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Background: Currently, solution combustion synthesis (SCS) is considered a reproducible, flexible, and low-cost synthesis method for the preparation of nanomaterials. A new trend in the SCS method is the use of less polluting fuels, such as starch. The use of starch as fuel in SCS is very interesting for green chemistry, as it is renewable and has several advantages, including its abundance, low-cost, and non-toxicity. Objective: This paper provides a comprehensive review of the SCS method using starch as fuel. The main advantages of using starch as fuel will be illustrated with a wide variety of examples, highlighting its impact on the preparation of nanomaterials for energy and environmental applications. Conclusion: In a combustion reaction using starch as fuel, several positive effects are expected, such as non-violent propagation, combustion with the production of non-toxic gases (mainly CO2 and H2O), and development of pores during the release of gases. For example, several macroporous metal oxide foams were prepared using the SCS method, through an appropriate combination of urea and starch fuels. With this approach, it is possible to control the structure, lattice defects, crystallite size, specific surface area, porosity, and other characteristics of the synthetized nanomaterial. For example, by combining starch with other fuels, it is possible to control the concentration of lattice defects in metal oxides and modify the optical properties of these materials. These properties are of fundamental importance for the performance of these materials and their subsequent application in electrodes, electrocatalysts, and photocatalysts in the areas of energy and environment.

Anthropogenic CO2 emissions are the major drivers of global warming and climate change. The adsorption of CO2 is one of the strategies to mitigate these emissions. In this sense, different materials have been used as adsorbents as is the case of zeolites. In this work,experimental infrared and X-ray analyses together with DFT (Density Functional Theory)theoretical calculations were employed to study the adsorption of CO2 on mordenite zeolites (Na-MOR). Ion exchange followed by chemical analysis showed that the Na+ of Na-MOR was not completely substituted under the experimental conditions employed. The XRD (X-ray Diffraction) analysis indicated that Na+ exchanged for Li+ did not affect the crystallinity of the materials. The infrared results showed that CO2 interacted linearly with the sodium and lithium cations present in the main channel of the mordenite framework. Sodium in dry samples favored the formation of carbonates and hydroxycarbonate species, as did the presence of low water content in the LixNa-MOR. The DFT periodical calculation of dehydrated mordenite models led to CO2 adsorption energies in the range of − 31.6 to − 34.2 kJ mol−1, with the highest adsorption energy found for sodium mordenite.The asymmetric stretching ν3 (CO2) vibration mode resulted intense and presented a shift which indicated a higher CO2 interaction of Na-MOR. The presence of some water molecules in the mordenite framework caused a decrease in the adsorption energy.

Ni/NiO composites were obtained by self-propagation synthesis (SHS) in order to investigate their structural and optical properties, evaluating the effects of ammonium hydroxide in the combustion. All the obtained solids were analyzed by X-Ray Diffraction (XRD), Ultraviolet–Visible spectroscopy (UV–Vis), Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy (RT-Raman) and Photoluminescence Spectroscopy (PL). The Ni phase content in the composite was dependent on the amount of ammonium hydroxide. Variations in the NiO cell dimensions were related to their nanostructure and to the formation of defects within the NiO lattice. Sample microstrain was associated with optical properties. The band gap values are shifted to higher wavelengths (red shift). The PL spectra show a strong dependence on the microstrain and NiO lattice defects. The PL quantum yield was measured in order to compare the amounts of defects in Ni/NiO composites.

Lithium manganese oxide, LiMn2O4, was synthesized in two temperature stages, where the first consisted by an ecofriendly solution combustion method at 300 °C. Finally, the as-burned powders were thermal treated at 500 and 700 °C. The structural and morphological changes were evaluated by the Rietveld method and density functional theory (DFT) calculations. The Rietveld refinement indicates obtaining the spinel cubic phase LiMn2O4 and a small amount of Mn2O3. The analyses by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) show a porous microstructure composed of nano-sized crystallites for the sample treated at 500 °C. In cyclic voltammetry, it was possible to observe that the reduction-oxidation reaction is reversible due to the shape of voltammograms and the anodic and cathodic peaks of Mn ions. The theoretical calculations considered the experimental crystallographic parameters. The unit cell volume change was evaluated according to distinct amounts of lithium ions in the structure. The removal of the Li+ cations from the oxides promotes a volume contraction. Therefore, it was possible to evaluate the participation of the Mn3+ ions in the frontier region between the valence and conduction bands. The density of states (DOS) calculation shows a predominant contribution of the O 2p and Mn 3d orbitals in the frontier orbitals.

SiO2/TiO2/Sb2O5 ternary oxide was prepared by the sol–gel method in two different proportions, and were characterized by X-ray fluorescence (XRF), analysis of the specific surface area by BET and the average pore size and pore volume by BJH method, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and electron dispersive spectroscopy (EDS) analyses, powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and other spectroscopic technics (FT-Raman, FT-IR, UV–Vis–NIR and DRS). The ternary oxides showed high surface area 758 and 529 m2 g−1 for SiTiSb-A and SiTiSb-B, respectively. The binding energy values for the Sb 3d and Ti 2p levels show the insertion of Sb and Ti atoms in the silica matrix, confirming the high dispersion of the metals presented in SEM, both in the bulk and on the surface. The thermogravimetric analysis (TGA) showed weight loss of 23% for both ternary oxides. The crystallographic data showed an increase of the crystalline order with the increase of the temperature of the thermal treatment. The anatase phase as well as a small content of the rutile phase of TiO2 were identified by FT-Raman. The Raman spectrum corroborated with the DTA and XRD of the SiTiSb-B which showed a slight decrease in the degree of crystallinity. Optical band gap values are dependent on the content of oxides. The pyridine adsorption studies showed the presence of Lewis and Bronsted acid sites on the SiTiSb ternary oxide surface, where the SiTiSb-B presented more acid sites on the surface.

A new silicon-aluminum-zirconium ternary oxide (SiO2/Al2O3/ZrO2) was prepared by the sol-gel method followed by one-step washing with absolute ethanol or two-step washing with absolute ethanol followed by ultra-pure water. Both ternary oxides presented high surface area (over 340 m2 g-1). The binding energy values for Zr3d and Al2p levels showed the insertion of Zr and Al atoms in silica matrix, confirming the dispersion surface of these elements as shown by scanning electron microscope (SEM) and energy dispersive X-ray fluorescence spectroscopy (EDXRF) data. A weight loss around 40 wt.% was found for both samples submitted to thermogravimetric analysis (TGA). Crystallographic data showed the presence of monoclinic and tetragonal ZrO2 phases in different proportions according to the calcination temperature. Regarding the acid-base properties, temperature-programmed desorption of CO2 (CO2-TPD) profiles suggested that washing with water reduced the overall basicity of the samples and removed the strongest basic sites. However, according to temperature-programmed desorption of NH3 (NH3-TPD) profiles, washing significantly increased the amount of weak acid sites, in agreement with pyridine adsorption data. Brønsted acid sites (BAS) are ever dominant but washing with ethanol followed by water reduced the number of Lewis acid sites (LAS).

Density functional theory (DFT) (B3LYP/6-311++G(d,p)) calculations of the interacting strength 1,2-dithiolene anionic ligands with the [M(OH2)4]2+ and [M(OH2)2]2+ complexes (M = Ni and Zn) were performed. Three series of ligands were studied: compounds with an aromatic ring, with an ethylene moiety and with a heterocyclic ring. The ligands have substituents electron donors and acceptors by induction and resonance. Two substitution reactions were studied: the first is the substitution of two water molecules from the [M(OH2)6]2+ by a dithiolene anionic ligand (L2-) and the second is the substitution of two water molecules from the [M(OH2)4L] by another dithiolene anionic ligand. Geometric, electronic and energetic properties of the substituted aquacations are correlated with the metal-ligand affinity. All the substitution processes for both metal cations are spontaneous and are modulated by the electronic effect of each substituent of the ligand. Geometric parameters and chelation angle are correlated with the interaction strength. The energy decomposition analysis (EDA) results show that the electrostatic component is the main stabilizing term for the monosubstituted complexes, while for the disubstituted complexes the covalent term is the main stabilizing component. The polarization term is the main one to describe the covalent character. Natural bond orbital (NBO) shows the acid-base interaction nature of the metal-ligand bond.

Lithium cobalt oxide, LiCoO2, widely used as cathode in lithium ion batteries was synthesized and their structural and electronic properties investigated. The crystalline powders were prepared by the sol-gel method with four complexing agents: citric acid, glycine, starch and gelatin. These syntheses were compared with the blank test (without complexing agent). The X-ray diffraction and vibrational spectroscopy allowed the identification of the rhombohedral phase LiCoO2 (R3m) as the only or principal crystalline component in all samples. A small fraction of a second phase of cubic spinel Co3O4 was observed in the samples of starch, gelatin and the blank test. The Rietveld refinements showed small structural variations, indicating reduced influence of the complexing agents on the synthesis. The theoretical HOMO-LUMO (highest occupied molecular orbital-lowest unoccupied molecular orbital) gap values are in agreement to those estimated by diffuse reflectance spectroscopy (DRS). The scanning electron microscopy (SEM) showed morphological pattern regardless of the complexing agent used, showing an alternative method.

Nanocrystalline calcium and strontium singly doped ceria and co-doped ceria materials for solid electrolytes were prepared via a hydrothermal route. The effect of the hydrothermal treatment time on the solid solution composition was evaluated. Sr doped ceria was the most difficult to form, due to the Sr 2+ large ionic radius. The small crystal size (12–16 nm) of powders allowed sintering into dense ceramic pellets at 1350 °C for 5 h. Raman spectroscopy evidenced a great lattice distortion for Sr doped and co-doped ceria materials, explaining the deterioration of the electrical properties for these ceramics. Besides that, a second phase was detected for Sr doped ceria pellet by using X-ray powder diffraction and Rietveld refinement of XRD data. Impedance measurements showed that Ca-doped ceria behaves as the best ionic conductor ( σ g 390 °C = 1.0 × 10 −3 S cm − 1 ) since the nominal composition was achieved; on the other hand, Sr doped ceria performed as resistive materials since Sr incorporation into ceria lattice was critical. These results enhance the close interlace between electrical performance and chemical composition of alkaline earth doped ceria.

This paper describes a simple procedure to synthesize materials with NASICON-like structures, using starch as a mild combustion fuel. The results of ICP-MS, x-ray and Raman spectroscopy present that the samples can be classified as a solid solution and isostructural to Li2Co2(MoO4)3. The analysis by x-ray diffraction shows that the increase on starch amount promotes crystallinity, leading to diffraction peaks more intense and better defined. Moreover, we can infer that the amount of starch increases substantially the material capacity (5 mAhg-1 to 52 mAhg-1), as well leads to a better definition of the redox peaks