CrystEngComm Blog

Iron vanadate (FeV_xO_y) nanostructures have shown very good performance in sensors, lithium batteries and as catalysts.  Their properties are strongly related to the shape and surface area of the particles and this makes the controllable preparation of one dimensional (1D) nanostructures (i.e. nanowires or nanorods), with large surfaces areas, a target for scientists.

A new paper reports a simple hydrothermal technique which achieves this.   The length of the particles can be adjusted simply by varying the pH of the reaction mixture between pH 4 and pH 6, with longer wires favoured at higher pH, as shown in the diagram below.  Using this methodology, lengths from several micrometers to several millimetres can be obtained and the ratios of diameters to lengths can also be varied from 10 to over 1000. In addition, the pore sizes in the nanostructures can also be controlled using the same method of pH variation.

There are four steps in the  formation of the nanostructures – dissolution, anisotropic growth (i.e. growth in one direction), Ostwald ripening (a process where smaller particles dissolve and deposit on larger particles to achieve more thermodynamically stable particles) and, finally, pore formation by loss of water molecules.

A sample of one of the prepared nanostructures (FeVO₄ nanorods) was tested for use in selective catalytic reduction (SCR) of NO with NH₃ as the reduction of NOx emissions from diesel engines is important to reduce air pollution.  The nanorods proved stable and selective under typical reaction conditions and, in addition, were resistant against two major catalyst poisons present in exhaust fumes, H₂O and SO_2.

For more information, read the full paper using the link below:

Hydrothermal growth and characterization of length tunable porous iron vanadate one-dimensional nanostructures
Lei Huang, Liyi Shi, Xin Zhao, Jing Xu, Hongrui Li, Jianping Zhang and Dengsong Zhang
CrystEngComm, 2014, DOI: 10.1039/C3CE42608D

_______________________________________________________________________________________________________

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

Furosemide is a loop diuretic (a ‘water pill’) used to treat congestive heart failure, oedema and sometimes hypertension.  It can also be used to reduce bleeding in horses during horseracing and is banned from use for this purpose in the UK. The bioavailability of the drug when taken orally is limited by the relatively low solubility. 

Formation of co-crystals with the co-formers caffeine or cytosine improves solubility (by 6 or 11 times) but the co-crystals suffer from low stability so are not suitable for pharmaceutical use.

A new paper takes a different approach, using salt formation as an alternative to co-crystal formation. Sodium and potassium salts of furosemide were prepared and their solubilities and stabilities assessed.  The solubility of the sodium salt (furo-Na-trihydrate) was over 4000 times higher than that of the free drug, while the potassium salt (furo-K-monohydrate) was over 10000 times more soluble.

Both salts show improved stability compared to the co-crystals – at 40 °C and 75% humidity furo-Na-trihydrate is stable for 2 weeks and furo-K-monohydrate is stable for 1 week.

The authors conclude that the low cost of preparation and the enhanced solubility and stability of the salts merits their consideration for use in oral drug formulations.

For more information see the paper:

High solubility crystalline hydrates of Na and K furosemide salts
U. B. Rao Khandavilli, Swarupa Gangavaram, N. Rajesh Goud, Suryanarayan Cherukuvada, S. Raghavender, Ashwini Nangia, Sulur G. Manjunatha, Sudhir Nambiar and Sharmistha Pal
CrystEngComm, 2014, DOI: 10.1039/C3CE42347F

——————————————————————————————————————————————————————-

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 Jamie Humphrey

I am delighted to announce the appointment of Sarah Ruthven as Editor for CrystEngComm.

Sarah joined the Royal Society of Chemistry in 2005 where she has been responsible for the successful development of journals such as Green Chemistry and Photochemical & Photobiological Sciences. In recent years, Sarah launched RSC Advances which has now become the largest journal published by the Royal Society of Chemistry!

Sarah will be supported by Deputy Editor, Fiona McKenzie and Development Editor, Guy Jones; in addition to Editorial Production Manager, Andrew Shore and his team of Publishing Editors. I strongly believe that with Sarah’s high enthusiasm and exceptional record of “getting things done”, CrystEngComm will thrive.

Some of you may be wondering what I will be doing as I am no longer CrystEngComm Editor. I recently accepted a position as Publisher here at the Royal Society of Chemistry, with the overall responsibility for about a third of our journals, including CrystEngComm.  My move from Editor to Publisher is with mixed feelings. I am very excited about my new role however I will very much miss the day-to-day involvement with the journal and crystal engineering community.  My time as CrystEngComm Editor has been immensely enjoyable, and I owe you all a great deal of thanks for making it so and for all your support for the journal. Thank you!

 With thanks

 Jamie

Sarah Ruthven

Jamie Humphrey

Posted on behalf of Josh Campbell, web writer for CrystEngComm 

Researchers in the field of nanophotonics aim to control photons or optical energies at the nanometre scale by using devices; typically 1D nanomaterials such as nanotubes or nanowires. Due to the nanoscopic nature of such materials, the quantum confinement effect allows fascinating properties to emerge which can be harnessed to produce ultra-fast, low-power and interference-free devices.

An integral part of any nanophotonic device is the waveguide, a physical structure that guides the photons to their target location. Waveguides can be active, guiding photons via coupling mechanisms, or passive, propagating the source light directly through the material.

Of all the classes of waveguide materials, inorganic devices are the most common, however recent research into waveguides made from small molecule organics is gaining traction. The advantages of these organic devices over existing inorganic materials are that they are easier to produce and have tuneable properties arising from greater variations in molecular structure.

For the emerging field of biophotonics, biocompatibility is a key requirement, with non-toxic pharmaceutical molecules being a logical fit for the role but not having been well explored.

In a recent article in CrystEngComm, researchers from the Rajadurai and Chandrasekar groups evaluated three pharmaceutical molecules as biophotonic devices: caffeine, carbamazepine and gilbenclamide, with nanoscale samples of each molecule grown via drop-casting on a clean glass slide.

The researchers found that crystal growth was governed by kinetic factors which often left the sample with defects which are compounded by defects created by the source of radiation used to examine the structures. To overcome this, the authors used a novel method of Raman laser light confinement to characterise the compounds.

All three molecules exhibited tubular morphologies which, in the case of carbamazepine, measured hundreds of microns in length. Passive waveguiding was observed via 2D optical confinement in all samples and no unnatural defects were observed when the samples were subjected to Raman spectroscopy.

The potential of these materials to act as biocompatible optical waveguides will hopefully bring the first biophotonic nano-devices significantly closer to realisation.

Read the full article now for more details: 

Passive optical waveguiding tubular pharmaceutical solids and Raman spectroscopy/mapping of nano-/micro-scale defects
Naisa Chandrasekhar, E. Ramanjaneya Reddy, Muvva D. Prasad, Marina S. Rajadurai and   Rajadurai Chandrasekar 
CrystEngComm, 2014, DOI: 10.1039/C4CE00084F

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

Nanometer- or micrometer-sized particles, doped with a small quantity of rare-earth cations, exhibit two types of luminescence. Where the light absorbed is of higher energy than the light emitted (known as down-conversion or DC) the materials can be used in lighting and displays.  If the light absorbed is of lower energy than the light emitted (up-conversion or UC), the materials can be used in photonics and biological imaging.  The luminescence behaviour depends on the composition, size and shape of the particles and the rare-earth ion (or ions) used for doping.

Lanthanide oxyfluorides, such as YOF, are attractive candidates for the host particles, due to their high stability and good transparency.  These materials have been prepared with various particle sizes but using harsh conditions and complicated processes which can, crucially, leave behind traces of the organic molecules used to control morphology.  These can be detrimental to the physical and chemical properties of the final product.

A new paper shows how a simple hydrothermal method can be used to prepare YOF particles with controllable size and shape, determined by altering the pH of the reaction mixture and without the need for organic shape-directing reagents.   At pH 9 microrods form, while at pH 11 the particles form as nanospheres and at pH 14 there is a mixture of the two morphologies.  The UV luminescence properties of samples doped with the rare-earth cations Tm³⁺, Tb³⁺ or Eu³⁺show characteristic blue, green or red DC emissions. Samples doped with two different rare earth cations, under lower energy excitation,  show red, blue and green UC emissions for Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺ and Yb³⁺/Ho³⁺ doped particles, respectively (see diagram below).

The emission intensities are related to the particle size and the number of surface defects (which lead to quenching of the luminescence).  Intensities are therefore highest for the microrods which are largest and have fewest defects.  Authors conclude that the YOF particles prepared are excellent host lattices for efficient luminescence which could find application in colour displays and anti-counterfeit labels.

For more details see the paper at:

YOF nano/micro-crystals: morphology controlled hydrothermal synthesis and luminescence properties

Yang Zhang, Xuejiao Li, Dongling Geng, Mengmeng Shang, Hongzhou Lian, Ziyong Cheng and Jun Lin

CrystEngComm, 2014, Advance Article
DOI: 10.1039/C3CE42323A, 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