“Immersion calorimetry as a tool to evaluate the catalytic performance of titanosilicate materials in the epoxidation of cyclohexene”. Vernimmen J, Guidotti M, Silvestre-Albero J, Jardim EO, Mertens M, Lebedev OI, Van Tendeloo G, Psaro R, Rodríguez-Reinoso F, Meynen V, Cool P, Langmuir: the ACS journal of surfaces and colloids 27, 3618 (2011). http://doi.org/10.1021/la104808v
Abstract: Different types of titanosilicates are synthesized, structurally characterized, and subsequently catalytically tested in the liquid-phase epoxidation of cyclohexene. The performance of three types of combined zeolitic/mesoporous materials is compared with that of widely studied Ti-grafted-MCM-41 molecular sieve and the TS-1 microporous titanosilicate. The catalytic test results are correlated with the structural characteristics of the different catalysts. Moreover, for the first time, immersion calorimetry with the same substrate molecule as in the catalytic test reaction is applied as an extra means to interpret the catalytic results. A good correlation between catalytic performance and immersion calorimetry results is found. This work points out that the combination of catalytic testing and immersion calorimetry can lead to important insights into the influence of the materials structural characteristics on catalysis. Moreover, the potential of using immersion calorimetry as a screening tool for catalysts in epoxidation reactions is shown.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.833
Times cited: 19
DOI: 10.1021/la104808v
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“Deposition of vanadium silicalite-1 nanoparticles on SBA-15 materials: structural and transport characteristics of SBA-VS-15”. Meynen V, Cool P, Vansant EF, Kortunov P, Grinberg F, Kärger J, Mertens M, Lebedev OI, Van Tendeloo G, Microporous and mesoporous materials 99, 14 (2007). http://doi.org/10.1016/j.micromeso.2006.08.029
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 23
DOI: 10.1016/j.micromeso.2006.08.029
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“Development of photocatalytic efficient Ti-based nanotubes and nanoribbons by conventional and microwave assisted synthesis strategies”. Ribbens S, Meynen V, Van Tendeloo G, Ke X, Mertens M, Maes BUW, Cool P, Vansant EF, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 114, 401 (2008). http://doi.org/10.1016/j.micromeso.2008.01.028
Abstract: Titanate nanotubes were prepared via a hydrothermal treatment of TiO2 powders (Riedel De Haen) in a basic solution. Morphology and structure of the prepared samples were characterized by high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), XRD, FT-Raman spectroscopy, nitrogen sorption and DSC. The photocatalytic activity was evaluated by photocatalytic oxidation of rhodamine 6G. Trititanate nanotubes (TTNT) with inner pore diameters between 4 and 4.2 nm and surface areas up till 360 m(2)/g could be synthesized. The synthesis route was modified by introduction of a calcination step, by applying a lower hydrothermal temperature and microwave irradiation in order to increase the photocatalytic activity of the porous photoactive nanotubular materials. Calcination and a softer hydrothermal treatment led to the formation of anatase without affecting the surface area and nanotubular shape of the samples. In this way, the photocatalytic activity of the original trititanate nanotubes could be significantly increased. By making use of microwave assisted synthesis, the photocatalytic activity call also be increased due to the presence of anatase. However, by applying microwave synthesis, a different structure was obtained, nanoribbons (NR) instead of nanotubcs, resulting in a decrease in surface area and porosity.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA); Organic synthesis (ORSY)
Impact Factor: 3.615
Times cited: 47
DOI: 10.1016/j.micromeso.2008.01.028
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“Formation of a combined micro- and mesoporous material using zeolite Beta nanoparticles”. van Oers CJ, Stevens WJJ, Bruijn E, Mertens M, Lebedev OI, Van Tendeloo G, Meynen V, Cool P, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 120, 29 (2009). http://doi.org/10.1016/j.micromeso.2008.08.056
Abstract: Composite micro- and mesoporous materials are synthesized using zeolite Beta nanoparticles without the need for a structure directing agent to form the mesopores. This leads to important ecological and economical advantages. The influence of the way of cooling the aged nanoparticles solution on the formation of the composite materials has been studied. The materials have been characterized towards porosity by N2-sorption, towards zeolitic properties by TGA, DRIFT, XRD and TEM, towards aluminium content by EPMA. All prepared structures possess zeolitic properties. However, the method of cooling down of the aged seeds leads to differences in the porosity and intensity of the zeolitic characteristics.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 42
DOI: 10.1016/j.micromeso.2008.08.056
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“Influence of the synthesis parameters of TiO2-SBA-15 materials on the adsorption and photodegradation of rhodamine-6G”. de Witte K, Busuioc AM, Meynen V, Mertens M, Bilba N, Van Tendeloo G, Cool P, Vansant EF, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 110, 100 (2008). http://doi.org/10.1016/j.micromeso.2007.09.035
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Electron microscopy for materials research (EMAT)
Impact Factor: 3.615
Times cited: 54
DOI: 10.1016/j.micromeso.2007.09.035
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“The merging of silica-surfactant microspheres under hydrothermal conditions”. Liu S, Lebedev OI, Mertens M, Meynen V, Cool P, Van Tendeloo G, Vansant EF, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 116, 141 (2008). http://doi.org/10.1016/j.micromeso.2008.03.034
Abstract: Post-synthesis hydrothermal treatments have been used to improve the quality of MCM-41 materials. In our latest work, merging of surfactant-containing silica microspheres during the hydrothermal treatments was observed. Mechanistic insights and the different stages that are involved in the merging process can be summarized as follows. First, the surfaces of the starting microspheres open up due to the dissolution of silica. Then the dissolved silica species provide mass source for the formation of particle necks connecting two neighboring microspheres. Gradually, surfaces of the starting microspheres are flattened to meet the needs of further growth of the necks. Finally, some chain-like highly-ordered mesoporous structures up to several micrometers are formed. The observed merging of the surfactant-containing microspheres is a re-assembling process, which is under the control of electrostatic force between the dissolved silica species and the surfactant cations. The occluded surfactant cations in the precursor spheres play important roles in the merging process.
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 5
DOI: 10.1016/j.micromeso.2008.03.034
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“Mesoporous material formed by acidic hydrothermal assembly of silicalite-1 precursor nanoparticles in the absence of meso-templates”. Stevens WJJ, Meynen V, Bruijn E, Lebedev OI, Van Tendeloo G, Cool P, Vansant EF, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 110, 77 (2008). http://doi.org/10.1016/j.micromeso.2007.09.007
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 21
DOI: 10.1016/j.micromeso.2007.09.007
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“Systematic evaluation of thermal and mechanical stability of different commercial and synthetic photocatalysts in relation to their photocatalytic activity”. Ribbens S, Beyers E, Schellens K, Mertens M, Ke X, Bals S, Van Tendeloo G, Meynen V, Cool P, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 156, 62 (2012). http://doi.org/10.1016/j.micromeso.2012.01.036
Abstract: The effect of thermal treatment and mechanical stress on the structural and photocatalytic properties of eight different (synthetic and commercial) photocatalysts has been thoroughly investigated. Different mesoporous Ti-based materials were prepared via surfactant based synthesis routes (e.g. Pluronic 123, CTMABr = Cetyltrimethylammonium bromide) or via template-free synthesis routes (e.g. trititanate nanotubes). Also, the stabilizing effect of the NaOH/NH4OH post-treatment on the templated mesoporous materials and their photocatalytic activity was investigated. Furthermore, the thermal and mechanical properties of commercially available titanium dioxides such as P25 Evonik® and Millenium PC500® were studied. The various photocatalysts were analyzed with N2-sorption, X-ray diffraction (XRD), high resolution transmission electron microscopy (HR-TEM), differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) to obtain information concerning the specific surface area, pore volume, crystal structure, morphology, phase transitions, etc. In general, results show that the NaOH post-treatment leads to an increased control of the crystallization process during calcination resulting in a higher thermal stability, but at the same time diminishes the photocatalytic activity. Mesoporous materials in which pre-synthesized nanoparticles are used as titania source have the best mechanical stability whereas the mechanical stability of the nanotubes is the most limited. At increased temperatures and pressures, the tested commercial titanium dioxides lose their superior photocatalytic activity caused by a decreased accessibility of the active sites. The observed changes in adsorption capacities and photocatalytic activities cannot be assigned to one single phenomenon. In this respect, it shows the need to define a general/standard method to compare different photocatalysts. Furthermore, it is shown that the photocatalytic properties do not necessarily deteriorate under thermal stress, but can be improved due to crystallization, even though the initial material is (partially) destroyed. It is shown that the usefulness of a specific type of photocatalyst strongly depends on the application and the temperature/pressure to which it needs to resist.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 8
DOI: 10.1016/j.micromeso.2012.01.036
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“Zeolite \beta nanoparticles based bimodal structures : mechanism and tuning of the porosity and zeolitic properties”. van Oers CJ, Kurttepeli M, Mertens M, Bals S, Meynen V, Cool P, Microporous and mesoporous materials: zeolites, clays, carbons and related materials 185, 204 (2014). http://doi.org/10.1016/j.micromeso.2013.11.021
Abstract: Despite great efforts in the research area of zeolite nanoparticles and their use in the synthesis of bimodal materials, still little is known about the impact of the synthesis conditions of the zeolite nanoparticles on its own characteristics, and on the properties and the formation mechanism of the final bimodal materials. A zeolite β nanoparticles solution is applied in a mesotemplate-free synthesis method, and the influence of the hydrothermal ageing temperature of the nanoparticles solution on both the zeolitic and porosity characteristics of the final bimodal material has been studied. Transmission electron microscopy in combination with 3-dimensional reconstructions obtained by electron tomography revealed that the zeolite β nanoparticles are connected by neck-like structures, thus creating a wormhole-like mesoporous material. Considering the zeolitic properties, a clear threshold is observed in the synthesis temperature series at 413 K. Below and at this threshold, the biporous materials show no apparent zeolitic characteristics, although these materials exhibit a more condensed and uniform SiOSi network in comparison to Al-MCF. Synthesis temperatures above the threshold lead to bimodal structures with defined zeolitic properties. Moreover, the dimensions of the nanoparticles are studied by TEM, revealing an increasing particle size with increasing temperature under the threshold of 413 K, which is in agreement with a sol-mechanism. This mechanism is disturbed after the threshold due to the start of the crystallisation process.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.615
Times cited: 10
DOI: 10.1016/j.micromeso.2013.11.021
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“The effect of the buffer solution on the adsorption and stability of horse heart myoglobin on commercial mesoporous titanium dioxide : a matter of the right choice”. Loreto S, Cuypers B, Brokken J, Van Doorslaer S, De Wael K, Meynen V, Physical chemistry, chemical physics 19, 13503 (2017). http://doi.org/10.1039/C6CP08585G
Abstract: Despite the numerous studies on the adsorption of different proteins onto mesoporous titanium dioxide and indications on the important role of buffer solutions in bioactivity, a systematic study on the impact of the buffer on the protein incorporation into porous substrates is still lacking. We here studied the interaction between a commercial mesoporous TiO2 and three of the most used buffers for protein incorporation, i.e. HEPES, Tris and phosphate buffer. In addition, this paper analyzes the adsorption of horse heart myoglobin (hhMb) onto commercial mesoporous TiO2 as a model system to test the influence of buffers on the protein incorporation behavior in mesoporous TiO2. N2 sorption analysis, FT-IR and TGA/DTG measurements were used to evaluate the interaction between the buffers and the TiO2 surface, and the effect of such an interaction on hhMb adsorption. Cyclic voltammetry (CV) and electron paramagnetic resonance (EPR) were used to detect changes in the microenvironment surrounding the heme. The three buffers show a completely different interaction with the TiO2 surface, which drastically affects the adsorption of myoglobin as well as its structure and electrochemical activity. Therefore, special attention is required while choosing the buffer medium to avoid misguided evaluation of protein adsorption on mesoporous TiO2.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.123
Times cited: 2
DOI: 10.1039/C6CP08585G
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“Effect of argon or helium on the CO2 conversion in a dielectric barrier discharge”. Ramakers M, Michielsen I, Aerts R, Meynen V, Bogaerts A, Plasma processes and polymers 12, 755 (2015). http://doi.org/10.1002/ppap.201400213
Abstract: This paper demonstrates that the CO2 conversion in a dielectric barrier discharge rises drastically upon addition of Ar or He, and the effect is more pronounced for Ar than for He. The effective CO2 conversion, on the other hand, drops upon addition of Ar or He, which is logical due to the lower CO2 content in the gas mixture, and the same is true for the energy efficiency, because a considerable fraction of the energy is then consumed into ionization/excitation of Ar or He atoms. The higher absolute CO2 conversion upon addition of Ar or He can be explained by studying in detail the Lissajous plots and the current profiles. The breakdown voltage is lower in the CO2/Ar and CO2/He mixtures, and the discharge gap is more filled with plasma, which enhances the possibility for CO2 conversion. The rates of electron impact excitationdissociation of CO2, estimated from the electron densities and mean electron energies, are indeed higher in the CO2/Ar and (to a lower extent) in the CO2/He mixtures, compared to the pure CO2 plasma. Moreover, charge transfer between Ar+ or Ar2+ ions and CO2, followed by electron-ion dissociative recombination of the CO2+ ions, might also contribute to, or even be dominant for the CO2 dissociation. All these effects can explain the higher CO2 conversion, especially upon addition of Ar, but also upon addition of He.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Plasma Lab for Applications in Sustainability and Medicine – Antwerp (PLASMANT)
Impact Factor: 2.846
Times cited: 63
DOI: 10.1002/ppap.201400213
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“Characterization and analysis of the adsorption immobilization mechanism of \beta-galactosidase on metal oxide powders”. Satyawali Y, Van Roy S, Roevens A, Meynen V, Mullens S, Jochems P, Doyen W, Cauwenberghs L, Dejonghe W, RSC advances 3, 24054 (2013). http://doi.org/10.1039/C3RA45107K
Abstract: Immobilization of the enzymes plays a vital role in enhancing their applicability in a wide range of applications, thus ensuring the use of sustainable enzymatic processes over the conventional chemical processes on an industrial scale. This study provides the background information for the selection and screening of inorganic metal oxide (MO) powders for their use as fillers in mixed matrix membranes for enzyme immobilization as the future aim. A total of 13 MOs, ranging in size from 0.01 μm to <5 μm, were tested for their performance as a support for enzyme (β-galactosidase) immobilization via adsorption. Alumina appeared to be the best performing MO with the amount and activity of the immobilized enzyme being 64 mg g−1 and up to 288 U g−1, respectively. The amount of immobilized enzyme on alumina (α-Al2O3 C and γ-Al2O3) was >3 times higher than ZrO2 (used as a reference MO in this study). Upon heat treatment at 900 °C, up to 15%, 52% and 42% decline was observed in the amount of immobilized enzyme in case of alumina metal oxides (MOs), ZrO2 and TiO2, respectively. The results suggested that both isoelectric point and surface area of the MO influence the immobilization. The most important observation in this study was that the bonding of the enzyme to the MO surface seems to be mediated by the bonding/interaction of the buffer to the enzyme.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); Sustainable Energy, Air and Water Technology (DuEL)
DOI: 10.1039/C3RA45107K
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“Enzymatic sensor for phenols based on titanium dioxide generating surface confined ROS after treatment with H2O2”. Rahemi V, Trashin S, Hafideddine Z, Meynen V, Van Doorslaer S, De Wael K, Sensors and actuators : B : chemical 283, 343 (2019). http://doi.org/10.1016/J.SNB.2018.12.039
Abstract: Titanium dioxide (TiO2) is a popular material as host matrix for enzymes. We now evidence that TiO2 can accumulate and retain reactive oxygen species after treatment by hydrogen peroxide (H2O2) and support redox cycling of a phenolic analyte between horseradish peroxidase (HRP) and an electrode. The proposed detection scheme is identical to that of second generation biosensors, but the measuring solution requires no dissolved H2O2. This significantly simplifies the analysis and overcomes issues related to H2O2 being present (or generated) in the solution. The modified electrodes showed rapid stabilization of the baseline, a low noise level, fast realization of a steady-state current response, and, in addition, improved sensitivity and limit of detection compared to the conventional approach, i.e. in the presence of H2O2 in the measuring solution. Hydroquinone, 4-aminophenol, and other phenolic compounds were successfully detected at sub-μM concentrations. Particularly, a linear response in the concentration range between 0.025 and 2 μM and LOD of 24 nM was demonstrated for 4-aminophenol. The proposed sensor design goes beyond the traditional concept with three sensors generations offering a new possibility for the development of enzymatic sensors based on peroxidases and the formation of ROS on titania after treatment with H2O2.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 5.401
Times cited: 1
DOI: 10.1016/J.SNB.2018.12.039
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“An adhesive conducting electrode material based on commercial mesoporous titanium dioxide as a support for Horseradish peroxidase for bioelectrochemical applications”. Rahemi V, Trashin S, Meynen V, De Wael K, Talanta : the international journal of pure and applied analytical chemistry 146, 689 (2016). http://doi.org/10.1016/J.TALANTA.2015.06.041
Abstract: An adhesive conducting electrode material containing of graphite, biocompatible ion exchange polymer nafion® and commercial mesoporous TiO2 impregnated with horseradish peroxidase (HRP) is prepared and characterized by amperometric, UVvis and N2 sorption methods. The factors influencing the performance of the resulting biosensor are studied in detail. The optimal electrode material consists of 45% graphite, 50% impregnated HRPTiO2 and 5% nafion®. The optimum conditions for H2O2 reduction are an applied potential of 0.3 V and 0.1 mM hydroquinone. Sensitivity and limit of detection in the optimum conditions are 1 A M−1 cm−2 and 1 µM correspondingly. The N2 sorption results show that the pore volume of TiO2 decreases sharply upon adsorption of HRP. The preparation process of the proposed enzyme electrode is straightforward and potentially can be used for preparation of carbon paste electrodes for bioelectrochemical detections.
Keywords: A1 Journal article; Laboratory of adsorption and catalysis (LADCA); AXES (Antwerp X-ray Analysis, Electrochemistry and Speciation)
Impact Factor: 4.162
Times cited: 7
DOI: 10.1016/J.TALANTA.2015.06.041
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“Aluminum incorporation into MCM-48 toward the creation of Brønsted acidity”. Collart O, Cool P, van der Voort P, Meynen V, Vansant EF, Houthoofd KJ, Grobet PJ, Lebedev OI, Van Tendeloo G, The journal of physical chemistry : B : condensed matter, materials, surfaces, interfaces and biophysical 108, 13905 (2004). http://doi.org/10.1021/jp049837x
Keywords: A1 Journal article; Electron microscopy for materials research (EMAT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 3.177
Times cited: 13
DOI: 10.1021/jp049837x
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“Mechanistic Insight into the Photocatalytic Working of Fluorinated Anatase {001} Nanosheets”. Kus M, Altantzis T, Vercauteren S, Caretti I, Leenaerts O, Batenburg KJ, Mertens M, Meynen V, Partoens B, Van Doorslaer S, Bals S, Cool P, The journal of physical chemistry: C : nanomaterials and interfaces 121, 26275 (2017). http://doi.org/10.1021/acs.jpcc.7b05586
Abstract: Anatase nanosheets with exposed {001} facets
have gained increasing interest for photocatalytic applications. To
fully understand the structure-to-activity relation, combined
experimental and computational methods have been exploited.
Anatase nanosheets were prepared under hydrothermal conditions
in the presence of fluorine ions. High resolution scanning
transmission electron microscopy was used to fully characterize
the synthesized material, confirming the TiO2 nanosheet
morphology. Moreover, the surface structure and composition
of a single nanosheet could be determined by annular bright-field
scanning transmission electron microscopy (ABF-STEM) and
STEM electron energy loss spectroscopy (STEM-EELS). The photocatalytic activity was tested for the decomposition of organic
dyes rhodamine 6G and methyl orange and compared to a reference TiO2 anatase sample. The anatase nanosheets with exposed
{001} facets revealed a significantly lower photocatalytic activity compared to the reference. In order to understand the
mechanism for the catalytic performance, and to investigate the role of the presence of F−, light-induced electron paramagnetic
resonance (EPR) experiments were performed. The EPR results are in agreement with TEM, proving the presence of Ti3+
species close to the surface of the sample and allowing the analysis of the photoinduced formation of paramagnetic species.
Further, ab initio calculations of the anisotropic effective mass of electrons and electron holes in anatase show a very high effective
mass of electrons in the [001] direction, having a negative impact on the mobility of electrons toward the {001} surface and thus
the photocatalysis. Finally, motivated by the experimental results that indicate the presence of fluorine atoms at the surface, we
performed ab initio calculations to determine the position of the band edges in anatase slabs with different terminations of the
{001} surface. The presence of fluorine atoms near the surface is shown to strongly shift down the band edges, which indicates
another reason why it can be expected that the prepared samples with a large amount of {001} surface, but with fluorine atoms
near the surface, show only a low photocatalytic activity.
Keywords: A1 Journal article; Engineering sciences. Technology; Electron microscopy for materials research (EMAT); Condensed Matter Theory (CMT); Laboratory of adsorption and catalysis (LADCA)
Impact Factor: 4.536
Times cited: 20
DOI: 10.1021/acs.jpcc.7b05586
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