Few-layer graphene-encapsulated metal nanoparticles for surface-enhanced raman spectroscopy, J. Phys. Chem. C 2014, 118(17), 8993-8998
Few-Layer Graphene-Encapsulated Metal Nanoparticles for Surface-Enhanced Raman Spectroscopy
Youming Liu , Yue Hu , and Jin Zhang *
Center for Nanochemistry, Beijing National Laboratory for Molecular Sciences, Key Laboratory for the Physics and Chemistry of Nanodevices, State Key Laboratory for Structural Chemistry of Unstable and Stable Species, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China
Abstract
Shell-isolated surface-enhanced Raman scattering (shell-isolated SERS), where the isolating shell prevents metal–molecule interactions and improves the stability of the metal nanoparticles, has recently drawn a tremendous amount of attention. However, obtaining an ultrathin, seamless, and chemically stable isolating shell for shell-isolated SERS is still in its infancy. Graphene, with a high optical transparency and chemical inertness, is an ideal candidate to serve as an isolating shell. In the present work, graphene with a controlled number of layers is grown on the surface of metal nanoparticles via chemical vapor deposition, creating graphene-encapsulated metal nanoparticles (M@G, where M = Cu, Ag, and Au) suitable for shell-isolated SERS. Ultraviolet–visible spectroscopy of Ag@G, Cu@G, and their corresponding nanoparticles indicates that graphene can prevent the surface oxidation of Ag and Cu nanoparticles after exposure to ambient air, giving a SERS-active substrate with a long lifetime. The Raman spectra of cobalt phthalocyanine and rhodamine 6G on M@G substrates show that Au@G can dramatically suppress photobleaching and fluorescence of the probe molecules, resulting in an enhanced Raman signal. Hence, M@G is a promising material for applications in chemical and biological detection because of its long-term stability and superior SERS performance.
