Carbon-based dots (CDs) are a novel class of luminescent carbon nanomaterials that have attracted much attention as promising alternatives for cadmium-based quantum dots and fluorescent organic dyes. Although different strategies have been proposed to produce CDs with intense and tuneable one-photon excited fluorescence (OPEF), the case of analogous two-photon excited fluorescence (TPEF) has not been fully explored yet. By varying the synthesis conditions, we produced three types of phloroglucinol-based carbon nanodots (PG CNDs). Their remarkable OPEF and TPEF properties can be tuned by (Ia) the conjugated aromatic domains and (Ib) the content of oxygenous moieties. In addition, the emission colour of the PG CNDs is strongly responsive to (II) the hydrogen-bonding network, enabling colour-switching while maintaining excellent fluorescence yields (both OPEF and TPEF). These three factors were evaluated for their suitability for the tuning of the emission colour. Our studies point out the advantages of the tuneable PG CNDs to be used in optoelectronics and biological application domains.

Monodispersed hollow periodic mesoporous organosilica nanoparticles (HPMO-NPs) with a controlled core cavity and a periodic mesoporous organosilica (PMO) shell are successfully synthesized using a dual templating approach. The PMO shell synthesized by the sol–gel route exhibits a hybrid organic-inorganic framework based on phenylene bridges. The HPMO spherical nanoparticles with a diameter above 500 nm were characterized using a multiscale approach through TEM, BET, SAXS, and FT-IR. They are shown to offer an open periodic mesoporosity, a hollow cavity with a size tailored by thediameter of the core template, and finally, a high surface area (833 m 2 · g−1 ). In addition, we demonstrate that, through the same approach, the size of these hollow spherical nanoparticles can be tuned. Indeed, sub-50-nm hollow nanoparticles with mesoporous shells have also been obtained. The differences observed in the textural properties of these two sizes of hollow mesoporous nano-objects are discussed.

In this article, we conduct comparative studies on the optical properties of metallic carbon nanotubes. First, we compare the complex dielectric constant predicted by an analytical model, the linear surface conductivity model, with ab initio calculations based on density functional theory. We highlight the similarities and differences between these two models, with the major discrepancy being the significantly different behavior of the plasma frequency with respect to the carbon nanotube diameter. In the second step, we compare the predictions of these models with experimental measurements of the dielectric function. We demonstrate that the screened plasma frequency serves as a reliable quantifier for distinguishing between the two models. In conclusion, we find that the ab initio calculations more accurately describe the optical properties of metallic carbon nanotubes compared with the commonly used linear surface conductivity model.

Nonlinear V-I characteristics of particulate composite prepared from dispersion of silicon carbide in a siloxane elastomer have been measured as a function of filler concentration up to the maximum allowable of about 32 vol.%. Two critical concentrations (percolation thresholds) are obtained at volume fractions of about 17 and 24 vol.% for low and high electric fields. These values are consistent with the critical concentrations predicted by the theory: 14 and 31 vol.% respectively and may come from edge and face contacts between SiC semi-conducting particles.

We report the existence in NaLa(SO 4 ) 2 ·H 2 O of a displacive phase transition under 200 K from the nonpolar P 3 1 21 to the polar P 3 1 space group.