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Experimental benchmarking of relative potential energy minima internuclear distances with femtometer length accuracy
Get PDFThe two dimensional photon excitation photon emission PhexPhem map of the archetypal H2 molecule, constructed from dispersed fluorescence measurements after energy scanning excitation by small bandwidth photons, displays complete systems of its Condon diffraction bands. They originate from spontaneous radiative dissociation of individual bound electronically excited rovibronic levels, one of the most relevant processes for the destruction of H2 in space. For the amp; 119861; amp; 8722; amp; 119883; system of electronic states, we show that specific measured spectral characteristics of individual bands are extremely sensitive to the difference amp; 916; amp; 8290; amp; 119877; of the internuclear distances, where the two potential energy curves each have their minimum. Using data from recorded H2 PhexPhem maps, it is possible to experimentally validate the calculations of amp; 916; amp; 8290; amp; 119877; down to an accuracy of at least 50 amp; 8290;f amp; 8289;m. This accuracy may be used as a sensitive experimental test to calculational accuracy. It is well feasible to improve the currently achieved experimental accuracy, for an even more accurate benchmark of advanced potential energy curve calculation
Unveiling the Impact of C60 O2 Interaction on the Performance and Characterization of Perovskite Solar Cells
Get PDFC60 is the prevalent electron transport layer ETL in high efficiency p i n perovskite single junction and multi junction solar cells. Here, it is demonstrated that the exposure of the C60 ETL to ambient O2 results in significantly increased non radiative recombination, influencing results from commonly applied characterization techniques such as steady state and transient photoluminescence PL , transient surface photovoltage, as well as current density voltage measurements. Based on PL and He I UV photoemission spectroscopy measurements and supported by density functional theory calculations and drift diffusion simulations, it is proposed that O2 rapidly intercalates into the C60 ETL, causing the formation of deep trap states and an altered charge carrier balance at the perovskite C60 interface. The findings reveal that the effect is reversible but can mislead experimental interpretations if disregarded, emphasizing the importance of O2 management during device fabrication and characterization. Furthermore, it is demonstrated that this interaction enables simple PL measurements in air to serve as a novel sensing method for evaluating the barrier layer quality of the SnOx buffer layer atop C60. This study thereby not only highlights a critical deterioration mechanism in perovskite solar cells and provides a deeper understanding of the underlying interaction between the C60 ETL and O2 but also offers practical avenues for future selective contact optimization
Automated Investigation of Metal Ligand Interactions by a Newly Established Robotic Workflow for Titrations
Get PDFIn this work, we present a new workflow to set up an automated platform for the investigation of metal complex formation in solutions. With the utilization of this robot titration platform, the generation of an abundancy of solvated metal complexes in differing coordination number is possible in a simple manner. The generated complexes can subsequently be sampled into differing vessels to examine them in detail. We present sampling for UV Vis and NMR spectroscopy at chosen model systems, however, the platform can easily be adapted to provide samples for other techniques, e. g., for infrared spectroscop
Mild Oxidation of Plant Polyphenols Yields Modular Nanoparticle Forming Materials with Drug Loading Capabilities
No full textPlant polyphenols have attracted interest as green precursors for functional materials due to their unique chemical features. Here, an approach to formulate nanoparticles NPs from a hydrophobic quercetin; QCT and a hydrophilic tannic acid; TA polyphenol, by leveraging their propensity for oxidation, is presented. QCT and TA are partially oxidized to form oxQCT and oxTA, respectively. The materials are subsequently used to formulate NPs by nanoprecipitation alone or in the presence of hydrophilic and amphiphilic polymers. Characterization of oxQCT reveals a notable chemical change and increased thermal stability, with reduced antioxidant and anti inflammatory activities compared to unmodified QCT. Conversely, oxTA shows an insignificant change in chemistry compared to pristine TA, yet it displays greater thermal stability, reduced antioxidant activity, and altered anti inflammatory activity. Particle size and morphology of the formulated NPs are examined by dynamic light scattering DLS , analytical ultracentrifugation AUC , and transmission electron microscopy TEM . The results indicate that co formulating oxQCT and oxTA with different polymers impacts their particle size, polydispersity index, and morphology. Lastly, oxQCT and oxTA co formulated with other polymers are capable of loading hydrophobic drugs such as amphotericin B and curcumin, forming sub 200 nm NPs with high loading efficiencies, which validates their use in drug delivery system
Multifunctional Chitosan Covalent Bonded Multi Walled Carbon Nanotubes Composite Binder for Enhanced Electrochemical Performances of Lithium Sulfur Batteries
Get PDFLithium sulfur batteries LSBs are considered as one of the most promising next generation energy storage devices because of their high energy density. However, the long term use of LSBs is mainly limited by polysulfide shuttling and cathode structural degradation caused by volume changes during charging and discharging. To address these issues, a multifunctional, high performance aqueous binder is developed by modifying a natural polysaccharide with multi walled carbon nanotubes MWCNTs . Specifically, the catechol conjugated chitosan CCS acts as the binder, showing strong polysulfide adsorption, while the MWCNTs covalently bonded to CCS enhance the mechanical toughness and electronic conductivity. The resulting CCS MWCNTs composite binder exhibits a tensile strength of 40 MPa and a strain at break of 300 , which are higher than those of CCS. As a binder for sulfur cathodes, the CCS MWCNTs binder demonstrates superior cyclic stability and rate capability. At a sulfur loading of 2.0 mg cm 2, it delivers an initial capacity of 1016 mAh g 1 at 0.2 C and retains 690 mAh g 1 after 100 cycles, significantly outperforming commercial polyvinylidene difluoride PVDF , sodium carboxymethylcellulose styrene butadiene rubber CMC SBR , and CCS binders. This study demonstrates the potential applications of polysaccharide binders in metal sulfur batteries by innovatively incorporating carbon nanotubes into the biopolymer binder, providing a promising alternative for environmentally friendly energy storag
TlInP2Se6 single crystal Electronic, optical and vibrational properties
No full textWe report on successful synthesis by the Bridgman technique of a large TlInP2Se6 single crystal and studies of its electronic, optical and vibrational properties. In particular, centimeter size dimensions of the TlInP2Se6 crystal allow its practical use in optical devices. The crystal was characterized by DTA, SEM, EDS, XPS, XES techniques which reveal its high optical quality, single phase composition and stoichiometry. The present refinements of the crystal structure of TlInP2Se6 bring the following unit cell constants a 6.4494 4 , b 7.5423 5 , c 12.1669 9 , amp; 945; 100.784 4 , amp; 946; 93.622 4 , amp; 947; 113.331 3 , and V 527.8 2 3. The experimental optical reflection spectrum of the crystal was measured in the far infrared spectral range 30 500 cm amp; 8722;1 using the synchrotron radiation. Furthermore, we employed first principles computations within a density functional theory DFT formalism to elucidate peculiarities of filling the valence band and conduction band regions and the nature of semiconducting gap. The DFT calculations confirm the existing measurements that the TlInP2Se6 crystal is an indirect semiconductor maximum of the valence band and minimum of the conduction band are positioned at high symmetry F and Z points of the Brillouin zone, respectively , and the principal contributors to the valence band are Se 4p states filling mainly its top and also the bottom of the conduction band. The DFT calculations explain observed highly anisotropic properties layered structure by strong differentiation of calculated real and imaginary parts of complex dielectric function in the y direction, with relation to x and z directions for the TlInP2Se6 compound. The vibrational properties of the TlInP2Se6 crystal were also investigated both experimentally by Raman measurements and theoretically using the DFPT metho
Activation of NiFe Oxide Based OER Catalysts Iron Determines the Growth of the Catalytically Active Phase in NiO
No full textMixed nickel iron hydr oxides are nowadays the best performing alkaline O2 evolution electrocatalysts. It has been assumed that the activity of these catalysts is determined by surface species but that a conditioning of the bulk is necessary to achieve optimal performances. Only recently, research delved into the surface properties and the composition near the solid liquid interface of such catalysts. Using sputter depth profiling X ray photoelectron spectroscopy, we compared pure nickel oxides with mixed nickel iron oxides and found that electrochemical transformation to oxy hydroxides in the mixed oxide systems is limited to just a few nanometers at the surface, unlike pure nickel oxides, which transform deeper into the bulk. This suggests that non surface sensitive techniques may overlook the true active phase in mixed nickel iron oxide catalysts. Our results indicate that bulk transformation may not be essential for catalytic activity. We propose a model in which iron limits nickel oxidation and promotes charge transfer directly to the oxygen evolution reactio
Photoluminescence Degradation in Metal Halide Perovskites Is In amp; 8208;Situ Study with Concentrated Sunlight Possible?
Get PDFPhotoluminescence PL spectroscopy is a valuable tool fordegradation studies of perovskite based photovoltaic materials. The wavelength sensitive nature of the photo induced processes implies a preference for sunlight as the photo excitation source for such PL studies. This study reports on the design and experimental validation of a new setup for the in situ study of PL degradation in metal halide perovskites using concentrated natural sunlight in a wide range of solar concentrations and sample temperatures. The system allows the sample to be excited with the entire solar spectrum while successfully filtering undesired reflected sunlight using two orthogonal polarization filters. Depending on temperature and solar concentration, we observed three types of perov skite PL behavior stable PL response, without degradation; reversible PL degradation with stable ultraviolet visible light absorp tion; and nonreversible PL degradation accompanied with the variation of light absorptio
Multiphysics Modeling of Photoelectrochemical Devices for Simultaneous Solar Driven Biomass Reforming and Hydrogen Production
Get PDFBiomass reforming, including glycerol and 5 hydroxymethylfurfural oxidation, converts renewable biomass derived molecules into value added chemicals and fuels. This process is crucial for sustainable energy and chemical production, offering a carbon neutral alternative to fossil based feedstocks. Integrating biomass oxidation with photoelectrochemistry enables solar driven reactions, reducing external electrical input and improving energy efficiency. Photoelectrochemical cells selectively oxidize biomass derived compounds at the photoanode while generating hydrogen or other reduction products at the cathode, creating a synergistic system for sustainable fuel and chemical production. Electrolyte transport properties significantly impact membraneless PEC device performance. This study systematically investigates flow behavior, crossover effects, and device operation using a 0.5 M glycerol solution as the anolyte. Despite its similar density and viscosity to water, the glycerol solution exhibits density driven instabilities, leading to electrolyte mixing when paired with a pure water catholyte. Simulations reveal that using the same glycerol solution in both compartments prevents crossover and enhances stability. A single bridge design optimized to minimize iR drop while maintaining separation reduced voltage losses by 47 compared to a double bridge configuration. At flow rates amp; 8805;60 mL min, product crossover remains negligible, supporting the feasibility of membraneless PEC designs for glycerol oxidation. These findings contribute to scaling up PEC systems for sustainable hydrogen and high value added chemical production, emphasizing the potential of modular, high efficiency solar driven biomass reformin
Physics informed Bayesian optimization of expensive to evaluate black box functions
Get PDFBayesian optimization with Gaussian process surrogates is a popular approach for optimizing expensive to evaluate functions in terms of time, energy, or computational resources. Typically, a Gaussian process models a scalar objective derived from observed data. However, in many real world applications, the objective is a combination of multiple outputs from physical experiments or simulations. Converting these multidimensional observations into a single scalar can lead to information loss, slowing convergence and yielding suboptimal results. To address this, we propose to use multi output Gaussian processes to learn the full vector of observations directly, before mapping them to the scalar objective via an inexpensive analytical function. This physics informed approach retains more information from the underlying physical processes, improving surrogate model accuracy. As a result, the approach accelerates optimization and produces better final designs compared to standard implementation