A review of the electrical properties of semiconductor nanowires: insights gained from terahertz conductivity spectroscopy View the table of contents for this issue, or go to the journal homepage for more 2016 Semicond. Sci. Technol. 31 103003

The photograph shows a polymer reflector that mimics the colour and underlying molecular structure of a golden beetle. It is formed from self-organizing layers of photopolymerised liquid crystal. These require an aligning layer, but we show that a layer of the material can be used as to self-align subsequent coatings, enabling the construction of complex structures by sequential coating of engineered materials.

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High surface area metals are of great importance for applications ranging from catalysts and electrodes to sensors or biomaterials. Many patents and scientific papers are devoted to a range of manufacturing approaches commonly involving multistep processing under harsh conditions, lacking general applicability and bearing the potential for contamination. Here we demonstrate the fabrication of porous metal layers by anodization at moderate voltages in highly concentrated acids. Porous metal layers were produced on copper, silver, iron and nickel using 99% phosphoric and sulfuric acids. The porous layer thickness can be tuned up to over one micrometer. Structures develop in 4 to 30 minutes independent of substrate purity or crystallographic features. The mechanism is believed to involve templated etching due to a near-stagnant bubble layer in a highly viscous electrolyte near the anode. It is therefore not dependent on any particular chemistry, as long as anodic oxygen bubbles are evolved at a sufficient rate. Since the principal processes of electropolishing are still operational, the surfaces remain flat at a larger scale, even though the optical properties (reflectivity, SERS activity) have changed significantly. Our method is reproducible, cheap, clean, fast and versatile, leading to a wider range of applications for porous metal surfaces.