Papers by Keyword: Pulsed Laser Ablation

Abstract: The impact of wavelength of the laser on several Topographical and Morphological characteristics of gold nanoparticles (Au NPs) was ablated utilizing pulsed laser ablation in liquid in this work. We employed a gold target with an extra purity to ablate the Nano-particles and a removal of tattoo Nd:YAG Q switching pulsed laser with a 10 Ns duration of pulses, the energy are 1000 mJ, the number of pulses are 600 pulses, and a frequency of 3 Hz to explore the gold NPs' characteristics using TEM and AFM. According to the greatest intensity of shorter wavelengths.

Abstract: Titanium dioxide and gold nanoparticles were synthesized using an environmentally friendly method to deposit undoped and Au-doped TiO₂ thin films on silicon and glass substrates via the spray pyrolysis technique. The effect of the Au nanoparticles concentrations on structural, morphological, and hydrogen sulfide (H₂S) gas sensing characteristics of TiO₂ thin films were investigated. An X-ray diffraction pattern confirmed the polycrystalline structure of the films deposited on glass and Si substrates with a dominant rutile phase and the formation of additional mixed-phases of Ti-Au bonding. According to a Field Emission-Scanning Electron Microscopy investigation, the cluster size ranged from 20 to 180 nm depending on the concentration of AuNPs. The sensing response of the prepared films was tested against H₂S at different operating temperatures. The effect of growing a mixture of titanium-gold phases as a suitable catalyst for hydrogen sulfide sensitivity is also discussed.

Abstract: YGdO₃:Er³⁺ nanoparticles were successfully synthesized by pulsed laser ablation in liquid method. The structural and morphological properties of the product are investigated by X-Ray diffraction and transmission electron microscopy. The upconversion photoluminescence properties were investigated in detail. Obvious stark splitting phenomena were observed in the green and red emission bands. The decay behaviors of three emission bands were studied. Based on thermal coupled energy level related upconversion fluorescence intensity ratio, the temperature sensing properties of product were studied. Linear function has beenused to reveal the relationship between fluorescence intensity ratio and temperature. Using stark sublevels related emission bands, sensitivity of the temperature sensor was successfully enhanced. These results suggest the YGdO₃:Er³⁺ nanoparticles prepared via pulsed laser ablation in liquid are promising luminescent materials for optical thermometry.

Abstract: Antibacterial composites based on linen and NPs obtained by pulsed laser ablation of a zinc target in air were synthesized at various concentrations of the active component (ZnO NPs). The surface morphology and optical properties of ZnO/linen composites were investigated by scanning electron microscopy and UV-visible spectroscopy. The antibacterial activity of ZnO/linen composites was tested on S.aureus in accordance with ISO 20743:2013. It was found that the antibacterial activity depends on the concentration of ZnO NPs. High antibacterial activity of the composites was achieved when the concentration of the active component was of 0.25 mg/cm2. At a concentration of 0.1 mg/cm2 the composites showed only a bacteriostatic effect. The use of photoactivation of composites by LED radiation of 365 nm for 10 min led to an increase in antibacterial activity about 1.5 times for the samples in both concentrations.

Abstract: Er³⁺ doped potassium sodium niobate (KNN: Er) ultrafine powders have been prepared by pulsed laser ablation in water. X-ray diffraction (XRD) pattern of the sample demonstrated that the as-synthesized powders were crystalized in orthorhombic phase. Scanning electron microscopy (SEM) and transmittance electron microscopy (TEM) images exhibited that the morphology of ultrafine powders are cube-like. Under the excitation of 980 nm laser, the sample exhibits green emission, which is originated from the transition of thermal coupled energy levels (²H_11/2, ⁴S_3/2) to ground state level ⁴I_15/2. Temperature dependent up-conversion emission intensity associated with thermal quenching of total green emission band and the fluorescence intensity ratio (FIR) between two sub-emission bands related to population of thermal coupled energy levels are investigated for temperature sensing in the temperature range of 300 K to 480 K. The temperature sensing performances related to different technique were discussed. A maximum relative sensitivity reaches 1.01% K^-1 at 464 K for emission intensity thermometry and that is 0.84% K^-1 at 374 K for FIR thermometry technique. All these results show that KNN: Er ultrafine phosphors prepared via pulsed laser ablation in water have prospect for non-contact temperature sensing.

Abstract: Colloidal solutions of copper (I) oxide, Cu₂O, were obtained by pulsed laser ablation of metallic copper target in distilled water using fundamental harmonic of Nd:YAG laser (1064 nm, 7 ns, 20 Hz). Nanocolloids obtained were applied to cotton fabric. Nanoparticles composition and structure were studied by UV-Vis and Raman spectroscopy, transmission and scanning electron microscopy, and XRD. Antibacterial activity of Cu₂O nanoparticles on cotton fabric to E.coli bacteria was demonstrated in comparison with zinc oxide nanoparticles.

Abstract: TiO_x/CdS composites were synthesized by CdS deposition on TiO_x from aqueous solutions of Cd (CH₃COO)₂ and Na₂S with and without addition of a stabilizing agent–Na₂SiO₃. Initial high-defective TiOx nanocrystalline powders were prepared by pulsed laser ablation (Nd:YAG laser, 1064 nm, 7 ns) of Ti target in H₂O. Composites obtained exhibit absorption in the visible range up to 520 nm. On the example of Rhodamine C photodecomposition in water it was revealed that the nanocomposite TiOx/CdS powders obtained exhibit good photocatalytic properties when excited by visible light.

Abstract: The synthesis of nanodiamonds by pulsed-laser ablation in liquid (PLAL) is an attractive research field in developing well-dispersed fluorescent nanodiamonds for bioimaging and life science. However, nanodiamonds are quite different from their widely pursued carbon allotropes both in synthesis conditions and physical properties. It is a great challenge to synthesize metastable phase nanodiamonds that prefer high temperature and high pressure. Despite the progress in the synthesis of nanodiamond by pulsed-laser ablation of graphite target using different laser power densities under room conditions, the transformation from graphite to nanodiamonds are not yet well explained. In order to have a better understanding to the formation of metastable nanodiamonds upon PLAL, the formation of nanodiamond has been elucidated from both the aspects of thermodynamics and kinetics. Due to low laser intensity and long wavelength, synthesis of nanodiamonds is the result of high cooling velocity of high-pressure and high-temperature carbon vapor condensation formed under laser vaporization of graphite particles. When diamond nuclei grow into the right size, they cannot increase and the graphite nucleation begins to form and grow on the diamond at given conditions due to long pulse width for ms-pulsed laser. In fact, the diamond particles enwrapped several layers of graphite have obtained. Moreover, the reasons related 3~6nm diamonds prepared by this new process and having narrow size distribution are also discussed.

Abstract: In this work the microscopic morphology of titanium carbide thin films, obtained by pulsed laser ablation, are studied. A target of TiC has been ablated in vacuum with a laser Twinkle of Light Conversion Ltd. capable to furnish impulses of 250 fs, with a repetition frequency of 10 Hz at the wavelength of 527 nm. The ablated material has been deposited on (111) oriented silicon substrates, maintained at ambient temperature during the film deposition. Digital images of the films have been acquired through scanning electron microscopy. Numerical codes have been developed in Matlab environment, to obtain a three-dimensional reconstruction of the film surfaces starting from the bidimensional images. On such reconstruction a multi-scale analysis has been performed by hilbertian methods, for the characterization of the surface roughness and to study the distribution of the deposited nanoparticles. The results show that the free surface of the film has a characteristics scale invariance that allow the description by multi-fractal techniques. In particular the fractal dimension of the surface has been calculated in nanometric range. The investigation allows to identify some proper morphological indicators to characterize the film geometry and parameterize the tribological properties of the interface. These indicators, if opportunely employed together with classical methods of analysis, furnish a further tool for better understanding the complex nature of the deposits.

Abstract: Barium Strontium Titanate Ba_0.8Sr_0.2TiO₃ (BST) thin films have been deposited on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition technique. The X-ray diffraction (XRD) shows that the films crystallize in a perovskite phase. XRD and Atomic Force Microscopy (AFM) characterization reveal that the grains are nano-sized. Rutherford Backscattering Spectrometry (RBS) analysis shows the stoichiometry of the films to be close to the stoichiometry of the target. The Raman spectroscopy shows that the films exhibit the tetragonal structure by the presence of the Raman active modes at 301 cm^-1 and 729 cm^-1, at room temperature. Leakage current measurements of Au/ Ba_0.8Sr_0.2TiO₃/Pt capacitors have been done, at room temperature, to investigate the conduction mechanisms of the films. We found that there are two different conduction regions in the capacitors, namely, an ohmic behavior at low voltages and a Schottky emission mechanism at high voltages. The Schottky barrier height has been estimated to be 0.99 eV.