The high-temperature (over 1020 degrees C) polymorph of ZnS, wurtzite ZnS, has been successfully prepared through a low-temperature (180 degrees C) hydrothermal synthesis route in the presence of ethylenediamine (en). The effects of en concentrations, reactant concentrations, reaction temperatures, and reaction times on crystal structures and shapes of ZnS have been investigated. We have demonstrated that the wurtzite ZnS showing rodlike morphology can be kinetically stabilized in the presence of en, especially at a high reactant concentration under appropriate hydrothermal conditions. Besides phase evolution of ZnS from hexagonal to cubic, morphological transformation from nanorods to nanograins has also been observed in the present investigation. Nanograins of phase-pure cubic ZnS, the thermodynamically stable polymorph, are easily prepared, and no hexagonal ZnS nanorods are detected in "pure" water, i.e., in the absence of en molecules. The above investigations indicate that the controlled fabrication of wurtzite ZnS nanorods is due to a mediated generation of the lamellar phase, ZnS.0.5en, a covalent organic-inorganic network based on ZnS slabs, and to its subsequent thermolysis in aqueous solution. The controlled growth of wurtzite ZnS nanorods and sphalerite ZnS nanograins provides us an opportunity to structurally modulate physical properties. These wurtzite ZnS nanorods display narrower and stronger blue emission than sphalerite ZnS nanograins.

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A uranyl–europium heterobimetallic compound, (TEA)3[(UO2)6Eu­(H2O)4(PPA)6] (H3PPA = phosphonoacetic acid, TEA = tetraethylammonium cation), was synthesized under mild hydrothermal conditions. The emission spectrum contains characteristic electronic transition features of both Eu3+ and UO2 2+, while the peak intensity of Eu3+ is notably higher than that of UO2 2+. This is primarily attributed to the energy transfer from uranyl to europium in the structure. Significantly, a positive correlation between the Eu3+ peak intensity at 621 nm and the D2O content can be established in the aqueous system, while the uranyl peak intensity is almost unchanged, allowing for the full-range ratiometric detection of D2O in H2O.