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Cleaning up our water – is m-BiVO4 the answer?

16 Sep 2011

Scanning electron microscope images of the octahedral m-BiVO4 crystals prepared with SDBS (left), and schematic illustration of the crystal orientation of m-BiVO4 octahedron with specific facets (right) Water contamination by synthetic organic chemicals is a burgeoning global problem due to the difficult degradation of these materials. Bismuth vanadate (BiVO₄) has been identified as promising photocatalyst for environmental applications because of its stability in water without altering the pH value. A very low band gap of 2.4 keV also means there is potential to activate BiVO₄ by visible light. The formation of good crystals with few structural defects and preferred facets is essential to the optimisation of these processes.

Mandi Han and colleagues at the Nanyang Technological University in Singapore have synthesised octahedral single crystals of monoclinic bismuth vanadate (m-BiVO₄) by hydrothermal methods. Reaction times, acid concentration and the addition of the surfactant sodium dodecyl benzene sulfonate all influence the growth of good crystals. Electron microscope measurements reveal the uniform size of these octahedral single crystals and preferred {120} and {021} crystalline facets. The m-BiVO₄ crystals exhibit excellent photocatalytic performance determined by the degradation of rhodamine B under visible light irradiation. Future research will investigate the effect of different facets on photocatalysis performance.

Read the full paper to find out more…

Synthesis of mono-dispersed m-BiVO4 octahedral nano-crystals with enhanced visible light photocatalytic properties
Mandi Han, Xiaofeng Chen, Ting Sun, Ooi Kiang Tan and Man Siu Tse
CrystEngComm, 2011, Advance Article
DOI: 10.1039/C1CE05539A

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Unprecedently Short Halogen Bonds

19 Aug 2011

Tetrahedral arrangement of N-iodosuccinimide with tetrafunctional hexamethylenetetramine forming infinite channels along the crystallographic c axis

Supramolecular synthons based on halogen bonding have been identified as excellent tools for the design and synthesis of supramolecular architectures. This growing field in crystal engineering has led to many discoveries of new and exciting intermolecular bonding motifs.

In this advance article, Kari Raatikainen and Kari Rissanen from the University of Jyväskylä report extremely short X···N synthons (where X= Br, I) from the crystal structures of N-haloimides with a series of amines and identify a unique example of a halogen bond based tubular material.

X-ray structure analyses reveal that X···N (X = Br, I) distances range from 2.347 Å to 2.596 Å. These unusually short halogen bond distances suggest an extremely polarized halogen atom, which allows exceptionally large overlap of Van der Waals volumes with the donor atom. The tetrahedral arrangement of N-iodosuccinimide with tetrafunctional hexamethylenetetramine exhibits these very strong halogen bonds, as well as multiple weak C-H···O hydrogen bonds, to form infinite channels with 7.31 Å × 6.74 Å diameter along the crystallographic c axis. The properties of this complex as a porous material are currently under investigation.

Interaction between amines and N-haloimides: a new motif for unprecedentedly short Br···N and I···N halogen bonds
Kari Raatikainen and Kari Rissanen
CrystEngComm, 2011, Advance Article DOI:10.1039/C1CE05447C

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Cleaning up our water – is m-BiVO4 the answer?

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