Efecto de la temperatura de recocido en la cristalinidad y tamaño de nanoparticulas de ZnO sintetizadas por el método Sol-Gel
Resumen
Se han producido nanopartículas de ZnO a través del método Sol-Gel, evaluando el efecto de la temperatura de recocido (350, 450, 550 y 650°C) sobre su cristalinidad y tamaño.
Mediciones de difracción de rayos X evidencian que, incluso sin necesidad de recocido, las nanopartículas de ZnOpresentan fase wurtzita con estructura hexagonal sin presencia de fases secundarias. La cristalinidad de las nanopartículas mejora a medida que aumenta la temperatura, produciéndose al mismo tiempo un aumento en su tamaño desde 10 hasta 30nm. Los resultados de FT-IR muestran la presencia de grupos acetato en las nanopartículas sin recocido, eliminándose con el tratamiento térmico. Mediante espectroscopiaRaman se han determinado tres bandas características del ZnO en las nanopartículas sin recocido, siendo la H más intensa la correspondiente al modo E cuya intensidad aumentó para las nanopartículas 2 recocidas a 650°C para la cual se observaron otras bandas características del ZnO. Los resultados de fotoluminiscencia muestran que las nanopartículas presentan una intensa
emisión ultravioleta pero débil emisión visible, no apreciándose efecto significativo del recocido.
Palabras clave: Nanoparticulas, óxido de zinc, Sol-Gel, recocido, cristalinidad.
ABSTRACT
ZnO nanoparticles have been synthesizedby using the Sol-gel method and the effect of annealing temperature (350, 450, 550 y 650°C) on theircrystallinity and size have been evaluated. X-ray diffraction measurements evidenced thatall ZnO nanoparticles showed hexagonal wurtzite, and no secondary phases were detected. Enhancing of crystallinityand an increasing of average particle size, from 10 to 30nm, as annealing temperature increased was clearly observed. Fourier Transform Infrared results showed the presence of acetate groups on no annealed nanoparticles, which were eliminated after annealing treatment. By Raman spectroscopy three characteristic bands of ZnO have been identified in as synthesized H nanoparticles, being the most intense the corresponding to the E mode, whose intensity 2 increased for the nanoparticles annealed at 650°C for which other characteristic bands of ZnO were clearly identified. Photoluminescence spectra showed that ZnOnanoparticles present an intense ultraviolet and a weak visible emission, and no significant effect of annealing was observed.
Key words: Nanoparticles, zinc oxide, Sol-Gel, annealing, crystallinity
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