ZnO materials with a range of different morphologies have been synthesized via a simple solvothermal method with different solvents. Zinc acetylacetonate was used as the zinc source in such solvothermal syntheses for the first time. XRD data showed that single-phase ZnO with the wurtzite crystal structure was obtained for all the solvents used. FE-SEM imaging showed that ZnO with cauliflower-like, truncated hexagonal conical, tubular and rodlike, hourglass-like, nanorods, and spherical shapes were produced when THF, decane, water, toluene, ethanol, and acetone were used as the solvent, respectively. The TEM data showed that the crystalline ZnO had different growth habits in the different solvents. The optical properties of the as-prepared ZnO materials were investigated by UV-vis absorption and room temperature photoluminescence. Photodegradation of phenol was used as a model reaction to test the photocatalytic activity of the ZnO samples. ZnO samples with different morphologies and crystal growth habits exhibited different activities to phenol degradation. The ZnO material prepared using THF as the solvent showed a nine-times enhancement of the kinetic rate constants over commercial ZnO (0.1496 min -1 vs 0.0182 min -1 ). The influence of the solvents on the morphology of ZnO samples and the effect of the morphologies on the photocatalytic activity are discussed.

The treatment of CdSe nanocrystals (NCs) in a 3-amino-1-propanol (APOL)/water (v/v = 10:1) mixture at 80 degrees C in the presence of O(2) causes them to undergo a slow chemical etching process, as evidenced by spectroscopic and structural investigations. Instead of the continuous blue shift expected from a gradual decrease in NC dimensions, a bottleneck behavior was observed with distinct plateaus in the peak position of photoluminescence (PL) and corresponding maxima in PL quantum yield (i.e., 34 +/-7%). It is presently argued that such etching behavior is a result of two competitive processes taking place on the surface of these CdSe NCs: (i) oxidation of the exposed Se-sites to acidic SeO(x)() entities, which are readily solubilized in the basic APOL/H(2)O mixture, and (ii) coordination of the underlying Cd-sites with both amines and hydroxyl moieties to temporally impede NC dissolution. This is consistent with the HRTEM results, which suggest that the etched NCs adopt pyramidal morphologies with Cd-terminated facets (i.e., (0001) bases and either {011} or {21} sides) and account for the apparent resistance to etching at the plateau regions.

Porous solids, such as zeolites and other molecular sieves, contain intracrystallite/framework cavities and channels that produce microporous (pore diameter, D < 2 nm), mesoporous (2 nm < D < 50 nm), and macroporous (D > 50 nm) structures, and have demonstrated excellent potential as materials for use in many separation and catalytic processes.[1] The pore sizes of these porous materials (especially the micropore sizes, which are close to molecular dimensions) may play a critical role in controlling separation and catalytic selectivity due to their shape and size selectivity. The production of materials with different microporosities has always been challenging. Natural and synthetic tunnel-structured manganese oxide octahedral molecular sieves (OMSs) make up a promising group of functional porous materials. They can exhibit various nanometer-scale tunnel sizes from 2.3 2.3 to 4.6 11.5 , which correspond to different micropore openings. As such, they constitute excellent model systems for studying the synthesis of materials with controlled microporosities. Moreover, the potential applications for synthetic manganese oxide OMS materials can be expanded by molecular modification or decoration of the tunnel structures.[2] There have been several attempts to synthesize manganese oxide OMSs with the same tunnel structures as those found in natural manganese oxides, or to create materials with new tunnel structures.[3±7]However, there has been very little work reported on the direct control of tunnel sizes. In this communication, we report the successful synthesis of manganese oxide OMS materials with controlled nanometer-scale tunnel sizes by controlling the pH of the hydrothermal transformation of layered manganese oxide precursors. Hydrothermal transformation of layered manganese oxide materials is one of the most effective methods of obtaining tunnel-structured manganese oxides. Due to the mixed-valent manganese framework, usually (+2, +3, and +4) or (+3 and +4), a small number of guest cations are usually required for charge balance in most layer-and tunnel-structured manganese oxides. These guest cations usually reside between the layers or inside the tunnels.[3±7] When layered manganese oxides are transformed into tunnel structures, the interlayer cations remain inside the tunnels. Therefore, the types and sizes of the guest cations in these layered manganese oxides might play critical roles as structure directors in templating different tunnel sizes during synthesis of tunnel structures. Since many cations are in hydrated form under aqueous/hydrothermal conditions, the template effect may actually result from the size of the hydrated cations rather than from that of the isolated cations. This is particularly intriguing since many cations can adopt different hydration states, and thus the sizes of the hydrated cations can be different. The corollary of this is that, if the sizes of hydrated cations can be controlled by varying the extent of hydration, it may be possible to synthesize materials with controlled tu...

Novel three‐dimensional (3D) hierarchical nanoarchitectures of ϵ‐MnO2 have been synthesized by a simple chemical route without the addition of any surfactants or organic templates. The self‐organized crystals consist of a major ϵ‐MnO2 dipyramidal single crystal axis and six secondary branches, which are arrays of single‐crystal ϵ‐MnO2 nanobelts. The growth directions of the nanobelts are perpendicular to the central dipyramidal axis, which shows sixfold symmetry. The shape of the ϵ‐MnO2 assembly can be controlled by the reaction temperature. The morphology of ϵ‐MnO2 changes from a six‐branched star‐like shape to a hexagonal dipyramidal morphology when the temperature is increased from 160 to 180 °C. A possible growth mechanism is proposed. The synthesized ϵ‐MnO2 shows both semiconducting and magnetic properties. These materials exhibit ferromagnetic behavior below 25 K and paramagnetic behavior above 25 K. The ϵ‐MnO2 system may have potential applications in areas such as fabrication of nanoscale spintronic materials, catalysis, and sensors.

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