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Two anthryl-functionalized cyanide-bridged [Fe4Co4] cube complexes, [(pzTp)Fe(CN)3Co(TpEtOAn)]4[OTf]4·8MeCN·7Et2O (1) and [NEt4]3[(pzTp)Fe(CN)3Co(TpEtOAn)]4[OTf]7·5MeCN·2Et2O (2) (pzTp− = tetrapyrazolylborate, TpEtOAn = 2,2,2-tris-(pyrazol-1-yl)ethoxy(9-methyl-anthracene)), were synthesized and characterized. The crystallographic study revealed that the [Fe4Co4] cubes are arranged into a linear supramolecular chain through significant anthryl–anthryl π–π stacking interactions in complex 1, whereas a zigzag supramolecular 1D assembly is observed in 2. The magnetic measurements showed that both compounds exhibited incomplete transitions from the paramagnetic {Fe IIILS (μ-CN)Co IIHS } state to the diamagnetic {Fe IILS (μ-CN)Co IIILS } state at about 200 K. The luminescence measurement of 1 in solution revealed an enhancement of the emission upon dilution or addition of perfluoronaphthalene (PFN) molecules, which could be attributed to the suppression of the aggregation-caused quenching (ACQ) effect, suggesting possible aggregation of the cube units in the solution. [ABSTRACT FROM AUTHOR]

In this article, we report the synthesis of a MOF containing multiple C＝C bonds geometrical features by adjusting the reactant ratio of the synthetic system. The photochemical addition studies revealed that the ligand 1,4-bis[2-(4-pyridyl)ethenyl]benzene can undergo photoisomerization under UV irradiation, and the angle between the C＝C bonds can be changed by about 85°, so that the C＝C pairs that do not conform to Schmidt's rule can be transformed into the conforming state, and then the 2 + 2 photoaddition can occur. We found that the angle range suitable for photoaddition includes not only the 0–15° range, but also the potential 85 ± 15° range. Furthermore, it is not the C＝C pair that best conforms to Schmidt's rule that gives priority to the photoaddition, but the one that enables the lowest total energy in the crystal to occur. [ABSTRACT FROM AUTHOR]

Side-chain functional groups have been shown to not only ensure solubility but also influence molecular packing behavior, and side-chain modification is an important strategy in the optimization of photovoltaic performance. Instead of focusing on the size of the alkyl side chains, we have investigated the influence of side-chain configurations on the properties of acceptors and organic solar cells (OSCs). Two acceptor molecules, BTIC-TCl-b and BTIC-TCl-l were designed by changing the linear configuration of alkyl chain substituents on thiophene rings to a branched structure. The results show that the branched configuration of the side-chain can significantly improve the planarity and reduce the π⋯π distances, leading to a more compact 3D-network structure. With the polymer donor PBDB-TF, an outstanding power conversion efficiency (PCE) of 16.17% was achieved by BTIC-TCl-b , which is significantly higher than that found with BTIC-TCl-l. Our study offers new insights for side-chain modification, regulation of the aggregation state, and optimization of photovoltaic performance. [ABSTRACT FROM AUTHOR]

Urease is a nickel-containing oligomer that can be used to catalyze the decomposition of urea. Free urease is unstable and prone to inactivation, whereas the immobilization of urease improves its resistance to environmental changes. A green and harmless cyclodextrin polymer (CDP) that has a network structure and excellent modifiability was selected for the immobilization of urease. Citric acid cross-linked CDP (CACDP) is oxidized by sodium periodate to obtain the aldehyde-functionalized dialdehyde CDP (DACDP). Urease is covalently bound to the CDP through a Schiff base reaction between the amino groups and aldehyde groups on DACDP to obtain urease-immobilized CDP (UrCDP). A series of characterization methods and urea-removal experiments confirmed the successful immobilization of urease on the polymer and thus the good removal effect. The maximum removal capacities of UrCDP34-6, UrCDP34-4, and UrCDP34-2 for urea are 145.7 mg g−1, 242.9 mg g−1 and 291.1 mg g−1, respectively. Urea-removal experiments at different temperatures and pH values proved that UrCDP maintains its catalytic activity in response to environmental changes. At the same time, a simple continuous-flow treatment device proved that UrCDP has the clear ability to continuously remove urea. This effective urease-immobilization and urea-removal method is experimentally proven and envisions potential applications in medical and wastewater treatment. [ABSTRACT FROM AUTHOR]

AgNbO3-based antiferroelectric films have attracted emerging attention in the field of dielectric energy storage and possess promising applications in photocatalysis and microwave devices. Unfortunately, it remains a challenge to fabricate pure-phase AgNbO3 films on Si substrates, precluding their further integration into electronic devices. Here, we, for the first time, report phase-pure AgNbO3 films on Pt/Ti/SiO2/Si substrates by a chemical solution deposition (CSD) method. A facile CSD route without using the hazardous pyridine additive is demonstrated to obtain a stable AgNbO3 precursor for spin-coating films. By comprehensively controlling the heat treatment conditions, secondary phases are eliminated in the deposited films. The phase transitions of the AgNbO3 films are also investigated, where intriguingly the room temperature phase is determined to be the antiferroelectric M2 phase, rather than the commonly reported M1 phase in bulk AgNbO3. Meanwhile, the relative dielectric permittivity surpasses 300 at room temperature and maintains at ∼400 with low dielectric loss (<0.05; measured at frequencies of 0.1–1 MHz) over a wide temperature range of 150–350 °C, within a 5% variation. This work provides an easy-to-implement process of AgNbO3 films which may attract scientific interests and potential applications. [ABSTRACT FROM AUTHOR]

A novel strategy to fabricate bilayer hydrogel actuators based on the asymmetric distribution of crystalline regions across the bilayer structures was proposed. By employing PVA polymer chains into an alkali solvent-derived chitosan hydrogel matrix, chitosan/PVA hybrid bilayer hydrogels with both excellent responsive bending and mechanical properties were obtained as pH-controlled manipulators. In the design, the chitosan/PVA hydrogels upon treatment with freeze-thawing cycles were taken as the first monolayer, where excessive crystalline regions appeared. The original chitosan/PVA hydrogel as the second monolayer was then integrated into one bilayer device through the chemical-crosslinking of epichlorohydrin at the interface. The results showed that the resultant chitosan/PVA bilayer hydrogel actuator with a weight ratio of 3 : 1 displayed better sensitivity upon exposure to stimuli. The actuation behaviors are strongly dependent on experimental parameters such as the pH, PVA content and the chemical-crosslinking density. It is proposed that the driving force originates from the asymmetric distribution of crystalline regions, thus resulting in differential swelling ratios between the monolayers. In addition, programmable 3D shape transformations were achieved by using the bilayer hydrogel with designed 2D geometric patterns, and the tailored gripper-like hydrogel actuator can successfully capture and transport the cargo. Moreover, this actuation behavior can be erased and re-written on demand under certain conditions. Taking advantage of this universal strategy, more attractive actuators derived from synthetic or natural polymers in combination with PVA are highly expected, which can be used as smart soft robots in various fields such as manipulators, grippers, and cantilever sensors. [ABSTRACT FROM AUTHOR]

Treatment of CoCl2·6H2O and tris(pyrazolyl-1-yl)borate tricyanoiron(III) anions at an elevated temperature (55 °C) afforded two less-common pearl-chain-like compounds, {[(TpR)Fe(CN)3CoCl2]2Co(DMF)4}·nDMF (1, TpR = Tp4-Me = hydridotris(4-methylpyrazol-1-yl)borate, n = 1 and 2, TpR = Tp*Me = hydridotris(3,4,5-trimethylpyrazol-1-yl)borate, n = 4.5), in which the 4-coordinate Co(II) ions and [(TpR)FeIII(CN)3]− units are alternately bridged by cyanide groups into squares, which are further linked with the 6-coordinate Co(II) ions into an infinite chain. Interestingly, the magnetic study revealed that 1 exhibits a typical single-chain magnet behaviour with an effective energy barrier of 28.0 K, while surprisingly no Glauber dynamics was observed for 2 despite their very similar structures. The variations of the local coordination environments of the cobalt ions and the cyanide linkages were evidenced, and they may account for the significant difference in their magnetic properties related to the global magnetic anisotropy and magnetic exchange of the chain. [ABSTRACT FROM AUTHOR]

Ferroelectric films can sustain large strain induced by substrate constraints, which may additionally modulate their crystal structures and electrical properties. This study revealed the strain engineering effect on the piezoelectricity of (100-x)%Bi1/2Na1/2TiO3-x%BaTiO3 (BNT-BTx) epitaxial films grown on Nb:SrTiO3100 (NSTO100) substrates in association with the crystal structure affected by film thickness. Several compositions in the BNT-BTx system, i.e. BNT-BT2, BNT-BT6 and BNT-BT15, were studied as typical representatives of ferroelectric rhombohedral, relaxor ferroelectric pseudo-cubic (near morphotropic phase boundary) and ferroelectric tetragonal structures, respectively. It was found that a monoclinic–rhombohedral phase transition appeared in BNT-BT2 films when we changed the film thickness, which was caused by the coherent strain imposed by the substrates. The 3-layer BNT-BT2 film (∼150 nm) exhibited a phase coexistence of monoclinic and rhombohedral phases, so that the effective piezoelectric constant was enhanced by at least 260% compared to films with pure monoclinic or rhombohedral phases. The present work may offer a feasible way to improve the piezoelectric properties of other perovskite piezoelectric films. [ABSTRACT FROM AUTHOR]

At present, the clinical strategies for treating chronic wounds are limited, especially when it comes to pain relief and rapid wound healing. Therefore, there is an urgent need to develop alternative treatment methods. This paper provides a systematic review on recent researches on how electrospun nanofiber scaffolds promote wound healing and how the electrospinning technology has been used for fabricating multi-dimensional, multi-pore and multi-functional nanofiber scaffolds that have greatly promoted the development of wound healing dressings. First, we provide a review on the four stages of wound healing, which is followed by a discussion on the evolvement of the electrospinning technology, what is involved in electrospinning devices, and factors affecting the electrospinning process. Finally, we present the possible mechanisms of electrospun nanofibers to promote wound healing, the classification of electrospun polymers, cell infiltration favoring fiber scaffolds, antibacterial fiber scaffolds, and future multi-functional scaffolds. Although nanofiber scaffolds have made great progress as a type of multi-functional biomaterial, major challenges still remain for commercializing them in a way that fully meets the needs of patients. [ABSTRACT FROM AUTHOR]

Thrombin plays an important role in the blood coagulation cascade and it stimulates the process of platelet aggregation. Herein, we developed a highly efficient and sensitive phosphorescent aptasensor system for the quantitative analysis of thrombin. The phosphorescence of 3-mercaptopropionic acid capped Mn-doped ZnS quantum dots (MPA-Mn:ZnS QDs) was gradually quenched with the addition of thrombin binding aptamers-BHQ2 (TBA-BHQ2) based on phosphorescence resonance energy transfer (PRET). With the addition of the target analyte thrombin into the system, TBA-BHQ2 could change its spatial structure from a random coil to an antiparallel G-quadruplex which resulted from the combination of thrombin and TBA-BHQ2, leading to the phosphorescence recovery. Finally, the concentration of thrombin could be accurately determined by means of measuring the phosphorescence intensity change value (ΔP). The limit of detection (LOD) was obtained as low as 15.26 pM with wide linear ranges both from 60 to 2000 pM and from 2 to 900 nM. The proposed strategy was also successfully applied for thrombin detection in human serum samples and plasma samples with satisfactory recoveries from 96% to 99% and 95% to 104%, respectively. The long lifetime of phosphorescent QDs possessed a suitable time delay to eliminate autofluorescence and scattered light interference from biological matrices effectively. Thus, the signal to noise ratio of the phosphorescent aptasensor was improved visibly for the analysis of target analytes. [ABSTRACT FROM AUTHOR]

The detection of phosphate (Pi) under physiological conditions is a very important issue in environmental and biological sciences. Herein, a unique fluorescent probe {[EuL(H2O)1.35(DMF)0.65]·1.9DMF}n (1) was prepared through the organic–inorganic hybridization between asymmetrical tricarboxylate ligands and Eu2O2 clusters under solvothermal conditions. The as-prepared sample 1 exhibited excellent fluorescence properties and could be designed as a self-calibrating fluorescent probe for sensitively and selectively detecting Pi which served as an essential substance in aquatic ecosystems and biological systems. The different responses of the two emission peaks caused by the addition of Pi resulted in a continuous fluorescence color change, which could be clearly observed with the naked eye under UV light lamp illumination at 302 nm. Typically, a good linearity existed between the ratio of dual fluorescence intensities and the Pi contents ranging from 0.1 μM to 15 μM with a low detection limit of 52 nM (S/N = 3). It is noteworthy that the prepared self-calibrating fluorescent probe displayed specific recognition towards Pi anions with satisfactory recovery ranging from 92.8% to 100.6% in water samples and biological fluids. Thus, we can envision that this work may open a new avenue for the detection of many other bioactive ions in environmental and biological samples. [ABSTRACT FROM AUTHOR]

As an emerging class of fluorescent probes, metal–organic frameworks (MOFs) have recently received great interest owing to their fascinating functional properties, intriguing tunable structures, high selectivity and good sensitivity. Herein, we present a novel strategy based on the application of a facile water-stable MOF {[Cd(μ3-abtz)·2I]}n (Abtz–CdI2–MOF, abtz = 1-(4-aminobenzyl)-1,2,4-triazole) using powerful solvo-thermal synthetic techniques, which can serve as an “off–on” fluorescent switch for the label-free detection of dopamine (DA) without any additional surface modification and functionalization. The fluorescence signal of Abtz–CdI2–MOF can be efficiently quenched by KMnO4, and then restored by DA in an “off–on” mode. The possible quenching mechanism should be static quenching resulting from the ground state recombination between Abtz–CdI2–MOF and MnO4−. Further when DA is added, MnO4− can be gradually released from the hybrid system, and bring about ground state complex decomposition, which is triggered by competitive interactions between Abtz–CdI2–MOF and the reduced iodine ions. Therefore, the fluorescence signal can be gradually turned “on”. The relative intensity of restored fluorescence is proportional to the concentration of DA in the wide linear range of 0.25–50 μM with a low detection limit of 57 nM (S/N = 3). Additionally, some potentially foreign interfering substances, such as ascorbic acid (AA) and uric acid (UA), glucide, amino acids and metal ions did not affect DA determination significantly. The proposed strategy was also successfully applied for DA determination in biological samples with satisfactory recoveries from 94.5% to 102%. [ABSTRACT FROM AUTHOR]

Six families of new lanthanide coordination polymers, [Ln2(L)6(H2O)2]n·3nH2O (Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Yb (9)), [Pr2(L)2(ox)2(H2O)4]n·9nH2O (10), [Pr2(L)2(glu)2(H2O)2]n (11), [Er2(L)2(glu)2]n (12), [Nd2(L)2(adip)2]n (13), [Ln2(L)2(1,2-bdc)2(H2O)2]n (Ln = Eu (14), Gd (15), Er (16)), (HL = 4′-(2-carboxyphenyl)-4,2′:6′,4′′-terpyridine, H2ox = oxalic acid, H2glu = glutaric acid, H2adip = adipic acid, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid) were synthesized under hydrothermal conditions and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compounds 1–9 are isomorphic 1D chain structures based on binuclear Ln(iii) units. Compound 10 is a 1D chain, where L− ligands dangle on two sides of the Pr-ox zigzag chain. Compounds 11 and 12 exhibit distinct 2D-layer structures consisting of Ln2(COO)4 binuclear units. Compound 13 displays an appealing 3D network structure, where the auxiliary ligand H2adip plays a significant role in the self-assembly process. Compounds 14–16 present a 1D-chain structure which is extended to a 2D-supramolecular framework by means of weak interactions. The diverse structures further verify the potential of HL ligand in the preparation of coordination polymers with new structures and properties. The effects of auxiliary ligands and coordination modes of HL ligand on the crystal architectures are discussed. The solid-state luminescence and thermal stabilities of compounds 1–16 also were studied. Based on the luminescent properties, we have designed and constructed successfully a series of doped-lanthanide MOF by adjusting the co-doping ratio of Eu(iii) and Tb(iii) into the same framework as that of 1–9. Interestingly, the luminescent colors of the Eu(iii)-doped Tb(iii) compounds can be tuned with change of excitation wavelength. Moreover, white-light emission was achieved on excitation at 330 nm. [ABSTRACT FROM AUTHOR]

Double-shelled hollow microspheres of LiMn2O4were prepared by a facile self-template method. The inner and outer shells of the obtained microspheres are composed of nanoparticles with diameters ranging between 200–400 nm. Galvanostatic charge/discharge cycling shows that this material delivers a discharge capacity of 127 mAh g−1at C/10 rate and a capacity retainability of 80% after 800 cycles at 5 C rate, revealing a high reversible capacity, superior rate capability and excellent cycling stability under high rates. The improved performance is attributed to the short Li+ion diffusion lengths in the nanobuilding blocks and the void core and space between the inner and outer shells to accommodate the volume expansion/contraction during Li+ions insertion/extraction processes. [ABSTRACT FROM AUTHOR]

The modulation of two-dimensional metal-organic framework (2-D MOF) nanosheet stacking is an effective means to improve the properties and promote the application of nanosheets in various fields. Here, we employed a series of alcohol guest molecules (MeOH, EtOH and PrOH) to modulate Zr-BTB (BTB = benzene-1,3,5-tribenzoate) nanosheets and to generate untwisted stacking. The distribution of stacking angles was statistically analyzed from high-angle annular dark-field (HAADF) and fast Fourier transform (FFT) images. The ratios of untwisted stacking were calculated, such as 77.01% untwisted stacking for MeOH, 83.45% for EtOH, and 85.61% for PrOH. The obtained untwisted Zr-BTB showed good separation abilities for different substituted benzene isomers, superior para selectivity and excellent column stability and reusability. Control experiments of 2-D Zr-TCA (TCA = 4,4',4''-tricarboxytriphenylamine) and Zr-TATB (TATB = 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tribenzoic acid) nanosheets with similar pore sizes and stronger polarity regulated by the alcohol guests exhibited moderate separation performance. The electron microscopy images revealed that polar alcohol regulation dominantly generated the twisted stacking of Zr-TCA and Zr-TATB with various Moiré patterns. Polar guest molecules, such as alcohols, provide strong host-guest interactions during the regulation of MOF nanosheet stacking, providing an opportunity to design new porous Moiré materials with application prospects., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

A novel strategy to fabricate bilayer hydrogel actuators based on the asymmetric distribution of crystalline regions across the bilayer structures was proposed. By employing PVA polymer chains into an alkali solvent-derived chitosan hydrogel matrix, chitosan/PVA hybrid bilayer hydrogels with both excellent responsive bending and mechanical properties were obtained as pH-controlled manipulators. In the design, the chitosan/PVA hydrogels upon treatment with freeze-thawing cycles were taken as the first monolayer, where excessive crystalline regions appeared. The original chitosan/PVA hydrogel as the second monolayer was then integrated into one bilayer device through the chemical-crosslinking of epichlorohydrin at the interface. The results showed that the resultant chitosan/PVA bilayer hydrogel actuator with a weight ratio of 3 : 1 displayed better sensitivity upon exposure to stimuli. The actuation behaviors are strongly dependent on experimental parameters such as the pH, PVA content and the chemical-crosslinking density. It is proposed that the driving force originates from the asymmetric distribution of crystalline regions, thus resulting in differential swelling ratios between the monolayers. In addition, programmable 3D shape transformations were achieved by using the bilayer hydrogel with designed 2D geometric patterns, and the tailored gripper-like hydrogel actuator can successfully capture and transport the cargo. Moreover, this actuation behavior can be erased and re-written on demand under certain conditions. Taking advantage of this universal strategy, more attractive actuators derived from synthetic or natural polymers in combination with PVA are highly expected, which can be used as smart soft robots in various fields such as manipulators, grippers, and cantilever sensors.

Thrombin plays an important role in the blood coagulation cascade and it stimulates the process of platelet aggregation. Herein, we developed a highly efficient and sensitive phosphorescent aptasensor system for the quantitative analysis of thrombin. The phosphorescence of 3-mercaptopropionic acid capped Mn-doped ZnS quantum dots (MPA-Mn:ZnS QDs) was gradually quenched with the addition of thrombin binding aptamers-BHQ2 (TBA-BHQ2) based on phosphorescence resonance energy transfer (PRET). With the addition of the target analyte thrombin into the system, TBA-BHQ2 could change its spatial structure from a random coil to an antiparallel G-quadruplex which resulted from the combination of thrombin and TBA-BHQ2, leading to the phosphorescence recovery. Finally, the concentration of thrombin could be accurately determined by means of measuring the phosphorescence intensity change value (ΔP). The limit of detection (LOD) was obtained as low as 15.26 pM with wide linear ranges both from 60 to 2000 pM and from 2 to 900 nM. The proposed strategy was also successfully applied for thrombin detection in human serum samples and plasma samples with satisfactory recoveries from 96% to 99% and 95% to 104%, respectively. The long lifetime of phosphorescent QDs possessed a suitable time delay to eliminate autofluorescence and scattered light interference from biological matrices effectively. Thus, the signal to noise ratio of the phosphorescent aptasensor was improved visibly for the analysis of target analytes.