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Copper is a most widely used substrate for Li deposition and dissolution in lithium metal anodes, which are complicated by the formation of solid-electrolyte-interphases (SEIs) whose physical and chemical properties can affect Li deposition and dissolution significantly. However, initial Li nucleation and growth on bare Cu creates Li nuclei that only partially cover the Cu surface so that SEI formation could proceed not only on Li nuclei but also on the bare region of the Cu surface with different kinetics, which may affect the follow-up processes distinctively. In this paper, we employ in-situ atomic force microscopy (AFM) together with X-ray photoelectron spectroscopy (XPS) to investigate how SEIs formed on Cu surface, without Li participation, and on the surface of growing Li nuclei, with Li participation, affect the components and structures of the SEIs, and how the formation sequence of the two kinds of SEIs along with Li deposition affect subsequent dissolution and re-deposition processes in a pyrrolidinium-based ionic liquid electrolyte containing small amount of water. Nanoscale in-situ AFM observations show that sphere-like Li deposits may have differently conditioned SEI-shells, depending on whether Li nucleation is precedent with formation of the SEI on Cu. Models of integrated-SEI shells and segmented-SEI shells are proposed to respectively describe SEI shells formed on Li nuclei and the SEI shells sequentially-formed on Cu and then on Li nuclei. “Top-dissolution” are observed for both types of shelled Li deposits, but the integrated-SEI shells only show wrinkles which can be recovered upon Li re-deposition while the segmented-SEI shells are apparently top-opened due to mechanical stresses introduced at the junctions of the top regions and become “dead” SEIs which forces subsequent Li nucleation and growth in the interstice of the dead SEIs. Our work provides insights on the impact mechanism of SEIs on Li deposition and dissolution on foreign substrates, and reveals that SEIs could be more influential to Li dissolution and spatial integration of SEI shells on Li deposits is important to improving the reversibility of deposition and dissolution cycling.

Polymeric carbon nitrides (PCN) are sustainable, tunable, non-toxic and chemically stable materials that represent highly promising heterogeneous photocatalysts for light-driven hydrogen peroxide production via selective reduction of dioxygen. However, most of the studies on photocatalytic H2O2 production using PCN-based photocatalysts reported so far have used PCN powder suspensions and have been carried out in the presence of additional (sacrificial) electron donors, such as aliphatic or aromatic alcohols. Herein, we report the first multicomponent hybrid photocathode based on PCN that is capable of selective reduction of dioxygen to H2O2 under visible light irradiation (420 nm LED). A comparative analysis of various photocathode architectures is carried out using electronic absorption spectroscopy, surface photovoltage spectroscopy, open-circuit photopotential spectroscopy, and photocurrent measurements, including in-situ detection of formed H2O2 using microelectrodes. Notably, the ability of PCN-based photocathodes to catalyze the light-driven reduction of O2 to H2O2 in the absence of any additional electron donor is unambiguously demonstrated. Our study thus highlights the intrinsic nature of the photocatalytic activity of PCN in H2O2 production, and paves the way for the development of further PCN-based photocathodes in which PCN could be coupled with more effective light absorbers to increase the overall performance.

Polymeric carbon nitrides (PCN) are sustainable, tunable, non-toxic and chemically stable materials that represent highly promising heterogeneous photocatalysts for light-driven hydrogen peroxide production via selective reduction of dioxygen. However, most of the studies on photocatalytic H2O2 production using PCN-based photocatalysts reported so far have used PCN powder suspensions and have been carried out in the presence of additional (sacrificial) electron donors, such as aliphatic or aromatic alcohols. Herein, we report the first multicomponent hybrid photocathode based on PCN that is capable of selective reduction of dioxygen to H2O2 under visible light irradiation (420 nm LED). A comparative analysis of various photocathode architectures is carried out using electronic absorption spectroscopy, surface photovoltage spectroscopy, open-circuit photopotential spectroscopy, and photocurrent measurements, including in-situ detection of formed H2O2 using microelectrodes. Notably, the ability of PCN-based photocathodes to catalyze the light-driven reduction of O2 to H2O2 in the absence of any additional electron donor is unambiguously demonstrated. Our study thus highlights the intrinsic nature of the photocatalytic activity of PCN in H2O2 production, and paves the way for the development of further PCN-based photocathodes in which PCN could be coupled with more effective light absorbers to increase the overall performance.

Antibacterial polymer materials have gained interest due to their capability to inhibit or eradicate biofilms with greater efficiency in comparison with their monomeric counterparts. Among the antimicrobial and anti-biofouling polymers, catecholamine-based polymers — and in particular polydopamine — have been studied due to their favorable adhesion properties, which can be tuned by controlling the pH value. In this study, we used atomic force microscopy (AFM)–based spectroscopy to investigate the relation between the adhesion properties and surface charge density and the pH of electrochemically deposited polydopamine films presenting a dissociation constant of polydopamine of 6.3 ± 0.2 and a point of zero charge of 5.37 ± 0.06. Furthermore, using AFM and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), the influence of the surface charge density of polydopamine on bacterial adhesion and biofilm formation was investigated. It was shown that the adhesion of Escherichia coli at positively charged polydopamine is three times higher compared to a negatively charged polymer, and that the formation of biofilms is favored at positively charged polymers. Graphical abstract

We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn4 O4 )(V4 O13 )(OAc)3 ]3- . Simulated IR spectra show that V=O stretching vibrations in the 900-1000 cm-1 region shift consistently by about 20 cm-1 per oxidation equivalent. Multiple bands in the 1450-1550 cm-1 region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of MnIII atoms. Spectroelectrochemical measurements of the oxidation from [Mn 2III Mn 2IV ] to [Mn 4IV ] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy.

In spite of the enormous promise that polymeric carbon nitride (PCN) materials hold for various applications, the fabrication of high-quality, binder-free PCN films and electrodes has been a largely elusive goal to date. Here, we tackle this challenge by devising, for the first time, a water-based sol−gel approach that enables facile preparation of thin films based on poly(heptazine imide) (PHI), a polymer belonging to the PCN family. The sol−gel process capitalizes on the use of a water-soluble PHI precursor that allows formation of a non-covalent hydrogel. The hydrogel can be deposited on conductive substrates, resulting in formation of mechanically stable polymeric thin layers. The resulting photoanodes exhibit unprecedented photoelectrochemical (PEC) performance in alcohol reforming and highly selective (∼100 %) conversions with very high photocurrents (>0.25 mA cm−2 under 2 sun) down to, This work was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)–Projektnummer 364549901–TRR 234 [Projects B6, B7, C2, C4 and Z2] and BE 5102/5-1. C.N and A.T. acknowledge financial support of the DFG through the project TU 149/8-2 “Towards photo-active membranes for artificial photosynthesis” as well as the DFG through a research infrastructure grant INST 275/257-1 FUGG. S.G.G. acknowledges support by Spanish MINECO (MAT2016-78155-C2-1-R) and Gobierno del Principado de Asturias (GRUPIN-ID2018-170). L.d.S.G. acknowledges Juan de la Cierva Formación scholarship. I.K. acknowledges the support of the Alexander von Humboldt Foundation through the Humboldt Research Fellowship. Open access funding enabled and organized by Projekt DEAL.

Pit membranes in bordered pits of tracheary elements of angiosperm xylem represent primary cell walls that undergo structural and chemical modifications, not only during cell death but also during and after their role as safety valves for water transport between conduits. Cellulose microfibrils, which are typically grouped in aggregates with a diameter between 20 to 30 nm, make up their main component. While it is clear that pectins and hemicellulose are removed from immature pit membranes during hydrolysis, recent observations of amphiphilic lipids and proteins associated with pit membranes raise important questions about drought-induced embolism formation and spread via air-seeding from gas-filled conduits. Indeed, mechanisms behind air-seeding remain poorly understood, which is due in part to little attention paid to the three-dimensional structure of pit membranes in earlier studies. Based on perfusion experiments and modelling, pore constrictions in fibrous pit membranes are estimated to be well below 50 nm, and typically smaller than 20 nm. Together with the low dynamic surface tensions of amphiphilic lipids at air-water interfaces in pit membranes, 5 to 20 nm pore constrictions are in line with the observed xylem water potentials values that generally induce spread of embolism. Moreover, pit membranes appear to show ideal porous medium properties for sap flow to promote hydraulic efficiency and safety due to their very high porosity (pore volume fraction), with highly interconnected, non-tortuous pore pathways, and the occurrence of multiple pore constrictions within a single pore. This three-dimensional view of pit membranes as mesoporous media may explain the relationship between pit membrane thickness and embolism resistance, but is largely incompatible with earlier, two-dimensional views on air-seeding. It is hypothesised that pit membranes enable water transport under negative pressure by producing stable, surfactant coated nanobubbles while preventing the entry of large bubbles that would cause embolism.

High-pressure freezing followed by freeze-substitution is a valuable method for ultrastructural analyses of resin-embedded biological samples. The visualization of lipid membranes is one of the most critical aspects of any ultrastructural study and can be especially challenging in high-pressure frozen specimens. Historically, osmium tetroxide has been the preferred fixative and staining agent for lipid-containing structures in freeze-substitution solutions. However, osmium tetroxide is not only a rare and expensive material, but also volatile and toxic. Here, we introduce the use of a combination of potassium permanganate, uranyl acetate, and water in acetone as complementing reagents during the freeze-substitution process. This mix imparts an intense en bloc stain to cellular ultrastructure and membranes, which makes poststaining superfluous and is well suited for block-face imaging. Thus, potassium permanganate can effectively replace osmium tetroxide in the freeze-substitution solution without sacrificing the quality of ultrastructural preservation.

Copper is the most widely used substrate for Li deposition and dissolution in lithium metal anodes, which is complicated by the formation of solid electrolyte interphases (SEIs), whose physical and chemical properties can affect Li deposition and dissolution significantly. However, initial Li nucleation and growth on bare Cu creates Li nuclei that only partially cover the Cu surface so that SEI formation could proceed not only on Li nuclei but also on the bare region of the Cu surface with different kinetics, which may affect the follow-up processes distinctively. In this paper, we employ

Cobaloximes are promising, earth-abundant catalysts for the light-driven hydrogen evolution reaction. Typically, these cobalt(III) complexes are prepared in situ or employed in their neutral form, e.g. [Co(dmgH 2 )(py)Cl], even though related complex salts have been reported previously and could in principle offer improved catalytic activity as well as more efficient immobilization on solid support. Here we report an interdisciplinary investigation into complex salts [Co(dmgH) 2 (py) 2 ] + [Co(dmgBPh 2 ) 2 Cl 2 ] - , TBA + [Co(dmgBPh 2 ) 2 Cl 2 ] - and [Co(dmgH) 2 (py) 2 ] + BArF - . We describe their strategic syntheses from commercially available complex [Co(dmgH) 2 (py)Cl] and demonstrate that these double and single complex salts are potent catalysts for the light-driven hydrogen evolution reaction. We also show that scanning electrochemical cell microscopy can be used to deposit arrays of catalysts [Co(dmgH) 2 (py) 2 ] + [Co(dmgBPh 2 ) 2 Cl 2 ] - and [Co(dmgH) 2 (py)Cl] on supported and free-standing amino-terminated ~ 1 nm thick carbon nanomembranes (CNMs). Photocatalytic H 2 evolution at such arrays was quantified with Pd microsensors using scanning electrochemical microscopy, thus providing a new approach for catalytic evaluation and opening up novel routes for the creation and analysis of “designer catalyst arrays”, nano-printed in a desired pattern on a solid support.

Silver-fluoropolymer (Ag-CF

PML nuclear bodies (PML-NBs) are dynamic interchromosomal macromolecular complexes implicated in epigenetic regulation as well as antiviral defense. During herpesvirus infection, PML-NBs induce epigenetic silencing of viral genomes, however, this defense is antagonized by viral regulatory proteins such as IE1 of human cytomegalovirus (HCMV). Here, we show that PML-NBs undergo a drastic rearrangement into highly enlarged PML cages upon infection with IE1-deficient HCMV. Importantly, our results demonstrate that dual signaling by interferon and DNA damage response is required to elicit giant PML-NBs. DNA labeling revealed that invading HCMV genomes are entrapped inside PML-NBs and remain stably associated with PML cages in a transcriptionally repressed state. Intriguingly, by correlative light and transmission electron microscopy (EM), we observed that PML cages also entrap newly assembled viral capsids demonstrating a second defense layer in cells with incomplete first line response. Further characterization by 3D EM showed that hundreds of viral capsids are tightly packed into several layers of fibrous PML. Overall, our data indicate that giant PML-NBs arise via combined interferon and DNA damage signaling which triggers entrapment of both nucleic acids and proteinaceous components. This represents a multilayered defense strategy to act in a cytoprotective manner and to combat viral infections.

Single and multi-barrel nanopipettes and nanopipette-based scanning electrochemical probe microscopy techniques like scanning electrochemical cell microscopy (SECCM) have gained significant attention as tools for localized, maskless, three-dimensional surface modifications [1,2]. The nanometer-sized orifices of nanopipettes allow delivering molecules to solution inducing concentration-confined electrodepositions. Also, electroless nanoscale depositions like the fountain pen technique [3] can be achieved by this technique. In this study, we present the deposition of various cobaloxime-based earth-abundant Co catalysts for light-driven hydrogen evolution reaction (HER) [4]. Arrays of different cobalt(III) complexes were deposited via SECCM and investigated in respect with their HER activity using scanning electrochemical microscopy (SECM) in combination of Pd-microsensors [5] for in situ hydrogen (H2) measurements under illumination. In addition, AFM studies revealed possible degradation of the commercially available neutral benchmark complex [Co(dmgH)2(py)Cl] in these studies. First results will also be presented in respect with the deposition of nanowires via co-deposition of HER catalyst and Ruthenium photosensitizer. First spatially resolved photocatalytic studies at such nanowires, which are characterized by high surface area, will be presented. Also, the influence of the substrate will also be discussed. References: Oswald, K. Palanisamy, C. Kranz, Curr. Op. Electrochem. 34, 100965 (2022). Hengsteler et al., Nano Lett. 21, 9093 (2021). -H. Kim, N. Moldovan, H.D. Espinosa, Small 1, 632, (2005). Oswald et al., Chem. Eur. J. 27, 16896 (2021) and corrigendum (2022); doi:10.1002/chem.2022008809. Kund et al., ChemElectroChem 9, e202200071 (2022) Funding by the German Science Foundation (DFG) – project number 364549901 – TRR 234 (projects B7, C4).

Rechargeable post Li-ion batteries based on aluminum (Al) are gaining attention due to high abundance of Al, the high theoretical volumetric capacity, and high safety associated with the low flammability [1,2]. In comparison to Li-ion batteries (LiBs), where the solid-electrolyte interphase (SEI) has been studied for decades, little is known on SEI formation in dependence of the used electrolyte for Al electrodes. In this study, we present the electrochemical performance of Al foils with two different thicknesses (0.025 mm and 0.075 mm), which were used as negative electrode in Al-ion batteries in AlCl3/1-ethyl-3-methylimidazolium chloride [EMIm]Cl electrolyte. Atomic force microscopy (AFM) was used to determine changes in the morphology of Al foils during the charge - discharge process to obtain information on the SEI and its microstructural morphology [3]. Spatially-resolved information on the electrochemical activity of interphase layers on cycled Al foils can be obtained via scanning electrochemical microscopy (SECM), which so far has only be studied at LiBs [4]. First results reveal the correlation between the morphological changes of SEI layer during cycling and its electrochemical behavior depending on the Al foil surface properties, which will be presented and discussed in this contribution. Key words: Al foil, AFM, microstructure, SEI layer, SECM. References: Meng-Chang Lin, Ming Gong, Bingan Lu, Yingpeng Wu, Di-Yan Wang, Mingyun Guan, Michael Angell, Changxin Chen, Jiang Yang, Bing-Joe Hwang and Hongjie Dai, Nature, 520, 325–328 (2015). Li, and N.J. Bjerrum, J. Power Sources, 110, 1–10 (2002). Feng Wu, Na Zhu, Ying Bai, Yaning Gao, and Chuan Wu, Green Energy & Environment 3, 71-77, (2018). Bastian Krueger, Luis Balboa, Jan Frederik Dohmann, Martin Winter, Peter Bieker and Gunther Wittstock. ChemElectroChem,7, 3590–3596, (2020). This work contributes to the research performed at CELEST (Center for Electrochemical Energy Storage Ulm-Karlsruhe) and was funded by the German Research Foundation (DFG) under Project ID 390874152 (POLiS Cluster of Excellence).

Diamond coatings are characterised by outstanding mechanical and chemical robustness and hence, thin diamond layers doped with boron are particularly interesting for transparent electrodes, e.g., for spectroelectrochemical applications. In this study, we present a non-destructive chemometric method to determine thickness and boron concentration of as-deposited heavily doped diamond films on silicon substrates, which may be used, e.g., as electroactive infrared transparent windows. Using partial least-squares regression, we readily predicted these parameters with high accuracy from Raman spectra after calibration with a set of diamond films, previously characterised by secondary ion mass spectrometry. Due to the Fano resonance caused by the boron incorporation into the diamond lattice, which is observable in the Raman spectrum, a precise determination of the boron concentration is possible. In addition, for diamond films below the wavelength of the used Raman laser, we were able to determine the thickness of the as-grown films and gain information on the underlying substrate.

Microelectrochemistry has a long history in the life sciences for in vivo and in vitro measurements of e.g., pH, oxygen, and signaling molecules such as nitric oxide (NO), adenosine-5`-triphosphate (ATP), hydrogen peroxide (H2O2) and neurotransmitters. In particular, gaining information on signaling molecules at live cells, e.g., during and after stimulation is of significance for understanding cell signaling. Within recent years, our research team has focused on the development of micro-sized sensing approaches for the detection of ATP [1,2], which is considered among the most important autocrine and paracrine signaling molecules [3]. H2O2 belongs to the group of reactive oxygen species (ROS), which is in contrast to radical ROS rather stable. H2O2 is involved in many physiological processes such as hypoxic signal transduction, cell differentiation and proliferation but is also involved in mediating immune responses [4]. The effect is, among other parameters, dependent on its local concentration and its exposure time. Platinum black is a highly suitable electrocatalytic nanomaterial for the electrochemical detection of H2O2 [5]. We recently demonstrated that Pt black modified microelectrodes can be used for H2O2 at granulocytes and peripheral blood mononuclear cells from pigs [6]. Within this presentation, we will introduce dual functional miniaturized probes that allow further miniaturization of electrochemical sensors for biomedical applications. We will demonstrate that these probes have great potential for cell measurements, i.e., at macrophages that produce and release ROS in response to phagocytosis or stimulation. References [1] E. Hecht, A. Liedert, A. Ignatius, B. Mizaikoff, C. Kranz, Biosens. Bioelectron. 2013, 44, 27. [2] C. Ziller, et al., ChemElectroChem 2017, 4, 864. [3] R. Corriden, P. A. Insel, Sci. Signal. 2010, 3, 104. [4] C. Lennicke et al., Cell Commun. Signal. 2015, 13, 39. [5] Y. Li, C. Sella, F. Lemaitre, M.G. Collignon, L. Thouin, C. Amatore, Electroanalysis 2013, 25, 895. [6] A. Hellmann, S. Daboss, F. Zink, C. Hartmann, P. Radermacher, C. Kranz, Electrochim. Acta 2020, 353, 30851

Polydopamine (PDA) is a synthetic eumelanin polymer which is, to date, mostly obtained by dip coating processes. In this contribution, we evaluate the physical and electrochemical properties of electrochemically deposited PDA films obtained by cyclic voltammetry or pulsed deposition. The obtained PDA thin films are investigated with respect to their electrochemical properties, i.e., electron transfer (ET) kinetics and charge transfer resistance using scanning electrochemical microscopy and electrochemical impedance spectroscopy, and their nanomechanical properties, i.e., Young’s modulus and adhesion forces at varying experimental conditions, such as applied potential or pH value of the medium using atomic force microscopy. In particular, the ET behavior at different pH values has not to date been investigated in detail for electrodeposited PDA thin films, which is of particular interest for a multitude of applications. Adhesion forces strongly depend on applied potential and surrounding pH value. Moreover, force spectroscopic measurements reveal a significantly higher percentage of polymeric character compared to films obtained by dip coating. Additionally, distinct differences between the two depositions methods are observed, which indicate that the pulse deposition process leads to denser, more cross-linked films.

Despite their technological importance for water splitting, the reaction mechanisms of most water oxidation catalysts (WOCs) are poorly understood. This paper combines theoretical and experimental methods to reveal mechanistic insights into the reactivity of the highly active molecular manganese vanadium oxide WOC [Mn4V4O17(OAc)3]3− in aqueous acetonitrile solutions. Using density functional theory together with electrochemistry and IR-spectroscopy, we propose a sequential three-step activation mechanism including a one-electron oxidation of the catalyst from [Mn23+Mn24+] to [Mn3+Mn34+], acetate-to-water ligand exchange, and a second one-electron oxidation from [Mn3+Mn34+] to [Mn44+]. Analysis of several plausible ligand exchange pathways shows that nucleophilic attack of water molecules along the Jahn–Teller axis of the Mn3+ centers leads to significantly lower activation barriers compared with attack at Mn4+ centers. Deprotonation of one water ligand by the leaving acetate group leads to the formation of the activated species [Mn4V4O17(OAc)2(H2O)(OH)]− featuring one H2O and one OH ligand. Redox potentials based on the computed intermediates are in excellent agreement with electrochemical measurements at various solvent compositions. This intricate interplay between redox chemistry and ligand exchange controls the formation of the catalytically active species. These results provide key reactivity information essential to further study bio-inspired molecular WOCs and solid-state manganese oxide catalysts., Combined theoretical and experimental studies shed light on the initial steps of redox-activation of a molecular manganese vanadium oxide water oxidation catalyst.

Immune cell activation leads to the acquisition of new functions, such as proliferation, chemotaxis, and cytokine production. These functional changes require continuous metabolic adaption in order to sustain ATP homeostasis for sufficient host defense. The bioenergetic demands are usually met by the interconnected metabolic pathways glycolysis, TCA cycle, and oxidative phosphorylation. Apart from glucose, other sources, such as fatty acids and glutamine, are able to fuel the TCA cycle.Rising evidence has shown that cellular metabolism has a direct effect on the regulation of immune cell functions. Thus, quiescent immune cells maintain a basal metabolic state, which shifts to an accelerated metabolic level upon immune cell activation in order to promote key effector functions.This review article summarizes distinct metabolic signatures of key immune cell subsets from quiescence to activation and demonstrates a methodical concept of how to assess cellular metabolic pathways. It further discusses why metabolic functions are of rising interest for translational research and how they can be affected by the underlying pathophysiological condition and/or therapeutic interventions.

Research on light-driven catalysis has gained tremendous importance due to the ever-increasing power consumption and the threatening situation of global warming related to burning fossil fuels. Significant efforts have been dedicated to artificial photosynthesis mimicking nature to split H2O into H2 and O2 by solar energy. Novel semiconductor und molecular photocatalysts focusing on one-step excitation processes via single component photocatalysts or via two-step excitation processes mimicking the Z-scheme of natural photosynthesis are currently developed. Analytical and physicochemical methods, which provide information at different time and length scales, are used to gain fundamental understanding of all processes leading to catalytic activity, i.e., light absorption, charge separation, transfer of charges to the reaction centres and catalytic turnover, but also understanding degradation processes of the photocatalytic active material. Especially, molecular photocatalysts still suffer from limited long-term stability due to the formation of reactive intermediates, which may lead to degradation. Although there is an overwhelming number of research articles and reviews focussing on various materials for photocatalytic water splitting, to date only few reviews have been published providing a comprehensive overview on methods for characterizing such materials. This review will highlight spectroscopic, spectroelectrochemical, and electrochemical approaches in respect to their potential in studying processes in semiconductor and (supra)molecular photocatalysts. Special emphasis will be on spectroscopic methods to investigate light-induced processes in intermediates of sequential electron transfer chains. Further, microscopic characterization methods, which are predominantly used for semiconducting and hybrid photocatalytic materials will be reviewed as surface area, structure, facets, defects, and bulk properties such as crystallinity and crystal size are key parameters for charge separation, transfer processes and suppression of charge recombination. Recent developments in scanning probe microscopy will also be highlighted as such techniques are highly suited for studying photocatalytic active material.

We present FIB/SEM tomography combined with an optimized embedding procedure and osmium tetroxide staining to trace and visualize the initial self-conditioning step as well as degradation processes of [5,15-bis(ethynyl)-10,20-diphenylporphinato]copper(II) (CuDEPP) composite electrodes for the first time. Staining with osmium tetroxide allowed visualizing chemical changes of the active CuDEPP material. Four composite electrode samples prior and after cycling with different cycle numbers in LiPF6 electrolyte (i.e., pristine, one, 200 and 2000 charging cycles) were investigated and for all samples 3D reconstructions with a voxel size of 7.15 × 7.15 × 20 nm3 were performed. The samples were further analyzed by wavelength-dispersive X-ray (WDX) spectroscopy revealing the insertion of the electrolyte into the active material of the electrode. The formation of an interphase adjacent to the inner pore space of the active CuDEPP material could be unambiguously identified. In addition, Raman spectroscopy results confirmed the self-conditioning and degradation processes of the metalloporphyrin complex.

Microbial biofilms are a crucial problem in many areas including the food processing industry, biotechnology, water quality and medical scenarios. The complexity of biofilm formation and subsequent prevention strategies - requires a fundamental understanding of the involved molecular mechanisms and the possibility of long-term monitoring biofilm formation. Infrared attenuated total reflection (IR-ATR) spectroscopy is a versatile analytical technique for monitoring biofilm formation of bacteria isolates in situ, non-destructively, and close to real time as an innovative approach providing molecular insight into biofilm formation [1]. The utility of IR-ATR to investigate microorganism behavior within biofilms derives from the evanescent field penetrating few micrometers into the biofilm formed directly at the interface of a multi-reflection ATR waveguide and the sample. In the present study, isolates from food biogenic amine (BA)-producing bacteria, Lactobacillus parabuchneri DSM 5987 strains formed in cheese are analyzed for developing a deeper understanding on the formation of biofilms, which are significant contributors to the presence of histamine in dairy food products [2]. Infrared spectra were recorded using a custom flow-through ATR assembly for revealing the metabolism of microorganisms within such biofilms along with the effects of the substrate functionality and culture conditions on the extracellular biopolymeric matrices [3,4]. The appearance of key IR bands in the region of 1600-1200 cm-1 indicates the production of lactic acid or lactate and the presence of amide groups, while most pronounced intensities in 1140-950 cm-1 correspond to phospholipids, polysaccharides and nucleic acids. In this study, the spectral region between 1700 and 600 cm-1 was determined to be the representative region for the identification of Lactobacillus parabuchneri biofilms enabling to study bioadhesion mechanisms and physico-chemical property changes during extended periods of biofilm growth. Real time monitoring has led to concrete steps for inhibition and disintegration via suitable antimicrobials by deposition on the IR inactive region of ATR waveguide. Multivariate data evaluation and classification strategies were applied to enable efficient multiparametric analysis for providing molecular information facilitating a better understanding of biofilm formation, maturation and changes in biofilm architecture via IR spectroscopic data. Keywords: IR-ATR spectroscopy, in situ monitoring, Lactobacillus parabuchneri, biofilm, ATR waveguide, flow-through ATR, lactic acid, multivariate data analysis. References: [1] Stenclova P, Freisinger S, et al. Appl. Spectro., 2019; Vol.73 (4) 424-432 [2] Yunda E, Quilès F, et al. Biofouling, 2019; Vol.35 (5) 494-507 [3] Diaz M, del Rio B, et al. Food Microbiol., 2016; Vol.7 (591) 85-91 [4] Lorite G, de Souza A, et al. Colloids Surfaces B. Biointerfaces, 2013; Vol. 102 519-525

Biofilms are considered a major cause of serious health issues in human medicine and food industry, due to their resistance against harsh conditions and pharmacological treatment [1]. Biofilms are defined as three-dimensional structures encasing bacterial communities rooted in extracellular polymeric substances (EPS). These complex systems are strongly influenced by a variety of parameters including biofilm age, external conditions, nutrient deficiency, attack of exogenous agents [2]. Moreover, bacterial colonies may activate survival strategies when subjected to stress such as the presence of antimicrobial agents. Even cannibalistic behavior may occur [3], which involves the secretion of cannibalism toxins inducing the generation of lysed cells providing nutrients. Several methodologies were developed for or adapted to biofilm formation studies enabling a more comprehensive understanding of biofilm physiology, structure, and composition. This information should facilitate the development of more effective eradication strategies. Infrared spectroscopy in attenuated total reflectance (IR-ATR) mode provides in-situ and close to real time monitoring of biofilm lifecycles providing molecular information on the various stages of biofilm formation. Given the antibiotic resistance of biofilms [4], it is of increasing importance to develop innovative methodologies for the treatment of biofilm-related infections. While our research team has shown the generic utility of antimicrobial nanoparticles (NPs) such as ZnONPs, AgNPs, CuNPs, etc. in the past [5], the current study focuses on AgNPs embedded within fluoropolymer matrices with tunable loading of the NPs. Next to morphological studies by TEM and AFM, detailed XPS investigations revealed the surface chemical composition. In addition, the kinetics of antimicrobial ion release enabled correlating the behavior of the nanocomposite to its swelling properties and 3D modification after immersion in liquids. Biofilm growth and inhibition was studied via AFM, optical microscopy and IR-ATR. The IR analysis of the biofilm allowed collecting molecular information on the biofilm behavior during long-term contact with antimicrobial surfaces. It was demonstrated that bacterial cells may re-colonize on top of dead biomass once the latter is thick enough to prevent direct interaction with the antimicrobial surface. In summary, this study represents an excellent foundation for developing an in depth understanding on the behavior of bacterial colonies and nascent biofilms in contact with surfaces decorated with nanoantimicrobials over extended periods of time. It is anticipated that an improved understanding on the stages of biofilm formation provides insight into the processes governing antimicrobial resistance phenomena. Finally, present antimicrobial material may be a useful strategy against Corona viruses. An outlook to this urging topic will be also presented. [1] N. Billings et al., Rep. Prog. Phys., 2015, 78, 036601. [2] D.O. Serra et al., MBio., 2013, 4, e00103. [3] C. Höfler et al., Microbiology, 2016, 162, 164. [4] M.C. Sportelli et al., Sci. Rep., 2017, 7, 11870. [5] M.C. Sportelli et al., TrAC, 2016, 84, 131.

Biofilms are well-organized sessile communities which exhibit an increased tolerance against antimicrobial and antibiotic treatments in comparison with their planktonic counterparts. Biofilms are ubiquitous and due to their high resilience, the problem with contamination of medical implants leads to serious health problems [1]. Within the last decades, novel therapies to prevent the formation of biofilms have been developed and, among others, antimicrobials based on metal nanoparticles (NPs) have been intensively studied [2], due to their ability to reduce biofilm formation. Silver nanoparticles (AgNPs) are known to be effective antimicrobial agents, as silver(I) has the ability to penetrate the cell and produce oxidative stress via the generation of reactive oxygen species (ROS) [3]. To understand the release mechanism of silver(I) ions, scanning electrochemical probe microscopy such as scanning electrochemical microscopy (SECM) is highly suitable. In this contribution, biocompatible AgNPs-fluoropolymer (Ag-CFx) composite films, prepared by ion beam sputtering (IBS) deposition [4], are investigated in respect to silver(I) release associated to the swelling of the antimicrobial film. The mechanism of the silver(I) release is studied real-time by scanning electrochemical microscopy (SECM) in combination with square-wave stripping voltammetry and the relation between controlled silver(I) release and the swelling of Ag-CFx films will be presented, combining electrochemical techniques and atomic force microscopy (AFM). References [1] G.C. Anderson, et al. Innate and Induced Resistance Mechanisms of Bacterial Biofilms. In Bacterial Biofilms; Romeo, T., Ed.; Springer Berlin Heidelberg: Berlin, Heidelberg, 2008; pp 85–105. [2] M.C. Sportelli, et al. Nano-Antimicrobials Based on Metals. In Novel Antimicrobial Agents and Strategies; John Wiley & Sons, Ltd, 2014; pp 181–218. [3] N. Durán, et al. Nanomedicine, 2016, 12(3), 789-799. [4] M.C. Sportelli, et al. Sci. Rep. 2017, 7 (1), 11870. Acknowledgements Financial support is acknowledged from European Union’s 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 813439.

Secretion of pulmonary surfactant in the alveoli of the lungs is essential to maintain lung function. Stretching of alveoli during lung inflation is the main trigger for surfactant secretion. Yet, the molecular mechanisms how mechanical distension of alveoli results in surfactant secretion are still elusive. The alveolar epithelium consists of alveolar epithelial type I (ATI) and surfactant secreting type II (ATII) cells. ATI, but not ATII cells, express caveolae, small plasma membrane invaginations that can respond to plasma membrane stresses and serve mechanotransductive roles. Within this study, we investigated the role of caveolae as mechanosensors in the alveolus. We generated a human caveolin���1 knockout ATI cell (hAELVicav���/���) using CRISPR/Cas9. Wildtype (hAELViwt) and hAELVicav���/��� cells grown on flexible membranes responded to increasing stretch amplitudes with rises in intracellular Ca2+. The response was less frequent and started at higher stretch amplitudes in hAELVicav���/��� cells. Stretch���induced Ca2+���signals depended on Ca2+���entry via piezo1 channels, localized within caveolae in hAELViwt and primary ATI cells. Ca2+���entry via piezo1 activated pannexin���1 hemichannels resulting in ATP release from ATI cells. ATP release was reduced in hAELVicav���/��� cells. In co���cultures resembling the alveolar epithelium, released ATP stimulated Ca2+ signals and surfactant secretion from neighboring ATII cells when co���cultured with hAELViwt but not hAELVicav���/��� cells. In summary, we propose that caveolae in ATI cells are mechanosensors within alveoli regulating stretch���induced surfactant secretion from ATII cells., publishedVersion

Biofilms are known to be well-organized microbial communities embedded in an extracellular polymeric matrix, which supplies bacterial protection against external stressors. Biofilms are widespread and diverse, and despite the considerable large number of publications and efforts reported regarding composition, structure and cell-to-cell communication within biofilms in the last decades, the mechanisms of biofilm formation, the interaction and communication between bacteria are still not fully understood. This knowledge is required to understand why biofilms form and how we can combat them or how we can take advantage of these sessile communities, e.g. in biofuel cells. Therefore, in situ and real-time monitoring of nutrients, metabolites and quorum sensing molecules is of high importance, which may help to fill that knowledge gap. This review focuses on the potential of scanning electrochemical microscopy (SECM) as a versatile method for in situ studies providing temporal and lateral resolution in order to elucidate cell-to-cell communication, microbial metabolism and antimicrobial impact, e.g. of antimicrobial coatings through the study of electrochemical active molecules. Given the complexity and diversity of biofilms, challenges and limitations will be also discussed., publishedVersion