TPR, EPR and UV-Vis studies of Ni(II) speciation in chrysoprase
Sojka, Zbigniew; Witkowski, Stefan; źabiński, Witold; Dyrek, Krystyna; Bidzińska, Ewa
published: Jan 16, 2004
TPR (Temperature Programmed Reduction) and EPR (Electron Paramagnetic Resonance) corroborated with UV-Vis methods were used to get a new insight into the status of nickel ions in chrysoprases from various localities. The investigation showed speciation of Ni into 2:1 highly dispersed phyllosilicates and extra-framework species grafted on the surface of chalcedony matrix. Both kinds of nickel exhibit a distorted octahedral coordination giving rise to a broad EPR spectrum with g = 2.17 and three characteristic d-d bands that can be parameterised with 10Dq = 8897cm-1 and B = 953cm-1.