Evolution of a high local strain in rolling up MoS2 sheets decorated with Ag and Au nanoparticles for surface-enhanced Raman scattering

Abstract

We report that a high local strain was obtained for multilayer MoS2 nanoscrolls decorated with noble nanoparticles (Ag and Au NPs) using a rolling process beyond breaking or slipping of MoS2. The local strain was estimated through the bending strain in the nanoscrolls and the extent of coverage of Ag and Au NPs decorated on MoS2, exhibiting magnified surface-enhanced Raman scattering. TEM images showed that the MoS2–Ag and MoS2–Au nanoscrolls have a tube-like morphology decorated with NPs on the inner and outer sides of the MoS2 nanoscrolls. In the Raman spectra, we confirmed the red shift and broadness of the FWHM for nanoscrolls in the eigenvectors of the and modes. From the Grüneisen parameter γ and the shear deformation potential β, we obtained peak shifts of ∼4.9 cm−1/% at and ∼1.1 cm−1/% strain at for free-standing MoS2. According to the obtained relationship of the Raman shift and the induced uniaxial tensile strain, the and peaks shifted upwards to around −12.8 cm−1 and −2.9 cm−1, respectively, and can be converted to an induced uniaxial tensile strain of about 2.6% for MoS2–Ag nanoscrolls.