In this work we demonstrate the coupling of the photothermal effects of gold nanostructures of controlled size and shape with graphene oxide nanosheets dispersed in water. The enhanced photothermal effects can be tuned by controlling the shape and size of the gold nanostructures, which result in a remarkable increase in the heating efficiency of the laser-induced size reduction of gold nanostructures. The Raman spectra of the Au-graphene nanosheets provide direct evidence for the presence of more structural defects in the graphene lattice induced by laser irradiation of graphene oxide nanosheets in the presence of Au nanostructures. The large surface areas of the laser-reduced graphene oxide nanosheets with multiple defect sites and vacancies provide efficient nucleation sites for the ultrasmall gold nanoparticles with diameters of 2-4 nm to be anchored to the graphene surface. This defect filling mechanism decreases the mobility of the ultrasmall gold nanoparticles and, thus, stabilizes the particles against the Ostwald ripening process, which leads to a broad size distribution of the laser-size-reduced gold nanoparticles. The Au nanostructures/graphene oxide solutions and the ultrasmall gold-graphene nanocomposites are proposed as promising materials for photothermal therapy and for the efficient conversion of solar energy into usable heat for a variety of thermal, thermochemical, and thermomechanical applications.

We have developed a facile, fast, and scalable microwave irradiation method for the synthesis of graphene and CdSe nanocrystals of controlled size, shape, and crystalline structure dispersed on graphene sheets. The reduction of graphite oxide into graphene takes place in DMSO within 2 min of microwave irradiation as opposed to 12 h of conventional thermal heating at 180 °C. The method allows the simultaneous reduction of graphite oxide and the nucleation and growth of CdSe nanocrystals using a variety of capping agents. Cubic and hexagonal CdSe nanocrystals with average sizes of 2-4 and 5-7 nm, respectively, have been prepared by the proper choice of the capping agent within a few minutes of microwave irradiation. Highquality nearly monodisperse CdSe nanocrystals have been supported on graphene with no evidence of aggregation. Direct evidence is presented for the efficient quenching of photoluminescence from the CdSe nanocrystals by graphene. The results provide a new approach for exploring the size-tunable optical properties of CdSe nanocrystals supported on graphene which could have important implications for energy conversion applications such as photovoltaic cells where CdSe quantum dots, the light-harvesting material, are supported on the highly conducting flexible graphene electrodes.

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CO elimination through oxidation over highly active and cost-effective catalysts is a way forward for many processes of industrial and environmental importance. In this study, doped CeO 2 with transition metals (TM = Cu, Co, Mn, Fe, Ni, Zr, and Zn) at a level of 20 at. % was tested for CO oxidation. The oxides were prepared using microwave-assisted sol–gel synthesis to improve catalyst’s performance for the reaction of interest. The effect of heteroatoms on the physicochemical properties (structure, morphology, porosity, and reducibility) of the binary oxides M–Ce–O was meticulously investigated and correlated to their CO oxidation activity. It was found that the catalytic activity (per gram basis or TOF, s –1 ) follows the order Cu–Ce–O > Ce–Co–O > Ni–Ce–O > Mn–Ce–O > Fe–Ce–O > Ce–Zn–O > CeO 2 . Participation of mobile lattice oxygen species in the CO/O 2 reaction does occur, the extent of which is heteroatom-dependent. For that, state-of-the-art transient isotopic 18 O-labeled experiments involving 16 O/ 18 O exchange followed by step-gas CO/Ar or CO/O 2 /Ar switches were used to quantify the contribution of lattice oxygen to the reaction. SSITKA-DRIFTS studies probed the formation of carbonates while validating the Mars–van Krevelen (MvK) mechanism. Scanning transmission electron microscopy-high-angle annular dark field imaging coupled with energy-dispersive spectroscopy proved that the elemental composition of dopants in the individual nanoparticle of ceria is less than their composition at a larger scale, allowing the assessment of the doping efficacy. Despite the similar structural features of the catalysts, a clear difference in the O lattice mobility was also found as well as its participation (as expressed with the α descriptor) in the reaction, following the order α Cu > α Co > α Mn > α Zn . Kinetic studies showed that it is rather the pre-exponential (entropic) factor and not the lowering of activation energy that justifies the order of activity of the solids. DFT calculations showed that the adsorption of CO on the Cu-doped CeO 2 surface is more favorable (−16.63 eV), followed by Co, Mn, Zn (−14.46, −4.90, and −4.24 eV, respectively), and pure CeO 2 (−0.63 eV). Also, copper compensates almost three times more charge (0.37 e − ) compared to Co and Mn, ca. 0.13 e − and 0.10 e − , respectively, corroborating for its tendency to be reduced. Surface analysis (X-ray photoelectron spectroscopy), apart from the oxidation state of the elements, revealed a heteroatom–ceria surface interaction (O a species) of different extents and of d...