Template-based growth of TiO₂ nanorods by sol-gel process

In this paper, the preparation of TiO2 nanorods by sol-gel-template process has been considered. The prepared sols were characterized by using FTIR spectroscopy, and the obtained nanorods were characterized by X-ray diffraction and SEM microscopy. SEM images show that TiO2 nanorods with uniform diameter of about 100-200 nm and a length of several micrometers. The results of XRD indicated that the TiO₂ nanorods were crystallized in the anatase and rutile phases after annealing to 400-700 ºC up to 2 hours

Quick and Easy Measurements of the Inherent Optical Property of Water by Laser

To compare properties of different waters we measured the reflectance of the second harmonic of Nd: YAG laser light through different water samples in the laboratory. To generate realistic images of natural waters one must consider in some details the interaction of light with the water body. The diagrams have been utilized to represent effective parameters in the water's reflectivity such as: the angle of incidence or the bottom conditions, height of the laser from water surface, wavelength of the laser light, radiant intensities, depth of water and also the impurities of water. The reflectance of the bottom from a mirror at the bottom of an aquarium with different depths of water will depend on the bottom slope relative to the direction of incidence of the laser light and the coating to prevent damaging the mirror against the laser light so it is necessary to change the mirror after several experiments.El presente trabajo muestra las mediciones hechas en diferentes líquidos para comparar sus propiedades, tomando como referencia la reflectancia de la segunda armónica de un laser Nd. YAG, esto a través de diferentes muestras de líquidos en el laboratorio. Para poder generar imágenes realistas se debe de considerar algunos detalles de interacción de la luz con el cuerpo líquido. Los diagramas fueron utilizados para representar parámetros efectivos de la reflexión del liquido como puede ser el ángulo de incidencia y las condiciones de fondo, la altura del laser respecto a la superficie del liquido, la longitud de onda de la luz laser, la intensidades de radiación la profundidad del líquido y las impurezas que pudieran existir. La reflexión de la profundidad utilizando un espejo a diferentes profundidades depende de la inclinación relativa a la dirección de incidencia del laser y de la protección del espejo para que no se dañe, por lo que es necesario cambiar el espejo después de varios experimentos

Effect of gold nanoparticles on the optical properties of Rhodamine 6G

Gold nanoparticles are synthesized by the laser ablation method and characterized by transmission electron microscopy and UV-visible absorption spectroscopy. The absorption and emission spectra and powers of Rhodamine 6G in the absence and presence of 27 nm diameter gold nanoparticles were studied. Empirical measurements represented that presence of gold nanoparticles lead to decrease the fluorescence power and fluorescence quantum yield, and increase the absorbance and absorbed power of Rhodamine 6G. Also, Stern-Volmer quenching constant of dye in proximity of nanoparticles shows high value which implies efficient quenching of the dye fluorescence by gold nanoparticles. Fluorescence quantum yield, radiative and nonradiative decay rate of Rhodamine 6G-gold nanoparticles assembly, in parallel orientation, as a function of dye’s dipole moment distance from gold nanoparticle’s surface, based on Gersten-Nitzan model, are calculated. Calculations show variations of the fluorescence quenching is strongly depended on the distance between the dye molecules and the Nps’ surface. Also, calculated radiative decay rate indicates good agreement with the experimental value, and results of the ratio of the nonradiative to the radiative decay rate of Rhodamine 6G-gold nanoparticles mixture show nonradiative energy transfer is better explained in terms of NSET rather than FRET mechanism

Synthesis and Characterization of Au-Zn Nanoalloy by Laser Irradiation in Liquid Media

Alloy nanoparticles due to their possibility of regulation, the region of absorption peak and consequently their optical and electrical properties, have a specific significance. In this research, nanosecond laser pulses of Nd:YAG laser with 532 nm wavelength that is close to absorption peak of gold and zinc nanoparticles, were used for synthesis of alloy. Atomic absorption spectrum UV-Visible, X-ray diffraction analysis and transmission electron microscopy images were utilized for characterization as well. For synthesis of Au-Zn alloy nanoparticles, zinc and gold nanoparticles were prepared separately by laser ablation method and then the mixture of their colloidal solutions with specified ratio was exposed to laser radiation. Thereby, gold and zinc nanoparticles were combined by absorbing of laser beam and gaining of required energy for melting, and Au-Zn alloy nanoparticles were formed. Wavelength of 532 nm is more effective in the formation of alloy than 1064 nm because of being close to wavelength of surface plasmon resonance of gold and zinc nanoparticles. Increase of concentration of gold nanoparticles compared to zinc nanoparticles in the mixed solution causes that gold nanoparticles absorb the most of the energy of laser and then larger gold particles are created, so alloy nanoparticles are not formed. The best time duration for irradiation and accomplishment of alloy formation is 30 min

Synthesis and Characterization of Au-Zn Nanoalloy by Laser Irradiation in Liquid Media

Alloy nanoparticles due to their possibility of regulation, the region of absorption peak and consequently their optical and electrical properties, have a specific significance. In this research, nanosecond laser pulses of Nd:YAG laser with 532 nm wavelength that is close to absorption peak of gold and zinc nanoparticles, were used for synthesis of alloy. Atomic absorption spectrum UV-Visible, X-ray diffraction analysis and transmission electron microscopy images were utilized for characterization as well. For synthesis of Au-Zn alloy nanoparticles, zinc and gold nanoparticles were prepared separately by laser ablation method and then the mixture of their colloidal solutions with specified ratio was exposed to laser radiation. Thereby, gold and zinc nanoparticles were combined by absorbing of laser beam and gaining of required energy for melting, and Au-Zn alloy nanoparticles were formed. Wavelength of 532 nm is more effective in the formation of alloy than 1064 nm because of being close to wavelength of surface plasmon resonance of gold and zinc nanoparticles. Increase of concentration of gold nanoparticles compared to zinc nanoparticles in the mixed solution causes that gold nanoparticles absorb the most of the energy of laser and then larger gold particles are created, so alloy nanoparticles are not formed. The best time duration for irradiation and accomplishment of alloy formation is 30 min

Determination of Dose-Equivalent Response of A Typical Diamond Microdosimeter in Space Radiation Fields

Introduction: Microdosimeters are helpful for dose equivalent measurement in unknown radiation fields. The favorable physical and mechanical properties of the detector-grade chemical vapor deposition diamond materials have made the diamond microdosimeters suitable candidate for radioprotection applications in space. The purpose of this work is the investigation of the dose equivalent response of a typical diamond microdosimeter with laser-induced graphitized electrodes for use in space radiation fields. Materials and Methods: The Geant4 Monte Carlo simulation toolkit was applied to simulate the particle transport within the microdosimeter, and to determine the mean chord length and the dose equivalent response of the microdosimeter, based on the lineal energy dependent quality factor.   Results: The linear stopping power of the protons and alpha particles with energies higher than 5 MeV and 10 MeV respectively can be estimated within20% of deviation using the microdosimeter response. The fluence to dose equivalent conversion coefficients calculated affirms that there is an adequate agreement between the calculated coefficients and other research group results. Conclusion: The reasonable agreement between the dose equivalents calculated in this study and the results reported by other researchers confirmed that this type of microdosimeter could be a promising candidate suitable for the measurement of the dose equivalent in space radiation fields

Synthesis of highly doped Nd:YAG powder by the SOL-GEL method

The sol-gel method was used for synthesizing Nd:YAG powder. The process contains several steps, for example solving in acid, mixing, evaporation etc. The XRD analysis of prepared powder by sol-gel method showed that the YAG single phase is resulted by heat treatment at 900 ºC for 2 hr. By SEM the homogeneity of Nd distribution in the YAG lattice was observed