Spectral analysis of electronic transitions for low doping concentration of nickel ions in silica matrices at different phases

• Absorption spectra of Ni complex doped silica are describe in three phases
• Racah parameter and ligand field strength are strongly dependent on sol–gel phase
• Drying temperature can design the symmetry site of Ni ion in silica
• Many spin forbidden transitions can be incited via the preparation process

The electronic transitions of nickel (II) complex in solution, Sol and Xerogel silica matrices hosts have been investigated. Water and ethanol start solvents are both tested in doping the metal complex within silica matrices using sol–gel technique. Sol–gel parameters employed for preparing good optical quality monoliths were precisely selected. Racah parameter, ligand field strength and nephelauxetic ratio for nickel (II) has been employed to verify the ion coordination in these three phases. The three well-known spin allowed transitions were diagnosed for all phases and at several drying temperatures. Whereas further three spin-forbidden transitions were also progressively evaluated and recorded as the drying temperature increases from 60 to 600 °C. The IR spectra substantiate the previous insight, which believed that the nickel ion could incorporate within silica matrices immediately after reaching the gelling point when the preparation temperature was above 60 °C. SEM investigation reveals that, as the drying temperature increased the symmetry site of Ni ions incorporated with silica matrices slightly converted from octahedral to tetrahedral site.