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- ItemStructural stability, electronic, optical, and thermoelectric properties of layered perovskite Bi2LaO4I(London : RSC Publishing, 2022) Joshi, Radha K.; Bhandari, Shalika R.; Ghimire, Madhav PrasadLayered perovskites are an interesting class of materials due to their possible applications in microelectronics and optoelectronics. Here, by means of density functional theory calculations, we investigated the structural, elastic, electronic, optical, and thermoelectric properties of the layered perovskite Bi2LaO4I within the parametrization of the standard generalized gradient approximation (GGA). The transport coefficients were evaluated by adopting Boltzmann semi-classical theory and a collision time approach. The calculated elastic constants were found to satisfy the Born criteria, indicating that Bi2LaO4I is mechanically stable. Taking into account spin-orbit coupling (SOC), the material was found to be a non-magnetic insulator, with an energy bandgap of 0.82 eV (within GGA+SOC), and 1.85 eV (within GGA+mBJ+SOC). The optical-property calculations showed this material to be optically active in the visible and ultraviolet regions, and that it may be a candidate for use in optoelectronic devices. Furthermore, this material is predicted to be a potential candidate for use in thermoelectric devices due to its large value of power factor, ranging from 2811 to 7326 μW m−1 K−2, corresponding to a temperature range of 300 K to 800 K.
- ItemCopolymerization of CO2 and epoxides mediated by zinc organyls(London : RSC Publishing, 2018) Wulf, Christoph; Doering, Ulrike; Werner, ThomasHerein we report the copolymerization of CHO with CO2 in the presence of various zinc compounds R2Zn (R = Et, Bu, iPr, Cy and Ph). Several zinc organyls proved to be efficient catalysts for this reaction in the absence of water and co-catalyst. Notably, readily available Bu2Zn reached a TON up to 269 and an initial TOF up to 91 h-1. The effect of various parameters on the reaction outcome has been investigated. Poly(ether)carbonates with molecular weights up to 79.3 kg mol-1 and a CO2 content of up to 97% were obtained. Under standard reaction conditions (100 °C, 2.0 MPa, 16 h) the influence of commonly employed co-catalysts such as PPNCl and TBAB has been investigated in the presence of Et2Zn (0.5 mol%). The reaction of other epoxides (e.g. propylene and styrene oxide) under these conditions led to no significant conversion or to the formation of the respective cyclic carbonate as the main product.
- ItemComplex calcium carbonate/polymer microparticles as carriers for aminoglycoside antibiotics(London : RSC Publishing, 2018) Racovita, Stefania; Vasiliu, Ana-Lavinia; Bele, Adrian; Schwarz, Dana; Steinbach, Christine; Boldt, Regine; Schwarz, Simona; Mihai, MarcelaComposite microparticles of CaCO3 and two pectin samples (which differ by the functional group ratio) or corresponding nonstoichiometric polyelectrolyte complexes with different molar ratios (0.5, 0.9 and 1.2) are obtained, characterized and tested for loading and release of streptomycin and kanamycin sulphate. The synthesized carriers were characterized before and after drug loading in terms of morphology (by SEM using secondary electron and energy selective backscattered electron detectors), porosity (by water sorption isotherms) and elemental composition (by elemental mapping using energy dispersive X-ray and FTIR spectroscopy). The kinetics of the release mechanism from the microparticles was investigated using Higuchi and Korsmeyer-Peppas mathematical models.
- ItemA novel characterisation approach to reveal the mechano-chemical effects of oxidation and dynamic distension on polypropylene surgical mesh(London : RSC Publishing, 2021) Farr, Nicholas T. H.; Roman, Sabiniano; Schäfer, Jan; Quade, Antje; Lester, Daniel; Hearnden, Vanessa; MacNeil, Sheila; Rodenburg, CorneliaPolypropylene (PP) surgical mesh, used successfully for the surgical repair of abdominal hernias, is associated with serious clinical complications when used in the pelvic floor for repair of stress urinary incontinence or support of pelvic organ prolapse. While manufacturers claim that the material is inert and non-degradable, there is a growing body of evidence that asserts PP fibres are subject to oxidative damage and indeed explanted material from patients suffering with clinical complications has shown some evidence of fibre cracking and oxidation. It has been proposed that a pathological cellular response to the surgical mesh contributes to the medical complications; however, the mechanisms that trigger the specific host response against the material are not well understood. Specifically, this study was constructed to investigate the mechano-chemical effects of oxidation and dynamic distension on polypropylene surgical mesh. To do this we used a novel advanced spectroscopical characterisation technique, secondary electron hyperspectral imaging (SEHI), which is based on the collection of secondary electron emission spectra in a scanning electron microscope (SEM) to reveal mechanical-chemical reactions within PP meshes. This journal is
- ItemKinetic investigation of para-nitrophenol reduction with photodeposited platinum nanoparticles onto tunicate cellulose(London : RSC Publishing, 2022) Thiel, T.A.; Zhang, X.; Radhakrishnan, B.; van de Krol, R.; Abdi, F.F.; Schroeter, M.; Schomäcker, R.; Schwarze, M.Photodeposition is a specific method for depositing metallic co-catalysts onto photocatalysts and was applied for immobilizing platinum nanoparticles onto cellulose, a photocatalytically inactive biopolymer. The obtained Pt@cellulose catalysts show narrow and well-dispersed nanoparticles with average sizes between 2 and 5 nm, whereby loading, size and distribution depend on the preparation conditions. The catalysts were investigated for the hydrogenation of para-nitrophenol via transfer hydrogenation using sodium borohydride as the hydrogen source, and the reaction rate constant was determined using the pseudo-first-order reaction rate law. The Pt@cellulose catalysts are catalytically active with rate constant values k from 0.09 × 10−3 to 0.43 × 10−3 min−1, which were higher than the rate constant of a commercial Pt@Al2O3 catalyst (k = 0.09 × 10−3 min−1). Additionally, the Pt@cellulose catalyst can be used for electrochemical hydrogenation of para-nitrophenol where the hydrogen is electrocatalytically formed. The electrochemical hydrogenation is faster compared to the transfer hydrogenation (k = 0.11 min−1).
- ItemBiofunctionalized zinc peroxide (ZnO2) nanoparticles as active oxygen sources and antibacterial agents(London : RSC Publishing, 2017) Bergs, Christian; Brück, Lisa; Rosencrantz, Ruben R.; Conrads, Georg; Elling, Lothar; Pich, AndrijOxygen is one of the most important substances for physiological reactions and metabolisms in biological systems. Through the tailored design of oxygen-releasing materials it might be possible to control different biological processes. In this work we synthesized for the first time zinc peroxide nanoparticles with controlled sizes and biofunctionalized surfaces using a one-step reaction procedure. The zinc peroxide nanoparticles were obtained with tunable sizes (between 4.0 ± 1.2 nm and 9.4 ± 5.2 nm) and were decorated with glucose 1-phosphate (Glc-1P). The specific interaction of the phosphate function of Glc-1P with the nanoparticle surface was monitored by solid state 31P-NMR and zeta-potential measurements. Furthermore, using fluorescence measurements we demonstrated that anchored glucose molecules on the nanoparticle surface are accessible for specific interactions with lectins. It could be shown that these interactions strongly depend on the amount of Glc-1P attached to the nanoparticle surface. Additionally it was demonstrated that the oxygen release from biofunctionalized zinc peroxide nanoparticles could be tuned according to the chemical composition of the nanoparticles and the pH of the aqueous solution. The antibacterial efficiency of the synthesized nanoparticles against Enterococcus faecalis, Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Prevotella intermedia was evaluated by determination of minimal bactericidal concentration (MIC).
- ItemMulti-walled carbon nanotube-based composite materials as catalyst support for water–gas shift and hydroformylation reactions(London : RSC Publishing, 2019) Wolf, Patrick; Logemann, Morten; Schörner, Markus; Keller, Laura; Haumann, Marco; Wessling, MatthiasIn times of depleting fossil fuel reserves, optimizing industrial catalytic reactions has become increasingly important. One possibility for optimization is the use of homogenous catalysts, which are advantageous over heterogeneous catalysts because of mild reaction conditions as well as higher selectivity and activity. A new emerging technology, supported ionic liquid phase (SILP), was developed to permanently immobilize homogeneous catalyst complexes for continuous processes. However, these SILP catalysts are unable to form freestanding supports by themselves. This study presents a new method to introduce the SILP system into a support made from multi-walled carbon nanotubes (MWCNT). In a first step, SILP catalysts were prepared for hydroformylation as well as low-temperature water–gas shift (WGS) reactions. These catalysts were integrated into freestanding microtubes formed from MWCNTs, with silica (for hydroformylation) or alumina particles (for WGS) incorporated. In hydroformylation, the activity increased significantly by around 400% when the pure MWCNT material was used as SILP support. An opposite trend was observed for WGS, where pure alumina particles exhibited the highest activity. A significant advantage of the MWCNT composite materials is the possibility to coat them with separation layers, which allows their application in membrane reactors for more efficient processes.
- ItemCorrection: Direct chemical vapor deposition synthesis of large area single-layer brominated grapheme (RSC Advances (2019) 9 (13527-13532) DOI: 10.1039/C9RA01152H)(London : RSC Publishing, 2019) Hasan, Maria; Meiou, Wang; Yulian, Liu; Ullah, Sami; Ta, Huy Q.; Zhao, Liang; Mendes, Rafael G.; Malik, Zahida P.; Ahmad, Nasir M.; Liu, Zhongfan; R¨ummeli, Mark H.Correction for ‘Direct chemical vapor deposition synthesis of large area single-layer brominated graphene’ by Maria Hasan et al., RSC Adv., 2019, 9, 13527–13532. In the Acknowledgements section, the attribution “the Czech Republic from ERDF “Institute of Environmental Technology – Excellent Research” (No. CZ.02.1.01/0.0/0.0/15_019/0000853), should read “the Czech Republic from ERDF OP RDE project No. CZ.02.1.01/0.0/0.0/16_019/0000853”. The Royal Society of Chemistry apologises for these errors and any consequent inconvenience to authors and readers.
- ItemSulfonated covalent triazine-based frameworks as catalysts for the hydrolysis of cellobiose to glucose(London : RSC Publishing, 2018) Artz, Jens; Delidovich, Irina; Pilaski, Moritz; Niemeier, Johannes; Kübber, Britta Maria; Rahimi, Khosrow; Palkovits, ReginaCovalent triazine-based frameworks (CTFs) were synthesized in large scale from various monomers. The materials were post-synthetically modified with acid functionalities via gas-phase sulfonation. Acid capacities of up to 0.83 mmol g−1 at sulfonation degrees of up to 10.7 mol% were achieved. Sulfonated CTFs exhibit high specific surface area and porosity as well as excellent thermal stability under aerobic conditions (>300 °C). Successful functionalization was verified investigating catalytic activity in the acid-catalyzed hydrolysis of cellobiose to glucose at 150 °C in H2O. Catalytic activity is mostly affected by porosity, indicating that mesoporosity is beneficial for hydrolysis of cellobiose. Like other sulfonated materials, S-CTFs show low stability under hydrothermal reaction conditions. Recycling of the catalyst is challenging and significant amounts of sulfur leached out of the materials. Nevertheless, gas-phase sulfonation opens a path to tailored solid acids for application in various reactions. S-CTFs form the basis for multi-functional catalysts, containing basic coordination sites for metal catalysts, tunable structural parameters and surface acidity within one sole system.
- ItemInterconnected electrocatalytic Pt-metal networks by plasma treatment of nanoparticle-peptide fibril assemblies(London : RSC Publishing, 2019) Bandak, J.; Petzold, J.; Hatahet, H.; Prager, A.; Kersting, B.; Elsner, Ch.; Abel, B.Noble metal catalysts possess outstanding catalytic behaviors in organic reactions, photocatalysis, electrocatalysis and many other applications. Peptide fibrils are used for the controllable nanostructuring of metal nanoparticles with specific sizes, shapes and high-surface area structures. The degradation of these fibrils with O2-plasma yields interconnected networks of nanoparticles, similar to metallic nanowires. Herein, platinum nanoparticles (Pt-NPs) were synthesized by reduction using VUV excimer radiation. The particle size was characterized by dynamic light scattering (DLS). Due to agglomeration, the metal nanoparticles were stabilized using poly(vinyl pyrrolidone) (PVP) and the same synthesis procedure. The influence of the polymer PVP molecular weight (Mwt), PVP concentration (Cp) and VUV irradiation time on platinum nanoparticle size was investigated. Small (2–3 nm) Pt-NPs are formed in the case of PVP with Mwt = 10 000 g mol−1. With increasing PVP Mwt, decreasing PVP concentration and shorter irradiation times, larger sized nanoparticles appear. The applicability of templated platinum nanoparticles, both the PVP-stabilized and non-stabilized Pt-NPs, immobilized via electrostatic interactions on the solid phase-synthesized aniline-GGAAKLVFF (AFP) peptide fibrils was investigated to serve as possible electrode material. The plasma treatment of the nanoparticle-fibril-assemblies was also studied as a novel technique. The Pt-NPs-AFP fibrils and the PVP-stabilized-Pt-NPs-AFP fibrils nanohybrids were employed to modify electrodes and then subjected to O2-plasma treatment. These O2-plasma treated/modified electrodes exhibited high electrocatalytic activities towards oxygen reduction in cyclic voltammetry measurements. Thus, the aforementioned nanocomposites hold great potential for polymer electrolyte fuel cells and other electrochemical applications in miniature devices and microfluidic chips.
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