Functional template directed synthesis of hybrid siliceous fluorescent vesicle (HSFV) is fabricated by using fluorescent vesicle as a built-in template. The template vesicle is the ionic self-assembly of an aggregation-induced emission (AIE) fluorogen. Upon depositing folic acid modified silica shell on its surface, the obtained HSFVs display low cytotoxicity, significant fluorescence, and targeted drug delivery toward cancer cells. Furthermore, the wall-thickness of the HSFVs can be controlled via altered concentration of silica source. This is the first report of HSFV employing the template vesicle as a built-in fluorescent agent, which represents a good example of rational design for an effective diagnostics, and may open up a new avenue for precision medicine.Keywords: aggregation-induced emission; fluorescent vesicles; hybrid self-assembly; precision medicine; template;

We report in this work the formation of fluorescence and MRI bimodal imaging nanoparticles achieved by electrostatic self-assembly. The nanoparticles are micelles formed with Gd3+ ion, a bisligand that contains aggregation induced emission (AIE) group, and a block copolymer. The coordination between the Gd3+ ion and the bisligand produces a negatively charged coordination complex, which interacted with the positive-neutral block copolymer to form polyion micelles. The micelles exhibit considerable fluorescence owing to the rotation restriction of the AIE group; meanwhile, the longitudinal relaxation of water was significantly slowed down which provide T1 contrast for magnetic resonance imaging. In vitro fluorescence imaging and in vivo MRI measurements verified this micelle indeed exhibit dual imaging ability. We expect that this orthogonal imaging may provide more accurate diagnosis in practical applications and will pave the way for the development of an advanced technique for diagnosis.

Advanced materials are often based on smart molecular self-assemblies that either respond to external stimuli or have hierarchical structures. Approaches to this goal usually stem from complicated molecular design and difficult organic synthesis. In this invited feature article, we demonstrate that desired molecular self-assemblies can be made conveniently by introducing simple functional molecules into amphiphilic systems. We show that upon introducing specific small molecules which serve as responders, modulators, or even building blocks, smart supramolecular architectures can be achieved which avoid complicated organic synthesis. We expect that this could be a general and economical way to produce advanced materials in the near future.

Switching between association and dissociation is the well-known strategy for constructing responsive materials based on the host–guest complexes of cyclodextrins (CDs). In this work, we report that temperature may also trigger self-assembly transition in the supramolecular system composed of sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD) at a molar ratio of 1:2. We reported previously that, at this ratio, SDS and β-CD form a channel-type SDS@2β-CD supramolecular unit, which further self-assembles into non-amphiphilic vesicles and microtubes driven by hydrogen bonding. Here, we report that the vesicles and microtubes can be reversibly switched between each other upon decreasing and increasing temperature. Control experiments in heavy water suggest that water molecules play a dominating role in the hydrogen bonding between SDS@2β-CD supramolecular units at lower concentration and higher temperature. Under opposite conditions, the hydrogen bonding between CDs is dominating. Therefore, for the 5% system, we observed a vesicle to microtube transition with a decreasing temperature, whereas for the 10% system, we observed the reverse process. Both processes are reversible. This is not only an example of temperature-triggered responsiveness in non-amphiphilic self-assemblies but also a new mode of responsiveness for the host–guest inclusion systems based on CDs. This temperature-responsive process is anticipated to shed light on the design and development of novel advanced materials.

Perylene derivatives are excellent n-type dyes that display superior potential in optical and electronic materials. Significant efforts have been endeavored toward structural modification of the perylene skeleton. Herein, we showed that the simple coordinating self-assembly of perylenetetracarboxylate could already generate excellent one-dimensional perylene-based self-assembly, and its structural details could be simply tailored by concentration. Microbelts with high potential energy are formed at concentrations below 1 mM, whereas nanobelts with low potential energy appear at higher concentrations. The coordination stoichiometry was 1 : 1 in the microbelt and 1 : 2 in the nanobelt, which resulted in drastic material properties, such that the microbelt with 1 : 1 coordinated PTC and Ni2+ displayed a conductivity 80 times that of the 1 : 2 coordinated nanobelt, whereas the latter exhibited 4 times higher specific surface area, significant fluorescence, and polarized light transmittance. These findings not only unveil a scenario of the coordinating self-assembly of perylenetetracarboxylate, but also show that concentration can act as a powerful tool to tailor the function of self-assembled materials.

Fabrication of solid white luminescent materials is a challenging topic. In this work we report that upon combining the advantages of aggregation induced emission and reversible coordination polymers, solid white luminescent films with the CIE coordinates of (0.335, 0.347) and external quantum efficiencies of up to 11.74% can be achieved via layer-by-layer assembly. In particular, the ratio of the R(red) G(green) B(blue) elements can be rationally controlled via concentration, demonstrating the advantage of reversible coordination polymers in the fabrication of functional materials. The white emission of the solid thin film displays excellent stability against temperature, pH, and explosion materials, but exhibits specific detection for Cl2, suggesting its great potential for application as both a robust luminescent material and a chemical sensor.

Propeller-shaped molecules have been recognized to display fantastic AIE (aggregation induced emission), but they can hardly self-assemble into nanostructures. Herein, we for the first time report that ionic complexation between a water-soluble tetrapheneyl derivative and an enzyme substrate in aqueous media produces a propeller-shaped supra-amphiphile that self-assembles into enzyme responsive fluorescent vesicles. The supra-amphiphile was fabricated upon complexation between a water-soluble propeller-shaped AIE luminogen TPE-BPA and myristoylcholine chloride (MChCl) in aqueous media. MChCl filled in the intramolecular voids of propeller-shaped TPE-BPA upon supra-amphiphile formation, which endows the supra-amphiphile superior self-assembling ability to the component molecules thus leading to the formation of fluorescent vesicles. Because MChCl is the substrate of cholinesterases, the vesicles dissemble in the presence of cholinesterases, and the fluorescent intensity can be correlated to the level of enzymes. The resulting fluorescent vesicles may be used to recognize the site of Alzheimer’s disease, to encapsulate the enzyme inhibitor, and to release the inhibitor at the disease site.Keywords: AIE; enzyme-responsive; fluorescent vesicle; self-assembly; supra-amphiphile

Binding of metal ions to the head of a coordinating amphiphile TTC4L substantially changes the emission color of the terthiophene group attached to the chain end via a conformation triggered self-assembly. This is in analogy with the allostery of proteins in which binding a ligand to one site may affect its performance at another site through conformational change.

In this work we report the chain length dependent behavior of the nonamphiphilic supramolecular building blocks based on the host–guest inclusion complexes of alkanes and β-cyclodextrins (β-CD). 1H NMR, ESI-MS, and SAXS measurements verified that upon increasing the chain length of alkanes, the building blocks for vesicle formation changed from channel type 2alkane@2β-CD via channel type alkane@2β-CD to non-channel type 2alkane@2β-CD. FT-IR and TGA experiments indicated that hydrogen bonding is the extensive driving force for vesicle formation. It revealed that water molecules are involved in vesicle formation in the form of structural water. Upon changing the chain length, the average number of water molecules associated with per building block is about 16–21, depending on the chain length.

Adaptive molecular self-assemblies provide possibility of constructing smart and functional materials in a non-covalent bottom-up manner. Exploiting the intrinsic properties of responsiveness of non-covalent interactions, a great number of fancy self-assemblies have been achieved. In this review, we try to highlight the recent advances in this field. The following contents are focused: (1) environmental adaptiveness, including smart self-assemblies adaptive to pH, temperature, pressure, and moisture; (2) special chemical adaptiveness, including nanostructures adaptive to important chemicals, such as enzymes, CO2, metal ions, redox agents, explosives, biomolecules; (3) field adaptiveness, including self-assembled materials that are capable of adapting to external fields such as magnetic field, electric field, light irradiation, and shear forces.

Poisonous industrial wastes have become the major threat to people's health. Recycling these components and making them into useful materials is needed urgently. We report that with the assistance of dodecylamine (DA), the chelating metal pollutant Cu-EDTA can be made into the lamellar Cu-EDTA@2DA supramolecular material. Since Cu-EDTA is notorious for its highly solubility and stability in water, this work for the first time showed that it can be made into supramolecular material which precipitated out from water. Furthermore, this Cu-EDTA@2DA supramolecular material shows excellent efficiency in adsorbing organic dyes, and can be recycled upon desorption of dyes in N,N-dimethylformamide (DMF). As far as we know, this is the first case of using industrial waste to build well-defined useful supramolecular materials. We expect that the strategy of ‘fight poison with poison’ can be an effective and economic approach to treat environmental pollution.

In situ characterization of the structure of reversible coordination polymers remains a challenge because of their dynamic and concentration-responsive nature. It is especially difficult to determine these structures in their self-assemblies where their degree of polymerization responds to the local concentration. In this paper, we report on the structure of reversible lanthanide coordination polymers in electrostatic assemblies using time-resolved luminescence (TRL) measurement. The reversible coordinating system is composed of the bifunctional ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4) and europium ion Eu3+. Upon mixing with the positively charged diblock copolymer poly(2-vinylpyridine)-b-poly(ethylene oxide) (P2VP41-b-PEO205), electrostatic polyion micelles are formed and the negatively charged L2EO4–Eu coordination complex simultaneously transforms into coordination “polymers” in the micellar core. By virtue of the water-sensitive luminescence of Eu3+, we are able to obtain the structural information of the L2EO4–Eu coordination polymers before and after the formation of polyion micelles. Upon analyzing the fluorescence decay curves of Eu3+ before and after micellization, the fraction of Eu3+ fully coordinated with L2EO4 is found to increase from 32 to 83%, which verifies the occurrence of chain extension of the L2EO4–Eu coordination polymers in the micellar core. Our work provides a qualitative picture for the structure change of reversible coordination polymers, which allows us to look into these “invisible” structures.

The ability to modulate amphiphilic aggregation reversibly with external stimuli, especially using light as a trigger, is of great importance. This has greatly contributed to the development of applications using self-assembly. However, most previously described systems are based on a specific molecular design and have shown difficultly in their application to light-inert aggregation. Here, we developed a general and effective approach to control the morphology of amphiphilic aggregates by light, which is suitable for different assemblies such as micelles, vesicles, and helixes. Our strategy is to construct a photoresponsive factor into light-inert self-assemblies. On the basis of the different capabilities to form host–guest inclusions between photoresponsive azobenzene sodium and light-inert molecules with cyclodextrin, the transformation of the corresponding amphiphilic aggregation can be controlled easily and reversibly by light stimuli. Not only the nanostructure of the aggregates but also the phase behavior, such as gel formation, can be modulated upon light irradiation using this method.

Self-assemblies dominated by coordination interaction are hardly responsive to thermal stimuli. We show that in case the coordinating mode changes with temperature, the resultant assemblies also exhibit temperature dependence. The self-assemblies are constructed with perylene tetracarboxylate and metal ions. Compounds containing a perylene skeleton often self-assemble into micro-belts, which is also true for the combination of perylene tetracarboxylate and metal ions. However, a unique pinecone structure was observed upon increasing the temperature of the coordinating system. The structural transition is triggered by the change of coordinating mode between the carboxylate group and the metal ion. At low temperature, intermolecular coordination occurs which favours the growth of the coordinating self-assembly along the long axis of the perylene. However, upon the elevation of temperature, the coordination is overwhelmed by intra-molecular mode. This is against the extension of the coordinating assembly due to the loss of connection between neighbouring perylenes. As a result, the pinecone structure is observed. We expect that the cases introduced in this work may inspire the design of structurally controllable temperature-dependent soft materials based on coordinating self-assembly.

Via the mixed self-assembling procedure, solid multicolour emission materials based on an amphiphilic terthiophene compound are obtained from a unimolecular platform. Upon controlling the concentration of the cationic surfactant dodecyltriethyl ammonium bromide (DEAB) in the precipitate–monomer equilibrium system of the terthiophene compound TTC4L, mixed self-assembly of TTC4L–DEAB results in diverse structures (including plates, spheres, and needles) with different emission colours. The multicolour emissions are triggered by the different distances between the terthiophene groups in these mixed self-assemblies. Each distance corresponds to a specific molecular state of terthiophene groups, so that emissions corresponding to the monomers, excimers, and aggregates are obtained. Upon variation of the ratio of DEAB and TTC4L, the relative fraction of emissions corresponding to the monomers, excimers, and aggregates of TTC4L changes. This approach may act as a simple method to control the stacking mode of the oligothiophene group which is anticipated to realize unimolecular-platform multicolour emissions.

Suppressing the overproduction of harmful active oxygen species is very important. We report that the production of 1O2 from TPPS can be reduced upon the formation of polyion micelles with PMVP41-b-PEO205. The amount of 1O2 can be controlled successfully, which affords a new thinking of disease treatment and oxidation resistance of cells.

The interaction between SDS and the swollen lamellar phase of an A-B-A type nonionic siloxane surfactant IM-22 in 60 % glycerol has been investigated with macroscopic phase observation, FF-TEM, SAXS, conductivity, and rheology experiments. Without addition of SDS, 20 % IM-22 forms highly swollen planar lamellar phase stabilized by strong thermal undulations. Upon addition of 1 mM SDS, the lamellae were transformed into giant multilamellar vesicles. The size of the vesicles decreases with increasing the amount of SDS below 5 mM whereas the number density of the vesicles increases. Further increasing the concentration of SDS leads to break of the vesicles. In this self-assembly transition process, the viscosity of the system exhibits maximum at 5 mM SDS, where the system owns property of gels. Conductivity measurements suggest that SDS starts to bind IM-22 at a concentration below 2 mM, but SAXS results reveal that the interlamellar spacings were not affected up to 5 mM. This was explained by the special interactions in this system. On the one hand, the ionization degree of SDS in 60 % glycerol is very low due to the low dielectric constant, which results in lower charge density in the lamellae. Therefore, thermal undulations dominate the electrostatic forces at SDS concentration below 5 mM. On the other hand, the mutual phobic nature of SDS with IM-22 allows break of the lamellae at higher SDS concentrations.

It is hard to obtain spatially ordered nanostructures via the polyion complexation process due to the inherent flexibility of polymers and isotropicity of ionic interactions. Here we report the formation of polyion assemblies with well-defined, periodically regular internal structure by imparting the proper stiffness to the molecular tile. A stiff bisligand TPE-C4-L2 was designed which is able to form a negatively charged supramolecular polyelectrolyte with transition metal ions. This supramolecular polyelectrolyte slowly self-assembled into polydispersed flat sheets with cocoon-like patterns. Upon the addition of an oppositely charged ordinary polyelectrolyte, the polydispersed cocoons immediately transformed into ultralong, uniform nanoladders as a result of matched ionic density recognition. The supramolecular polyelectrolytes assembled side-by-side, and the negative charges aligned in an array. This structure forced the positively charged polymers to lie along the negative charges so that the perpendicular arrangement of the oppositely charged chains was achieved. Such precise charge recognition will provide insight into the design of advanced materials with hierarchical self-assembled structures.

In this paper, we report on the luminescence of europium by directly exciting europium ions with visible light in aqueous medium. Upon replacing all the water molecules that coordinate around a central europium ion with a ditopic ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4), the quenching from water molecules is efficiently eliminated, offering considerable europium emission. By stoichiometrically mixing with a positively charged block polyelectrolyte, the negatively charged L2EO4–Eu coordinating complex can be transformed into a coordination ‘polymer’, which simultaneously forms electrostatic micelles with further enhanced europium fluorescence emission, owing to the increased fraction of L2EO4-coordinated Eu(III) as revealed by the fluorescence lifetime measurements. This approach avoids the use of the antenna effect that often utilizes UV light as the irradiation source. We further use those micelles for bio-imaging, and for the first time demonstrate the use of directly excited Eu-containing nano-probes for in vivo fluorescence imaging in small animals under visible excitation. Although literature results have shown that the direct excitation of europium ions in water may lead to emissions in the presence of coordinating ligands, those emissions were too weak to be applied due to the remaining water molecules in the coordination sphere. Our work points out that the direct excitation of europium can generate considerable europium emission given that all the water molecules in the coordination sphere are excluded, which does not only greatly reduce tedious lab work in synthesizing antenna molecules, but also facilitates the application of europium in aqueous medium under visible light.

Hierarchical molecular self-assembly offers many exotic and complicated nanostructures which are of interest in nanotechnology and material science. In the past decade, various strategies leading to hierarchical molecular self-assemblies have been developed. In this review we summarize the recent advances in the creation and application of solution-based self-assembled nanostructures that involve more than one level of arrangement of building blocks. The strategies for construction hierarchical self-assembled structures and the advantages brought up by these assemblies are focused on. The following contents are included: (1) general approaches to fabricate hierarchical self-assembly, including self-assemblies based on supramolecules and specially designed block copolymers; (2) the advantages brought about by the hierarchical self-assembly, including the fabrication of special self-assembled structures, rich responsiveness to external stimuli, and the materials’ performance.

Switching between association and dissociation is the well-known strategy for constructing responsive materials based on the host–guest complexes of cyclodextrins (CDs). In this work, we report that temperature may also trigger self-assembly transition in the supramolecular system composed of sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD) at a molar ratio of 1:2. We reported previously that, at this ratio, SDS and β-CD form a channel-type SDS@2β-CD supramolecular unit, which further self-assembles into non-amphiphilic vesicles and microtubes driven by hydrogen bonding. Here, we report that the vesicles and microtubes can be reversibly switched between each other upon decreasing and increasing temperature. Control experiments in heavy water suggest that water molecules play a dominating role in the hydrogen bonding between SDS@2β-CD supramolecular units at lower concentration and higher temperature. Under opposite conditions, the hydrogen bonding between CDs is dominating. Therefore, for the 5% system, we observed a vesicle to microtube transition with a decreasing temperature, whereas for the 10% system, we observed the reverse process. Both processes are reversible. This is not only an example of temperature-triggered responsiveness in non-amphiphilic self-assemblies but also a new mode of responsiveness for the host–guest inclusion systems based on CDs. This temperature-responsive process is anticipated to shed light on the design and development of novel advanced materials.

Advanced materials are often based on smart molecular self-assemblies that either respond to external stimuli or have hierarchical structures. Approaches to this goal usually stem from complicated molecular design and difficult organic synthesis. In this invited feature article, we demonstrate that desired molecular self-assemblies can be made conveniently by introducing simple functional molecules into amphiphilic systems. We show that upon introducing specific small molecules which serve as responders, modulators, or even building blocks, smart supramolecular architectures can be achieved which avoid complicated organic synthesis. We expect that this could be a general and economical way to produce advanced materials in the near future.

Bioinspired cell deformation aids in the design of smart functional molecular self-assemblies. We report on a system of bacteria-like vesicles which release entrapped drug upon developing hairs triggered by UV irradiation, just like cilia stretching from the surface of bacteria. The formation of cilia leads to a less intact membrane, which allows release of entrapped drug. This bioinspired design created a smart nanocarrier that releases the payload via deformation rather than complete breaking.Keywords: azobenzene; bioinspired structure; controlled release; cyclodextrin; photoresponsive; self-assembly; vesicle;

This article presents a facile strategy to combine Eu3+ and Gd3+ ions into coacervate core micelles in a controlled way with a statistical distribution of the ions. Consequently, the formed micelles show a high tunability between luminescence and relaxivity. These highly stable micelles present great potential for new materials, e.g. as bimodal imaging probes.

One of the recent challenges in nanotechnology is the development of ‘catalyzed self-assembly’. So far successful cases are still scarce. In this work we report the delicate case of a cyclodextrin (CD) catalyzed self-assembly of the terthiophene-containing amphiphile TTC4L into microspheres. TT4CL can form precipitates when CDs are not present, whereas it self-assembles into microspheres in the presence of CDs. The CDs were not involved into the microspheres, but they stayed in the supernate in the form of the TTC4L@CD inclusion complex. This complex may further transform into microspheres in the presence of a competitive guest. ITC and 1H NMR measurements suggest that part of the terthiophene group binds weakly with CDs. We expect that this weak binding interferes with the quick stacking of TTC4L, so that a ‘slow’ arrangement of the terthiophene moiety becomes possible which finally leads to the formation of microspheres. Our results not only provide a new solid example of a catalyzed molecular self-assembly, but also envisage a new paradigm for the possible role of CDs in supramolecular chemistry.

In this paper, we report on the impact of the structure of ligands on the luminescence enhancement of Eu(III) by directly exciting Eu(III) with visible light in aqueous media. Upon replacing the water molecules that coordinated around a Eu3+ ion with a ditopic ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4) or ethylenediaminetetraacetic acid disodium salt (EDTA), significant luminescence can be obtained. L2EO4 may occupy all 9 coordinating sites of a Eu3+ ion at proper L2EO4/Eu ratios, whereas EDTA only occupies 6 of them with 3 sites left for water at various EDTA/Eu ratios. These coordinated water molecules quench the fluorescence of EDTA–Eu complexes drastically so that the luminescence is about 30 times lower than that of the L2EO4–Eu system. Furthermore, the negatively charged L2EO4/Eu = 3/2 coordinated complex can be further transformed into coordination ‘polymers’ by mixing with a positively charged block polyelectrolyte, which forms electrostatic micelles with further enhanced luminescence. The emission of the EDTA–Eu complex is not influenced by the addition of polymers due to the formation of stable small 1:1 EDTA–Eu complex which doesn't change with increasing concentration. Our work points out that the L2EO4–Eu system is superior to the EDTA–Eu system in creating visible light sensitized Eu(III) luminescence, and the emission of Eu(III) can be indeed significantly enhanced to an applicable level by excluding all the water molecules in the coordination sphere of Eu(III).

Currently there is intense interest in decreasing the operating potential for hydrogen evolution in water electrolysis to considerably decrease the energy cost. In this work we report a significant decrease of the operating potential for hydrogen evolution from neutral water mediated by an iron based soft coordination polymer (FeIII-SCSP). The creation of a local acidic environment with a thickness in the range of ∼40 nm on the surface of a glassy carbon electrode allows enrichment of H+ on the GCE, so that the operating potentials were effectively decreased. This strategy thus generates a new paradigm for lowering the operating potential of hydrogen generation from neutral water without the use of additional acids and organic cosolvents.

The construction and regulation of one-dimensional (1-D) structure have been fully investigated in anionic azo dyes and cationic surfactants mixed systems. Anionic azo dyes with different charge numbers and different size of conjugated groups were selected. Analogously, cationic alkyl quaternary ammoniums surfactants with different chain length, charges on the head, and types of the surfactants were tested. By studying the relationship between molecular structure and intermolecular interactions in a controlled way, it was found that 1-D self-assembly is a process that affected by multiple interactions, including electrostatic attractions, hydrophobic interactions, and potential π–π staking. Besides, the symmetry of the molecules also affects the morphology of the assemblies.Combination of steric effect, π–π stacking, electrostatic and hydrophobic interaction, the packing model of dye and surfactant molecules in the 1-D nano-structures has been suggested.Highlights► 1-D structures were found in azo dyes and cationic surfactants mixed systems. ► Helixes were found in one of the mixed systems. ► The regulation of the formation of these 1-D structures has been investigated.

It has long been considered that the addition of cyclodextrins (CDs) disfavors the self-assembly of surfactants in dilute solutions since the hydrophobic effect is destroyed upon the formation of the hydrophiphilic CD/surfactant inclusion complex. However, in this work, we found that β-CD/nonionic surfactant inclusion complexes are able to self-assemble into vesicles in dilute solutions, namely in solutions with concentration lower than the CMC of surfactants. When using Tween 20 as a model surfactant, HNMR and MS measurements indicate that the building block for the vesicles is the channel type Tween 20@2β-CD inclusion complex. Structure and IR analysis suggests that the self-assembly of hydrophilic Tween 20@2β-CD is driven by H-bonds between both the headgroup of Tween 20 and the hydroxyl groups of β-CD. The self-assembly of the inclusion complex between the β-CD and the nonionic surfactant in dilute solution is found to be a general phenomenon. Undoubtedly, surfactant@2β-CD inclusion complex can be a novel building block for nonamphiphilic self-assembly, which provides a new physical insight for the influence of cyclodextrins on the self-assembly of surfactants.

We present here a simple molecular assembly approach to multicolor emissions based on a unimolecular platform of a terthiophene-containing amphiphile TTC4L. The amphiphiles self-assemble into vesicles in solution which exhibit a blue emission. Upon controlling the distance between the fluorescent terthiophene groups by transformation of the self-assembly of TTC4L molecules into their co-assembly with surfactants, the color of the emissions can be continuously tailored which covers most of the visible region. Since the multi-colors were obtained without any structural modification on the fluorescent molecules, we have demonstrated a real unimolecular platform for fabricating multicolor emissions. In contrast, only dual emissions can be obtained from TTC4L using host–guest chemistry. As a simple approach of ‘tunable emissions’, this surfactant-assisted unimolecular platform opens a new vista for the application of molecular assemblies in advanced light emitting materials.

In this paper, we report on an extremely pH sensitive fluid based on a simple ammonium surfactant synthesized in our lab. The fluid was obtained simply by the addition of NaOH into a 100 mM N-cetyl-N,N-dihydroxyethylammonium bromide (CDHEAB) aqueous solution. The viscosity of this aqueous solution may change 106-fold within a narrow pH range of 4.97 to 5.78. The extremely pH-sensitive rheological performance was attributed to the critical molecular structure that allows the combination of strong hydrophobic interactions and effective hydrogen bonding upon protonation. Based on the understanding of the molecular origin of this superior rheological behavior, we are able to manipulate the responsive threshold value of the pH, which provides great advantage in the fine tuning and design of pH responsive fluids with desired pH values. Our results demonstrate that easy-to-process, extremely pH sensitive fluids can be produced by proper molecular design which covers the delicate balance between hydrophobic interactions and the electrostatic effect.

We report in this paper a dual catalytic effect of water soluble soft coordination supramolecular polymers (SCSPs) based on Fe3+ and a bis-ligand. Upon assembling the Fe(III)-SCSPs onto electrodes via layer-by-layer technique, the electroactive films may lower the half-wave potential for all the tested molecules and enhance the current for neutral or oppositely charged electroactive species. The decrease of the half-wave potential was attributed to the mediation of the Fe(III)-SCSPs in electron transferring, whereas the enhancement of current is a consequence of accumulation of electrons in the films. We verified that this dual catalytic effect is general to neutral and cationic redox active molecules, and can be used to detect hydrogen peroxide owing to the significant enlargement of catalytic current. Our results proved that the water soluble soft coordination supramolecular polymers containing metal centers are indeed a novel class of advanced catalytic materials, which may open a new vista on the design and study of materials of this class.

We report in this paper direct observation of redox-induced uptake of a charged species in micelles with a complex coacervate core, using a system consisting of negatively charged iron-coordination polymers and positively charged-b-neutral block co-polyelectrolytes. Neutral, charge-balanced micelles are first prepared by stoichiometric mixing of the oppositely charged components. Upon a redox stimulus, the micelles develop excess charges, which (as proposed in our previous work) most likely lead to sequestration of oppositely charged species, as the charge balance has to be restored. In this work we verify this prediction by using a rigid, rod-like iron coordination polymer, namely, the positively charged MEPE, as the species to be taken up. After uptake of this rigid cargo, the morphology of the micelles was found to transform from spheres to banana-shaped bundles and fibers, which clearly indicate the uptake of MEPE in the micellar core. Our result proves that the redox stimulus indeed induces excess charges in the core, which forces the self-assembled particles to change both composition and shape. As an interesting example of “adaptive self-assembly”, our findings also pave the way to novel redox-triggered uptake and release systems.Keywords: coordination polymers; electrostatic micelles; redox; uptake

We report in this paper the release and uptake of charged payloads in redox responsive electrostatic micellar systems composed of negatively charged soft iron coordination suprapolymers and positively charged block copolymers. This micellar system was reported in our previous work (Yan, Y.; Lan, Y. R.; de Keizer, A.; Drechsler, M.; Van As, H.; Stuart, M. A. C.; Besseling, N. A. M. Redox responsive molecular assemblies based on metallic coordination polymers. Soft Matter, 2010, 6, 3244–3248), where we proposed that the system can be used as a redox-triggered release and uptake system. In this paper, we successfully selected a negatively charged fluorescent dye, eosin B, as a model cargo to track the release and upload process. Upon being compacted in the mixed micelles of coordination polymers and diblock copolymers, the fluorescence of eosin B was effectively quenched. Once reduction was conducted, excess negative charges were introduced to the mixed micelles so that the negatively charged eosin B was expelled out which was accompanied by the recovery of the fluorescence. The free negatively charged eosin B was able to be taken up by the Fe(II) micelles again if oxidation of Fe(II) was carried out since excess positive charges were produced. Beside eosin B, other charged species, such as various charged macromolecules, were tested to be capable of uptake and release by this micellar system. We suppose this system can be potentially used as a redox-gated micellar carrier for uptake and release of charged cargos.

We report on the detection of micellar growth in anionic, cationic, and catanionic surfactant systems using a novel surfactant type fluorescence probe, sodium 12-(N-dansyl)amino-dodecanate (12-DAN-ADA). The fluorescent group was incorporated in the tail of the surfactant which tethers the fluorescent group deep inside the apolar micellar cores. The fluorescence anisotropy of 12-DAN-ADA was found to be very sensitive for directly detecting the micellar growth in micelles containing oppositely charged surfactants, including cationic CTAB systems and mixed systems of oppositely charged surfactants (DEAB/SDS); in regard to the like charged SDS micellar systems, the sensitivity can be greatly enhanced by addition of a water soluble quencher which quenches the background fluorescence from the equilibrium population of free 12-DAN-ADA.Graphical abstractThe growth of surfactant micelles can be sensitively detected by measuring the fluorescence anisotropy or the fluorescence maximum of a surfactant type fluorescence probe 12-DAN-ADA.Research highlights► A novel anionic surfactant type fluorescence probe with the fluorescent group attached to the end of the chain was designed. ► The fluorescent group can be tethered deep into the micellar cores. ► The growth of micelles can be detected by using this new type of fluorescence probe. ► The sensibility of the probe can be enhanced considerably if the background fluorescence is quenched by water soluble quenchers.

CDs may have promising functions in surfactant systems far beyond simply being disadvantageous to the formation of micelles. In this paper we review the recent literature and our work on the interesting effect of CDs on amphiphilic systems, especially on the concentrated single surfactant systems and catanionic surfactant mixed systems, both of them have been scarcely focused upon in the literature. In concentrated single surfactant systems, the 2:1 surfactant–CD inclusion complexes may form hierarchical self-assemblies such as lamellae, microtubes, and vesicles which are driven by hydrogen bonding. In nonstoichiometrically mixed catanionic surfactant systems, CDs behave as a stoichiometry booster that always selectively binds to the excess component so as to shift the mixing ratio to electro-neutral in the aggregates. In this way, CDs reduce the electrorepulsion in the aggregates and trigger their growth. Upon analysis of literature work and our own results, we expect that a new era focusing on the new function of CDs on surfactant systems will come.

Metal mediated coordination polymers offer the opportunity to fabricate devices and materials that are equally important for fundamental research and new technologies. Most coordination polymers were synthesized at the desired stoichiometry. We demonstrate that coordination polyelectrolytes can form in layer-by-layer (LBL) assembled films regardless of the initial metal to bisligand ratio in solution. Upon dipping a substrate alternately into a covalent polylectrolyte solution and then into the mixed solution of Fe3+ and bisligands, the Fe3+ to ligand ratio in the LBL film tends to be 1:1 and forms polymeric structures even if the ratios in the bulk solution strongly deviate from unity. Our results suggest that layer-by-layer assembly promotes the formation of coordination polyelectrotyes.

In this paper, we report on the fluorescence enhancement of Eu coordination complexes in dilute solutions through electrostatic complex micelle formation with an oppositely charged block polyelectrolyte. The coordination complexes alone are oligomeric structures which have many ends where partially coordinated europium is exposed to water. In the presence of oppositely charged polyelectrolytes, the local concentration of the coordination complexes is greatly enhanced, so that they transform into polymeric structures and form electrostatically induced micelles with the block polyelectrolytes. This effectively decreases the number of europium–water coordination bonds, which leads to the enhancement of fluorescence emission. This is the first report that utilizes the concentration responsiveness of the smart coordination polymers to promote the function of the colloids made from them.

The effect of pH on iron-containing complex coacervate core micelles [Fe(III)–C3Ms] is investigated in this paper. The Fe(III)–C3Ms are formed by mixing cationic poly(N-methyl-2-vinylpyridinium iodide)-b-poly(ethylene oxide) [P2MVP41-b-PEO205] and anionic iron coordination polymers [Fe(III)–L2EO4] at stoichiometric charge ratio. Light scattering and Cryo-TEM have been performed to study the variations of hydrodynamic radius and core structure with changing pH. The hydrodynamic radius of Fe(III)–C3Ms is determined mainly by the corona and does not change very much in a broad pH range. However, Cryo-TEM pictures and magnetic relaxation measurements indicate that the structure of the micellar cores changes upon changing the pH, with a more crystalline, elongated shape and lower relaxivity at high pH. We attribute this to the formation of mixed iron complexes in the core, involving both the bis-ligand and hydroxide ions. These complexes are stabilized toward precipitation by the diblock copolymer.

Hierarchical assemblies of coordination supramolecules are reviewed. These assemblies are self-organized by coordination supramolecules themselves or co-assemblies with other modules. By utilizing electrostatic interaction, the coordination supramolecules can be incorporated into films, liquid crystals, micelles, and hydrogels, etc. These coordination supramolecules-containing novel materials exhibit many switchabilities and other desired properties. The following contents are covered in this review: (1) coordination supramolecules of different architecture; (2) hierarchical molecular devices containing these coordination supramolecules; (3) short perspectives and conclusions.

We report in this work on the scaling behavior of wormlike micelles formed in a series of mixed systems of oppositely charged surfactants, including sodium decanote (SD)/hexadecyltrimethylammonium bromide (CTAB), sodium laurate (SL)/hexadecyltrimethylammonium bromide, sodium didecaminocystine (SDDC)/hexadecyltrimethylammonium bromide, and sodium dilauraminocystine (SDLC)/hexadecyltrimethylammonium bromide. Steady and dynamic rheological measurements were performed to characterize these wormlike micelles. The scaling behavior for these systems at various mixing ratios was systematically investigated and was compared with that given by the Cates model. It was found that the Cates law can be applied in these systems simply by manipulating the mixing ratio or the surfactant structure. Energetic analysis demonstrates that the scaling behavior of wormlike micelles in nonequimolar mixed cationic and anionic surfactant systems can be close to that predicted by the Cates model, if the electrostatic contribution is below a threshold value.Scaling exponents for catanionic wormlike micelle systems can agree with values derived from the Cates model as the mixing ratio shifts toward electroneutral.

The self-assembly and molecular packing mode of a novel, unsymmetrical bolaamphiphile, sodium 4-(6-hydroxyhexyloxy) cinnamate (SHHC) was studied. Tube-like structures were obtained in SHHC aqueous solution at pH 9.2. Upon UV irradiation, the SHHC molecules in the system were found to undergo four-center-type photocyclodimerization and photoisomerization. The combination of IR, XRD and Zeta potential results suggested the formation of a tail-to-tail type bilayer membrane structure: the SHHC molecules stretched upright with the cinnamate headgroups toward the outside in each layer, whereas the tail OH groups of two layers remained inside and formed interlayer hydrogen bonds. This parallel packing mode of SHHC molecules in the membrane was also confirmed by the pH-induced self-assembly transition. With increasing pH from 9.2 to 12.0, the low-curvatured tubes transformed into spherical vesicles, which was in line with the increased outer leaflet head group area as increasing pH. Our results demonstrated that upon careful molecular design, the orientation of unsymmetrical bolaamphiphiles can be controlled; π–π interactions between cinnamoyl groups were found to be strong enough to drive the formation of well-oriented molecular assemblies.

Complex coacervate core micelles (C3Ms) from cationic poly(N-methyl-2-vinyl-pyridinium iodide)-b-poly(ethylene oxide) (P2MVP41-b-PEO205) and anionic iron coordination polymers are investigated in the present work. Micelle formation is studied by light scattering for both Fe(II)- and Fe(III)-containing C3Ms. At the stoichiometric charge ratio, both Fe(II)-C3Ms and Fe(III)-C3Ms are stable for at least 1 week at room temperature. Excess of iron coordination polymers has almost no effect on the formed Fe(II)-C3Ms and Fe(III)-C3Ms, whereas excess of P2MVP41-b-PEO205 copolymers in the solution can dissociate the formed micelles. Upon increasing salt concentration, the scattering intensity decreases. This decrease is due to both a decrease in the number of micelles (or an increase in CMC) and a decrease in aggregation number. The salt dependence of the CMC and the aggregation number is explained using a scaling argument for C3M formation. Compared with Fe(II)-C3Ms, Fe(III)-C3Ms have a lower CMC and a higher stability against dissociation by added salt.

We report that the phase and self-assembly transition in an aqueous surfactant two-phase (ASTP) system can be induced by a small amount of glycerol. The ASTP was formed from a cationic Gemini surfactant, C12C6C12(Et), and an anionic surfactant, sodium laureate (SL), in a borax solution. Upon addition of 0.3–2 vol% glycerol to the system, the ASTP system underwent a striking phase transition: three phases at 0.3–0.5% glycerol, a single birefringent phase at 0.7–1.2% glycerol, then again two phases, with the upper one like ice-cream. FF-TEM, CSLM and polarized microscopy revealed that the lamellae in the original upper phase were transformed into multilamellar vesicles. This phase and the microstructure transition were attributed to neutralization of sodium laureate to lauric acid by the formation of protons from the reaction of borax with glycerol. The variation of the charge density on the bilayer assemblies and the formation of LA were confirmed by fluorescence quenching and ATR-IR experiments. Our results demonstrate that a small amount of glycerol can be used to tailor the phases and microstructures in surfactant systems containing pH-sensitive components.

We investigated the formation of nanoribbon hydrogels in a mixed system of zinc ions, bis(ligand)s, and triblock peptide copolymers. Using a combination of experimental techniques: dynamic light scattering, cryo-transmission electron microscopy, small-angle X-ray scattering and circular dichroism, we arrived at a model for the formation of nanoribbon hydrogels in which well-defined nanoribbons are formed out of multiple supramolecular interactions: (1) metal coordination that yields supramolecular polyelectrolytes; (2) electrostatic complexation between the supramolecular polyelectrolytes and the oppositely charged blocks of the peptide copolymers; (3) hydrogen bond and (4) hydrophobic interactions that support the secondary and ternary structure of the ribbons; (5) van der Waals interactions that enable bundling of the ribbons.

We report on the stability of complex coacervate core micelles, i.e., C3Ms (or PIC, BIC micelles), containing metal coordination polymers. In aqueous solutions these micelles are formed between charged-neutral diblock copolymers and oppositely charged coordination polymers formed from metal ions and bisligand molecules. The influence of added salt, polymer concentration, and charge composition was investigated by using light scattering and cryo-TEM techniques. The scattering intensity decreases strongly with increasing salt concentration until a critical salt concentration beyond which no micelles exist. The critical micelle concentration increases almost exponentially with the salt concentration. From the scattering results it follows that the aggregation number decreases with the square root of the salt concentration, but the hydrodynamic radius remains constant or increases slightly. It was concluded that the density of the core decreases with increasing ionic strength. This is in agreement with theoretical predictions and is also confirmed by cryo-TEM measurements. A complete composition diagram was constructed based on the composition boundaries obtained from light scattering titrations.

Supramolecular self-assembly into various nano- or microscopic structures based on non-covalent interactions between molecules has been recognized as a very efficient approach that leads to functional materials. Since most non-covalent interactions are relatively weak and form and break without significant activation barriers, the thermodynamic equilibrium of many supramolecular systems can be easily influenced by processing pathways that allow the system to stay in a kinetically trapped state. Thus far, kinetic traps have been found to be very important in producing more elaborate structural and functional diversity of self-assembled systems. In this review, we try to summarize the approaches that can produce kinetically trapped self-assemblies based on examples made by us. We focus on the following subjects: (1) supramolecular pathway dependent self-assembly, including kinetically trapped self-assemblies facilitated by host–guest chemistry, coordination chemistry, and electrostatic interactions; (2) physical processing pathway dependent self-assembly, including solvent quality controlled self-assembly, evaporation induced self-assembly and crystallization induced self-assembly.

Fabrication of solid white luminescent materials is a challenging topic. In this work we report that upon combining the advantages of aggregation induced emission and reversible coordination polymers, solid white luminescent films with the CIE coordinates of (0.335, 0.347) and external quantum efficiencies of up to 11.74% can be achieved via layer-by-layer assembly. In particular, the ratio of the R(red) G(green) B(blue) elements can be rationally controlled via concentration, demonstrating the advantage of reversible coordination polymers in the fabrication of functional materials. The white emission of the solid thin film displays excellent stability against temperature, pH, and explosion materials, but exhibits specific detection for Cl2, suggesting its great potential for application as both a robust luminescent material and a chemical sensor.

CDs may have promising functions in surfactant systems far beyond simply being disadvantageous to the formation of micelles. In this paper we review the recent literature and our work on the interesting effect of CDs on amphiphilic systems, especially on the concentrated single surfactant systems and catanionic surfactant mixed systems, both of them have been scarcely focused upon in the literature. In concentrated single surfactant systems, the 2:1 surfactant–CD inclusion complexes may form hierarchical self-assemblies such as lamellae, microtubes, and vesicles which are driven by hydrogen bonding. In nonstoichiometrically mixed catanionic surfactant systems, CDs behave as a stoichiometry booster that always selectively binds to the excess component so as to shift the mixing ratio to electro-neutral in the aggregates. In this way, CDs reduce the electrorepulsion in the aggregates and trigger their growth. Upon analysis of literature work and our own results, we expect that a new era focusing on the new function of CDs on surfactant systems will come.

In this paper, we report on the impact of the structure of ligands on the luminescence enhancement of Eu(III) by directly exciting Eu(III) with visible light in aqueous media. Upon replacing the water molecules that coordinated around a Eu3+ ion with a ditopic ligand 1,11-bis(2,6-dicarboxypyridin-4-yloxy)-3,6,9-trioxaundecane (L2EO4) or ethylenediaminetetraacetic acid disodium salt (EDTA), significant luminescence can be obtained. L2EO4 may occupy all 9 coordinating sites of a Eu3+ ion at proper L2EO4/Eu ratios, whereas EDTA only occupies 6 of them with 3 sites left for water at various EDTA/Eu ratios. These coordinated water molecules quench the fluorescence of EDTA–Eu complexes drastically so that the luminescence is about 30 times lower than that of the L2EO4–Eu system. Furthermore, the negatively charged L2EO4/Eu = 3/2 coordinated complex can be further transformed into coordination ‘polymers’ by mixing with a positively charged block polyelectrolyte, which forms electrostatic micelles with further enhanced luminescence. The emission of the EDTA–Eu complex is not influenced by the addition of polymers due to the formation of stable small 1:1 EDTA–Eu complex which doesn't change with increasing concentration. Our work points out that the L2EO4–Eu system is superior to the EDTA–Eu system in creating visible light sensitized Eu(III) luminescence, and the emission of Eu(III) can be indeed significantly enhanced to an applicable level by excluding all the water molecules in the coordination sphere of Eu(III).

Currently there is intense interest in decreasing the operating potential for hydrogen evolution in water electrolysis to considerably decrease the energy cost. In this work we report a significant decrease of the operating potential for hydrogen evolution from neutral water mediated by an iron based soft coordination polymer (FeIII-SCSP). The creation of a local acidic environment with a thickness in the range of ∼40 nm on the surface of a glassy carbon electrode allows enrichment of H+ on the GCE, so that the operating potentials were effectively decreased. This strategy thus generates a new paradigm for lowering the operating potential of hydrogen generation from neutral water without the use of additional acids and organic cosolvents.

This article presents a facile strategy to combine Eu3+ and Gd3+ ions into coacervate core micelles in a controlled way with a statistical distribution of the ions. Consequently, the formed micelles show a high tunability between luminescence and relaxivity. These highly stable micelles present great potential for new materials, e.g. as bimodal imaging probes.

Binding of metal ions to the head of a coordinating amphiphile TTC4L substantially changes the emission color of the terthiophene group attached to the chain end via a conformation triggered self-assembly. This is in analogy with the allostery of proteins in which binding a ligand to one site may affect its performance at another site through conformational change.