A versatile synthetic method based on solvothermal technique has been developed for the fabrication of TiO(2) nanocrystals with different shapes such as rhombic, truncated rhombic, spherical, dog-bone, truncated and elongated rhombic, and bar. The central features of our approach are the use of water vapor as hydrolysis agent to accelerate the reaction and the use of both oleic acid and oleylamine as two distinct capping surfactants which have different binding strengths to control the growth of the TiO(2) nanoparticles. We also show that the presence of an appropriate amount of water vapor along with the desired oleic acid/oleylamine molar ratio plays a crucial role in controlling size and shape of TiO(2) nanocrystals.

Chemical and physical transformations by milling are attracting enormous interest for their ability to access new materials and clean reactivity, and are central to a number of core industries, from mineral processing to pharmaceutical manufacturing. While continuous mechanical stress during milling is thought to create an environment supporting nonconventional reactivity and exotic intermediates, such speculations have remained without proof. Here we use in situ, real-time powder X-ray diffraction monitoring to discover and capture a metastable, novel-topology intermediate of a mechanochemical transformation. Monitoring the mechanochemical synthesis of an archetypal metal-organic framework ZIF-8 by in situ powder X-ray diffraction reveals unexpected amorphization, and on further milling recrystallization into a non-porous material via a metastable intermediate based on a previously unreported topology, herein named katsenite (kat). The discovery of this phase and topology provides direct evidence that milling transformations can involve short-lived, structurally unusual phases not yet accessed by conventional chemistry.

Hydrogen production via photocatalytic water splitting using sunlight has enormous potential in solving the worldwide energy and environmental crisis. The key challenge in this process is to develop efficient photocatalysts which must satisfy several criteria such as high chemical and photochemical stability, effective charge separation and strong sunlight absorption. The combination of different semiconductors to create composite materials offers a promising way to achieve efficient photocatalysts because doing so can improve the charge separation, light absorption and stability of the photocatalysts. In this review article, we summarized the most recent studies on semiconductor composites for hydrogen production under visible light irradiation. After a general introduction about the photocatalysis phenomenon, typical heterojunctions of widely studied heterogeneous semiconductors, including titanium dioxide, cadmium sulfide and graphitic carbon nitride are discussed in detail.

The catalytic conversion of CO2 into valuable fuels is a compelling solution for tackling the global warming and fuel crisis. Light absorption and charge separation, as well as adsorption/activation of CO2 on the photocatalyst surface, are essential steps for this process. This article reviews the CO2 photoreduction mechanisms and critical aspects that greatly affect the photoreduction efficiency. Additionally, different materials for CO2 photoreduction are provided, including d0 and d10 metal oxides/mixed oxides, sulfides, polymeric materials, and metal phosphides with visible response, metal‐organic frameworks, and layer double hydroxides. Furthermore, various structural engineering strategies and corresponding state‐of‐the‐art photocatalytic systems are reviewed and discussed, such as bandgap engineering, geometrical nanostructure engineering, and heterostructure engineering. Each strategy has advantages and disadvantages, requiring further adjustment to further improve the photocatalytic performance of the photocatalyst. Based on this review, it is greatly expected that efficiently artificial systems and the breakthrough technologies for CO2 reduction will be successfully developed in the future to solve the energy shortage as well as the environmental problem.

A new approach for the synthesis of uniform metal-organic framework (MOF) nanocrystals with controlled sizes and aspect ratios has been developed using simultaneously the non-ionic triblock co-polymer F127 and acetic acid as stabilizing and deprotonating agents, respectively. The alkylene oxide segments of the triblock co-polymer can coordinate with metal ions and stabilize MOF nuclei in the early stage of the formation of MOF nanocrystals. Acetic acid can control the deprotonation of carboxylic linkers during the synthesis and, thus, enables the control of the rate of nucleation, leading to the tailoring of the size and aspect ratio (length/width) of nanocrystals. Fe-MIL-88B-NH(2), as an iron-based MOF crystal, was selected as a typical example to illustrate our approach. The results reveal that this approach is used for not only the synthesis of uniform nanocrystals but also the control of the size and aspect ratio of the materials. The size and aspect ratio of nanocrystals increase with an increase in the concentration of acetic acid in the synthetic mixture. The non-ionic triblock co-polymer F127 and acetic acid can be easily removed from the Fe-MIL-88B-NH(2) nanocrystal products by washing with ethanol, and thus, their amine groups are available for practical applications. The approach is expected to synthesize various nanosized carboxylate-based MOF members, such as MIL-53, MIL-89, MIL-100, and MIL-101.

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An Au/TiO(2) nanostructure was constructed to obtain a highly efficient visible-light-driven photocatalyst. The design was based on a three-dimensional ordered assembly of thin-shell Au/TiO(2) hollow nanospheres (Au/TiO(2)-3 DHNSs). The designed photocatalysts exhibit not only a very high surface area but also photonic behavior and multiple light scattering, which significantly enhances visible-light absorption. Thus Au/TiO(2)-3 DHNSs exhibit a visible-light-driven photocatalytic activity that is several times higher than conventional Au/TiO(2) nanopowders.

Monodisperse samaria nanospheres and nanorods have been synthesized from commercial bulk Sm2O3 powders and various capping long-chain alkyl acids (e.g., oleic acid, myristic acid, decanoic acid). The synthesized materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), Fourier transform IR, thermogravimetric analysis, and N2 adsorption/desorption isotherms was employed to characterize these materials. The results revealed that the synthesis of nanorods consists of two steps of growth: (i) the nanoparticles were formed at relatively low temperature (120−140 °C) by Ostwald ripening and (ii) were followed by oriented attachment of these nanoparticles at higher temperature (160−200 °C) to produce the nanorods (average size of 7 nm × 160 nm). Furthermore, the width of nanorods can be controlled by the length of capping alkyl chain agents; on the basis of the experimental results, it seems that a longer alkyl chain agent leads to thinner nanorods; however, the length of nanorods remains unchanged. For the whole process, the possible Ostwald ripening and oriented attachment mechanisms were also discussed. The XPS results for the calcined nanorods sample shows the presence of two oxidation states, Sm3+/Sm2+ (it is found to be 40% Sm2+), and three components by deconvolution of O 1s peak indicating the defected structure. The surface chemical composition is found to be Sm2O3−x (x = 1.8). We believe that this synthetic method is simple, highly reproducible, inexpensive, and applicable for large-scale production.