Doped and undoped ZnO nanorods (ZnO-NRs) are highly investigated materials for their numerous applications in catalysis, in optoelectronics, and in analytical chemistry. Seeded growth using well-defined ZnO nanomaterials represents a useful approach to control the size and morphology of undoped ZnO-NRs; however, the possibility to use such a strategy to produce size-defined doped ZnO-NRs was not previously investigated. In this work, we show that it is possible to prepare aluminum- and cerium-doped ZnO-NRs with well-defined length and diameter by a controlled hydrolytic seeded growth. The synthesized materials were characterized by various analytical techniques such as XPS, EDS, SEM/EDS, XRD, Raman, UV–vis, and photoluminescence (PL), which evidenced the correlation between the loading of dopant, the morphology of the nanorods, their optoelectronic properties, and the amount and nature of lattice defects. Given its smaller ionic radius, the doping with aluminum was more efficient than with cerium. Indeed, for the latter element, dopant concentrations above a certain threshold led to phase separation and coprecipitation of ceria particles during synthesis. In addition, the effect of our preparation strategy on the photocatalytic activity of doped and undoped ZnO-NRs was investigated by studying the photodegradation of methyl orange (MO) under UV light. The study revealed that aluminum-doped ZnO-NRs generally performed better than cerium-doped ZnO-NRs and that moderate aluminum concentrations could lead to an improvement of the photocatalytic performance compared to undoped ZnO-NRs, an observation that could be related to the occurrence and abundance of specific defect sites in the lattice.

No abstract

Glycerol carbonate (GC) has emerged as an attractive synthetic target due to various promising technological applications. Among several viable strategies to produce GC from CO2 and glycerol and its derivatives, the cycloaddition of CO2 to glycidol represents an atom‐economic an efficient strategy that can proceed via a halide‐free manifold through a proton‐shuttling mechanism. Here, it was shown that the synthesis of GC can be promoted by bio‐based and readily available organic salts leading to quantitative GC formation under atmospheric CO2 pressure and moderate temperatures. Comparative and mechanistic experiments using sodium citrate as the most efficient catalyst highlighted the role of both hydrogen bond donor and weakly basic sites in the organic salt towards GC formation. The citrate salt was also used as a catalyst for the conversion of other epoxy alcohols. Importantly, the discovery that homogeneous organic salts catalyze the target reaction inspired us to use metal alginates as heterogeneous and recoverable bio‐based catalysts for the same process.

Nanostructured zinc oxide (ZnO) is an important material that finds application in numerous fields spanning from catalysis to optoelectronics. Rodlike ZnO nanostructures are of particular interest, given their well-defined crystalline orientation and high surface area to volume ratio. In this work we show how the choice of precursor seeds determines the final morphology of in-suspension-grown ZnO nanostructures and can be used to tune their length and diameter. Free-standing ZnO nanorods were grown by controlled hydrolysis of zinc nitrate at 90 °C using hexamethylenetetramine as a source of ammonia which, in turn, provided OH anions. The ZnO growth was directed toward the formation of pencil-shaped nanorods (diameter ∼124 nm) using aqueous suspensions of ZnO nanopyramids (prepared by a nonhydrolytic sol–gel method), whereas their length depended on the concentration of the initial precursor. To prove the importance of the size of seeds and their morphology, ZnO nanotiles, nanoparticles, and nanocrystals were also used to seed the growth of ZnO nanostructures, giving nanorods of different lengths and diameters. The morphology of the nanostructures was investigated by SEM, TEM, and powder X-ray diffraction.

Three-dimensional hierarchical mesoporous structures of titanium dioxide (3D-HPT) were synthesized by self-assembly emulsion polymerization. Polymethyl methacrylate (PMMA) and pluronic 123 (P123) were used as the soft templates and co-templates for assisting the formation of hierarchical 3D porous structures. The TiO2 crystal structure, morphology, and Remazol red dye degradation were investigated. The 3D-HPT and normal three-dimensional titanium dioxide (3D-T) presented the good connection of the nanoparticle-linked honeycomb within the form of anatase. The 3D-HPT structure showed greatly enhanced adsorption of Remazol dye, and facilitated the efficient photocatalytic breakdown of the dye. Surprisingly, 3D-HPT can adsorb approximately 40% of 24 ppm Remazol dye in the dark, which is superior to 3D-T and the commercial anatase at the same condition (approx. 5%). Moreover, 3D-HPT can completely decolorize Remazol dye within just 20 min, which is more than three folds faster than the commercial anatase, making it one of the most active photocatalysts that have been reported for degradation of Remazol dye. The superior photocatalytic performance is attributed to the higher specific surface area, amplified light-harvesting efficiency, and enhanced adsorption capacity into the hierarchical 3D inverse opal structure compared to the commercial anatase TiO2.