A rigid and healable polymer cross-linked by weak but abundant Zn(II)-carboxylate interactions.

Achieving a desirable combination of solid-like properties and fast self-healing is a great challenge due to slow diffusion dynamics. In this work, we describe a design concept that utilizes weak but abundant coordination bonds to achieve this objective. The designed PDMS polymer, crosslinked by abundant Zn(II)-carboxylate interactions, is very strong and rigid at room temperature. As the coordination equilibrium is sensitive to temperature, the mechanical strength of this polymer rapidly and reversibly changes upon heating or cooling. The soft-rigid switching ability σ, defined as G'max /G'min, can reach 8000 when ΔT = 100 °C. Based on these features, this polymer not only exhibits fast thermal-healing properties, but is also advantageous for various applications such as in orthopedic immobilization, conductive composites/adhesives, and 3D printing.

Sequential Introduction of Cations Deriving Large-Grain Csx FA1-x PbI3 Thin Film for Planar Hybrid Solar Cells: Insight into Phase-Segregation and Thermal-Healing Behavior.

Composition engineering of perovskite materials has been demonstrated to be important for high-performance solar cells. Recently, the energy favorable hybridization of formamidinium (FA) and cesium (Cs) in three dimension lead halide perovskites has been attracting increasing attention due to its potential benefit on durability. Herein, we reported a simple and effective method to produce phase-pure CsxFA1-xPbI3 thin film via sequential introduction of cations, in which the FA cation was introduced by interdiffusion annealing in the presence of N-methylimidazole (NMI). NMI was employed as an additive to slow down the crystallization and thus drive the formation of CsxFA1-xPbI3 with micrometer grain size, which probably facilitate the charge dissociation and transportation in photovoltaic devices. More importantly, composition dependent phase-segregation has been revealed and investigated for the first time during the phase-pure mixed-cation perovskites CsxFA1-xPbI3. The present findings demonstrated that suppressing phase-segregation of mixed-cation perovskites by meticulous composition engineering is significant for further development of efficient photovoltaics. It also suggested that phase-pure Cs0.15FA0.85PbI3 may be a promising candidate with superior phase-durability, which performed an efficiency over 16% in planar perovskite solar cells.

A Highly Stretchable and Autonomous Self-Healing Polymer Based on Combination of Pt···Pt and π-π Interactions.

A new self-healing polymer has been obtained by incorporating a cyclometalated platinum(II) complex Pt(C∧ N∧ N)Cl (C∧ N∧ N = 6-phenyl-2,2'-bipyridyl) into a polydimethylsiloxane (PDMS) backbone. The molecular interactions (a combination of Pt···Pt and π-π interactions) between cyclometalated platinum(II) complexes are strong enough to crosslink the linear PDMS polymer chains into an elastic film. The as prepared polymer can be stretched to over 20 times of its original length. When damaged, the polymer can be healed at room temperature without any healants or external stimuli. Moreover, the self-healing is insensitive to surface aging. This work represents the first example where the attractive metallophilic inter-actions are utilized to design self-healing materials. Moreover, our results suggest that the stretchability and self-healing properties can be obtained simultaneously without any conflict by optimizing the strength of crosslinking interactions.

A Stiff and Healable Polymer Based on Dynamic-Covalent Boroxine Bonds.

A stiff and healable polymer is obtained by using the dynamic-covalent boroxine bond to crosslink PDMS chain into 3D networks. The as-prepared polymer is very strong and stiff, and can bear a load of more than 450 times its weight. When damaged, it can be completely healed upon heating after wetting.

Facile and environmentally friendly synthesis of ultrathin nickel hydroxide nanosheets with excellent supercapacitor performances.

In this article, we report a facile and environmentally friendly glutamic acid-assisted hydrothermal strategy for the preparation of ultrathin two-dimensional (2D) ß-Ni(OH)2 nanosheets with a thickness of about 2 nm, which exhibit a maximum specific capacitance of 2537.4 F g(-1) at a current density of 1 A g(-1), even at 10 A g(-1), the specific capacitance is still maintained at 2290.0 F g(-1) with 77.6% retention after 3000 cycles.

A highly stretchable autonomous self-healing elastomer.

It is a challenge to synthesize materials that possess the properties of biological muscles-strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.

A Highly Stretchable Polymer that Can Be Thermally Healed at Mild Temperature.

Combining stretchability and self-healing properties in a man-made material is a challenging task. For an efficient self-healing material, weaker dynamic or reversible bonds should be presented as crosslinks so that they will first break upon damage and then reform after healing, which is not favorable when developing elastic materials. In this work, by incorporating dynamic Fe(III)-triazole coordination bonds into polydimethylsiloxane (PDMS) backbone, a highly elastic polymer is obtained that can be thermally healed at mild temperature. The as-prepared polymer can be stretched to 3400% strain at low loading speed (1 mm min(-1) ). When damaged, the polymer can be thermally healed at 60 °C for 20 h with a healing efficiency of over 90%. The good mechanical and healable properties of this polymer can be ascribed to the unique coordination bond strength and coordination conformation of Fe(III)-triazole coordination complex.

A novel photo-responsive europium(III) complex for advanced anti-counterfeiting and encryption.

A novel europium(iii) complex simultaneously exhibiting photocolorimetric and photofluorometric behavior was obtained. Multiple distinguishable identities can be obtained and reversibly modulated using light as external stimuli. With this novel photo-responsive complex, double encryption and advanced anti-counterfeiting were realized.

Asymmetric Donor-π-Acceptor-Type Benzo-Fused Aza-BODIPYs: Facile Synthesis and Colorimetric Properties.

Novel aza-diisoindolylmethene and their BF2 -chelating complexes (benzo-fused aza-BODIPYs) were synthesized on a large scale and in a facile manner from phthalonitrile in tBuOK-DMF solution. The unique asymmetric donor-π-acceptor structure facilitates B-N bond detachment in the presence of trifluoroacetic acid (TFA) in dichloromethane, resulting in sharp color change from red to colorless, with over 250 nm hypsochromic shift in the absorption maximum. This colorimetric process can be reversed by adding a very small amount of proton-accepting solvents or compounds. A (1) H and (11) B NMR spectroscopy study and also density functional theory (DFT) calculations suggest that TFA-induced B-N bond cleavage may disrupt the whole π-conjugation of the BODIPY molecule, resulting in significant colorimetric behavior.

A self-healing PDMS polymer with solvatochromic properties.

Coordination bonds are effective for constructing functional self-healing materials due to their tunable bond strength and metal-ion-induced functionalities. In this work, we incorporate a cobalt(II) triazole complex into a polydimethylsiloxane (PDMS) matrix. The resulting polymers show solvatochromic behaviour as well as self-healing properties.

Starfish-shaped Co3O4/ZnFe2O4 Hollow Nanocomposite: Synthesis, Supercapacity, and Magnetic Properties.

A novel starfish-shaped porous Co3O4/ZnFe2O4 hollow nanocomposite was fabricated for the first time by a facile and stepwise hydrothermal approach, utilizing metal-organic frameworks as precursors and sacrificial templates. The morphology evolution in the synthetic process upon reaction time and amount of raw materials were investigated in detail. The as-synthesized starfish-shaped porous Co3O4/ZnFe2O4 composites were studied as an electrode material for supercapacitors showing good capacitive performances. Their specific capacitance can reach as high as 326 F g(-1) at 1 A g(-1). The rational combination of components with different potential windows in a composite material enables a wide overall potential range resulting in the highest energy density of 82.5 Wh kg(-1), significantly larger than that of the single components. Magnetic measurements show that the system presents a large coercivity and high squareness (at 1.8 K, Hc = 884 Oe and Mr/Ms = 0.52) with respect to the individual components, which may be attributed to the unique morphology of Co3O4/ZnFe2O4, as well as surface and interface exchange coupling effects. Materials with this novel design and fabrication may show promise for potential applications in electrochemical energy storage and magnetic devices.

Comparison of the electronic and vibrational optical activity of a europium(III) complex.

The geometry and the electronic structure of chiral lanthanide(III) complexes are traditionally probed by electronic methods, such as circularly polarised luminescence (CPL) and electronic circular dichroism (ECD) spectroscopy. The vibrational phenomena are much weaker. In the present study, however, significant enhancements of vibrational circular dichroism (VCD) and Raman optical activity (ROA) spectral intensities were observed during the formation of a chiral bipyridine-Eu(III) complex. The ten-fold enhancement of the vibrational absorption and VCD intensities was explained by a charge-transfer process and the dominant effect of the nitrate ion on the spectra. A much larger enhancement of the ROA and Raman intensities and a hundred-fold increase of the circular intensity difference (CID) ratio were explained by the resonance of the λ = 532 nm laser light with the (7)F0 → (5)D0 transitions. This phenomenon is combined with a chirality transfer, and mixing of the Raman and luminescence effects involving low-energy (7)F states of europium. The results thus indicate that the vibrational optical activity (VOA) may be a very sensitive tool for chirality detection and probing of the electronic structure of Eu(III) and other coordination compounds.

Dumbbell-like Au-Fe3O4 nanoparticles: a new nanostructure for supercapacitors.

Monodispersed dumbbell-like Au-Fe3O4 nanoparticles (NPs) were synthesized and studied for use in supercapacitors. These dumbbell NPs show Au/Fe3O4-size dependent capacitive behaviors and the 7-14 nm Au-Fe3O4 NPs have the best specific capacitance of 464 F g(-1) at 1 A g(-1) and capacity retention of 86.4% after 1000 cycles, much larger than pure Fe3O4 NPs (160 F g(-1) and 72.8% retention). This capacitive enhancement is believed to arise from the Au-induced increase in electron transfer across the dumbbell-like NPs. Thise report demonstrates a new strategy to enhance oxide NP capacitance for applications in high performance supercapacitors.

Potential switchable circularly polarized luminescence from chiral cyclometalated platinum(II) complexes.

A series of chiral cyclometalated platinum(II) complexes, [Pt((-)-L1)(Dmpi)]Cl ((-)-1), [Pt((+)-L1)(Dmpi)]Cl ((+)-1), [Pt((-)-L2)(Dmpi)]Cl ((-)-2), [Pt((+)-L2)(Dmpi)]Cl ((+)-2), [Pt3((-)-L2)2(Dmpi)4](ClO4)4 ((-)-3), and [Pt3((+)-L2)2(Dmpi)4](ClO4)4 ((+)-3) [(-)-L1 = (-)-4,5-pinene-6'-phenyl-2,2'-bipyridine, (+)-L1 = (+)-4,5-pinene-6'-phenyl-2,2'-bipyridine), (-)-L2 = (-)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, (+)-L2 = (+)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, Dmpi = 2,6-dimethylphenyl isocyanide], have been designed and synthesized. In aqueous solutions, (-)-1 and (+)-1 aggregate into one-dimensional helical chain structures through Pt···Pt, π-π, and hydrophobic-hydrophobic interactions. (-)-3 and (+)-3 represent a novel helical structure with Pt-Pt bonds. The formation of helical structures results in enhanced and distinct chiroptical properties as evidenced by circular dichroism spectra. Circularly polarized luminescence (CPL) was observed from the aggregates of (-)-1 and (+)-1 in water, as well as (-)-3 and (+)-3 in dichloromethane. The CPL activity can be switched reversibly (for (-)-1 and (+)-1) or irreversibly (for (-)-3 and (+)-3) by varying the temperature.

Inorganic nanostructured materials for high performance electrochemical supercapacitors.

Electrochemical supercapacitors (ES) are a well-known energy storage system that has high power density, long life-cycle and fast charge-discharge kinetics. Nanostructured materials are a new generation of electrode materials with large surface area and short transport/diffusion path for ions and electrons to achieve high specific capacitance in ES. This mini review highlights recent developments of inorganic nanostructure materials, including carbon nanomaterials, metal oxide nanoparticles, and metal oxide nanowires/nanotubes, for high performance ES applications.

Asymmetrical/symmetrical D-π-A/D-π-D thiazole-containing aromatic heterocyclic fluorescent compounds having the same triphenylamino chromophores.

A family of linear asymmetrical D-π-A and symmetrical D-π-D types of thiazole-based aromatic heterocyclic fluorescent compounds bearing various electron-donating and electron-withdrawing tails (bromo, triphenylamino, pyridyl, thienyl and benzoic acid) have been designed and prepared successfully. Synthetic, structural, thermal, spectral and computational comparisons have been carried out for related compounds because of their adjustable electronic properties. It is interesting to mention that compound 2 can be prepared from 5-bromothiazole by one-pot Suzuki-Miyaura coupling and subsequent C-H activation reactions via a 5-TPA-substituted thiazole intermediate 1. X-ray single-crystal structures of six compounds indicate that they all crystallize in the triclinic P1 space group and the thiazole core exhibits different dihedral angles with its adjacent benzene ring of the triphenylamino group (3.6(3)-40.8(3)°). The photophysical and electrochemical results demonstrate that compound 7 exhibits high electrochemical activity with a green fluorescence emission. Meanwhile, compounds 1, 2, and 6 show high luminescence quantum yields, and compound 8 exhibits excellent thermal stability (T(d(10)) = 503 °C).

A single-molecule magnet based on heptacyanomolybdate with the highest energy barrier for a cyanide compound.

Three trinuclear Mn2Mo molecules based on the orbitally degenerate [Mo(CN)7](4-) anion were prepared, one of which is the first single-molecule magnet (SMM) based on heptacyanomolybdate. The blocking temperature and the energy barrier (U = 40.5 cm(-1)) are records for a cyanide-based SMM. Wide hysteresis loops and sharp quantum tunneling steps were observed from single-crystal measurements.

Circular dichroism spectroscopy study of crystalline-to-amorphous transformation in chiral platinum(II) complexes.

Two couples of enantiomeric platinum(II) complexes: Pt(L1a )Cl (1a), Pt(L1b )Cl (1b) and Pt(L1a )(C ≡ C - Ph) (2a), Pt(L1b )(C ≡ C - Ph) (2b) (L1a = (+)-1,3-di-(2-(4,5-pinene)pyridyl)benzene, L1b = (-)-1,3-di-(2-(4,5-pinene)pyridyl)benzene) were synthesized and characterized. Their absolute configurations were determined by single crystal X-ray diffraction and further verified by circular dichroism (CD) spectra (including electronic circular dichroism [ECD] and vibrational circular dichroism [VCD]). These complexes show interesting mechanoluminescence and/or vapoluminescence due to crystalline-to-amorphous transformation. The crystalline solids, grinding-induced amorphous powders, and vapor-induced amorphous powders of complexes 2a and 2b were comparatively investigated by solid-state ECD and VCD spectra. The transformation from crystalline solids to amorphous powders was accompanied by significant variances of the spectral feature in both ECD and VCD spectra.

Syntheses, photoluminescence, and electroluminescence of a series of iridium complexes with trifluoromethyl-substituted 2-phenylpyridine as the main ligands and tetraphenylimidodiphosphinate as the ancillary ligand.

Five bis-cyclometalated iridium complexes with tifluoromethyl-substituted 2-phenylpyridine (ppy) at different positions of its phenyl group as the main ligands and tetraphenylimidodiphosphinate (tpip) as the ancillary ligand, 2-6 (1 is a trifluoromethyl-free complex), were prepared, and their X-ray crystallography, photoluminescence, and electrochemistry were investigated. The number and positions of trifluoromethyl groups at the phenyl ring of ppy greatly affected the emission spectra of Ir(3+) complexes, and their corresponding emission peaks at 533, 502, 524, 480, and 542 nm were observed at room temperature, respectively. Constructed with complexes 2-6 as the emitters, respectively, the organic light-emitting diodes (OLEDs) with the structure of indium-tin oxide/1,1-bis[4-(di-p-tolylamino)phenyl]cyclohexane (30 nm)/Ir (x wt %):bis[3,5-bis(9H-carbazol-9-yl)phenyl]diphenylsilane (15 nm)/1,3,5-tris(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl (45 nm)/LiF (1 nm)/Al (100 nm) showed good performances. Particularly, device G4 based on 4-trifluoromethyl-substituted complex 4 with x = 8 wt % obtained a maximum luminance of over 39000 cd m(-2) and maximum luminance efficiency (η(L)) and power efficiency (η(p)) of 50.8 cd A(-1) and 29.0 lm W(-1), respectively. The results suggested that all of the complexes 2-6 would have potential applications in OLEDs.

Coplanar bithiazole-centered heterocyclic aromatic fluorescent compounds having different donor/acceptor terminal groups.

A family of stable and soluble bithiazole-centered heterocyclic aromatic fluorescent compounds is described herein. All these multiple N-donor containing compounds have effective π-conjugated systems and different imidazole, pyridine, thiophene, triphenylamino, benzoic acid, and ethyl benzoate tails showing distinguishable D-A-A-D and A-A-A-A structures. X-ray single-crystal structures of seven compounds indicate that all of the bithiazole cores have the same trans coplanar configuration but exhibit different dihedral angles with their adjacent aromatic heterocycles (4.5(6)-69.7(3)°). Optical and electrochemical results demonstrate that the TPA-terminated bithiazole compound 2TPA2TZ has yellow fluorescence and reversible redox activity as well as extraordinarily high thermal stability. Theoretical and experimental studies have been made to reveal the differences from related compounds with adjustable electronic properties. The internal reorganization energy (λ) studies have been carried out to indicate the differences between the bithiazole-based derivatives and the corresponding bithiophene-based counterparts.