CrystEngComm Blog

Posted on behalf of Gwenda Kyd, web writer for CrystEngComm

Controlling the size and shape of crystals is useful when these factors are related to properties of interest, such as luminescence. In the case of hexagonal sodium yttrium fluoride (β-NaYF₄), the upconversion luminescence (i.e. conversion of longer wavelength infra-red radiation to shorter wavelength visible light) varies with the size and morphology of the microcrystals.

A new paper shows how the morphology can be conveniently and predictably varied by altering the ratio of NaF to RE ³⁺ (where RE³⁺ is the total amount of Y³⁺ and dopant Yb³⁺ and Er³⁺) in a simple hydrothermal synthesis. Changing this ratio leads to the formation of tubes, spheres, rods, bipyramids, plates and prisms of different sizes. In the paper, the authors also suggested a potential mechanism for formation of the different morphologies. As shown in the figure below, the upconversion emissions of green and red light vary for these morphologies.

For more details see the full paper:

Controllable synthesis, formation mechanism and upconversion luminescence of β-NaYF₄ : Yb³⁺/Er³⁺ microcrystals by hydrothermal process
Mingye Ding, Chunhua Lu, Linhai Cao, Yaru Ni and Zhongzi Xu
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41427B, 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

Lithium ion batteries (LIB) are ubiquitous in modern life. Consumer electronics generally use LIBs based on LiCoO2 but these have safety drawbacks and environmental concerns. NiO has been proposed as a replacement material for the anode due to its safety, low cost and theoretical capacity. However bulk NiO has poor electrochemical performance and much research has been focused on developing nanostructures that would allow NiO to reach its full potential. Porous hollow materials can offer many improvements compared to the bulk such as improved capacity and cycling performance.

A new paper presents the synthesis of NiO porous hollow microspheres using L-cysteine as a directing agent. The directing agent causes the spheres to form, as without it the precursors to NiO grow into nanoplate-assembled flowers. The authors propose a mechanism for the sphere formation: L-cysteine complexes with Ni(OH)2, which during hydrothermal treatment aggregate due to the hydrophobic interactions of the L-cysteine. These continue to aggregate throughout treatment and assemble into spheres. The NiO microspheres showed improved reversibility and good capacity retention. The authors attribute the improved performance to the hollow architecture which allows for fast ion/electron transfer.

Find out more from the paper:

L-cysteine-assisted preparation of porous NiO hollow microspheres with enhanced performance for lithium storage
Dong Xie, Qingmei Su, Zimin Dong, Jun Zhang and Gaohui Du
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41161C, 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

Non-linear optical (NLO) materials are in demand due to their potential applications in photonic technologies such as laser frequency conversion and signal communication. Chiral coordination networks are likely to have good NLO properties but their formation from achiral building blocks (tectons) can be difficult.

A new paper presents a systematic study of Cd-complexes containing a range of related tetrazolate tectons, with different substituents, allowing the importance of steric and electronic factors to be considered. One molecular structure and three framework structures were formed. The size of the substituent is significant here, with smaller substituents favouring the formation of network structures. In these network structures, which crystallise in chiral space groups, the framework where the tecton has the strongest electron withdrawing substituent shows the highest second harmonic generation SHG efficiency. This compound is also phasematchable, a characteristic necessary for a laser frequency conversion material.

For more information see the paper at:

From achiral tetrazolate-based tectons to chiral coordination networks: effects of substituents on the structures and NLO properties
Jian-Zhen Liao, Da-Chi Chen, Fang Li, Yong Chen, Nai-Feng Zhuang, Mei-Jin Lin and Chang-Cang Huang
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41037D, 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

Ditopic ligands (ligands capable of coordination at two separate sites) allow the creation of well-ordered extended complexes containing different cations. They are usually N-, P-, O-, and S-containing (or in their N, O-, N, S,- and N, P-combinations) organic molecules, and have been used in various applications such as monitoring guest exchange and the creation of metal organic frameworks. The multi-centre nature of these ligands allows for other interactions outside of coordinative and hydrogen bonding such as halogen bonding. 3-(4-pyridyl)-2,4-pentanedione (HacacPy) is a well known ditopic ligand, and in this new work, has been used to create a crystal in which these three types of bonding are represented.

Three complexes containing HacacPy and tetrafluorodiiodobenzene (TFDIB) were prepared. Compound 1 showed the halogen bonding produced between the pyridine N and the iodine of TFDIB with this being the only coordination centre used. In compound 2 HacacPy is deprotonated and is involved in coordinative bonding using the acac part of the ligand and two pyridine N atoms form halogen bonds to TFDIB producing chains. Compound 3 introduces a third interaction, hydrogen bonding of a Py N to a solvent molecule which is in turn halogen bonded to a TDIB which is halogen bonded to another Py N. The authors analysed the charge density of 3 and provided the first tentative experimental results of the effect of metal coordination on halogen bonds.

Find out more from the paper:

3-(4-Pyridyl)-2,4-pentanedione – a bridge between coordinative, halogen, and hydrogen bonds
Carina Merkens, Fangfang Pan and Ulli Englert
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41306C, 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

Tungsten oxide hydrates (like WO₃•nH₂O, n=0-2) show promising photocatalytic properties. They efficiently oxidise a range of organic compounds including textile dyes and bacterial pollutants when irradiated with blue light and also have potential use in the treatment of acid polluted solutions. An understanding of the structure dependent nature of the activities is required to fully develop them and new preparation methods can facilitate this. Microwave heating methods are attractive as they increase reaction rates and improve the yields and purity of products.

This new paper shows how microwave assisted synthesis of WO₃•0.33H₂O can efficiently produce orthorhombic crystallites. The products of syntheses with and without microwave heating via three different methods were compared. In each case, different particle sizes and morphologies were formed. For each of the pairs (with or without microwave heating), the photocatalytic properties were enhanced for the products of the microwave-assisted synthesis. Authors suggest this is due to the preferential growth along the (100) face exposing more of the highly acidic (010) faces.

For more details see the paper at:

Microwave-assisted growth of WO₃·0.33H₂O micro/nanostructures with enhanced visible light photocatalytic properties
Jiayin Li, Jianfeng Huang, Jianpeng Wu, Liyun Cao, Qijia Li and Kazumichi Yanagisawa
CrystEngComm, 2013, Advance Article
DOI: 10.1039/C3CE41005F, 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.