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

Beckmann rearrangement was carried out in the solid state in a ball mill using metal oxides as solid acids. After a comprehensive investigation of different reaction parameters, acids as well as further additives, a combination of aluminosilicate materials, phosphorus pentoxide, and para-toluenesulfonic acid was identified as the optimal system. This allowed the model compounds ϵ-caprolactam and acetanilide to be obtained in yields of 46 % and 94 %, respectively, while the robustness of the method was demonstrated by applying it to additional substrates. Finally, we scaled up our optimized reaction into a continuous process using a twin screw extruder. With this, yields beyond 90 % could be achieved in a residence time as low as seven minutes.

The need for continuous observation of electrocatalytic processes under operating conditions has promoted the popularity of in situ techniques coupled with electrochemical tests. In situ Raman spectrometer coupled with electrochemistry (or Raman spectroelectrochemistry) is a powerful tool to provide real-time structural information related to the dynamic electrolyte/electrode interface. To make it more accessible among the electrocatalysis community, we provide an essential experimental guideline of in situ Raman spectroelectrochemistry to beginners. After the necessary background of the technical principle and primary applications, we focus on the experimental considerations, from electrode preparation, cell design, and laser parameters to the electrochemical sequence and data process. The recent efforts to make this technique more affordable are also highlighted. We hope this review can help beginners to understand and use Raman spectroelectrochemistry.

The novel spinel Cu_0.2Co_0.2Mn_0.2Ni_0.2Zn_0.2Fe₂O₄ comprising six transition metal cations was successfully prepared by a solution-combustion method followed by distinct thermal treatments. The entropic stabilization of this hexa-metallic material is demonstrated using in situ high temperature powder X-ray diffraction (PXRD) and directed removal of some of the constituting elements. Thorough evaluation of the PXRD data yields sizes of coherently scattering domains in the nanometre-range. Transmission electron microscopy based methods support this finding and indicate a homogeneous distribution of the elements in the samples. The combination of ⁵⁷Fe Mössbauer spectroscopy with X-ray absorption near edge spectroscopy allowed determination of the cation occupancy on the tetrahedral and octahedral sites in the cubic spinel structure. Magnetic studies show long-range magnetic exchange interactions which are of ferri- or ferromagnetic nature with an exceptionally high saturation magnetization in the range of 92–108 emu g⁻¹ at low temperature, but also an anomaly in the hysteresis of a sample calcined at 500 °C.

The Front Cover shows a battery cell designed for in operando neutron powder diffraction. The picture seeks to illustrate the experiment process where lithium ions are moving into the crystal structure of the battery cathode during discharge. This leads to changes in the crystal structure that are very important to understand for optimizing the battery materials. These structural changes are probed in operando by neutron powder diffraction, and neutrons are especially suited for probing the location of Li-ion compared with similar techniques such as X-ray diffraction. More information can be found in the Research Article by Daniel R. Sørensen et al..

Invited for this month's cover is the group of Daniel R. Sørensen at the University of Aarhus (Denmark) and at the University of Lund (Sweden). The cover picture shows a battery cell designed for in operando neutron powder diffraction. The picture seeks to illustrate the experiment process where lithium ions are moving into the crystal structure of the battery cathode during discharge. This leads to changes in the crystal structure that are very important to understand for optimizing the battery materials. These structural changes are probed in operando by neutron powder diffraction, and neutrons are especially suited for probing the location of Li-ion compared with similar techniques such as X-ray diffraction. The beauty of using neutrons is also that their penetrating power allows for investigating the battery without the need for windows of any kind. Read the full text of their Research Article at 10.1002/cmtd.202200046.

Digitalisation and industry 4.0 are set to profoundly change the way chemical and materials discovery and development work. The integration of multiple enabling technologies such as flow synthesis, automation, analytics, and real-time reaction control lead to highly efficient, productive, data-driven discovery and synthetic protocols. For instance, the development of flow chemistry enables the fine control and automation of process parameters such as flow rates, temperature, and pressure, which inherently enhances process efficiency. Flow chemistry presents a more sustainable means of manufacturing in terms of waste minimisation, as it enables the integration of synthetic processes with downstream processing. Furthermore, it allows the integration of analytical techniques to provide in situ process monitoring of large amounts of process and product data. The application of Artificial Intelligence (AI) and/or Machine Learning (ML) techniques allows rapid decision making that can optimise existing processes, and it has also been applied in the discovery of novel materials, synthetic pathways and chemicals. All this is contributing to an effective digitalisation of chemical and material synthetic processes from the laboratory to large-scale industrial deployment.

This paper presents recent developments in the effective digitalisation of chemical synthetic processes which integrates continuous flow synthesis, analytics and artificial intelligence technologies. Specifically, this paper illustrates the emerging trend of process digitalisation through the advanced syntheses of materials with catalytic, optical and optoelectronic applications.

The accurate measurement of redox potentials of small molecules is a relatively straightforward task using electrochemical methods such as cyclic voltammetry. However, proteins, in most cases, are not amenable to the same approach due to slow heterogeneous electron transfer and the possibility of denaturing at the electrode surface. This necessitates the use of small molecular weight redox mediators to facilitate electron transfer. This leads to spectroelectrochemical techniques where the applied electrochemical potential is coupled to a spectroscopic signal of the protein. Traditionally this is done at different applied (fixed) potentials akin to an electrochemical titration, but the time required for electrochemical equilibrium to be established, and its consistent application, are major sources of experimental error. Here we have utilised a continuously scanning potential synchronised with time-resolved UV-vis spectroscopy to provide an automated approach that can be used to measure protein redox potentials accurately in an expedient manner. The test cases are the heme proteins cytochrome c and myoglobin. The scope and limitations of the method are discussed.

In operando powder diffraction remains one of the most powerful tools for non-destructive investigation of battery electrode materials. While in operando X-ray, especially synchrotron radiation, powder diffraction is by now a routine experimental technique, in operando neutron powder diffraction is still less established. We present a new electrochemical cell for in operando neutron powder diffraction, which is, first and foremost, easy to use, but can also cycle electrode materials under electrochemical conditions close to those achieved using standard laboratory cells. The cell has been designed in multiple sizes, and high-quality electrochemical and neutron powder diffraction data is presented for sample sizes as low as 48 mg total active material. The cell handles lithium-ion and sodium-ion materials equally well, with no difference in how the cell is prepared and assembled. The cell is intended to be used as sample environment at powder diffractometers at the neutron facilities MLZ, ORNL and ACNS.

The Front Cover shows a sketch of the formation process of metal oxide nanoparticles, where nanocrystalline oxides form from fragments of polyoxometalates. In situ X-ray total scattering studies with Pair Distribution Function analysis can give new insights into the formation process, as it provides structural information on all stages of the reaction – from precursor ions in solution, over amorphous or nanostructured intermediates to the final crystalline material. Here, we show how the analysis of such data can be automated using structure mining and simple computational tools. More information can be found in the Research Article by EmilT. S. Kjær0000et al..

Invited for this month's cover are the groups of Kirsten M. Ø. Jensen at the University of Copenhagen (Denmark) and Simon J. L. Billinge at Columbia University (US). The cover picture shows a sketch of the formation process of metal oxide nanoparticles, where nanocrystalline oxides form from fragments of e.g., polyoxometalates. In situ X-ray total scattering studies with Pair Distribution Function analysis can give new insights into the formation process, as it provides structural information on all stages of the reaction – from precursor ions in solution, over amorphous or nanostructured intermediates to the final crystalline material. Here, it is show how the analysis of such data can be automated using structure mining and simple computational tools. Read the full text of their Research Article at 10.1002/cmtd.202200034.