A research team led by Dr. WANG Zhenyou, Research Fellow at the Aerospace Information Research Institute, Chinese Academy of Sciences (AIRCAS), has developed a microscopic time-gated Raman spectrometer that enables non-destructive, micrometer-scale chemical analysis of fragile archaeological ivory—even when strong fluorescence would normally obscure the signal. The study was published in ACS Applied Materials & Interfaces.
Ivory artifacts excavated from the Sanxingdui Ruins, dating back more than 3,000 years, are invaluable for understanding the ancient Shu civilization. However, prolonged burial conditions—including groundwater, soluble salts, and microbial activity—can severely weaken ivory internally while leaving the exterior seemingly intact. This makes non-destructive, high-resolution analytical tools essential for conservation and restoration.
Raman spectroscopy, widely used for molecular composition, is in principle well suited to this task. In practice, however, archaeological materials frequently produce strong fluorescence under laser illumination, overwhelming the much weaker Raman signals and rendering conventional measurements ineffective.
To address this challenge, the research team developed a time-gated Raman approach that separates Raman scattering signals from fluorescence based on their fundamentally different time scales. Raman signals occur instantaneously after laser excitation, whereas fluorescence persists much longer. By synchronizing an ultrashort detection window precisely with the Raman signal, the instrument effectively suppresses fluorescence background and recovers Raman spectra from strongly fluorescent materials.
Through a combination of hardware design and algorithm optimization, the team achieved efficient fluorescence suppression, improved the localization of key chemical components, and reduced overall system cost—an important step toward wider adoption of time-gated Raman technology in heritage science.
The team applied the new instrument to four ivory fragments excavated from Sanxingdui. Under conventional continuous-wave Raman conditions, two samples yielded little or no usable spectral information due to fluorescence. In contrast, the time-gated Raman measurements effectively suppressed fluorescence interference and improved the signal-to-noise ratio by more than 20 times in strongly fluorescent samples, revealing clear internal compositional differences.
The analysis shows that ivories from different burial environments exhibits pronounced differences in organic content, mineral crystallinity, and corrosion severity. The results further suggest that metal-ion infiltration and non-metal ion substitution, such as sulfate replacing structural components in hydroxyapatite, play a central role in deep ivory degradation. In some specimens, spectral features consistent with possible heat exposure were also observed, pointing to potential fire-related damage.
Overall, the study demonstrates that time-gated Raman spectroscopy can provide molecular-level evidence critical for understanding how ancient ivory deteriorates over time, offering a robust scientific basis for conservation decisions and restoration strategies. Beyond ivory, the method is expected to be broadly applicable to archaeological materials that suffer from strong fluorescence.
In December 2025, the team was invited to present this work at the 13th International Conference on Advanced Vibrational Spectroscopy (ICAVS 13), where it attracted significant interests from experts in archaeology and spectroscopy and sparked discussion on future collaboration and commercialization.
This study was conducted in collaboration with researchers from the Sichuan Provincial Institute of Cultural Relics and Archaeology, Zhejiang University, and the University of Electronic Science and Technology of China.
Prototype of the microscope-integrated time-gated Raman spectrometer. (Image by AIRCAS)
Time-gated Raman spectroscopy and its application to the analysis of ivory from the Sanxingdui Ruins. (Image by AIRCAS)
Research News
Time-Gated Raman Spectroscopy Reveals How 3,000-Year-Old Sanxingdui Ivory Degraded—Despite Intense Fluorescence
A research team led by Dr. WANG Zhenyou, Research Fellow at the Aerospace Information Research Institute, Chinese Academy of Sciences (AIRCAS), has developed a microscopic time-gated Raman spectrometer that enables non-destructive, micrometer-scale chemical analysis of fragile archaeological ivory—even when strong fluorescence would normally obscure the signal. The study was published in ACS Applied Materials & Interfaces.
Ivory artifacts excavated from the Sanxingdui Ruins, dating back more than 3,000 years, are invaluable for understanding the ancient Shu civilization. However, prolonged burial conditions—including groundwater, soluble salts, and microbial activity—can severely weaken ivory internally while leaving the exterior seemingly intact. This makes non-destructive, high-resolution analytical tools essential for conservation and restoration.
Raman spectroscopy, widely used for molecular composition, is in principle well suited to this task. In practice, however, archaeological materials frequently produce strong fluorescence under laser illumination, overwhelming the much weaker Raman signals and rendering conventional measurements ineffective.
To address this challenge, the research team developed a time-gated Raman approach that separates Raman scattering signals from fluorescence based on their fundamentally different time scales. Raman signals occur instantaneously after laser excitation, whereas fluorescence persists much longer. By synchronizing an ultrashort detection window precisely with the Raman signal, the instrument effectively suppresses fluorescence background and recovers Raman spectra from strongly fluorescent materials.
Through a combination of hardware design and algorithm optimization, the team achieved efficient fluorescence suppression, improved the localization of key chemical components, and reduced overall system cost—an important step toward wider adoption of time-gated Raman technology in heritage science.
The team applied the new instrument to four ivory fragments excavated from Sanxingdui. Under conventional continuous-wave Raman conditions, two samples yielded little or no usable spectral information due to fluorescence. In contrast, the time-gated Raman measurements effectively suppressed fluorescence interference and improved the signal-to-noise ratio by more than 20 times in strongly fluorescent samples, revealing clear internal compositional differences.
The analysis shows that ivories from different burial environments exhibits pronounced differences in organic content, mineral crystallinity, and corrosion severity. The results further suggest that metal-ion infiltration and non-metal ion substitution, such as sulfate replacing structural components in hydroxyapatite, play a central role in deep ivory degradation. In some specimens, spectral features consistent with possible heat exposure were also observed, pointing to potential fire-related damage.
Overall, the study demonstrates that time-gated Raman spectroscopy can provide molecular-level evidence critical for understanding how ancient ivory deteriorates over time, offering a robust scientific basis for conservation decisions and restoration strategies. Beyond ivory, the method is expected to be broadly applicable to archaeological materials that suffer from strong fluorescence.
In December 2025, the team was invited to present this work at the 13th International Conference on Advanced Vibrational Spectroscopy (ICAVS 13), where it attracted significant interests from experts in archaeology and spectroscopy and sparked discussion on future collaboration and commercialization.
This study was conducted in collaboration with researchers from the Sichuan Provincial Institute of Cultural Relics and Archaeology, Zhejiang University, and the University of Electronic Science and Technology of China.
Prototype of the microscope-integrated time-gated Raman spectrometer. (Image by AIRCAS)
Time-gated Raman spectroscopy and its application to the analysis of ivory from the Sanxingdui Ruins. (Image by AIRCAS)