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Preparation of MgO and Mg0.95Zn0.05O nanomaterials using self-propagating combustion method are done to investigate the effect of doping on the band gap energy. The synthesis condition has been optimized to obtain pure MgO and Mg0.95Zn0.05O materials which confirmed by XRD. FESEM results shows agglomeration of crystallite with average crystallite size of samples between 30 nm to 125 nm. The band gap obtained from the measurement of UV-Vis NIR spectrophotometer for MgO nanostructure is 6.36 eV which is lower than bulk MgO of 7.8 eV. The presence of Zn in Mg0.95Zn0.05O sample causes the narrowing of band gap to 5.33 eV.

Preparation of MgO and Mg0.9Li0.2O materials using self-propagating combustion method are done to investigate the effect of substitution doping on the band gap energy. The synthesis condition has been optimized to obtain pure and single phase of MgO and Mg0.9Li0.2O materials and was confirmed by X-Ray Diffraction (XRD). The morphology obtained from field emission scanning electron microscopy (FESEM) is spherical and rounded polyhedral shape with agglomeration of crystallites for MgO and Mg0.9Li0.2O materials respectively. The crystallite size of MgO and Mg0.9 Li0.2O samples is between 50 nm to 120 nm and 200 nm to 1500 nm respectively. The band gap was determined by UV-Vis NIR spectrophotometer and it was found that the band gap obtained for MgO nanostructure is 6.10 eV which is lower than bulk MgO of 7.8 eV. The presence of Li in the MgO had caused changes in morphology, crystallite size and band gap narrowing to 3.83 eV.

Band gaps are important characteristics of materials. Most metal oxide nanomaterials, such as ZnO, exhibit band gap widening, however, SnO2 nanomaterials conversely exhibit band gap narrowing. It is important to understand this phenomenon at a more fundamental level. In this work, the reasons behind the band gap narrowing is probed in terms of crystal structure, electronic charge configuration and quantum mechanical effects of energy discretization in the materials. The samples were calcined at 700 °C for 1 h, 2 h, 5 h, 10 h, 24 h and 48 h for the investigation of the different nanostructured SnO2. The crystallite size of SnO2 nanostructures were found to increase with calcination time. Crystal structural parameters were extracted via the Rietveld method and it was found that changes of both the a and c cell parameters were greatest in the crystallite size range of the nano region (100 nm and below). It was observed that there is a correlation between the crystal dimensions with the band gap and conductivities of the nanomaterials. It is proposed that the band gap narrowing is due to the decrease in the hybridization of the SnO2 nanomaterial energy levels resulting in more discrete energy levels and the narrowing of the band gap. This quantum effect may not be seen in other metal oxides with different electronic configurations and crystal structure.

Doping of the materials with other metals or transition metals will modify the properties of the nanomaterials. In this work, MgO and Cu doped MgO which are Mg0.95Cu0.05O and Mg0.90Cu0.10O nanomaterials are synthesized using a self-propagating combustion method. The samples are annealed at 900 °C for 24 hours. The phase and purity of the synthesized samples are studied using X-Ray Diffraction (XRD) and the result revealed that the samples are pure and single phase. The morphology and crystallite size of the pure samples are examined using Field Emission Scanning Electron Microscope (FESEM). The result shows polyhedral morphology with agglomeration of crystallite and average crystallite size of the samples is between 40 to 210 nm. The band gap obtained for MgO nanostructures is 6.38 eV which is lower than bulk MgO of 7.8 eV. The presence of Cu causes the narrowing the band gap energy of Mg0.95Cu0.05O and Mg0.90Cu0.10O samples to 4.28 eV and 3.35 eV respectively.

Pulsed laser deposition (PLD) method has the advantages of high quality mirror finish, good densification and uniform thickness. In this work, Al2O3 thin films with different thicknesses were fabricated via the PLD method. The characteristics of the thin film samples were investigated using Grazing Incidence Diffraction (GID) technique and Field Emission Scanning Electron Microscope (FESEM). For the band gap studies, measurements were done using a UV-Vis NIR spectrophotometer. The deposition was done in the presence of oxygen gas with partial pressure of 2.66 Pa. FESEM images showed high quality, smooth and dense films obtained using the PLD method. The Al2O3 thin films have thicknesses of between 71.2 nm to 176 nm. The band gap energies obtained were in the range of 6.29 eV to 6.49 eV. It was observed that the band gap of the thin films increases as the thickness decreases due to the defects in the films.

Biodiesel is known as the best candidate for the replacement of nonrenewable biodiesel. Currently, it has been produced from transesterification and esterification of triglycerides and fatty acids, respectively. However, the production of biodiesel from waste oils surrounded by numbers of obstacle such as saponification problem, complex purification process, high-cost production, and dual-step processes has made them the least choice feedstock. Recently, an advanced scientific finding in the catalysis technology has been reported for the reduction of free fatty acid (FFA) from waste oils. Photocatalysis is a light-induced catalytic process that involves oxidization and/or reduction of organic molecules via redox reactions activated through the electron-hole pair generated on the surface of semiconductors upon light irradiation. The esterification of FFA with ethanol is carried out according to the Langmuir Hinshelwood reaction path: when a photocatalyst is irradiated by ultraviolet light, the photogenerated electrons (e−) in the valence band are excited and transferred to the conduction band, and the same number of holes (h+) will be produced. The methanol adsorbed on the catalyst surface reacts with photogenerated hole (h+) to generate H+ and radical methanol. At the same time, fatty acid molecules adsorbed on the surface of the catalyst is reduced to form free radical by accepting the photogenerated electron (e−) on the surface. Then, the reaction between radicals and protons will react to form methyl ester and water. In this chapter, we successfully studied, analyzed, and discussed the classical technique of biodiesel production, and fundamental, theories, concept, and potential of advanced photocatalysis technology in the biodiesel production.

From experimental investigations of the bandgaps of magnesium oxide (MgO) nanostructures, the results show that band-gap narrowing occurred as the physical dimension of the MgO crystallites decrease. This is in contrast to other metal oxides such as ZnO. To obtain insights on this observed phenomenon, the first-principle studies using density functional theory were carried out. The strategy used here is different from the normal theoretical studies, such that information of the structural characterization obtained from experimental X-ray diffraction (XRD) data via the Rietveld method was used in the calculations. This is important, because nanostructures do not possess the same crystal parameters as the bulk and accurate real structural parameters should be used in the calculations. Based on these values, the crystal structures were simulated and the electronic band structures were calculated within the density functional theory (DFT). Results from the density of state (DOS) studies shows that the band-gap narrowing is due to the shifting of the valence and conduction bands. From our theoretical results, we can conclude that the narrowing of the bandgaps of MgO nanostructures is a consequence of the increase of their lattice parameters. The calculated results exhibit this trend and are in good agreement with the experimental results.

The band gap energies of MgO nanostructured can be tuned to a suitable value needed for various applications by substitution with dopant element. The study on doped compounds is to investigate band gap changes in the new materials. In this work, MgO and its doped materials Mg1-xCuxO (x = 0.02, 0.04, 0.06) were synthesized using a combustion method. The phase and purity of materials were studied using X-Ray diffraction (XRD). The morphology and crystallites size of the materials were examined by a Field Emission Scanning Electron Microscope (FESEM). It was found that the synthesis route using triethanolamine for the combustion synthesis is suitable in obtaining pure and single phase MgO and Mg1-xCuxO nanostructured. The presence of doped element, Cu in the MgO had caused changes in morphologies and crystallite size of the materials. The band gap energy of the materials was measured using a UV-Vis NIR spectrophotometer. The absorption edges of Mg1-xCuxO were observed to shift to the right with respect to those of MgO as the Cu content increases, implying that band gap narrowing occurred in the materials.

Quantum dots are interesting nanostructures with have novel physical and chemical characteristics. It is not an easy task to obtain quantum dots because materials tend to agglomerate. In this work, SnO2 quantum dots have been successfully synthesized via a simple and low cost method which is the sol-gel method. Thermal analysis of the precursors were carried out using a Simultaneous Thermogravimetric Analyzer (STA). The annealed samples were characterized using X-Ray Diffraction (XRD) for phase studies. Finally, the crystallite size and morphology of tin oxide quantum dots were determined using Field Emission Scanning Electron Microscopy (FESEM).

Recently, several synthesis methods have been reported for producing magnesium oxide (MgO) nanostructures such as sol-gel, combustion, thermal evaporation, chemical precipitation, etc. This work describes a simple method to synthesize MgO nanostructures via a conventional solid-state reaction method using magnesium acetate tetrahydrate as a starting material. Magnesium acetate tetrahydrate was directly annealed at a temperature of 600 °C and 800 °C for 24 h. The X-Ray Diffraction (XRD) revealed that the annealed samples were pure while Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) showed different morphologies of MgO. From the results, it is found that TEM may reveal information that cannot be observed in the SEM micrographs.

Magnesium oxide (MgO) is a metal oxide which has many applications in industry and can be synthesized by many different synthesis methods. In this study, MgO was synthesized by using two different methods which were sol-gel and solid-state reaction methods. Both samples were annealed at 800 oC for 24 hours and characterized by using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The band gap energies for both samples were determined by using UV-Vis NIR Spectroscopy. The band gap values of the samples are evaluated from the data. It was found that the band gap energies of the MgO using different synthesis route were not the same.

Carbon additives are very important components of cathodes in Li-ion batteries. This is because carbon is an electronic conductor whereas cathode materials are ionic conductors. Without the presence of carbon, the electrons will not be able to flow and there will be space charge built-up in the materials. Carbon therefore facilitates the conductivity of charged species in the cathode materials and help to disperse the negative charge accumulation which may otherwise impede Li-ion diffusion within the cathodes. In this work, two types of carbon, namely, activated carbon (micron sized) and Denka Black (nano sized) were used in conjunction with the cathode materials LiCoO2and LiMn2O4. The amounts of cathode materials were kept constant while the amounts of carbon additives were varied. Galvanostatic charge-discharge was done over a voltage range of 4.2 V to 3.2 V. Results showed that Denka Black gives improved performance for both cathode material. This is believed to be due to the effect of nano sized particles of Denka Black.

In this work, the band gap energies of magnesium oxide (MgO) were investigated to see if calcination time affects the band gap energies of the MgO. MgO nanomaterials have been prepared by a sol-gel method. MgO precursors produced were calcined at a temperature of 600 °C for 24 hours and 48 hours. The structural characterization of samples is achieved using X-Ray Diffraction (XRD) and the morphology as well as particle size of MgO were examined by Field Emission Scanning Electron Microscopy (FESEM). UV-Vis NIR spectroscopy was used to determine the band gap energies of the materials. From the results, the band gap energy of the MgO with a longer heating time exhibited a higher value.

Substitution of cation in metal oxides could give different properties with potential in some applications. Li2xMg(1� x)O was prepared by substitution of magnesium with lithium in magnesium oxide to form new materials which were Li0.2Mg0.9O and Li0.4Mg0.8O. They were synthesized using a sol–gel method. The samples were characterized using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The band gap energies of the samples were obtained from measurements using a UV–vis Spectrophotometer. The crystalite size of the MgO samples was sub-micron while that of the Li substituted samples were larger. It was found that there were quite drastic differences in the band energies of MgO and Li2xMg(1 � x)O materials. & 2012 Published by Elsevier B.V.

MgO films of various thicknesses were fabricated via the pulsed laser deposition method. The MgO thin films obtained have the advantage of high quality mirror finish, good densification and of uniform thickness. The MgO thin films have thicknesses of between 43 to 103 nm. They are polycrystalline in nature with oriented growth mainly in the direction of the [200] and [220] crystal planes. It is observed that the band gap of the thin films increases as the thickness decreases due to quantum effects, however, turn-on voltage has the opposite effect. The decrease of the turn-on as well as the tunnelling voltage of the thinner films, despite their larger band gap, is a direct experimental evidence of quantum tunnelling effects in the thin films. This proves that quantum tunnelling is more prominent in low dimensional structures.

Magnesium oxide (MgO) is one of the metal oxides which has unique properties and has great potential applications in industry. In this work, MgO was synthesized by using a sol‐gel and solid state methods. The precursor of MgO was annealed at the temperature of 600 °C for 1 hour and 800 °C for 24 hours for sol‐gel method. For solid state method, magnesium acetate was annealed at the temperature of 800 °C for 24 hours. These samples were characterized by using X‐Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). TEM micrographs show the morphology of the samples of the sol‐gel method are thin film nanostructures whereas sample of the solid state method is spherical shape. The band gap energies of the samples were measured using UV‐Vis NIR Spectrophotometer. The band gap values of the samples were calculated and it was found that there is a difference of band gap energies between samples employing different synthesis route.

Lithium conducting ceramics are important for applications in thin film batteries. In this work, novel Li2xMg1-xO materials were synthesized by the sol-gel method. Optimization of the synthesis method showed that annealing at 950 oC gave pure, single phase materials of cubic crystal structure. Conductivity studies, using a.c. impedance showed that incorporating nanostructured carbon enhances the conductivities of the composite materials. The nanostructured carbon acted like a bridge connecting the voids between the crystals and improved the electronic and Li+ ionic diffusion through the materials.

ZnO and Zn0.99Cu0.01O nanostructures were prepared by a simple sol–gel method. The band gaps of the materials were systematically studied based on the dependence of the dimensions of the nanostructures as well as the presence of a dopant material, Cu. ZnO and Zn0.99Cu0.01O nanostructures were found to exhibit band gap widening whilst substitution of Cu in the lattice of ZnO caused its band gap to narrow with respect to the pure ZnO materials. In order to understand the phenomenon of band gap change, structural, spectroscopic, particle size and morphological studies were done. The band gap change occurring when the materials were in the nanostructured phase was proven to be mainly due to the downward shift of the valence band. Interestingly, when the band gaps of the pure ZnO and Cu doped ZnO were compared, the band gap changes were due to different shifts of the valence bands. Keywords: Nanomaterials, Rietveld refinement, Doped ZnO, Band gap, Energy band shift