Photolithographic nanoseeding method for selective synthesis of metal-catalysed nanostructures.

In this work we present a general method for the selective synthesis by photolithography of localised nanostructures in planar geometries. The methodology relies on the previous concept of photo-patternable metallic nanoparticle (NP)/polymer nanocomposites, which can provide a range of NP sizes, polydispersity and densities. First, a photoresist containing metallic ions is patterned by photolithography. Silver NPs are synthesised in situ after the exposure and development of the patterned thin film via the thermal-induced reduction of ions embedded in its structure. Gentle plasma ashing is used to selectively remove the polymer, which leaves NPs on the patterned areas. These NPs are used as seeds for subsequent processes. In order to demonstrate the flexibility of the method, its use to selectively produce localised nanostructures through different processes is shown here. Following a top-down approach, high aspect-ratio silicon nanograss has been produced by reactive ion etching and masking by the NPs. In a bottom-up approach, 280 nm copper clusters have been selectively grown in arrays. This method can be easily extrapolated to other metals and it provides a quick way to selectively generate hierarchical nanostructures in large planar areas that can be used for different applications, such as the fabrication of nanostructured sensor arrays.

Laser-driven coating of vertically aligned carbon nanotubes with manganese oxide from metal organic precursors for energy storage.

Carbon nanotubes-transition metal oxide systems are intensively studied due to their excellent properties for electrochemical applications. In this work, an innovative procedure is developed for the synthesis of vertically aligned multi-walled carbon nanotubes (VACNTs) coated with transition metal oxide nanostructures. VACNTs are grown by plasma enhanced chemical vapor deposition and coated with a manganese-based metal organic precursor (MOP) film based on manganese acetate solution. Subsequent UV pulsed laser irradiation induces the effective heating-decomposition of the MOP leading to the crystallization of manganese oxide nanostructures on the VACNT surface. The study of the morphology, structure and composition of the synthesized materials shows the formation of randomly oriented MnO2 crystals, with few nanometers in size, and to their alignment in hundreds of nm long filament-like structures, parallel to the CNT's long axis. Electrochemical measurements reveal a significant increase of the specific capacitance of the MnO2-VACNT system (100 F g-1) as compared to the initial VACNT one (21 F g-1).