Polychromic carbon black: Laser galvanized multicolour fluorescence display

Recovered carbon black (rCB), a very economical and abundance source of material, is transformed into dazzling multicolour fluorescence and visual display for the first time by way of a scanning focused laser treatment. This laser-initiated process is both straightforward and versatile, catering to both micro- and macro-scopic patterning with the sample in ambient or helium environment. The observed phenomenon is attributed to both chemical and structural induced colouration of rCB powder. Chemically, carbon infusion of oxidised metal occurs when photothermal reaction takes place in ambient. After laser modification with the sample in helium environment, the powder not only fluoresces due to sulphur impurities, control annealing of these powders results in formation of periodic arrangements of carbon nanoparticles. The periodicity of these arrangement falls within the range of visible wavelength, hence contributing to the visually observable rainbow coloured rCB flakes. The patterned sample is also transferrable using PDMS stamps. This in turn broadens the application of this material in flexible electronic devices/displays. Photocurrent measurements show most significant enhancement under yellow light illumination. Furthermore, in the presence of an applied potential, the fluorescence detected from the sample can easily be switched off. All in all, we present a simple process to add multiple functionalities to a material that is both inexpensive and sustainable.

     

Morphology evolution of polyaniline microstructures via reverse micelles and their hydrophobicity

Polyaniline morphology evolution in toluene has been observed for the first time. Various structures, including one-dimensional open-ended microtubes, three-dimensional solid microspheres and two-dimensional novel solid microplates were controllably synthesized in the same reaction system. The structures obtained were sensitive to oxidant concentration and molar ratio of monomer to oxidant. Solid microplates were mainly formed on the glass beaker wall and bottom, while tubes and spheres were produced in solution by employing reverse micelles as soft templates. Studies on the effect of reaction temperature, mechanical stirring and the addition of more acid were also carried out. FTIR and UV-Vis results showed that the PANI products were in the emeraldine form. The PANI film prepared from spheres exhibited hydrophobic property due to its rough surface covered with nanoscale dots and the large distribution of sphere diameters.     

Re-grown aligned carbon nanotubes with improved field emission

In this work, a simple technique to improve the field emission property of multi-walled carbon nanotubes is presented. Re-grown multi-walled carbon nanotubes are grown on the same substrates after the as-grown multi-walled carbon nanotubes are transferred to other substrates using polydimethylsiloxane as intermediation. For the duration of the synthesis of the re-grown multi-walled carbon nanotubes, similar synthesis parameters used in growing the as-grown multi-walled carbon nanotubes are utilized. As a form of possible application, field emission studies show -2.6 times improvement in field enhancement factor and more uniform emission for the re-grown multi-walled carbon nanotubes. In addition, the turn-on field is reduced from 2.85 V/microm to 1.40 V/microm. Such significant improvements are attributed to new emission sites comprising of sharp carbonaceous impurities encompassing both tip and upper portion of the multi-walled carbon nanotubes. As such, this technique presents a viable route for the production of multi-walled carbon nanotubes with better field emission quality.     

Structure-mechanical property of individual cobalt oxide nanowires

We present a comprehensive approach to address the correlation between mechanical properties of nanowires (NWs) with their characteristic size, microstructure, and chemical composition. Using this technique, the Young's modulus of Co3O4 NWs with different sizes was evaluated. Thermal annealing in inert atmosphere was found to induce chemical reduction of as-grown Co3O4 NWs into CoO NWs without modifying their geometrical shape. Both Co3O4 and CoO NWs exhibited a size-dependent variation in Young's modulus.     

The growth of pine-leaf-like hierarchical SnO2 nanostructures

Pine-leaf-like SnO₂ hierarchical nanostructures (NSs) were grown by a two-step vapour transport deposition process with a combination of vapour–solid and vapour–liquid–solid mechanisms at the primary and secondary processes, respectively. This type of hierarchical structure consisted of SnO₂ trunk with homo-branching nanowires (NWs). The branched NWs connected the trunk NWs at included angles of 56° and 90° for two different types of hierarchical NSs. Based on the thermodynamic calculation, the formation of branched NWs at those angles are all energetically favourable.     

Mechanical characterization of hotplate synthesized vanadium oxide nanobelts

Vanadium oxide nanobelts have been synthesized on Si or SiN substrates by simply heating vanadium foils on a hotplate. As-grown nanobelts were characterized as V₂O₅·nH₂O (0.3 < n < 1.7) layer structures containing water molecular intercalation. Using an electromechanical resonance method, the Young’s modulus of the nanobelts was measured in situ in a scanning electron microscope. It was found that the Young’s modulus of as-grown nanobelts varied between 5.6 and 98 GPa, with a typical Q-factor of 120. Such scattered values were attributed to the different contents of water molecules in the nanobelts. After annealing at 450 °C in vacuum, the nanobelts were converted to α-V₂O₅ phase and a polycrystalline structure was observed. The Young’s modulus of the annealed nanobelts showed more consistent values at an average of 28.9 GPa, lower than the calculated modulus of bulk α-V₂O₅ at 68 GPa.     

Micropatterning of porphyrin nanotubes thin film using focused laser writing

We report an effective process to create micropatterns on a thin film of porphyrin nanotubes PNTs on Si substrate using focused laser beam. The optical properties of the newly synthesized porphyrin nanotubes are investigated and micropatterning is demonstrated using laser fabrication, an increasingly important tool in various fields of research. We made use of this laser cutting method to create interesting and useful two-dimensional patterned structures. The shapes and sizes of the structures created can be controlled by varying the power of the laser, angle of incident of the focused laser beam, the relative speed with which the laser beam traverse through the film and the magnification of objective lens used.