Stability and transformation mechanism of weddellite nanocrystals studied by X-ray diffraction and infrared spectroscopy

Stability of weddellite, the dihydrate phase of calcium oxalate [CaC2O4(H2O)2+x], mainly detected in kidney stones and in oxalate films found on the surfaces of several ancient monuments, has been studied. Under ambient conditions, weddellite is unstable and quickly changes into whewellite, the monohydrate phase of calcium oxalate (CaC2O4H2O). Crystal structure of weddellite was detd. by single crystal X-ray diffraction. Synthesized nanocrystals of weddellite were kept under different hygrometric conditions in order to study, by X-ray powder diffraction, the effect of humidity on their stability. The mechanism of transformation of weddellite nanocrystals has been investigated by IR spectroscopy using D2O as a structural probe.