【摘要】 淡水有核珍珠因为其粒径大、圆度好、色彩丰富、光泽强等优点,在珍珠市场上占据了较大份额。目前关于彩色淡水有核珍珠的致色机理尚没有一致的结论,且关于该致色物质如何使淡水有核珍珠呈现多种颜色的研究较少。基于此研究现状,选取多种颜色的淡水有核珍珠进行激光拉曼光谱与色度学研究。拉曼光谱研究发现样品具有三种不同的C—C与■峰,且表现出对应关系:1123～1125cm^-1处的C—C峰常与1506～1509cm^-1处的■峰同时出现;1132～1134cm^-1处的C—C峰常与1522～1523或1525cm^-1处的■峰同时出现;1128～1131cm^-1处的C—C峰常与1506～1509与1520～1523或1525cm^-1的■双重峰同时出现。依据拉曼光谱中■键峰的差异将全部样品分为P、T、G、P+T、T+G、P+G共6种类型。结合样品的色度学参数,在同类型样品中,建立亮度L或饱和度S与其拉曼光谱中CO₃/C—C峰面积比的相关性,发现P型珠的亮度L与CO₃/C—C峰面积比有明显的正相关性,而P、T、G型珠的饱和度S都与CO₃/C—C峰面积比有明显的负相关性,证实三种不同的C—C与■峰是由不同的致色物质所致。并根据拉曼谱峰将彩色淡水有核珍珠中的致色有机物归属为线性多烯类分子。线性多烯分子的拉曼峰位随着有序度的增加而红移,拉曼峰位更靠近红外区的线性多烯分子的碳骨架更长更直,这导致不同类型样品的拉曼光谱中C—C与■的峰有所区别。此外,依据色度学参数对彩色淡水有核珍珠进行颜色系列的划分。将色调角h∈（0,15）的珍珠归为红色系列;将色调角h∈（15,45）的珍珠归为黄色系列;将色调角h∈（335,360）的珍珠归为紫色系列。更多还原

【Abstract】 Freshwater nucleated pearls have gained a significant share in the pearl market, due to their large size, good roundness, rich color, and strong luster. However, there is still no explicit conclusion on color-causing mechanism in colored freshwater nucleated pearls, which is attributed to the fact that there are very few studies currently focused on the mechanism research. Herein, we filtrate multiple colors of freshwater cultured pearls to study the mechanism via laser Raman spectroscopy and colorimetry. The Raman spectroscopy revealed these samples possess three different C—C and C=C peaks, exhibiting interesting corresponding relationship, which means the concurrence of C—C(1 123～1 125 cm^-1) corresponding to the C=C(1 506～1 509 cm^-1), the C—C(1 132～1 134 cm^-1) corresponding to the C=C(1 522～1 523 cm^-1) or the C=C(1 525 cm^-1), the C—C(1 128～1 131 cm^-1) corresponding to the C=C double peak(1 506～1 509 and 1 520～1 523 or 1 525 cm^-1). Owing to the differences of CC peaks in the Raman spectra, the samples were classified into P, T, G, P+T, T+G, and P+G. Combining with the chromatic parameters, we explored the relationship between the lightness（L） or saturation（S） and the CO₃/C—C peak area ratio in the same type, displaying the positive correlation between the lightness（L） and the CO₃/C—C peak area ratio for P-type pearls. In contrast, the negative correlation was found between the saturation（S） and the CO₃/C—C peak area ratio for P, T, and G types, which confirmed that the three different C—C and C=C peaks were caused by different color-causing substances. Moreover, we attributed color-causing organic compounds to linear polyenes by Raman spectroscopy. The Raman peaks of linear polyenes show redshift with the increase of orderliness. Linear polyene molecules with peaks closer to the infrared region have more extended and straighter carbon skeletons, which leads to the difference between the peaks of C—C and C=C in the Raman spectra of different samples. We also categorised the colored freshwater nucleated pearls via chromatic parameters. The pearls with hue angle（h）∈（0, 15）,（15, 45）,（335, 360） are classified as the red series, yellow series, and purple series, respectively.更多还原