Papers by Keyword: Sol-Gel Synthesis

Abstract: Yttrium-doped ZnO aerogel nanostructures with low Y concentrations (0.5 and 1 at.%) were synthesized through a modified sol–gel process coupled with supercritical isopropanol drying, yielding highly porous and crystalline materials. Structural and optical characteristics were investigated using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Utraviolet–Visible (UV–Vis) spectroscopy, and photoluminescence (PL) spectroscopy. XRD results confirmed the formation of single-phase polycrystalline ZnO with a hexagonal wurtzite structure for all samples, along with lattice perturbations consistent with the substitution of Zn²⁺ by Y³⁺ ions. FTIR spectra further supported successful ZnO network formation, revealing a systematic shift of the Zn–O stretching band toward lower wavenumbers upon Y incorporation. UV–Vis measurements showed that yttrium doping enhances optical absorbance and induces a slight redshift of the absorption edge, indicating a modest narrowing of the band gap. PL analysis demonstrated a remarkable enhancement in UV and visible emission for the ZnO:Y (0.5 at.%) sample, which exhibited the highest overall PL intensity across the investigated spectral range. This enhancement is attributed to an increased radiative recombination rate of photogenerated carriers and the formation of additional defect-related states introduced by low-level Y doping. These findings highlight the strong potential of yttrium-modified ZnO aerogels for tunable optical and photonic applications.

Abstract: Conceptually, the present work leads to the synthesis of magnesium nanoparticles (MgO NPs) using pomegranate (Punica granatum L) rind extract for antibacterial fabric coating. The antibacterial performance of MgO NPs on cotton, polyester and blend wool types of fabric was evaluated towards three species of gram-positive bacteria; Staphylococcus epidermidis, Brevibacterium linens and Cutibacterium acnes. Fourier transform infrared spectroscopy (FTIR) analysis confirmed the successful of sol-gel synthesis process with the presence of flavonoid compounds in MgO NPs solution. The breaking load test was run for all fabric samples, while for tearing strength test, it was carried out only for cotton and polyester fabrics. Air permeability test device was used to determine the air permeability of all fabric samples to ensure the ventilation of the fabrics after coating process. The MgO NPs produced from sol-gel synthesis method established a good antibacterial activity against gram-positive bacteria in all types of fabric samples.

Abstract: In the research, we show that suboxidic Ti₇O₁₃ and rutile TiO₂ phases formed in addition to the general Ti₃O₅ phase when the sintering temperature was set at constant argon gas flow rate. Suboxidic Ti₇O₁₃ and rutile TiO₂ phases were removed by tuning the flow rate of argon gas at constant sintering temperature. At the 1300°C temperature, the smallest Ti₃O₅ nanocrystals with a size of ~9 nm were produced. Flat shaped particles of Ti₃O₅ crystals were observed in SEM measurements.

Abstract: Microcrystalline cellulose (MCC) has been widely used in the production of composite materials because it is inexpensive, easy to process, good mechanical properties and environmentally friendly. Despite its advantages, MCC has disadvantages such as poor thermal stability, hygroscopic and poor compatibility with hydrophobic materials. Understanding the thermal behavior of MCC is important because thermal degradation occurs at different rates and directly affects the final product. In this study, the MCC/ SiO₂ hybrid materials were prepared using in-situ sol-gel synthesis, followed by the investigation of their thermal stability and degradation kinetics using thermogravimetric analysis (TGA). Degradation kinetics were analysed using two model-free analysis (i.e. Flynn-Wall-Ozawa, FWO and modified Coats-Redfern, CRm) to evaluate the degradation behaviour (conversion degree (α) of 0.1 to 0.8) and activation energies (E_a) of MCC, MCC/ sol-gel silica (MCC/SiO₂) and modified MCC (mMCC/SiO₂) at heating rates (β) of 10, 20, 30 and 40 °C/min. Thermal stability results showed that the presence of silica on MCC had no influence on the degradation temperature of the hybrid material however, it slightly shifted the T_onset to higher values. The presence of silica also increased the final residue of the hybrid, especially in mMCC/SiO2 samples. DTG curves clearly show that all samples exhibited one step degradation process. The kinetics study assumed that all samples has single reaction mechanism as the fitted line was parallel in almost all conversion degrees (α) in both FWO and CRm methods. E_a calculated for MCC, MCC/SiO₂ and mMCC/SiO₂ are in good fit with both FWO and CRm model where the R² observed more than 0.97. E_a was increased in both methods, MCC/SiO₂ and mMCC/SiO₂ as compared to MCC, which implied that the addition of sol-gel silica to MCC could promote a stepwise degradation.

Abstract: Vanadium oxide films have been fabricated by the acetylacetonate and triethoxy vanadyl sol-gel methods on silicon substrates, as well as by magnetron sputtering on glass-ceramic substrates. Additional annealing in reducing atmosphere results in formation of vanadium dioxide or mixed phases with a VO₂ predominance. The obtained films demonstrate the metal-insulator transition and electrical switching. In the films produced from triethoxy vanadyl, the peculiarities of electrical properties are related to the size effect, heterophase character of vanadium oxide films, and different types of charge carriers in the bulk of nanocrystallites and on their surfaces. Also, the effect of doping with hydrogen by means of plasma-immersion ion implantation on the properties of vanadium dioxide is explored. It is shown that the transition parameters in VO₂ thin films depend on the hydrogen implantation dose. At doses exceeding a certain threshold value, the films are metallized, and the phase transition no longer occurs.

Abstract: Sm₂O₃/ZnO nanoparticles were prepared via microwave-assisted hydrothermal and sol-gel combustion synthesis. Characteristics of obtained samples were compared in dependence of Sm₂O₃ content and calcination temperature. Prepared nanostructures were characterized with scanning electron microscopy and X-ray diffraction. Nanoparticles prepared via microwave-assisted hydrothermal and sol-gel method have flower-like and spherical shape respectively. The photocatalytic activity of samples under solar light simulated illumination was found to be affected by content of Sm₂O₃, calcination temperature and preparation method. The first-order rate constant of MB solution degradation of samples prepared via microwave-assisted hydrothermal method approximately three times exceeds that of sol-gel samples.

Abstract: In present work, a new technique to prepare alumina nanoparticles and nanofibers using a sol-gel method was proposed. A solution combustion method was applied to form a nanostructured catalytically active layer of CuO–Co₃O₄–CeO₂ on the surface of the alumina. The uniform distribution and fine dispersion of active components provide the appropriate activity of the catalysts obtained in a model reaction of CO oxidation. The morphology of nanostructured alumina was found to affect the catalytic behavior. Carbon monoxide conversion was observed at lower temperatures when alumina nanofibers were used as a catalyst support.

Abstract: This paper aims to find various ways to maximize the potential of nickel oxide (NiO) nanostructures which is produced via simple route method. The morphology of the NiO nanostructures was modified by adding surfactants such as Tween 80, SDS and CTAB. The effect on the morphology and optical property of the type and amount of the surfactant used were determined. The synthesized nanostructures were compared in terms of its shape, uniformity and size. SEM images revealed that the morphologies were altered by simply adding and adjusting the amount of surfactant such as CTAB, Tween 80 and SDS on to the solution. Nanocubic, nanospheres and nanoblades were produced using CTAB, Tween 80 and SDS respectively. XRD confirmed the presence of oxide and hdroxides of nickel on the produced product. The effects on the morphology of the NiO upon adding surfactant could give a good impact in different applications such as electrode, catalysts and gas sensors.

Abstract: The synthesis of silica particles at the nanoscale through the sol-gel method is of great interest due to their potential use in industrial applications. The Stöber method is the most used method for the silica nanoparticles production using ammonia as a catalyst. This work studied the sol-gel synthesis of amorphous silica nanoparticles described by Stöber, in order to evaluate the influence of the variation of the process parameters (molar ratio water/TEOS = 25 and 55, reagent feed rate = 0.6 mL/min and 18 mL/min, pH = 12 and 9 and reaction time of 0, 5, 30, 60 and 120 minutes) on the particle size distribution and structural functional groups. The particle size distribution was analyzed by dynamic light scattering (DLS) and the structural functional groups was analyzed by infrared spectroscopy through Fourier transform (FTIR). The molar ratio water/TEOS influenced the functional groups presents and the time influenced the particle diameter distribution. It was not possible to identify the influence of the feed rate and pH in the results. The particle diameters found were between 200-500nm. This result may be occurred due to mass diffusion and/or nanoparticles aggregation.

Abstract: Niobium doped 8YSZ ceramics were prepared by sol-gel synthesis. The mixtures were calcined, compacted into cylindrical pellets, sintered and evaluated for phase stability, microstructure and electrical conductivity. Tetragonal, monoclinic and cubic phases were present, however the trend for phase seems to be erratic for the studied samples. The increasing Nb content appears to improve the morphology by increasing densification. It is noted that increasing Nb content also increases oxide conductivity. The best conductivity belongs to 1.0% mol Nb, with a value of 8.013 x 10^-6 (Ωcm)^-1. Increasing Nb content beyond 1.0% mol has detrimental effect on morphology and ionic conductivity.