Marauo Davis

Thermoelectric properties of porous multi-walled carbon nanotube/polyaniline core/shell nanocomposites

Porous polyaniline (PANI)-coated multi-walled carbon nanotube (MWNT) core/shell nanohybrids were fabricated through in situ polymerization and subsequently assembled into macroscopic composites. N(2) adsorption/desorption analysis indicated that the volume of nanopores increased significantly, which could make a significant contribution to phonon scattering. Thermal annealing was also carried out to improve the Seebeck coefficient of the as-produced nanocomposites. The optimal sample showed electrical conductivity of 14.1 S cm(-1), a Seebeck coefficient of 79.8 μV K(-1) and thermal conductivity of 0.27 W mK(-1), resulting in a highest figure of merit (ZT) of 0.01 at a very low loading of MWNTs (<1 wt%). These results will provide a potential direction to enhance thermoelectric performance of organic materials and also facilitate the application of organic materials in thermal energy harvesting or cooling.

Synthesis and photoluminescence properties of hierarchical architectures of YBO3:Eu3+

We present a general hydrothermal method without any organic solvent or surfactant for the synthesis of YBO3:Eu3+ nano- and micro-structures. The samples were of excellent quality with uniform, well dispersed, self-assembled and self-purified YBO3:Eu3+. Single crystal nanoflakes gathered together to evolve into a hierarchical architecture with eight different types of three dimensional morphologies. Strong photoluminescence spectra were obtained at 592, 611 and 627 nm at excitations wavelengths 254 and 363 nm. The emission spectra are associated with the transitions from the excited 5D0 level to the 7FJ (J = 1, 2, 3, 4) levels of Eu3+ activators. YBO3:Eu3+ prepared using ethanol solvent exhibited the highest chromaticity values yet reported.

Tailoring cobalt doped zinc oxide nanocrystals with high capacitance activity: factors affecting structure and surface morphology

Highly crystalline zinc cobaltite (ZnCo2O4) nanocrystals were successfully synthesized through an epoxide driven, sol–gel method using Zn(NO3)·6H2O and CoCl2·6H2O as precursors. The crystal phase, morphology, specific surface areas, porosity, and capacitance activity of the prepared materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), gas sorption techniques, and cyclic voltammetry, respectively. Results reveal that the synthesized nanocrystals are ∼4 nm in diameter. Electron microscopy studies illustrate significant changes brought on by varying the solvent and epoxide. Gas sorption analyses detail high specific surface areas (>200 m2 g−1) and porosities of the as prepared and annealed samples. Cyclic voltammetry experiments show that these zinc cobaltite nanocrystals have exceptional capacitance (∼700 Fg−1) and excellent cycle durability making them an excellent electrode material for supercapacitors.

Aerogel nanocomposites of ZnO–SnO2 as efficient photocatalysts for the degradation of rhodamine B

For the first time, aerogel nanocomposites containing ZnO and SnO2 were successfully prepared through a facile, sol–gel method without the use of a template or supporting matrix. These nanoparticles exhibit high potential for application as a photocatalyst for wastewater remediation.

Formation of three-dimensional ordered hierarchically porous metal oxides via a hybridized epoxide assisted/colloidal crystal templating approach.

Three-dimensionally ordered hierarchically porous alumina, iron(III) oxide, yttria, and nickel oxide have been prepared through the hybridization of colloidal crystal-templating and a modified sol-gel method. Simply, highly ordered arrays of poly(methyl methacrylate) (PMMA) were infiltrated with a precursor solution of metal salt and epoxide. Calcination after solidification of the material removed the polymer template while forming the inverse replicas, simultaneously. These hierarchical structures possessing macropore windows and mesopore walls were characterized by powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and N2 adsorption/desorption techniques to probe the structural integrity. It was revealed by PXRD that the prepared 3D frameworks were single-phase polycrystalline structures with grain sizes between 5 and 27 nm. The thermal stability as studied by TGA illustrates expected weight losses and full decomposition of the PMMA template. SEM reveals the bimodal, hierarchical macroporous frameworks with well-defined macropore windows and mesoporous walls. Gas sorption measurements of the ordered materials display surface areas as high as 93 m(2) g(-1), and average mesopore diameter up to 33 nm. Due to the versatility of this method, we expect these materials will be ideal candidates for applications in catalysis, adsorption, and separations. Furthermore, the implementation of this technology for production of three-dimensionally ordered macroporous materials can improve the cost and efficiency of metal oxide frameworks (MOFs) due to its high versatility and amenability to numerous systems.

Enhanced electrical conductivity in mesoporous 3D indium-tin oxide materials

Free-standing, three-dimensional (3D) indium-tin oxide monoliths with an interconnected pore structure have been prepared using a non-alkoxide preparative method. This approach aids in the formation of stable frameworks with a regular pore structure and considerable electrical conductivity.

Rapid preparation of high surface area iron oxide and alumina nanoclusters through a soft templating approach of sol–gel precursors

A facile, one-pot and organic-solvent free strategy for the synthesis of Fe2O3/Fe3O4 and Al2O3 nanoparticles has been explored. Our synthesis combines the simple preparation of small particles from an epoxide assisted, sol–gel method with the rapid through-put of soft-template processing to yield highly porous metal oxides. The role of the supporting dextran template is investigated and is found to be crucial in tuning surface area and morphological shape. In all, we show this process to be a simple, low-cost approach that could be amended to other metal systems. The resulting porous Fe and Al materials was investigated using gas adsorption/desorption analysis, scanning electron microscopy and transmission electron microscopy. The annealed materials were analyzed using powder X-ray diffraction.