Optical and fluorescence properties of Dy2O3-doped P2O5+K2O+MgO+Al2O3 and P2O5+K2O+MgO+MgF2+Al2O3 glasses have been investigated at room temperature. From the optical absorption measurements and using Judd–Ofelt (JO) theory, JO parameters have been obtained which are used to predict the radiative properties of 4F9/2 level of Dy3+ ion. A strong yellow (Y) and blue (B) emissions corresponding to 4F9/2→6H13/2 and 4F9/2→6H15/2 transitions of Dy3+ ions were observed in these glasses. A good correlation between the intensity ratio (Y/B) and Ω6/Ω2 was identified. The CIE colour coordinates were evaluated from the emission spectra to simulate white light emission from the title glasses. Fluorescence decay curves of the 4F9/2→6H13/2 transition have been measured and analysed. The product of σemxτexp reveals the possibility of using these glasses for yellow laser

This article reviews the basic theoretical aspects of graphene in order to contribute to making teaching easier and more understandable for those who still cannot understand it in an abstract way. This work presents the basic aspects of sp2 hybridization concepts from a quantum approach, which consists in obtaining the states for the sigma bonds from carbon atoms orientation close to another carbon atom that is our reference point in the crystal lattice. Furthermore, we calculate the band structure of graphene by using the tight-binding model, which can give us a good approximation to the energy levels as a function of the wave vector. This is for students interested in solid-state topic and it is approached in a simple and understandable way step by step to finally obtain the bands structure of the primitive cell of graphene monolayer. Additionally, we calculate the high symmetry points of the first Brillouin zone and the analysis around K points to obtain the well-known Dirac cones. The intention of this work is to show that this topic can be less abstract than it seems.