Laser-Induced Synthesis of Pure Zinc Oxide Nanoflakes

Abstract

Nanostructured zinc oxide (ZnO) has received immense attention as a low-cost and non-toxic photo-active material for different applications such as photocatalysis, photovoltaics, photonic and bio-medical fields. Herein, facile crystalline ZnO nanoflakes were prepared by homogeneous precipitation followed by laser-induced recrystallization and without the use of any organic ligand. The effect of laser type and wavelength on the recrystallization process was studied adopting a pulsed nitrogen laser (λ=337 nm) and a continuous argon laser (λ=488 nm). The pulsed nitrogen laser features a pulse duration of 150±1 ns, pulse energy of 1.3±0.3 mJ, and a target irradiance of 5.7±0.5 kW/cm2 while the continuous argon laser provides an irradiance of 10±0.3 mW/cm2. The morphology, structure and optical properties of the prepared nanostructures were studied using a scanning electron microscope (SEM), X-ray diffraction (XRD), UV-Visible, photoluminescence (PL), and Raman spectroscopy. The results confirm the formation of pure ZnO nanoflakes of the wurtzite structure. The laser-induced evolution of ZnO nanoflakes depends on the nature of the precipitating agent, laser energy and exposure time. The ZnO nanoflakes prepared using urea-assisted homogeneous precipitation is more advantageous than that precipitated with NaOH. Moreover, the pulsed nitrogen laser of higher irradiance demonstrated an enhanced formation of ZnO nanoflakes after 90 min of irradiation. The laser irradiation provides a facile synthetic route to pure ZnO nanostructures for various applications.

Insight into novel anti-mucormycosis therapies: investigation of new anti-mucormycosis laser-induced photodynamic therapy based on a sulphone bis-compound loaded silica nanoemulsion

“…The first peak of the SBDMP is located at 256 nm with a 4 nm blue wavelength shift while the second peak is still at 292 nm due to the increase in the size of the silica nanoemulsion particles from 100 nm to 259 nm upon loading of the SBDMP. 29,41 These results are in agreement with TEM results and zeta potential evaluations. The SBDMP absorption spectra shows that any photo-induced activity by the developed silica nanoemulsion is initiated by two-photon absorption (TPA).…”

“…The laser beam has a diameter of 24 mm and a divergence of 4 mrad. A plano-convex quartz mirror with a focal length of 10 cm was used to focus the beam on the sample on one wall of a 96-wall polypropylene plate at an angle of 45°from the laser axis center, 7,24,29 with Fig. 1 illustrating the LIPDT system setup.…”

“…5. 7,29,46 The second small emission band at 465 nm can be attributed to the emission of silica nanoemulsion that is deposited on the surface of SBDMP-loaded silica nanoemulsion. This emission band is induced by electron-hole recombination between self-trapped excitons and oxygen-decient centers in silica.…”

Development of Antimicrobial Laser-Induced Photodynamic Therapy Based on Ethylcellulose/Chitosan Nanocomposite with 5,10,15,20-Tetrakis(m-Hydroxyphenyl)porphyrin

“…This process minimizes the overheating of the tissue with laser light. Moreover, the laser light can easily be focused into optical fibers and transported over long distances inside the body cavities or through the lumens of needles into illuminated tissue [8][9][10]. Additionally, certain laser wavelengths (from red light to NIR) are preferable for aPDT due to the thermal and penetration interactions with microbes, antimicrobial agents, and/or tissue [11,12].…”