Scientific publications

The statistical anionic copolymerisation of the biobased monomer β-myrcene with styrene in cyclohexane was investigated via in situ near-infrared (NIR) spectroscopy, focusing on the influence of the modifiers (i.e., Lewis bases) tetrahydrofuran (THF) and 2,2-di(2-tetrahydrofuryl)propane (DTHFP) on the reactivity ratios. With increasing [modifier]/[Li] ratio, the reactivity ratios in the system myrcene/styrene are adjustable from rS ≪ rMyr via rS ≈ rMyr to rS ≫ rMyr. The bidentate modifier DTHFP affects the reactivity ratios much more than THF: minute amounts only (0.35 equivalent relative to Li) are required to randomize the copolymer, and one equivalent to invert the reactivity ratios. Using these reactivity ratios, copolymer composition profiles are obtained, which upon increasing the modifier concentration vary from tapered, block-like copolymers to random to inversely tapered copolymers. 1H-NMR spectroscopy was used to determine the microstructure of the myrcene units in the copolymers. With increasing [modifier]/[Li] ratio, the content of 1,4-units decreases and the content of 3,4- and 1,2-units increases. DTHFP as a modifier minimizes the content of 1,2-units. The glass transition temperatures also depend on the [modifier]/[Li] ratio, but less strongly than in the copolymer poly(styrene-co-isoprene). Although all copolymers have the same composition (33%mol myrcene, corresponding to 39.6%weight and 45%vol), very similar molecular weights (about 90 kg mol−1) and low dispersities (1.06 to 1.10), different morphologies could be obtained. Lamellar, cylindrical and gyroid structures were identified by TEM and SAXS measurements. The mechanical properties vary in a wide range from hard and brittle to soft and flexible. The gyroid structure showed the highest Young's modulus and no viscoelastic deformation.

Abstract A one-pot approach for the preparation of diblock copolymers consisting of polystyrene and polymyrcene blocks is described via a temperature-induced block copolymer (BCP) formation strategy. A monomer mixture of styrene and myrcene is employed. The unreactive nature of myrcene in a polar solvent (tetrahydrofuran) at −78 °C enables the sole formation of active polystyrene macroinitiators, while an increase of the temperature (−38 °C to room temperature) leads to poly(styrene-block-myrcene) formation due to polymerization of myrcene. Well-defined BCPs featuring molar masses in the range of 44–117.2 kg mol−1 with dispersities, Ð, of 1.09–1.21, and polymyrcene volume fractions of 30–64% are accessible. Matrix assisted laser desorption ionization-time of flight mass spectrometry measurements reveal the temperature-controlled polymyrcene block formation, while both transmission electron microscopy and small-angle X-ray scattering measurements prove the presence of clearly microphase-separated, long range-ordered domains in the block copolymers. The temperature-controlled one-pot anionic block copolymerization approach may be general for other terpene-diene monomers.

One of the major environmental problems is a global metal contamination. Heavy metals are nonbiodegradable and tend to accumulate in living organisms. Therefore, searching for biocompatible materials with enhanced sorption capabilities for selective removal of toxic elements from complex environments, low cost, ease of operation, and large available quantities that meet all requirements of the Green Chemistry concept is a current engineering and analytical task. We present a comprehensive study toward construction of an advanced biomembrane-based technology for recovery of several heavy metals and ruthenium by microdimensional alginate scaffolds. The chosen design of alginate scaffolds and their operational conditions were monitored during removal of Cd(II), Co(II), Pb(II), As(III), and Ru(III) in modeled aqueous solutions, cell culture medium, and in the presence of A549 lung cells by a tandem of biological (live/dead cell test), physical nanoanalytical (TEM/EDX, SEM/EDX), and chemical (FT-IR, HR-ICP-MS) assays. More precisely, the impact of certain experimental conditions, viz., medium acidity and matrix effects on sorption capacity of the above-mentioned elements, was investigated in detail. Remarkably, a different attachment behavior during adsorption of chosen elements by alginate scaffolds was observed. In addition, we revealed an essential concentration dependent effect of loaded heavy metals and ruthenium on cultivated cells. The obtained data allow us to gain a deeper insight into the interactions occurring in the studied biomaterial-inorganic system. Moreover, the obtained dependencies can be widely used for the development of alginate-based membrane technology employed for the protection of environmental and biological samples from the toxic pollutants.

During infection, inflammation is an important contributor to tissue regeneration and healing, but it may also negatively affect these processes should chronic overstimulation take place. Similar issues arise in chronic inflammatory gastrointestinal diseases such as inflammatory bowel diseases or celiac disease, which show increasing incidences worldwide. For these dispositions, probiotic microorganisms, including lactobacilli, are studied as an adjuvant therapy to counterbalance gut dysbiosis. However, not all who are affected can benefit from the probiotic treatment, as immunosuppressed or hospitalized patients can suffer from bacteremia or sepsis when living microorganisms are administered. A promising alternative is the treatment with bacteria-derived membrane vesicles that confer similar beneficial effects as the progenitor strains themselves. Membrane vesicles from lactobacilli have shown anti-inflammatory therapeutic effects, but it remains unclear whether the stimulation of probiotics induces vesicles that are more efficient. Here, the influence of culture conditions on the anti-inflammatory characteristics of Lactobacillus membrane vesicles was investigated. We reveal that the culture conditions of two Lactobacillus strains, namely, L. casei and L. plantarum, can be optimized to increase the anti-inflammatory effect of their vesicles. Five different cultivation conditions were tested, including pH manipulation, agitation rate, and oxygen supply, and the produced membrane vesicles were characterized physico-chemically regarding size, yield, and zeta potential. We furthermore analyzed the anti-inflammatory effect of the purified vesicles in macrophage inflammation models. Compared to standard cultivation conditions, vesicles obtained from L. casei cultured at pH 6.5 and agitation induced the strongest interleukin-10 release and tumor necrosis factor-α reduction. For L. plantarum, medium adjusted to pH 5 had the most pronounced effect on the anti-inflammatory activity of their vesicles. Our results reveal that the anti-inflammatory effect of probiotic vesicles may be potentiated by expanding different cultivation conditions for lactobacilli. This study creates an important base for the utilization of probiotic membrane vesicles to treat inflammation.

Pulmonary delivery of nanocarriers for novel antimycobacterial compounds is challenging because the aerodynamic properties of nanomaterials are sub-optimal for such purposes. Here, we report the development of dry powder formulations for nanocarriers containing benzothiazinone 043 (BTZ) or levofloxacin (LVX), respectively. The intricacy is to generate dry powder aerosols with adequate aerodynamic properties while maintaining both nanostructural integrity and compound activity until reaching the deeper lung compartments. Microparticles (MPs) were prepared using vibrating mesh spray drying with lactose and leucine as approved excipients for oral inhalation drug products. MP morphologies and sizes were measured using various biophysical techniques including determination of geometric and aerodynamic mean sizes, X-ray diffraction, and confocal and focused ion beam scanning electron microscopy. Differences in the nanocarriers’ characteristics influenced the MPs’ sizes and shapes, their aerodynamic properties, and, hence, also the fraction available for lung deposition. Spay-dried powders of a BTZ nanosuspension, BTZ-loaded silica nanoparticles (NPs), and LVX-loaded liposomes showed promising respirable fractions, in contrast to zirconyl hydrogen phosphate nanocontainers. While the colloidal stability of silica NPs was improved after spray drying, MPs encapsulating either BTZ nanosuspensions or LVX-loaded liposomes showed the highest respirable fractions and active pharmaceutical ingredient loads. Importantly, for the BTZ nanosuspension, biocompatibility and in vitro uptake by a macrophage model cell line were improved even further after spray drying.

This work introduces the facile and scalable two-step synthesis of Ti 2 Nb 10 O 29 (TNO)/carbon hybrid material as a promising anode for lithium-ion batteries (LIBs). The first step uses a mechanically-induced self-sustaining reaction via ball-milling at room temperature to produce titanium niobium carbide with a stoichiometric ratio of Ti and Nb of 1 to 5. The second step involves the oxidation of as-synthesized titanium niobium carbide to produce TNO. Synthetic air yields fully oxidized TNO, while annealing in CO 2 results in TNO/carbon hybrids. The electrochemical performance for the hybrid and non-hybrid electrodes was surveyed for a narrow potential window (1.0-2.5 V vs. Li/Li + ) and a large potential window (0.05-2.5 V vs. Li/Li + ). The best hybrid material displayed a specific capacity of 350 mAh/g at a rate of 0.01 A/g (144 mAh/g at 1 A/g) in the large potential window regime. The electrochemical performance of hybrid materials is superior compared to non-hybrid materials for operation within the large potential window. Due to the advantage of carbon in hybrid material, the rate handling is faster than that of the non-hybrid one. The hybrid materials display robust cycling stability and maintain ca. 70% of their initial capacities after 500 cycles. In contrast, only ca. 26% of the initial capacity is maintained after the first 40 cycles for non-hybrid materials. We also applied our hybrid material as an anode in a full-cell lithium-ion battery by coupling it with commercial LiMn 2 O 4 .

This work presents the synthesis of MoO2/MoS2 core/shell nanoparticles within a carbon nanotube network and their detailed electron microscopy investigation in up to three dimensions. The triple-hybrid core/shell material was prepared by atomic layer deposition of molybdenum oxide onto carbon nanotube networks, followed by annealing in a sulfur-containing gas atmosphere. High-resolution transmission electron microscopy together with electron diffraction, supported by chemical analysis via energy dispersive X-ray and electron energy loss spectroscopy, gave proof of a MoO2 core covered by few layers of a MoS2 shell within an entangled network of carbon nanotubes. To gain further insights into this complex material, the analysis was completed with 3D electron tomography. By using Z-contrast imaging, distinct reconstruction of core and shell material was possible, enabling the analysis of the 3D structure of the material. These investigations showed imperfections in the nanoparticles which can impact material performance, i.e. for faradaic charge storage or electrocatalysis.

Owing to MXenes’ tunable mechanical properties induced by their structural and chemical diversity, MXenes are believed to compete with state-of-the-art 2D nanomaterials such as graphene regarding their tribological performance. Their nanolaminate structure offers weak interlayer interactions and an easy-to-shear ability to render them excellent candidates for solid lubrication. However, the acting friction and wear mechanisms are yet to be explored. To elucidate these mechanisms, 100-nm-thick homogeneous multilayer Ti3C2Tx coatings are deposited on technologically relevant stainless steel by electrospraying. Using ball-on-disk tribometry (Si3N4 counterbody) with acting contact pressures of about 300 MPa, their long-term friction and wear performance under dry conditions are studied. MXene-coated specimens demonstrate a 6-fold friction reduction and an ultralow wear rate (4 × 10–9 mm3 N–1 m–1) over 100 000 sliding cycles, outperforming state-of-the-art 2D nanomaterials by at least 200% regarding their wear life. High-resolution characterization verified the formation of a beneficial tribolayer consisting of thermally/mechanically degraded MXenes and amorphous/nanocrystalline iron oxides. The transfer of this tribolayer to the counterbody transforms the initial steel/Si3N4 contact to tribolayer/tribolayer contact with low shear resistance. MXene pileups at the wear track’s reversal points continuously supply the tribological contact with fresh, lubricious nanosheets, thus enabling an ultra-wear-resistant and low-friction performance.

Abstract Owing to high electrical conductivity and ability to reversibly host a variety of inserted ions, 2D metallic molybdenum disulfide (1T-MoS2) has demonstrated promising energy storage performance when used as a supercapacitor electrode. However, its charge storage mechanism is still not fully understood, in particular, how the interlayer spacing of 1T-MoS2 would affect its capacitive performance. In this work, molecular dynamics simulations of 1T-MoS2 with interlayer spacing ranging from 0.615 nm to 1.615 nm have been performed to investigate the resulting charge storage capacity in ionic liquids. Simulations reveal a camel-like capacitance-potential relation, and MoS2 with an interlayer spacing of 1.115 nm has the highest volumetric and gravimetric capacitance of 118 F cm-3 and 42 F g-1, respectively. Although ions in MoS2 with an interlayer spacing of 1.115 nm diffuse much faster than with interlayer spacings of 1.365 nm and 1.615 nm, the MoS2 with larger interlayer spacing has a much faster charging process. Our analyses reveal that the ion number density and its charging speed, as well as ion motion paths, have significant impacts on the charging response. This work helps to understand how the interlayer spacing affects the interlayer ion structures and the capacitive performance of MoS2, which is important for revealing the charge storage mechanism and designing MoS2 supercapacitor.