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.

Colloidal Organometal Halide Perovskite (MAPbBrxI3-x, 0≤x≤3) Quantum Dots: Controllable Synthesis and Tunable Photoluminescence.

Organic-inorganic perovskite materials, typically methylammonium lead trihalide (MAPbX3: MA = methylammonium; X = Br, I), are recently attract enormous attention for their distinguished photo-electronic properties. The control of morphology, composition and dispersability of MAPbX3 perovskite nanocrystals is crucial for the property tailoring and still a major challenge. Here we report the synthesis of colloidal MAPbBrxI3-x(0 ≤ x ≤ 3) nanocrystals at room temperature by using alkyl carboxylate as capping ligands. These nanocrystals exhibit continuously tunable UV-vis absorption and photoluminescence (PL) across the visible spectrum, which is attributed to the quantum confinement effect with certain stoichiometry. Their unique exciton recombination dynamics was investigated and discussed.

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.

Finely tuning MOFs towards high performance in C2H2 storage: synthesis and properties of a new MOF-505 analogue with an inserted amide functional group.

Aiming to improve the acetylene (C2H2) storage capability of MOFs, we successfully designed NJU-Bai 17, a new analogue of MOF-505 with an inserted amide functional group which exhibits almost record high C2H2 uptakes of 222.4 cm(3) g(-1) at 296 K and 296 cm(3) g(-1) at 273 K under 1 bar. This result has been further supported by the determination of the heat of C2H2 adsorption and Grand Canonical Monte Carlo (GCMC) and first-principle calculations.

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.

The Utilization of Amide Groups To Expand and Functionalize Metal-Organic Frameworks Simultaneously.

A new stepwise ligand-elongation strategy by amide spacers is utilized to prepare isoreticularly high-porous metal-organic frameworks (MOFs), namely, quasi-mesoporous [Cu2 (PDBAD)(H2 O)]n (H4 PDBAD=5,5'-((4,4'-((pyridine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis(azanediyl))diisophthalic acid; NJU-Bai22: NJU-Bai for Nanjing University Bai's group), and mesoporous [Cu2 (PABAD)(H2 O)]n (H4 PABAD=5,5'-((4,4'-((4,4'-((pyridine-3,5-dicarbonyl)bis(azanediyl))bis(benzoyl))bis (azanediyl))bis(benzoyl))bis(azanediyl))diisophthalic acid; NJU-Bai23). Compared with the prototypical MOF of [Cu2 (PDAD)(H2 O)]n (H4 PDAD=5,5'-(pyridine-3,5-dicarbonyl)bis(azanediyl)diisophthalic acid; NJU-Bai21, also termed as PCN-124), both MOFs exhibit almost the same CO2 adsorption enthalpy and CO2 selectivity values, and better capacity for CO2 storage under high pressure; these results make them promising candidate materials for CO2 capture and sequestration. Interestingly, this new method, in comparison with traditional strategies of using phenyl or triple-bond spacers, is easier and cheaper, resulting in a better ability to retain high CO2 affinity and selectivity in MOFs with large pores and high CO2 storage capacity. Additionally, it may lead to the high thermal stability of the MOFs and also their tolerance to water, which is related to the balance between the density of functional groups and pore sizes. Therefore, this strategy could provide new opportunities to explore more functionalized mesoporous MOFs with high performance.

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.

Finely tuning MOFs towards high-performance post-combustion CO2 capture materials.

CO2 capture science and technology, particularly for the post-combustion CO2 capture, has become one of very important research fields, due to great concern of global warming. Metal-organic frameworks (MOFs) with a unique feature of structural fine-tunability, unlike the traditional porous solid materials, can provide many and powerful platforms to explore high-performance adsorbents for post-combustion CO2 capture. Until now, several strategies for finely tuning MOF structures have been developed, in which either the larger quadrupole moment and polarizability of CO2 are considered: metal ion change (I), functional groups attachment (II) and functional group insertion (III), vary the electronic nature of the pore surface; or targeting the smaller kinetic diameter of CO2 over N2 is focused on: framework interpenetration (IV), ligand shortening (V) and coordination site shifting (VI) contract the pore size of frameworks to improve their CO2 capture properties. In this review, from the viewpoint of synthetic materials scientists/chemists, we would like to introduce and summarize these strategies based upon recent work published by other groups and ourselves.

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.

Synthesis of copper micro-rods with layered nano-structure by thermal decomposition of the coordination complex Cu(BTA)2.

Porous metallic copper was successfully prepared by a simple thermal decomposition strategy. A coordination compound of Cu(BTA)2 with the morphology of micro-rod crystal was synthesized as the precursor. The precursor to copper transformation was performed and annealed at 600°C with the shape preserved. The copper micro-rods are assembled from unique thin lamellar layers, each with the thickness of approximately 200 nm and nano-pores of approximately 20 to 100 nm. This morphology is highly related to the crystal structure of the precursor. The mechanism of the morphology formation is proposed, which would be able to offer a guideline toward porous metals with controllable macro/micro/nano-structures by the precursor crystal growth and design.

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.

Type-II core-shell Si-CdS nanocrystals: synthesis and spectroscopic and electrical properties.

Type-II Si-CdS core-shell colloidal nanocrystals (NCs) are synthesized with the spectroscopic and electronic properties tuned by the thickness of the CdS shell.