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Immobilisation of Ni(II) and Zr(IV) metal-organic frameworks on electrodes using electrophoretic deposition
No full textMetal-organic frameworks are materials which are constituted by an inorganic centre and organic
ligand offering high crystallinity, high surface area and high permanent porosity. These structures
show promising results in multiple applications due to their properties, especially their capacity
for open-metal sites. The use of these structures for electrochemical applications, such as sensors
and electrocatalysts, require their immobilisation on a conductive surface, as they are obtained in
powder form using the most common method – solvothermal synthesis. Electrophoretic
deposition, an indirect method, which focus on immobilising these materials in powder form postsynthesis on the surface of a conductive structure can be used for their immobilisation, that may
offer several advantages in relation with other methods if further developed – those being
simplicity and universality. This work focuses on the synthesis, immobilisation, and stability
studies of these MOFs in the presence of water and in oxidative aqueous electrochemical medium.
The obtained metal-organic framework powders and films were characterised using X-rays
diffraction, Fourier Transform infrared spectroscopy and scanning-electron microscopy. The
electrochemical studies were made using cyclic voltammetry. It was possible to form films of the
MOFs UiO-66, UiO-66-NH2 and Ni-MOF-74 on the surface of fluoride-doped tin oxide glass
using electrophoretic deposition, with all three MOF films showing stability in water and the UiO-
66 and UiO-66-NH2 films showing high stability as well in highly basic oxidative aqueous
electrochemical medium
Operando Photoelectron Spectroscopy Analysis of Li6PS5Cl Electrochemical Decomposition Reactions in Solid-State Batteries
No full textMost solid electrolytes (SEs) which are promising for all-solid-state battery (ASSB) applications are known to have a narrow electrochemical stability window. Consequently, parasitic electrolyte reactions are observed when high-energy-density electrode materials such as lithium and silicon are employed, hindering their utilization in commercial battery systems. Therefore, it is crucial to understand at which potentials such reactions start, and which chemical species are present in the subsequently formed solid electrolyte interphase (SEI). Herein, a new operando experimental approach is introduced to investigate such reactions by employing hard X-ray photoelectron spectroscopy (HAXPES). This approach enables the examination of the SEI formed below a thin metal film (e.g., 6 nm nickel) acting as the working electrode. The feasibility of this approach is demonstrated using a sulfide-based Li6PS5Cl solid electrolyte (lithium argyrodite). It is shown that electrolyte reduction reactions start upon polarization of the working electrode to voltages below 1.75 V (vs. Li+/Li) and result in considerable Li2S formation, particularly in the voltage range of 1.5 – 1.0 V. The overall intensity trends confirm the heterogeneous/layered microstructure of the SEI (e.g., preferential Li2O and Li2S deposition near the current collector). The reversibility of side reactions is also observed, as Li2O and Li2S decompose in the 2–4 V potential window, generating oxidized sulfur species, sulfites and sulfates. The introduced experimental approach is promising for the spectroscopic investigation of electrolyte side reactions under dynamic conditions for various solid electrolyte and current collector combinations
Moiré Superlattices of Zn2+ Mediated 2D Assembly of Mn2+-Cysteine Complex Nanoparticles Alter Electron Spin Transitions in the X-band
No full textAmbient reaction-mediated assembly of cysteine-based nanoparticles of Mn complex, and Zn2+ ion led to the generation of moiré patterns in 2D films. Individually formed crystalline 2D films made of manganese cysteine complex nanoparticles and Zn2+ ions were stacked angularly against each other giving rise to the moiré films. Selected area electron diffraction patterns revealed a wide range of twist angles. Circular dichroism peaks appearing at 480 nm, 513 nm, and 643 nm; representing moiré chirality were observed irrespective of the chiral identity of the constituent ligand. The moiré films were constituted of two chemically different types of Mn2+ ions as revealed by electron spin resonance (ESR) spectroscopy. The ESR signal of Mn2+ ion was found to have been altered upon formation of the moiré films as a result of the prevalent interfacial magnetic field of the individual 2D films. The current work focuses on the generation of self-assembled moiré materials of manganese cysteine nanoparticles by Zn2+ ion and the influence of so formed moiré pattern on the chemical environment of the Mn2+ ions. The discovery of inorganic complex nanoparticle-based moiré material can offer structural, physical, and chemical diversity to materials science
Machine Learning in Complex Organic Mixtures: Applying Domain Knowledge Allows for Meaningful Performance with Small Datasets.
No full textThe ability to quantify individual components of complex mixtures is a challenge found throughout the life and physical sciences. An improved capacity to generate large datasets along with the uptake of machine-learning (ML) based analysis tools has allowed for various ‘omics’ disciplines to realize exceptional advances. Other areas of chemistry that deal with complex mixtures often cannot leverage these advances. Environmental samples, for example, can be more difficult to access and the resulting small datasets are less appropriate for unconstrained ML approaches. Herein, we present an approach to address this latter issue. Using a very small environmental dataset—35 high-resolution mass spectra gathered from various solvent extractions of Canadian petroleum fractions—we show that the application of specific domain knowledge can lead to ML models with notable performance
Molecular Beam Scattering from Flat Jets of Liquid Dodecane and Water
No full textMolecular beam experiments in which gas molecules are scattered from liquids provide detailed, microscopic perspectives on the gas–liquid interface. Extending these methods to volatile liquids while maintaining the ability to measure product energy and angular distributions presents a significant challenge. The incorporation of flat liquid jets into molecular beam scattering experiments in our laboratory has allowed us to demonstrate their utility in uncovering dynamics in this complex chemical environment. Here, we summarize recent work on the evaporation and scattering of Ne, CD4, ND3, and D2O from a dodecane flat liquid jet and present first results on the evaporation and scattering of Ar from a cold salty water jet. In the evaporation experiments, Maxwell–Boltzmann flux distributions with a cosθ angular distribution are observed. Scattering experiments reveal both impulsive scattering and trapping followed by thermal desorption. Super-specular scattering is observed for all four species scattered from dodecane and is attributed to anisotropic momentum transfer to the liquid surface. In the impulsive scattering channel, rotational excitation of the polyatomic scatterers is a significant energy sink, and these species accommodate more readily on the dodecane surface compared to Ne. Our preliminary results on cold salty water jets suggest that Ar atoms undergo vapor-phase collisions when evaporating from the liquid surface. Initial scattering experiments characterize the mechanisms of Ar interacting with an aqueous jet, allowing for comparison to dodecane systems
Study of Synthesis , Characterisation and Photocatalytic degradation of Methyl orange using Copper Nanoparticles derived from roots of Averrhoa carambola.
No full textPhotocatalytic degradation using metal nanoparticles is one of the most preferred method to eradicate water contamination mainly caused due to toxic azo dyes. In this study, synthesis of Copper nanoparticles(CuNP’s) is mainly discussed using aqueous extract of roots of Averrhoa carambola. Purpose of this study is to scientifically investigate photocatalytic efficacy of CuNP’s. Synthesised CuNP’s showed maximum wavelength at 278 nm after 30 minutes of synthesis. Fourier Tranform Infrared (FTIR) Spectroscopy results are obtained giving functional groups responsible in formation of CuNP’s. Field Emission Gun -Scanning Electron Microscopy (FEG-SEM) showed particle sizes in the range of 32.8 nm, 33.8 nm, 38.5 nm and 47.8 nm for CuNP’s .Whereas, Energy dispersive X-Ray spectroscopy (EDS) technique also determined presence and composition of synthesised CuNP’s formed. Futher , its photocatalytic efficacy is highlighted against degradation of Methyl orange. To summarise, in this study green CuNP’s proved to be an efficient nanocatalyst with 93.91 % degradation of methyl orange in six minutes
A method to identify small molecule/protein pairs susceptible to protein ubiquitination
No full textAlthough using DNA encoded libraries (DELs) to find small molecule binders of target proteins is well-established, identifying DEL hits for functions other than binding remains challenging. We demonstrate here a technique where pools of DNA-linked small molecules are mixed with pools of DNA-linked protein targets and optimal small/protein pairs are identified based on their ability to catalyze the transfer of ubiquitin (Ub) onto the target proteins. Since the transfer of Ub is the first step in the tagging of proteins for proteasomal destruction, finding small molecules that can selectively reprogram Ub-transfer is one of the great challenges in contemporary drug development. Our work provides the framework for a new type of functional DEL screen that matches small molecule Ub-transfer catalysts with their optimal protein substrates. We believe the technology could be especially useful in discovering and optimizing molecular glue degraders
Ultrafast dynamics of fluorene initiated by highly intense laser fields
No full textWe present an investigation of the ultrafast dynamics of the polycyclic aromatic hydrocarbon fluorene initiated by an intense femtosecond near- infrared laser pulse (810 nm) and probed by a weak visible pulse (405 nm). Using a multichannel detection scheme (mass spectra, electron and ion velocity-map imaging), we provide a full disentanglement of the complex dynamics of the vibronically excited parent molecule, its excited ionic states, and fragments. We observed various channels resulting from the strong-field ionization regime. In particular, we observed the formation of the unstable tetracation of fluorene, above-threshold ionization features in the photoelectron spectra, and evidence of ubiquitous secondary fragmentation. We produced a global fit of all observed time-dependent photoelectron and photoion channels. This global fit includes four parent ions extracted from the mass spectra, 15 kinetic-energy-resolved ionic fragments extracted from ion velocity map imaging, and five photoelectron channels obtained from electron velocity map imaging. The fit allowed for the extraction of 60 lifetimes of various metastable photoinduced intermediates
Predicting Reactivity and Passivation of Solid-State Battery Interfaces
No full textIn this work, we build a computationally inexpensive, data-driven model that utilizes only atomistic structure information to predict the reactivity of interfaces between any candidate solid-state electrolyte material and a Li metal anode. This model is trained on data from ab initio molecular dynamics (AIMD) simulations of the time evolution of the solid electrolyte-Li metal interface for 67 different materials. Predicting the reactivity of solid state interfaces with ab initio techniques remains an elusive challenge in materials discovery and informatics, and previous work on predicting interfacial compatibility of solid-state Li-ion electrolytes and Li metal anodes has focused mainly on thermodynamic convex hull calculations. Our framework involves training machine learning models on AIMD data, thereby capturing information on both kinetics and thermodynamics, and then leveraging these models to predict the reactivity of thousands of new candidates in the span of seconds, avoiding the need for additional weeks-long AIMD simulations. We identify over 300 new chemically stable and over 780 passivating solid-electrolytes that are predicted to be thermodynamically unfavored. Our results indicate many potential solid-state electrolyte candidates have been incorrectly labeled unstable via purely thermodynamic approaches using density functional theory (DFT) energetics, and that the pool of promising, Li-stable solid-state electrolyte materials may be much larger than previously thought from screening efforts. To showcase the value of our approach, we highlight two borate materials that were identified by our model and confirmed by further AIMD calculations to likely be highly conductive and chemically stable with Li: LiB13C2 and LiB12PC
From Digital Blueprint to Chemical Reality: Methanol to Formaldehyde at Ambient Conditions
No full textPartial oxidation of methanol to value added product presents an intriguing yet challenging process. Among these products, formaldehyde is the simplest and one of the most vital aliphatic aldehydes, which has extensive application across various domains. Industrially, silver and iron-molybdenum oxides are used as catalysts for the conversion of methanol to formaldehyde at elevated temperatures (600 ◦ C and 250-400 ◦ C, respectively). However, in this computational and experimental study, we have demonstrated the efficacy of ZnO as a catalyst. Notably, in the presence of ZnO, methanol readily converts to formaldehyde even under ambient conditions. We employed periodic density functional theory (DFT) to explore (1011) facet of ZnO to elucidate its inter- action with methanol. Our comprehensive analysis identified the most active facet (1011) involved in the spontaneous conversion of methanol to formaldehyde. Subsequently, experimental validation supported our theoretical findings, demonstrating the conversion of methanol to formaldehyde with 100% selectivity at room temperature and atmospheric pressure in the presence of ZnO. This study exemplifies the pivotal role of theory in catalyst design