Water is the renewable, bulk chemical that nature uses to enable carbohydrate production from carbon dioxide. The dream goal of energy research is to transpose this incredibly efficient process and make an artificial device whereby the catalytic splitting of water is finalized to give a continuous production of oxygen and hydrogen. Success in this task would guarantee the generation of hydrogen as a carbon-free fuel to satisfy our energy demands at no environmental cost. Here we show that very efficient and stable nanostructured, oxygen-evolving anodes are obtained by the assembly of an oxygen-evolving polyoxometalate cluster (a totally inorganic ruthenium catalyst) with a conducting bed of multiwalled carbon nanotubes. Our bioinspired electrode addresses the one major challenge of artificial photosynthesis, namely efficient water oxidation, which brings us closer to being able to power the planet with carbon-free fuels.

The use of plasmonic metal nanoparticles as photosensitizers has undergone a strong development in the last few years given their ability to increase the activity of semiconductors into the visible and near infrared regions. The present work reports an experimental and theoretical study on the critical influence that shape anisotropy of gold nanoparticles exerts on the photocatalytic performance of Au-TiO2 nanoarchitectures. The obtained results show

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Metallic nanoparticles exhibit exceptional optoelectronic properties with applications in plasmonics, biosensing and nanomedicine. Recently, new synthesis techniques have enabled precise control over the sizes and shapes of metal nanoparticles, occasionally leading to morphologies that cannot be properly characterized using standard techniques. An example is five-fold-twinned decahedral Au nanoparticles, which are intrinsically strained as a result of their unique geometry. Various competing models have been proposed to predict the strain states of such nanoparticles. Here, we present a detailed analysis of the internal structure of a decahedral Au nanoparticle using aberration-corrected high-resolution electron microscopy and strain mapping. Our measurements confirm the presence of a disclination, which is consistent with the commonly accepted strain model. However, we also observed shear gradients, which are absent from the models. By comparing our local strain determinations with finite-element calculations, we show the effect of elastic anisotropy on the strain state in these nanoparticles.

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Gold nanorods with well‐defined aspect ratios are homogeneously incorporated within poly(vinyl alcohol) thin films and subsequently aligned by heating and stretching the nanocomposite films. The spatial alignment of the nanorods is directly proved using transmission electron microscopy. The polarization‐dependent optical response of the rods is measured and compared with a dipole model. Excellent agreement is found. Additionally, irradiation of the film with nanosecond laser pulses (1064 nm) leads to selective reshaping of the nanorods into nanospheres, and we demonstrate that this effect can be used to micropattern optical structures into the films.

Plasmon modes of the exact same individual gold nanoprisms are investigated through combined nanometer-resolved electron energy-loss spectroscopy (EELS) and cathodoluminescence (CL) measurements. We show that CL only probes the radiative modes, in contrast to EELS, which additionally reveals dark modes. The combination of both techniques on the same particles thus provides complementary information and also demonstrates that although the radiative modes give rise to very similar spatial distributions when probed by EELS or CL, their resonant energies appear to be different. We trace this phenomenon back to plasmon dissipation, which affects in different ways the plasmon signatures probed by these techniques. Our experiments are in agreement with electromagnetic numerical simulations and can be further interpreted within the framework of a quasistatic analytical model. We therefore demonstrate that CL and EELS are closely related to optical scattering and extinction, respectively, with the addition of nanometer spatial resolution.

Multipod Au nanoparticles (nanostars) with single crystalline tips were synthesized in extremely high yield through the reduction of HAuCl 4 in a concentrated solution of poly(vinylpyrrolidone) (PVP) in N,N-dimethylformamide (DMF), in the presence of preformed Au nanoparticle seeds, but with no need for external energy sources. Nanostar dispersions display a well-defined optical response, which was found (through theoretical modeling) to comprise a main mode confined within the tips and a secondary mode confined in the central body. Calculations of the surface enhanced Raman scattering (SERS) response additionally show that this morphology will be relevant for sensing applications.