While colloidal nanocrystals hold tremendous potential for both enhancing fundamental understanding of materials scaling and enabling advanced technologies, progress in both realms can be inhibited by the limited reproducibility of traditional synthetic methods and by the difficulty of optimizing syntheses over a large number of synthetic parameters. Here, we describe an automated platform for the reproducible synthesis of colloidal nanocrystals and for the high-throughput optimization of physical properties relevant to emerging applications of nanomaterials. This robotic platform enables precise control over reaction conditions while performing workflows analogous to those of traditional flask syntheses. We demonstrate control over the size, size distribution, kinetics, and concentration of reactions by synthesizing CdSe nanocrystals with 0.2% coefficient of variation in the mean diameters across an array of batch reactors and over multiple runs. Leveraging this precise control along with high-throughput optical and diffraction characterization, we effectively map multidimensional parameter space to tune the size and polydispersity of CdSe nanocrystals, to maximize the photoluminescence efficiency of CdTe nanocrystals, and to control the crystal phase and maximize the upconverted luminescence of lanthanide-doped NaYF(4) nanocrystals. On the basis of these demonstrative examples, we conclude that this automated synthesis approach will be of great utility for the development of diverse colloidal nanomaterials for electronic assemblies, luminescent biological labels, electroluminescent devices, and other emerging applications.

0.9 ) 2 Se 4.95 is prepared as a glass-ceramic composite of the nominal composition 25%Na 2 Se-15%Ga 2 Se 3 -60%GeSe 2 using Na 2 Se and Ga-Ge-S alloys as precursor in melt-quench processes (evacuated silica amoule, 950 C, several hours). A large Na-ion conductivity of >10 -5 S/cm at ambient temperature is obtained. The crystal phase is possibly stabilized against moisture via encapsulation in an inert glass matrix and forms a 3D continuous percolation network for fast Na-ion conduction. The results demonstrate that the material with planar pathways for alkali-ion diffusion can serve as viable alternative to the conventional solid electrolytes. -(KIM, S. K.; MAO, A.; SEN*, S.; KIM, S.; Chem. Mater. 26 (2014) O is prepared by solid state reaction of a stoichiometric mixture of La 2 S 3 , Bi 2 S 3 , and PbO (evacuated quartz tube, 940 K, 25 h). The compound crystallizes in the tetragonal space group P4/nmm (Z = 2, powder XRD) and shows stacked NaCl-like M 4 S 6 (M: Pb, Bi) layers and fluorite-type La 2 O 2 layers. Electrical resistivity and Hall effect measurements demonstrate that it is a narrow gap semiconductor with an activation energy of 17 meV. The thermopower and the figure of merit at room temperature are -52 V/K and 0.23, resp., which makes LaPbBiS 3 O and its derivatives a promising thermoelectric material. -The novel stoichiometric perovskite SrCrO 2 H is synthesized by high pressure/high temperature reaction of SrO, Cr 2 O 3 , and SrH 2 (5 GPa, 1000 C, 30 min). The compound is characterized by powder neutron and synchrotron X-ray diffraction. SrCrO 2 H crystallizes with the ideal cubic perovskite structure in the space group Pm3m and displays O 2-/H -disorder. Despite the nonbonding nature of the Cr-H-Cr interaction, the compound exhibits G-type spin ordering with an exceptional high Neel temperature of about 380 K. The high T N value is explained by the relieved octahedral tilting that enhances the Cr-O-Cr antiferromagnetic coupling and the reduced frustration between nearest neighbor and next-nearest neighbor interactions. -(TASSEL, C.; GOTO, Y.; KUNO, Y.; HESTER, J.; GREEN, M.; KOBAYASHI, Y.; KAGEYAMA*, H.; Angew. Chem., Int. Ed. 53 (2014) (Pt capsule, 8 GPa, 1623 K, 30 min) and characterized by powder synchrotron XRD, powder neutron diffraction, XANES, second harmonic generation measurements, magnetic and electrical measurements, and DFT calculations. The compound crystallizes in the non-centrosymmetric rhombohedral space group R3 with Z = 3 (Ni 3 TeO 6 -type structure). It shows strong ferrimagnetic ordering with a Curie temperature of 337 K and demonstrates spontaneous structural polarization (68 C cm -2 ). The material is magnetically ordered, non-centrosymmetric, and polar already at room temperature. The results motivate new directions in the search for practical magnetoelectric/multiferroic materials. The synthesis route is an economical and scalable way for mass production of LiFePO 4 F as a cheap cathode material for lithium ion batteries. The crystal structure of (V) is solved fo...

Structure of glasses in the pseudobinary system Ga2Se3-GeSe2 with Ga2Se3 content ranging from 6.3 to 30 mol % is investigated using a combination of Raman and multinuclear ((71)Ga, (77)Se) solid state nuclear magnetic resonance (NMR) spectroscopy. The results indicate that the structure of these glasses consists primarily of a corner sharing network of (Ge/Ga)Se4 tetrahedra with some fraction of edge-sharing GeSe4 tetrahedra and of ethane-like (Se3)Ge-Ge(Se3) units, in which the Ga, Ge, and Se atoms adopt coordination numbers of 4, 4, and 2, respectively. As expected, the concentration of metal-metal bonds increases with addition of Ga2Se3 as the glass structure becomes too deficient in Se to satisfy the tetrahedral coordination of both Ga and Ge by Se atoms alone. These metal-metal bonds are mostly limited to Ge-Ge homopolar bonds, indicating a violation of chemical order. At relatively high degrees of Se-deficiency, however, spectroscopic evidence suggests the formation of triply coordinated Se atoms as an alternate mechanism to accommodate the tetrahedral coordination of Ga and Ge atoms. This observation indicates a violation of the 8-N coordination rule and is reminiscent of oxygen triclusters in isoelectronic Al2O3-SiO2 glasses. Compositional variation of physical properties such as density, molar volume, optical band gap, glass transition temperature, and fragility are shown to be consistent with the proposed structural model.

No abstract

No abstract