Papers by Keyword: Sol-Gel

Abstract: In this recent study, thin films of pure tin oxide (SnO₂) denoted by TO and tin oxide doped with nickel (Ni) and zinc (Zn) at varying concentrations of 5 wt.%, 10 wt.%, and 15 wt.% were developed and characterized on ordinary glass substrates. The deposition of the films was conducted using the sol-gel technique (Dip-coating). These films are referred to as (Ni-Zn) co-doped tin oxide (NZTO) films that can be used in diverse applications such as gas and UV sensors. The effect of Ni/Zn co-doping on the structural, morphological, optical, and electrical properties of undoped SnO₂ was investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet-visible (UV-Vis) spectroscopy. The electrical properties were further examined using the quadruple method. XRD analysis revealed that all samples were polycrystalline with a rutile-type tetragonal crystal structure, predominantly oriented along the (110) plane, but changed to (100) and (200) orientations with high doping contents. The grain size values exhibited a decreasing tendency with increasing co-doping content. The SEM images indicated that the films possessed a porous surface and were made up of well-defined and homogenously dispersed spherical and polyhedron-shaped nanoparticles, which were influenced by doping with Ni and Zn. The FTIR study showed that all the films exhibit the Sn-O-Sn, Sn-O, Sn-OH, and H-O vibration peaks. The NZTO films enhanced the crystal structure and raised the optical energy gap from 4.03 eV for TO to 4.09 eV for NZTO. The thickness also increased from d = 353.44 nm for pure TO films to d = 448.43 nm for films doped with 15% NZTO. The highest transmittance value was observed to be 93% for TO within the visible range. Hall effect measurements indicated that TO exhibited n-type conductivity and p-type conductivity when doped with 5%, 10%, or 15% NZTO. This allows photodetectors based on TO to show great sensitivity to UV light.

Abstract: Magnetite nanoparticles are synthesized in an environmentally friendly way by utilizing natural ingredients found in citrus limon juice. The acid in citrus limon juice serves as a fuel for the sol-gel process, producing magnetite nanoparticles. Annealing treatment (400°C, 500°C, and 600°C) is used to change the structural and magnetic properties of the magnetite nanoparticles. All samples magnetite phase was verified by X-Ray Diffraction (XRD) examination. Increasing the annealing temperature causes an increase in crystallite size from 10.81 to 27.30 nm. Furthermore, the results of infrared spectroscopy revealed the presence of oxide bonds (M-O) in the range 558–567 cm^-1 and 408–437 cm^-1, which are Fe-O bonds. Magnetic properties also change as a result of the annealing treatment, which is characterized by increased saturation magnetization and changes in other magnetic parameters. Furthermore, green synthesis of magnetite nanoparticles is effective against gram-negative bacteria (E. Coli) with enhanced antibacterial performance.

Abstract: ZnO is a semiconductor material that is widely used for many applications in industries such as solar cells, dye-sensitized solar cells, food packaging, photocatalytic, anti-microbial, light-emitting diode devices, and gas sensors. In this study, ZnO nanoparticles (NPs) have been successfully synthesized using two methods, namely spray pyrolysis and a consecutive method. The consecutive method is a combination of sol-gel and spray drying methods. The objective of this study is to investigate the photocatalytic performance of ZnO fabricated using those methods. Both methods used the same precursor, zinc acetate dehydrate as a source of zinc, but with different solvents and additives. Based on the X-ray diffraction pattern, the ZnO NPs synthesized using spray pyrolysis and a consecutive method exhibited similar polycrystalline hexagonal wurtzite structures. The large crystal sizes of ZnO NPs were obtained using a consecutive method, sol-gel followed by spray drying, in comparison with those from the ZnO spray pyrolysis. In contrast, the particle size of ZnO prepared by the consecutive method was in a smaller range. The SEM analysis implied that the ZnO structures had surface defects. In the UV-driven photocatalytic degradation of methylene blue, ZnO produced by the consecutive method exhibited slightly higher degradation performance than ZnO spray pyrolysis. This performance was attributed to the larger crystal size of ZnO NPs, which provided a longer carrier movement at semiconductor surfaces and reduced electron-hole recombination. Additionally, ZnO NPs produced using the consecutive method underwent agglomeration that leads to a smaller contact surface with methylene blue, obstructing the degradation process.

Abstract: Scale deposits in geothermal power plants are well-known potential sources of minerals. Extensive research in mineral recovery is crucial due to the considerable variability in scale composition and geochemistry based on location. Geothermal scales from Batangas, Philippines, were used to synthesize size-modified amorphous silica (SiO₂) via sol-gel method. Initial analyses employing x-ray fluorescence spectroscopy (XRF), total dissolved solids (TDS), electrical conductivity (EC), and pH measurements confirmed that the scale is rich in silica and salts at neutral pH. Then, the effect of varying scale concentration, precipitation pH, and aging time on the particle size distribution of recovered amorphous silica were investigated. Dynamic light scattering (DLS) for particle size analysis (PSA) revealed that the sample with 2.5% (w/v) scale precursor in NaOH and precipitated until pH 10 had the lowest average cumulant diameter (1.66 μm). Moreover, the synergy of precipitation pH and aging time was found to significantly affect the polydispersity index and cumulative diameter of precipitated SiO₂ based on 2³ factorial ANOVA at 0.05 significance level. X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) confirmed that the precipitates were amorphous SiO₂ with spherical morphology. This study proves the viability of utilizing geothermal scales from Batangas, Philippines for the synthesis of amorphous SiO₂ with controlled particle size, which is a potential filler for composite materials.

Abstract: This study examined the impact of silica-coating on the luminescence characteristics of indium phosphide (InP) nanoparticles. Silica-coated InP nanoparticles were prepared using three different techniques. The first method utilized tetraethoxysilane (TEOS) as the silica source, resulting in the encapsulation of multiple InP nanoparticles within silica spheres. This approach caused a red-shift in the luminescence peak wavelength of the InP colloidal solution post-TEOS coating, compared to the original InP colloidal solution. Conversely, the second method employed tetramethoxysilane (TMOS), resulting in the formation of irregularly shaped silica-coatings on multiple InP nanoparticles, which reduced the red-shift in the luminescence peak wavelength of the silica-coated InP colloidal solution. The third method involved pre-coating InP nanoparticles with TMOS, followed by thickening the silica shells using TEOS. This technique successfully encapsulated multiple InP nanoparticles within silica spheres, maintaining the luminescence peak wavelength of the InP colloid solution post-coating with TMOS and TEOS nearly identical to that of the original solution. This method merged the advantageous outcomes of the first two methods. Additionally, silica spheres containing InP nanoparticles synthesized using both TMOS and TEOS exhibited the highest luminescence intensity. In summary, this study introduces a novel approach in nanoparticle engineering, enhancing the functional properties of InP nanoparticles and expanding their potential applications in optoelectronic devices.

Abstract: In this study, eco-friendly and low-cost highly porous ceramic substrates were fabricated to enhance the performance of photocatalysts. ZnO as a model photocatalyst deposited as thin films by dip-coating sol-gel method on naturally extracted kaolin clay (90%) and Corn starch (10%)-made highly porous ceramic substrates prepared as pellet form and sintered at different temperatures: 1150, 1200, 1250, and 1300 °C. The effect of temperature on the prepared substrates modified their porosity and the best value obtained was 56% with a specific surface area of 38.80 m²/g for 1150 °C. Structural analysis of the X-ray diffraction spectra revealed a hexagonal wurtzite structure for ZnO and mullite/cristoballite structures for substrates. Scanning electron microscopy images confirmed the porosity and uniform formation of ZnO on the substrates. The high porosity samples resulted in a high reflectance of over 90%, and band gap energies values around 3.11 eV were verified by UV–VIS spectroscopy. The photocatalytic properties of ZnO thin films on ceramic substrates were studied by testing the degradation of Orange II dye in an aqueous medium under UV light irradiation. The highest degradation rate of 92% was obtained for ZnO thin films deposited on porous substrates treated at 1150 °C. The kinetic study indicated that the photocatalytic degradation of Orange II correlated with the pseudo-first-order kinetic model.

Abstract: Lightweight refractory materials are most used as a second layer in the lining. Many techniques can be used to their production depending on their final application. This manuscript is focused on utilization of sol-gel method as the replacement of hydraulic or ceramic bond in the manufacturing process of grog and castable preparation. The results show possible ways to produce high quality lightweight refractory grog with very high purity and also lightweight refractory castable, which performs good results in terms of bulk density, apparent porosity, cold crushing strength, cold modulus of rupture and permanent linear changes.

Abstract: This article deals with the selection of a suitable gelling agent for refractory castable with a sol-gel binder system. The goal is to find the optimal ratio between gelation time, content, and concentration of the solution. Various salts (NaCl, NH₄Cl, Ca(NO₃)₂) are investigated as gelling agents. Gelation curves are constructed from gelation time observations. For the design of the formula of refractory castable with a sol-gel bond, it is important to know the behavior of the sol after mixing with the gelling agent. This is the goal of the experiment. In the end, we will obtain initial data for further proposals for the composition of refractory castable with a sol-gel bond.

Abstract: Lanthanum strontium manganite (La_0.6Sr_0.4MnO₃) nanoparticles have been synthesized by sol-gel auto combustion method. Four sets of LSMO nanoparticles have been synthesized by varying the reaction pH from 10 to 13. LSMO nanoparticles were further functionalized with Polyvinylpyrrolidone (PVP). Structural properties of LSMO nanoparticles were determined by powder X-ray diffraction. Rietveld refinement of diffractograms revealed that irrespective of synthesis conditions, LSMO nanoparticles were synthesized with rhombohedral and orthorhombic crystal phases. Magnetic properties (saturation magnetization, domain magnetization and Curie temperature) of LSMO nanoparticles have been determined by vibration sample magnetometer. Synthesized LSMO nanoparticles are soft ferromagnetic and possesses Curie temperature in between 360 – 370 K. Their saturation magnetization increases with increases in reaction pH, which is in good agreement with the corresponding increase in their rhombohedral phase fraction. PVP coated LSMO nanoparticles when exposed to AC magnetic field produces magnetic hyperthermia temperature (45 °C) within 10 minutes of exposure. Hyperthermia efficiency of LSMO nanoparticles measured in terms of specific loss power (SLP) increases with magnetic field frequency and field strength and it decreases with nanoparticle concentration. LSMO nanoparticles synthesized at pH 10, 11 and 12 are suitable for the magnetic hyperthermia therapy of cancer while the one synthesized at pH 13 is not suitable for magnetic hyperthermia as it could not produce the requisite temperature of 45 °C needed to induce cell apoptosis in in-vivo experiments. Highest hyperthermia efficiency (15.69 W/g) was observed for PVP coated LSMO nanoparticles (concentration: 12.5 mg/mL) synthesized at pH 10 when exposed to an AC magnetic field of strength 10 mT and field frequency of 935.6 KHz.

Abstract: The aim of this study was to compare the synthesis process of magnetic silica nanoparticles (Fe-SNP) through the analysis of X-ray Diffraction (XRD) results. Fe₃O₄ magnetic nanopowders was synthesized by ultrasonic assisted co-precipitation and Fe-SNP was synthesized by direct mixing method of sodium silicate (Na₂SiO₃) and magnetite (Fe₃O₄) and the sol-gel method. Silica sludge was used as a silica source from Indonesia geothermal power plant waste. The synthesized of Fe-SNP is the functionalization of Fe₃O₄ with silica. Variations concentration of Na₂SiO₃ is used for the direct mixing method and variations of Fe₃O₄ form is used for the sol-gel method. Particles formed and particle size were characterized by XRD. The XRD results showed that there is no SiO₂ phase in the sample synthesized by direct mixing method while two phases of SiO₂ and Fe₃O₄ were found in the sample synthesized by sol-gel method. The size of the Fe₃O₄ nanoparticles calculated with Scherer’s formula and it obtained 19.9 nm, while the Fe₃O₄ nanoparticles with the addition of 20 mL and 6 mL Na₂SiO₃ concentrations were 6,53 nm and 10,23 nm. For the sol-gel method the size of Fe₃O₄ nanoparticles obtained was 11,03 using Fe₃O₄ powders and 9,86 using Fe₃O₄ solutions.