hinshelwood reaction steps can be found important in plasma-catalytic NH3 synthesis.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Movement Antwerp (MOVANT)
Impact Factor: 3.7
DOI: 10.1021/acs.jpcc.0c05110
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“On the Anti-Cancer Effect of Cold Atmospheric Plasma and the Possible Role of Catalase-Dependent Apoptotic Pathways”. Bengtson C, Bogaerts A, Cells 9, 2330 (2020). http://doi.org/10.3390/cells9102330
Abstract: Cold atmospheric plasma (CAP) is a promising new agent for (selective) cancer treatment, but the underlying cause of the anti-cancer effect of CAP is not well understood yet. Among different theories and observations, one theory in particular has been postulated in great detail and consists of a very complex network of reactions that are claimed to account for the anti-cancer effect of CAP. Here, the key concept is a reactivation of two specific apoptotic cell signaling pathways through catalase inactivation caused by CAP. Thus, it is postulated that the anti-cancer effect of CAP is due to its ability to inactivate catalase, either directly or indirectly. A theoretical investigation of the proposed theory, especially the role of catalase inactivation, can contribute to the understanding of the underlying cause of the anti-cancer effect of CAP. In the present study, we develop a mathematical model to analyze the proposed catalase-dependent anti-cancer effect of CAP. Our results show that a catalase-dependent reactivation of the two apoptotic pathways of interest is unlikely to contribute to the observed anti-cancer effect of CAP. Thus, we believe that other theories of the underlying cause should be considered and evaluated to gain knowledge about the principles of CAP-induced cancer cell death.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Times cited: 2
DOI: 10.3390/cells9102330
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“Plasma-driven catalysis: green ammonia synthesis with intermittent electricity”. Rouwenhorst KHR, Engelmann Y, van ‘t Veer K, Postma RS, Bogaerts A, Lefferts L, Green Chemistry 22, 6258 (2020). http://doi.org/10.1039/D0GC02058C
Abstract: Ammonia is one of the most produced chemicals, mainly synthesized from fossil fuels for fertilizer applications. Furthermore, ammonia may be one of the energy carriers of the future, when it is produced from renewable electricity. This has spurred research on alternative technologies for green ammonia production. Research on plasma-driven ammonia synthesis has recently gained traction in academic literature. In the current review, we summarize the literature on plasma-driven ammonia synthesis. We distinguish between mechanisms for ammonia synthesis in the presence of a plasma, with and without a catalyst, for different plasma conditions. Strategies for catalyst design are discussed, as well as the current understanding regarding the potential plasma-catalyst synergies as function of the plasma conditions and their implications on energy efficiency. Finally, we discuss the limitations in currently reported models and experiments, as an outlook for research opportunities for further unravelling the complexities of plasma-catalytic ammonia synthesis, in order to bridge the gap between the currently reported models and experimental results.
Keywords: A1 Journal article; Engineering sciences. Technology; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT); Movement Antwerp (MOVANT)
Impact Factor: 9.8
Times cited: 4
DOI: 10.1039/D0GC02058C
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“Arc plasma reactor modification for enhancing performance of dry reforming of methane”. Dinh DK, Trenchev G, Lee DH, Bogaerts A, Journal Of Co2 Utilization 42, 101352 (2020). http://doi.org/10.1016/j.jcou.2020.101352
Abstract: Arc plasma technology is gaining increasing interest for a variety of chemical reaction applications. In this study, we demonstrate how modifying the reactor geometry can significantly enhance the chemical reaction performance. Using dry reforming of methane as a model reaction, we studied different rotating arc reactors (conventional rotating arc reactor and nozzle-type rotating arc reactor) to evaluate the effect of attaching a downstream nozzle. The nozzle structure focuses the heat to a confined reaction volume, resulting in enhanced heat transfer from the arc into gas activation and reduced heat losses to the reactor walls. Compared to the conventional rotating arc reactor, this yields much higher CH4 and CO2 conversion (i.e., 74% and 49%, respectively, versus 40% and 28% in the conventional reactor, at 5 kJ/L) as well as energy efficiency (i.e., 53% versus 36%). The different performance in both reactors was explained by both experiments (measurements of temperature and oscillogram of current and voltage) and numerical modelling of the gas flow dynamics, heat transfer and fluid plasma of the reactor chambers. The results provide important insights for design optimization of arc plasma reactors for various chemical reactions.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 7.7
DOI: 10.1016/j.jcou.2020.101352
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“Ligand-Mode Directed Selectivity in Cu–Ag Core–Shell Based Gas Diffusion Electrodes for CO2Electroreduction”. Irtem E, Arenas Esteban D, Duarte M, Choukroun D, Lee S, Ibáñez M, Bals S, Breugelmans T, Acs Catalysis , 13468 (2020). http://doi.org/10.1021/acscatal.0c03210
Abstract: Bimetallic nanoparticles with tailored size and specific composition have shown promise as stable and selective catalysts for electrochemical reduction of CO2 (CO2R) in batch systems. Yet, limited effort was devoted to understand the effect of ligand coverage and postsynthesis treatments on CO2 reduction, especially under industrially applicable conditions, such as at high currents (>100 mA/cm2) using gas diffusion electrodes (GDE) and flow reactors. In this work, Cu–Ag core–shell nanoparticles (11 ± 2 nm) were prepared with three different surface modes: (i) capped with oleylamine, (ii) capped with monoisopropylamine, and (iii) surfactant free with a reducing borohydride agent; Cu–Ag (OAm), Cu–Ag (MIPA), and Cu–Ag (NaBH4), respectively. The ligand exchange and removal was evidenced by infrared spectroscopy (ATR-FTIR) analysis, whereas high-resolution scanning transmission electron microscopy (HAADF-STEM) showed their effect on the interparticle distance and nanoparticle rearrangement. Later on, we developed a process-on-substrate method to track these effects on CO2R. Cu–Ag (OAm) gave a lower on-set potential for hydrocarbon production, whereas Cu–Ag (MIPA) and Cu–Ag (NaBH4) promoted syngas production. The electrochemical impedance and surface area analysis on the well-controlled electrodes showed gradual increases in the electrical conductivity and active surface area after each surface treatment. We found that the increasing amount of the triple phase boundaries (the meeting point for the electron–electrolyte–CO2 reactant) affect the required electrode potential and eventually the C+2e̅/C2e̅ product ratio. This study highlights the importance of the electron transfer to those active sites affected by the capping agents—particularly on larger substrates that are crucial for their industrial application.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Applied Electrochemistry & Catalysis (ELCAT)
Impact Factor: 12.9
Times cited: 23
DOI: 10.1021/acscatal.0c03210
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“The effect of H2O on the vibrational populations of CO2in a CO2/H2O microwave plasma: a kinetic modelling investigation”. Verheyen C, Silva T, Guerra V, Bogaerts A, Plasma Sources Science &, Technology 29, 095009 (2020). http://doi.org/10.1088/1361-6595/aba1c8
Abstract: Plasma has been studied for several years to convert CO2 into value-added products. If CO2 could be converted in the presence of H2O as a cheap H-source for making syngas and oxygenates, it would mimic natural photosynthesis. However, CO2/H2O plasmas have not yet been extensively studied, not by experiments, and certainly not computationally. Therefore, we present here a kinetic modelling study to obtain a greater understanding of the vibrational kinetics of a CO2/H2O microwave plasma. For this purpose, we first created an electron impact cross section set for H2O, using a swarm-derived method. We added the new cross section set and CO2/H2O-related chemistry to a pure CO2 model. While it was expected that H2O addition mainly causes quenching of the CO2 asymmetric mode vibrational levels due to the additional CO2/H2O vibrational-translational relaxation, our model shows that the modifications in the vibrational kinetics are mainly induced by the strong electron dissociative attachment to H2O molecules, causing a reduction in electron density, and the corresponding changes in the input of energy into the CO2 vibrational levels by electron impact processes.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 3.8
DOI: 10.1088/1361-6595/aba1c8
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“Identifying Electrochemical Fingerprints of Ketamine with Voltammetry and Liquid Chromatography–Mass Spectrometry for Its Detection in Seized Samples”. Schram J, Parrilla M, Sleegers N, Samyn N, Bijvoets SM, Heerschop MWJ, van Nuijs ALN, De Wael K, Analytical Chemistry 92, 13485 (2020). http://doi.org/10.1021/acs.analchem.0c02810
Abstract: Herein, a straightforward electrochemical approach for the determination of ketamine in street samples and seizures is presented by employing screen-printed electrodes (SPE). Square wave voltammetry (SWV) is used to study the electrochemical behavior of the illicit drug, thus profiling the different oxidation states of the substance at different pHs. Besides, the oxidation pathway of ketamine on SPE is investigated for the first time with liquid chromatography–high-resolution mass spectrometry. Under the optimized conditions, the calibration curve of ketamine at buffer solution (pH 12) exhibits a sensitivity of 8.2 μA μM–1, a linear relationship between 50 and 2500 μM with excellent reproducibility (RSD = 2.2%, at 500 μM, n = 7), and a limit of detection (LOD) of 11.7 μM. Subsequently, binary mixtures of ketamine with adulterants and illicit drugs are analyzed with SWV to investigate the electrochemical fingerprint. Moreover, the profile overlapping between different substances is addressed by the introduction of an electrode pretreatment and the integration of a tailor-made script for data treatment. Finally, the approach is tested on street samples from forensic seizures. Overall, this system allows for the on-site identification of ketamine by law enforcement agents in an easy-to-use and rapid manner on cargos and seizures, thereby disrupting the distribution channel and avoiding the illicit drug reaching the end-user.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation); Toxicological Centre
Impact Factor: 7.4
DOI: 10.1021/acs.analchem.0c02810
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“Wearable Electrochemical Sensors for the Monitoring and Screening of Drugs”. Teymourian H, Parrilla M, Sempionatto JR, Montiel NF, Barfidokht A, Van Echelpoel R, De Wael K, Wang J, Acs Sensors 5, 2679 (2020). http://doi.org/10.1021/acssensors.0c01318
Abstract: Wearable electrochemical sensors capable of noninvasive monitoring of chemical markers represent a rapidly emerging digital-health technology. Recent advances toward wearable continuous glucose monitoring (CGM) systems have ignited tremendous interest in expanding such sensor technology to other important fields. This article reviews for the first time wearable electrochemical sensors for monitoring therapeutic drugs and drugs of abuse. This rapidly emerging class of drug-sensing wearable devices addresses the growing demand for personalized medicine, toward improved therapeutic outcomes while minimizing the side effects of drugs and the related medical expenses. Continuous, noninvasive monitoring of therapeutic drugs within bodily fluids empowers clinicians and patients to correlate the pharmacokinetic properties with optimal outcomes by realizing patient-specific dose regulation and tracking dynamic changes in pharmacokinetics behavior while assuring the medication adherence of patients. Furthermore, wearable electrochemical drug monitoring devices can also serve as powerful screening tools in the hands of law enforcement agents to combat drug trafficking and support on-site forensic investigations. The review covers various wearable form factors developed for noninvasive monitoring of therapeutic drugs in different body fluids and toward on-site screening of drugs of abuse. The future prospects of such wearable drug monitoring devices are presented with the ultimate goals of introducing accurate real-time drug monitoring protocols and autonomous closed-loop platforms toward precise dose regulation and optimal therapeutic outcomes. Finally, current unmet challenges and existing gaps are discussed for motivating future technological innovations regarding personalized therapy. The current pace of developments and the tremendous market opportunities for such wearable drug monitoring platforms are expected to drive intense future research and
commercialization efforts.
Keywords: A1 Journal article; Engineering sciences. Technology; AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 8.9
DOI: 10.1021/acssensors.0c01318
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“Effect of plasma-induced oxidative stress on the glycolysis pathway of Escherichia coli”. Ranjbar S, Shahmansouri M, Attri P, Bogaerts A, Computers In Biology And Medicine 127, 104064 (2020). http://doi.org/10.1016/j.compbiomed.2020.104064
Abstract: Antibiotic resistance is one of the world’s most urgent public health problems. Due to its antibacterial properties, cold atmospheric plasma (CAP) may serve as an alternative method to antibiotics. It is claimed that oxidative stress caused by CAP is the main reason of bacteria inactivation. In this work, we computationally investigated the effect of plasma-induced oxidation on various glycolysis metabolites, by monitoring the production of the biomass. We observed that in addition to the significant reduction in biomass production, the rate of some reactions has increased. These reactions produce anti-oxidant products, showing the bacterial defense mechanism to escape the oxidative damage. Nevertheless, the simulations show that the plasma-induced oxidation effect is much stronger than the defense mechanism, causing killing of the bacteria.
Keywords: A1 Journal article; Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 7.7
DOI: 10.1016/j.compbiomed.2020.104064
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