CrystEngComm Blog

Carbon dioxide (CO₂) can be reduced to give methane using light, in the presence of a catalyst. This process is attractive as it provides a potential feedstock for other processes as well as removing the greenhouse gas CO₂ from the atmosphere. The catalyst is key to the photoreduction, and ZnGaNO is a promising candidate as it is stable, environmentally friendly and absorbs light in the visible region, which is suitable for the reduction of CO₂.

A new paper reports the synthesis of ZnGaNO nanorods by molten salt ion exchange, which represents a milder method than that used conventionally. This involves use of ZnCl₂ as both a source of Zn and a molten salt. It is nitrided at 750 °C for five hours, along with KGaO₂, as represented below.

The as-prepared nanorods show enhanced performance as catalysts for CO₂ reduction. The rate of methane evolution is four times higher than that using ZnGaNO from solid state synthesis. As the photoreaction takes place on the surface of the catalyst, the larger surface area of the nanorods is thought to be significant. In addition, the nanorods possess a higher concentration of Zn ions owing to a lower synthesis temperature, which facilitates better energy absorption. There are also less surface defects in the nanorods, so recombination of carriers is disfavoured.

For more details, see the full paper at:

Molten salt ion exchange route to ZnGaNO single crystal nanorods for improved CO₂ photoreduction to CH₄
P. Zhou, S. C. Yan and Z. G. Zou
CrystEngComm, 2015, DOI: 10.1039/C4CE02198C

Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.

Control of the crystal form of pharmaceutically important molecules such as paracetamol is crucial to the successful development of drug molecules.  Conventional crystallisation from organic solvents can lead to unwanted forms with poor physicochemical properties.  Crystallisation from ionic liquids (ILs) offers a potential alternative.  ILs are composed entirely of ions and have low melting points as their cationic components are large and unsymmetrical, resulting in low lattice energies.

A new paper shows how the crystallisation of paracetamol, commonly used to reduce pain and fever, from ILs can be controlled.   Use of two ILs, 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]) was studied, under cooling crystallisation conditions.

The thermodynamically stable monoclinic I form of paracetamol was obtained from both ILs but the crystal size and shape varied with the IL used, the solution concentration and the mechanism of crystal growth.  One of the samples produced is shown below.

Crystal habits not commonly produced by conventional crystallisation could be produced – elongated prisms from [bmim][PF₆] and trigonal bipyramids from [hmim][PF₆]. These results suggest that ILs have potential value for the crystal engineering of pharmaceutically important molecules.

For full details, see the paper at:

Crystallisation control of paracetamol from ionic liquids

K. B. Smith, R. H. Bridson and G. A. Leeke

CrystEngComm, 2014, Advance Article
DOI: 10.1039/C4CE01796J

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Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.

As the number of cars continues to increase, the problem of hazardous exhaust fumes such as nitrogen dioxide (NO₂) becomes more pressing.  New gas sensors are required to determine the quantities of these gases quickly and accurately.  These are often made of metal oxide semiconductors, including tungsten trioxide (WO₃), which are easily fabricated, low cost materials.  Nano-sized structures typically possess better gas adsorption properties than the bulk material due to favourable surface effects but particles of different shapes (morphologies) could also have different gas-sensing properties.

A new paper presents a method of producing three different morphologies of WO₃ nanostructures and studies their gas-sensing abilities.  In the simple hydrothermal synthesis, control of morphology is achieved using different amounts of citric acid, thereby changing the number of available carboxyl-groups.  This produces nanoparticles (0D), nanoplates (2D) and hierarchical microspheres (3D).  Among these 3 morphologies, the hierarchical structures are found to show the best gas-sensing properties towards NO₂ (see diagram below), with a high sensitivity, a fast response time and operating at a relatively low temperature (200^oC).

Authors conclude that this is due to an increased number of defects present in the structure which increases the number of gas adsorption sites on the surface, while their internal structure accelerates transport of the gas molecules to the sensing sites.

For more information, see the full article at:

Carboxyl-directed hydrothermal synthesis of WO₃ nanostructures and their morphology-dependent gas-sensing properties

Shouli Bai, Kewei Zhang, Xin Shu, Song Chen, Ruixian Luo, Dianqing Li and Aifan Chen

CrystEngComm, 2014, Advance Article
DOI: 10.1039/C4CE01167H

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Gwenda Kyd has a PhD in metallocarborane chemistry from the University of Edinburgh. Other research work includes the spectroscopic study of the structure of glasses and organometallic electron-transfer reactions and the preparation of new inorganic phosphors. She has recently published a book on chemicals from plants.