物理法改色前后优质淡水珍珠的超微结构特征研究

The Ultrastructure Characterization of High-Quality Freshwater Cultured Pearls Modified by Color Using Physical Method

利用原子力显微镜(AFM)、场发射高分辨率扫描电子显微镜(FESEM)和场发射高分辨率透射电子显微镜(HRTEM)对物理法改色前后的优质淡水珍珠表面进行了细致的观察。通过对比分析珍珠在微米级至纳米级的范围内微结构及超微结构特征的变化,证明珍珠质层是天然的纳米材料;改色前后珍珠的红外光谱分析及XRD分析对物理法改色珍珠机理是由于微量MnCO3在γ射线辐照下氧化成Mn2O3或MnO2所致的说法给予否定;由红外光谱测试结果可知物理法改色珍珠呈色机理与珍珠中有机物的辐照化学变化有关,并且物理法改色珍珠伴色的呈色机理与珍珠的文石纳米粒径效应亦无明显的相关性。

We investigate morphology and microstructure of color modified high-quality fresh water cultured pearls by using physical method with atomic force microscopy （AFM）, field emission scanning electron microscopy （FESEM） and high resolution transmission electron microscopy （HRTEM）, respectively. The results indicate that nacre in pearls is a kind of natural nano material. In addition, the results of FTIR and XRD analyses are a considerable chal- lenge to the mechanism of pearl color modification with physical method. The mechanism presumes that the color change in such pearls is caused by oxidation of trace MnCO3 to Mn2O3 or MnO2 under the γ-ray irradiation. In fact, in this work, a color-forming mechanism via physical method is involved with the irradiation- induced chemical changes of organic matter in pearls. Moreover, there is no obvious correlation between the color-forming mechanism and the effect of aragonite nanometer particle size of pearls.