Synthesis and vibrational spectroscopic characterisation of nickel containing aurichalcite

Abstract

Raman spectroscopy complimented with supplementary infrared spectroscopy has been used to characterise a synthetic nickel substituted aurichalcite a zinc/nickel hydroxy carbonate, (Zn2+,Cu2+,Ni2+ )5(CO3)2(OH)6. XRD patterns show high orientation and indicate the presence of some minor impurities. The diffraction patterns for the Ni-aurichalcite are well correlated with the standard reference patterns. EDAX analyses indicate variations in chemical composition of Zn/Ni ratios of ~20:1. The symmetry of the carbonate anion in aurichalcite is Cs and is composition dependent. This symmetry reduction results in multiple bands in both the symmetric stretching and bending regions. The intense band for the Ni-aurichalcite at 1070 cm-1 is assigned to the ν1 (CO3)2- symmetric stretching mode. Three Raman bands assigned to the ν3 (CO3)2- antisymmetric stretching modes are observed for Ni-aurichalcite at 1372, 1480 and 1543 cm-1. Multiple Raman bands are observed in the region from 800 to 850 cm-1 and 720 to 750 cm-1 regions and are attributed to ν2 and ν4 bending modes confirming the reduction of the carbonate anion symmetry in the aurichalcite structure. This research proves that nickel containging aurichalcites can be synthesised in the laboratory thus mimicing the natural nickel containing aurichalcites.