A facile hydrazine hydrate reduction of graphene oxide (GO) with surface-passivated by a polyethylene glycol (PEG) method for the fabrication of graphene quantum dots (GQDs) with frequency upconverted emission is presented. And we speculate on the upconversion luminescence due to the anti-Stokes photoluminescence (ASPL), where the δE between the π and σ orbitals is near 1.1 eV.

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Plasmonic MoO3-x@MoO3 nanosheets obtained from surface oxidation of MoO3-x were employed as a SERS substrate for methylene blue detection. They exhibit extraordinary sensitivity comparable to noble metals, which is attributed to shell-isolated electromagnetic enhancing by the plasmonic MoO3-x core and elimination of the photocatalytic degradation by the MoO3 shell.

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