A Dendrimer‐Based Electropolymerized Microporous Film: Multifunctional,Reversible, and Highly Sensitive Fluorescent Probe

A dendrimer PYTPAG2 composed of a central pyrene “core” and four exterior “arms” capped with electroactive triphenylamine is developed as an electroactive precursor to prepare fluorescent films through electropolymerization (EP). The fluorescence emission comes from the central pyrene “core” and the steric hindrance of the exterior “arms” is beneficial for the formation of microporous morphology. The stable and highly cross‐linked fluorescent EP films can be obtained even as free‐standing films. Further, these dendrimer EP films are first studied as the multifunctional fluorescent probe: the emission of EP films exposed to trinitrotoluene vapor is quenched by 82% in 120 s; while the fluorescence is increased to nearly 400% in 120 s upon exposure to benzene vapor, EP films also act as the fluorescent sensor to Fe³⁺ in solution and the limit of detection is obtained to be 8.5 × 10^?8 m . All the above detection processes exhibit remarkable reversibility. These excellent performances are attributed to both the specific molecular features of PYTPAG2 and the intrinsic properties of EP films.     

Toward High Performance Thiophene‐Containing Conjugated Microporous Polymer Anodes for Lithium‐Ion Batteries through Structure Design

Poly(thiophene) as a kind of n‐doped conjugated polymer with reversible redox behavior can be employed as anode material for lithium‐ion batteries (LIBs). However, the low redox activity and poor rate performance for the poly(thiophene)‐based anodes limit its further development. Herein, a structure‐design strategy is reported for thiophene‐containing conjugated microporous polymers (CMPs) with extraordinary electrochemical performance as anode materials in LIBs. The comparative study on the electrochemical performance of the structure‐designed thiophene‐containing CMPs reveals that high redox‐active thiophene content, highly crosslinked porous structure, and improved surface area play significant roles for enhancing electrochemical performances of the resulting CMPs. The all‐thiophene‐based polymer of poly(3,3′‐bithiophene) with crosslinked structure and a high surface area of 696 m² g^?1 exhibits a discharge capacity of as high as 1215 mAh g^?1 at 45 mA g^?1, excellent rate capability, and outstanding cycling stability with a capacity retention of 663 mAh g^?1 at 500 mA g^?1 after 1000 cycles. The structure–performance relationships revealed in this work offer a fundamental understanding in the rational design of CMPs anode materials for high performance LIBs.     

Advanced Applications and Challenges of Electropolymerized Conjugated Microporous Polymer Films

Conjugated microporous polymers (CMPs) are a unique class of porous materials that have an integrated π-conjugated system and permanent intrinsic porosity. They are of great interest because of their outstanding performance in gas sorption, photoredox catalysis, energy storage, organic light-emitting diodes (OLEDs), and sensing applications. However, conventional chemically synthesized CMPs are solid powders and have poor solubility, which makes it difficult to process and integrate devices, and has become a bottleneck preventing their practical applications. Electropolymerization (EP) is a simple and efficient method for the preparation of CMP films, which simultaneously completes material synthesis and film processing. More importantly, the microstructure of the CMP films can be effectively controlled by electrochemical parameters. In this review, first, the basic synthetic principles and strategies of CMP films via EP are introduced, allowing for facile optimization of the structure and properties. Then, the recent progress of the EP CMP films is focused upon in organic electronics, energy storage, sensors, chemical capture and separation, and electrocatalysts. Finally, the challenges and outlook for EP CMP films are addressed.     

Necklace‐like Nitrogen‐Doped Tubular Carbon 3D Frameworks for Electrochemical Energy Storage

The design and synthesis of a necklace‐like nitrogen‐doped tubular carbon (NTC) are presented by growing microporous polyhedral ZIF‐8 particles and a uniform layer of ZIF‐8 on sacrificial ZnO tetrapods (ZTPs). Oxygen vacancies together with defect regions on the surface of the ZTPs result in the formation of ZIF‐8 polyhedra in conjunction with a very thin shell. This necklace‐like NTC structure has a high N content, very large surface area, ultrahigh microporosity, and quite high electrical conductivity. NTC‐based symmetrical supercapacitor and zinc‐ion capacitor (ZIC) devices are fabricated and their electrochemical performance is measured. The NTC supercapacitor shows an ultrahigh rate capability (up to 2000 mV s^?1) and promising cycle life, retaining 91.5% of its initial performance after 50 000 galvanostatic charge–discharge cycles. An aqueous ZIC, constructed using the NTC, has a specific capacitance of 341.2 F g^?1 at a current density of 0.1 A g^?1 and an energy density of 189.6 Wh kg^?1 with a 2.0‐V voltage window, respectively. The outstanding performance is attributed to the NTC high N‐doping content, a continuous “polyhedral 3D hollow” architecture and the highly porous microtubular arms exhibiting very high surface area.     

Switchable Supercapacitors with Transistor‐Like Gating Characteristics (G‐Cap)

A novel three‐electrode electrolyte supercapacitor (electric double‐layer capacitor [EDLC]) architecture in which a symmetrical interdigital “working” two‐electrode micro‐supercapacitor array (W‐Cap) is paired with a third “gate” electrode that reversibly depletes/injects electrolyte ions into the system controlling the “working” capacity effectively is described. All three electrodes are based on precursor‐derived nanoporous carbons with well‐defined specific surface area (735 m² g^?1). The interdigitated architecture of the W‐Cap is precisely manufactured using 3D printing. The W‐Cap operating with a proton conducting PVA/H₂SO₄‐hydrogel electrolyte and high capacitance (6.9 mF cm^?2) can be repeatedly switched “on” and “off”. By applying a low DC bias potential (?0.5 V) at the gate electrode, the AC electroadsorption in the coupled interdigital nanoporous carbon electrodes of the W‐Cap is effectively suppressed leading to a stark capacity drop by two orders of magnitude from an “on” to an “off” state. The switchable micro‐supercapacitor is the first of its kind. This general concept is suitable for implementing a broad range of nanoporous materials and advanced electrolytes expanding its functions and applications in future. The integration of intelligent functions into EDLC devices has extensive implications for diverse areas such as capacitive energy management, microelectronics, iontronics, and neuromodulation.     

Role of Polymeric Metal Nucleation Inducers in Fabricating Large‐Area,Flexible, and Transparent Electrodes for Printable Electronics

The advent of special types of transparent electrodes, known as “ultrathin metal electrodes,” opens a new avenue for flexible and printable electronics based on their excellent optical transparency in the visible range while maintaining their intrinsic high electrical conductivity and mechanical flexibility. In this new electrode architecture, introducing metal nucleation inducers (MNIs) on flexible plastic substrates is a key concept to form high‐quality ultrathin metal films (thickness ≈ 10 nm) with smooth and continuous morphology. Herein, this paper explores the role of “polymeric” MNIs in fabricating ultrathin metal films by employing various polymers with different surface energies and functional groups. Moreover, a scalable approach is demonstrated using the ionic self‐assembly on typical plastic substrates, yielding large‐area electrodes (21 × 29.7 cm²) with high optical transmittance (>95%), low sheet resistance (<10 Ω sq^?1), and extreme mechanical flexibility. The results demonstrate that this new class of flexible and transparent electrodes enables the fabrication of efficient polymer light‐emitting diodes.     

Multi‐Stimuli‐Responsive Microcapsules for Adjustable Controlled‐Release

Novel multi‐stimuli‐responsive microcapsules with adjustable controlled‐release characteristics are prepared by a microfluidic technique. The proposed microcapsules are composed of crosslinked chitosan acting as pH‐responsive capsule membrane, embedded magnetic nanoparticles to realize “site‐specific targeting”, and embedded temperature‐responsive sub‐microspheres serving as “micro‐valves”. By applying an external magnetic field, the prepared smart microcapsules can achieve targeting aggregation at specific sites. Due to acid‐induced swelling of the capsule membranes, the microcapsules exhibit higher release rate at specific acidic sites compared to that at normal sites with physiological pH. More importantly, through controlling the hydrodynamic size of sub‐microsphere “micro‐valves” by regulating the environment temperature, the release rate of drug molecules from the microcapsules can be flexibly adjusted. This kind of multi‐stimuli‐responsive microcapsules with site‐specific targeting and adjustable controlled‐release characteristics provides a new mode for designing “intelligent” controlled‐release systems and is expected to realize more rational drug administration.     

High‐Fidelity Trapping of Spatial–Temporal Mitochondria with Rational Design of Aggregation‐Induced Emission Probes

High‐fidelity trapping of mitochondrial dynamic activity is critical to value cellular functions and forecast disease but lack of spatial–temporal probes. Given that commercial mitochondria probes suffering from low photostability, aggregation‐caused quenching effect, and limited signal‐to‐noise ratio from fluorescence “always on” in the process of targeting mitochondria, here, the rational design strategy of a novel aggregation‐induced emission (AIE) molecular motif and unique insight into the high‐fidelity targeting of mitochondria is reported, thereby illustrating the relationship between tailoring molecular aggregation state and mitochondrial targeting ability. This study focuses on how to exactly modulate the hydrophilicity and the aggregated state for realizing “off‐on” fluorescence, as well as matching the charge density to go across the cell membrane for mitochondrial targeting. Probe tricyano‐methylene‐pyridine (TCM‐1) exhibits an unprecedented high‐fidelity feedback on spatial–temporal mitochondrial information with several advantages such as “off‐on” near‐infrared characteristic, high targeting capacity, favorable biocompatibility, as well as excellent photostability. TCM‐1 also produces reactive oxygen species in situ for image‐guided photodynamic anticancer therapy. Through unraveling the relationship between tuning molecular aggregation behavior and organelle‐specific targeting ability, for the first time, a unique guide is provided in designing AIE‐active probes to explore the hydrophilicity and membrane potential for targeting subcellular organelles.     

Dendrimer‐Encapsulated Ruthenium Oxide Nanoparticles as Catalysts in Lithium‐Oxygen Batteries

Dendrimer‐encapsulated ruthenium oxide nanoparticles (DEN‐RuO₂) have been used as catalysts in lithium‐oxygen (Li‐O₂) batteries for the first time. The results obtained from ultraviolet‐visible spectroscopy, electron microscopy and X‐ray photoelectron spectroscopy show that the nanoparticles synthesized by the dendrimer template method are ruthenium oxide, not metallic ruthenium as reported by other groups. The DEN‐RuO₂ significantly improves the cycling stability of Li‐O₂ batteries with carbon electrodes and decreases the charging potential even at ten times less catalyst loading than those reported previously. The monodispersity, porosity, and large number of surface functionalities of the dendrimer template prevent the aggregation of the RuO₂ nanoparticles, making their entire surface area available for catalysis. The potential of using DEN‐RuO₂ as a standalone cathode material for Li‐O₂ batteries is also explored.     

Autonomously Controlled Homogenous Growth of Wafer‐Sized High‐Quality Graphene via a Smart Janus Substrate

The work reports a new method for large‐area growth of graphene films, which have been predicted to have novel and broad applications in the future. While chemical vapor deposition (CVD) is currently the preferred method, it suffers from a rather narrow processing window, and there is also much to be desired in the electrical properties of the CVD films. A new method for large‐area growth of graphene films is reported to overcome the narrow processing window of the CVD method. A composite substrate made of a C‐dissolving top (Ni) layer and a C‐rejecting bottom (Cu) layer is designed, which evolves into a C‐rejecting mixture, to autonomously regulate the C content at an elevated yet stable level at and near the surface over an extended duration. This “smart” substrate promotes graphene formation over a wide temperature‐gas composition window, leading to reliable growth of wafer‐sized graphene films of defined layer‐thickness and superior electrical–optical properties. This “smart”‐substrate strategy can also be implemented on Si and SiO₂ supports, paving the way toward the direct fabrication of large area, graphene‐enabled electronic and photonic devices.     

Microscopic and Nanoscopic Three‐Phase‐Boundaries of Platinum Thin‐Film Electrodes on YSZ Electrolyte

Agglomerated Pt thin films have been proposed as electrodes for electrochemical devices like micro‐solid oxide fuel cells (μ‐SOFCs) operating at low temperatures. However, comprehensive studies elucidating the interplay between agglomeration state and electrochemical properties are lacking. In this contribution the electrochemical performance of agglomerated and “dense” Pt thin film electrodes on yttria‐stabilized‐zirconia (YSZ) is correlated with their microstructural characteristics. Besides the microscopically measurable triple‐phase‐boundary (tpb) where Pt, YSZ and air are in contact, a considerable contribution of “nanoscopic” tpbs to the electrode conductivity resulting from oxygen permeable grain boundaries is identified. It is demonstrated that “dense” Pt thin films are excellent electrodes provided their grain size and thickness are in the nanometer range. The results disprove the prevailing idea that the performance of Pt thin film electrodes results from microscopic and geometrically measurable tpbs only.     

Capillary Network‐Like Organization of Endothelial Cells in PEGDA Scaffolds Encoded with Angiogenic Signals via Triple Helical Hybridization

Survival of tissue engineered constructs after implantation depends on proper vascularization. The differentiation of endothelial cells into mature microvasculature requires dynamic interactions between cells, scaffold, and growth factors, which are difficult to recapitulate in artificial systems. Previously, photocrosslinked poly(ethylene glycol) diacrylate (PEGDA) hydrogels displaying collagen mimetic peptides (CMPs), dubbed PEGDA‐CMP, that can be further conjugated with bioactive molecules via CMP‐CMP triple helix hybridization were reported. Here, it is shown that a bifunctional peptide featuring pro‐angiogenic domain mimicking vascular endothelial growth factor (VEGF) and a collagen mimetic domain that can fold into a triple helix conformation can hybridize with CMP side chains of the PEGDA‐CMP hydrogel, which results in presentation of insoluble VEGF‐like signals to endothelial cells. Presentation of VEGF‐like signals on the surface of micropatterned scaffolds in this way transforms cells from a quiescent state to elongated and aligned phenotype suggesting that this system could be used to engineer organized microvasculature. It is also shown that the pro‐angiogenic peptide, when applied topically in combination with modified dextran/PEGDA hydrogels, can enhance neovascularization of burn wounds in mice demonstrating the potential clinical use of CMP‐mediated matrix‐bound bioactive molecules for dermal injuries.     

Luminescent Graphene Oxide with a Peptide‐Quencher Complex for Optical Detection of Cell‐Secreted Proteases by a Turn‐On Response

Graphene oxide (GO) is an emerging luminescent nanomaterial with photostable and unique photoluminescence (PL) in the visible and near‐infrared region. Herein, a GO PL‐based optical biosensor consisting of a luminescent GO donor covalently linked with a peptide‐quencher complex is reported for the simple, rapid, and sensitive detection of proteases. To this end, the quenching efficiency of various candidate quenchers of GO fluorescence, such as metalloprotoporphyrins and QXL₅₇₀, are examined and their quenching mechanisms investigated. A fluorescence resonance energy transfer‐based quencher, QXL₅₇₀, is found to be much more effective for quenching the intrinsic fluorescence of GO than other charge transfer‐based quenchers. The designed GO–peptide–QXL system is then able to sensitively detect specific proteases—chymotrypsin and matrix metalloproteinase‐2—via a “turn‐on” response of quenched GO fluorescence after proteolytic cleavage of the quencher. Finally, the GO–peptide–QXL hybrid successfully detects MMP‐2 secreted from living cells—human hepatocytes HepG2—with high sensitivity.     

Tunable Structural Color Surfaces with Visually Self‐Reporting Wettability

Functional materials with wettability of specific surfaces are important for many areas. Here, a new lubricant‐infused elastic inverse opal is presented with tunable and visually “self‐reporting” surface wettability. The elastic inverse opal films are used to lock in the infused lubricating fluid and construct slippery surfaces to repel droplets of various liquids. The films are stretchable, and the lubricating fluid can penetrate the pores under stretching, leaving the surface layer free of lubrication; the resultant undulating morphology of the inverse opal scaffold topography can reversibly pin droplets on the fluidic film rather than the solid substrate. This mechanical stimulation process provides an effective means of dynamically tuning the surface wettability and the optical transparency of the inverse opal films. In particular, as the adjustments are accompanied by simultaneous deformation of the periodic macroporous structure, the inverse opal films can self‐report on their surface status through visible structural color changes. These features make such slippery structural color materials highly versatile for use in diverse applications.     

Novel Signal‐Amplifying Fluorescent Nanofibers for Naked‐Eye‐Based Ultrasensitive Detection of Buried Explosives and Explosive Vapors

A novel electrospun fluorescent nanofiberous membrane with a function like “molecular wires” was developed via electrospinning for the detection of ultra‐trace nitro explosive vapors and buried explosives by naked eye under UV excitation. The high binding affinity between the electron‐deficient nitro explosives and the sensing film results in a rapid, dramatic quenching in its fluorescence emission. A wide spectrum of nitro explosives, in particular, TNT, Tetryl, RDX, PETN and HMX could be “visually” detected at their sub‐equilibrium vapors (less than 10 ppb, 74 ppt, 5 ppt, 7 ppt and 0.1 ppt, respectively) released from 1 ng explosives residues. Such outstanding sensing performance could be attributed to the proposed “sandwich‐like” conformation between pyrene and phenyl pendants of PS which may allow efficient long‐range energy migration similar to “molecular wire”, thus achieving amplified fluorescence quenching. Its application for the detection of buried explosives in soil by naked eye was also demonstrated, indicating its potential application for landmine mapping. To the best of our knowledge, this is the first report about the detection of buried explosives without the use of any advanced analytical instrumentation.     

Growth and Properties of Hybrid Organic‐Inorganic Metalcone Films Using Molecular Layer Deposition Techniques

Molecular layer deposition (MLD) is a useful technique for fabricating hybrid organic‐inorganic thin films. MLD allows for the growth of ultrathin and conformal films using sequential, self‐limiting reactions. This article focuses on the MLD of hybrid organic‐inorganic films grown using metal precursors and various organic alcohols that yield metal alkoxide films. This family of metal alkoxides can be described as “metalcones”. Many metalcones are possible, such as the “alucones” and “zincones” based on the reaction of trimethylaluminum and diethylzinc, respectively, with various organic diols such as ethylene glycol. Alloys of the various metalcones with their parent metal oxide atomic layer deposition (ALD) films can also be fabricated that have an organic‐inorganic composition that can be adjusted by controlling the relative number of ALD and MLD cycles. These metalcone alloys have tunable chemical, optical, mechanical, and electrical properties that may be useful for designing various functional films. The metalcone hybrid organic‐inorganic materials offer a new tool set for engineering thin film properties.     

Conjugated Polymers of Intrinsic Microporosity (C‐PIMs)

Conjugated microporous polymers (CMPs) have shown great potential for energy and environmental issues, however, poor solubility and processability of most of these materials limit their applications. Herein, a range of linear conjugated polymers of intrinsic microporosity (C‐PIMs) is reported, combining for the first time the properties of conjugated microporous polymers, such as tunable electronic properties and compositional variation, with those of linear polymers of intrinsic microporosity (PIMs) allowing for solution processability and film formation. These soluble materials have a number of potential applications, for example as components in devices where large, porous interfaces are combined with extended electronic conjugation.     

Sub‐5 nm Dendrimer Directed Self‐Assembly with Large‐Area Uniform Alignment by Graphoepitaxy

Directed self‐assembly (DSA) using soft materials is an important method for producing periodic nanostructures because it is a simple, cost‐effective process for fabricating high‐resolution patterns. Most of the previously reported DSA methods exploit the self‐assembly of block copolymers, which generates a wide range of nanostructures. In this study, cylinders obtained from supramolecular dendrimer films with a high resolution (<5 nm) exhibit planar ordering over a macroscopic area via guiding topographical templates with a high aspect ratio (>10) and high spatial resolution (≈20 nm) of guiding line patterns. Theoretical and experimental studies reveal that this property is related to geometrical anchoring on the meniscus region and physical surface anchoring on the sidewall. Furthermore, this DSA of dendrimer cylinders is demonstrated by the non‐regular geometry of the patterned template. The macroscopic planar alignment of the dendrimer nanostructure reveals an extremely small feature size (≈4.7 nm) on the wafer scale (>16 cm²). This study is expected to open avenues for the production of a large family of supramolecular dendrimers with different phases and feature dimensions oriented by the DSA approach.     

Highly Efficient Electrocatalysts for Oxygen Reduction Reaction Based on 1D Ternary Doped Porous Carbons Derived from Carbon Nanotube Directed Conjugated Microporous Polymers

One‐dimensional (1D) porous materials have shown great potential for gas storage and separation, sensing, energy storage, and conversion. However, the controlled approach for preparation of 1D porous materials, especially porous organic materials, still remains a great challenge due to the poor dispersibility and solution processability of the porous materials. Here, carbon nanotube (CNT) templated 1D conjugated microporous polymers (CMPs) are prepared using a layer‐by‐layer method. As‐prepared CMPs possess high specific surface areas of up to 623 m² g^?1 and exhibit strong electronic interactions between p‐type CMPs and n‐type CNTs. The CMPs are used as precursors to produce heteroatom‐doped 1D porous carbons through direct pyrolysis. As‐produced ternary heteroatom‐doped (B/N/S) 1D porous carbons possess high specific surface areas of up to 750 m² g^?1, hierarchical porous structures, and excellent electrochemical‐catalytic performance for oxygen reduction reaction. Both of the diffusion‐limited current density (4.4 mA cm^?2) and electron transfer number (n = 3.8) for three‐layered 1D porous carbons are superior to those for random 1D porous carbon. These results demonstrate that layered and core–shell type 1D CMPs and related heteroatom‐doped 1D porous carbons can be rationally designed and controlled prepared for high performance energy‐related applications.     

Long Range Self‐Assembly of Polythiophene Breath Figures: Optical and Morphological Characterization

Large‐area, device relevant sized microporous thin films are formed with commercially available polythiophenes by the breath figure technique, a water‐assisted micropatterning method, with such semitransparent thin films exhibiting periodicity and uniformity dictated by the length of the polymer side chain. Compared to drop‐casted thin films, the microporous thin films exhibit increased crystallinity due to stronger packing of the polymer inside the honeycomb frame.