Journal of Materials Chemistry Blog

Hydrophobic cellulose nanocrystals modified with quaternary ammonium salts

Cellulose nanocrystals or CNCs are environmentally friendly biomaterials whose surface functionality can be tailored in order to improve their performance.  In this hot paper, Zhou and co-workers describe a simple and flexible route to produce CNCs bearing high carboxylate content.  A new environmentally friendly method for the surface modification of the produced CNCs is reported.  Modifying the surface of the CNCs using a range of quaternary ammonium salts via ionic exchange in aqueous solution, gives a series of CNCs that can be redispersed and individualised in organic solvents.  These CNCs can be dried from solvent to form well-disperesed nanocomposites.

(J. Mater. Chem., 2012, 22, 19798–19805)

A green-yellow emitting oxyfluoride solid solution phosphor Sr₂Ba(AlO₄F)_1-x(SiO₅)_x:Ce³⁺ for thermally stable, high color rendition solid state white lighting

LEDs are increasing in use over traditional incandescent or fluorescent light sources because of their reduced energy demands.  Solid state white lighting devices offer many advantages compared to these conventional sources such as longer lifetimes and no need for mercury.  Most common white lighting phosphors strongly absorb blue light, in this hot paper, Seshadri et al. report a green-to-yellow emitting phosphor solid solution.  The composition (x) of the phosphor can be altered to easily tune the colour of the phosphor between near-UV excitation and green/yellow emission wavelengths which are optimal for white lighting applications.

(J. Mater. Chem., 2012, 22, 18204–18213)

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Atomic layer deposition of anatase TiO₂ coating on silica particles: growth, characterization and evaluation as photocatalysts for methyl orange degradation and hydrogen production

Photocatalysis using various forms of titanium dioxide is well known, but many of these forms, such as TiO₂ thin films or the commercially available Degussa P25 powder, have small particle sizes which makes recovery and handling a challenge. In this hot paper, Rosseinsky and co-workers utilise TiO₂–SiO₂ core-shell particles to produce an efficient photcatalyst which can be easily separated from aqueous solution. They use atomic layer deposition to deposit anatase TiO₂ layers onto SiO₂ support particles. The particles can photocatlyse methyl orange with nearly ten times greater efficiency compared to P25 when normalised for TiO₂ content.

(J. Mater. Chem., 2012, 2, 20203–20209). Read for free until October 26th!

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High throughput theory and simulation of nanomaterials: exploring the stability and electronic properties of nanographene

Computational modelling of structure-activity relationships in nanomaterials can be challenging.  Snook and co-workers have developed a high throughput method by using a combinational approach with electronic structure simulations to give a general method for predicating and understanding the properties of graphene.  They describe the calculation for a predictive property matrix of graphene quantum dots using SCC-DFTB. Alternative graphene structures with AC- and ZZ-edges are able to be modelled without increasing the methodological complexity.  This hot paper shows that a database of electronic properties of graphene can be built up, and when a particular property is desired it can be readily obtained.

(J. Mater. Chem., 2012, 22, 18119–18123)

Living materials from sol–gel chemistry: current challenges and perspectives

In this Highlight article, Marine Blondeau and Thibaud Coradin discuss the use of sol–gel encapsulation technology for biomedical and environmental applications.  They discuss the topic from a materials point-of-view, outlining the key points of the encapsulation process and the formation of gels from sols.  The challenges, possibilities and advances in the field are also discussed.

(J. Mater. Chem., 2012, DOI: 10.1039/C2JM33647B, Advanced Article)

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Quiescent water-in-oil Pickering emulsions as a route toward healthier fruit juice infused chocolate confectionary

Finding alternatives to the calorie-rich triglyceride fats found in chocolate are a high priority for chocolate manufacturers. In this hot paper, Bon and co-workers introduced fruit juice into chocolate by forming stable water-in-oil emulsions. The infused fruit juice replaces up to 50 % by weight of the total fat content in the chocolate. The approach uses a quiescent Pickering emulsion fabrication strategy to infuse the fruit juice in the form of emulsion droplets. White, milk and dark chocolate is produced using this method, which can also be applied in other systems such as aqueous acetic acid dispersed in sunflower oil.

(J. Mater. Chem., 2012, DOI: 10.1039/C2JM34233B, Advanced Article)

Electrospinning of in situ crosslinked collagen nanofibers

The high porosity and large surface area of non-woven collagen fibers makes them excellent scaffolds for tissue engineering and regenerative medicine. When collagen is regenerated by electrospinning the fibers are not resistance to water, thus undergo dissolution and have poor mechanical firmness. In this hot paper, Wnek and co-workers report a single-step method of electrospinning crosslinked collagen fibers in situ. The crosslinked fibers exhibited swelling when placed in water, in contrast to the dimensional shrinking often seen in post-crosslinked electrospun collagen. Importantly, the porosity of the fibers was also maintained during water treatment. The team suggest the crosslinking technique could also be applied to other biomaterials for tissue engineering.

(J. Mater. Chem., 2012, DOI: 10.1039/C2JM31618H, Advanced Article)

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Multifunctionalization of carbon nanotube fibers with the aid of graphene wrapping
The excellent mechanical and electrical properties of carbon nanotubes is harnessed in a range of applications from advanced textiles through to supercapacitors, and artificial muscles. However, the mechanical properties of the CNT fiber can be affected by chemical modification of the CNTs, and the fabrication and performance depend strongly on the morphology of the fiber surface. In this hot paper Xiaohua Zhang, Qingwen Li and co-workers report a new method to modify the surface roughness and level of functionalization of CNT fibers, by wrapping them in graphene oxide or reduced graphene. The introduction of a graphene layer also has smoothing and shield effects, resulting in higher tensile strength and improved and stabilized performance. The nanotubes can also be further functionalised with polyaniline or TiO₂ nanoparticles.
(J. Mater. Chem., 2012, 22, 16277-16282)

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