Laser & Optoelectronics Progress, Volume. 58, Issue 24, 2430001(2021)

Raman Spectrum Characteristics and Coloration Mechanism of Freshwater-Nucleated Pearls

Xiaoyi Yang1,2, Zhengyu Zhou1,2、*, Xiaoman Qi3, Zhiwei Zhang4, and Zongting Liao1,2
Author Affiliations
  • 1State Key Laboratory of Marine Geology, Tongji University, Shanghai 200092, China
  • 2Laboratory of Gem and Technological Materials, Tongji University, Shanghai 200092, China
  • 3Zhejiang Angeperle Company Limited by Shares, Zhuji, Zhejiang 311800, China
  • 4National Gemstone Testing Center, Shanghai 200122, China
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    Gabriel pearls are freshwater-nucleated pearls developed in recent years cultured in the mantle of Hyriopsis cumingii. In response to its coloration mechanism, scholars have proposed diversified viewpoints. In our research, both laser Raman spectroscopic and micro-infrared spectroscopic analyses were performed on Gabriel pearls with carotenoid standard samples (β-carotene and astaxanthin) as reference materials for a better understanding of the coloration mechanism, which was expected to provide a scientific theoretical basis for quality evaluation and cultivation technology of these pearls. The results confirmed the strong 1509 and 1126 cm -1 Raman peaks of the nacre of freshwater colored nucleated pearls attributed to ν1(C=C) and ν2(C—C) stretching vibration modes of carotenoid-binding protein, respectively. The presence of a weak peak at 1017 cm -1 was associated with the plane oscillation of CH3 (ν3). Raman spectra in the range of 2100--3800 cm -1 revealed five groups of peaks with varying intensities, which were attributed to frequency multiplication and combined frequency vibration of ν1, ν2, and ν3. Notably, there was a correlation between the number of conjugated double bonds of carotenoid molecules or carotenoid-binding proteins and the color of freshwater-nucleated pearls, indicating one of the reasons for the coloration diversity of pearl color.

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    Xiaoyi Yang, Zhengyu Zhou, Xiaoman Qi, Zhiwei Zhang, Zongting Liao. Raman Spectrum Characteristics and Coloration Mechanism of Freshwater-Nucleated Pearls[J]. Laser & Optoelectronics Progress, 2021, 58(24): 2430001

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    Paper Information

    Category: Spectroscopy

    Received: Oct. 20, 2020

    Accepted: Jan. 22, 2021

    Published Online: Dec. 3, 2021

    The Author Email: Zhou Zhengyu (06058@tongji.edu.cn)

    DOI:10.3788/LOP202158.2430001

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