Bulk solvents, widely used in the chemical industry, pose a serious threat to human health and the environment. As a result, there is growing interest in avoiding their use by relying on "mechanochemistry" – an energy-efficient alternative that uses high-frequency milling to drive reactions. Because milling involves the intense impact of steel balls in rapidly moving jars, however, the underlying chemistry is difficult to observe.
Now, for the first time, scientists have studied a milling reaction in real time, using highly penetrating X-rays to observe the surprisingly rapid transformations as the mill mixed, ground, and transformed simple ingredients into a complex product. This research, reported Dec. 2 in Nature Chemistry, promises to advance scientists' understanding of processes central to the pharmaceutical, metallurgical, cement and mineral industries – and could open new opportunities in "green chemistry" and environmentally friendly chemical synthesis.
The international team of researchers was led by Tomislav Frišèiæ of McGill University in collaboration with Ivan Halasz from the University of Zagreb in Croatia, and scientists from the University of Cambridge, the Max-Planck-Institute for Solid State Research in Stuttgart, Germany, and the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.
While mechanical action can break chemical bonds -- for example, in the wear and tear of textile fibers -- mechanical force can also be used to synthesize new chemical compounds and materials. In recent years, ball milling has become increasingly popular in the production of highly complex chemical structures. In such synthesis, steel balls are shaken with the reactants and catalysts in a rapidly vibrating jar. Chemical transformations take place at the sites of ball collision, where impact causes instant "hot spots" of localized heat and pressure. This is difficult to model and, without access to real time reaction monitoring, mechanochemistry remained poorly understood.
"When we set out to study these reactions, the challenge was to observe the entire reaction without disturbing it, in particular the short-lived intermediates that appear and disappear under continuous impact in less than a minute", says Frišèiæ, an assistant professor in McGill's Department of Chemistry.
The team of scientists chose to study mechanochemical production of the metal-organic framework ZIF-8 from the simplest and non-toxic components. Materials such as ZIF-8 are rapidly gaining popularity for their ability to capture large amounts of CO2; if manufactured cheaply and sustainably, they could become widely used for carbon capture and storage, catalysis and even hydrogen storage.
"The team came to the ESRF because of our high-energy X-rays capable of penetrating 3 mm thick walls of a rapidly moving reaction jar made of steel, aluminium or plastic. The X-ray beam must get inside the jar to probe the mechanochemical formation of ZIF-8, and then out again to detect the changes as they happened", says Simon Kimber, a scientist at the European Synchrotron Radiation Facility (ESRF) in Grenoble, who is a member of the team. This unprecedented methodology enabled the real-time observation of reaction kinetics, reaction intermediates and the development of their respective nanoparticles.
In principle, this technique could be used to study all types of chemical reactions in a ball mill, and optimize them for processing in a range of industries. "That would translate into good news for the environment, for industry -- and for consumers," Frišèiæ says.
The researchers in the team were supported by the Herchel Smith Fund, the British Council/DAAD, ESRF Grenoble, NanoDTC, the University of Cambridge, the Ministry of Science, Education and Sports of the Republic of Croatia, McGill University and the FRQNT Centre for Green Chemistry and Catalysis.
Chris Chipello | EurekAlert!
Oestrogen regulates pathological changes of bones via bone lining cells
28.07.2017 | Veterinärmedizinische Universität Wien
Programming cells with computer-like logic
27.07.2017 | Wyss Institute for Biologically Inspired Engineering at Harvard
Spectrally narrow x-ray pulses may be “sharpened” by purely mechanical means. This sounds surprisingly, but a team of theoretical and experimental physicists developed and realized such a method. It is based on fast motions, precisely synchronized with the pulses, of a target interacting with the x-ray light. Thereby, photons are redistributed within the x-ray pulse to the desired spectral region.
A team of theoretical physicists from the MPI for Nuclear Physics (MPIK) in Heidelberg has developed a novel method to intensify the spectrally broad x-ray...
Physicists working with researcher Oriol Romero-Isart devised a new simple scheme to theoretically generate arbitrarily short and focused electromagnetic fields. This new tool could be used for precise sensing and in microscopy.
Microwaves, heat radiation, light and X-radiation are examples for electromagnetic waves. Many applications require to focus the electromagnetic fields to...
Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers
Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...
Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.
At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...
3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects
A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...
26.07.2017 | Event News
21.07.2017 | Event News
19.07.2017 | Event News
28.07.2017 | Health and Medicine
28.07.2017 | Power and Electrical Engineering
28.07.2017 | Life Sciences