CrystEngComm Blog

It gives us great pleasure to assemble a series of issues of CrystEngComm that celebrates 2014 as the International Year of Crystallography (IYCr2014).

Since its inception in 1999, CrystEngComm has been the go-to journal for publishing the highest-quality work in crystal engineering. It was the first online-only journal of the Royal Society of Chemistry and was among the very first to spur and foster an online scientific community.

During the last 15 years, CrystEngComm has witnessed and ushered explosive growth in the field of crystal engineering, as demonstrated by the increase in number of articles published from 9 in 1999 to 1325 in 2013. Indeed, the field of crystal engineering itself now has a highly-successful Gordon Research Conference (GRC) devoted to the subject. Clearly, the launch of CrystEngComm has supported crystal engineering and its numerous sub-areas as the field has developed.

A celebration provides an opportunity to both reflect and look forward. I personally recall travelling as an undergraduate student on a flight to a Chemical Institute of Canada Conference in 1992 and sitting next to a professor who was also travelling to attend the meeting. At that time, I was just beginning to learn how to grow single crystals, as well as collect and solve X-ray data. Our experiments in those days were conducted on a conventional Enraf-Nonius CAD-4 point-detector diffractometer. Data collection times were on the order of days to weeks.

While I had only been a researcher for about one year, in a conversation with the professor I was comfortable enough to remark that, “You really gain a great deal of confidence about chemistry once you have determined a crystal structure”. Clearly, I was already ‘hooked’, at an early stage, by the process of gathering and analysing X-ray data and the insight gained from the X-ray experiment.

Over the past 15 years, CrystEngComm has made many strides scientifically, meaning that we are able to readily draw on an international community to celebrate IYCr2014. To that end, we have assembled a series of issues edited by prominent researchers in crystal engineering that provide a global celebration from regions including:

Each issue contains a series of papers that reflects the wide breath and scope of crystal engineering and modern crystallographic techniques being studied in each region.

Our deepest thanks and gratitude are extended to the Guest Editors (pictures L-R below):

• Michaele Hardie, University of Leeds, UK (CrystEngComm Editorial Board Member)
• Dario Braga, University of Bologna, Italy (first CrystEngComm Scientific Editor)
• Rahul Banerjee, CSIR-National Chemical Laboratory, India (CrystEngComm Associate Editor)
• J. J. Vittal, National University of Singapore, Singapore
• Stuart Batten, Monash University, Australia
• Christer Aakeröy, Kansas State University, USA (CrystEngComm Associate Editor)
• Tomislav Friščić, McGill University, Canada (CrystEngComm Editorial Board Member)

As well as the CrystEngComm staff, for their dedication and hard work to bring such a global effort together.

Guest Editors of IYCr themed issues

All four IYCr14 themed issues have been very successful and I encourage you to take an opportunity to review all of them.

Much change has been realized in crystal engineering and X-ray diffraction during the past two decades. A major change in this regard has been the implementation of charge-coupled device (CCD) detectors, which enable typical data collection times on the order of hours versus days or weeks. The number of structures in the Cambridge Structural Database (CSD) has increased from roughly 200,000 to 700,000 during the time period (one million is coming quickly), which provides the all-important data for crystal engineers to develop improved understandings of structural relationships between solids.

Moreover, with data collection times becoming shorter and shorter, the field of crystal engineering can be expected to deliver even greater insights into the structures and dynamics of crystalline solids. Let us keep each other posted in CrystEngComm.

Leonard R. MacGillivray, Chair, CrystEngComm Editorial Board

A new paper by Behrens and co-workers in CrystEngComm details the modulated syntheses of a Zinc-fumarate MOF in both water and DMF. The authors performed kinetic studies for each synthesis, showing that, contrary to what was expected, the modulator increased the rate of formation of the MOF in DMF.

Modulating agents (usually monocarboxylic acids) are added to a MOF reaction mixture to increase the reproducibility and crystallinity of the final product. In coordination modulation, the modulating agent competes with the organic linkers in binding to the metal centre, preventing the formation of impurities but slowing down the reaction. In this current work, the authors chose formic acid as their modulator and performed in situ energy dispersive x-ray diffraction, which allowed for quantitative kinetic data to be produced.

When the authors carried out the synthesis in water, the modulating agent behaved as expected, decreasing the nucleation and growth rates as the formic acid concentration increased. However, when formic acid was added to the DMF-containing reaction mixture, the rate of growth increased. The authors theorise this occurs due to trace water in their commercial formic acid which they investigated by keeping the formic acid concentration constant but increasing water content. This showed remarkable results, increasing the rate constant by 2 orders of magnitude.

By observing that both the presence of a modulator and the water concentration have a large effect on the crystal formation, the authors added to the body of evidence that successful MOF syntheses are highly dependent on subtle changes in reagents and conditions.

Read the full article to find out more

Insight into the mechanism of modulated syntheses: in situ synchrotron diffraction studies on the formation of Zr-fumarate MOF
Gesa Zahn, Philip Zerner, Jann Lippke, Fabian L. Kempf, Sebastian Lilienthal, Christian A. Schröder, Andreas M. Schneidera and Peter Behrens
CrystEngComm, 2014, 16, 9198-9207

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.

Posted on behalf of Josh Campbell, web writer for CrystEngComm 

A new paper in CrystEngComm details the successful synthesis of tungsten oxide (WO₃) mixed amorphous/crystalline nanostructures. These 1D, hexagonal nanorods show electrochromic performances that combine the high optical modulation and quick response times of amorphous WO₃ with the improved stability of crystalline phases.

Researchers synthesised the nanostructures using a two-step hydrothermal process by growing the crystalline core first before the amorphous shell on the rod’s surface. They found that the thickness of the amorphous shells could be varied by altering the length of the second step. They used sodium cations to stop the conversion of the hexagonal WO₃ phase to the monoclinic form encouraging the formation of the rod architectures by promoting growth along the c-axis.

The large surface area of the amorphous shells allowed for rapid bleaching and coloration as most of the electrolyte ions were kept away from the surface of the core. The cores of the structures helped increase the stability of the material by increasing its density and crystallinity.

Getting a balance between amorphous and crystalline properties is important in electrochromic device performance. Materials scientists have studied amorphous WO₃ thin films extensively as they show fast response times and high coloration efficiency. Unfortunately they make for unstable devices due to their disordered structures.

Researchers have since discovered that crystalline WO₃ offers much better stability due to its dense and ordered structure but lacks the performance needed for practical applications. Nanostructures with the best of both worlds may allow increased property control and performance in future devices.

Read the full article for more details: 

Facile synthesis of one-dimensional crystalline/amorphous tungsten oxide core/shell heterostructures with balanced electrochromic properties
Yung-Chiun Her and Chia-Chun Chang
CrystEngComm, 2014, DOI: 10.1039/C4CE00430B 

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.

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.

Posted on behalf of Josh Campbell, web writer for CrystEngComm 

Graphene is a material composed of single of 2D sheets of graphite which showcases a number of exotic properties. These include: ballistic transport of charge, which occurs partially due to the material having a lower resistivity than that of silver; an anomalous quantum Hall effect and spin transport. Single crystals of graphene can be grown using chemical vapour deposition (CVD) on a variety of substrates although the material is perhaps more famously known for being prepared from graphite using adhesive tape in a process called exfoliation. These different methods of preparation influence the final properties of the material; with CVD-produced samples often having lower mobilities than exfoliated samples, which are smaller. Epitaxy, the process of growing one crystalline material on another with recognition of some form between the layers, is another viable method of graphene synthesis, with heteroepitaxal growth having been investigated for a variety of different substrates. In this vein, it has been postulated that growing “graphene-on-graphene” could offer methods for both investigating the mechanism of graphene growth and producing large single crystal samples. 

A recent article in CrystEngComm reports how homoepitaxal growth can proceed from both exfoliated and CVD grown samples of graphene. In the study, an exfoliated or CVD-grown seed was placed onto a copper foil surface and heated to 1025 °C in the presence of H₂ and CH₄. By investigating the atomic structure around the newly grown graphene, the authors showed that the crystal orientation was preserved from the original graphite flake and the graphene sheet, with graphene layers 1-2 sheets thick being made regardless of the method used. The authors subsequently used the result to grow large films of graphene epitaxally. A close examination of the atomic structures of both the seed and the newly grown graphene showed that the original crystal orientation was preserved during growth. It is hoped that this new method of homoepitaxal graphene growth will allow for much larger and higher-quality samples of crystalline material to be grown in the future. 

Read the full article now for more details: 

Lateral homoepitaxial growth of graphene
H. Wang, G. Wang, P. Bao, Z. Shao, X. Zhang, S. Yang, W. Zhu and   B. Deng
CrystEngComm, 2014, DOI: 10.1039/C3CE42072H

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.