CrystEngComm Blog

Posted on behalf of Josh Campbell, web writer for CrystEngComm

Organic superconductivity has been observed in charge transfer complexes since the 1980s. The organic cation is most commonly a tetrathiafulvalene derivative or a polycyclic aromatic hydrocarbon. Typically the charge is transported through 1D π-stacks, which can be thought of as molecular wires. However interactions between neighbouring wires have a large impact on the properties of the bulk. The preparation of insulated molecular wires can allow for better understanding of the 1D charge transport and better electronic properties. In π-stacked materials bulky counter ions are used to separate the stacks which allows for better solubility and survival of strongly cationic species.

A new paper looks at how TMFB ((trifluoromethyl)phenylborate) counter ions affect the crystalline packing seen across a series of organic donors. Two distinct packing arrangements were seen, with some donors adopting π-stacked chains which were well separated by the counter ion. However others showed an isolated cation radical bonding motif. To investigate this the authors looked at the size of the donors in question and showed that the switch between packing is possibly to do with the product of the width and length of the molecule. The authors also investigated the electronic properties of the stacks, some of which showed excellent electronic properties.

Find out more from the paper:

π-Bonded molecular wires: self-assembly of mixed-valence cation-radical stacks within the nanochannels formed by inert tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anions
Sergiy V. Rosokha, Charlotte L. Stern and Jeremy T. Ritzert
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41719K

Josh Campbell is a PhD student currently at the University of Southampton studying crystal structure prediction of organic semiconductors. He received his BSc from the University of Bradford.

Doping of semiconductor crystals with transition metal ions can create materials with improved optical, magnetic and thermal properties.  These could potentially replace conventional semiconductors in optical devices.  However, as the size and shape of the crystals as well as the dopant need to be controlled to optimise the desired properties, their preparation can prove difficult.  The addition of Cu ions to ZnSe nanocrystals is of interest due to their emission properties, but the large difference in structure between Cu_xSe and ZnSe makes retaining the shape after doping, problematic.

A new paper shows how doping of ZnSe crystals with Cu ions can be achieved under mild reaction conditions, obtaining ultrathin nanorods.  This is achieved by preparing  ZnSe nanorods then adsorbing Cu ions onto the surface and finally growing a thin shell of ZnSe on top, as shown in the figure below. The process, termed growth-doping, maintains the shape of the rods during the doping process.  The optical properties of the 1% Cu doped rods give a quantum yield of 7% and the emission is retained for weeks in air, suggesting it may have potential for use in optical devices.

For more information see the paper:

Facile synthesis and optical properties of ultrathin Cu-doped ZnSe nanorods
Shufang Kou, Tingting Yao, Xiaofeng Xu, Rui Zhu, Qing Zhao and Jian Yang
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41493K

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. Currently she is writing a book on chemicals from plants.

Posted on behalf of Josh Campbell, web writer for CrystEngComm

Photocatalysis has applications ranging from sterilising surgical equipment to the conversion of water to hydrogen. In particular mesoporous catalysts show good catalytic activity due to their high surface area, ordered pore structures and high pore volumes. There are two usual methods of fabricating these: either by supporting a catalyst (such as Au or TiO) on a mesoporous silicon framework; or using a catalyst with an inherent mesoporous structure. However there are drawbacks, as excess catalyst can block pores and synthesising a mesoporous structure can be difficult.

A new paper uses a novel way to develop photocatalysts. Bi₂O₃/Bi₂SiO₅ heterostructures were placed in SiO2 mesoporous microspheres. The combination of Bismuth catalysts enhances the photocatalytic activity. The authors propose this occurs due to the small size of the photocatalyst (leading to a reduction in the electron-hole recombination rate), the high surface area of the mesoporous structure and efficient electron-hole splitting due to formation of heterostructures.

Find out more from the paper:

Solar light photocatalysis using Bi₂O₃/Bi₂SiO₅ nanoheterostructures formed in mesoporous SiO₂ microspheres
Ling Zhang, Wenzhong Wang, Songmei Sun, Dong Jiang and Erping Gao
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41433G

Josh Campbell Josh Campbell is a PhD student currently at the University of Southampton studying crystal structure prediction of organic semiconductors. He received his BSc from the University of Bradford.

Posted on behalf of Gwenda Kyd, web-writer for CrystEngComm

Cuprous oxide (Cu₂O) has many potentially useful applications resulting from its optical and magnetic properties. It has a small band-gap, which gives it attractive photocatalytic behaviour, further enhanced by its low cost and environmental acceptability. However, the control of size and morphology of Cu₂O particles can be problematic.

A new paper demonstrates use of a simple wet-chemical method to form a new class of Cu₂O particles existing as short hexapods, octahedra or {110} truncated octahedra. These are formed in a size- and morphology-controllable manner depending on the reaction conditions. The degradation of methyl oxide (MO) dye gives a measure of photocatalytic activity of the different morphology crystals (see diagram below). The results indicate that activity varies with morphology, with the best results obtained for smallest-sized octahedra and potential use in the treatment of organic pollutants is indicated.

For more details see the paper at:

The morphology dependence of cuprous oxide and its photocatalytic properties
Ru Li, Xuefeng Yan, Liangmin Yu, Zhiming Zhang, Qunwei Tang and Yongping Pan
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41470A

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. Currently she works as a scientific database editor.

Posted on behalf of Gwenda Kyd, web writer for CrystEngComm

The efficacy of some anti-cancer treatments could potentially be increased and side-effects reduced by improved transport and specific delivery of drugs to the tumour site. The porosity of metal-organic frameworks (MOFs) makes them attractive potential carriers. In addition, MOFs can have multiple pore types with different characateristics and also exposed metal sites where molecules can coordinate, so the inclusion of multiple bioactive molecules in the same carrier may be possible.

In a new paper, the MOF CPO-27-Ni is shown to act as a carrier for both the non-conventional anti-cancer drug RAPTA-C and nitrous oxide (NO). A high concentration of NO in tumour cells is beieved to increase the sensitivity to some cytotoxic drugs. In CPO-27-Ni, the uptake of RAPTA-C and NO are unaffected by each other and both compounds are efficiently released in simulated body fluid. The NO is chemisorbed by interaction with the Ni sites in the MOF while the RAPTA-C is physisorbed into the pores of the framework structure.

For more information see the paper at:

Metal–organic frameworks as potential multi-carriers of drugs
Sara Rojas, Paul S. Wheatley, Elsa Quartapelle-Procopio, Barbara Gil, Bartosz Marszalek, Russell E. Morris and Elisa Barea
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41289J, Communication

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. Currently she works as a scientific database editor.