Three-dimensional MoS2-NS@Au-NPs hybrids as SERS sensor for quantitative and ultrasensitive detection of melamine in milk

MoS 2 , a novel inorganic graphene analogues with typical two-dimensional structure, has attracted increasing interest in various fields. MoS 2 -based hybrid plasmonic structures have been extensively investigated as higher quality surface enhanced Raman scattering (SERS) substrates. Herein, we have designed a three-dimensional (3D) MoS 2 nanospheres (NSs) based hybrid nanostructure as SERS sensor by decorating Au nanoparticles (NPs) on the surface of 3D MoS 2 -NSs (3D MoS 2 -NS@Au-NPs). 3D MoS 2 -NSs acts as (a) a stable scaffold for Au NPs decoration via microwave-irradiation hydrothermal process, (b) a chemical mechanism source for Raman enhancement, and (c) a 3D spatial structure for generation of more effective hot spots due to Au coupling effect and supply larger surface area for adsorbing probe molecules. The 3D MoS 2 -NS@Au-NPs hybrid structure exhibits 56-fold improvement on enhancement factor compared to two-dimensional MoS 2 -NST@Au-NPs hybrid structures. SERS performance was easily and effectively optimized with the tuning of the density and sizes of Au NPs. The optimized 3D MoS 2 -NS@Au-NPs was applied as SERS sensor for melamine detection in milk. Quantitative detection was realized in the range of 1 ppb–10 ppm with a linear coefficient of .997. Excellent sensitivity of 1 ppb and uniformity of 10.12% relative standard deviation was achieved, which could meet the demand for melamine detection as prescribed by the U.S. Food and Drug Administration.