A Hydrogen‐Bonded‐Supramolecular‐Polymer‐Based Nanoprobe for Ratiometric Oxygen Sensing in Living Cells

The first example of a ratiometric optical oxygen nanoprobe based on a hydrogen‐bonded supramolecular polymer has been reported. The supramolecular polymer based nanoprobe (SPNP) is prepared from the co‐assembly of a bis‐ureidopyrimidinone (bis‐UPy)‐containing phosphorescent indicator (Por(Pd)‐bisUPy), fluorescent reference dye (BF₂‐bisUPy), and skeleton unit (DPA‐bisUPy) through quadruple hydrogen bonds by a mini‐emulsion method. The water‐dispersible SPNP is highly sensitive to oxygen (Q = 95%), with full reversibility, excellent storage stability and photostability, and good cell‐penetrating ability, and exhibits low cytotoxicity toward living cells. The preparation of the SPNP is straightforward and its function is easily tuned by changing the monomeric structure. This work is expected to lead to the design of other SPNPs for other important analytes in biological systems.     

Non‐Equilibrium,Light‐Adaptive,Steady‐State Reconfiguration of Mechanical Patterns in Bioinspired Nanocomposites

Bioinspired nanocomposites have made great progress for the fabrication of mechanical high‐performance structural materials, but their properties have thus far been engineered with a focus on static behavior. This contrasts profoundly with the dynamic reconfiguration often observed in living tissues. Here, a first concept is introduced for steady‐state, light‐adaptive reconfiguration of mechanical patterns in bioinspired nanocomposites under dissipative out‐of‐equilibrium conditions. This is realized for green, waterborne cellulose nanofibril/polymer nanopapers by achieving a heterogeneous activation of a photothermal effect. To this end, predefined mechanical patterns are designed by top‐down lamination of bottom‐up engineered bioinspired nanocomposites containing thermoreversible hydrogen bonds, as well as spatially selectively incorporated single‐walled carbon nanotubes for photothermal response. Global irradiation leads to localized photothermal softening by cascading light to heat, and to the dynamization and breakage of the thermoreversible supramolecular bonds, leading to macroscopic reconfiguration and even inversion of mechanical stiff/soft patterns. The altered configuration is only stable in a dissipative steady state and relaxes to the ground state once light is removed. The strategy presents a new approach harnessing the capabilities from top‐down and bottom‐up structuring, and by interfacing it with non‐equilibrium adaptivity concepts, it opens avenues for hierarchical bioinspired materials with anisotropic response in global fields.     

Cephalopod‐Inspired High Dynamic Range Mechano‐Imaging in Polymeric Materials

Cephalopods, such as squid, cuttlefish, and octopuses, use an array of responsive absorptive and photonic dermal structures to achieve rapid and reversible color changes for spectacular camouflage and signaling displays. Challenges remain in designing synthetic soft materials with similar multiple and dynamic responsivity for the development of optical sensors for the sensitive detection of mechanical stresses and strains. Here, a high dynamic range mechano‐imaging (HDR‐MI) polymeric material integrating physical and chemical mechanochromism is designed providing a continuous optical read‐out of strain upon mechanical deformation. By combining a colloidal photonic array with a mechanically responsive dye, the material architecture significantly improves the mechanochromic sensitivity, which is moreover readily tuned, and expands the range of detectable strains and stresses at both microscopic and nanoscopic length scales. This multi‐functional material is highlighted by creating detailed HDR mechanographs of membrane deformation and around defects using a low‐cost hyperspectral camera, which is found to be in excellent agreement with the results of finite element simulations. This multi‐scale approach to mechano‐sensing and ‐imaging provides a platform to develop mechanochromic composites with high sensitivity and high dynamic mechanical range.     

Influence of Hydrogen Bonds on the Supramolecular Order of Hexa‐peri‐hexabenzocoronenes

Three different hexa‐peri‐hexabenzocoronene (HBC) derivatives with carboxylic acid functions have been synthesized to study the effect of hydrogen bonding on the already pronounced columnar π‐stacking. This functionalization improves the degree of order in the bulk and influences the surface patterning at solid‐liquid interfaces as well as the thermal properties of these materials. The length of the tether between the aromatic core and the hydrogen‐bond‐forming carboxy group appears as a key factor influencing the supramolecular self‐assembly, since only the HBCs with shorter spacers showed a strong synergetic effect of the columnar π‐stacking with the hydrogen‐bonding motifs. Clear signatures for this are unusually high mesophase transition temperatures and non‐tilted columnar stacking in the pseudocrystalline phase. As model systems, HBC dyads have been synthesized with the two HBC disks linked through a covalent spacer fitting the intercolumnar distance of the short‐tethered, hydrogen‐bridged dimer. This comparison emphasized the impact of the hydrogen bonds on the supramolecular properties of the materials. A broad range of analytical methods have been used, including differential scanning calorimetry, wide‐angle X‐ray diffractometry, solid‐state NMR spectroscopy, and scanning tunneling microscopy.     

Light‐Fueled,Spatiotemporal Modulation of Mechanical Properties and Rapid Self‐Healing of Graphene‐Doped Supramolecular Elastomers

Gaining spatially resolved control over the mechanical properties of materials in a remote, programmable, and fast‐responding way is a great challenge toward the design of adaptive structural and functional materials. Reversible, temperature‐sensitive systems, such as polymers equipped with supramolecular units, are a good model system to gain detailed information and target large‐scale property changes by exploiting reversible crosslinking scenarios. Here, it is demonstrated that coassembled elastomers based on polyglycidols functionalized with complementary cyanuric acid and diaminotriazine hydrogen bonding couples can be remotely modulated in their mechanical properties by spatially confined laser irradiation after hybridization with small amounts of thermally reduced graphene oxide (TRGO). The TRGO provides an excellent photothermal effect, leads to light‐adaptive steady‐state temperatures, and allows local breakage/de‐crosslinking of the hydrogen bonds. This enables fast self‐healing and spatiotemporal modulation of mechanical properties, as demonstrated by digital image correlation. This study opens pathways toward light‐fueled and light‐adaptive graphene‐based nanocomposites employing molecularly controlled thermal switches.     

A Colorimetric Hydrocarbon Sensor Employing a Swelling‐Induced Mechanochromic Polydiacetylene

Exceptional challenges have confronted the rational design of colorimetric sensors for saturated aliphatic hydrocarbons (SAHCs). The main reasons for this difficulty are the extremely nonpolar nature of these targets and their lack of functional groups that can interact with probes. By taking advantage of a mechanochromic conjugated polydiacetylene (PDA) and the hydrocarbon‐induced swelling properties of polydimethylsiloxane (PDMS), a sensor film that enables simple, colorimetric differentiation between a variety of C5 to C14 aliphatic hydrocarbons is fabricated. The unprecedented PDA–PDMS composite sensor undergoes a blue‐to‐red colorimetric transition on a timescale that is dependent on the chain length of the hydrocarbon target. In addition, the development of the red color is directly proportional to the swelling ratio of the film. This straightforward approach enables naked‐eye differentiation between n‐pentane and n‐heptane. The versatility of the sensor system is demonstrated by using it for the colorimetric determination of kerosene in adulterated diesel oil. Finally, the observation that a PDA microcrystal in the film undergoes significant expansion and tearing in concert with a blue‐to‐red colorimetric transition during the swelling process provides direct evidence for the mechanism for the mechanochromic behavior of the PDA.     

Analysis of Metallo‐Supramolecular Systems Using Single‐Molecule Force Spectroscopy

Single‐molecule force spectroscopy has been used for the investigation of the rupture behavior of individual metallo‐supramolecular systems. For this purpose, a specifically designed unsymmetrical α,ω‐functionalized poly(ethylene oxide) has been employed for mono‐termination with a terpyridine ligand and subsequently for the attachment onto atomic force microscopy (AFM) tips and microscope slide substrates. Metallo‐supramolecular complexes were formed by the use of ruthenium(III )–ruthenium(II ) chemistry. Vertical stretching with the AFM cantilever ruptured the coordinative bonds. The rupture force of individual bisterpyridine ruthenium(II ) complexes was determined to be 95 pN at a force loading rate of 1 nN s^–1. Simultaneous rupturing of multiple parallel metallo‐supramolecular bonds was also observed. Monte Carlo simulations corroborated the experimental observations. The presented results lay the basis for the application of such metallo‐supramolecular systems in advanced functional nanomaterials.     

Hierarchical Chemical Bonds Contributing to the Intrinsically Low Thermal Conductivity in α‐MgAgSb Thermoelectric Materials

Understanding the lattice dynamics and phonon transport from the perspective of chemical bonds is essential for improving and finding high‐efficiency thermoelectric materials and for many applications. Here, the coexistence of global and local weak chemical bonds is elucidated as the origin of the intrinsically low lattice thermal conductivity of non‐caged structure Nowotny–Juza compound, α‐MgAgSb, which is identified as a new type of promising thermoelectric material in the temperature range of 300–550 K. The global weak bonds of the compound lead to a low sound velocity. The unique three‐centered Mg? Ag? Sb bonds in α‐MgAgSb vibrate locally and induce low‐frequency optical phonons, resulting in “rattling‐like” thermal damping to further reduce the lattice thermal conductivity. The hierarchical chemical bonds originate from the low valence electron count of α‐MgAgSb, with the feature shared by Nowotny–Juza compounds. Low lattice thermal conductivities are therefore highly possible in this series of compounds, which is verified by phonon and bulk modulus calculations on some of the compositions.     

Well‐Defined Protein‐Based Supramolecular Nanoparticles with Excellent MRI Abilities for Multifunctional Delivery Systems

Protein‐based nanoparticles are widely used for effective biomedical applications. The objective of this work is to design series of magnetic resonance imaging (MRI)‐visible cationic supramolecular nanoparticles (PGEA@BSA‐Ad/Gd³⁺) based on bovine serum albumin (BSA) and β‐cyclodextrin‐cored star ethanolamine‐functionalized poly(glycidyl methacrylate) (CD‐PGEA) in the presence of Gd³⁺ ions for multifunctional delivery systems. CD‐PGEA is prepared via atom transfer radical polymerization and ring‐opening reaction. It is found that in the absence of Gd³⁺ ions, CD‐PGEA does not well interact with adamantine‐modified BSA (BSA‐Ad). The well‐defined PGEA@BSA‐Ad/Gd³⁺ supramolecular nanoparticles could be produced through the synergistic actions of the host–guest and electrostatic self‐assemblies by mixing aqueous solutions of CD‐PGEA, BSA‐Ad, and Gd³⁺. In comparison with CD‐PGEA assembly units, such kinds of uniform PGEA@BSA‐Ad/Gd³⁺ supramolecular nanoparticles exhibit better pDNA condensation ability, lower cytotoxicity, higher gene transfection, and easier cellular uptake. In addition, PGEA@BSA‐Ad/Gd³⁺ also produces outstanding MRI abilities, much better than Magnevist (Gd‐diethylenetriaminepentacetate acid). The present design of protein–polymer supramolecular nanoparticles with MRI contrast agents would provide a new way for multifunctional gene/drug delivery systems.     

From Metastable Colloidal Crystalline Arrays to Fast Responsive Mechanochromic Photonic Gels: An Organic Gel for Deformation‐Based Display Panels

An efficient and straightforward method is developed to prepare a mechanochromic photonic gel by fixing the metastable SiO₂ colloidal crystalline array (CCA) in the mixture of ethylene glycol (EG) and poly(ethylene glycol) methacrylate (PEGMA) through photopolymerization. Thanks to the recent fabrication of solvent‐wrapped, metastable CCA, a high volume fraction of EG (46%) is introduced to the photonic gel before particle assembly, but not by swelling after polymerization, which leads to a more deformable composite than most reported opal gels. Compared to traditional photonic gels, this opal gel not only has improved mechanochromic sensitivity to weak external force and extended color tuning range from red to blue (Δλ = 150 nm), but also possesses fast and reversible response in millisecond level (20–200 ms), repeatable reflection signals in cycling and fatigue tests, and good resolution in response to localized deformation, which renders it an ideal deformation‐based photonic display screen. A new trigger system is designed to solve the large deformation causing color fading in conventional mechanochromic gels and brilliant red, green, and blue (RGB) pixels can be conveniently manipulated by ‘pushing’ operations.     

Hexahistidine‐Tagged Single‐Walled Carbon Nanotubes (His6‐tagSWNTs): A Multifunctional Hard Template for Hierarchical Directed Self‐Assembly and Nanocomposite Construction

While a hexahistidine affinity tag can be introduced at protein termini or internal sites by standard molecular biology procedures for purification, immobilization, or labeling of proteins, here the versatility of this concept is exploited for the chemical preparation of novel hexahistidine‐tagged single‐walled carbon nanotubes (His₆‐tagSWNTs), a novel hard template useful for solubilizing, assembling, processing, and interfacing SWNTs in aqueous conditions. Water‐soluble and exfoliated His₆‐tagSWNTs are prepared and fully characterized. This functional molecular module is able to interact via robust physisorption (π?π stacking) with the sidewall of SWNTs and combines the versatility of small, water‐soluble reporters (His₆) for hierarchical directed self‐assembly (HDSA) and construction of nanocomposites. It is demonstrated that metal coordination bonds with Ni(II) can be used for the supramolecular self assembly of His₆‐tagSWNTs, generating complex reticulated networks and architectures. The His₆‐tagSWNTs hard template nanohybrid is further utilized for directed self‐assembly with silica nanoparticles. The versatility of the novel hybrids opens a new era for the rational design, smart (bio)functionalization, processing, interfacing, and self assembling of carbon nanotubes for the construction of multicomposites and more complex systems with controllable spatial organization and programmable properties for a wide range of applications in biology, nanoelectronics, and catalysis.     

Tunable Self‐Assembled Micro/Nanostructures of Carboxyl‐Functionalized Squarylium Cyanine for Ammonia Sensing

Orderly molecular self‐assembly for tunable micro/nanostructures is an effective way to prepare novel functional materials with desired properties. Squarylium cyanine (SCy) dyes have received great attention in the fields of laser, imaging, and optoelectronic device. However, the detailed self‐assembly behavior of SCy has rarely been investigated. In the present work, two SCy derivatives, D1 and D2 , respectively, bearing four and two carboxylic acid groups at different positions are prepared and used as a model system to investigate the molecular self‐assembly, morphology, and optical properties of SCy dyes. The hydrogen‐bonding interactions between the carboxylic acid groups in D1 and D2 are determined with X‐ray diffraction, 2D nuclear magnetic resonance, and Fourier transformation infrared spectroscopy. The two types of hydrogen bonds in D1 cooperating with inherent π–π stacking interaction result in tunable molecular aggregations, which further leads to the transformation between J‐aggregation and H‐aggregation of D1 in the solid state in response to ammonia gas. In all, this work provides a feasible and effective way to study the self‐assembled aggregates of SCy dyes at both molecular and supramolecular levels, and has developed a reversible sensor for ammonia gas detection.     

Two‐Component Molecular Materials of 2,5‐Diphenyloxazole Exhibiting Tunable Ultraviolet/Blue Polarized Emission,Pump‐enhanced Luminescence,and Mechanochromic Response

The development of π‐conjugated molecular systems with high‐efficiency generation of UV and blue light plays an important role in the fields of light‐emitting diodes, fluorescent imaging, and information storage. Herein, supramolecular construction of solid‐state UV/blue luminescent materials are assembled using 2,5‐diphenyloxazole (DPO) with four typical co‐assembled building blocks (1,4‐diiodotetrafluorobenzene, 4‐bromotetrafluorobenzene carboxylic acid, pentafluorophenol, and octafluoronaphthalene). Compared with the pristine DPO sample, the as‐prepared two‐component molecular materials feature ease of crystallization, high crystallinity, enhanced thermal stability and tunable luminescence properties (such as emissive wavelength, color, fluorescence lifetime, and photoluminescence quantum yield) as well as multicolor polarized emission in the UV/blue region. Moreover, pump‐enhanced luminescence and reversible mechanochromic fluorescence (MCF) properties can also be obtained for these molecular solids, which are absent for the pristine DPO sample. Therefore, this work provides a procedure for the facile self‐assembly of ordered two‐component molecular materials with tunable UV/blue luminescence properties, which have potential application in the areas of light‐emitting displays, polarized emission, frequency doubling, and luminescent sensors.     

A Double‐Layer Mechanochromic Hydrogel with Multidirectional Force Sensing and Encryption Capability

Hydrogel‐based soft mechanochromic materials that display colorimetric changes upon mechanical stimuli have attracted wide interest in sensors and display device applications. A common strategy to produce mechanochromic hydrogels is through photonic structures, in which mechanochromism is obtained by strain‐dependent diffraction of light. Here, a distinct concept and simple fabrication strategy is presented to produce luminescent mechanochromic hydrogels based on a double‐layer design. The two layers contain different luminescent species—carbon dots and lanthanide ions—with overlapped excitation spectra and distinct emission spectra. The mechanochromism is rendered by strain‐dependent transmittance of the top‐layer, which regulates light emission from the bottom‐layer to control the overall hydrogel luminescence. An analytical model is developed to predict the initial luminescence color and color changes as a function of uniaxial strain. Finally, this study demonstrates proof‐of‐concept applications of the mechanochromic hydrogel for pressure and contact force sensors as well as for encryption devices.     

Enhanced DNA Sequencing Performance Through Edge‐Hydrogenation of Graphene Electrodes

The use of graphene electrodes with hydrogenated edges for solid‐state nanopore‐based DNA sequencing is proposed, and molecular dynamics simulations in conjunction with electronic transport calculations are performed to explore the potential merits of this idea. The results of the investigation show that, compared to the unhydrogenated system, edge‐hydrogenated graphene electrodes facilitate the temporary formation of H‐bonds with suitable atomic sites in the translocating DNA molecule. As a consequence, the average conductivity is drastically raised by about 3 orders of magnitude while exhibiting significantly reduced statistical variance. Furthermore, the effect of the distance between opposing electrodes is investigated and two regimes identified: for narrow electrode separation, the mere hindrance due to the presence of protruding hydrogen atoms in the nanopore is deemed more important, while for wider electrode separation, the formation of H‐bonds becomes the dominant effect. Based on these findings, it is concluded that hydrogenation of graphene electrode edges represents a promising approach to reduce the translocation speed of DNA through the nanopore and substantially improve the accuracy of the measurement process for whole‐genome sequencing.     

Water‐Soluble Conjugated Molecule for Solar‐Driven Hydrogen Evolution from Salt Water

Photocatalytic hydrogen evolution is an attractive method for the acquisition of clean and sustainable energy with the use of solar power. Most reported studies have been carried out in scarce pure water. Therefore, the development of an artificial photosynthesis system that works perfectly with the earth's abundant seawater would be attractive. Herein, a supramolecular strategy for photocatalytic hydrogen production from the simulated seawater under sunlight irradiation (AM 1.5G, 100 mW cm^?2) is presented using a water‐soluble, conjugated molecule as the photosensitizer and the photodeposited Pt nanoparticles as the catalyst. Inspired by the natural photosynthesis system, unprecedented advantage of the chloride ions in seawater is taken and the formation of supramolecular structure is promoted by electrostatic interactions between chloride ions and the fine‐designed PorFN, which further facilitates the loading of Pt nanoparticles and multielectron transfer. As a result, a hydrogen evolution rate of 10.8 mmol h^?1 g^?1 is achieved in the simulated seawater. Moreover, the photocatalytic activity shows relatively low dependence on the light intensity, which is of great importance for practical applications.     

Supramolecular Surface Chemistry: Substrate‐Independent,Phosphate‐Driven Growth of Polyamine‐Based Multifunctional Thin Films

The ability to engineer surfaces at the supramolecular level by controlled integration of specific chemical units through substrate‐independent methodologies represents one of the new paradigms of contemporary materials science. Here, a method is reported to form multifunctional supramolecular coatings through simple dip‐coating of substrates in an aqueous solution of polyamine in the presence of phosphate anions. The chemical richness and versatility of polyamines are exploited as phosphate receptors to form thin functional films on a broad variety of substrates, ranging from metal to carbonaceous surfaces. It is shown that the simple derivatization of pendant amino groups of polyallylamine precursors with different chemical groups can endow films with predefined responsiveness or multiple functions—this translates into one‐pot and one‐step preparation of substrate‐adherent films displaying built‐in functions. It is believed that the flexibility, speed, and versatility with which this method provides such robust functional films make it very attractive for preparing samples of fundamental and technological interest.     

Bimetal Schottky Heterojunction Boosting Energy‐Saving Hydrogen Production from Alkaline Water via Urea Electrocatalysis

Hydrogen production via water electrocatalysis is limited by the sluggish anodic oxygen evolution reaction (OER) that requires a high overpotential. In response, a urea‐assisted energy‐saving alkaline hydrogen‐production system has been investigated by replacing OER with a more oxidizable urea oxidation reaction (UOR). A bimetal heterostructure CoMn/CoMn₂O₄ as a bifunctional catalyst is constructed in an alkaline system for both urea oxidation and hydrogen evolution reaction (HER). Based on the Schottky heterojunction structure, CoMn/CoMn₂O₄ induces self‐driven charge transfer at the interface, which facilitates the absorption of reactant molecules and the fracture of chemical bonds, therefore triggering the decomposition of water and urea. As a result, the heterostructured electrode exhibits ultralow potentials of ?0.069 and 1.32 V (vs reversible hydrogen electrode) to reach 10 mA cm^?2 for HER and UOR, respectively, in alkaline solution, and the full urea electrolysis driven by CoMn/CoMn₂O₄ delivers 10 mA cm^?2 at a relatively low potential of 1.51 V and performs stably for more than 15 h. This represents a novel strategy of Mott–Schottky hybrids in electrocatalysts and should inspire the development of sustainable energy conversion by combining hydrogen production and sewage treatment.     

A Water‐Soluble Mechanochromic Luminescent Pyrene Derivative Exhibiting Recovery of the Initial Photoluminescence Color in a High‐Humidity Environment

Switching of the luminescence properties of molecular materials in response to mechanical stimulation is of fundamental interest and also has a range of potential applications. Herein, a water‐soluble mechanochromic luminescent pyrene derivative having two hydrophilic dendrons is reported. This pyrene derivative is the first example of a mechanochromic luminescent organic compound that responds to relative humidity. Mechanical stimulation (grinding) of this pyrene derivative in the solid state results in a change of the photoluminescence from yellow to green. Subsequent exposure to water vapor induces recovery of the initial yellow photoluminescence. The color change is reversible through at least ten cycles. It is also demonstrated that this compound can be applied as a mechano‐sensing material in frictional wear testing for grease, owing to its immiscibility in non‐polar solvents and its non‐crystalline behavior. Transmission electron microscope and atomic force microscope observations of samples prepared from dilute aqueous solutions of the pyrene derivative on suitable substrates, together with dynamic light scattering measurements for the compound in aqueous solution, indicate that this amphiphilic dumbbell‐shaped molecule forms micelles in water.     

Nanostructured Crystalline Comb Polymer of Perylenebisimide by Directed Self‐Assembly: Poly(4‐vinylpyridine)‐pentadecylphenol Perylenebisimide

Well defined nanostructured polymeric supramolecular assemblies are formed when an asymmetric perylenebisimide substituted with ethylhexyl chains on one end and functionalized with 3‐pentadecylphenol at the other termini ( PDP‐UPBI ) is complexed with poly(4‐vinylpyridine) (P4VP) via a non‐covalent specific interaction such as hydrogen‐bonding. The resulting P4VP(PDP‐UPBI) _n complexes are fully solution processable. The bulk structure and morphologies of the supramolecular film studied using small angle and wide angle X‐ray scattering reveals highly crystalline nature of the complex. Thin film morphology of the 1:1 complex analyzed using transmission electron microscopy shows uniform lamellar structures in the domain range of 5–10 nm. A clear trend of improved electrical parameters in P4VP(PDP‐UPBI) system compared to pristine ( PDP‐UPBI ) is observed from space charge limited current measurements. In short, a simple and facile method to obtain spatially defined organization of n‐type semiconductor perylenebisimide molecules using hydrogen bonding interactions with P4VP as the structural motif is showcased herein.