ABSTRACT
The nanocrystallization of functional molecules has been a subject of recent interest in the current development of nanotechnology. Herein, we report the unprecedented synthesis of single nanocrystals of a molecular gold nanocluster in a homogeneous solution by using surfactant-based nano-envelopes. The co-assembling of a Au8 nanocluster carrying lipophilic phosphine ligands with sodium dodecyl sulfate (SDS) in an aqueous solution results in the formation of sphere-shaped amorphous nano-aggregates coated with the surfactant. Upon sonication, the spherical amorphous aggregates are smoothly shape-shifted into discrete rhombic nanocrystals, which can be tracked by TEM and solution XRD. The transformation into single nanocrystals occurs exclusively without further growth or agglomeration, implying that the crystal growth is restricted within the surfactant nano-envelopes. The robust but flexible nature of the wrapped surfactant is likely responsible for the controlled crystallization. We also demonstrate that the amorphous-to-nanocrystalline transition in solution remarkably enhances the photoluminescence emission from the nanocluster, providing a clear example of crystallization-induced emission enhancement. Notably, the obtained nanocrystals showed high stability in solution and retained their shape, size, and PL intensity even after several months, owing to the densely packed surfactant shell. The present surfactant-directed nanocrystallization method may be applicable to other molecular species to contribute to the development of nanocluster science as well as the designed synthesis of nanomaterials.
ABSTRACT
Ultrathin flexible photodetectors can be conformably integrated with the human body, offering promising advancements for emerging skin-interfaced sensors. However, the susceptibility to degradation in ambient and particularly in aqueous environments hinders their practical application. Here, we report a 3.2-micrometer-thick water-resistant organic photodetector capable of reliably monitoring vital sign while submerged underwater. Embedding the organic photoactive layer in an adhesive elastomer matrix induces multidimensional hybrid phase separation, enabling high adhesiveness of the photoactive layer on both the top and bottom surfaces with maintained charge transport. This improves the water-immersion stability of the photoactive layer and ensures the robust sealing of interfaces within the device, notably suppressing fluid ingression in aqueous environments. Consequently, our fabricated ultrathin organic photodetector demonstrates stability in deionized water or cell nutrient media over extended periods, high detectivity, and resilience to cyclic mechanical deformation. We also showcase its potential for vital sign monitoring while submerged underwater.
ABSTRACT
Unlike absorption-based colors of dyes and pigments, reflection-based colors of photonic crystals, so called "structural colors", are responsive to external stimuli, but can remain unfaded for over ten million years, and therefore regarded as a next-generation coloring mechanism. However, it is a challenge to rationally design the spectra of structural colors, where one structure gives only one reflection peak defined by Bragg's law, unlike those of absorption-based colors. Here, we report a reconfigurable photonic crystal that exhibits single-peak and double-peak structural colors. This photonic crystal is composed of a colloidal nanosheet in water, which spontaneously adopts a layered structure with single periodicity (407â nm). After a temperature-gradient treatment, the photonic crystal segregates into two regions with shrunken (385â nm) and expanded (448â nm) periodicities, and thus exhibits double reflection peaks that are blue- and red-shifted from the original one, respectively. Notably, the transition between the single-peak and double-peak states is reversible.
ABSTRACT
Although phage display selection using a library of M13 bacteriophage has become a powerful tool for finding peptides that bind to target materials on demand, a remaining concern of this method is the interference by the M13 main body, which is a huge filament >103 â times larger than the displayed peptide, and therefore would nonspecifically adhere to the target or sterically inhibit the binding of the displayed peptide. Meanwhile, filamentous phages are known to be orientable by an external magnetic field. If M13 filaments are magnetically oriented during the library selection, their angular arrangement relative to the target surface would be changed, being expected to control the interference by the M13 main body. This study reports that the magnetic orientation of M13 filaments vertical to the target surface significantly affects the selection. When the target surface was affinitive to the M13 main body, this orientation notably suppressed the nonspecific adhesion. Furthermore, when the target surface was less affinitive to the M13 main body and intrinsically free from the nonspecific adhesion, this orientation drastically changed the population of M13 clones obtained through library selection. The method of using no chemicals but only a physical stimulus is simple, clean, and expected to expand the scope of phage display selection.
Subject(s)
Cell Surface Display Techniques , Peptide Library , Peptides/metabolism , Bacteriophage M13/genetics , Bacteriophage M13/metabolism , Magnetic PhenomenaABSTRACT
Mechanical nonreciprocity, or the asymmetric transmission of mechanical quantities between two points in space, is crucial for developing systems that can guide, damp, and control mechanical energy. We report a uniform composite hydrogel that displays substantial mechanical nonreciprocity, owing to direction-dependent buckling of embedded nanofillers. This material exhibits an elastic modulus more than 60 times higher when sheared in one direction compared with the opposite direction. Consequently, it can transform symmetric vibrations into asymmetric ones that are applicable for mass transport and energy harvest. Furthermore, it exhibits an asymmetric deformation when subjected to local interactions, which can induce directional motion of various objects, including macroscopic objects and even small living creatures. This material could promote the development of nonreciprocal systems for practical applications such as energy conversion and biological manipulation.
ABSTRACT
The photocyclodimerization of 2-anthracenecarboxylic acid has been extensively studied as a model reaction of asymmetric photochemistry. So far, numerous chiral environments have been employed to control this photoreaction, while the scope of photoreactants has been limited only to 2-anthracenecarboxylic acid and its simple esters and amides. Here, we developed a systematic series of photoreactants (2 a-d) by introducing various substituents to 2-anthracenecarboxylic acid, which showed different reactivities and selectivities depending on the substituents. By using the photoreactants 2 a-d, we evaluated the performance of a chiral environment composed of an amphiphilic amino alcohol (1), where the photocyclodimerization of 2 a-d generally proceeded in excellent regio- and enantioselectivities (71-98 % regio ratio, 76-86 % ee). Furthermore, by reacting 2 a and 2 b together in the chiral environment of 1, we succeeded in the first stereocontrolled cross-photocyclodimerization between two prochiral anthracenes (58 % chemo ratio, 83 % regio ratio, 90 % ee).
Subject(s)
Amino Alcohols , Anthracenes , Stereoisomerism , Dimerization , Cyclization , Anthracenes/chemistryABSTRACT
Chiral amphiphiles are useful for controlling the structures and properties of supramolecular assemblies, but their stereocontrolled synthesis is generally difficult, because their long alkyl chains tend to bring unfavorable effects on the solubility, reactivity, and crystallinity of molecules. Typical examples are amphiphilic 1,2-amino alcohols (S)-1 and (1S,2S)-2 developed by our group, which were known to serve as chiral reaction media for controlling the stereochemistry of asymmetric photoreactions. We previously developed synthetic schemes for these 1,2-amino alcohols, but their synthetic efficiencies were unsatisfactory (13 steps with 2% overall yield for (S)-1; eight steps with 8% yield for (1S,2S)-2). As the main reason of such low efficiencies, the stereocontrolling methods we previously employed (diastereomer-salt crystallization for (S)-1; stereoselective reactions for (1S,2S)-2) were not ideal. Here, we report highly improved synthetic schemes for (S)-1 and (1S,2S)-2 based on the enantioselective high performance liquid chromatography (HPLC) separation of intermediates in preparative scales. Compared with the previous schemes, the new schemes are advantageous in fewer number of steps, higher overall yield, and lower risk of racemization (seven steps with 15% overall yield for (S)-1; seven steps with 26% overall yield for (1S,2S)-2).
Subject(s)
Amino Alcohols , Amino Alcohols/chemistry , Chromatography, High Pressure Liquid/methods , StereoisomerismABSTRACT
Just like in living organisms, if precise coherent operation of tiny movable components is possible, one may generate a macroscopic mechanical motion. Here we report that ~1010 pieces of colloidally dispersed nanosheets in aqueous media can be made to operate coherently to generate a propagating macroscopic wave under a non-equilibrium state. The nanosheets are initially forced to adopt a monodomain cofacial geometry with a large and uniform plane-to-plane distance of ~420 nm, where they are strongly correlated by competitive electrostatic repulsion and van der Waals attraction. When the electrostatic repulsion is progressively attenuated by the addition of ionic species, the nanosheets sequentially undergo coherent motions, generating a propagating wave. This elaborate wave in time and space can transport microparticles over a long distance in uniform direction and velocity. The present discovery may provide a general principle for the design of macroscopically movable devices from huge numbers of tiny components.
ABSTRACT
Ultralong organic phosphorescence (UOP) has aroused enormous interest in recent years. UOP materials are mainly limited to crystals or rigid host-guest systems. Their poor processability and mechanical properties critically hamper practical applications. Here, we reported a series of ultralong phosphorescent foams with high mechanical strength. Phosphorescence lifetime of the foam can reach up to 485.8 ms at room temperature. Impressively, lightweight gelatin foam can bear a compressive pressure of 4.44 MPa. Moreover, phosphorescence emission of polymer foam can be tuned from blue to orange through varying the excitation wavelength. Experimental data and theoretical calculations revealed that ultralong phosphorescence was ascribed to the fixation of multiple hydrogen bonds to the clusters of carbonyl groups. These results will allow for expanding the scope of luminescent foams, providing an ideal platform for developing ultralong phosphorescent materials with high mechanical strength.
ABSTRACT
PbS square superstructures are formed by the oriented assembly of PbS quantum dots (QDs), reflecting the facet structures of each QD. In the square assembly, the quantum dots are highly oriented, in sharp contrast to the conventional hexagonal QD assemblies, in which the orientation of QDs is highly disordered, and each QD is connected through ligand molecules. Here, we measured the transport properties of the oriented assembly of PbS square superstructures. The combined electrochemical doping studies by electric double layer transistor (EDLT) and spectroelectrochemistry showed that more than fourteen electrons per quantum dot are introduced. Furthermore, we proved that the lowest conduction band is formed by the quasi-fourth degenerate quantized (1Se) level in the PbS QD square superstructures.
ABSTRACT
A Cu-catalyzed cascade reaction between N-alkoxyanilines having an electron-donating functional group at the ortho position and dienophiles, such as N-methylmaleimide, styrene, and indene, proceeded via a dearomative [1,3]-alkoxy rearrangement followed by the Diels-Alder reaction, affording the corresponding ketimines with highly functionalized bicyclic skeletons in an efficient and stereoselective manner. Our mechanistic investigations indicated that the [1,3]-rearrangement is the rate-determining process, efficiently suppressing unfavorable side reactions.
ABSTRACT
Based on the predesigned self-selective complexation, metallo-supramolecular P3HT-b-PEO diblock copolymers with varying block ratios were synthesized, and their oriented polymer films generated during solvent evaporation in a 9 T magnetic field were investigated. An anisotropic, ordered layer structure was achieved using [P3HT20 -Zn-PEO107 ] and carefully characterized by polarized optical microscopy (POM), AFM, polarized UV/Vis spectroscopy, and GI-SAXS/WAXS. The PEO-removed [P3HT20 -Zn-PEO107 ] film was obtained after decomplexation with TEA-EDTA under mild conditions, and the selective removal of PEO domains was evidenced by UV/Vis and ATR-FTIR spectroscopy. Anisotropic photoconductivity of the magnetically aligned film was evaluated by flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements. The results indicated that the presence of insulating crystalline PEO segments diminished the photoconductivity along the P3HT backbone direction.
ABSTRACT
The longest bottlebrush polymers reported so far (up to 7â µm in length) were synthesized in two steps from a norbornene derivative bearing two 2-bromoisobutylate moieties (NB). The key to this achievement is the excellent reactivity of NB in ring opening metathesis polymerization, which proceeded in a well-controlled manner with quantitative conversion of NB for monomer-initiator ratios ranging up to 10,000. The resultant polymer derived from NB was readily converted to various bottlebrush polymers in a divergent synthetic route by grafting vinyl monomers from the 2-bromoisobutylate units in NB via atom transfer radical polymerization. The structure of the ultra-long bottlebrush polymer was directly observed using atomic force microscopy.
ABSTRACT
Although various biomimetic soft materials that display structural hierarchies and stimuli responsiveness have been developed from organic materials, the creation of their counterparts consisting entirely of inorganic materials presents an attractive challenge, as the properties of such materials generally differ from those of living organisms. Here, we have developed a hydrogel consisting of inorganic nanosheets (14 wt%) and water (86 wt%) that undergoes thermally induced reversible and abrupt changes in its internal structure and mechanical elasticity (23-fold). At room temperature, the nanosheets in water electrostatically repel one another and self-assemble into a long-periodic lamellar architecture with mutually restricted mobility, forming a physical hydrogel. Upon heating above 55 °C, the electrostatic repulsion is overcome by competing van der Waals attraction, and the nanosheets rearrange into an interconnected 3D network of another hydrogel. By doping the gel with a photothermal-conversion agent, the gel-to-gel transition becomes operable spatiotemporally on photoirradiation.
ABSTRACT
Ionic liquid crystals have emerged as a new class of functional soft materials in the last two decades, and they exhibit synergistic characteristics of ionic liquids and liquid crystals such as macroscopic orientability, miscibility with various species, phase stability, nanostructural tunability, and polar nanochannel formation. Owing to these characteristics, the structures, properties, and functions of ionic liquid crystals have been a hot topic in materials chemistry, finding various applications including host frameworks for guest binding, separation membranes, ion-/proton-conducting membranes, reaction media, and optoelectronic materials. Although several excellent review articles of ionic liquid crystals have been published recently, they mainly focused on the fundamental aspects, structures, and specific properties of ionic liquid crystals, while these applications of ionic liquid crystals have not yet been discussed at one time. The aim of this feature article is to provide an overview of the applications of ionic liquid crystals in a comprehensive manner.
ABSTRACT
Herein we report the synthesis and isolation of a shape-persistent Janus protein nanoparticle derived from the biomolecular machine chaperonin GroEL (AGroELB) and its application to DNA-mediated ternary supramolecular copolymerization. To synthesize AGroELB with two different DNA strands A and B at its opposite apical domains, we utilized the unique biological property of GroEL, i.e., Mg2+/ATP-mediated ring exchange between AGroELA and BGroELB with their hollow cylindrical double-decker architectures. This exchange event was reported more than 24 years ago but has never been utilized for molecular engineering of GroEL. We leveraged DNA nanotechnology to purely isolate Janus AGroELB and succeeded in its precision ternary supramolecular copolymerization with two DNA comonomers, A** and B*, that are partially complementary to A and B in AGroELB, respectively, and programmed to self-dimerize on the other side. Transmission electron microscopy allowed us to confirm the formation of the expected dual-periodic copolymer sequence -(B*/BGroELA/A**/A**/AGroELB/B*)- in the form of a laterally connected lamellar assembly rather than a single-chain copolymer.
ABSTRACT
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
ABSTRACT
Since various helical supramolecular polymers became available, their application to molecular chirality recognition have been anticipated but not extensively studied. So far, only a few examples of chiral reactions have been reported, but none for chiral separation. Here, we report the application of a helical supramolecular polymer to the enantio-separation of chiral guest molecules. The monomer of this supramolecular polymer is the salt-pair of a dendritic carboxylic acid with an enantiopure amino alcohol. In an apolar solvent, this salt-pair stacks via hydrogen bonds to form a helical polymer. In conjunction with this carboxylic acid, various amino alcohols afford supramolecular polymers, whose helical handedness is determined by the stereochemistry of the amino alcohols. When two salts with the same chirality are mixed, they undergo copolymerization, while those with opposite chirality do not. Owing to this stereoselective copolymerizability, the helical supramolecular polymer could bias the enantiomeric composition of chiral amino alcohols.
ABSTRACT
meta-Substituted anilines were efficiently synthesized via copper-catalyzed [1,3]-methoxy rearrangement of N-methoxyanilines followed by Michael addition of nucleophiles to the in situ generated ortho-quinol imine. The present reaction exhibits excellent applicability of para-substituents, such as vinyl, methylthio, ester, and bromo, and carbon nucleophiles, such as 1,3,5-trimethoxybenzene, N-methylindole, and dimethyl malonate. Thus, the present rearrangement can resolve problems stemming from oxidation reactions, such as the use of stoichiometric amounts of oxidants and low compatibility of electron-withdrawing groups.
ABSTRACT
Biological materials, such as bones, teeth and mollusc shells, are well known for their excellent strength, modulus and toughness1-3. Such properties are attributed to the elaborate layered microstructure of inorganic reinforcing nanofillers, especially two-dimensional nanosheets or nanoplatelets, within a ductile organic matrix4-6. Inspired by these biological structures, several assembly strategies-including layer-by-layer4,7,8, casting9,10, vacuum filtration11-13 and use of magnetic fields14,15-have been used to develop layered nanocomposites. However, how to produce ultrastrong layered nanocomposites in a universal, viable and scalable manner remains an open issue. Here we present a strategy to produce nanocomposites with highly ordered layered structures using shear-flow-induced alignment of two-dimensional nanosheets at an immiscible hydrogel/oil interface. For example, nanocomposites based on nanosheets of graphene oxide and clay exhibit a tensile strength of up to 1,215 ± 80 megapascals and a Young's modulus of 198.8 ± 6.5 gigapascals, which are 9.0 and 2.8 times higher, respectively, than those of natural nacre (mother of pearl). When nanosheets of clay are used, the toughness of the resulting nanocomposite can reach 36.7 ± 3.0 megajoules per cubic metre, which is 20.4 times higher than that of natural nacre; meanwhile, the tensile strength is 1,195 ± 60 megapascals. Quantitative analysis indicates that the well aligned nanosheets form a critical interphase, and this results in the observed mechanical properties. We consider that our strategy, which could be readily extended to align a variety of two-dimensional nanofillers, could be applied to a wide range of structural composites and lead to the development of high-performance composites.