کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1230591 | 1495240 | 2014 | 7 صفحه PDF | دانلود رایگان |
• We study the vibrational properties of monohydrate and dihydrate phases of calcium oxalate.
• We investigate the phase transformation of calcium oxalate dihydrate.
• We report a re-investigation of the vibrational spectra (Raman and IR) of whewellite.
• X-ray diffraction show the influence of relative humidity on the stability of weddellite.
• The new data achieved will provide essential information in medical and Cultural Heritage fields.
New data on vibrational properties of calcium oxalates and their controversial transformation mechanism are presented. We have focused on whewellite (CaC2O4·H2O) and weddellite [CaC2O4·(2 + x) H2O], the most common phases of calcium oxalate; these compounds occur in many organisms, in kidney stones and in particular kinds of films found on the surface of many works of art. Low temperature experiments carried out by Fourier transform infrared spectroscopy have highlighted both the high structural order in the crystalline state of whewellite and the disordered distribution of the zeolitic water molecules in weddellite. The synthesised nanocrystals of weddellite have been kept under different hygrometric conditions in order to study, by X-ray powder diffraction, the role of “external” water molecules on their stability. Moreover, in order to identify the different kinds of water molecules, a re-investigation, supported by quantum chemical calculations, of the observed vibrational spectra (IR and Raman) of whewellite has been conducted.
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Journal: Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy - Volume 128, 15 July 2014, Pages 413–419