Lauritsensutherland3300

Distinct facets of an electrocatalyst can promote polysulfide (Li2Sn (n = 4, 6, 8) and Li2Sm (m = 1, 2)) redox kinetics in lithium-sulfur (Li-S) battery chemistry. 7,12-Dimethylbenz[aanthracene manufacturer] Herein, we report that the (100) facet of tungsten disulfide (e-WS2) generated in situ by electrochemical pulverization exhibits onset potentials of 2.52 and 2.32 V vs Li/Li+, respectively, for the reduction of polysulfides Li2Sn and Li2Sm, which is unprecedented till date. In a comparable study, bulk WS2 was synthesized ex situ. The transmission electron microscopy (TEM) analysis reveals that the (100) facet was dominant in e-WS2, while the (002) facet was pronounced in bulk WS2. The density functional theory (DFT) analysis indicates that the (100) facet displays metallic-like behavior, which is highly desired for enhanced polysulfide redox kinetics. We believe that the e-WS2 produced can potentially be an excellent electrocatalyst for other applications such as hydrogen evolution reaction (HER), photocatalysis, and CO2 reduction.An1.33T4Al8Si2 (An = Ce, Th, U, Np; T = Ni, Co) were synthesized in metal flux reactions carried out in aluminum/gallium melts. In previous work, U1.33T4Al8Si2 (T = Co, Ni) analogues were formed by arc-melting UTSi and reacting this mixture in Al/Ga flux. However, in the current work, all compounds were synthesized by using AnO2 reactants, taking advantage of the ability of the aluminum in the flux to act as both solvent and reducing agent. While reactions with T = Co yielded hexagonal Gd1.33Fe4Si10-type quaternary phases for all An, reactions with T = Ni produced these compounds only with An = U and Np. For reactions with An = Ce and Th, the reactions led instead to the formation of AnNi3-xSixAl4-yGay phases, with the tetragonal KCu3S4 structure type. Attempts to synthesize plutonium analogues Pu1.33T4Al8Si2 were also unsuccessful, producing the previously reported PuCoGa5 and Pu2Ni5Si6 instead. Magnetic data collected on the neptunium analogues Np1.33T4Al8Si2 (T = Ni, Co) show antiferromagnetic coupling at low temperatures and indicate a tetravalent state for the Np ions.A series of azobenzene-loaded metal-organic frameworks were synthesized with the general formula M2(BDC)2(DABCO)(AB)x (M = Zn, Co, Ni, and Cu; BDC = 1,4-benzenedicarboxylate; DABCO = 1,4-diazabicyclo[2.2.2]octane; and AB = azobenzene), herein named M-1⊃ABx. Upon occlusion of AB, each framework undergoes guest-induced breathing, whereby the pores contract around the AB molecules forming a narrow-pore (np) framework. The loading level of the framework is found to be very sensitive to the synthetic protocol and although the stable loading level is close to M-1⊃AB1.0, higher loading levels can be achieved for the Zn, Co, and Ni frameworks prior to vacuum treatment, with a maximum composition for the Zn framework of Zn-1⊃AB1.3. The degree of pore contraction upon loading is modulated by the inherent flexibility of the metal-carboxylate paddlewheel unit in the framework, with the Zn-1⊃AB1.0 showing the biggest contraction of 6.2% and the more rigid Cu-1⊃AB1.0 contracting by only 1.7%. Upon heating, each composite shows a temperature-induced phase transition to an open-pore (op) framework, and the enthalpy and onset temperatures of the phase transition are affected by the framework flexibility. For all composites, UV irradiation causes trans → cis isomerization of the occluded AB molecules. The population of cis-AB at the photostationary state and the thermal stability of the occluded cis-AB molecules are also found to correlate with the flexibility of the framework. Over a full heating-cooling cycle between 0 and 200 °C, the energy stored within the metastable cis-AB molecules is released as heat, with a maximum energy density of 28.9 J g-1 for Zn-1⊃AB1.0. These findings suggest that controlled confinement of photoswitches within flexible frameworks is a potential strategy for the development of solid-solid phase change materials for energy storage.Photosubstitution reactions of cis-[Ru(bpy)2(MeCN)2]2+ with a pyrazole ligand (pzH) were studied under various conditions toward the development of a photochemical synthetic route to polypyridyl ruthenium complexes (bpy = 2,2'-bipyridine). In the absence of a base, light irradiation of an acetonitrile solution of pyrazole and cis-[Ru(bpy)2(MeCN)2]2+ gave a mixture of the reactant and cis-[Ru(bpy)2(pzH)(MeCN)]2+. In the presence of a mild base such as N,N-dimethylaminopyridine, a second photosubstitution from cis-[Ru(bpy)2(pzH)(MeCN)]2+ to cis-[Ru(bpy)2(pz)(pzH)]+ (1b) was greatly enhanced, as confirmed by UV-vis and 1H nuclear magnetic resonance spectroscopy. The yields of 1b were increased in solvents with moderate coordinating properties, such as acetone. The successive photosubstitution reaction was observed using a stoichiometric amount of pyrazole.The aim of this study was to investigate the thermoelectric properties of hot-pressed Ba3Cu14-δTe12 as well as its stability with regards to Cu ion movement. For the latter, two single crystals were picked from pellets after they were measured up to 573 and 673 K, which showed no significant changes in the occupancies of any of the Cu sites. All investigated Ba3Cu14-δTe12 materials displayed low thermal conductivity values ( less then 1 W m-1 K-1) and appropriate electrical conductivity values (300-600 Ω-1 cm-1). However, the thermopower values were comparably low ( less then +65 μV K-1), resulting in uncompetitive zT values, with the highest being achieved for Ba3Cu13.175Te12, namely zT = 0.12 at 570 K. In an attempt to decrease the thermal conductivity, and thereby enhance the figure of merit, a brief alloying study with Ag was undertaken. The incorporation of Ag, however, did not produce any significant improvements.A multidentate tetrazole molecule based on a TPE core, tetrakis[4-(1H-tetrazol-5-yl)phenyl]ethylene (H4ttpe) with combined advantages of two functional groups, was synthesized by cycloaddition reaction of the corresponding organic benzonitrile derivative and azide salt. Coordination self-assembly of the in situ formed aggregation-induced emission polytetrazole luminogen with cadmium(II) ion produces an unprecedented tetrazolyl-TPE-based microporous cationic metal-organic framework (MOF) with an unusual (4,5,8T14)-connected net of [Cd4(H4ttpe)2Cl5]·(N3)3, in which the H4ttpe serves as the first undeprotonated tetrazole ligand of octa-coordinating bridging mode. We investigate, for the first time, the utilization of the luminescent MOF containing a TPE core decorated with tetrazolyl terminals for explosive detection based on the change in fluorescence intensity, which shows high selectivity and efficiency in fluorescence quenching toward TNP detection in water solution.The pressure dependence of the magnetic properties of rhombohedral Na2Mn[Mn(CN)6] up to 10 kbar has been studied. The magnetic ordering temperature, Tc, for Na2Mn[Mn(CN)6] reversibly increases with increasing applied hydrostatic pressure, P, by 9.0 K (15.2%) to 68 K at 10 kbar with an average rate of increase, dTc/dP, of 0.86 K/kbar. The magnetization at 50 kOe and remanent magnetization, Mr(H), remain constant with an average value of 13,100 ± 200 and 8500 ± 200 emuOe/mol. The coercive field Hcr increases by 12% from 13,400 to 15,000 Oe. The increase and rate of increase of Tc for rhombohedral Na2Mn[Mn(CN)6] are reduced with respect to monoclinic A2Mn[Mn(CN)6] (A = K and Rb), but they are still greater than those of cubic Cs2Mn[Mn(CN)6]. This is attributed to the compression of the MnNC framework bonding without decreasing ∠MnII-N≡C, maintaining the unit cell in accord with cubic A = Cs at lower applied pressures, and not due to reduction in ∠MnII-N≡C, which correlates with increasing Tc that is reported for A = K and Rb as well as Cs at higher applied pressures.We report on the new Ruddlesden-Popper (RP) oxyfluoride La2NiO2.5F3 containing an unprecedented high amount of fluorine and Ni2+. This oxyfluoride was prepared by topochemical low-temperature fluorination of La2NiO4, which was obtained by a soft chemistry synthesis, with poly(vinylidene difluoride) (PVDF) as fluorinating agent. La2NiO2.5F3 is the first n = 1 RP compound crystallizing in the tetragonal space group P42/nnm (a = 5.7297(6) Å and c = 13.0106(2) Å). The crystal structure shows a unique tilting scheme of the NiO4F2 octahedra that has so far been only theoretically predicted. Combined neutron and X-ray powder diffraction experiments together with bond-valence-sum and DFT+U calculations reveal an unusual anion ordering with fluoride being located on the apical anion sites of the NiO4F2 octahedra. Excess fluorine ions were found to populate two of the four interstitial anion sites in an ordered fashion. A third interstitial anion position is occupied by oxygen ions while the fourth site remains unoccupied. This hitherto unobserved ordering scenario in RP oxyfluorides promotes a strong layerwise alternating tilting of the NiO4F2 octahedra. Magnetic measurements show strong antiferromagnetic interactions with a high Néel temperature of about 225 K and a pronounced ZFC/FC splitting most likely as the result of a small ferromagnetic moment arising from spin canting. The electronic structure was characterized by DFT and UV-vis spectroscopy, and a strong increase of Eg was found compared to La2NiO4 (3.4 eV vs 1.3 eV).N-Heterocyclic carbenes (NHCs) are versatile L-type ligands that have been shown to stabilize coinage metal chalcogenide nanocrystals, such as Ag2S, remarkably well. However, very little research has been done on the interaction between NHC ligands and coinage metal chalcogenide nanocrystal surfaces and subsequent ligand exchange reactions. Herein, solution 1H nuclear magnetic resonance methods were used to monitor ligand exchange reactions on stoichiometric Ag2S nanocrystal platforms with various primary amine and carboxylic acid ligands. Despite the introduction of new ligands, the native NHC ligands remain tightly bound to the Ag2S nanocrystal surface and are not displaced at room temperature. Primary amine and carboxylic acid ligands demonstrated quantitative ligand exchange only after the samples had been heated with an excess incoming ligand, which implies a strong NHC-Ag binding energy. Density functional theory affirms that a model NHC ligand binds the strongest to a Ag12S6 cluster surface, followed by amine and carboxylic acid binding; computational analysis is therefore in line with the absence of NHC displacement observed in experiments. Both the bulky sterics of the C14-alkyl chains on the NHC and the high energies for the binding of NHC to the Ag2S surface contribute to the superior colloidal stability over conventional long-chain amine or carboxylic acid ligands (many months vs hours to days).The photophysical behavior of the cyclometalating Ir(III) complexes [Ir(ppy)2(bpy)]+, where Hppy is 2-phenylpyridine and bpy is 2,2'-bipyridine (complex 1), and [Ir(diFppy)2(dtb-bpy)]+, where diFppy is 2-(2,4-difluorophenyl)pyridine and dtb-bpy is 4,4'-di-tert-butyl-2,2'-bipyridine (complex 2), has been theoretically investigated by performing density functional theory calculations. The two complexes share the same molecular skeleton, complex 2 being derived from complex 1 through the addition of fluoro and tert-butyl substituents, but present notable differences in their photophysical properties. The remarkable difference in their emission quantum yields (0.196 for complex 1 in dichloromethane and 0.71 for complex 2 in acetonitrile) has been evaluated by characterizing both radiative and nonradiative decay paths. It has emerged that the probability of decaying through the nonradiative triplet metal-centered state, normally associated with the loss of the emission quantum yield, does not appear to be the reason behind the reported substantially different emission efficiency.