Combining Laser Beams and Nanometallic Particles, NYCU Extends the Mercury Content Detection Threshold Limit to 0.2 ppb

  • Post category:News

The legally regulated natural residue concentration of mercury in cosmetics is 1 ppm. Institute of Biophotonics of National Yang Ming Chiao Tung University successfully combined magneto-plasmonic nanoparticles with laser beams and applied surface-enhanced Raman scattering to extend the measurement threshold limit to 0.2 ppb. The technology can help introduce more convenient methods for heavy metal detection.

Taiwan Food and Drug Administration stipulates that except for natural residue, heavy metal mercury is not allowed to be added to cosmetics. However, because mercury inhibits tyrosinase activity in the skin and reduce the generation of melanin, some unscrupulous vendors still add mercury to cosmetics. Therefore, heavy metal content of skin whitening cosmetic products has always been the focus of inspection. Nonetheless, heavy metal detection processes mostly rely on bulky devices, such as a mass spectrometer, in the laboratory to complete the detection.

After light is injected into an object, the scattered wavelengths and the original incident wavelengths may differ according to the materials of the object. This is called the principle of Raman spectroscopy, which has been considered have the potential for material analysis. However, the weak scattering signal, together with the interference of light reflected by objects have posed challenges to analysis of the signals.

To overcome this challenge and facilitate practical application of theory, a common method is to cover metallic substrates on the sample, which are the surface-enhanced Raman scattering substrates. Professor Surojit Chattopadhyay, graduate student Zih-Ying Chen, and Dr. Akash Gupta of Institute of Biophotonics produced ferric oxide nanoparticles coated with a layer of silver to aggregate ferric oxide nanoparticles by using magnets. They successfully generated the hotspot effect to amplify the signals of Raman spectroscopy and overcome the problem of weak signals of scattered Raman spectroscopy.

This technique of combining laser beams with nanoparticles to surface enhance Raman spectroscopy was confirmed to be able to detect 0.2 ppb natural residue of Hg+ concentration limits in commercial skin whitening cosmetics. This limit is considerably lower than the 1 ppm natural residue regulation implemented in Taiwan. The results demonstrate the enhanced detection sensitivity of the technique and its potential to be applied in detection.

Numerous scientists have invested in research regarding surface-enhanced Raman scattering nanosubstrates, intending to apply the theory in industrial practice. The success of National Yang Ming Chiao Tung University in coating ferric oxide with silver determines a type of nanoparticles that can augment Raman signals and be applied in mercury detection in cosmetics. How to stably regulate the structure of metallic nanoparticles to create substrates that can be used repeatedly is a challenge to future commercialization. The research article was published in Issue 337 of Sensors and Actuators B: Chemical, a renowned publisher of photoelectric sensing techniques, in 2021.


Chinese version: