Crecimiento de nanopartículas de cobre en matriz de erionita

Abstract

Unreduced and reduced in hydrogen flow copper exchanged synthetic erionite, with a SiO$_{2}$/Al$_{2}$O$_{3}$ molar ratio of 7.7, have been characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), and electron spin resonance spectroscopy (ESR). The XRD patterns show that the reduction process does not change the zeolite structure, besides the reduced form at 450$^{\circ}$C present diffraction lines assigned to copper metallic particles. The DRS measurements have detected isolated Cu$^{2 + }$ ions as well as plasma resonance peak of copper metallic nanoparticles. The ESR simulation analysis of the spectra measured at 20$^{\circ}$C indicates the presence of two different Cu$^{2 + }$ ions sites localized in the erionite matrix. Up to 450$^{\circ}$C only one type of sites take place in the reduction process, participating in Cu metal clusters and Cu metal nanoparticles formation, keeping the Cu$^{2 + }$ ions of the second site intact.