No abstract

Chemical enhancement is an important mechanism in surface-enhanced Raman spectroscopy. It is found that mildly reduced graphene oxide (MR-GO) nanosheets can significantly increase the chemical enhancement of the main peaks by up to 1 order of magnitude for adsorbed Rhodamine B (RhB) molecules, in comparison with the mechanically exfoliated graphene. The observed enhancement factors can be as large as ∼10(3) and show clear dependence on the reduction time of graphene oxide, indicating that the chemical enhancement can be steadily controlled by specific chemical groups. With the help of X-ray photoelectron spectra, these chemical species are identified and the origin of the observed large chemical enhancement can thus be revealed. It is shown that the highly electronegative oxygen species, which can introduce a strong local electric field on the adsorbed molecules, are responsible for the large enhancement. In contrast, the local defects generated by the chemical reduction show no positive correlation with the enhancement. Most importantly, the dramatically enhanced Raman spectra of RhB molecules on MR-GO nanosheets reproduce all important spectral fingerprints of the molecule with a negligible frequency shift. Such a unique noninvasive feature, along with the other intrinsic advantages, such as low cost, light weight, easy availability, and flexibility, makes the MR-GO nanosheets very attractive to a variety of practical applications.

No abstract

No abstract

No abstract

We propose a new approach to fabricate the graphene nanomesh through the local catalytic hydrogenation of carbon by Cu nanoparticles. It allows to tune the size and density of the holes in the nanomesh as well as the total edge length of the holes through the control of the thickness of the Cu film. The upshift of both G and 2D peaks in Raman spectra of the graphene nanomeshes indicates that the nanomesh is spontaneously p-type doped. Moreover, the split of G peak reveals that the doping is localized near the edge region of the hole in the nanomesh. Importantly, the nanomesh shows improved chemical enhancement for Raman spectra of absorbed RhB molecules as compared to the graphene. The edges in the nanomesh can enhance Raman spectroscopy via increasing both the local charge transfer and the ability to absorb RhB molecules. The results show that the graphene nanomesh has a great potential for the rapid and sensitive detection for the environmental monitoring and food security.

No abstract

No abstract