Evolution of a high local strain in rolling up MoS₂sheets 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 [Formula: see text] and [Formula: see text] modes. From the Grüneisen parameter γ and the shear deformation potential β, we obtained peak shifts of ∼4.9 cm^-1/% at [Formula: see text] and ∼1.1 cm^-1/% strain at [Formula: see text] for free-standing MoS₂. According to the obtained relationship of the Raman shift and the induced uniaxial tensile strain, the [Formula: see text] and [Formula: see text] 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.