Humidity‐Triggered Self‐Healing of Microporous Polyelectrolyte Multilayer Coatings for Hydrophobic Drug Delivery

Layer‐by‐layer (LbL) self‐assemblies have inherent potential as dynamic coatings because of the sensitivity of their building blocks to external stimuli. Here, humidity serves as a feasible trigger to activate the self‐healing of a microporous polyethylenimine/poly(acrylic acid) multilayer film. Microporous structures within the polyelectrolyte multilayer (PEM) film are created by acid treatment, followed by freeze‐drying to remove water. The self‐healing of these micropores can be triggered at 100% relative humidity, under which condition the mobility of the polyelectrolytes is activated. Based on this, a facile and versatile method is suggested for directly integrating hydrophobic drugs into PEM films for surface‐mediated drug delivery. The high porosity of microporous film enables the highest loading (≈303.5 μg cm^?2 for a 15‐bilayered film) of triclosan to be a one‐shot process via wicking action and subsequent solvent removal, thus dramatically streamlining the processes and reducing complexities compared to the existing LbL strategies. The self‐healing of a drug‐loaded microporous PEM film significantly reduces the diffusion coefficient of triclosan, which is favorable for the long‐term sustained release of the drug. The dynamic properties of this polymeric coating provide great potential for its use as a delivery platform for hydrophobic drugs in a wide variety of biomedical applications.     

Soft Nanostructured Films for Actuated Surface‐Based siRNA Delivery

Substrate‐mediated gene delivery is an emerging technology that enables spatial control of gene expression and localized delivery. This is of particular interest for siRNA where surface‐based release can greatly impact the fields of stem‐cell reprograming, wound healing, and medical device coatings in general. However, reports on the use of siRNA for substrate‐mediated delivery are scarce and have suffered from low efficiency. Here, an alternative strategy is reported by designing self‐assembled substrates that experience stimuli‐responsive topological transformations. Specifically, a methodology is established to promote the molecular organization of lipid films having 3D‐bicontinuous cubic, 2D‐inverted hexagonal, or 1D‐lamellar nanostructures encapsulating siRNA. In response to a compositional, temperature, or humidity stimulus, the nanostructures evolve from 1D‐lamellar or 2D‐hexagonal to 3D‐cubic resulting in efficient siRNA release to human cell cultures. Grazing incidence X‐ray diffraction reveals that film nanostructures are highly ordered and preferentially aligned. The results indicate that film structure substantially affects siRNA delivery, with the supported 3D‐bicontinuous cubic phase yielding the most effective reduction of gene expression. Subsequent studies suggest this enhanced performance arises due to the ability of this phase to cross cell membranes, particularly those of endocytic compartments. This work underpins that nanostructure tuning is decisive to the performance of therapeutic films.     

Self‐Powered Electronics by Integration of Flexible Solid‐State Graphene‐Based Supercapacitors with High Performance Perovskite Hybrid Solar Cells

To develop high‐capacitance flexible solid‐state supercapacitors and explore its application in self‐powered electronics is one of ongoing research topics. In this study, self‐stacked solvated graphene (SSG) films are reported that have been prepared by a facile vacuum filtration method as the free‐standing electrode for flexible solid‐state supercapacitors. The highly hydrated SSG films have low mass loading, high flexibility, and high electrical conductivity. The flexible solid‐state supercapacitors based on SSG films exhibit excellent capacitive characteristics with a high gravimetric specific capacitance of 245 F g^?1 and good cycling stability of 10 000 cycles. Furthermore, the flexible solid‐state supercapacitors are integrated with high performance perovskite hybrid solar cells (pero‐HSCs) to build self‐powered electronics. It is found that the solid‐state supercapacitors can be charged by pero‐HSCs and discharged from 0.75 V. These results demonstrate that the self‐powered electronics by integration of the flexible solid‐state supercapacitors with pero‐HSCs have great potential applications in storage of solar energy and in flexible electronics, such as portable and wearable personal devices.     

Highly Stable Graphene‐Based Multilayer Films Immobilized via Covalent Bonds and Their Applications in Organic Field‐Effect Transistors

Highly stable graphene oxide (GO)‐based multilayered ultrathin films can be covalently immobilized on solid supports through a covalent‐based method. It is demonstrated that when (3‐aminopropyl) trimethoxysilane (APTMS), which works as a covalent cross‐linking agent, and GO nanosheets are assembled in an layer‐by‐layer (LBL) manner, GO nanosheets can be covalently grafted on the solid substrate successfully to produce uniform multilayered (APTMS/GO)N films over large‐area surfaces. Compared with conventional noncovalent LBL films constructed by electrostatic interactions, those assembled using this covalent‐based method display much higher stability and reproducibility. Upon thermal annealing‐induced reduction of the covalent (APTMS/GO)N films, the obtained reduced GO (RGO) films, (APTMS/RGO)N, preserve their basic structural characteristics. It is also shown that the as‐prepared covalent (APTMS/RGO)N multilayer films can be used as highly stable source/drain electrodes in organic field‐effect transistors (OFETs). When the number of bilayers of the (APTMS/RGO)N film exceeds 2 (ca. 2.7 nm), the OFETs based on (APTMS/RGO)N electrodes display much better electrical performance than devices based on 40 nm Au electrodes. The covalent protocol proposed may open up new opportunities for the construction of graphene‐based ultrathin films with excellent stability and reproducibility, which are desired for practical applications that require withstanding of multistep post‐production processes.     

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.     

Light‐Driven and Light‐Guided Microswimmers

Light‐driven swimming particles hold great potential in wide applications ranging from next‐generation drug delivery to versatile microrobotic devices. It is desired that the self‐propelled microparticles should swim not only autonomously but also directionally to achieve their goals in their potential applications. This paper presents the first example of fully organic colloidal particles of a spiropyran‐terminated hyperbranched polymer that can be driven and meanwhile steered by a UV light source, swimming straight towards the UV source. The mean‐square velocities of the photochromic suspension particles are about 20 μm s^?1, and increase to about 54 μm s^?1 with the addition of NaCl of 0.5%. The phototactic propulsion is supposed to be originated from the UV irradiation‐induced interfacial tension gradient on the surface of the colloidal particles. This finding allows for the design of new microengines for next‐generation drug delivery systems, microrobotic devices, and self‐adaptive photocatalysts, etc.     

Peptide‐Based Nanostructured Materials with Intrinsic Proapoptotic Activities in CXCR4+ Solid Tumors

Protein materials are gaining interest in nanomedicine because of the unique combination of regulatable function and structure. A main application of protein nanoparticles is as vehicles for cell‐targeted drug delivery in the form of nanoconjugates, in which a conventional or innovative drug is associated to a carrier protein. Here, a new nanomedical approach based on self‐assembling protein nanoparticles is developed in which a chemically homogeneous protein material acts, simultaneously, as vehicle and drug. For that, three proapoptotic peptidic factors are engineered to self‐assemble as protein‐only, fully stable nanoparticles that escape renal clearance, for the multivalent display of a CXCR4 ligand and the intracellular delivery into CXCR4⁺ colorectal cancer models. These materials, produced and purified in a single step from bacterial cells, show an excellent biodistribution upon systemic administration and local antitumoral effects. The design and generation of intrinsically therapeutic protein‐based materials offer unexpected opportunities in targeted drug delivery based on fully biocompatible, tailor‐made constructs.     

Nucleation‐Governed Reversible Self‐Assembly of an Organic Semiconductor at Surfaces: Long‐Range Mass Transport Forming Giant Functional Fibers

The use of solvent‐vapor annealing (SVA) to form millimeter‐long crystalline fibers, having a sub‐micrometer cross section, on various solid substrates is described. Thin films of a perylene‐bis(dicarboximide) (PDI) derivative, with branched alkyl chains, prepared from solution exhibit hundreds of nanometer‐sized PDI needles. Upon exposure to the vapors of a chosen solvent, tetrahydrofuran (THF), the needles re‐organize into long fibers that have a remarkably high aspect ratio, exceeding 10³. Time‐ and space‐resolved mapping with optical microscopy allows the self‐assembly mechanism to be unravelled; the mechanism is found to be a nucleation‐governed growth, which complies with an Avrami‐type of mechanism. SVA is found to lead to self‐assembly featuring i) long‐range order (up to the millimeter scale), ii) reversible characteristics, as demonstrated through a series of assembly and disassembly steps, obtained by cycling between THF and CHCl₃ as solvents, iii) remarkably high mass transport because the PDI molecular motion is found to occur at least over hundreds of micrometers. Such a detailed understanding of the growth process is fundamental to control the formation of self‐assembled architectures with pre‐programmed structures and physical properties. The versatility of the SVA approach is proved by its successful application using different substrates and solvents. Kelvin probe force microscopy reveals that the highly regular and thermodynamically stable fibers of PDI obtained by SVA exhibit a greater electron‐accepting character than the smaller needles of the drop‐cast films. The giant fibers can be grown in situ in the gap between microscopic electrodes supported on SiO_x, paving the way towards the application of SVA in micro‐ and nanoelectronics.     

Deep‐Red/Near‐Infrared Electroluminescence from Single‐Component Charge‐Transfer Complex via Thermally Activated Delayed Fluorescence Channel

Formation of a single‐component charge‐transfer complex (SCCTC) is unveiled in solid state of an intermolecular charge‐transfer molecule 2‐(4‐(1‐phenyl‐1H‐phenanthro[9,10‐d]imidazol‐2‐yl)phenyl)anthracene‐9,10‐dione (PIPAQ). Intermolecular donor–acceptor interactions between two PIPAQ molecules is the primary driving force for self‐association and contributes to intermolecular charge transfer. The SCCTC character is fully verified by crystallographic, photophysical, electron spin resonance, and vibrational characterizations. The PIPAQ‐based SCCTC is first applied in light‐emitting devices as an emissive layer to realize efficient deep‐red/near‐infrared electroluminescence. This work provides new insights into SCCTC and represents an important step toward their applications in optoelectronic devices.     

Free‐Standing Carbon Nanofibrous Films Prepared by a Fast Microwave‐Assisted Synthesis Process

Carbon nanofibrous (CNF) films are of great interest for various applications, e.g., as substrates for electrodes, sensors, or catalysts. Here, a fast microwave‐assisted synthesis is reported to fabricate square‐centimeter large free‐standing carbon nanofibrous films of approximately 10 μm thickness utilizing nickel‐based catalysts and ethanol as carbon source. The obtained CNF coatings exhibit a good stability and partial self‐delamination from the substrate is observed, which enables their easy detachment from the substrate without the need for further treatment. Scanning electron microscopy is applied to investigate the morphology of the films and to develop a growth model.     

Self‐Assembly of a Donor‐Acceptor Dyad Across Multiple Length Scales: Functional Architectures for Organic Electronics

Molecular dyads based on polycyclic electron donor (D) and electron acceptor (A) units represent suitable building blocks for forming highly ordered, solution‐processable, nanosegregated D‐A domains for potential use in (opto)electronic applications. A new dyad, based on alkyl substituted hexa‐peri‐hexabenzocoronene (HBC) and perylene monoimide (PMI) separated by an ethinylene linker, is shown to have a high tendency to self‐assemble into ordered supramolecular arrangements at multiple length scales: macroscopic extruded filaments display long‐range crystalline order, nanofiber networks are produced by simple spin‐coating, and monolayers with a lamellar packing are formed by physisorption at the solution‐HOPG interface. Moreover, highly uniform mesoscopic ribbons bearing atomically flat facets and steps with single‐molecule heights self‐assemble upon solvent‐vapor annealing. Electrical measurements of HBC‐PMI films and mesoscopic ribbons in a transistor configuration exhibit ambipolar transport with well balanced p‐ and n‐type mobilities. Owing to the increased level of order at the supramolecular level, devices based on ribbons show mobility increases of more than one order of magnitude.     

Highly Scalable,Closed‐Loop Synthesis of Drug‐Loaded,Layer‐by‐Layer Nanoparticles

Layer‐by‐layer (LbL) self‐assembly is a versatile technique from which multi­component and stimuli‐responsive nanoscale drug‐carriers can be constructed. Despite the benefits of LbL assembly, the conventional synthetic approach for fabricating LbL nanoparticles requires numerous purification steps that limit scale, yield, efficiency, and potential for clinical translation. In this report, a generalizable method for increasing throughput with LbL assembly is described by using highly scalable, closed‐loop diafiltration to manage intermediate purification steps. This method facilitates highly controlled fabrication of diverse nanoscale LbL formulations smaller than 150 nm composed from solid‐polymer, mesoporous silica, and liposomal vesicles. The technique allows for the deposition of a broad range of polyelectrolytes that included native polysaccharides, linear polypeptides, and synthetic polymers. The cytotoxicity, shelf life, and long‐term storage of LbL nanoparticles produced using this approach are explored. It is found that LbL coated systems can be reliably and rapidly produced: specifically, LbL‐modified liposomes could be lyophilized, stored at room temperature, and reconstituted without compromising drug encapsulation or particle stability, thereby facilitating large scale applications. Overall, this report describes an accessible approach that significantly improves the throughput of nanoscale LbL drug‐carriers that show low toxicity and are amenable to clinically relevant storage conditions.     

Self‐Assembled Room Temperature Multiferroic BiFeO3‐LiFe5O8 Nanocomposites

Multiferroic materials have driven significant research interest due to their promising technological potential. Developing new room‐temperature multiferroics and understanding their fundamental properties are important to reveal unanticipated physical phenomena and potential applications. Here, a new room temperature multiferroic nanocomposite comprised of an ordered ferrimagnetic spinel α‐LiFe₅O₈ (LFO) and a ferroelectric perovskite BiFeO₃ (BFO) is presented. It is observed that lithium (Li)‐doping in BFO favors the formation of LFO spinel as a secondary phase during the synthesis of Li_xBi_1?xFeO₃ ceramics. Multimodal functional and chemical imaging methods are used to map the relationship between doping‐induced phase separation and local ferroic properties in both the BFO‐LFO composite ceramics and self‐assembled nanocomposite thin films. The energetics of phase separation in Li doped BFO and the formation of BFO‐LFO composites are supported by first principles calculations. These findings shed light on Li's role in the formation of a functionally important room temperature multiferroic and open a new approach in the synthesis of light element doped nanocomposites for future energy, sensing, and memory applications.     

General Method for Large‐Area Films of Carbon Nanomaterials and Application of a Self‐Assembled Carbon Nanotube Film as a High‐Performance Electrode Material for an All‐Solid‐State Supercapacitor

Rational assembly of carbon nanostructures into large‐area films is a key step to realize their applications in ubiquitous electronics and energy devices. Here, a self‐assembly methodology is devised to organize diverse carbon nanostructures (nanotubes, dots, microspheres, etc.) into homogeneous films with potentially infinite lateral dimensions. On the basis of studies of the redox reactions in the systems and the structures of films, the spontaneous deposition of carbon nanostructures onto the surface of the copper substrate is found to be driven by the electrical double layer between copper and solution. As a notable example, the as‐assembled multiwalled carbon nanotube (MWCNT) films display exceptional properties. They are a promising material for flexible electronics with superior electrical and mechanical compliance characteristics. Finally, two kinds of all‐solid‐state supercapacitors based on the self‐assembled MWCNT films are fabricated. The supercapacitor using carbon cloth as the current collector delivers an energy density of 3.5 Wh kg^?1 and a power density of 28.1 kW kg^?1, which are comparable with the state‐of‐the‐art supercapacitors fabricated by the costly single‐walled carbon nanotubes and arrays. The supercapacitor free of foreign current collector is ultrathin and shows impressive volumetric energy density (0.58 mWh cm^?3) and power density (0.39 W cm^?3) too.     

An Improved Optical Method for Determining the Order Parameter in Thin Oriented Molecular Films and Demonstration of a Highly Axial Dipole Moment for the Lowest Energy π–π* Optical Transition in Poly(9,9‐ dioctylfluorene‐co‐bithiophene)

Understanding the complex interplay between the 3D structural hierarchy within thin films of conjugated polymers and the properties of devices based thereon is starting to be recognized as an important challenge in the continued development of these materials for a range of applications. As a result, for example, accurate measurements of molecular orientation and elucidation of its influence on optical characteristics are of significant interest. Here we report an improved optical method to determine both the order parameter and the angle between the polymer backbone director and the optical transition dipole moment for the lowest energy π–π* absorption peak in uniaxially aligned thin films of conjugated polymers. The method uses a combination of polarized Raman spectroscopy and UV‐vis spectroscopy and is based on a general theoretical treatment to describe the expected Raman and optical absorption anisotropies of such films. It is applied to study the orientation within thermotropically aligned films of the electroluminescent fluorene‐based copolymer poly(9,9‐dioctylfluorene‐co‐bithiophene) (F8T2). A more highly axial transition dipole moment is found for the dominant long wavelength absorption peak of F8T2 compared to that of other fluorene‐based (co)polymers. The angle between the polymer backbone director and the transition dipole is estimated to be β ≤ 3°, a deduction that helps to explain the relatively large optical dichroism for aligned films of F8T2 and that offers the prospect of highly polarized electroluminescence from F8T2‐based light‐emitting diodes.     

Supramolecular Nanostructuring of Silver Surfaces via Self‐Assembly of [60]Fullerene and Porphyrin Modules

Recent achievements in our laboratory toward the “bottom‐up” fabrication of addressable multicomponent molecular entities obtained by self‐assembly of C₆₀ and porphyrins on Ag(100) and Ag(111) surfaces are described. Scanning tunneling microscopy (STM) studies on ad‐layers constituting monomeric and triply linked porphyrin modules showed that the molecules self‐organize into ordered supramolecular assemblies, the ordering of which is controlled by the porphyrin chemical structure, the metal substrate, and the surface coverage. Specifically, the successful preparation of unprecedented two‐dimensional porphyrin‐based assemblies featuring regular pores on Ag(111) surfaces has been achieved. Subsequent co‐deposition of C₆₀ molecules on top of the porphyrin monolayers results in selective self‐organization into ordered molecular hybrid bilayers, the organization of which is driven by both fullerene coverage and porphyrin structure. In all‐ordered fullerene–porphyrin assemblies, the C₆₀ guests organize, unusually, into long chains and/or two‐dimensional arrays. Furthermore, sublimation of C₆₀ on top of the porous porphyrin network reveals the selective long‐range inclusion of the fullerene guests within the hosting cavities. The observed mode of the C₆₀ self‐assembly originates from a delicate equilibrium between substrate–molecule and molecule–molecule interactions involving charge‐transfer processes and conformational reorganizations as a consequence of the structural adaptation of the fullerene–porphyrin bilayer.     

Stepwise Drug‐Release Behavior of Onion‐Like Vesicles Generated from Emulsification‐Induced Assembly of Semicrystalline Polymer Amphiphiles

Tailoring unique nanostructures of biocompatible and degradable polymers and the consequent elucidation of shape effects in drug delivery open tremendous opportunities not only to broaden their biomedical applications but also to identify new directions for the design of nanomedicine. Cellular organelles provide the basic structural and functional motif for the development of novel artificial nanoplatforms. Herein, aqueous onion‐like vesicles structurally mimicking multicompartmentalized cellular organelles by exhibiting exquisite control over the molecular assembly of poly(ethylene oxide)‐block‐poly(ε‐caprolactone) (PEO‐b‐PCL) semicrystalline amphiphiles are reported. Compared to in situ self‐assembly, emulsification‐induced assembly endows the resulting nanoaggregates of PEO‐b‐PCL with structural diversity such as helical ribbons and onion‐like vesicles through the molecular packing modification in the hydrophobic core with a reduction of inherent crystalline character of PCL. In particular, onion‐like vesicles composed of alternating walls and water channels are interpreted by nanometer‐scale 3D visualization via cryogenic‐electron tomo­graphy (cryo‐ET). Interestingly, the nature of the multi‐walled vesicles results in high drug‐loading capacity and stepwise drug release through hydrolytic cleavage of the PCL block. The crystalline arrangement of PCL at the molecular scale and the spatial organization of assembled structure at the nanoscale significantly affect the drug‐release behavior of PEO‐b‐PCL nanovehicles.     

Silicon‐Based Self‐Assemblies for High Volumetric Capacity Li‐Ion Batteries via Effective Stress Management

Silicon nanoparticles (Si NPs) have been considered as promising anode materials for next‐generation lithium‐ion batteries, but the practical issues such as mechanical structure instability and low volumetric energy density limit their development. At present, the functional energy‐storing architectures based on Si NPs building blocks have been proposed to solve the adverse effects of nanostructures, but designing ideal functional architectures with excellent electrochemical performance is still a significant challenge. This study shows that the effective stress evolution management is applied for self‐assembled functional architectures via cross‐scale simulation and the simulated stress evolution can be a guide to design a scalable self‐assembled hierarchical Si@TiO₂@C (SA‐SiTC) based on core–shell Si@TiO₂ nanoscale building blocks. It is found that the carbon filler and TiO₂ layer can effectively reduce the risk of cracking during (de)lithiation, ensuring the stability of the mechanical structure of SA‐SiTC. The SA‐SiTC electrode shows long cycling stability (842.6 mAh g^?1 after 1000 cycles at 2 A g^?1), high volumetric capacity (174 mAh cm^?3), high initial Coulombic efficiency (80.9%), and stable solid‐electrolyte interphase (SEI) layer. This work provides insight into the development of the structural stable Si‐based anodes with long cycle life and high volumetric energy density for practical energy applications.     

Open‐Shell Donor–Acceptor Conjugated Polymers with High Electrical Conductivity

Conductive polymers largely derive their electronic functionality from chemical doping, processes by which redox and charge‐transfer reactions form mobile carriers. While decades of research have demonstrated fundamentally new technologies that merge the unique functionality of these materials with the chemical versatility of macromolecules, doping and the resultant material properties are not ideal for many applications. Here, it is demonstrated that open‐shell conjugated polymers comprised of alternating cyclopentadithiophene and thiadiazoloquinoxaline units can achieve high electrical conductivities in their native “undoped” form. Spectroscopic, electrochemical, electron paramagnetic resonance, and magnetic susceptibility measurements demonstrate that this donor–acceptor architecture promotes very narrow bandgaps, strong electronic correlations, high‐spin ground states, and long‐range π‐delocalization. A comparative study of structural variants and processing methodologies demonstrates that the conductivity can be tuned up to 8.18 S cm^?1. This exceeds other neutral narrow bandgap conjugated polymers, many doped polymers, radical conductors, and is comparable to commercial grades of poly(styrene‐sulfonate)‐doped poly(3,4‐ethylenedioxythiophene). X‐ray and morphological studies trace the high conductivity to rigid backbone conformations emanating from strong π‐interactions and long‐range ordered structures formed through self‐organization that lead to a network of delocalized open‐shell sites in electronic communication. The results offer a new platform for the transport of charge in molecular systems.