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HKBU invents patented laser technology for artwork and antique authentication

Professor Cheung Nai-ho (left) and Dr Bruno Cai (right) demonstrate using the patented laser technique to analyse the chemical information of cinnabars on a Chinese painting.

Professor Cheung Nai-ho of the Department of Physics and his former PhD student Dr Bruno Cai have developed a laser technique that can sensitively analyse the chemistry of artwork such as antiques and paintings. Unlike conventional laser ablative microprobes, their technique causes no visible damage to artwork even under high-magnification microscope. The new method measures the chemical information in real-time and achieves 100 to 1,000 times better sensitivity than current methods. The technology has been granted a US patent and the team has set up a company to collaborate with local as well as overseas museums/institutes and private collectors to analyse paintings, ceramics, frescoes and other art objects.

Zep2Probe, the instrumentation platform developed by the team, delivers a laser pulse onto the sample and vaporises about one nanogram of the material. The gas plume so produced is excited to fluoresce by another ultra-violet laser pulse. The fluorescence reveals the elemental composition of the sample.

Professor Cheung Nai-ho said, “Conventional laser microprobes typically remove micrograms of material from the artwork surface. This causes visible and irreversible damage to the sample. Using the new technology, only one nanogram or less of the material is vaporised for detection. Damage will not be visible even when examined under a microscope. The fluorescence signal is then analysed by comparing it against our proprietary database to trace the provenance of the artwork.”

Using the detection of silicon in colour pigments as an example, conventional laser microprobes such as laser-induced breakdown spectroscopy require about one picogram (10-12 g) of silicon in the vapour plume to register a signal while the new technology requires only one femtogram (10-15 g).

Dr Bruno Cai said, “Our team is collaborating with local and overseas partners such as museums to analyse pigments on paintings as well as ceramic artefacts. Specific examples include the analysis of Chinese black inks and cinnabars on xuan paper and the chemical sorting of Yixing teaware. The technology can also be used in the forensic analysis of questioned documents.”

Please click here to see the damage comparison after using conventional laser-induced breakdown spectroscopy (LIBS) and patented technology plume laser-excited atomic fluorescence (PLEAF) on cinnabars (above) and laser printed ink (below).

(Adapted from HKBU eNews, CPRO)