Metal-ligand Interactions Research Articles

Designing dynamic metal-coordinated hydrophobically associated mechanically robust and stretchable hydrogels for versatile, multifunctional applications in strain sensing, actuation and flexible supercapacitors

Combining the synergistic effect of dynamic metal–ligand cross-linking and hydrophobic association along with low density chemical cross-linking, we have developed a mechanically robust and stretchable hydrogel that was synthesized by micellar copolymerization of acrylamide (AM), maleic acid (MA) and butyl acrylate monomer. With optimized composition, this hydrogel showed ∼ 3 MPa tensile strength & ∼ 60 MPa compressive strength. The hydrogel is stretchable ∼ 7 times of its original length. These hydrogel materials are flexible and can be folded, bent, and twisted due to their high toughness (∼10 MJ m−3) and low elastic modulus (0.56 MPa). Because of the dynamic nature of metal–ligand interaction and hydrophobic association, the hydrogel showed high energy dissipation under tensile deformation and quick recovery of the dissipated energy after repeated loading and unloading. This hydrogel showed pH responsive mechanical properties. At lower pH, the mechanical strength and elastic modulus of the hydrogel deteriorated due to the dissociation of metal–ligand interaction. This concept was further used for demonstrating shape memory effect in these materials. Utilizing the colorimetric change in presence of Fe3+ and H+, the hydrogel can be used for data encryption-decryption technology. Combining with a thermoresponsive hydrogel (Poly (N-Isopropyl acrylamide)) layer, our hydrogel showed excellent thermoresponsive reversible actuation effect. Furthermore, because of its high ionic conductivity and strain dependent resistance change, the hydrogel can be used as a flexible strain sensor and as a compressible electrolyte in flexible supercapacitor devices.

The Progress and Outlook of Multivalent‐Ion‐Based Electrochromism

Electrochromic technology has witnessed numerous achievements in recent years both in research and commercialization. Electrochromic devices (ECD) based on different electrochemical mechanism have been developed for various applications, ranging from smart windows, thermal management, rear views, display, camouflage, etc. Compared to conventional ECDs based on monovalent charge carriers (e.g., H+, Li+), incorporating multivalent ions with rich electrochemistry, high charge density, and small ionic radius has opened new possibilities in novel ECDs. The merits of multivalent ions are harvested in ECDs activated by ion intercalation/deintercalation (e.g., Zn2+, Al3+, Ca2+, Mg2+), reversible metal electrodeposition (e.g., Cu2+, Bi3+, Zn2+), and dynamic metal–ligand interactions (e.g., Cu2+, Fe2+). Herein, the working mechanism, characteristics, and up‐to‐date achievements in multivalent ECDs are summarized and classified accordingly. The applications of multivalent ECDs for smart windows, energy storage, thermal management, multicolor displays, etc., are exemplified. The issues and challenges encountered by multivalent ECDs are emphasized, and the future directions for developing multivalent ECDs are also summarized. The aim of this review is to inspire more efforts in the exploration and the proliferation of multivalent ECDs.

In vitro biological activities of novel Ni(II)-2-chloroquinoline derivative complex: Synthesis, characterization and computational studies

Quinoline derivative nickel complexes have received considerable attention in biomedical research. Herein, novel nickel(II) complex [Ni(II)(HL)2].2H2O was synthesized from newly synthesised ligand 2-((2-hydroxyethyl)amino)quinoline-3-carbaldehyde (H2L) through bidentate fashion of metal–ligand interaction. The complex was characterized using spectroscopic and physicochemical methods. The formation constant (KNi(II) = 2.36 × 107) of the complex was calculated spectroscopically and thermodynamic parameters (ΔG, ΔH and ΔS) were determined from it. In vitro antibacterial activity analysis of the newly synthesized complex exhibited mean inhibition zones ranging from medium to high (16.55 ± 1.03 mm, 16.69 ± 0.63 and 20.94 ± 2.01 mm) at 600 μg/mL against E. coli, S. aureus and P. aeruginosa, respectively. The complex also showed enhanced antioxidant activities compared with the corresponding free ligand. The energy band gap (1.183 eV) was calculated from the HOMO and LUMO of the most stable structure of the synthesized complex. The DFT calculated results and molecular docking analysis results showed good agreement with the experimental results. The complex showed pronounced biological activities than the free ligand. The in silico binding modes of the complex against E. Coli DNA Gyrase and S. aureus Dihydrofolate reductase (PDB: 2w9h) were found to be in excellent agreement with the in vitro biological studies.

Promotion of thermochromic luminous polysulfone membrane towards smart high-temperature PM2.5 filtration and fire alarming

Particulate matter 2.5 (PM2.5) has become a major threat to human lives. To minimize the adverse effect of high temperature PM2.5, the best way is to alert and filter out the PM2.5 simultaneously. However, it remains a challenge to design filters with combined merits of high-performance, fire-retardancy and thermal response. In this work, we prepare the thermochromic luminous polysulfone membrane with high-temperature PM2.5 filtration and alarming property. The dual luminous center containing covalent donor–acceptor (DA) structure and metal–ligand interaction are incorporated and electrospun into structure unified nanofibers. And different thermal responsiveness is observed for the dual luminous center. The high PM2.5 filtration efficiency (99.1%), low pressure drops (98 Pa) and heat-resistant (Tg > 236 °C) membrane can be directly applied on an in-situ high-temperature PM2.5 filtration and monitoring device, with the emission color variable from red to cyan in a wide range. More importantly, PBN composite filters show excellent flame retardancy in comparison with the commercial PE fabrics, and the color indicating property functions well even under fire. Therefore, the PBN composite membrane holds great potential in the fields of high-temperature PM2.5 filtration and fire alarming.

Alendronate-Functionalized Graphene Quantum Dots as an Effective Fluorescent Sensing Platform for Arsenic Ion Detection.

Alendronate-functionalized graphene quantum dots (ALEN-GQDs) with a quantum yield of 57% were synthesized via a two-step route: preparation of graphene quantum dots (GQDs) by pyrolysis method using citric acid as the carbon source and post functionalization of GQDs via a hydrothermal method with alendronate sodium. After careful characterization of the obtained ALEN-GQDs, they were successfully employed as sensing materials with superior selectivity and sensitivity for the detection of nanomolar levels of arsenic ions (As(III)). According to the mechanistic investigation, arsenic ions can quench the fluorescence intensity of ALEN-GQDs through metal-ligand interaction between the As(III) ions and the surface functional groups of the fluorescent probe. This probe provided a rapid method to monitor As(III) with a wide detection range (44nM-1.30µM) and a low detection limit of 13nM. Finally, to validate the applicability, this novel fluorescent probe was successfully applied for the quantitative determination of As(III) in rice and water samples.

Constructing Ultrastable Metallo-Cages via In Situ Deprotonation/Oxidation of Dynamic Supramolecular Assemblies.

Coordination-driven self-assembly enables the spontaneous construction of metallo-supramolecules with high precision, facilitated by dynamic and reversible metal-ligand interactions. The dynamic nature of coordination, however, results in structural lability in many metallo-supramolecular assembly systems. Consequently, it remains a formidable challenge to achieve self-assembly reversibility and structural stability simultaneously in metallo-supramolecular systems. To tackle this issue, herein, we incorporate an acid-/base-responsive tridentate ligand into multitopic building blocks to precisely construct a series of metallo-supramolecular cages through coordination-driven self-assembly. These dynamic cagelike assemblies can be transformed to their static states through mild in situ deprotonation/oxidation, leading to ultrastable skeletons that can withstand high temperatures, metal ion chelators, and strong acid/base conditions. This in situ transformation provides a reliable and powerful approach to manipulate the kinetic features and stability of metallo-supramolecules and allows for modulation of encapsulation and release behaviors of metallo-cages when utilizing nanoscale quantum dots (QDs) as guest molecules.

Colorimetric Chemosensor for Cu2+ and Fe3+ Based on a meso-Triphenylamine-BODIPY Derivative.

Optical chemosensors are a practical tool for the detection and quantification of important analytes in biological and environmental fields, such as Cu2+ and Fe3+. To the best of our knowledge, a BODIPY derivative capable of detecting Cu2+ and Fe3+ simultaneously through a colorimetric response has not yet been described in the literature. In this work, a meso-triphenylamine-BODIPY derivative is reported for the highly selective detection of Cu2+ and Fe3+. In the preliminary chemosensing study, this compound showed a significant color change from yellow to blue-green in the presence of Cu2+ and Fe3+. With only one equivalent of cation, a change in the absorption band of the compound and the appearance of a new band around 700 nm were observed. Furthermore, only 10 equivalents of Cu2+/Fe3+ were needed to reach the absorption plateau in the UV-visible titrations. Compound 1 showed excellent sensitivity toward Cu2+ and Fe3+ detection, with LODs of 0.63 µM and 1.06 µM, respectively. The binding constant calculation indicated a strong complexation between compound 1 and Cu2+/Fe3+ ions. The 1H and 19F NMR titrations showed that an increasing concentration of cations induced a broadening and shifting of the aromatic region peaks, as well as the disappearance of the original fluorine peaks of the BODIPY core, which suggests that the ligand-metal (1:2) interaction may occur through the triphenylamino group and the BODIPY core.

A light-responsive wound dressing hydrogel: Gelatin based self-healing interpenetrated network with metal-ligand interaction by ferric citrate.

Interpenetrated network (IPN) hydrogels with desired mechanical properties were prepared based on gelatin. A copolymer of dimethyl aminoethyl methacrylate (DMAEMA) with 2-Acrylamido-2-methylpropane sulfonic acid (AMPS) in gelatin was chemically cross-linked with methylene bis acrylamide (MBA) to form a semi-IPN hydrogel. Also, IPN hydrogel is fabricated from the AMPS-co-DMAEMA and gelatin in the presence of ferric ions with both chemical and physical cross-linkers. According to the compression test, the metal-ligand interaction has a remarkable impact on the mechanical strength of hydrogel. Ferric ions caused a decrease in the pores size confirmed by the SEM images of hydrogels, resulting in preserving its mechanical stability during the swelling test due to a more robust structure of hydrogel. Ferric to ferrous ions reduction is observed under visible light irradiation, which results in a light-sensitive hydrogel with a higher rate of biodegradation compared to semi-IPN hydrogels. MTT assay results implied that the synthesized hydrogels are non-toxic for the L-929 cell line. Also, for more detailed investigations, histological studies are conducted as in vivo tests. With regards to the improvements of mechanical properties harnessed in IPN hydrogels by ferric ions along with the extraordinary self-healing capability, IPNs would be considered an appropriate option for tissue engineering.

Identifying And Unveiling the Role of Multivalent Metal States for Bidirectional UOR and HER Over Ni, Mo-Trithiocyanuric Based Coordination Polymer.

Urea oxidation reaction (UOR), an ideal alternative to oxygen evolution reaction (OER), has received increasing attention for realizing energy-saving H2 production and relieving pollutant degradation. Normally, most studied Ni-based UOR catalysts pre-oxidate to NiOOH and then act as active sites. However, the unpredictable transformation of the catalyst's structure and its dissolution and leaching, may complicate the accuracy of mechanism studies and limit its further applications. Herein, a novel self-supported bimetallic Mo-Ni-C3 N3 S3 coordination polymers (Mo-NT@NF) with strong metal-ligand interactions and different H2 O/urea adsorption energy are prepared, which realize a bidirectional UOR/hydrogen evolution reaction (HER) reaction pathway. A series of Mo-NT@NF is prepared through a one-step mild solvothermal method and their multivalent metal states and HER/UOR performance relationship is evaluated. Combining catalytic kinetics, in situ electrochemical spectroscopic characterization, and density-functional theory (DFT) calculations, a bidirectional catalytic pathway is proposed by N, S-anchored Mo5+ and reconstruction-free Ni3+ sites for catalytic active center of HER and UOR, respectively. The effective anchoring of the metal sites and the fast transfer of the intermediate H* by N and S in the ligand C3 N3 S3 H3 further contribute to the fast kinetic catalysis. Ultimately, the coupled HER||UOR system with Mo-NT@NF as the electrodes can achieve energy-efficient overall-urea electrolysis for H2 production.

Fabrication of Highly Thermally Resistant and Self-Healing Polysiloxane Elastomers by Constructing Covalent and Reversible Networks.

The fabrication of self-healing elastomers with high thermal stability for use in extreme thermal conditions such as aerospace remains a major challenge. A strategy for preparing self-healing elastomers with stable covalent bonds and dynamic metal-ligand coordination interactions as crosslinking sites in polydimethylsiloxane (PDMS) is proposed. The added Fe (III) not only serves as the dynamic crosslinking point at room temperature which is crucial for self-healing performance, but also plays a role as free radical scavenging agent at high temperatures. The results show that the PDMS elastomers possessed an initial thermal degradation temperature over 380°C and a room temperature self-healing efficiency as high as 65.7%. Moreover, the char residue at 800°C of PDMS elastomer reaches 7.19% in nitrogen atmosphere, and up to 14.02% in air atmosphere by doping a small amount (i.e., 0.3 wt%) of Fe (III), which is remarkable for the self-healing elastomers that contain weak and dynamic bonds with relatively poor thermal stability. This study provides an insight into designing self-healing PDMS-based materials that can be targeted for use as high-temperature thermal protection coatings.

Seamlessly Adhesive Bionic Periosteum Patches Via Filling Microcracks for Defective Bone Healing.

Current artificial designs of the periosteum focus on osteogenic or angiogenic properties, while ignoring the filling and integration with bone microcracks, which trigger a prolonged excessive inflammatory reaction and lead to failure of bone regeneration. In this study, seamless adhesive biomimetic periosteum patches (HABP/Sr-PLA) were prepared to fill microcracks in defective bone via interfacial self-assembly induced by Sr ions mediated metal-ligand interactions among pamidronate disodium-modified hyaluronic acid (HAPD), black phosphorus (BP), and hydrophilic polylactic acid (PLA). In vitro, HABP/Sr-PLA exhibited excellent self-healing properties, seamlessly filled bone microcracks, and significantly enhanced osteogenesis and angiogenesis. Furthermore, in a rat cranial defect model, HABP/Sr-PLA was demonstrated to significantly promote the formation of blood vessels and new bone under mild 808 nm photothermal stimulation (42.8 °C), and the highest protein expression of CD31 and OPN was five times higher than that of the control group and other groups. Therefore, the proposed seamless microcrack-filled bionic periosteum patch is a promising clinical strategy for promoting bone repair.

What Determines If a Ligand Undergoes Coordination or Catalytic Activation on a Metal Cluster?

We report a joint experimental and theoretical study on the reactivity of Agn+ clusters with H2S, D2O, and NH3. Complete dehydrogenation products are observed for Agn+ reacting with H2S, but no dehydrogenation products are found for D2O or NH3 under the same reaction condition. Theoretical calculations elucidate why Agn+ clusters show different reactivities with these inorganic hydrides. NH3 shows strong coordination with Agn+, but the dehydrogenation reactions are unfavorable; in contrast, the fragile H-S bonds and stable AgnS+ products facilitate the hydrogen evolution of H2S on Agn+. We fully analyzed the metal-ligand interactions of Agn+ clusters with three molecules and illustrated the reaction dynamics and charge-transfer interactions and altered the superatomic states during the formation of cluster sulfides. We expect this study to benefit the design of stable environmentally friendly desulfurization catalysts and also the understanding of the mechanism on ligand-protected metal clusters in wet chemistry.

Cu(II) and Mn(II) Anchored on Functionalized Mesoporous Silica with Schiff Bases: Effects of Supports and Metal-Ligand Interactions on Catalytic Activity.

New series of Cu(II) and Mn(II) complexes with Schiff base ligands derived from 2-furylmethylketone (Met), 2-furaldehyde (Fur), and 2-hydroxyacetopheneone (Hyd) have been synthesized in situ on SBA-15-NH2, MCM-48-NH2, and MCM-41-NH2 functionalized supports. The hybrid materials were characterized by X-ray diffraction, nitrogen adsorption-desorption, SEM and TEM microscopy, TG analysis, and AAS, FTIR, EPR, and XPS spectroscopies. Catalytic performances were tested in oxidation with the hydrogen peroxide of cyclohexene and of different aromatic and aliphatic alcohols (benzyl alcohol, 2-methylpropan-1-ol, and 1-buten-3-ol). The catalytic activity was correlated with the type of mesoporous silica support, ligand, and metal-ligand interactions. The best catalytic activity of all tested hybrid materials was obtained in the oxidation of cyclohexene on SBA-15-NH2-MetMn as a heterogeneous catalyst. No leaching was evidenced for Cu and Mn complexes, and the Cu catalysts were more stable due to a more covalent interaction of the metallic ions with the immobilized ligands.

Nanoimaging of Facet-Dependent Adsorption, Diffusion, and Reactivity of Surface Ligands on Au Nanocrystals.

Analysis of the influence of dissimilar facets on the adsorption, stability, mobility, and reactivity of surface ligands is essential for designing ligand-coated nanocrystals with optimal functionality. Herein, para-nitrothiophenol and nitronaphthalene were chemisorbed and physisorbed, respectively, on Au nanocrystals, and the influence of different facets within a single Au nanocrystal on ligands properties were identified by IR nanospectroscopy measurements. Preferred adsorption was probed on (001) facets for both ligands, with a lower density on (111) facets. Exposure to reducing conditions led to nitro reduction and diffusion of both ligands toward the top (111) facet. Nitrothiophenol was characterized with a diffusivity higher than that of nitronaphthalene. Moreover, the strong thiol-Au interaction led to the diffusion of Au atoms and the formation of thiol-coated Au nanoparticles on the silicon surface. It is identified that the adsorption and reactivity of surface ligands were mainly influenced by the atomic properties of each facet, while diffusion was controlled by ligand-metal interactions.

Metal-Ligand Interactions and Their Roles in Controlling Nanoparticle Formation and Functions.

ConspectusFunctional nanoparticles (NPs) have been studied extensively in the past decades for their unique nanoscale properties and their promising applications in advanced nanosciences and nanotechnologies. One critical component of studying these NPs is to prepare monodisperse NPs so that their physical and chemical properties can be tuned and optimized. Solution phase reactions have provided the most reliable processes for fabricating such monodisperse NPs in which metal-ligand interactions play essential roles in the synthetic controls. These interactions are also key to stabilizing the preformed NPs for them to show the desired electronic, magnetic, photonic, and catalytic properties. In this Account, we summarize some representative organic bipolar ligands that have recently been explored to control NP formation and NP functions. These include aliphatic acids, alkylphosphonic acids, alkylamines, alkylphosphines, and alkylthiols. This ligand group covers metal-ligand interactions via covalent, coordination, and electrostatic bonds that are most commonly employed to control NP sizes, compositions, shapes, and properties. The metal-ligand bonding effects on NP nucleation rate and growth can now be more thoroughly investigated by in situ spectroscopic and theoretical studies. In general, to obtain the desired NP size and monodispersity requires rational control of the metal/ligand ratios, concentrations, and reaction temperatures in the synthetic solutions. In addition, for multicomponent NPs, the binding strength of ligands to various metal surfaces needs to be considered in order to prepare these NPs with predesigned compositions. The selective ligand binding onto certain facets of NPs is also key to anisotropic growth of NPs, as demonstrated in the synthesis of one-dimensional nanorods and nanowires. The effects of metal-ligand interactions on NP functions are discussed in two aspects, electrochemical catalysis for CO2 reduction and electronic transport across NP assemblies. We first highlight recent advances in using surface ligands to promote the electrochemical reduction of CO2. Several mechanisms are discussed, including the modification of the catalyst surface environment, electron transfer through the metal-organic interface, and stabilization of the CO2 reduction intermediates, all of which facilitate selective CO2 reduction. These strategies lead to better understanding of molecular level control of catalysis for further catalyst optimization. Metal-ligand interaction in magnetic NPs can also be used to control tunneling magnetoresistance properties across NPs in NP assemblies by tuning NP interparticle spacing and surface spin polarization. In all, metal-ligand interactions have yielded particularly promising directions for tuning CO2 reduction selectivity and for optimizing nanoelectronics, and the concepts can certainly be extended to rationalize NP engineering at atomic/molecular precision for the fabrication of sensitive functional devices that will be critical for many nanotechnological applications.

An Outlook into the Magnetic and Magnetocaloric Properties of Cr1.3Fe0.7O3

Herein, the magnetic and magnetocaloric properties of Cr1.3Fe0.7O3 particles are presented. The structural and oxidation states of the samples are confirmed from the X‐ray diffraction and X‐ray photoemission spectroscopy measurements. In addition, the thermomagnetization experiments reveal the coexistence of two spin reorientation, Morin transition, as well as Néel temperature below 300 K. Such complex magnetic behavior of the system can be ascribed to the metal–ligand–metal interaction caused both by Cr3+ and Fe3+ magnetic ions. The maximum magnetic entropy change estimated from the isothermal magnetization measurements is 0.056 J kg−1 K−1 at 41 K for an external magnetic‐field change of 70 kOe.

Eco-friendly PVA-LYS fibers for gold nanoparticle recovery from water and their catalytic performance.

In this work, we grafted lysine on PVA electrospun fibers, using a green preparation technique. The resulting fiber mats were proposed for gold nanoparticles (AuNPs) removal from water. The efficiency of three fibers with different lysine amounts (10, 20, and 30%) was investigated. The incorporation of amino groups in PVA fibers was firstly proved by FTIR, SEM, and elemental analysis, confirming the presence of lysine. Among the three different fibers, PVA-LYS 30% has shown the best removal efficiency, reaching 65%, at pH equal to 5. Adsorption isotherms were studied and showed that the Langmuir model is the best model fitting our experimental results, with a maximum adsorption capacity of 20.1mgg-1. Metal-ligand interactions and electrostatic attraction between protonated amino groups of lysine on the fibers and negatively charged, citrate capped, AuNPs are the main proposed mechanisms for AuNP adsorption on the fibers. Sustainability of AuNPs adsorbed on these fibers has been checked through their reuse as catalyst for the reduction of 4-nitrophenol to 4-aminophenol. The process was completed within 60min, and their reusability showed more than 99% efficiency after 5 reduction cycles. Our results prove that green PVA-LYS fibers can extract nanoparticles from water, as low cost-effective and eco-friendly adsorbent, and contribute to the promotion of a circular economy approach, through their reuse as catalyst in the reduction of pollutants.

Heat-Resistant and Color-Changing Luminescent Polysulfone for Information Encryption and Fire Alarming.

An intrinsic difficulty with thermally responsive photoluminescent materials is that high temperatures usually destroy luminance due to the notorious thermal quenching effect. Limited by the vulnerable chemical structure and soft skeleton, most of the existing photoluminescent responsive materials fail to indicate or work at a surging temperature over 100 °C, thus limiting application in display and alarming in harsh conditions. Herein, enlightened by chameleon's adaptive nature to external stimulus, we introduce a topologically optimized electron donor-acceptor (DA) structure and supramolecular interactions of lanthanide ions into the polymer backbone. The emission color determined by the DA structure is stable at high temperatures, and metal-ligand interaction phosphorescence is temperature-adjustable. Owing to the excellent reproducibility and heat resistance of composite films, the sensors can be bent into different three-dimensional structures and adhered to metal surfaces as flexible thermometers with superior display resolution. The polymer composite film could be directly applied as a photoluminescent quick response (QR) code, with patterns simultaneously variable to a temperature from 30 to 150 °C free of manual operation. More importantly, the polymeric composite could be in-situ-oxidized to a "sulfone" structure with an enhanced glass transition temperature of 297-304 °C. The heat- and flame-resistant characteristics of the oxidized films give rise to the application of fire alarming devices since it can locate the fire source and respond exactly depending on the distance from the fire. The unique display, encryption, and alarming functions of the polymeric composite studied in this work bring forward a new concept of developing a great information security and disaster monitoring system with the application of temperature-responsive materials.

Metal-Assembled Collagen Peptide Microflorettes as Magnetic Resonance Imaging Agents

Magnetic resonance imaging (MRI) is a medical imaging technique that provides detailed information on tissues and organs. However, the low sensitivity of the technique requires the use of contrast agents, usually ones that are based on the chelates of gadolinium ions. In an effort to improve MRI signal intensity, we developed two strategies whereby the ligand DOTA and Gd(III) ions are contained within Zn(II)-promoted collagen peptide (NCoH) supramolecular assemblies. The DOTA moiety was included in the assembly either via a collagen peptide sidechain (NHdota) or through metal-ligand interactions with a His-tagged DOTA conjugate (DOTA-His6). SEM verified that the morphology of the NCoH assembly was maintained in the presence of the DOTA-containing peptides (microflorettes), and EDX and ICP-MS confirmed that Gd(III) ions were incorporated within the microflorettes. The Gd(III)-loaded DOTA florettes demonstrated higher intensities for the T1-weighted MRI signal and higher longitudinal relaxivity (r1) values, as compared to the clinically used contrast agent Magnevist. Additionally, no appreciable cellular toxicity was observed with the collagen microflorettes loaded with Gd(III). Overall, two peptide-based materials were generated that have potential as MRI contrast agents.

Versatile metallo-supramolecular polymeric interphase for highly reversible zinc metal anodes

The instability of the zinc anode stemming from dendrite growth and water-induced parasitic reactions involving hydrogen evolution and spontaneous corrosion has severely hampered the practical application of aqueous zinc metal batteries. The repetitive formation and extinction of zinc dendrites, in particular, can induce dynamic volume fluctuation in zinc anodes, resulting in coulombic inefficiency and a limited cycle lifespan. Herein, we describe a design concept that utilizes dynamic metal-ligand interactions to construct a robust metallo-supramolecular interphase crosslinked by Zn(II)-2,6-bis(1,2,3-triazol-4-yl)pyridines moieties to stabilize the Zn plating/stripping. The designed metallo-supramolecular interphase with a dynamically crosslinked network can not only substantially enhance mechanical resilience to dissipate the plating/stripping-induced stress, but also simultaneously selectively transports Zn2+ cations and facilitates the desolvation process via the dynamic coordinated hopping mechanism. Meanwhile, this chemically inert and hydrophobic metallo-supramolecular interphase can significantly reduce water-induced side reactions by blocking electrolyte permeation. Consequently, such an ultrathin (≈230 nm) interphase layer enables stable Zn plating/stripping for 1200 h at a high current density of 10 mA cm−2 and a capacity of 1 mAh cm−2 in symmetric cells. Furthermore, an improved cycling stability can be attained for Zn//MnO2 full cells.