Metal-organic framework-based SERS chips enable in situ and sensitive detection of dissolved hydrogen sulfide in...

Hydrogen sulfide (H₂S) in natural water plays an important role in carbon and sulfur cycles in biosphere. Current detection protocol is complicated, which need to "bring back water" to lab followed by gas chromatograph analysis. In situ, field detection is still challenging. Herein, a portable, sensitive surface enhanced Raman scattering (SERS) chip was proposed for in situ H₂S sampling and SERS signal stabilizing, enabling a "bring back chip" manner for lab analysis. The SERS chip was composed of single core-shell gold nanorod-ZIF-8 framework (Au NR@ZIF-8) nanoparticle. Relying on headspace adsorption, evaporated H₂S was enriched in the ZIF-8 shell and then reacted with Au NR, resulting in the weakening of the Au-Br bond Raman peak (175 cm^-1) and the appearance of the Au-S bond Raman peak (273 cm^-1). The SERS signal reached equilibrium in 10 min. The detection range of H₂S was 0.1-2000 μg/L and limit of detection was 0.098 μg/L. SERS signal was not interfered by normal volatile gases. Moreover, SERS signal of a reacted chip was stable at an ambient condition, allowing for in situ sampling and bring-back detection. The applicability of the chip was verified by dynamic H₂S monitoring during artificial black-odor water evolution, and in-field quantitative analysis of H₂S content in river water and sediment. Finally, the chip was sealed in a waterproof breathable membrane device, which realized the detection of vertical profiles of H₂S in the river. This work provided a promising tool for field analysis of H₂S in natural environments.