CrystEngComm Blog

Posted on behalf of Josh Campbell, web writer for CrystEngComm

Rare earth metals and their compounds are some of the most important elements in modern economies and science. They can be found in superconductors, catalytic converters and lasers. Most rare earth ions also show the phenomenon of upconversion (UC). UC is the emission of light at shorter wavelengths than initially absorbed at for example the conversion of infrared to visible light. UC effects show great promise in the bioimaging field, providing narrow emission bandwidths and high-signal to noise ratio due to being able to use near infra-red sources of excitation. Rare earth halides are known to increase UC luminescence but chlorides and bromides are usually sensitive to moisture and not suitable for labelling biomolecules.

A new highlight shows the most popular way of synthesizing rare earth fluorides and their applications as luminescent labels. Thermal decomposition is the most common synthesis method and gives nanocrystals with well-defined shapes and good size selectivity. However there are drawbacks (such as the strict experimental conditions) which have led to the development of coprecipitation and microwave assisted methods among others. These nanoparticles with UC properties have also recently shown promise being used as multimodal imagers. Multimodal imaging uses more than one technique and work is being done to integrate magnetic components into UC nanocrystals to combine MRI and luminescent imaging.

Find out more from the article:

Rare earth fluorides upconversion nanophosphors: from synthesis to applications in bioimaging
Song Wang, Jing Feng, Shuyan Song and Hongjie Zhang
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE40679B, Highlight

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

Metal-organic frameworks (MOFs) are porous networks with a wide range of potential applications including gas storage and sensing. For their potential to be fully realised in integrated systems, efficient methods of producing thin films and patterns are crucial. Although methods exist for MOFs, these are are less developed than for other materials such as ZnO.

A new paper shows how thin films or patterns of the MOF ZIF-8 can be produced by melting the required ligand, 2-methylimidazole , in contact with a ZnO film or pattern. If the process is carried out under vacuum with an excess of ligand, it is totally solvent- and waste-free. Using this method with ZnO supported films and patterns is demonstrated to replicate the morphologies in the resulting ZIF-8, as shown in the diagram below. ZIF-8 is highly stable and has many possible uses including molecular separation and as an insulator in microelectronics. The reported strategy could allow new applications for ZIF-8 films to be developed.

For more information see the paper at:

Solvent-free synthesis of supported ZIF-8 films and patterns through transformation of deposited zinc oxide precursors
Ivo Stassen, Nicolò Campagnol, Jan Fransaer, Philippe Vereecken, Dirk De Vos and Rob Ameloot
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41025K, Communication

Gwenda KydGwenda 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.

Over time, gleaming teeth become stained by repeated exposure to vices such as coffee, red wine or cigarettes. Current whitening methods include replacing the crown of the tooth or etching off stained enamel using chemical abrasives like hydrogen peroxide. These require the removal of part of a healthy tooth, and can lead to gum irritation and sensitive teeth.

Fluorapatite, polyethylene oxide and a polymer derived from the neurotoxin acrylamide have been combined by Chinese scientists to make a film that can restore teeth to their natural colour.

Read the full story at Chemistry World

PEO-assisted precipitation of human enamel-like fluorapatite films for tooth whitening
Shize Liu, Yujing Yin and Haifeng Chen

CrystEngComm, 2013,15, 5853-5859
DOI: 10.1039/C3CE40388B, Paper

Posted on behalf of Gwenda Kyd, web writer for CrystEngComm

Biofuels, such as plant oils, are a potential alternative energy source. However, the presence of impurities like gums and phospholipids can hamper their use in diesel engines. Phospholipids (which are made up of a fatty acid, a simple organic group and a phosphate group) can be removed in the conventional refining process, but this causes loss of oil and nutrients and uses both water and chemicals.

A new paper shows how phospholipids can be efficiently removed using Y₂O₃ cubes and flowers, made hydrothermally, as shown in the figure below. Y₂O₃ is a Lewis acid and the positively charged metal atom attracts the negatively charged phospholipid, absorbing it onto the metal-oxide surface. Y₂O₃ flowers have a larger specific surface area than cubes, so absorb phopholipds more efficiently (approximately 90% rather than 80% of 870 ppm phospholipid in soyabean oil). This demonstrates that both flowers and cubes could have potential use in the separation of phospholipids from plant oils.

For more information see the paper at:

Hydrothermal synthesis of Lewis acid Y₂O₃ cubes and flowers for the removal of phospholipids from soybean oil
Yi-Feng Lin, Jhen-Huei Chen, Shih-Hong Hsu and Tsair-Wang Chung
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE40791H, 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 works as a scientific database editor.

Posted on behalf of Josh Campbell, web writer for CrystEngComm 

Metal nanoparticles (NPs) are structures within the µm-nm range that exhibit amazing properties and morphologies. Photochemical and superparamagnetic effects have been reported while everything from nanostars to nanoreefs have been created. NPs are often thought to be a product of modern science but their use dates back hundreds of years, used in pottery finishes and for staining glass. Michael Faraday first described the effect of gold colloids on glass in 1857. NPs are usually prepared by physical or chemical methods, and each has its own advantages and problems. Physical methods such as vapour deposition and laser ablation do not offer complete control over the size of the NPs unless at extreme conditions. These typically require a solid substrate, limiting their use in producing liquid suspensions. Chemical methods involve the reduction of the metal ions dissolved in appropriate solvents and for noble metals have produced NPs down to micron level. However, this method does not work well for metals prone to oxidation.

This new paper describes the chemical synthesis of zinc nanoparticles which show exciting photoluminescence properties and a resistance to oxidation. ZnCl was dissolved in a phenylether and complexed with oleylamine before being reduced to Zn²⁺, after which it nucleates into the final structure. Hexagonal Zn particles form which have a diameter of 250-350nm and showed no oxide phases. The Zn particles also were found to emit light in the UV to blue range. The authors suggest that this is due to the 3d-Fermi gap being lowered compared to bulk zinc, and the sp band itself being discretized.

Find out more:

Chemical synthesis of blue-emitting metallic zinc nano-hexagons
Nguyen T. Mai, Trinh T. Thuy, Derrick M. Mott and Shinya Maenosono
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE40801A, Paper

 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

Pigments are solid colourants used in the production of materials such as paints, inks and plastics. For a given pigment, the colour is affected by particle size and morphology, among other things. Formation of a multi-componet system (co-crystal) may also affect the colour and, additionally, may alter properties like heat stability. However, pigments tend to be insoluble in common solvents, rendering production of co-crystals by conventional, solution-based, methods difficult.

A new paper shows how mechanochemical co-crystallisation (ie grinding the components in a small quantity of solvent) can produce co-crystals of the pigment fluorescein (see diagram below) quickly and in quantitative yields. Co-crystals with three different co-formers were produced each with a different colour. Attempts to produce co-crystals using solvent-based methods were also successful, but produced different co-crystals and less efficiently. Authors discuss the broad implications of the results for the pigment and dye industries, suggesting mechanochemical co-crystallisation as an efficient route to colour- and property-tunable pigments.

More information can be found in the full paper at:

Advantages of mechanochemical cocrystallisation in the solid-state chemistry of pigments: colour-tuned fluorescein cocrystals
Dejan-Krešimir Bučar, Stefan Filip, Mihails Arhangelskis, Gareth O. Lloyd and William Jones
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41013G, 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.

Posted on behalf of Gwenda Kyd, web writer for CrystEngComm

Many important drug molecules are hydrophobic so methods to successfully introduce these into the body and make them bioavailable must be developed. Peptide-based molecules are an attractive delivery vehicle due to their biocompatibility, recognition properties, biodegradability and hydrophobic-hydrophilic balance.

A new paper shows how three gamma-peptides, with different degrees of flexibility, can self-assemble to form porous microspheres (see diagram below). The anticonvulsant drug carbamazepine has been encapsulated in these microspheres, which range in diameter from 300nm-1µm. The microspheres have limited water solubility, so there is a sustained release of the drug by dissolution of the microsphere. The authors suggest tailoring of the capsule properties could lead to controlled drug delivery and release.

Find out more in the paper:

Fabrication of microspheres from self-assembled γ-peptides
Suman Kumar Maity, Santu Bera, Arpita Paikar, Apurba Pramanik and Debasish Haldar

CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE40689J, Paper