TiO2 decorated flower-like 2H-MoS2 heterostructure as stable noble-free substrate for sensitive and selective surface-enhanced Raman scattering analysis of Hg2+

Developing stable, noble-free SERS substrates with high selectivity and reproducibility remains a major analytical challenge. Herein, a novel noble-free substrate of TiO 2 decorated flower-like 2H-MoS 2 (2H-MoS 2 /TiO 2 ) heterostructure was fabricated for sensitive and selective analysis of mercury ion (Hg 2+ ) in environmental water, demonstrating high potential for monitoring real water samples following standard pretreatment. The 2H-MoS 2 /TiO 2 heterostructure can be simply prepared by two-step hydrothermal method, as well as exhibiting high SERS activity with low minimum detectable concentration (1.0 μg/L) and promising enhancement factor (about 10 5 ) for Rhodamine 6G and derivatives. The good Raman enhancement attributes to multiple synergistic effect of high adsorbability of 2H-MoS 2 /TiO 2 , molecular resonance and significant charge transfer effect, which was investigated by experiments and density functional theory simulations. The indirect analytical method for Hg 2+ based on good SERS activity and specificity of R-NH 2 for Hg 2+ was established. The low limit of detection (0.16 μg/L) with linearity of 0.5 μg/L–1.0 mg/L for Hg 2+ can be obtained. The recoveries of Hg 2+ in environmental water is 82.3–106.7 % with low relative standard deviations of 2.1–6.3 %. More than just a high-performance substrate, this work provides a general design strategy for constructing stable and practical noble-free heterojunctions, significantly advancing the development of reliable SERS methodologies for on-site environmental analysis.