Juha-Pekka Nikkanen

Porphyrin-fullerene dyad with a long linker: formation of charge transfer conformer in Langmuir-Blodgett film

Abstract A porphyrin–fullerene covalently linked dyad is studied in solutions and Langmuir–Blodgett (LB) films. The dyad is characterized by a relatively long linker. In benzonitrile, it performs a relatively slow photo-induced electron transfer (ET), k ET ≈5×10 8 s −1 . Being incorporated in an LB film the dyad forms a compact conformer, which takes the smallest surface area. For this conformer the donor–acceptor separation is much shorter as compared with that in liquid phases and the molecule perform a fast photo-induced ET, k ET ≈8×10 9 s −1 . The LB films were studied using time-resolved measurements of fluorescence, absorption, and Maxwell displacement charge.

Iron Oxide Doped Alumina-Zirconia Nanoparticle Synthesis by Liquid Flame Spray from Metal Organic Precursors

The liquid flame spray (LFS) method was used to make iron oxide doped alumina-zirconia nanoparticles. Nanoparticles were generated using a turbulent, high-temperature (𝑇max∼3000 K) H2-O2 flame. The precursors were aluminium-isopropoxide, zirconium-𝑛-propoxide, and ferrocene in xylene solution. The solution was atomized into micron-sized droplets by high velocity H2 flow and introduced into the flame where nanoparticles were formed. The particle morphology, size, phase, and chemical composition were determined by TEM, XRD, XPS, and N2-adsorption measurements. The collected particulate material consists of micron-sized aggregates with nanosized primary particles. In both doped and undoped samples, tetragonal phase of zirconia was detected in room temperature while alumina was found to be noncrystalline. In the doped powder, Fe was oxidized to Fe2O3. The primary particle size of collected sample was approximately from 6 nm to 40 nm. Doping was observed to increase the specific surface area of the powder from 39 m2/g to 47 m2/g.

Influence of long-term aqueous exposure on surface properties of plasma-sprayed oxides Cr2O3 and Cr2O3–25 wt% TiO2

The influence of water exposure on the surface properties of plasma-sprayed Cr(2)O(3) and Cr(2)O(3)-25 wt% TiO(2) was studied. It was shown that both plasma-sprayed materials contained Cr(VI) hydrous oxide phases, which dissolved rapidly at the beginning of water exposure. The dissolution continued slowly during the whole water exposure time. The Cr(VI) dissolution was accompanied by a rapid increase in surface IEP value. Both Cr(2)O(3) and Cr(2)O(3)-25 wt% TiO(2) showed similar dissolution, zeta potential, and surface oxidation states. Thus the addition of TiO(2) did not influence the surface properties of the plasma-sprayed Cr(2)O(3).

Dissolution-Induced Nanowire Synthesis on Hot-Dip Galvanized Surface in Supercritical Carbon Dioxide

In this study, we demonstrate a rapid treatment method for producing a needle-like nanowire structure on a hot-dip galvanized sheet at a temperature of 50 °C. The processing method involved only supercritical carbon dioxide and water to induce a reaction on the zinc surface, which resulted in growth of zinc hydroxycarbonate nanowires into flower-like shapes. This artificial patina nanostructure predicts high surface area and offers interesting opportunities for its use in industrial high-end applications. The nanowires can significantly improve paint adhesion and promote electrochemical stability for organic coatings, or be converted to ZnO nanostructures by calcining to be used in various semiconductor applications.

Synthesis of ZnO nanowires with supercritical carbon dioxide and post heat treatment

Zinc oxide (ZnO) nanowires are used in applications such as gas sensors and solar cells. This work presents a novel synthesis route for ZnO nanowires using supercritical carbon dioxide (scCO2) and post heat treatment. The method used scCO2 and a precursor solution as reactants to form nanowires on a galvanized surface. After the scCO2 treatment, the substrate was heat-treated. The surfaces were characterized with SEM, TEM, EDS, FTIR, XRD and optical spectroscopy. The FTIR results showed that the surface structure had changed from zinc hydroxycarbonate to ZnO during the heat treatment. The nanowires were slightly bent due to the heat treatment according to the SEM images. The presence of ZnO was further confirmed with XRD. The bandgap of the structure was determined by reflectance measurements and showed a value of 3.23 eV. The synthesis method presented in this study offers a unique approach into the formation of ZnO nanowires in a facile, rapid and environmentally friendly process.

Tailoring of Versatile Surface Morphologies on Hot Dip Galvanized Steel in Wet CO2: Aspects on Formation, Barrier Properties, and Utilization as a Substrate for Coatings

Zinc carbonate and a mixed-phase zinc carbonate were precipitated selectively on hot dip galvanized steel in the presence of CO2 and water. The zinc carbonate was precipitated as a uniform layer with cubic superficial appearance, while the mixed-phase zinc carbonate was precipitated as nanowires. The distinct structures could be formed separately or as a dual structure with nanowires on the outermost surface. The barrier properties were improved by the both patina forms; a significant increase in surface hydrophobicity was obtained. The dual patina structure was successfully coated with an organic coating, and the intact wet CO2-induced patina with both structures was confirmed within the coating. The formed carbonates can be further converted to zinc oxide by calcination, preserving the delicate structures, which opens a wide range of potential applications for the nanostructured ZnO in a variety of future electronic and optoelectronic devices.