Self-assembly of porphyrin-DNA hybrids into large flat nanostructures.

The main aim of nanotechnology is to create functional systems by controlling the matter at the nanometer level. In this context DNA is a versatile building block for the fabrication of micrometer-scale objects with a subnanometer-scale resolution. Over the last 15 years, DNA nanotechnology has considerably developed with the invention of DNA origami, double crossover structures and molecule/oligonucleotide hybrids. Our interest is focused on the combination of short complementary DNA sequences with organic molecules with a view to create large self-assembled nanostructures. Here we report on the synthesis of porphyrin derivatives bearing up to four 21-mer oligonucleotides and we demonstrate that the combination of the molecular hybrids containing complementary DNA strands leads to the formation of large nanostructures with micrometer-scale size.

Inkjet Printing NiO-Based p-Type Dye-Sensitized Solar Cells.

Fabrication at low cost of transparent p-type semiconductors with suitable electronic properties is essential toward the scalability of many electronic devices, especially for photovoltaic and photocatalytic applications. In this context, the synthesis of mesoporous NiO films through inkjet printing of a sol-gel ink was investigated for the first time. Nickel chloride and Pluronic F-127, used as nickel oxide precursor and pore-forming agent, respectively, were formulated in a water/ethanol mixture to prepare a jettable ink for Dimatix printer. Multilayer NiO films were formed, and different morphologies could be obtained by playing on the interlayer thermal treatment. At low temperature (30 °C), a porous nanoparticulate-nanofiber dual-pore structure was observed. On the other hand, with a high temperature treatment (450 °C), nanoparticulate denser films without any dual structure were obtained. The mechanism for NiO formation during the final sintering step, investigated by means of X-ray photolectron spectroscopy, shows that a Ni(OH)2 species is an intermediate between NiCl2 and NiO. The different morphologies and thicknesses of the NiO films were correlated to their performance in a p-DSSC configuration, using a new push-pull dye (so-called "RBG-174") and an iodine-based electrolyte. Moreover, the positive impact of a nanometric NiOx layer deposited by spin-coating and introduced between FTO and the NiO mesoporous network is highlighted in the present work. The best results were obtained with NiOx/four layer-NiO mesoporous photocathodes of 860 nm, with a current density at the short circuit of 3.42 mA cm-2 (irradiance of 100 mW cm-2 spectroscopically distributed following AM 1.5).

SWNT array resonant gate MOS transistor.

We show that thin horizontal arrays of single wall carbon nanotubes (SWNTs) suspended above the channel of silicon MOSFETs can be used as vibrating gate electrodes. This new class of nano-electromechanical system (NEMS) combines the unique mechanical and electronic properties of SWNTs with an integrated silicon-based motion detection. Its electrical response exhibits a clear signature of the mechanical resonance of SWNT arrays (120-150 MHz) showing that these thin horizontal arrays behave as a cohesive, rigid and elastic body membrane with a Young's modulus in the order of 1-10 GPa and ultra-low mass. The resonant frequency can be tuned by the gate voltage and its dependence is well understood within the continuum mechanics framework.