ChemRxiv
Not a member yet
27047 research outputs found
Sort by
Quantum Control of Nonlinear Dynamics in Confined Fluids
No full textInvestigating nonlinear fluid dynamics remains a challenge across physics from nanofluidics and biophysics to astrophysics. Here we introduce a quantum/classical theoretical approach that takes into account both quantum correlations and classical behaviour within a 2D fluid that is confined in a 3 μm side square. We employ a modified Gross-Pitaevskii equation, encompassing many-body interactions and confinement. This system reveals complex fluid dynamics characterised by dissipative solitons; a significant outcome is an asymptotic function that describes the soliton behaviour. The solitons exhibit intriguing geometrical and temporal transformations, guided by subtle phase gradients. We trace the soliton evolution from 1 ns to 83 ns, revealing the emergence of geometric oscillations in amplitude and phase angles. Under these phase gradients, solitons transition to states with reduced amplitude and expanded spatial profiles. These results show that geometric solitons can emerge from a quantum noisy environment, and lead us to propose an interesting possibility: it is feasible to control and manipulate nonlinear dynamics in systems with finite-range interactions and confinement using quantum control. By bridging quantum and classical dynamics, this study links various scientific disciplines, including non-equilibrium phases of condensed matter, unconventional/quantum computing and advanced control of nanofluidics. From a more fundamental perspective, this possibility of quantum control of classical behaviour advances our understanding of physics within multidimensional Hilbert spaces
Temporal Analysis of Products (TAP) Reactor Study of the Dynamics of CO2 Interaction with a Ru/g-Al2O3 Supported Catalyst II: Interaction Strength, Formation of Intermediates and Oxygen Exchange
No full textContinuing a comprehensive study of the reduction of COx over supported Ru catalysts, we explored the interaction of CO2 with Ru/g-Al2O3 by TAP reactor measurements, focusing on dynamic aspects in adsorption/desorption, reaction and oxygen exchange processes. Pulse shape analysis in H2/CO2 multipulse sequences provides information on the interaction of reactant/product species with the catalyst. The measurements provide information on the dynamic build-up of reaction intermediates and more stable adspecies during pulsing, and its relation to CH4 formation. Facile oxygen exchange between CO2 and catalyst, followed by isotope labelling experiments, is quantitatively reconciled in a simple model, relating the ratio between different CO2 isotopologues to the 18O : 16O ratio in the total exchangeable oxygen on the surface and in the CO2 pulse. The results provide detailed insight into various aspects of the interaction between CO2 and Ru/Al2O3 catalysts important for a mechanistic understanding of various catalytic reactions involving CO2
The iron-catalysed Suzuki coupling of aryl chlorides
No full textA simple iron-based catalyst with an N-heterocyclic carbene ligand can be used to excellent effect in the previously unknown Suzuki biaryl coupling of aryl chloride substrates with aryl boronic esters activated by an organolithium reagent. Mechanistic studies suggest the possible involvement of Fe(I) as the lowest oxidation state on the catalytic manifold and show that the challenging step is not activation of the aryl chloride substrate, but rather the transmetallation step. These findings are likely to pave the way for a renaissance of iron-catalysed carbon-carbon bond-forming transformations with ‘soft’ nucleophilic coupling partners
Flexible Electrochemical Stripping for Wastewater Ammonia Recovery with Real-Time Product Tunability
No full textNitrogen in wastewater can be recovered to prevent negative environmental, human health, and economic impacts and to enable distributed chemical manufacturing. We developed novel flexible electrochemical stripping (FECS) for tunable recovery of ammonia/ammonium (total ammonia nitrogen, TAN) from urine as ammonium sulfate and aqueous ammonia. Batch and continuous experiments demonstrated that product speciation could be readily controlled by modifying electrochemical cell operation frequency, duration, and applied current without affecting TAN removal. During continuous experiments, FECS recovered ammonia solutions with concentrations similar to ready-to-use cleaners (1% and 2% aqueous ammonia (w/w) or 8.22 and 16.4 g/L TAN) and cleaner concentrates (5% aqueous ammonia (w/w) or 41.1 g/L TAN), as well as ammonium sulfate solutions between 5 and 18.4 g/L TAN, approaching commercial fertilizer concentrations (28.4 g/L TAN). Beyond modifying applied current, future process engineering and operating condition optimization should reduce energy consumption, increase recovery efficiency, and enhance economic viability of FECS. Our findings will enable development and deployment of electrochemical nitrogen recovery in contexts with varying needs for ammonia-based products, paving the way for circular economies that integrate distributed chemical manufacturing with sanitation systems
Programming Fluid Motion Using Multi-Enzyme Micropump Systems
No full textIn the presence of appropriate substrates, surface-anchored enzymes can act as pumps and propel fluid through microchambers. Understanding the dynamic interplay between catalytic reactions and fluid flow is vital to enhancing the accuracy and utility of flow technology. Through a combination of experimental observations and numerical modelling, we show that coupled enzyme pumps can exhibit flow enhancement, flow suppression, and changes in the directionality (reversal) of the fluid motion. The pumps’ ability to regulate the flow path is due to the reaction selectivity of the enzymes; the resultant fluid motion is only triggered by the presence of certain reactants. Hence, the reactants and the sequence in which they are present in the solution, and the layout of the enzyme-attached patches form an “instruction set” that guides the flowing solution to specific sites in the system. Such systems can operate as sensors that indicate concentrations of reactants through measurement of the trajectory along which the flow demonstrates maximal speed. The performed simulations suggest that the solutal buoyancy mechanism causes fluid motion and is responsible for all the observed effects. More broadly, our studies provide a new route for forming self-organizing flow systems that can yield fundamental insight into non-equilibrium, dynamical systems
Modular, Atroposelective Total Synthesis of Micitide 982
No full textA modular, atroposelective total synthesis of micitide 982 (1) is reported. The feature of this report is the gram-scale C-H biarylation of N-phthaloyl-L-alanine followed by atroposelective Larock macrocyclization. This modular approach allowed the construction of a highly strained atrop-Tyr-Trp cross-linkage with unprecedented atropisomerism, as well as the first total synthesis of micitide 982 (1)
Quantum dot-based FRET nanosensors for Talin-membrane assembly and mechanosensing
No full textUnderstanding the mechanisms of assembly and disassembly of macromolecular structures in cells relies on solving biomolecular interactions. However, those interactions often remain unclear because tools to track molecular dynamics are not sufficiently resolved in time or space. In this study, we present a straightforward method for resolving inter- and intra- molecular interactions in cell adhesive machinery, using quantum dot (QD) based Förster resonance energy transfer (FRET) nanosensors. Using mechanosensitive protein Talin, one of the major components of focal adhesions, we are investigating mechanosensing ability of proteins to sense and respond to mechanical stimuli. First, we quantified the distances separating Talin and a giant unilamellar vesicle membrane for three Talin variants. These variants differ in molecular length. Second, we investigated the mechanosensing capabilities of Talin, i.e., its conformation changes due to mechanical stretching initiated by cytoskeleton contraction. Our results suggest that in early focal adhesion, Talin undergoes stretching, corresponding to a decrease in the Talin-membrane distance of 2.5 nm. We demonstrate that QD-FRET nanosensors can be applied for the sensitive quantification of mechanosensing with sub-nanometer accuracy
Systematic and unbiased pathway exploration by artificial force application to a generic neural network potential
No full textComputational pathway exploration can unravel complex catalytic mechanisms and even predict unexplored catalytic reactions when performed in a fully systematic and unbiased manner. However, such a comprehensive exploration typically requires years of computation or thousands of CPU cores even for small systems. Herein, a generic neural network potential (NNP) trained on a large structure–energy database and force- and kinetics-based pathway exploration algorithm were combined without any tuning. An interface code was developed to combine the NNP in the Matlantis platform with the search algorithm in the GRRM software. The combined approach automatically generated comprehensive pathway ensembles containing over 10,000 local minimum structures for methane oxidation on the Pd(111) and Pd(100) surfaces with reasonable computational effort. The kinetically most plausible mechanism derived from the ensemble was qualitatively consistent with that obtained by density functional theory. These results highlight the considerable predictive power of the proposed approach at low computational cost
Preserving Precise Choreography of Bonds in Stereoretentive Olefin Metathesis: New Type of Ligand Allows High Z-Selectivity Even at Elevated Temperature
No full textThe Z-alkene geometry is prevalent in various chemical compounds, including numerous building blocks, fine chemicals, and natural products. Unfortunately, established Mo, W, and Ru Z‑selective catalysts lose their selectivity at high temperatures required for industrial processes like reactive distillation, which limits their synthetic applications. To address this issue, we developed a catalyst capable of providing Z-alkenes with high selectivity under harsh conditions. Our research revealed a novel dithiolate ligand that, stabilised by resonance, delivers high selectivity at temperatures up to 150 °C in concentrated mixtures. This distinguishes the dithioquinoxaline complex from existing Z-selective catalysts. Notably, this unique trait does not compromise the new catalyst’s usability under classical conditions, matching the activity of known stereoretentive catalysts. Density Functional Theory (DFT) calculations were employed to understand the reaction mechanism and selectivity, and to investigate the poisoning that the catalyst may undergo and how it competes with catalytic activity. Furthermore, the new quinoxaline-based catalyst enables the valorisation of bio-sourced alkene feedstocks and the production of agricultural sex pheromones for pest control
In situ neutron reflectometry reveals the interfacial microenvironment driving electrochemical ammonia synthesis
No full textElectrified interfaces are critical to the performance of energy systems and often demonstrate substantial complexity under operating conditions. Nanoscale understanding of the interfacial microenvironment, i.e., the solid electrolyte interphase (SEI), in lithium-mediated nitrogen reduction (Li-N2R) is key for realizing efficient ammonia production. Using in situ neutron reflectometry, we found the Li-N2R SEI comprises a thick, diffuse outer layer and a thin, compact inner layer at low current cycling. Increasing current density resulted in a thinner outer layer with a thicker inner layer; sustained current led to LiH formation. Neutron absorption indicated boron uptake in the SEI. Time-resolved tracking of SEI growth with isotope contrasting revealed the proton donor modifies the inner layer, and the solvent modifies the outer layer. Li dendritic growth was observed in the absence of a proton donor. Our results inform Li-based systems and reaction microenvironments, and these methods can be applied broadly to interfacial energy technologies