Scientists have newly developed high-pressure resistant solid-state nanomaterials

Schematic diagram of the preparation process of SERS substrate (a); and SERS enhancement mechanism (b) Photo courtesy of Ocean

SEM image of the SERS substrate (the distribution of silver nanoparticles on the surface resembles the back pattern of the seven-star ladybug) Image courtesy of the ocean

Recently, the Institute of Oceanography of the Chinese Academy of Sciences and the Institute of Physics of the Chinese Academy of Sciences cooperated to prepare a surface-enhanced Raman scattering (SERS) substrate of silver nanoparticles similar to the spot-like Ladybird of the Seven-Star Ladybug. The substrate achieves the detection of 10-6 M ethanolamine phosphate molecules under simulated high pressure, which has good sensitivity and pressure resistance, which provides a new means for the in-situ detection of low concentrations of microbial metabolites in the deep sea in the future. The international academic journal “Surface and Interface” recently reported this latest result online.

It is understood that due to the extremely complex deep-sea environment, deep-sea in situ exploration has been facing great challenges. In its previous work, the research group of the Institute of Oceanography has successfully achieved various in situ detection by using the self-developed deep-sea Raman probe system. In situ detection subjects include high temperature hydrothermal vent fluid temperatures up to 450°C, such as CO2, composition of SO42-/HSO4- and H2, minerals and physicochemical parameters of overlying biome.

However, the research group found that there is still a lack of relevant detection methods for some macromolecules in situ in the deep sea, especially the relevant metabolites and intermediates of various microorganisms living in extreme environments of the deep sea. At the same time, there is no in situ detection method for extracellular metabolites of deep-sea microorganisms in the world, and traditional detection methods, such as color measurement, liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR), cannot detect multiple components at the same time. Moreover, traditional detection methods are time-consuming, costly, and insensitive. The detection limit of laser Raman can only reach the millimolar level, which seriously hinders the detection of low-concentration deep-sea microbial metabolites or intermediates by laser Raman technology. Therefore, in situ detection of deep-sea extracellular metabolites is very difficult and faces great challenges.

Surface enhanced Raman scattering (SERS) mainly comes from the enhancement of local electromagnetic fields near precious metal (silver, gold) nanoparticles, so it has the ability to detect trace molecules with ultra-sensitive and rapid detection limits, and the detection limit can reach the nanomolar or even picomolar level. However, most of the currently widely used SERS substrates are liquid sol materials, and solid SERS substrates also have the disadvantages of easy oxidation and easy falling off under high pressure, and cannot be applied in deep sea in-situ detection.

In view of this, the research team used the high-temperature annealing process to heat treat the silver-coated quartz to successfully prepare a silver nanoparticle SERS substrate material similar to the spot-like Ladybird spot, showing good crystal orientation, and achieving the detection of 10-6 M phosphoethanolamine at 11 MPa. The developed SERS substrate material has strong oxidation resistance and can withstand the deep-sea high-pressure environment, ensuring the success of the 2022 in-situ exploration voyage of the cold seep ecosystem in the South China Sea, which not only meets the needs of in-situ exploration of the deep sea, but also suitable for the detection of extreme industrial environments.

The research has been jointly funded by the National Natural Science Foundation of China, the Class A Strategic Pilot Project of the Chinese Academy of Sciences, the Key Deployment Project of the Ocean Science Research Center of the Chinese Academy of Sciences, the Taishan Young Scholars Program and other projects, and the support of the Institute of Physics of the Chinese Academy of Sciences Collaborative Extreme Conditions User Facility (SECUF). (Source: China Science News, Liao Yang, Li Hezhao)

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