Muséum national d'histoire naturelle, Département de Préhistoire UMR 7194, Centre de spectroscopie infrarouge, Paris, France.
Spectrochim Acta A Mol Biomol Spectrosc. 2011 May;78(5):1476-81. doi: 10.1016/j.saa.2011.01.036. Epub 2011 Feb 1.
Chalcedony consists of hydroxylated 50-100 nanometre measuring α-quartz (SiO(2)) crystallites that lose their surface silanole groups (Si-OH) upon heating between 350°C and 600°C. The loss of the chalcedony's ≈1% of silanole groups allows for the healing of water related defects in the crystallites. We investigated these crystallographic transformations using Fourier Transform mid Infrared Spectroscopy in direct transmission, Attenuated Total Reflection (ATR) and the reflectivity. We found that an absorption band that is specific for chalcedony at 555 cm(-1) disappears gradually upon heating between 350°C and 600°C. The reduction of the band is correlated to the loss of surface silanoles. This result leads to the assignment of the band to free Si-O vibrations in non bridging Si-OH groups that have a lower natural frequency than Si-O vibrations in bridging Si-O-Si. The recognition of a silanole signal in the mid infrared allows for an easy, cheap and rapid recognition of hydroxyl in chalcedony.
玉髓由羟基化的 50-100 纳米 α-石英（SiO(2)）纳米晶组成，在 350°C 至 600°C 之间加热时，其表面硅醇基团（Si-OH）会丢失。玉髓中约 1%的硅醇基团的丢失使得纳米晶中的水相关缺陷得以修复。我们使用傅里叶变换中红外光谱在直接透射、衰减全反射（ATR）和反射率下研究了这些晶体结构的转变。我们发现，555 cm(-1)处专属于玉髓的吸收带在 350°C 至 600°C 之间加热时逐渐消失。该带的减少与表面硅醇基团的损失有关。这一结果表明，该带与具有较低自然频率的非桥接 Si-OH 基团中的游离 Si-O 振动有关，而不是桥接 Si-O-Si 中的 Si-O 振动。中红外对硅醇信号的识别可以很容易、廉价和快速地识别玉髓中的羟基。
