ABSTRACT
Gold nanoclusters exhibiting concomitant photothermy (PT) and photoluminescence (PL) under near-infrared (NIR) light irradiation are rarely reported, and some fundamental issues remain unresolved for such materials. Herein, we concurrently synthesized two novel rod-shaped Au nanoclusters, Au52(PET)32 and Au66(PET)38 (PET = 2-phenylethanethiol), and precisely revealed that their kernels were 4 × 4 × 6 and 5 × 4 × 6 face-centered cubic (fcc) structures, respectively, based on the numbers of Au layers in the [100], [010], and [001] directions. Following the structural growth mode from Au52(PET)32 to Au66(PET)38, we predicted six more novel nanoclusters. The concurrent synthesis provides rational comparison of the two nanoclusters on the stability, absorption, emission and photothermy, and reveals the aspect ratio-related properties. An interesting finding is that the two nanoclusters exhibit concomitant PT and PL under 785 nm light irradiation, and the PT and PL are in balance, which was explained by the qualitative evaluation of the radiative and non-radiative rates. The ligand effects on PT and PL were also investigated.
ABSTRACT
Atomically precise ~1-nm Pt nanoparticles (nanoclusters, NCs) with ambient stability are important in fundamental research and exhibit diverse practical applications (catalysis, biomedicine, etc.). However, synthesizing such materials is challenging. Herein, by employing the mixture ligand protecting strategy, we successfully synthesized the largest organic-ligand-protected (~1-nm) Pt23 NCs precisely characterized with mass spectrometry and single-crystal X-ray diffraction analyses. Interestingly, natural population analysis and Bader charge calculation indicate an alternate, varying charge -layer distribution in the sandwich-like Pt23 NC kernel. Pt23 NCs can catalyze the oxygen reduction reaction under acidic conditions without requiring calcination and other treatments, and the resulting specific and mass activities without further treatment are sevenfold and eightfold higher than those observed for commercial Pt/C catalysts, respectively. Density functional theory and d-band center calculations interpret the high activity. Furthermore, Pt23 NCs exhibit a photothermal conversion efficiency of 68.4 % under 532-nm laser irradiation and can be used at least for six cycles, thus demonstrating great potential for practical applications.
ABSTRACT
The atom-transfer radical addition (ATRA) reaction simultaneously forges carbon-carbon and carbon-halogen bonds. However, frequently-used photosensitizers such as precious transition metal complexes, or organic dyes have limitations in terms of their potential toxicity and recyclability. Three ß-ketoenamine-linked covalent organic frameworks (COFs) from 1,3,5-triformylphloroglucinol and 1,4-phenylenediamines with variable transient photocurrent and photocatalytic activity have been prepared. A COF bearing electron-deficient Cl atoms displayed the highest photocatalytic activity toward the ATRA reaction of polyhalogenated alkanes to give halogenated olefins under visible light at room temperature. This heterogeneous photocatalyst exhibited good functional group tolerance and could be recycled without significant loss of activity.
ABSTRACT
A novel dimension splitting method is proposed for the efficient numerical simulation of a biochemotaxis model, which is a coupled system of chemotaxis-fluid equations and incompressible Navier-Stokes equations. A second-order pressure correction method is employed to decouple the velocity and pressure for the Navier-Stokes equations. Then, the alternating direction implicit scheme is used to solve the velocity equation, and the operator with dimension splitting effect is used instead of the traditional elliptic operator to solve the pressure equation. For the chemotactic equation, the operator splitting method and extrapolation technique are used to solve oxygen and cell density to achieve second-order time accuracy. The proposed dimension splitting method splits the two-dimensional problem into a one-dimensional problem by splitting the spatial derivative, which reduces the computation and storage costs. Finally, through interesting experiments, we show the evolution of the cell plume shape during the descent process. The effect of changing specific parameters on the velocity and plume shape during the descent process is also studied.
ABSTRACT
Metal nanoclusters have recently attracted extensive interest from the scientific community. However, unlike carbon-based materials and metal nanocrystals, they rarely exhibit a sheet kernel structure, probably owing to the instability caused by the high exposure of metal atoms (particularly in the relatively less noble Ag or Cu nanoclusters) in such a structure. Herein, we synthesized a novel AgCu nanocluster with a sandwich-like kernel (diameter≈0.9â nm and length≈0.25â nm) by introducing the furfuryl mercaptan ligand (FUR) and the alloying strategy. Interestingly, the kernel consists of a centered silver atom and two planar Ag10 pentacle units with completely mirrored symmetry after a rotation of 36 degrees. The two Ag10 pentacles and some extended structures show an unreported golden ratio geometry, and the two inner five-membered rings and the centered Ag atom form an unanticipated full-metal ferrocene-like structure. The featured kernel structure causes the dominant radial direction transition of excitation electrons, as determined via time-dependent density functional theory calculations, which affords the protruding absorption at 612â nm and contributes to the promising photothermal conversion efficiency of 67.6 % of the as-obtained nanocluster, having important implications for structure-property correlation and the development of nanocluser-based photothermal materials.
ABSTRACT
The reaction of the carbazole ligand supported Ga(I) compound LGa(THF) (3) and 1-azido-4-(tert-butyl)benzene (ArN3) afforded the first stable tetrazagallole LGaN4Ar2 (4) bearing a three-coordinate Ga atom. Reduction of 4 with elemental potassium resulted in the radical dimer {[K(18-c-6)]+[4]Ë-}2, featuring a strong antiferromagnetic interaction between the spin centers.
ABSTRACT
Strong Mn-Mn coupling interactions (dipole-dipole and spin-exchange), predominantly determined by statistically and apparently short Mn···Mn distances in traditional heavily Mn2+-doped semiconductors, can promote energy transfer within randomly positioned and close-knit Mn2+ pairs. However, the intrinsic mechanism on controlling Mn2+ emission efficiency is still elusive due to the lack of precise structure information on local tetrahedrally coordinated Mn2+ ions. Herein, a group of Mn2+-containing metal-chalcogenide open frameworks (MCOFs), built from [Mn4In16S35] nanoclusters (denoted T4-MnInS) with a precise [Mn4S] configuration and length-variable linkers, were prepared and selected as unique models to address the above-mentioned issues. MCOF-5 and MCOF-6 that contained a symmetrical [Mn4S] core with a D2d point group and relatively long Mn···Mn distance (â¼3.9645 Å) exhibited obvious red emission, while no room-temperature PL emission was observed in MCOF-7 that contained an asymmetric [Mn4S] configuration with a C1 point group and relatively short Mn···Mn distance (â¼3.9204 Å). The differences of Mn-Mn dipole-dipole and spin-exchange interactions were verified through transient photoluminescent spectroscopy, electron spin resonance (ESR), and magnetic measurements. Compared to MCOF-5 and MCOF-6 showing a narrower/stronger ESR signal and longer decay lifetime of microseconds, MCOF-7 displayed a much broader/weaker ESR signal and shorter decay lifetime of nanoseconds. The results demonstrated the dominant role of distance-directed Mn-Mn dipole-dipole interactions over symmetry-directed spin-exchange interactions in modulating PL quenching behavior of Mn2+ emission. More importantly, the reported work offers a new pathway to elucidate Mn2+-site-dependent photoluminescence regulation mechanism from the perspective of atomically precise nanoclusters.
ABSTRACT
The direct electroreduction of CO2 to ratio-tunable syngas (CO + H2) is an appealing solution to provide important feedstocks for many industrial processes. However, low-cost, Earth-abundant yet efficient and stable electrocatalysts for composition-adjustable syngas have still not been realized for practical applications. Herein, new hierarchical 0D/2D heterostructures of SnO2 nanoparticles (NPs) confined on CuS nanosheets (NSs) were designed to enable CO2 electroreduction to a wide-range syngas (CO/H2: 0.11-3.86) with high faradaic efficiency (>85%), remarkable turnover frequency (96.12 h-1) and excellent durability (over 24 h). Detailed experimental characterization studies together with theoretical calculations manifest that the ascendant catalytic performance is not only attributed to the heterostructure of ultrasmall SnO2 NPs homogeneously confined on ultrathin CuS NSs, which endows the maximum exposure of active sites and faster charge transfer, but is also accounted by the strong interaction between well-defined SnO2 and CuS interfaces, which modulated reaction free-energies of reaction intermediates and hence improved the activity of CO2 electroreduction to highly ratio-tunable syngas. This work provides a better understanding and a new strategy for intermediate regulation by interface engineering of hereostructures for CO2 reduction and beyond.
ABSTRACT
Although the water gas shift (WGS) reaction has sparked intensive attention for the production of high-purity hydrogen, the design of cost-efficient catalysts with noble metal-like performance still remains a great challenge. Here, we successfully overcome this obstacle by using Se-incorporated MoS2 with a 1T phase. Combining the optimized electronic structure, additional active sites from edge sites, and a sulfur vacancy based on the 1T phase, as well as the high surface ratio from the highly open structure, the optimal MoS1.75Se0.25 exhibits superior activity and stability compared to the conventional 2H-phase MoS2, with poor activity, large sulfur loss, and rapid inactivation. The hydrogen production of MoS1.75Se0.25 is 942 µmol, which is 1.9 times higher than MoS2 (504 µmol) and 2.8 times higher than MoSe2 (337 µmol). Furthermore, due to the lattice stabilization via Se-incorporation, MoS1.75Se0.25 exhibited excellent long-term stability without obvious change in more than 10 reaction rounds. Our results demonstrate a pathway to design efficient and cost-efficient catalysts for WGS.
ABSTRACT
A luminescent lanthanide metal-organic framework [Tb7(OH)8(H2O)6(IDA)3(COO)3]·4Cl·2H2O (Tb-IDA, IDA = iminodiacetic acid) was hydrothermally synthesized and structurally characterized. Monitoring ultraviolet radiation was achieved by correlating the dosage with the luminescence color change in doped Gd99Tb0.1Eu0.9-IDA compound. A linear relationship is developed across a broad range from blue to yellow within a CIE chromaticity diagram.
ABSTRACT
Remarkable progresses regarding pure inorganic frameworks and metal-organic frameworks (MOF) have been made. However, pure inorganic frameworks with MOF-like grid structures are rarely reported due to the weakness of inorganic moiety as a long linear linker. We report herein a fascinating inorganic framework assembled by a [Ge4S10]4- cluster node and a linear [-Cu-MS4-Cu-] (M = Mo (1) and W (2)) inorganic pillar. Their network shows MOF-like orthogonal structure with two interpenetrated two-dimensional (2D) plus 2D to 3D framework and a 1D nano tunnel. Electrodes with crystalline sample of 1 and 2, inorganic sulfide framework, were prepared, and their quasi-capacitance behaviors were investigated. Electrochemical performances were evaluated by cyclic voltammetry and galvanostatic charge-discharge techniques in CsOH, KOH, NaOH, and LiOH electrolytes. The results revealed that the crystal materials exhibit moderate specific capacitance values that are comparable to those of porous sulfide materials.
ABSTRACT
A lot of ternary In-Sb-Q (Q = S, Se) chalcogenido-metalates with amines or complex cations have been recently reported for their diverse structures, however, such a type of In-Sn-Q chalcogenido-metalate has been rarely announced. Herein, we report a series of 2-D In-Sn-Q compounds prepared using a metal-phenanthroline cationic template, [M(Phen)3](In2Sn2Q8)·(amine)·nH2O (M = Ni(II), Fe(II) or Co(II); amine = cyclohexylamine (Cha) or 1,6-diaminohexane (Dah); Q = S or Se). Their anions are isostructural and a 2-D porous network with large 16-tetrahedron-rings. The 2-D network joint of In-Sn-Q is a (In/Sn)3Q3 six-membered ring, which is different from the Sn3Q4 pseudosemicube of most 2-D Sn-Q binary compounds. The materials exhibit photocurrent response properties measured using a photo-electrochemical cell. The result shows that (1) the selenides exhibit more intense photocurrents than the sulfides and (2) the current intensity is related to the metal-phenanthroline cations.
ABSTRACT
As most of the chalcogenidometalate anions are well-known electron-rich systems, design and preparation of ion pair compounds, by integrating an organic acceptor (A) with an inorganic chalcogenidometalate donor (D), are an attractive strategy to obtain new functional materials. We report herein the single-crystal structures and properties of three new ion pair charge-transfer (IPCT) compounds by incorporating thiogermanates with methylviologen (MV(2+), N,N'-dimethyl-4,4'-bipyridinium dication), [MV]2Ge4S10·xSol (Sol = solvent). Sharp and fast solvent-induced color changes and switchable fluorescence emission are observed for the compounds. The weak interactions that relate to the solvent and ions in the structures are likely the key points to modulate the cation-anion charge-transfer. A photocurrent response is observed for the photoelectric system of the IPCT compound upon repetitive switching of light on and off.
ABSTRACT
A new mixed-valence thioarsenate(II,III) [Ni(dap)3]4-[As10Cu2S18] (1, dap = diaminopropane) has been solvothermally synthesized and structurally characterized. 1 features a new heterometallic thioarsenate [As10Cu2S18](8-) with mixed valence As(2+)/As(3+) ions, which is constructed by combination of the chair-shaped tetramer cyclo-[As4S8] and the rare heterometallic cluster [As3CuS6]. 1 is the first example of transition metal ions encapsulated within mixed-valent thioarsenates(II,III). The optical properties of 1 have also been investigated.
ABSTRACT
Thiogermanates, {[Ni(phen)(3)](2)Ge(4)S(10)}·xSol (Sol = 4MeOH·12H(2)O (1) and 24H(2)O (2)) were prepared and characterized by single-crystal structure analysis. There are large quantities of the solvent molecules that cocrystallize with the anions and cations and form a strong hydrogen bonding network (O-H···S and O···H-O-H···O). Reversible yellow-pink color change with fast speed was found for these compounds, when the crystals were immersed in alcohol solvents and water alternately. The time of the solvent-induced color change relates to the molecular size and structure of the alcohols. The smaller the molecule is, the faster the color change will be. The fastest color change was found by using the methanol solvent that took only about one second. The color change also relates to the ratio of water/alcohol. The solvatochromism phenomenon is accompanied with a rapid solvent-induced recrystallization that is verified by the XRD patterns.
ABSTRACT
The preparation and crystal structure of a large wheel-shaped indium-telluride compound are reported. The inorganic cluster is decorated with 1,2-diaminocyclohexane molecules that play an important role in the formation of the nanoring. A related new 1D polymeric InTe compound is also presented in order to understand the effect of acidity on the formation of the ring structure.
ABSTRACT
Supertetrahedral compounds of chalcogenometalates (T3 cluster compounds) integrated with Ni-bpy (bpy = 2,2'-bipyridine) complex were prepared by a solvothermal technique. The compound [Ni(bpy)(3)](3)[H(4)In(10)S(20)]·bpy·2EG·6H(2)O (Mb-InS-1) (EG = ethylene glycol) consists of discrete T3 clusters of [H(4)In(10)S(20)](6-) with three [Ni(bpy)(3)](2+) cations. The compound [Ni(bpy)(3)](2)[H(2)In(10)S(19)]·bpy·2HEA·2H(2)O (Mb-InS-2) (EA = ethanolamine) is a 1-D polymer, in which zigzag T3 cluster chains are charge balanced by metal-bpy complex cations. The compound [Ni(bpy)(3)](7)[H(4)In(40)S(74)]·7Hbpy·3HEA·8H(2)O (Mb-InS-3) is a 2-D T3 polymer with cation layers of [Ni(bpy)(3)](2+). Integrating M-bpy complex cations into chalcogenido structures has been made with the aim of improving the photoabsorption of the materials. The electronic spectra showed the new bands of cation-anion charge-transfer (CACT) that is mainly caused by the S···H-C(py) contacts between the InS T3 supertetrahedral clusters and the [Ni(bpy)(3)](2+) cations.
Subject(s)
2,2'-Dipyridyl/chemistry , Indium/chemistry , Organometallic Compounds/chemical synthesis , Sulfides/chemistry , Crystallography, X-Ray , Models, Molecular , Organometallic Compounds/chemistryABSTRACT
Three anion-cation compounds 1-3 with formula [M(phen)(3)][Cd(4)(SPh)(10)]·Sol (M = Ru(2+), Fe(2+), and Ni(2+), Sol = MeCN and H(2)O) have been synthesized and characterized by single-crystal analysis. Both the cations and anion are well-known ions, but the properties of the co-assembled compounds are interesting. Molecular structures and charge-transfer between the cations and anions in crystal and even in solution are discussed. These compounds are isomorphous and short inter-ion interactions are found in these crystals, such as π···π stacking and C-H···π contacts. Both spectroscopic and theoretical calculated results indicate that there is anion-cation charge-transfer (ACCT) between the Ru-phen complex dye and the Cd-SPh cluster, which plays an important role in their photophysical properties. The intensity of the fluorescent emission of the [Ru(phen)(3)](2+) is enhanced when the cation interacts with the [Cd(4)(SPh)(10)](2-) anion. The mechanism for the enhancement of photoluminescence has been proposed.
ABSTRACT
A new cation- and anion-sensitive system based on a TTF derivative with a diamino-diamido moiety (H(2)L) has been studied. The results of cyclic voltammetry indicated that the redox potentials of the protonated H(2)L (H(4)L(2+)) selectively respond to later transition metal cations and some oxo anions. Solid-state structures of the cation-anion compounds formed by H(4)L(2+) and oxo anions were characterized crystallographically, which is helpful to understand the matter of the sensitivity for the anion. There are two types of hydrogen bonds in these compounds, one is with an amino group and the other is with an amido group. The shift of the redox potential is obviously related to formation of hydrogen bonding with the amido group. The packing structures of these cation-anion compounds are arranged to layered sandwiched structures assembled by an oxo-anion layer and two TTF layers through hydrogen bonding.
Subject(s)
Chemistry Techniques, Analytical/instrumentation , Heterocyclic Compounds/chemistry , Electrochemistry , Models, Molecular , Molecular Conformation , Oxidation-ReductionABSTRACT
Though numerous metal-organic frameworks or polymers have been reported, the organic building blocks are usually not redox-active. On the other hand, some mono-, di- or tri-nuclear compounds with tetrathiafulvalene (TTF) have been prepared, although little is known about the coordination polymers combined with paramagnetic metals and organic TTF ligands. We report herein a series of coordination polymers of copper(II) and manganese(II) with TTF dicarboxylate ligand (L). Compound 1, [CuL(2,2-bpy)](n), is a one-dimensional (1-D) coordination polymer with five-coordinated square-pyramidal Cu(II) centers. Mn(II) complex 2, [MnL(2,2-bpy)](n), also takes a 1-D structure, showing a double-bridged mode by carboxylate groups. The 4,4-bipyridine compound 3, [MnL(4,4-bpy)(H(2)O)](n)·CH(3)CN, takes a 2-D grid network. A zinc(II) compound 4, [ZnL(4,4-bpy)(H(2)O)](n)·CH(3)CN, isomorphous structure with 3, is also presented. The electrochemical properties of the solid-state compounds were investigated by cyclic voltammetry using surface-modified electrodes. As usually observed in TTF derivatives, two sets of redox-waves were observed. The values of E(1/2)(1) of compounds 1-4 are in the order of 2(Mn) ≈ 3(Mn) < 1(Cu) < 4(Zn), indicating that the metal coordination can affect the potential shift of the TTF ligand. Weak antiferromagnetic exchanges are observed for compounds 1, 2, and 3.
