Highlights
Nigel P Freestone University of Northampton, UK
Applied highlights
Squid skin coating invisible to IR Using a protein from colour-changing squids, US scientists have created a coating that reflects infrared and lets objects mimic the infrared signature of their surroundings that it could be used to create camouflage that would make people and vehicles invisible to infrared cameras (L. Phan, W. G. Walkup, D. D. Ordinario, E. Karshalev, J-M. Jocson, A. M. Burke, A. A. Gorodetsky; Adv. Mater., doi: 10.1002/adma.2013014720) (Scheme 1). Conventional visual camouflage can help the wearer blend in to the background, but it is notoriously difficult to hide from infrared sensors. Pencil squids, for example, have specialised skin cells that can reflect both visible light and infrared. These cells have highly folded membranes, which form finger-like lamellae containing a protein called reflectin, which has a high refractive index. Layers of extracellular space between the lamellae have a low refractive index, so combined these structures act like Bragg reflectors. These layered structures produce strong colours, and the squids use muscular contractions to alter the spacing of these layers to rapidly change colour. The new coating utilises thin films of
reflectin to make a stripped down mimic of squid skin. The ‘skin’ is created by depositing the protein on a graphene oxide layer, which was itself laid down on a glass or silica substrate. The graphene oxide acts like the dark pigments found under the reflectin- containing layers of squid skin, acting as permanent contrast to the colour- changing cells. They then investigated how different substances could chemically alter and ‘tune’ the film’s structure and reflective properties. Exposing the film to acetic acid vapour caused it to swell enough to reflect infrared radiation, allowing it to ‘disappear’ when viewed with an infrared camera.
Although at an early-stage, this technology shows promise as a next- generation camouflage coating. The next challenge is to find a more user-friendly
54 Chemistry&Industry • November 2013
Graphene Oxide
Substrate Acid vapour
trigger. Instead of acetic acid, the scientists are seeking a mechanical or electrical stimuli to induce the same change in colouration.
Magnetic crude oil sponge Magnetic foams, which can absorb up to 100 times their weight in oil, have been created by Chinese chemists (N. Chen, Q. Pan; ACS Nano, 2013, 7, 6875). The ultralight (95mg/cm3
), magnetic Fe2O3
/C, Co/C, and Ni/C foams, with a density <5 mg cm-3
, are available through
the pyrolysis of commercial polyurethane sponge grafted with polyelectrolyte layers based on the corresponding metal acrylate at 400°C. The ultralight foams consist of 3D
interconnected hollow tubes that have a diameter of micrometer and nanoscale wall thickness, forming hierarchical structures from macroscopic to nanometer length scales (Scheme 2). Wall thickness and morphology of the microtubes can be tuned by controlling the concentrations of
Scheme 1
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acrylic acid and metallic cations. After modification with low-surface-
energy polysiloxane, the ultralight foams exhibit superhydrophobicity and superoleophilicity, which quickly and selectively absorbs a variety of oils from a polluted water surface under magnetic field.
By controlling the composition and conformation of the grafted polyelectrolyte layers, the present approach is extendable to fabricate a variety of ultralow-density materials desirable for absorptive materials, electrode materials and catalyst supports.
Catalytic conversion of ethanol into an advanced biofuel Unprecedented selectivity of over 94% at good (20%+) conversion has been observed for the upgrade of ethanol to the advanced biofuel 1-butanol with a new ruthenium–bis(diphenylphosphanyl) methane catalyst at 150o
C in the presence
of EtONa (5molwt%) (G. R. M. Dowson, M. F. Haddow, J. Lee, R. L. Wingad, D. F. Wass; Angew. Chem. Int. Ed. Engl., 2013, 52, 9005) (Scheme 3). Preliminary mechanistic studies
indicate that control over the notoriously uncontrolled acetaldehyde aldol condensation is critical for the high selectivity, and evidence was found for an on-metal condensation step.
dicarboxylate)- void = 75%, 2215m2 (OH)4 (H2 O)2 (L)6 ]n Scheme 2
MOF capture of VOCs Efficient air filters for the protection against chemical warfare agents might be achieved by surface functionalisation of the pores in robust metal–organic frameworks with fluoroalkyl residues [[Ni8
(L=arene- /g]
and the precise control of their pore size (N. M. Padial, E. Q. Procopio, C. Montoro, E. López, J. E. Oltra, V. Colombo, A. Maspero, N. Masciocchi, S. Galli, I. Senkovska, S. Kaskel, E. Barea, J. A. R. Navarro; Angew. Chem. Int. Ed. Engl., 2013, 52, 8290) (Scheme 4). These MOFs capture harmful volatile
organic compounds even under extremely moist conditions (80 % relative humidity).
Smallest magnetic stir bars A simple and scalable method has been developed for fabricating Fe3
nanoparticle magnetic stir bars, which are tunable from 75nm–1.4μm in width and up to around 17μm in length (W. H. Chong, L. Ket Chin, R. L. S. Tan, H. Wang,
O4
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