Boron-nitride-rich organic thin materials based on borazines have gained significant attention for their potential in nano(opto)electronic and energy storage devices. We address synthetic challenges in producing effective borazine-based thin films by proposing a dual theoretical and experimental protocol. This combines a multiscale computational approach, using density functional theory and classical molecular dynamics, with synthesis and thin-film formation via the Langmuir-Blodgett technique. The computational modeling focuses on three key properties: π-π stacking interactions, molecular steric hindrance, and dynamic self-assembly orientation. This modeling guided the selection of a borazine molecular building block and enabled the successful experimental formation of a free-standing molecular-thin borazine-based film. Solely π-π stacking interactions were found to drive the formation of a bilayer film with a molecular thickness of 2.1 nm, capable of spanning 0.6 μm diameter holes as a free-standing film. The agreement between theory and experiment confirms that the film retains essential features of the borazine molecular crystal, particularly intermolecular offset face-to-face π-π stacking and hexagonal-based pattern orientations. We thus establish a robust and transferable approach for modeling and synthesizing borazine-based thin materials, deepen the understanding of molecular interactions in borazine self-assembly, and demonstrate the suitability of the Langmuir-Blodgett technique for fabricating borazine-based 2D materials.

Bismuth vanadate (BiVO4) shows promise as a photoanode for water oxidation, with a relatively low band gap of 2.4 eV. However, its performance is limited by poor carrier separation and surface recombination. To address these limitations, a BiVO4-Cu2O/CuO nanocube (NC) heterojunction was successfully developed, increasing the photogenerated oxygen evolution current density to 2.3 mA/cm2 at 1.23 V vs RHE, compared to 1.4 mA/cm2 for bare BiVO4. Addition of drop-casted Cu2O/CuO NCs on BiVO4 increases both the charge injection efficiency and the charge separation efficiency to over 60% at 1.23 V vs RHE. In comparison, the addition of drop-casted CuO nanowires (NWs) to BiVO4 increased the charge injection efficiency to over 65%, but it only moderately increased the charge separation efficiency to 49% at 1.23 V vs RHE. These results highlight the importance of the interface between BiVO4 and the catalyst layer for an enhanced photocurrent. In the Cu2O/CuO NCs, bulk Cu2O likely serves as a hole-extracting heterojunction, while surface CuO likely functions as a catalyst. In contrast, the CuO NWs function primarily as a catalyst.

In contrast to the common viewpoint that bacteriochlorophyll (BChl) motion is largely absent within the chlorosome assembly, physics-based modeling points to a crucial role of the nanoscale librational motion of the macrocycle for the transfer of excitons. To elucidate this motion experimentally, compositional uniformity and high sensitivity are required. We focused on uniformly 13C labeled chlorosome preparations from the bchQ mutant Chlorobaculum tepidum with significantly enhanced structural homogeneity. The librational motion is characterized using Rotational Echo DOuble Resonance (REDOR), and in addition, the impact of temperature on specific functionalities within BChl molecules is studied with 1-dimensional and 2-dimensional dipolar and scalar-based MAS NMR measurements. Results show the gradual freezing of the tails and side chains of the BChls with decreasing temperature. However, the librational motion analyzed by measuring the 5C-H dipolar coupling strength obtained from REDOR data sets persists at different temperatures. REDOR simulations show a close match to the experimental dephasing frequency of oscillation for a dipolar coupling strength of 17.5 ± 0.5 kHz which is considerably less than the dipolar coupling strength of 22.7 kHz in the rigid limit. Following a two-site jump model, we arrive at an estimate for BChl libration sampling at an angle of θ = 48 ± 4°, corroborating that the macrocycle indeed experiences significant librational motion on a time scale that is short compared to the NMR measurement time. This finding is in full quantitative support of the dominant rotational motion exhibited by the BChl macrocycle estimated from early MD simulations.

Developing functional perovskites is important for advancing solar energy conversion technologies. This study investigates the effects of dopants on the structural, optical, electronic, and solar conversion performances of Ba2M0.4Bi1.6O6 double perovskites. X-ray diffraction (XRD) and Rietveld refinement confirm crystallization in the I2/m space group (M = La, Ce, Pr, Pb), and Fm3¯m and I2/m space groups (M = Y). The B1-O-B2 structure modulates to highly ordered (M = La, Y), partially ordered (M = Pr), or disordered (M = Ce, Pb). UV-vis spectra show strong light absorption, with Tauc plots estimating ~1.57 eV (M = La) and ~1.73 eV (M = Pr) optical band gaps. Under AM 1.5G illumination, the M = La photoelectrode generates photocurrents of 1 mA cm−2 at 0.3 VRHE, surpassing M = Ce and Pb (1 μm, 4-times spin-coating). Increasing its thickness to 7.7 μm (4-times dip-coating) further enhances the photocurrents to 2.3 mA cm−2 at 0.2 VRHE, outperforming all counterparts due to improved stability. Fine-tuning crystal and electronic structures via strategic B-site doping provides a new route for engineering Ba2Bi2O6-based double perovskites for broad solar energy conversion applications.

Localized 1H magnetic resonance spectroscopy (MRS) is a powerful tool in pre-clinical and clinical neurological research, offering non-invasive insight into neurochemical composition in localized brain regions. Zebrafish (Danio rerio) are increasingly being utilized as models in neurological disorder research, providing valuable insights into disease mechanisms. However, the small size of the zebrafish brain and limited MRS sensitivity at low magnetic fields hinder comprehensive neurochemical analysis of localized brain regions. Here, we investigate the potential of ultra-high-field (UHF) MR systems, particularly 28.2 T, for this purpose. This present study pioneers the application of localized 1H spectroscopy in zebrafish brain at 28.2 T. Point resolved spectroscopy (PRESS) sequence parameters were optimized to reduce the impact of chemical shift displacement error and to enable molecular level information from distinct brain regions. Optimized parameters included gradient strength, excitation frequency, echo time, and voxel volume specifically targeting the 0–4.5 ppm chemical shift regions. Exceptionally high-resolution cerebral metabolite spectra were successfully acquired from localized regions of the zebrafish brain in voxels as small as 125 nL, allowing for the identification and quantification of major brain metabolites with remarkable spectral clarity, including lactate, myo-inositol, creatine, alanine, glutamate, glutamine, choline (phosphocholine + glycerol-phospho-choline), taurine, aspartate, N-acetylaspartyl-glutamate (NAAG), N-acetylaspartate (NAA), and γ-aminobutyric acid (GABA). The unprecedented spatial resolution achieved in a small model organism enabled detailed comparisons of the neurochemical composition across distinct zebrafish brain regions, including the forebrain, midbrain, and hindbrain. This level of precision opens exciting new opportunities to investigate how specific diseases in zebrafish models influence the neurochemical composition of specific brain areas.

An Axiomatic Design (AD) theoretical protocol is proposed for the analysis and noniterative engineering of photoelectrochemical (PEC) cells that can convert CO2 toward C2+ products. AD provides criteria for identifying and selecting materials based on data commonly available in the literature. In addition, it establishes a design order for how to achieve optimal integration of materials for catalysis and light-induced charge separation with a proton-transporting membrane in a noniterative manner by matching relevant fluxes with concentration at interfaces across the design. For a hypothetical tandem PEC flow cell reactor for ethylene as an example, the AD protocol predicts an upper bound of 31 μmol h-1 cm-2 at 12% solar-to-product efficiency following PEC process optimization with a design path comprising five steps, starting from data for an O-(II)-D-Cu CO2 reduction reaction (CO2RR) catalyst and including current concentration to tailor the overpotential. The computational procedure provides models with high yield and robustness by balancing high selectivity with low overpotential and a broad operation range of 0.5-1.2 Sun with a dual absorber with bandgaps of 1.90 and 1.35 eV and a fill factor of 0.85. The procedures are implemented in Python and use a decoupled design matrix that eliminates interdependencies between components.

3-Hydroxypropionic acid (3-HP) serves as a crucial platform chemical with diverse applications across various industries. In this study, the oxaloacetate pathway was utilized for 3-HP production. This pathway involves the decarboxylation of oxaloacetate into malonic semialdehyde, catalyzed by branched-chain α-keto acid decarboxylase (KdcA), which is subsequently reduced to 3-HP by dehydrogenases. Directed evolution of KdcA was carried out to enhance its catalytic efficiency toward oxaloacetate, resulting in a KdcAM8 mutant with the following substitutions: S286R, S287T, F381H, F382P, L534S, L535F, M538T, and G539F. Compared to wild-type (WT) KdcA, KdcAM8 exhibits a lower KM value toward oxaloacetate (KM = 1.15 mM vs KM > 25 mM). Among these mutations, the single mutants S286R and S287T exhibited 5.5-fold and 1.3-fold increased activities, respectively. Instead of WT KdcA, the KdcAM8 mutant was integrated into Escherichia coli (E. coli) BL21 strain, resulting in the production of 3-HP at a concentration of 0.11 mM. To further improve 3-HP production, two dehydrogenases were compared for the downstream conversion of malonic semialdehyde into 3-HP, and two carboxylases were explored to enhance the upstream precursor supply of oxaloacetate. Additionally, the growth conditions were optimized. Finally, a nonnatural oxaloacetate pathway was successfully engineered in the E. coli BL21 strain, achieving a 3-HP titer of approximately 0.71 mM from glucose. This work illustrates that protein engineering is a powerful tool for modulating flux in the target pathway and holds promise for the future development of the oxaloacetate pathway to improve the 3-HP yield.

A fundamental understanding of proton transport through graphene nanopores, defects, and vacancies is essential for advancing two-dimensional proton exchange membranes (PEMs). This study employs ReaxFF molecular dynamics, metadynamics, and density functional theory to investigate the enhanced proton transport through a graphene nanopore. Covalently functionalizing the nanopore with a benzenesulfonic group yields consistent improvements in proton permeability, with a lower activation barrier (≈0.15 eV) and increased proton selectivity over sodium cations. The benzenesulfonic functionality acts as a dynamic proton shuttle, establishing a favorable hydrogen-bonding network and an efficient proton transport channel. The model reveals an optimal balance between proton permeability and selectivity, which is essential for effective proton exchange membranes. Notably, the benzenesulfonic-functionalized graphene nanopore system achieves a theoretically estimated proton diffusion coefficient comparable to or higher than the current state-of-the-art PEM, Nafion. Ergo, the benzenesulfonic functionalization of graphene nanopores, firmly holds promise for future graphene-based membrane development in energy conversion devices.

Chlorosomes, the photosynthetic antenna complexes of green sulfur bacteria, are paradigms for light-harvesting elements in artificial designs, owing to their efficient energy transfer without protein participation. We combined magic angle spinning (MAS) NMR, optical spectroscopy and cryogenic electron microscopy (cryo-EM) to characterize the structure of chlorosomes from a bchQ mutant of Chlorobaculum tepidum. The chlorosomes of this mutant have a more uniform composition of bacteriochlorophyll (BChl) with a predominant homolog, [8Ethyl, 12Ethyl] BChl c, compared to the wild type (WT). Nearly complete 13C chemical shift assignments were obtained from well-resolved homonuclear 13C-13C RFDR data. For proton assignments heteronuclear 13C-1H (hCH) data sets were collected at 1.2 GHz spinning at 60 kHz. The CHHC experiments revealed intermolecular correlations between 132/31, 132/32, and 121/31, with distance constraints of less than 5 Å. These constraints indicate the syn-anti parallel stacking motif for the aggregates. Fourier transform cryo-EM data reveal an axial repeat of 1.49 nm for the helical tubular aggregates, perpendicular to the inter-tube separation of 2.1 nm. This axial repeat is different from WT and is in line with BChl syn-anti stacks running essentially parallel to the tube axis. Such a packing mode is in agreement with the signature of the Qy band in circular dichroism (CD). Combining the experimental data with computational insight suggests that the packing for the light-harvesting function is similar between WT and bchQ, while the chirality within the chlorosomes is modestly but detectably affected by the reduced compositional heterogeneity in bchQ.

In the past decade, Ru-bda (bda = 2,2 '-bipyridine-6,6 '-dicarboxylic acid) complexes have emerged as extremely effective water oxidation catalysts, rendering them a potential candidate for incorporation into dye-sensitized photoelectrochemical cells. However, the performance of these catalysts declines dramatically when anchored to a photoanode surface due to their catalytic mechanism involving the interaction of two metal centers (I2M). This reduced performance prompts an investigation into the catalytic cycle following an alternative mechanism in which the O-O bond is formed through a water nucleophilic attack (WNA). In this work, we have performed hybrid-DFT based molecular dynamics simulations of the rate-determining O-O bond formation following the WNA mechanism in a [Ru-bda]-dye dyad model in explicit water solvation. In addition, our study probes oxygen dissociation from the RuIII-O2 intermediate, and the equilibrium dynamics of the low-valent RuIII-bda intermediate. Our simulations demonstrate that including a fraction of exact Hartree-Fock exchange impacts the electron and hole localizations in the catalyst-dye complex, which can in specific instances affect the dynamics of the system. This study contributes to a fundamental understanding of water oxidation catalysis with the Ru-bda catalyst family and highlights the relevance of modeling catalytic processes at the hybrid-DFT level.

A Lanthanum ion (La3+) incorporation strategy is implemented to modify Ba2Bi2O6-based double perovskite photoelectrodes. X-ray diffraction (XRD) characterization shows that highly crystalline Ba2La0.4Bi1.6O6 double perovskites with the space group I2/m are successfully prepared. UV-vis absorption spectra and the Tauc-plot reveal an optical band gap Eg approximate to 1.57 +/- 0.01 eV. A thickness dependence of the photoelectrodes photoelectrochemical (PEC) performance shows that the submicron (approximate to 1 mu m) 4-times spin-coated thin film photoelectrode displays strong p-type conductivity, which delivers an encouraging photocurrent density of 0.88 mA cm-2 at 0.25 VRHE under AM 1.5G illumination. 10-times coated and 20-times coated medium thick (125.8-197 mu m) photoelectrodes that exhibit moderate p-type conductivity, show further enhanced photocurrent densities of 1.5 mA cm-2 at 0 VRHE. In contrast, charge recombination centers existing in a standard thick pellet (approximate to 500 mu m) Ba2La0.4Bi1.6O6 photoelectrode can quench photo-generated charge carriers and greatly undermine PEC activities. The approach to doping at the Bi(III) sites contrasts with earlier efforts that focus on doping at the Bi(V) sites and thus paves the way for further tailoring a family of novel promising photocathode materials for efficient solar-water conversion devices.

The largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in low-light environments. Guided by NMR chemical shifts and distance constraints for Chlorobaculum tepidum wild-type chlorosomes, the two contrasting packing modes for syn-anti parallel stacks of BChl c to form polar 2D arrays, with dipole moments adding up, are explored. Layered assemblies were optimized using local orbital density functional and plane wave pseudopotential methods. The packing mode with the lowest energy contains syn-anti and anti-syn H-bonding between stacks. It can accommodate R and S epimers, and side chain variability. For this packing, a match with the available EM data on the subunit axial repeat and optical data is obtained with multiple concentric cylinders for a rolling vector with the stacks running at an angle of 21° to the cylinder axis and with the BChl dipole moments running at an angle ß ∼ 55° to the tube axis, in accordance with optical data. A packing mode involving alternating syn and anti parallel stacks that is at variance with EM appears higher in energy. A weak cross-peak at -6 ppm in the MAS NMR with 50 kHz spinning, assigned to C-181, matches the shift of antiparallel dimers, which possibly reflects a minor impurity-type fraction in the self-assembled BChl c.

Ta5+-doped Ba2Bi2-xTaxO6 (0.2 <= x <= 0.8) double perovskites are synthesized by a soft chemical sol-gel method. X-ray diffraction (XRD) results show the formation of a double perovskite structure. Systematic shifts of Bragg diffraction peaks to larger angles confirm the incorporation of increasing amounts of Ta5+ dopant ions in the Ba2Bi2O6 (BBO) crystal lattice. The optical absorption spectra and Tauc plots reveal a monotonic increase of the optical band gaps for Ba2Bi2-xTaxO6 (0.2 <= x <= 0.8) from 1.5 to 2.3 eV. Photoelectrochemical (PEC) and electrochemical tests signify the advantages of doping Ta5+ in improving the photoelectrode resistance to electrochemical corrosion. Highly reversible ambipolar photocurrents are observed for photoelectrodes with x >= 0.4 that can be further enhanced by anodic or cathodic poling treatment for facilitated interface photocharge injection. Ba2Bi1.6Ta0.4O6 photoelectrodes exhibit both the highest cathodic photocurrent of 65.5 mu A cm(-2) at 0 V-RHE with an onset potential of 1.43 V-RHE, and the highest anodic photocurrent of 37 mu A cm(-2) at 2 V-RHE with an onset potential of 1.03 V-RHE among other Ta5+ containing counterpart samples. The deteriorating PEC photocurrents of photoelectrodes with x >= 0.5 are the result of both inferior light absorption ability due to large band gaps and lower charge carrier concentrations due to defect compensation. The understanding and control of this switchable-photocurrent phenomenon by doping strategies are significant to further tailor the electronic band structure for compatible homojunctions of BBO-based double perovskites.

Zebrafish (Danio rerio) is an important animal model for a wide range of neurodegenerative diseases. However, obtaining the cellular resolution that is essential for studying the zebrafish brain remains challenging as it requires high spatial resolution and signal-to-noise ratios (SNR). In the current study, we present the first MRI results of the zebrafish brain at the state-of-the-art magnetic field strength of 28.2 T. The performance of MRI at 28.2 T was compared to 17.6 T. A 20% improvement in SNR was observed at 28.2 T as compared to 17.6 T. Excellent contrast, resolution, and SNR allowed the identification of several brain structures. The normative T1 and T2 relaxation values were established over different zebrafish brain structures at 28.2 T. To zoom into the white matter structures, we applied diffusion tensor imaging (DTI) and obtained axial, radial, and mean diffusivity, as well as fractional anisotropy, at a very high spatial resolution. Visualisation of white matter structures was achieved by short-track track-density imaging by applying the constrained spherical deconvolution method (stTDI CSD). For the first time, an algorithm for stTDI with multi-shell multi-tissue (msmt) CSD was tested on zebrafish brain data. A significant reduction in false-positive tracks from grey matter signals was observed compared to stTDI with single-shell single-tissue (ssst) CSD. This allowed the non-invasive identification of white matter structures at high resolution and contrast. Our results show that ultra-high field DTI and tractography provide reproducible and quantitative maps of fibre organisation from tiny zebrafish brains, which can be implemented in the future for a mechanistic understanding of disease-related microstructural changes in zebrafish models of various brain diseases.

Toll-like receptor 2 (TLR2) belongs to the TLR protein family that plays an important role in the immune and inflammation response system. While TLR2 is predominantly expressed in immune cells, its expression has also been detected in the brain, specifically in microglia and astrocytes. Recent studies indicate that genomic deletion of TLR2 can result in impaired neurobehavioural function. It is currently not clear if the genomic deletion of TLR2 leads to any alterations in the microstructural features of the brain. In the current study, we noninvasively assess microstructural changes in the brain of TLR2-deficient (tlr2-/-) zebrafish using state-of-the art magnetic resonance imaging (MRI) methods at ultrahigh magnetic field strength (17.6 T). A significant increase in cortical thickness and an overall trend towards increased brain volumes were observed in young tlr2-/- zebrafish. An elevated T2 relaxation time and significantly reduced apparent diffusion coefficient (ADC) unveil brain-wide microstructural alterations, potentially indicative of cytotoxic oedema and astrogliosis in the tlr2-/- zebrafish. Multicomponent analysis of the ADC diffusivity signal by the phasor approach shows an increase in the slow ADC component associated with restricted diffusion. Diffusion tensor imaging and diffusion kurtosis imaging analysis revealed diminished diffusivity and enhanced kurtosis in various white matter tracks in tlr2-/- compared with control zebrafish, identifying the microstructural underpinnings associated with compromised white matter integrity and axonal degeneration. Taken together, our findings demonstrate that the genomic deletion of TLR2 results in severe alterations to the microstructural features of the zebrafish brain. This study also highlights the potential of ultrahigh field diffusion MRI techniques in discerning exceptionally fine microstructural details within the small zebrafish brain, offering potential for investigating microstructural changes in zebrafish models of various brain diseases.

Leptin is a hormone that plays a key role in controlling food intake and energy homeostasis. Skeletal muscle is an important target for leptin and recent studies have shown that leptin deficiency may lead to muscular atrophy. However, leptin deficiency-induced structural changes in muscles are poorly understood. The zebrafish has emerged as an excellent model organism for studies of vertebrate diseases and hormone response mechanisms. In this study, we explored ex-vivo magnetic resonance microimaging (μMRI) methods to non-invasively assess muscle wasting in leptin-deficient (lepb-/-) zebrafish model. The fat mapping performed by using chemical shift selective imaging shows significant fat infiltration in muscles of lepb-/- zebrafish compared to control zebrafish. T2 relaxation measurements show considerably longer T2 values in the muscle of lepb-/- zebrafish. Multiexponential T2 analysis detected a significantly higher value and magnitude of long T2 component in the muscles of lepb-/- as compared to control zebrafish. For further zooming into the microstructural changes, we applied diffusion-weighted MRI. The results show a significant decrease in the apparent diffusion coefficient indicating increased constraints of molecular movements within the muscle regions of lepb-/- zebrafish. The use of the phasor transformation for the separation of diffusion-weighted decay signals showed a bi-component diffusion system which allows us to estimate each fraction on a voxel-wise basis. A substantial difference was found between the ratio of two components in lepb-/- and control zebrafish muscles, indicating alterations in diffusion behavior associated with the tissue microstructural changes in muscles of lepb-/- zebrafish as compared to control zebrafish. Taken together, our results demonstrate that the muscles of lepb-/- zebrafish undergo significant fat infiltration and microstructural changes leading to muscle wasting. This study also demonstrates that μMRI provides excellent means to non-invasively study the microstructural changes in the muscles of the zebrafish model.

A thorough understanding of the proton-coupled electron transfer (PCET) steps that are involved in photocatalytic water oxidation is of crucial importance in order to increase the efficiency of dye-sensitized photoelectrochemical cells (DS-PEC) for solar to fuel conversion. This work provides a computational investigation of the ground and excited state potential energy surfaces of PCET reactions in two supramolecular dye-catalyst complexes for photocatalytic water splitting. The intrinsic reaction coordinate path is computed for the rate limiting PCET step in the catalytic cycle for both complexes. By using time-dependent density functional theory calculations, we show that the ground and excited state potential energy surfaces have a (near) degeneracy in the region of the PCET transition state. We discuss two possible strategies that take advantage of this feature to accelerate the PCET reaction: (i) through optimizing the conditions for vibronic coupling by chemical design and synthesis or (ii) through populating the product state with appropriately tuned laser pulses.

The antenna complex of green sulfur bacteria, the chlorosome, is one of the most efficient supramolecular systems for efficient long-range exciton transfer in nature. Femtosecond transient absorption experiments provide new insight into how vibrationally induced quantum overlap between exciton states supports highly efficient long-range exciton transfer in the chlorosome of Chlorobium tepidum. Our work shows that excitation energy is delocalized over the chlorosome in <1 ps at room temperature. The following exciton transfer to the baseplate occurs in ∼3 to 5 ps, in line with earlier work also performed at room temperature, but significantly faster than at the cryogenic temperatures used in previous studies. This difference can be attributed to the increased vibrational motion at room temperature. We observe a so far unknown impact of the excitation photon energy on the efficiency of this process. This dependency can be assigned to distinct optical domains due to structural disorder, combined with an exciton trapping channel competing with exciton transfer toward the baseplate. An oscillatory transient signal damped in <1 ps has the highest intensity in the case of the most efficient exciton transfer to the baseplate. These results agree well with an earlier computational finding of exciton transfer driven by low-frequency rotational motion of molecules in the chlorosome. Such an exciton transfer process belongs to the quantum coherent regime, for which the Förster theory for intermolecular exciton transfer does not apply. Our work hence strongly indicates that structural flexibility is important for efficient long-range exciton transfer in chlorosomes.

Chlorosomes from green bacteria perform the most efficient light capture and energy transfer, as observed among natural light-harvesting antennae. Hence, their unique functional properties inspire developments in artificial light-harvesting and molecular optoelectronics. We examine two distinct organizations of the molecular building blocks as proposed in the literature, demonstrating how these organizations alter light capture and energy transfer, which can serve as a mechanism that the bacteria utilize to adapt to changes in light conditions. Spectral simulations of polarization-resolved two-dimensional electronic spectra unravel how changes in the helicity of chlorosomal aggregates alter energy transfer. We show that ultrafast anisotropy decay presents a spectral signature that reveals contrasting energy pathways in different chlorosomes.