The type and concentration of inoculum and substrate as well as the presence of oxygen impact the water kefir fermentation process

Eleven series of water kefir fermentation processes differing in the presence of oxygen and the type and concentration of inoculum and substrate, were followed as a function of time to quantify the impact of these parameters on the kinetics of this process via a modeling approach. Increasing concentrations of the water kefir grain inoculum increased the water kefir fermentation rate, so that the metabolic activity during water kefir fermentation was mainly associated with the grains. Water kefir liquor could also be used as an alternative means of inoculation, but the resulting fermentation process progressed slower than the one inoculated with water kefir grains, and the production of water kefir grain mass was absent. Substitution of sucrose with glucose and/or fructose reduced the water kefir grain growth, whereby glucose was fermented faster than fructose. Lacticaseibacillus paracasei (formerly known as Lactobacillus paracasei), Lentilactobacillus hilgardii (formerly known as Lactobacillus hilgardii), Liquorilactobacillus nagelii (formerly known as Lactobacillus nagelii), Saccharomyces cerevisiae, and Dekkera bruxellensis were the main microorganisms present. Acetic acid bacteria were present in low abundances under anaerobic conditions and only proliferated under aerobic conditions. Visualization of the water kefir grains through scanning electron microscopy revealed that the majority of the microorganisms was attached onto their surface. Lactic acid bacteria and yeasts were predominantly associated with the grains, whereas acetic acid bacteria were predominantly associated with the liquor

The influence of superabsorbent polymers and nanosilica on the hydration process and microstructure of cementitious mixtures

Superabsorbent polymers (SAPs) are known to mitigate the development of autogenous shrinkage in cementitious mixtures with a low water-to-cement ratio. Moreover, the addition of SAPs promotes the self-healing ability of cracks. A drawback of using SAPs lies in the formation of macropores when the polymers release their absorbed water, leading to a reduction of the mechanical properties. Therefore, a supplementary material was introduced together with SAPs, being nanosilica, in order to obtain an identical compressive strength with respect to the reference material without additives. The exact cause of the similar compressive behaviour lies in the modification of the hydration process and subsequent microstructural development by both SAPs and nanosilica. Within the present study, the effect of SAPs and nanosilica on the hydration progress and the hardened properties is assessed. By means of isothermal calorimetry, the hydration kinetics were monitored. Subsequently, the quantity of hydration products formed was determined by thermogravimetric analysis and scanning electron microscopy, revealing an increased amount of hydrates for both SAP and nanosilica blends. An assessment of the pore size distribution was made using mercury intrusion porosimetry and demonstrated the increased porosity for SAP mixtures. A correlation between microstructure and the compressive strength displayed its influence on the mechanical behaviour

Integrated cleanroom process for the vapor-phase deposition of large-area zeolitic imidazolate framework thin films

Robust and scalable thin-film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for the zeolitic imidazolate framework-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices

Molecular Layer Deposition of Zeolitic Imidazolate Framework‑8 Films [Dataset]

24 pages. -- Methods. -- Summary of some of the reported vapor-phase processes for the layer-by-layer deposition of MOFs6. -- Synchrotron GIXRD reciprocal space maps of direct ZIF-8 MLD show crystallinity even at a very low number of cycles. -- Vapor pressure determination of 2-methylimidazole (HmIM) via thermogravimetry: Knudsen effusion method. -- Direct ZIF-8 MLD linker exposure times. -- Direct ZIF-8 MLD films on Si are pinhole-free. -- AFM image of a MOF-CVD ZIF-8 “layer”, i.e., scattered crystallites. -- Photograph of a 200 mm wafer with 30 MLD ZIF-8 cycles and the corresponding 100-point ellipsometry thickness mapping. -- Film characterization of direct ZIF-8 MLD with a missing water pulse. -- Effect of no water pulses in direct ZIF-8 MLD. -- Direct ZIF-8 MLD with water completely or partially substituted by methanol. -- Humidified conditions HmIM post-deposition treatment of direct ZIF-8 MLD. -- HAXPES survey scans. -- HAXPES peak fitting. -- Study of aging effect due to exposure to atmospheric gasses. -- Direct ZIF-8 MLD on (100) oriented supercrystals. -- ZIF-67 crystals powder characterization. -- SEM images ZIF-67. -- Direct ZIF-8 MLD schematic representation of the protocol. -- Two-step ZIF-8 MLD schematic representation of the protocol. -- The optimized temperature gradient in the MOF-MLD reactor. -- MOF-MLD optimization of the temperature gradient. -- Ellipsometry of HmIM post-deposition treatment and activation in two-step ZIF-8 MLD. -- Ellipsometric porosimetry as a function of time. -- Supporting Information References.Vapor-phase film deposition of metal–organic frameworks (MOFs) would facilitate the integration of these materials into electronic devices. We studied the vapor-phase layer-by-layer deposition of zeolitic imidazolate framework 8 (ZIF-8) by consecutive, self-saturating reactions of diethyl zinc, water, and 2-methylimidazole on a substrate. Two approaches were compared: (1) Direct ZIF-8 “molecular layer deposition” (MLD), which enables a nanometer-resolution thickness control and employs only self-saturating reactions, resulting in smooth films that are crystalline as-deposited, and (2) two-step ZIF-8 MLD, in which crystallization occurs during a postdeposition treatment with additional linker vapor. The latter approach resulted in a reduced deposition time and an improved MOF quality, i.e., increased crystallinity and probe molecule uptake, although the smoothness and thickness control were partially lost. Both approaches were developed in a modified atomic layer deposition reactor to ensure cleanroom compatibility.Peer reviewe

Efficient long-range conduction in cable bacteria through nickel protein wires

Filamentous cable bacteria display long-range electron transport, generating electrical currents over centimeter distances through a highly ordered network of fibers embedded in their cell envelope. The conductivity of these periplasmic wires is exceptionally high for a biological material, but their chemical structure and underlying electron transport mechanism remain unresolved. Here, we combine high-resolution microscopy, spectroscopy, and chemical imaging on individual cable bacterium filaments to demonstrate that the periplasmic wires consist of a conductive protein core surrounded by an insulating protein shell layer. The core proteins contain a sulfur-ligated nickel cofactor, and conductivity decreases when nickel is oxidized or selectively removed. The involvement of nickel as the active metal in biological conduction is remarkable, and suggests a hitherto unknown form of electron transport that enables efficient conduction in centimeter-long protein structures

Electrochemical codeposition of copper-antimony and interactions with electrolyte additives : towards the use of electronic waste for sustainable copper electrometallurgy

The use of electronic waste or low grade materials as feedstock for the electrolytic production of copper is challenging because impurity metals such as Sb(III) are introduced in the electrolyte. In this work, the mechanisms that lead to antimony contamination in electrolytic copper are studied. Linear sweep voltammetry experiments indicate that the reduction of Sb(III) is kinetically slow in the absence of Cu(II). In the presence of Cu (II), however, reduction of Sb(III) can occur readily by the codeposition of Cu(II) and Sb(III) as demonstrated by chronoamperometry. The ToF-SIMS analyses confirmed the codeposition of antimony in the very first micrometer of the copper deposit, enabled by the nucleation overpotential for galvanostatic copper electrodeposition under conditions relevant for the commercial production of copper. Based on potentiostatic electrodeposition experiments, we suggest that a copper concentration of >40 g L-1 Cu(II) in Sb(III) containing electrolytes is beneficial to obtain high purity copper. Codeposition reactions were impacted by the presence of additives (thiourea, glue and chloride ions). In particular, the addition of 0.02 g L-1 chloride mitigated the codeposition of antimony (0.02 g L-1 Sb(III)) to produce grade A copper. For optimal removal of Sb(III) from bleed electrolytes, a molar ratio of ~3 Cu(II)/Sb(III) should be maintained (e.g. 0.3 g L-1 Cu(II) for a typical concentration of 0.2 g L-1 Sb(III))

Electrochemical Codeposition of Copper‑antimony and Interactions with Electrolyte Additives: towards the Use of Electronic Waste for Sustainable Copper Electrometallurgy

The use of electronic waste or low grade materials as feedstock for the electrolytic production of copper is challenging because impurity metals such as Sb(III) are introduced in the electrolyte. In this work, the mechanisms that lead to antimony contamination in electrolytic copper are studied. Linear sweep voltammetry experiments indicate that the reduction of Sb(III) is kinetically slow in the absence of Cu(II). In the presence of Cu(II), however, reduction of Sb(III) can occur readily by the codeposition of Cu(II) and Sb(III) as demonstrated by chronoamperometry. The ToF-SIMS analyses confirmed the codeposition of antimony in the very first micrometer of the copper deposit, enabled by the nucleation overpotential for galvanostatic copper electrodeposition under conditions relevant for the commercial production of copper. Based on potentiostatic electrodeposition experiments, we suggest that a copper concentration of ≥40 g L−1 Cu(II) in Sb(III) containing electrolytes is beneficial to obtain high purity copper. Codeposition reactions were impacted by the presence of additives (thiourea, glue and chloride ions). In particular, the addition of 0.02 g L−1 chloride mitigated the codeposition of antimony (0.02 g L−1 Sb(III)) to produce grade A copper. For optimal removal of Sb(III) from bleed electrolytes, a molar ratio of ~3 Cu(II)/Sb(III) should be maintained (e.g. 0.3 g L−1 Cu(II) for a typical concentration of 0.2 g L−1 Sb(III))