2Research Center on Advanced Materials and Technologies, Department of Exact and Natural Sciences, Institute of Interdisciplinary Research, Alexandru Ioan Cuza University of Iasi, Iasi, Romania.1Faculty of Physics, Alexandru Ioan Cuza University of Iasi, Iasi, Romania.Teodora Matei 1 Vasile Tiron 2 Roxana Jijie 2 Georgiana Bulai 3 Ioana-Laura Velicu 1* Daniel Cristea 4 Valentin Crăciun 5,6