CrystEngComm Blog

Flufenamic acid (FFA) is a potent non-steroidal anti-inflammatory drug used to treat lower back pain, either orally or topically.  However, it has low solubility and a slow dissolution rate which are problematic.  One way these properties can be improved is by forming a solid solution with polyvinylpyrrolidine or a co-crystal with nicotinamide (NA).  Co-crystals form between the active molecule and a co-former and possess different physicochemical properties from either of the components.

A recent CrystEngComm article reports the formation and X-ray structures of three new co-crystals of FFA, with the co-formers theophylline (TP), 4-pyridone and 4,4’-bipyridine.  Each of the three structures shows the formation of heterosynthons (i.e. interactions between complementary functional groups) e.g. for FFA-TP, interactions between FFA O-H and TP N atoms.   TP is a central nervous system stimulant, found in cocoa beans, and used to treat respiratory diseases such as asthma.  The FFA-TP system is an example of a drug-drug co-crystal, where both components have biological activity and therefore is of particular interest.

The authors found improved solubility and dissolution rate for this system, compared to either pure FFA or the FFA-NA co-crystal.  They also compared the properties to a TP co-crystal with oxalic acid, with the FFA-TP co-crystal proving less hygroscopic.

These results suggest that formation of this co-crystal offers improved properties for both FFA and TP and in addition, offers an opportunity to explore the development of combination drugs by forming drug-drug co-crystals.

For more information see the paper:

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

Harnessing light from the sun to drive reactions requires the development of photocatalysts which can both absorb light of the required frequency but also absorb enough of this light to meet the energy demands for the reactions.  To solve this latter problem, silver halide catalysts with silver particles adsorbed on the surface (i.e. AgX@Ag) are a possibility, as these utilise the surface plasmon resonance (SPR) effect to enhance the visible light absorbed.  SPR occurs when electrons from the surface Ag atoms oscillate at the same frequency as the visible light. The degree of oscillation  increases and subsequently increases the energy available to facilitate a chemical reaction.  Unfortunately, forming the AgX@Ag particles can require high temperatures and strong light.

A recent CrystEngComm paper reports a facile synthesis of AgCl@Ag under mild conditions, using the biomaterial agar gel as a matrix.  Diffusion of the reactants is mediated by the matrix and on illumination with visible light, Ag atoms are generated on the surface of the AgCl.  The AgCl@Ag particles produced are in the form of concave cubes.  The authors suggest their mild eco-friendly synthesis method could be used to prepare other functional materials at low cost.

For more details, see the paper:

Biomaterial-assisted synthesis of AgCl@Ag concave cubes with efficient visible-light-driven photocatalytic activity
Pei Hu, Xianluo Hu, Chaoji Chen, Dongfang Hou and Yunhui Huang
CrystEngComm, 2014, DOI: 10.1039/C3CE41925H

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

Epichrorohydrin (ECH) is an important reagent in the industrial production of glycerol, epoxy resins and polymers used in the paper and food industries.  However, it is toxic to humans by inhalation, by absorption through the skin and by ingestion – and it is a cancer suspect agent.  Accurate and reliable detection of ECH gas is therefore required so that risks can be monitored and minimised.  Semiconductor materials like tin dioxide (SnO₂) are one possibility – they are highly sensitive to gas absorption but their lack of sensitivity to individual gases is problematic.  One method of improving sensitivity is to dope the material with noble metals.

A new paper describes the preparation of porous SnO₂ materials decorated with 5-15% Ag.  These have a diameter of 4-5 μm and consist of nanosheets.  The ECH sensing properties of the new materials were studied and the 10% doped sample was found to give the best performance.  It showed a fast response and recovery time, high response, good selectivity and a detection limit of 0.5 ppm, rendering it a promising material for use in ECH detection.

For more information see the paper:

Selective epichlorohydrin-sensing performance  of Ag nanoparticles decorated porous SnO₂ architectures
Zhenglin Zhang, Haiyan Song, Shishu Zhang, Junyan Zhang, Wenya Bao, Quanqin Zhao and Xiang Wu
CrystEngComm, 2014, Advance Article
DOI: 10.1039/C3CE41478G, Paper

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.

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.