Papers by Keyword: Titania Nanoparticles

Abstract: Weak stimulated emission cross-section of rare earth ions (REIs) as dopants inside various glass hosts are disadvantageous for practical applications and needs improvement. We determine the mechanism of Titania (TiO₂) nanoparticles (TNPs) mediated Surface Plasmon Resonance (SPR) assisted modification in the spectral properties of tellurite glass doped with Erbium (Er³⁺) ions. Transparent and thermally stable glass samples with varying TNPs contents are synthesized using melt-quenching technique. TEM images revealed the existence of TNPs with average size ranged from 16 to 26 nm. Glass containing 0.4 mol% of TNPs displayed an enhancement in the Raman signal by a factor of 2.25, 1.83, 1.98, 1.56 and 3.58 for the bands centered at 388, 495, 673, 758, and 845 cm^-1, which is attributed to the SPR assisted effects. Absorption spectra of TNPs embedded glass (devoid of erbium ions) manifested two surface plasmon (SP) bands at 552 and 580 nm. Up-conversion (UC) PL spectra showed three prominent bands centered at 525, 545, and 660 nm due to the Er³⁺ ion transition from the excited states to the ground state. Furthermore, glass containing 0.4 mol% of TiNPs exhibited an intensity enhancement by a factor of 30, and 28.57 (green bands) and 19.60 (red band), which are ascribed to the generation of strong local electric field mediated by SPR effect of TNPs situated in the vicinity of Er³⁺ ion. The presence of TNPs surface plasmon is asserted to be responsible for the alteration of the Er³⁺ ions absorbance and modification of the UC emission intensity. A correlation between SPR and Surface Enhance Raman Scattering (SERS) is established.

Abstract: The effects of Titania nanoparticles (TiNPs) sensitization on the self-cleaning, spectral, and physical properties of erbium-doped tellurite glass were determined. Five glass samples with composition (69-x)TeO₂-20ZnO-10Na₂O-1Er₂O₃-(x)TiO₂, where x = 0.0, 0.1, 0.2, 0.3 and 0.4 mol% were synthesized using melt quenching method. XRD pattern confirmed the amorphous nature of prepared samples and TEM images manifested the growth of nearly spherical TiNPs of average size ≈14 ± 1 nm inside the glass matrix. The observed decrease in the water contact angle from 68^o to 43^o with increasing TiNPs contents was ascribed to the increase of glass surface hydrophilicity. Meanwhile, enhanced degradation rate of methylene blue (MB) with increasing TiNPs contents up to 0.2 mol% indicated an improved photocatalytic activity of the glass sample. The UV-Vis-NIR absorption spectra exhibited ten significant bands of Er³⁺ ions. Two plasmon absorption bands were evidenced at 552 and 580 nm. The green band in the photoluminescence spectra of sample containing 0.2 mol% of TiNPs showed highest enhancement factor of 30 times. It is established that the present glass composition is prospective for making self-cleaning surfaces and other display devices.

Abstract: In this work, nanomaterials were used as consolidants and protective layers for artistic stones. Synthetized nanocomposites were applied on marble and their performances as protective and water repellent coating were characterized. For the preparation of the novel nanocomposites, SiO₂ and TiO₂ nanoparticles were synthesized by laser pyrolysis and were dispersed in acrylic polymer and silicon-based resin. To evaluate the retreatability of water repellent treatments, the capability of laser to remove protective layers was explored. Laser cleaning tests with different working parameters have been carried out to optimize the effectiveness of the process. The effects of laser treatments on stone surfaces and on the applied nanocomposites were estimated by using confocal optical microscopy and Laser-Induced Fluorescence (LIF).

Abstract: Electrophoretic deposition (EPD) is one of useful methods for the preparation of the thin film with homogeneous microstructure on a conductive substrate. In the EPD method, the structure of the particle thin film could be controlled by adjusting the electrical operating conditions. Titania nanoparticle (NP) films, which are used for the electrode of dye-sensitized solar cells (DSSCs), require not only the homogeneous microstructure but also controlled pore size distribution, contributing to high-rate transport of electrons for the high conversion efficiency of DSSCs. In this study, titania NP films were prepared by EPD under DC constant-current conditions using available NPs dispersed in ethanol. The thickness as well as the weight of the titania NP film appeared to be increased almost linearly with EPD operation time, while the porosity of the film calculated from those values was not always constant but increased slightly with the operation time and asymptotically reached about 60%. We confirmed that the forces on the particles depositing onto the substrate became weaker as the EPD operation time increased, due to the electrostatic charges gradually building up on the thin NP film with particle deposition. The deposition behavior of titania NPs was drastically changed upon varying the water content in ethanol. We detected many pinholes on the surface of thin NP films when the water content in ethanol increased. The amount of particles accumulated on the substrate via EPD could be calculated based on the electrical conductivity of the suspension and the mobility of particles in the suspension, but was found to be underestimated when the water content increased.

Abstract: Titania nanoparticles were obtained by an ultrasonic assistant sol-gel method. The prepared titania nanoparticles were characterized by X-ray diffraction (XRD) and differential scanning calorimeter (DSC). The photocatalytic properties of the prepared titania were evaluated from the photodegradation of X-3B solution. The thermalanalysis results showed that the weight loss of prepared TiO₂ particles ends at about 500°C, and the appropriate condition of calcination was found to be 2 h at 500°C. The XRD results showed that anatase was the main phase of prepared TiO₂ nanoparticle, and the average crystallite size of the TiO₂ particles, calcined for 2 h at 500°C was calculated as 15.3 nm using the Scherrer equation. The results demonstrated that such nanoTiO₂ showed high photocatalytic activities for X-3B degradation, whether it is under UV irradiation or sunlight irradiation.

Abstract: Novel nanogold doped TiO₂ nanoparticles are found to be highly efficient for the photocatalytic degradation of organic pollutants. TiO₂ nanoparticles were synthesized from titanium (IV) isopropoxide through hydrothermal route. Gold nanoparticles were prepared by chemical reduction and stabilization employing D-glucosamine, and were doped in TiO₂ nanoparticles. The analysis revealed that the diameter of gold nanoparticles used for doping is around 5 nm. Undoped and gold doped samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, UV-Vis diffuse reflectance spectra (DRS) and field emission scanning electron microscopy (SEM). DRS study showed that nanogold doping in titania nanoparticles induces a shift of absorption edge to the visible range and reduces the band gap. Complementing our earlier finding that noble metal doping in titania nanoparticles enable photocatalytic activity in the visible region, it is showed that gold doping enhances photocatalytic activity of the titania nanoparticles. This was confirmed by the degradation of the dye methylene blue repeatedly using gold doped nanoparticles under direct sunlight. Further, the nanoparticles were used to study the degradation of the persistent organic pollutant, β endosulfan, and near complete degradation were observed in an hour. Regenerated nanoparticles were found effective for the degradation of the pesticide for more than three cycles.

Abstract: Recently photocatalytic materials have been used in variety of industrial applications. TiO₂ is the only suitable photocatalytic material for industrial usage due to its benefits such as non-toxicity, stability, and low cost. TiO₂ nanoparticles were successfully synthesized from titanium alkoxide precursor by sol-gel method. Effects of nitrogen doping on the microstructure and phase evolution of the TiO₂ nanoparticles were investigated. The X-ray diffraction results of doped samples confirm the presence of anatase as the only crystalline phase. The addition of nitrogen in titania matrix leads to disappearance of rutile traces. The scanning electron microscopy show that TiO₂ nanoparticle size decreases by increasing nitrogen doping. Furthermore, DSC-TG results reveal that the crystallization temperature of doped sample shifts to higher temperatures of about 100 °C.

Abstract: The objective of this work is to utilize a low-grade synthetic rutile to produce high-grade titania nanoparticles. Due to the nature of the precursor, the hydrothermal method needs modification in order to accommodate the precursors and chemical reagents. The product will be characterized with the XRD (crystallite size and crystallinity), EDXRF (chemical composition), SEM (Morphology), N₂ adsorption-desorption (Surface Area) and UV-Vis-NIR. Results revealed a crystallite size of less than 20 nm, a surface area of 186.8 m²/g, a morphology that is a combination of agglomeration and particles, and an optical band gap of 3.23 eV. It is concluded that synthetic rutile is a viable precursor to produce high quality titania nanoparticles.

Abstract: A pulsed spark-discharge aerosol generator using air as a carrier gas was successfully applied to the titania nanoparticle production. The titanium vapor evaporated by spark discharge was subsequently supersaturated and condensed to titania nanoparticles by nucleation and condensation. The size and concentration of the particles can be controlled easily using air as a carrier gas by altering the repetition frequency, capacitance, gap distance, and flow rate of the spark-discharge system. TEM observation shows that the generated particles were aggregates, which primary particle sizes are a few nanometers. The element composition of the nanoparticles was titanium and the crystal phase was amorphous. XPS analysis shows that oxidation state of generated particles corresponded to TiO2. These XPS data indicates that some fraction of the evaporated titanium vapor could be oxidized in an air atmosphere by the oxidation with oxygen. However, enough time for crystallization was lacked because of raid cooling.