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1.
Chemistry ; 2019 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-31873958

RESUMO

Two new heterometallic metal-organic frameworks (MOFs), LnZnTPO 1 and 2 , and two homometallic MOFs, LnTPO 3 and 4 (Ln = Eu for 1 and 3 , and Tb for 2 and 4 ; H 3 TPO = tris-(4-carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of the C 3 -symmetric ligand H 3 TPO with the corresponding metal ion(s) (a mixture of Ln 3+ and Zn 2+ for 1 and 2 , and Ln 3+ alone for 3 and 4 ). Single-crystal X-ray diffraction (SXRD) analysis revealed that 1 and 3 are isostructural to 2 and 4 , respectively. Thermogravimetric analysis (TGA) showed that the framework is thermally stable up to about 400 °C for 1 and 2 , and about 450 °C for 3 and 4 . Powder X-ray diffraction (PXRD) analysis showed their pore structure changes during drying processes. The shapes of gas sorption isotherms for 1 and 3 are almost identical to those for 2 and 4 , respectively. Solvothermal immersion of 1 and 2 in Tb 3+ and Eu 3+ solutions resulted in the framework metal-ion exchange affording 4 and 3 , respectively, as confirmed by photoluminescence (PL), PXRD, infrared (IR), and inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses.

2.
Inorg Chem ; 58(20): 14107-14111, 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31596572

RESUMO

While mixed-metal ions into a single framework can be randomly arranged in most reported cases, it is synthetically challenging to control and organize the distribution of different metal ions over a three-dimensional structure. In this context, for the family of M2(dobpdc) with broad applications, we present the first case of a bimetallic Mg/Zn(dobpdc) framework with a 1:1 compositional ratio, based on a one-dimensional Zn(H2dobpdc) template, which would not be obtained by the conventional reaction of the corresponding metal salts. Moreover, we demonstrate that the resultant compositional ratios in the bimetallic M'/Zn(dobpdc) (M' = Mg, Mn, Co, Ni) are governed by the ionic radii of the metals and the affinity of the metal ions for the linker groups. Notably, the unexpected gradual reduction in the adsorption enthalpy and the mixed CO2 adsorption feature are revealed in Mg/Zn(dobpdc) and its diamine-grafted framework, respectively.

3.
Angew Chem Int Ed Engl ; 58(45): 16152-16155, 2019 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-31502347

RESUMO

An S-shaped gas isotherm pattern displays high working capacity in pressure-swing adsorption cycle, as established for CO2 , CH4 , acetylene, and CO. However, to our knowledge, this type of adsorption behavior has not been revealed for NH3 gas. Herein, we design and characterize a hydrogen-bonded organic framework (HOF) that can adsorb NH3 uniquely in an S-shape (type IV) fashion. While conventional porous materials, mostly with type I NH3 adsorption behavior, require relatively high regeneration temperature, this platform which has significant working capacity is easily regenerated and recyclable at room temperature.

4.
Dalton Trans ; 48(40): 15074-15090, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31559975

RESUMO

We demonstrate white-light emission using lead halide perovskites: (pip)2PbBr6 (pip = piperazine), (pip)2Pb4Cl12, (1mpz)2PbBr6 (1mpz = 1-methylpiperazine), and (2,5-dmpz)0.5PbBr3·2((CH3)2SO) (2,5-dmpz = trans-2,5-dimethylpiperazine, abbreviated as (2,5-dmpz)0.5PbBr3), in which the inorganic frameworks were connected by piperazinium dications through hydrogen bonds, forming a three-dimensional supramolecular network. From single-crystal X-ray diffraction measurements and Raman spectroscopy, we identified the crystal structures and local environmental vibrational modes in the inorganic framework, finding that (pip)2PbBr6 crystallized in the centrosymmetric orthorhombic space group Pnnm, whereas (pip)2Pb4Cl12 crystallized in the trigonal/rhombohedral space group R3. The zero-dimensional (1mpz)2PbBr6 structure crystallized in the centrosymmetric monoclinic space group P2/n, whereas the [PbBr6]4- octahedron was separated by a 1-methylpiperazine dication. (2,5-dmpz)0.5PbBr3·2((CH3)2SO) contained half a cation, which was completed by inversion symmetry, along with two dimethyl sulfoxide solvent molecules that crystallized in the monoclinic space group P21/c. Among the perovskites, (2,5-dmpz)0.5PbBr3·2((CH3)2SO) exhibited the longest carrier lifetime (42 ns), the lowest band gap (2.34 eV), and the highest photoluminescence quantum yield (58.02%). This is because it forms a 1D corner-sharing structure and has localized electronic states near the conduction band minimum, which contributes to the high photoluminescence quantum yield and white-light emission.

5.
Polymers (Basel) ; 11(9)2019 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-31480664

RESUMO

Polymer-based micro-electrode arrays (MEAs) are gaining attention as an essential technology to understand brain connectivity and function in the field of neuroscience. However, polymer based MEAs may have several challenges such as difficulty in performing the etching process, difficulty of micro-pattern generation through the photolithography process, weak metal adhesion due to low surface energy, and air pocket entrapment over the electrode site. In order to compensate for the challenges, this paper proposes a novel MEA fabrication process that is performed sequentially with (1) silicon mold preparation; (2) PDMS replica molding, and (3) metal patterning and parylene insulation. The MEA fabricated through this process possesses four arms with electrode sites on the convex microstructures protruding about 20 µm from the outermost layer surface. The validity of the convex microstructure implementation is demonstrated through theoretical background. The electrochemical impedance magnitude is 204.4 ± 68.1 kΩ at 1 kHz. The feasibility of the MEA with convex microstructures was confirmed by identifying the oscillation in the beta frequency band (13-30 Hz) in the electrocorticography signal of a rat olfactory bulb during respiration. These results suggest that the MEA with convex microstructures is promising for applying to various neural recording and stimulation studies.

6.
Chem Commun (Camb) ; 55(65): 9713-9716, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31353388

RESUMO

Single-crystal-to-single crystal structural conversions occur in a Zn(ii) coordination polymer, uniquely induced by fine-tuned relative humidity. Proton conductivity depends on the number of hydrogen bonds in the structures. Slope change in the Arrhenius plot is uncommon among coordination-based conductors and associated with temperature-dependent phase changes.

7.
Chem Sci ; 9(33): 6871-6877, 2018 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-30310620

RESUMO

A hypercrosslinked porous organic polymer was modified by post-oxidation and post-sulfonation to obtain a porous platform with a high density of acidic groups. Such an acidified material exhibits record high NH3 adsorption capacity per surface area, fast adsorption rate, and recyclability at low desorption temperature. Noticeably, the coating of the polymer with PDMS represents a facile and efficient route to enable both a significant improvement of low-pressure NH3 adsorption capacity (∼40-fold enhancement; from 0.04 to 1.41 mmol g-1) with respect to the non-modified polymer at 500 ppm and hydrophobicity associated with the selective sorption of NH3 over water vapor (hydrophilic for the non-coated material). This material is easy to prepare, cost-effective, and scalable to mass production.

8.
Acta Crystallogr E Crystallogr Commun ; 74(Pt 8): 1107-1110, 2018 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-30116572

RESUMO

The asymmetric unit of the solvated title complex, [Ir(C11H8N)2(C15H14NO3)]·2CH2Cl2, consists of two complex mol-ecules together with four di-chloro-methane solvent mol-ecules, one of which is disordered. In each complex mol-ecule, the IrIII ion has a distorted octa-hedral coordination environment defined by two 2-phenyl-pyridine ligands, through two phenyl C and two pyridine N atoms, and by one N,O-bidentate 2-[(2,4-di-meth-oxy-phenyl-imino)-meth-yl]phenolate anion. The IrIII ions lie almost in the equatorial planes with deviations of 0.0396 (17) and 0.0237 (17) Å, respectively, for the two complex mol-ecules. In both complex mol-ecules, the two 2-phenyl-pyridine ligands are nearly perpendicular to each other [dihedral angles between the least-squares-planes of 89.91 (11) and 85.13 (11)°]. In the crystal, inter-molecular C-H⋯O inter-actions as well as inter-molecular C-H⋯π inter-actions are present, leading to a three-dimensional network structure. One of the four dichlormethane solvent mol-ecules shows disorder over two sets of sites [occupancy ratio 0.79 (2):0.21 (2)].

9.
ChemSusChem ; 11(10): 1694-1707, 2018 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-29603670

RESUMO

For real-world postcombustion applications in the mitigation of CO2 emissions using dry sorbents, adsorption and desorption behaviors should be controlled to design and fabricate prospective materials with optimal CO2 performances. Herein, we prepared diamine-functionalized Mg2 (dobpdc) (H4 dobpdc=4,4'-dihydroxy-(1,1'-biphenyl)-3,3'-dicarboxylic acid). (1-diamine) with ethylenediamine (en), primary-secondary (N-ethylethylenediamine-een and N-isopropylethylenediamine-ipen), primary-tertiary, and secondary-secondary diamines. A slight alteration of the number of alkyl substituents on the diamines and their alkyl chain length dictates the desorption temperature (Tdes ) at 100 % CO2 , desorption characteristics, and ΔT systematically to result in the tuning of the working capacity. The existence of bulky substituents on the diamines improves the framework stability upon exposure to O2 , SO2 , and water vapor, relevant to real flue-gas conditions. Bulky substituents are also responsible for an interesting two-step behavior observed for the ipen case, as revealed by DFT calculations. Among the diamine-appended metal-organic frameworks, 1-een, which has the required adsorption and desorption properties, is a promising material for sorbent-based CO2 capture processes. Hence, CO2 performance and framework durability can be tailored by the judicial selection of the diamine structure, which enables property design at will and facilitates the development of desirable CO2 -capture materials.

10.
Org Lett ; 19(20): 5509-5512, 2017 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-29019410

RESUMO

Calix[n]triazoles are developed as new derivatives in the calixarene family. Calixtriazole compounds 2-4 are synthesized using an iterative convergent strategy including an inter-/intramolecular copper(I)-catalyzed azide-alkyne cycloaddition reaction. Solid-state structures are clearly refined to give 1,2-alternate and partial cone conformations for calix[4]triazole and calix[5]triazole, respectively. Theoretical studies based on density functional theory (DFT) calculations indicated that intermolecular interactions are crucial in determining the conformers of the crystals, and the most stable conformers of calix[4]triazole, calix[5]triazole, and calix[6]triazole in the monomeric forms are 1,3-alternate, 1,3-alternate, and 1,3,5-alternate, respectively.

11.
Inorg Chem ; 56(13): 7443-7448, 2017 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-28617591

RESUMO

Three MOF-74-type Co(II) frameworks with one-dimensional hexagonal channels have been prepared. Co(II) spins in a chain are ferromagnetically coupled through carboxylate and phenoxide bridges. Interchain antiferromagnetic couplings via aromatic ring pathways operate over a Co-Co length shorter than ∼10.9 Å, resulting in a field-induced metamagnetic transition, while being absent over lengths longer than ∼14.7 Å.

12.
Inorg Chem ; 56(9): 4911-4917, 2017 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-28414438

RESUMO

Controlling the coordination sphere of lanthanoid complexes is a challenging critical step toward controlling their relaxation properties. Here we present the synthesis of hexacoordinated dysprosium single-molecule magnets, where tripodal ligands achieve a near-perfect octahedral coordination. We perform a complete experimental and theoretical investigation of their magnetic properties, including a full single-crystal magnetic anisotropy analysis. The combination of electrostatic and crystal-field computational tools (SIMPRE and CONDON codes) allows us to explain the static behavior of these systems in detail.

13.
ChemSusChem ; 10(3): 541-550, 2017 02 08.
Artigo em Inglês | MEDLINE | ID: mdl-28004886

RESUMO

A combined sonication and microwave irradiation procedure provides the most effective functionalization of ethylenediamine (en) and branched primary diamines of 1-methylethylenediamine (men) and 1,1-dimethylethylenediamine (den) onto the open metal sites of Mg2 (dobpdc) (1). The CO2 capacities of the advanced adsorbents 1-en and 1-men under simulated flue gas conditions are 19 wt % and 17.4 wt %, respectively, which are the highest values reported among amine-functionalized metal-organic frameworks (MOFs) to date. Moreover, 1-den exhibits both a significant working capacity (12.2 wt %) and superb CO2 uptake (11 wt %) at 3 % CO2 . Additionally, this framework showcases the superior recyclability; ultrahigh stability after exposure to O2 , moisture, and SO2 ; and exceptional CO2 adsorption capacity under humid conditions, which are unprecedented among MOFs. We also elucidate that the performance of CO2 adsorption can be controlled by the structure of the diamine ligands grafted such as the number of amine end groups or the presence of side groups, which provides the first systematic and comprehensive demonstration of fine-tuning of CO2 uptake capability using different amines.


Assuntos
Dióxido de Carbono/química , Diaminas/química , Compostos Organometálicos/química , Adsorção , Dióxido de Carbono/isolamento & purificação , Modelos Moleculares , Conformação Molecular , Oxigênio/química , Teoria Quântica , Vapor , Dióxido de Enxofre/química , Temperatura Ambiente
14.
Chemistry ; 23(20): 4803-4809, 2017 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-28009932

RESUMO

With regard to fluorescence quenching commonly observed during metal-ion detection, "turn-on" chemical sensing has been rarely reported, but could be extremely important because it facilitates the selective recognition of target objects of interest against a dark background. A metal-organic framework (MOF) chemosensor has been prepared that serves as an efficient platform for the selective detection of Cu2+ and Cd2+ ions over other metal ions. In particular, this framework shows the highest fluorescence enhancement (≈60-fold relative to Cd-free MOF) for the hazardous metal ion Cd2+ among luminescent MOFs and displays excellent reusability in repeated cycles. The direct diffusion of Cd2+ into the crystal pores has also been visualized for the first time.

15.
Inorg Chem ; 56(1): 305-312, 2017 Jan 03.
Artigo em Inglês | MEDLINE | ID: mdl-27936739

RESUMO

Five-fold interpenetrated Zn(II) frameworks (1 and 2) have been prepared, and an irreversible phase transformation from 1 to 2 is found to occur through a dissolution-recrystallization process. Compound 1 exhibits the highest quenching efficiency (>96%) for nitrobenzene at 7 ppm among luminescent coordination polymers. Selective discrimination of nitroaromatic molecules including o-nitrophenol (o-NP), p-nitrophenol (p-NP), 2,4-dinitrophenol (DNP), and 2,4,6-trinitrophenol (TNP) is realized in 1 and 2 as a result of the fact that the framework-analyte interaction affords characteristic emission signals. This observation is the first case of a nonporous coordination framework for such discriminative detection. Notably, significant hydrophobicity is evident in the framework 1 because of its surface roughness, which accounts for the enhanced quenching ability.

16.
Polymers (Basel) ; 9(12)2017 Dec 08.
Artigo em Inglês | MEDLINE | ID: mdl-30965988

RESUMO

Conventional polymer multielectrode arrays (MEAs) have limitations resulting from a high Young's modulus, including low conformability and gaps between the electrodes and neurons. These gaps are not a problem in soft tissues such as the brain, due to the repopulation phenomenon. However, gaps can result in signal degradation when recording from a fiber bundle, such as the spinal cord. Methods: We propose a method for fabricating flexible polydimethylsiloxane (PDMS)-based MEAs featuring plateau-shaped microelectrodes. The proposed fabrication technique enables the electrodes on the surface of MEAs to make a tight connection to the neurons, because the wire of the MEA is fabricated to be plateau-shaped, as the Young's modulus of PDMS is similar to soft tissues and PDMS follows the curvature of the neural tissue due to its high conformability compared to the other polymers. Injury caused by the movement of the MEAs can therefore be minimized. Each electrode has a diameter of 130 µm and the 8-channel array has a center-to-center electrode spacing of 300 µm. The signal-to-noise ratio of the plateau-shaped electrodes was larger than that of recessed electrodes because there was no space between the electrode and neural cell. Reliable neural recordings were possible by adjusting the position of the electrode during the experiment without trapping air under the electrodes. Simultaneous multi-channel neural recordings were successfully achieved from the spinal cord of rodents. We describe the fabrication technique, electrode 3D profile, electrode impedance, and MEA performance in in vivo experiments in rodents.

17.
Nat Commun ; 7: 13489, 2016 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-27845342

RESUMO

A hallmark of Weyl semimetal is the existence of surface Fermi arcs. An intriguing question is what determines the connectivity of surface Fermi arcs, when multiple pairs of Weyl nodes are present. To answer this question, we show that the locations of surface Fermi arcs are predominantly determined by the condition that the Zak phase integrated along the normal-to-surface direction is . The Zak phase can reveal the peculiar topological structure of Weyl semimetal directly in the bulk. Here, we show that the winding of the Zak phase around each projected Weyl node manifests itself as a topological defect of the Wannier-Stark ladder, energy eigenstates under an electric field. Remarkably, this leads to bulk Fermi arcs, open-line segments in the bulk spectra. Bulk Fermi arcs should exist in conjunction with surface counterparts to conserve the Weyl fermion number under an electric field, which is supported by explicit numerical evidence.

18.
Angew Chem Int Ed Engl ; 55(52): 16123-16126, 2016 12 23.
Artigo em Inglês | MEDLINE | ID: mdl-27885758

RESUMO

We demonstrate the facile microwave-assisted synthesis of a porous organic framework 1 and the sulfonated solid (1S) through postsubstitution. Remarkably, the conductivity of 1S showed an approximately 300-fold enhancement at 30 °C as compared to that of 1, and reached 7.72×10-2  S cm-1 at 80 °C and 90 % relative humidity. The superprotonic conductivity exceeds that observed for any conductive porous organic polymer reported to date. This material, which is cost-effective and scalable for mass production, also revealed long-term performance over more than 3 months without conductivity decay.

19.
Ann Dermatol ; 28(5): 575-578, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-27746636

RESUMO

BACKGROUND: Fungi are eukaryotic microorganisms including yeast and molds. Many studies have focused on modifying bacterial growth, but few on fungal growth. Microcurrent electricity may stimulate fungal growth. OBJECTIVE: This study aims to investigate effects of microcurrent electric stimulation on Trichophyton rubrum growth. METHODS: Standard-sized inoculums of T. rubrum derived from a spore suspension were applied to potato dextrose cornmeal agar (PDACC) plates, gently withdrawn with a sterile pipette, and were applied to twelve PDACC plates with a sterile spreader. Twelve Petri dishes were divided into four groups. The given amperage of electric current was 500 nA, 2 µA, and 4 µA in groups A, B, and C, respectively. No electric current was given in group D. RESULTS: In the first 48 hours, colonies only appeared in groups A and B (500 nA and 2 µA exposure). Colonies in group A (500 nA) were denser. Group C (4 µA) plates showed a barely visible film of fungus after 96 hours of incubation. Fungal growth became visible after 144 hours in the control group. CONCLUSION: Lower intensities of electric current caused faster fungal growth within the amperage range used in this study. Based on these results, further studies with a larger sample size, various fungal species, and various intensities of electric stimulation should be conducted.

20.
Chem Commun (Camb) ; 52(92): 13460-13462, 2016 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-27782273

RESUMO

A plasmonic liquid junction photovoltaic cell with greatly improved power conversion efficiency is described. When illuminated with simulated sunlight, the device (Au-TiO2/V3+(0.018 M), V2+(0.182 M)/Pt) reproducibly and sustainably produces an VOC of 0.50 V and a JSC of 0.5 mA cm-2, corresponding to a power conversion efficiency of 0.095%.

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