W.O.R. acknowledges FAPERJ (Brazilian Fund Agency) for financial support. C.G. acknowledges the financial support from Proyecto Basal FB 0821. P.V. acknowledges the financial support from Financiamiento Basal para Centros Cientificos y Tecnologicos de Excelencia (Chile) through the Center for Development of Nanoscience and Nanotechnology (CEDEN-NA). J. Lopez acknowledges the financial support from DGIP-PIIC. This research was also supported by Fondecyt grants no. 1140552 and 1130950. Spanish MINECO funds under research projects nos. MAT2013-48054-C2-2-R and MAT2016-76824-C3-3-R and Principado de Asturias from FICyT project no. FC-15-GRUPIN14-085 are also acknowledged. Shared research facilities from SCTs of University of Oviedo are also gratefully recognized.