MXenes induce epitaxial growth of size-controlled noble nanometals: a case study for surface enhanced Raman scattering (SERS)

Noble nanometals are of significance in both scientific interest and technological applications, which are usually obtained by conventional wet-chemical synthesis. Organic surfactants are always used in the synthesis to prevent unexpected overgrowth and aggregation of noble nanometals. However, the surfactants are hard to remove and may interfere with plasmonic and catalytic studies, remaining surfactant-free synthesis of noble nanometals a challenge. Herein, we report an approach to epitaxial growth of size-controlled noble nanometals on MXenes. As piloted by density functional theory calculations, along with work function experimental determination, kinetic and spectroscopic studies, epitaxial growth of noble nanometals is initiated via a mechanism that involves an in situ redox reaction. In the redox, MXenes as two-dimensional solid reductants whose work functions are compatible with the reduction potentials of noble metal cations, enable spontaneous donation of electrons from the MXenes to noble metal cations and reduce the cations into nanoscale metallic metals on the outmost surface of MXenes. Neither surfactants nor external reductants are used during the whole synthesis process, which addresses a long-standing interference issue of surfactant and external reductant in the conventional wet-chemical synthesis. Moreover, the MXenes induced noble nanometals are size-controlled. Impressively, noble nanometals firmly anchored on MXenes exhibit excellent performance towards surface enhanced Raman scattering. Our developed strategy will promote the nanostructure-controlled synthesis of noble nanometals, offering new opportunities to further improve advanced functional properties towards practical applications.