Chemistry methods : new approaches to solving problems in chemistry最新文献

A generalizable and versatile microfluidic approach for facile synthesis of a wide range of metal oxide microparticles using atypical metal-organic precursors is reported. Microparticles of three single oxide materials, zinc(II) oxide, tin(IV) oxide, and cerium(IV) oxide, as well as a binary rare earth mixed oxide, lanthanum(III) praseodymium(III) oxide, are synthesized in flow. The tin(IV) oxide is shown to vary in composition from 14.2 % to 0 % orthorhombic phase at annealing temperatures ranging from 500 °C to 900 °C, while the lanthanum(III) praseodymium(III) oxide forms at a relatively low temperature of ∼700 °C.

Invited for this month's cover are the groups of Alec M. Wodtke at the Georg-August University in Göttigen (Germany) and at the University of Crete (Greece). The cover picture shows ammonia (NH₃) molecules adsorbed on an atomically flat platinum surface. An ultra-short laser pulse hits the surface and heats up the metal electron rapidly to several thousand Kelvin within a few 100 fs. This high electronic temperature causes a fraction of the ammonia molecules to desorb with hyperthermal velocity from the surface. Depended on the laser intensity, the number of desorbing molecules is proportional to the surface coverage. Read the full text of their Research Article at 10.1002/cmtd.202200017.

The Front Cover shows ammonia molecules adsorbed on an atomically flat platinum surface. An ultra-short laser pulse hits the surface and heats up the metal electron rapidly to several thousand Kelvin within a few 100fs. This high electronic temperature causes a fraction of the ammonia molecules to desorb with hyperthermal velocity from the surface. More information can be found in the Research Article by Kim Pappendorf et al..

A novel application to determine stability constants from supramolecular titration experiments is presented. The focus lies on NMR titration and ITC experiments for pure 1 : 1 systems, as well as mixed 2 : 1/1 : 1, 1 : 1/1 : 2 and 2 : 1/1 : 1/1 : 2 systems. SupraFit provides global and local fitting and a global search tool. Statistical methods are implemented and can be applied to analyse the results of nonlinear regression. Monte Carlo simulations, combined with the percentile methods and F-Test approaches to calculate confidence intervals are supported. The implemented statistical approaches are illustrated and discussed on model functions. All methods are accessible through an intuitive user interface, providing charts for all (kind of) data produced. SupraFit is written in C++, using the Qt Toolkit for the Graphical User Interface (GUI) and the Eigen library for nonlinear regression and is released under the GNU Public License (GPL).

Reproducibility is at the heart of science. However, most published results usually lack the information necessary to be independently reproduced. Even more, most authors will not be able to reproduce the results from a few years ago due to lacking a gap-less record of every processing and analysis step including all parameters involved. There is only one way to overcome this problem: developing robust tools for data analysis that, while maintaining a maximum of flexibility in their application, allow the user to perform advanced processing steps in a scientifically sound way. At the same time, the only viable approach for reproducible and traceable analysis is to relieve the user of the responsibility for logging all processing steps and their parameters. This can only be achieved by using a system that takes care of these crucial though often neglected tasks. Here, we present a solution to this problem: a framework for the analysis of spectroscopic data (ASpecD) written in the Python programming language that can be used without any actual programming needed. This framework is made available open-source and free of charge and focusses on usability, small footprint and modularity while ensuring reproducibility and good scientific practice. Furthermore, we present a set of best practices and design rules for scientific software development and data analysis. Together, this empowers scientists to focus on their research minimising the need to implement complex software tools while ensuring full reproducibility. We anticipate this to have a major impact on reproducibility and good scientific practice, as we raise the awareness of their importance, summarise proven best practices and present a working user-friendly software solution.

Most experimental methods for studying the kinetics of surface reactions – for example, temperature programmed desorption (TPD), molecular beam relaxation spectrometry (MBRS) and velocity-resolved kinetics (VRK) – employ detection schemes that require thermal desorption. However, many adsorbates – for example reaction intermediates – never leave the surface under reaction conditions. In this paper, we present a new method to measure adsorbate concentrations on catalytic surfaces and demonstrate its utility for studying thermal desorption kinetics. After a short-pulsed molecular beam deposits CO or NH₃ on Pt (111), the surface is irradiated with an ultrashort laser pulse that induces desorption. Another tightly focused ultrashort laser pulse ionizes the gas-phase molecules by a non-resonant multiphoton process and the ions are detected. This two-laser signal is then recorded as a function of time after the dosing molecular beam pulse and decays exponentially. First-order thermal desorption rate constants are obtained over a range of temperatures and found to be in good agreement with past reports. Ion detection is done mass selectively with ion-imaging, dispersing the gas phase molecules by their velocities. Since laser-induced desorption (LID) produces hyperthermal gas phase molecules, they can be detected with little or no background. This approach is highly surface-specific and exhibits sensitivity below 10⁻⁴ ML coverage. Because the signals are linearly proportional to adsorbate concentration, the method can be employed at lower temperatures than VRK, whose signal is proportional to reaction rate.

Nuclear magnetic resonance (NMR) is widely applied from analytics to biomedicine although it is an inherently insensitive phenomenon. Overcoming sensitivity challenges is key to further broaden the applicability of NMR and, for example, improve medical diagnostics. Here, we present a rapid strategy to enhance the signals of ¹³C-labelled metabolites with para-hydrogen and, in particular, ¹³C-pyruvate, an important molecule for the energy metabolism. We succeeded to obtain an average of 27 % ¹³C polarization of 1-¹³C-pyruvate in water which allowed us to introduce two applications for studying cellular metabolism. Firstly, we demonstrate that the metabolism of 1-¹³C-pyruvate can serve as a biomarker in cellular models of Parkinson's disease and, secondly, we introduce the opportunity to combine real-time metabolic analysis with protein structure determination in the same cells. Based on the here presented results, we envision the use of our approach for future biomedical studies to detect diseases.

Invited for this month's cover is the group of Prof. Luís M. N. B. F. Santos at the University of Porto (Portugal). The cover picture shows a scheme of the μFlowCAL working principle. This flow type microcalorimeter is able to measure the heat of mixing/reaction of two fluids injected in a glass micromixer micro reactor of 200 μL. A second micromixer/reactor is used as a calorimetric reference. This calorimeter allows for an accurate measurement of heats of mixing or dilution using very small samples. Read the full text of their Research Article at 10.1002/cmtd.202100099.

The Front Cover shows a scheme of the working principle of μFlowCal. This flow microcalorimeter is designed towork in isothermal conditions, in differential mode and in the absenceof gas phase, requiring small amounts of sample (200 μL). Both themicrocalorimeter and its operational methodology were optimized tomeasure the heat of mixing of fluids with moderate viscosity andvolatility. More information can be found in the Research Article by Inês C. M. Vaz et al.

Automated chemical synthesizers have become more common in recent years but struggle to apply rigid procedures to broad substrate scopes. We have developed an adaptive auto-synthesizer that uses online HPLC and FTIR measurements to adapt to the changing reactivities of different substrates, allowing precise control of reaction conditions. To do so, we designed a flexibly-timed procedure consisting of specific actions performed by our platform when specific reaction-monitoring checkpoints are met. Online HPLC allowed our system to autonomously separate, label and quantify most reaction components, with orthogonal FTIR enabling non-UV active species to be additionally tracked. We tested our platform with CDI-mediated multistep amidation reactions using a variety of different acid and amine substrates. To demonstrate the high reproducibility and control afforded by our system, we determined the relative rates of both acid activation and subsequent amidation, providing insight into substrate reactivities and the reaction mechanism.