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Nanocrystalline TiO2 powders with different optical band gap have been successfully prepared using solution combustion method starting directly from titanium metal. The emphasis is placed on the role of fuel urea on the variations of optical band gap which is obtained from DRS data in the range of 190–1100 nm. The samples were characterized with XRD, FTIR, FESEM, and DRS. It is shown that the powders calcined at 800 ℃ are predominantly anatase and minor rutile according to XRD results where the crystallite size ranges from 13.2 nm to 22 nm. The size of powders can affect the photo catalytic activity of TiO2 where the surface/ volume ratio determines the available sites for electrons to migrate. The micronized aggregated powders composed of sub-particles in the order of less than 100 nm have no preferred morphology based-on FESEM images. FTIR analysis satisfactorily matched with the standard data. The results of diffuse reflectance spectroscopy (DRS) accompanied with mathematical calculations extracted the values of optical direct band gap of TiO2 powders in the range of 3.53 to 3.6 eV which is in the border of UV and Vis part of electromagnetic radiation. Overall, optical band gap and crystallite size can be controlled by fuel in combustion method.

Abstract A novel polymethyl methacrylate/boehmite nanocomposite with remarkably enhanced adsorption performance of Cu(II) was synthesized from $${\text{Al}}({\text{NO}}_{3} )_{3} \cdot 9{\text{H}}_{2} {\text{O}}$$Al(NO3)3·9H2O using a facile sol–gel method. The effects of boehmite content, contact time and morphology of hybrid (pH of synthesis) as the main parameters on removal efficiency and removal capability of hybrid on copper ions have been explored. Composites contained between 0.7 and 5wt% boehmite content and those with dissimilar morphology prepared with different pH values showed different adsorption behavior. Batch adsorption experiments show that the adsorption performance of the hybrids was enhanced with increased boehmite and contact time. The highest removal efficiency and adsorption capability were achieved when the hybrid was prepared at pH 8 with associated increased catalytic activity. Graphic abstract

In this study, porous network-like α-Fe2O3 and α/γ-Fe2O3 nanoparticles (NPs) were synthesized by auto-combustion method and their photocatalytic performance was evaluated using methylene blue (MB) as a dye model. Calcination of the synthesized nanoparticles resulted in α/γ-Fe2O3 heterophase magnetite material at 450°С and pure α-Fe2O3 at 700 and 800°С. The magnetic property of α/γ-Fe2O3 makes the photocatalyst to be easily collected from the photocatalytic system and increases its potential in industrial applications. The α/γ-Fe2O3 heterophase material showed a photocatalytic performance almost similar to that of the α-Fe2O3 NPs calcined at 800°С, but higher than that of the α-Fe2O3 NPs calcined at 700°С. The cliff-like band structure between α-Fe2O3 and γ-Fe2O3 reduced recombination of photoelectrons and photoholes, thereby improving photocatalytic performance of the α/γ-Fe2O3 heterophase material.

Synthetic strategies to control the properties of gamma-alumina mesoporous have been discussed. In this study, the emphasis is placed upon the effect of three parameters pH of the reaction, salt precursor concentration and ageing time on the pore structure of nanoparticles synthesized by precipitation method. The gamma alumina as the only phase was recognized due to the appearance of characteristic peaks based on standard data JCPDS 29-0063 card in XRD pattern. The samples were analyzed by BET and BJH analysis in terms of specific surface area and pore structure (size distribution, morphology, and total pore volume). The results showed that all the synthesized samples are mesoporous. The sample synthesized at a precursor concentration of 0.1 M and pH 8 and the ageing time of 48 h obtained the highest specific surface area (217.02 m2 g−1) among all samples, while the sample prepared at the precursor concentration 0.2 M and pH 8 showed the highest pore volume with a value of 0.31 cm3 g−1. Among the parameters, only pH altered the pore morphologies from spherical to cylindrical while the ageing time and salt concentration did not change the pore morphology of mesoporous alumina samples. The TEM image reveals the sponge-like morphology which implies the appearance of a highly inter-connected pore system.

The pore size and type of aluminum oxy-hydroxide (boehmite) obtained using an optimized sol–gel method was investigated as a mesoporous material with the calcination temperature varied from 150 to 550 °C. Structural features were characterized by XRD, SEM, TEM, BET. Molecular interactions were identified by using PALS (positron annihilation lifetime spectroscopy) and CDBS (coincidence Doppler broadening spectroscopy). The XRD pattern showed that the sample synthesized at 250 °C has an orthorhombic phase characterizing the boehmite structure. All the samples prepared from pure aluminum metal were mesoporous according to BET results with a strong relationship between microstructure properties and temperature. The highest values of specific surface area and pore volume assigned to the sample prepared at 250 °C with 268.3 m2·g−1 and 0.313 cm3·g−1, respectively. The results of PAL-spectroscopy show that, the lifetime of positrons annihilating at pores of the boehmite at 350 °C increased as the average pore size growths because the free-volume defects in the samples increased.

A method to acquire polymethyl methacrylate/Boehmite hybrid nanoparticles with well-controlled morphology synthesized directly from their relevant precursors (methyl methacrylate and aluminum nitrate) via an aqueous one-pot process is proposed which considerably shorten the number of steps and render substantial commercial benefits. Silane coupling agent was applied to yield a better compatibility between the organic-inorganic counterparts that confirmed by fourier transform infrared spectroscopy spectra with the chemical bond of Si–O–Al as the main link between organic and inorganic moieties. Thermal stability, morphology study, and microhardness of (polymethyl methacrylate/Boehmite) nanohybrids were also evaluated using thermogravimetric analysis, field emission scanning electron microscopy, and Vickers hardness experiments. Field emission scanning electron microscopy analysis confirmed the formation of polymethyl methacrylate/Boehmite nanostructure with an excellent dispersion of inorganic particles in an organic matrix with high uniformity. The uniform particles including different morphologies (cauliflower, semispherical, and bean–like particles) obtained by adjusting pH, surfactant, and sequence of precursor addition. Under acidic pH 4 and basic pH 8, the cauliflower and semispherical particles were made while bean-like particles obtained when polymethyl methacrylate particles formed after boehmite. The presence of boehmite improved the thermal stability and microhardness of hybrid. The microhardness of hybrid increased more than 44% with increasing just 5% boehmite.

The morphology of PMMA/boehmite hybrid nanoparticles was controlled through the facile aqueous one-pot process starting directly from primary precursors. The effect of morphology control on optical properties of PMMA/boehmite nanocomposites was examined. Boehmite content varied from 0 to 5% and some physical properties such as density, band gap, visible transparency (400–800 nm) and UV absorption were studied. Transparent PMMA/boehmite hybrid nanoparticles (400–800 nm) with controlled morphologies were prepared. It was shown that the position of the absorption band in UV–Vis spectra of PMMA/boehmite nanocomposite depends on morphology. Morphology control leads to 13.7% increase of band gap without changing the composition. The band gap also increased with increasing boehmite in both morphologies. The results suggest these polymeric nanocomposites have good potential for application in the field of UV filters due to their high absorption in the range of 400–200 nm and high transparency in the visible region.

Rutile and anatase microcrystalline composites TiO 2 –(Ti 0.98 Si 0.2 )O 2 were successfully synthesized by auto-combustion method using urea, citric acid/nitric acid=0.6 and citric acid/nitric acid=1.2 as fuel. The prepared powders were characterized using optical and surface analysis methods. From the results of X-ray diffraction (XRD) patterns the rutile phase of the composite formed by one-step calcination. Micro size distribution function, surface morphology and electrical properties of powders were studied by Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Ultraviolet–visible spectroscopy (UV–vis). The particle size distributions of composites were measured by Dynamic Light Scattering (DLS). From UV–vis spectra the quantum confinement effect is observed because the optical band gap of powders has a blue shift.

The composition of 98.0(Al 1.9 Fe 0.1 O 3 )/2.0SiO 2 was synthesized by modifying auto-combustion method and the effect of calcination temperature on structure and optical properties were studied. The prepared powders were characterized by X-ray diffraction (XRD) patterns, X-ray fluorescence (XRF) spectrometry, Ultraviolet-visible (UV–vis) spectra and Fourier transform infrared (FTIR) spectroscopy. The particle size distribution and the specific surface area of nanoparticles were studied using Transmission electron microscopy (TEM) and BET analysis technique. Adopting Kramers–Kronig relation, FTIR and UV–vis spectra, the optical constants of nano-alumina, including optical band gap ( E g ), refractive index ( n ), extinction coefficients ( k ), real ( e 1 ) and imaginary parts ( e 2 ) of dielectric function were obtained. The results of optical band gap values indicate quantum confinement effect. The energy loss functions were determined to show loss of energy that transmit through a solid.

In this study, we developed the novel aqueous-based PMMA/AlOOH hybrid by a one-pot process starting from their relevant precursors in a controlled manner. Starting chemical reactions directly from precursors and the sequence of adding reactants provide the possibility towards enhancing the homogeneity of the final product. Inorganic and organic segments were made compatible by means of oleic acid as a coupling agent. Boehmite to PMMA weight ratio as the main parameter was varied from 0 to 18% and the morphology, particle size, size distribution, and topography map of hybrids was shown to be composition dependent. Final PMMA/Bo nanohybrids were characterized using FTIR to confirm the chemical interactions between inorganic and organic segments. TEM analysis showed that nanohybrid particles with irregular shapes containing inorganic particles dispersed in the organic matrix are formed with an average diameter which depends on boehmite content. The presence of phase transformation of Bo makes PMMA/Bo hybrids significantly thermally stable. According to AFM topography map analysis and relevant Gaussian fit function, the roughness of nanocomposite, the size of hybrid nanoparticles and deviation from the mean value (size) were increased as Bo increases from 0 to 18.

A relaxor electroceramic [Formula: see text]–[Formula: see text]–0.30-[Formula: see text] (PMN–PLT–BLT) with [Formula: see text] = 0.25, 0.50 and 0.75 was synthesized using the two combination methods of auto-combination and hot-pressing. Characterization of the crystal phase, microstructure, optical and dielectric properties of PMN–PLT–BLT was made primarily by X-ray diffraction and TEM and SEM methods. The pure perovskite crystals (rhombohedral and tetragonal) prepared at [Formula: see text] for 2 h calcination were revealed by using X-ray diffraction. The average optical transmittance of these electroceramics in the range between 450 nm and 900 nm is higher than 60% while in the IR region reached 100%. The PMN–PLT–BLT with [Formula: see text] = 0.75 displays the highest transparency around 70% near 1100 nm. The microstructures and dielectric measurements show that these three electroceramics have densities of about 98.8% and exhibit a normal relaxation characteristic.

In the current study, ABO3 (A = Pb, Ba, Sr and B = Ti) perovskite structures are produced by the auto-combustion route by using citric acid (CA) and nitric acid (NA) as fuel and oxidizer. The X-ray diffraction (XRD) patterns confirmed the perovskite nanostructure with cubic, tetragonal, and rhombohedral for SrTiO3, PbTiO3, and BaTiO3, respectively. Using Scherrer’s equation and XRD pattern, the average crystallite size of the samples were acquired. The effect of Ti–O bond length on the structure of the samples was evaluated. The type of structures obtained depends on Ti–O bond length which is in turn influenced by A[Formula: see text] substitutions. Microstructural studies of nanostructures calcined at 850[Formula: see text]C confirmed the formation of polyhedral particles with a narrow size distribution. The values of optical band gaps were measured and the impact of A[Formula: see text] was discussed. The optical properties such as the complex refractive index and dielectric function were calculated by IR spectroscopy and Kramers–Kronig (K–K) relations. Lead, as the element with the highest density as compared to other elements, changes the optical constants, remarkably due to altering titanium and oxygen distance in TO6 groups.

Optical properties of PMMA/boehmite nano-hybrid synthesized directly from their relevant precursors via facile aqueous one-pot process is studied. Silane coupling agent was applied to make compatible chemically the organic–inorganic counterparts. The chemical bond of SiOAl as the main link between organic and inorganic moieties was confirmed by Fourier transforms infrared (FTIR) spectra. The chemical bond of Si–O–Al as the main link between organic and inorganic moieties. Determining the refractive and absorption index, real and imaginary parts of dielectric constant, energy loss function, and their distribution for PMMA/boehmite nano-hybrid as a function of boehmite loading was assessed in the range of 12–120 THz using FTIR data and Kramers–Kronig relations. The inorganic/organic weight ratio varied from 0.7% to 5% and its impact on optical features was evaluated. It was demonstrated that the optical features of hybrids are frequency-dependent and less affected from boehmite incorporation.

TiO2-(Ti[Formula: see text]Si[Formula: see text]O2 nanopowders (TS-NPs) with average particle size around 90 nm were successfully synthesized by controlled auto-combustion method by using citric acid/nitric acid (AC:NA) and urea/metal cation (U:MC). The structure of powders was studied based on their X-ray diffraction (XRD) patterns. The XRD of TS-NPs shows that rutile and anatase are the main phases of TS-NPs for AC:NA and U:MC, respectively. Particle size and histogram of nanopowders were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS). Optical properties of TS-NPs were calculated by Fourier transform infrared spectroscopy (FTIR) and Kramers–Kroning (KK) relation. Plasma frequencies of TS-NPs obtained from energy loss functions depend on fuels as a result of changes in crystal structure, particle size distribution, and morphology.