Search

Metal ions are ubiquitous in nature and play significant roles in assembling functional materials in fields spanning chemistry, biology, and materials science. Metal-phenolic materials are assembled from phenolic components in the presence of metal ions through the formation of metal-organic complexes. Alkali, alkali-earth, transition, and noble metal ions as well as metalloids interacting with phenolic building blocks have been widely exploited to generate diverse hybrid materials. Despite extensive studies on the synthesis of metal-phenolic materials, a comprehensive summary of how metal ions guide the assembly of phenolic compounds is lacking. A fundamental understanding of the roles of metal ions in metal-phenolic materials engineering will facilitate the assembly of materials with specific and functional properties. In this review, we focus on the diversity and function of metal ions in metal-phenolic material engineering and emerging applications. Specifically, we discuss the range of underlying interactions, including (i) cation-π, (ii) coordination, (iii) redox, and (iv) dynamic covalent interactions, and highlight the wide range of material properties resulting from these interactions. Applications (e.g., biological, catalytic, and environmental) and perspectives of metal-phenolic materials are also highlighted.

The intrinsic hypoxic tumor microenvironment and limited accumulation of photosensitizers (PSs) result in unsatisfied efficiency of photodynamic therapy (PDT). To enhance the PDT efficiency against solid tumors, a functional oxygen self-supplying and PS-delivering nanosystem is fabricated via the combination of catalase (CAT), chlorin e6 (Ce6) and metal-phenolic network (MPN) capsule. It is demonstrated that the CAT encapsulated in the capsules (named CCM capsules) could catalyze the degradation of hydrogen peroxide (H2O2) to produce molecular oxygen (O2), which could be converted into cytotoxicity reactive oxygen species (ROS) by surface-loaded Ce6 under 660 nm laser irradiation, leading to synergistic anticancer effects in vitro and in vivo. Therefore, the application of CCM capsule could be a promising strategy to improve PDT effectiveness.

Background:The caries patterns of the first permanent molars (FPMs) among schoolchildren had not been adequately evaluated, and researchers paid no attention to the distributions of fully-erupted FPMs number and proportion in Shenzhen children.Objective:To quantitatively assess the eruption stages and dental caries patterns of the FPMs for the total students as well as the subgroups.Methods:A 3-year school-based epidemiological investigation was undertaken by dentists to examine the eruption stages and dental caries patterns of the FPMs, involved the second-grade students from 132 primary schools in Baoan District of Shenzhen, China.Results:Among 95809 schoolchildren aged 6–8 years, 86.51% individuals had fully erupted the Tooth #16, 87.15% for #26, 89.30% for #36, and 88.81% for #46 (c2=475.033,Pvs78.43%;Pc2=3322.810,Pvs25.68%;PConclusions:Most schoolchildren aged 6–8 years have fully erupted the FPMs, with a relatively high prevalence of FPMs caries in Shenzhen.

The biomolecular corona that forms on particles upon contact with blood plays a key role in the fate and utility of nanomedicines. Recent studies have shown that precoating nanoparticles with serum proteins can improve the biocompatibility and stealth properties of nanoparticles. However, it is not fully clear how precoating influences biomolecular corona formation and downstream biological responses. Herein, we systematically examine three precoating strategies by coating bovine serum albumin (single protein), fetal bovine serum (FBS, mixed proteins without immunoglobulins), or bovine serum (mixed proteins) on three nanoparticle systems, namely supramolecular template nanoparticles, metal-phenolic network (MPN)-coated template (core-shell) nanoparticles, and MPN nanocapsules (obtained after template removal). The effect of protein precoating on biomolecular corona compositions and particle-immune cell interactions in human blood was characterized. In the absence of a pre-coating, the MPN nanocapsules displayed lower leukocyte association, which correlated to the lower amount (by 2-3 fold) of adsorbed proteins and substantially fewer immunoglobulins (more than 100 times) in the biomolecular corona relative to the template and core-shell nanoparticles. Among the three coating strategies, FBS precoating demonstrated the most significant reduction in leukocyte association (up to 97% of all three nanoparticles). A correlation analysis highlights that immunoglobulins and apolipoproteins may regulate leukocyte recognition. This study demonstrates the impact of different precoating strategies on nanoparticle-immune cell association and the role of immunoglobulins in bio-nano interactions.

Supramolecular complexation is a powerful strategy for engineering materials in bulk and at interfaces. Metal-phenolic networks (MPNs), which are assembled through supramolecular complexes, have emerged as suitable candidates for surface and particle engineering owing to their diverse properties. Herein, we examine the supramolecular dynamics of MPNs during thermal transformation processes. Changes in the local supramolecular network including enlarged pores, ordered aromatic packing, and metal relocation arise from thermal treatment in air or an inert atmosphere, enabling the engineering of metal-oxide networks (MONs) and metal-carbon networks, respectively. Furthermore, by integrating photo-responsive motifs (i.e., TiO2 ) and silanization, the MONs are endowed with reversible superhydrophobic (>150°) and superhydrophilic (≈0°) properties. By highlighting the thermodynamics of MPNs and their transformation into diverse materials, this work offers a versatile pathway for advanced materials engineering.

Engineering coatings with precise physicochemical properties allows for control over the interface of a material and its interactions with the surrounding environment. However, assembling coatings with well-defined properties on different material classes remains a challenge. Herein, we report a co-assembly strategy to precisely control the structure and properties (e.g., thickness, adhesion, wettability, and zeta potential) of coatings on various materials (27 substrates examined) using quinone and polyamine building blocks. By increasing the length of the amine building blocks from small molecule diamines to branched amine polymers, we tune the properties of the films, including the thickness (from ca. 5 to ca. 50 nm), interfacial adhesion (0.05 to 5.54 nN), water contact angle (130 to 40°), and zeta potential (-42 to 28 mV). The films can be post-functionalized through the in situ formation of diverse nanostructures, including nanoparticles, nanorods, and nanocrystals. Our approach provides a platform for the rational design of engineered, substrate-independent coatings for various applications.

Developing materials with programmable permeability for cargo encapsulation and release is challenging but important in a number of fields including drug delivery and sensing. Metal–phenolic networ...

Functional coatings are of considerable interest because of their fundamental implications for interfacial assembly and promise for numerous applications. Universally adherent materials have recently emerged as versatile functional coatings; however, such coatings are generally limited to catechol, (ortho-diphenol)-containing molecules, as building blocks. Here, we report a facile, biofriendly enzyme-mediated strategy for assembling a wide range of molecules (e.g., 14 representative molecules in this study) that do not natively have catechol moieties, including small molecules, peptides, and proteins, on various surfaces, while preserving the molecule's inherent function, such as catalysis (≈80 % retention of enzymatic activity for trypsin). Assembly is achieved by in situ conversion of monophenols into catechols via tyrosinase, where films form on surfaces via covalent and coordination cross-linking. The resulting coatings are robust, functional (e.g., in protective coatings, biological imaging, and enzymatic catalysis), and versatile for diverse secondary surface-confined reactions (e.g., biomineralization, metal ion chelation, and N-hydroxysuccinimide conjugation).

Nanoengineered capsules encapsulated with functional cargos (e.g., enzymes) are of interest for various applications including catalysis, bioreactions, sensing, and drug delivery. Herein, we report a facile strategy to engineer enzyme-encapsulated metal-phenolic network (MPN) capsules using enzyme-loaded zeolitic imidazolate framework nanoparticles (ZIF-8 NPs) as templates, which can be removed in a mild condition (e.g., ethylenediaminetetraacetic acid (EDTA) solution). The capsule size (from 250 nm to 1 μm) and thickness (from 9.8 to 33.7 nm) are well controlled via varying the template size and coating time, respectively. Importantly, MPN capsules encapsulated with enzymes (i.e., glucose oxidase) can trigger the intracellular cascade reaction via the exhaustion of glucose to produce H2O2 and subsequently generate toxic hydroxyl radicals (•OH) based on the Fenton reaction via the reaction between H2O2 and iron ions in MPN coatings. The intracellular cascade reaction for the generation of •OH is efficient to inhibit cancer cell viability, which is promising for the application in chemodynamic therapy.

The tunable growth of metal-organic materials has implications for engineering particles and surfaces for diverse applications. Specifically, controlling the self-assembly of metal-phenolic networks (MPNs), an emerging class of metal-organic materials, is challenging, as previous studies suggest that growth often terminates through kinetic trapping. Herein, kinetic strategies were used to temporally and spatially control MPN growth by promoting self-correction of the coordinating building blocks through oxidation-mediated MPN assembly. The formation and growth mechanisms were investigated and used to engineer films with microporous structures and continuous gradients. Moreover, reactive oxygen species generated by ultrasonication expedite oxidation and result in faster (ca. 30 times) film growth than that achieved by other MPN assembly methods. This study expands our understanding of metal-phenolic chemistry towards engineering metal-phenolic materials for various applications.

Selective self-assembly in multicomponent mixtures offers a method for isolating desired components from complex systems for the rapid production of functional materials. Developing approaches capable of selective assembly of "target" components into intended three-dimensional structures is challenging because of the intrinsically high complexity of multicomponent systems. Herein, we report the selective coordination-driven self-assembly of metal-phenolic networks (MPNs) from a series of complex multicomponent systems (including crude plant extracts) into thin films via metal chelation with phenolic ligands. The metal (FeIII) selectively assembles low abundant phenolic components (e.g., myricetrin and quercetrin) from plant extracts into thin films. This selective metal-phenolic assembly is independent of the substrate properties (e.g., size, surface charge, and shape). Moreover, the high selectivity is consistent across different target phenolic ligands in model mixtures, even though each individual component can form thin films from single-component systems. A computational simulation of film formation suggests that the driving force for the selective behavior stems from differences in the number of chelating sites in the phenolic structures. The MPN films are shown to demonstrate improved antioxidant properties compared with the corresponding phenolic compounds in their free form, therefore exhibiting potential as free-standing antioxidant films.

Deposition of dopamine and tannic acid has received great attention in the fields of surface and interface science and technology. The deposition behaviors of various metal–phenolic systems have been investigated, and it is generally accepted that at least one catechol group is essential to the formation of the coatings. Herein, we report a novel and effective surface-coating system based on the coordination complexes of FeIII ions with a natural product juglone that contains only one phenolic hydroxyl. We investigated the deposition behaviors of this novel system on various substrates. Microporous polypropylene membrane modified with juglone/FeIII coatings is superhydrophilic and underwater superoleophobic, showing high separation efficiency and good reusability for various oil/water emulsions. In addition, the modified membrane can adsorb anionic dyes and selectively remove them from dye mixtures with high efficiency. We further demonstrated that the coating is a result of the synergetic effect of juglo...

Janus membranes (JMs) with opposite wettability have brought about new opportunities to tackle the challenging issues encountered in oil/water separation. However, these achievements suffer from empirical availability for the separation of oil-in-water emulsions, lacking a controllable way to tune the synergistic effect of asymmetric configurations, which is the “inner” driving force for practical performance. Herein, the role of the asymmetric configuration is theoretically and experimentally demonstrated in the Janus structural design, membrane fabrication, and separation performance for oil-in-water emulsions. These significant insights are particularly gained by analyzing Young–Laplace capillary pressures, measuring the adhesive forces between the oil and membrane surface, and monitoring the demulsification and oil transportation processes. Fluorescence imaging has been used to in situ visualize the separation process and then a mechanism is firstly proposed as demulsification followed by rapid unidirectional oil transportation for surfactant-stabilized oil-in-water emulsions. The two successive processes are strongly governed by the controllable asymmetric configuration of the JMs. An efficient oil separation can, therefore, be achieved from surfactant-stabilized oil-in-water emulsions with a wide size distribution (from nanometers to microns) by optimizing these two stages via tuning the hydrophilic/hydrophobic configuration and surface charge property of the JMs. Therefore, this work is expected to yield a design principle and guideline for developing JMs with applicability in the practical separation of oil-in-water emulsions.

The manipulation of interfacial properties has broad implications for the development of high-performance coatings. Metal-phenolic networks (MPNs) are an emerging class of responsive, adherent materials. Herein, host-guest chemistry is integrated with MPNs to modulate their surface chemistry and interfacial properties. Macrocyclic cyclodextrins (host) are conjugated to catechol or galloyl groups and subsequently used as components for the assembly of functional MPNs. The assembled cyclodextrin-based MPNs are highly permeable (even to high molecular weight polymers: 250-500 kDa), yet they specifically and noncovalently interact with various functional guests (including small molecules, polymers, and carbon nanomaterials), allowing for modular and reversible control over interfacial properties. Specifically, by using either hydrophobic or hydrophilic guest molecules, the wettability of the MPNs can be readily tuned between superrepellency (>150°) and superwetting (ca. 0°).

Hybrid conformal coatings, such as metal-phenolic networks (MPNs) that are constructed from the coordination-driven assembly of natural phenolic ligands, are of interest in areas including biomedicine, separations, and energy. To date, most MPN coatings have been prepared by immersing substrates in solutions containing the phenolic ligands and metal ions, which is a suitable method for coating small or flexible objects. In contrast, more industrially relevant methods for coating and patterning large substrates, such as spray assembly, have been explored to a lesser extent toward the fabrication of MPNs, particularly regarding the effect of process variables on MPN growth. Herein, a spray assembly method was used to fabricate MPN coatings with various phenolic building blocks and metal ions and their formation and patterning were explored for different applications. Different process parameters including solvent, pH, and metal-ligand pair allowed for control over the film properties such as thickness and roughness. On the basis of these investigations, a potential route for the formation of spray-assembled MPN films was proposed. Conditions favoring the formation of bis complexes could produce thicker coatings than those favoring the formation of mono or tris complexes. Finally, the spray-assembled MPNs were used to generate superhydrophilic membranes for oil-water separation and colorless films for UV shielding. The present study provides insights into the chemistry of MPN assembly and holds promise for advancing the fabrication of multifunctional hybrid materials.

It is highly desirable to develop environmentally friendly processes for fabricating thin-film composite (TFC) nanofiltration membranes (NFMs) from natural materials. However, the nanofiltration performance of such TFC NFMs is not satisfactory for practical applications owing to the lack of efficient methods for constructing ultrathin, uniform, stable coatings as selective layers. In this study, a contra-diffusion strategy is used to fabricate TFC NFMs with ultrathin cross-linked alginate coatings as selective layers without the use of any organic solvents. The as-prepared NFMs show a water permeation flux that is nearly one order of magnitude higher than that of other alginate-based TFC NFMs with similar salt rejection, and represents the best performance among all TFC NFMs from natural materials. These NFMs also demonstrate excellent mono-/divalent ion selectivity, as well as good long-term operation stability and antifouling properties. Furthermore, this strategy maximizes the reactant usage rate, minimizes the waste discharge and provides new insight into environmentally friendly fabrication of TFC NFMs.

Ultrathin perforated honeycomb-patterned membranes show promise for high-resolution separation, in which the mechanical strength and chemical stability of membranes are very important. Here we report facile and versatile modification methods for preparing cross-linked honeycomb membranes with tunable mechanical and chemical properties. Commercially available polystyrene-b-polyisoprene-b-polystyrene (SIS), which contains double bonds for post modification, together with an amphiphilic block copolymer was utilized as the membrane-forming material. Robust and self-standing honeycomb membranes were obtained by the rapid vapor diffusion cross-linking of S2Cl2 in 5 min. X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDX) results demonstrate effective cross-linking. The cross-linked membranes show excellent resistance to organic solvents and other harsh environments. Water flux measurements indicate that the cross-linked membranes can endure trans-membrane pressure as high as 0.12 MPa. The cross-linked membranes are stable in a wide temperature range. Another cross-linking method based on thiol–ene click chemistry is also proved to be able to form robust membranes with both improved stabilities and controllable surface properties. Moreover, the cross-linked perforated honeycomb membranes can be used for separation under higher operation pressure.

The molecular weight distribution (MWD) of polymers shows effects on their phase separation, crystallization, self-assembly, and mechanical properties. It is well known that the architecture of polymers plays a crucial role in the self-assembly of patterned porous films via the breath figure method. However, the effect of MWD is still unknown. In this work, we synthesized a series of hydroxyl-end-functionalized polystyrenes with a narrow MWD by atom transfer radical polymerization (ATRP). MWD was further broadened by mixing the polystyrenes. Honeycomb-patterned porous films were prepared from the polystyrenes. For a unimodal distributed sample with a wide MWD, the optimal concentration for patterned film formation is expanded. However, an improvement cannot be observed in bimodal distributed polymers. The high heterogeneity of the bimodal system weakens the cooperation of components with different molecular weights in stabilizing water droplets. Furthermore, it is interesting to note that the stiffness of patterned porous films can be enhanced by tuning the MWD. The present study demonstrates the effects of the MWD of polymers on the self-assembly behaviors, providing new insights into the breath figure process and the design of robust patterned porous films.

Supraparticles (SPs) assembled from smaller colloidal nanoparticles can serve as depots of therapeutic compounds and are of interest for long-term, sustained drug release in biomedical applications. However, a key challenge to achieving temporal control of drug release from SPs is the occurrence of an initial rapid release of the loaded drug (i.e., "burst" release) that limits sustained release and potentially causes burst release-associated drug toxicity. Herein, a biocoating strategy is presented for silica-SPs (Si-SPs) to reduce the extent of burst release of the loaded model protein lysozyme. Specifically, Si-SPs were coated with a fibrin film, formed by enzymatic conversion of fibrinogen into fibrin. The fibrin-coated Si-SPs, FSi-SPs, which could be loaded with 7.9 ± 0.9 μg of lysozyme per SP, released >60% of cargo protein over a considerably longer period of time of >20 days when compared with the uncoated Si-SPs that released the same amount of the cargo protein, however, within the first 3 days. Neurotrophins that support the survival and differentiation of neurons could also be loaded at ∼7.3 μg per SP, with fibrin coating also delaying neurotrophin release (only 10% of cargo released over 21 days compared with 60% from Si-SPs). In addition, the effects of incorporating a hydrogel-based system for surgical delivery and the opportunity to control drug release kinetics were investigated-an alginate-based hydrogel scaffold was used to encapsulate FSi-SPs. The introduction of the hydrogel further extended the initial release of the encapsulated lysozyme to ∼40 days (for the same amount of cargo released). The results demonstrate the increasing versatility of the SP drug delivery platform, combining large loading capacity with sustained drug release, that is tailorable using different modes of controlled delivery approaches.

Deposition of dopamine and tannic acid has received great attention in the fields of surface and interface science and technology. The deposition behaviors of various metal-phenolic systems have been investigated, and it is generally accepted that at least one catechol group is essential to the formation of the coatings. Herein, we report a novel and effective surface-coating system based on the coordination complexes of Fe

Polydopamine-based coatings are fabricated via an electric field-accelerating and -directing codeposition process of polydopamine with charged polymers such as polycations, polyanions, and polyzwitterions. The coatings are uniform and smooth on various substrates, especially on those adhesion-resistant materials including poly(vinylidene fluoride) and poly(tetrafluoroethylene) membranes. Moreover, this electric field-directed deposition method can be applied to facilely prepare Janus membranes with asymmetric chemistry and wettability.

We report a completely green and one-step protocol to fabricate selective layers for thin film composite nanofiltration membranes via the laccase-triggered co-deposition of natural tea catechins and chitosan. The constructed membranes show around 99% rejection of Na2SO4 with a high water permeation flux of 45 L m−2 h−1 under 0.6 MPa.

We describe here a facile and robust approach to conformal and non-conformal surface modification by tuning the wetting transition between the Wenzel state and the Cassie state. Highly ordered honeycomb-patterned porous films were prepared from a diblock copolymer by the breath figure method, and pincushion-like surfaces were obtained by removing the top surface layer of honeycomb films. It is found that the surface modification is highly dependent on the pre-wetting process. After complete pre-wetting, polydopamine (PDA) and polyetherimide (PEI) deposit both inside and outside of the pores, and thus the whole honeycomb film surface becomes hydrophilic. Water droplets on the surfaces transform from a Cassie state to a Wenzel state after 6–12 h PDA/PEI deposition, during which the apparent water contact angles decrease from above 90° (e.g., 115°) to below 90° (e.g., 55°). If the honeycomb-patterned porous films are not pre-wetted, PDA/PEI deposit only on the external surfaces, forming a top layer covering the pores, and the pore walls are not modified. This approach provides a versatile route for controlling water spreading and impregnation behaviors on patterned porous films, which will be useful in fields such as microreactors, supercapacitors, and wearable electronics.

Targeted drug delivery remains at the forefront of biomedical research but remains a challenge to date. Herein, we describe the first super-assembly of nanosized metal–organic polyhedra (MOP) and their biomimetic coatings of lipid bilayers to synergistically combine the advantages of micelles and supramolecular coordination cages for targeted drug delivery. The super-assembly technique affords unique hydrophobic features that endow individual MOP to act as nanobuilding blocks and enable their super-assembly into larger and well-defined nanocarriers with homogeneous sizes over a broad range of diameters. Various cargos were controllably loaded into the MOP with high payloads, and the nanocages were then super-assembled to form multi-drug delivery systems. Additionally, functional nanoparticles were introduced into the super-assemblies via a one-pot process for versatile bioapplications. The MOP super-assemblies were surface-engineered with epidermal growth factor receptors and could be targeted to cancer cells. In vivo studies indicated the assemblies to have a substantial circulation half-life of 5.6 h and to undergo renal clearance – characteristics needed for nanomedicines.

In this paper, we report novel superhydrophobic surfaces with tunable water adhesion by combining mussel-inspired surface chemistry and bioinspired multiscale surface structures. Highly ordered honeycomb porous films were prepared from a diblock copolymer polystyrene-block-poly(N,N-dimethylaminoethyl methacrylate) by the breath figure method. Removing the top surface layer of the honeycomb films leads to pincushion-like surfaces. The films were coated with polydopamine after completely prewetting by ethanol, followed by the reaction with 1H,1H,2H,2H-perfluorodecanethiol for fluorination. As a result of the surface modification, both the honeycomb and the pincushion-like surfaces are superhydrophobic with a water contact angle higher than 150°. Interestingly, the former is highly adhesive, on which water droplets are pinned at any tilted angles, whereas the latter is relatively low adhesive. Calculations indicate that the honeycomb films are in the Cassie state, whereas the pincushion-like surfaces are in ...

Droplet bouncing on repellent solid surfaces (e.g., the lotus leaf effect) is a common phenomenon that has aroused interest in various fields. However, the scenario of a droplet bouncing off another droplet (either identical or distinct chemical composition) while moving on a solid material (i.e., ricocheting droplets, droplet billiards) is scarcely investigated, despite it having fundamental implications in applications including self‐cleaning, fluid transport, and heat and mass transfer. Here, the dynamics of bouncing collisions between liquid droplets are investigated using a friction‐free platform that ensures ultrahigh locomotion for a wide range of probing liquids. A general prediction on bouncing droplet–droplet contact time is elucidated and bouncing droplet–droplet collision is demonstrated to be an extreme case of droplet bouncing on surfaces. Moreover, the maximum deformation and contact time are highly dependent on the position where the collision occurs (i.e., head‐on or off‐center collisions), which can now be predicted using parameters (i.e., effective velocity, effective diameter) through the concept of an effective interaction region. The results have potential applications in fields ranging from microfluidics to repellent coatings., Droplets colliding and ricocheting on super‐repellent surfaces display dynamics consistent with droplet–surface collisions, but with tunable dynamics between bouncing droplets via control over the angle of incidence. Parameters introduced using the concept of an effective interaction region allow for a universal description and prediction of droplet bouncing dynamics, with implications for wetting characteristics of next‐generation surfaces.

Micro/nanostructured surfaces with designable wettability show great promise in many fields. This paper reports a new strategy for fabricating superhydrophobic surfaces with tunable water adhesion force by combining multiscale surface structures and mussel-inspired surface chemistry, which can be used for multiple liquid manipulations. Highly ordered porous films prepared by the breath figure method enable convenient construction of surfaces with honeycomb-patterned or nanosized pincushion-like structures. Multiple liquid manipulations including no-loss transportation of water droplets, water collection, programmable movement of water droplets, and chemical reaction monitoring are demonstrated on the micro/nanostructured surfaces. The proposed method is facile, energy-efficient, and can be conducted for the preparation of superhydrophobic surfaces with high contrast adhesion patterns.