Abstract/Summary

Herein, we report for the first time the fabrication of novel 3-D mesoporous nickel with single diamond morphology using direct templating through bicontinuous cubic phases of monoolein (Rylo) via the electrodeposition route. Mesoporous nickel was successfully electrodeposited from nickel electrolyte at room temperature through the bicontinuous cubic phases of monoolein (Rylo) at a potential of -0.95 V vs. Ag/AgCl. The structure of the fabricated nickel films was confirmed by small angle X-ray scattering (SAXS) analysis and the calculated lattice parameter of the fabricated films was found to be (175 ± 2.5 Å). Transmission electron microscopy (TEM) of the fabricated nickel films confirmed the deposition of nickel in a 3-D network of interconnected nanowires. The electrochemical surface area of the nickel films deposited in the presence of monoolein template was estimated to be ~266 fold higher than that of the nickel films deposited in the absence of the template. Furthermore, the specific surface area of the templated nickel films was calculated to be (~13 m2/g). In addition, the templated nickel films were found to exhibit high electrochemical stability. This makes these films very promising to be used as capacitors in batteries and fuel cells. These results validate the use of monoolein as a structure directing agent for fabrication of 3-D mesoporous materials via the electrodeposition route. Mesoporous platinum was electrodeposited for the first time from hexachloroplatinic acid (HCPA) solution through the bicontinuous cubic phases of monoolein (Cithrol) at potential of -0.25 V vs. Ag/AgCl. Cyclic voltammetry confirmed the presence of nanostructured platinum in the deposited films. Furthermore, a clear SAXS peak was observed. The lattice parameter for this peak was calculated to be 456 Å. However, the structure of the deposited platinum films could not be revealed from the SAXS analysis. Therefore, further investigations are required in order to reveal the structure of the fabricated platinum films. For the first time, we report the fabrication of Pt/Ni and Ni/Pt composites by electrodeposition of platinum and nickel onto 3-D Ni and Pt scaffolds, respectively. The 3-D Ni and Pt scaffolds were fabricated by direct templating through cubic phases of monoolein and phytantriol, respectively. The fabricated Pt/Ni, Ni/Pt films could be promising as electrode materials for batteries, fuel cells, sensors and other applications. Some of the physicochemical properties of monoolein products, Rylo and Cithrol were studied using different analytical techniques. Both cross polarised light microscopy (CPLM) and SAXS analysis revealed the formation of stable cubic phases of Rylo and Cithrol at room temperature under excess water. CPLM analysis demonstrated that the phase transition from cubic phase (QΙΙ) to hexagonal (HΙΙ) occurred at 65 oC for Rylo and at a lower temperature for Cithrol (52.3 oC). Consistently, SAXS patterns of Rylo and Cithrol at full hydration at different temperatures showed a phase transition from diamond cubic phase (QΙΙD) to hexagonal (HΙΙ) at 65 oC for Rylo and at 55 oC for Cithrol. The phase transition was accompanied with a decrease in the lattice parameter with both materials. SAXS analysis also revealed an increase in the lattice parameters of the cubic phases of both monoolein types (Rylo and Cithrol) by increasing the concentration of Brij-56 up to 20% (wt/wt), indicating a swelling of monoolein cubic phases. Therefore, Brij-56 is promising for tuning the structural parameters of monoolein-water system which is potentially important for many applications such as membrane protein crystallization, drug delivery and electrodeposition templating of nanostructured materials.