35 lap 431 220

Raman spectroscopy has been used as a tool to identify CeO₂, to provide clues on the degree of nano-structuring [44 (link),45 (link),46 (link),47 (link),48 (link)] and to detect the presence of oxygen defects and reduced Ce³⁺ ions [49 (link),50 (link)]. Additionally, the organic functionalization to CeO₂ can be followed via Raman spectroscopy [46 (link)]. A confocal Raman microscope (Jasco, NRS-3100, Lecco, Italy) was used to obtain Raman spectra. The 514 nm line of an air-cooled Ar⁺ laser (Melles Griot, 35 LAP 431–220, Carlsbad, CA, USA) was injected into an integrated Olympus microscope and focused to a spot size of approximately 2 µm by using a 100× objective, with a final 2 mW laser power at the sample. A holographic notch filter was used to reject the excitation laser line. Raman scattering was collected by using a Peltier-cooled 1024 × 128 pixel CCD photon detector (Andor DY401BVI, Andor technology oxford instruments, Belfast, UK). For most systems, it took 60 s to collect a complete data set. Measurements were at least triplicated for scope of reproducibility.

A confocal Raman microscope (Jasco, NRS-3100) was used to obtain Raman and photoluminescence spectra. The 514 nm line of an air-cooled Ar+ laser (Melles Griot, 35 LAP431 220), was injected into an integrated Olympus microscope and focused to a spot diameter of approximately 3 μm by a 20x objective with a final 4 mW power at the sample. A holographic notch filter was used to reject the excitation laser line. The Raman backscattering was collected using a 0.1 mm slit and a diffraction lattice of 1200 grooves/mm, corresponding to an average spectral resolution of 8 cm^–1. Solutions were left evaporating on Si substrates, and it took 60 s to collect a complete data set by a Peltier-cooled 1024 × 128 pixel CCD photon detector (Andor DU401BVI). Raman micro-spectroscopic measurements of both GO and MoS₂ samples were at least triplicated for scope of reproducibility and as a check of spatial homogeneity of the samples. Wavelength calibration was performed by using cyclohexane as a standard.