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Applying magnetic substrates, magnetized perpendicular to the surface, we were able to crystallize from racemic solution pure conglomerates of several molecules. The resolution is based on the spin...

Enormous attention has been paid to upconverted circularly polarized luminescence (UC-CPL). However, so far, chiral species are still needed in UC-CPL materials, either through the covalent or noncovalent bond. Here, we report a general supramolecular coassembly approach for the fabrication of UC-CPL systems from completely achiral components. We have found that an achiral C3-symmetric molecule could form a chiral nanohelix through symmetry breaking, which could serve as a general helical platform to endow achiral guests with induced chirality and CPL activity. Two different photon upconversion systems, namely, triplet-triplet annihilation photon upconversion (TTA-UC) donor/acceptor pairs and inorganic lanthanide upconversion nanoparticles (UCNPs), are selected. When these two systems coassembled with the chiral nanohelix made from an achiral C3-symmetric molecule, hybrid nanohelix structures formed and UC-CPL activity was induced. Through such an approach, we demonstrated that the fabrication of the UC-CPL materials does not require any chiral molecules. Moreover, we have shown that the polarization of UC-CPL can be tuned by the helicity of the nanohelix, which could be controlled through the seeded vortex. Our work provides a general approach for designing tunable UC-CPL materials from completely achiral motifs, which largely expands the research scope of the CPL materials.

Consecutive boosted circularly polarized luminescence (CPL) with controlled handedness has been demonstrated in a supramolecular assembly from a completely achiral molecule. It is found that achira...

The steady-state charge and spin transfer yields were measured for three different Ru-modified azurin derivatives in protein films on silver electrodes. While the charge-transfer yields exhibit weak temperature dependences, consistent with operation of a near activation-less mechanism, the spin selectivity of the electron transfer improves as temperature increases. This enhancement of spin selectivity with temperature is explained by a vibrationally induced spin exchange interaction between the Cu(II) and its chiral ligands. These results indicate that distinct mechanisms control charge and spin transfer within proteins. As with electron charge transfer, proteins deliver polarized electron spins with a yield that depends on the protein’s structure. This finding suggests a new role for protein structure in biochemical redox processes.

Achieving a higher dissymmetry factor is a crucial issue in developing circularly polarized luminescence (CPL) materials. Here, by tailoring the solvent composition and the morphology of the same chiral emissive small molecules (R- or S-SPAn), circularly polarized emission with a boosted dissymmetry factor (two orders) was realized. It was found that by regulating the water fraction in the mixed THF/H2O, we were able to achieve kinetic control over association of chiral emissive R- or S-SPAn into various nanostructures with 0D nanospheres, 2D nanoflakes and 3D stacked nanoflakes. These nanostructures are all CPL active. Remarkably, the dissymmetry factors of the nanostructures were significantly enhanced compared to those of the molecules and further boosted in different morphologies, from ∼10−4 (0D nanospheres) to 10−3 (2D flake) to ∼10−2 (3D nanoflakes). The enlarged glum value could be assigned to a good packing induced strong luminescence of an excimer. This strategy provides an efficient way to fabricate higher dissymmetry factor CPL organic nanomaterials by only changing the supramolecular architectures while using the same chiral small molecules.

Enantiomeric diaminocyclohexane was found to trigger the self-assembly of achiral monomers into chiral supramolecular assemblies with strong circularly polarized luminescence.

The origin of homochirality in life is a fundamental mystery. Symmetry breaking and subsequent amplification of chiral bias are regarded as one of the underlying mechanisms. However, the selection and control of initial chiral bias in a spontaneous mirror symmetry breaking process remains a great challenge. Here we show experimental evidences that laminar chiral microvortices generated within asymmetric microchambers can lead to a hydrodynamic selection of initial chiral bias of supramolecular systems composed of exclusively achiral molecules within milliseconds. The self-assembled nuclei with the chirality sign affected by the shear force of enantiomorphic microvortices are subsequently amplified into almost absolutely chirality-controlled supramolecular gels or nanotubes. In contrast, turbulent vortices in stirring cuvettes fail to select the chirality of supramolecular gels. This study reveals that a laminar chiral microflow can induce enantioselection far from equilibrium, and provides an insight on the origin of natural homochirality., Symmetry breaking and chiral amplification are fundamental principles in chemistry and biology but the control of initial chiral bias remains a great challenge. Here the authors show that chiral microvortices can lead to a selection of initial chiral bias of supramolecular systems composed of achiral molecules.

An achiralC3-symmetric molecule was found to self-assemble into various hierarchical nanostructures such as nanotwists, nanotrumpets and nanobelts, in which the twisted fibers showed supramolecular chirality as well as circularly polarized luminescence although the compound is achiral.

The fabrication and application of supramolecular gels have achieved great progress in the past few decades. Although several reviews and books have well summarized the design, properties and functions of certain supramolecular gels, a comprehensive overview is still lacking to reveal the design strategy of the supramolecular gels. In this review, we propose a concept of a supramolecular gelaton, which is a structural unit or molecule for the design and construction of the supramolecular gels, to show how to design the targeted functional gels. We classify the gelaton into two types. One is a covalent gelaton that when covalently connects with other functional groups results in a molecule that can become a gelator. The other type is a non-covalent gelaton, which is a gelator molecule that can assist other gelator or non-gelator molecules to form gels. We hope that the concept of supramolecular gelatons will provide useful guidance and understanding of the design of gelator molecules and preparation of supramolecular gels.

Colloidal nanocrystal assemblies (CNAs) of cuprous oxide (Cu2O) are controllably synthesized by in-situ self-assembling primary Cu2O nanocrystals, in which Cu2O CNAs assemblied by nanocrystals of 8–10 nm were about 0.6 μm and Cu2O CNAs assemblied by nanocrystals of 32 nm were about 1.8 μm. From room temperature magnetization measurement results, both of the CNAs showed ferromagnetic behavior with very small saturation magnetization (Ms) values and 10 nm nanocrystal-based CNAs had the largest Ms value of about 9.2 emu/g. Electrochemical experimental results showed that submicron Cu2O CNAs were able to detect dopamine and uric acid quickly while micrometer Cu2O CNAs were not. Cu2O CNAs formed by 8 nm nanocrystals showed the highest electrocatalytic activity in oxygen reduction reaction and displayed the best adsorptive ability to remove Congo red in aqueous solutions, which can be recylced after a simple heat treatment. Furthermore, the formation mechanism and the relationship between crystalline size and assembly of primary nanocrystals as well as physicochemical properties of Cu2O CNAs have been discussed and analyzed.

Two types of PdCu2 nanoparticles were prepared through one-pot synthesis and a two-step reducing process, named as PdCu2-1 and PdCu2-2, respectively. The morphology and structure of as-prepared samples were investigated by transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and inductively coupled plasma-optical emission spectrometry. Results showed that more Pd atoms were buried in the inside of PdCu2-1, whereas more available Pd sites were distributed on the surface of PdCu2-2. The electrochemical measurements indicated that both PdCu2-1 and PdCu2-2 nanoparticles showed a higher electrocatalytic activity than that for pure Pd nanoparticles. In particular, PdCu2-2 predictably exhibited a better stability and durability as well as a lower onset potential and a higher catalytic current density than that of PdCu2-1 toward ethanol oxidation in alkaline media. On the basis of these studies, the formation mechanisms of both th...

This paper studies the electrochemical behaviors of symmetric supercapacitors with the porous carbon obtained from chestnut shells as active materials and ionic liquids as electrolytes, including 1-ethyl-3-methylimidazolium bis[(trifluoromethyl) sulfonyl]imide (EMImTF 2 N), 1-ethyl-3-methylimidazolium tetrafluoroborate (EMImBF 4 ) and 1-Butyl-3-methylimidazolium tetrafluoroborate (BMImBF 4 ). Experimental data observed at a current density of 0.1 A/g showed that symmetric supercapacitor using EMImBF 4 as the electrolyte had the maximum specific capacitance of 208.7 F/g, while 180.8 F/g for EMImTF 2 N and 134.6 F/g for BMImBF 4 . However, specific capacitance of supercapacitors assembled with EMImBF 4 , EMImTF 2 N and BMImBF 4 respectively retained 62.9%, 94.5% and 71.5% of the initial values after 2000 galvanostatic charge-discharge cycles. The relationship between the molecular structure of ionic liquids and electrochemical properties of the supercapacitors was discussed based on the experimental data.

Functionalization of carbon nanotubes (CNTs) has been proven to be an effective method to modulate their properties including electrocatalytic activity. Here, we report the catalytic properties of CNTs modified with various functional groups in the oxygen reduction reaction (ORR). Experimental data show that ORR activity of CNTs is enhanced markedly with increasing content of carboxyl groups, and MWNT-COOH sample display the highest current density and most positive onset potential among the studied catalysts. Remarkably, the functionalized CNTs exhibit excellent long-time stability and tolerance towards alcohols. Both experimental and theoretical results suggest that the deprotonated state of carboxyl groups promote the ORR electrocatalytic performance of CNTs in an alkaline electrolyte.

The electrochemical reduction behavior of nitrobenzene was studied on glassy carbon electrodes modified with MnFe 2 O 4 colloid nanocrystal assemblies. The crystalline size and structure of the colloid nanocrystal assemblies were found to play important roles in determining the catalytic activity of the electrode towards nitrobenzene. It was found that nitrobenzene was first reduced to phenylhydroxylamine via a four-electron reduction pathway, then phenylhydroxylamine was oxidized to nitrosobenzene by losing two-electron on the electrode. The electrochemical reaction mechanisms of p -nitrotoluene and m -dinitrobenzen on the electrodes were discussed and analyzed based on the experimental data.

The origin of biological homochirality, e.g., life selects the L-amino acids and D-sugar as molecular component, still remains a big mystery. It is suggested that mirror symmetry breaking plays an important role. Recent researches show that symmetry breaking can also occur at a supramolecular level, where the non-covalent bond was crucial. In these systems, equal or unequal amount of the enantiomeric nanoassemblies could be formed from achiral molecules. In this paper, we presented a brief overview regarding the symmetry breaking from dispersed system to gels, solids, and at interfaces. Then we discuss the rational manipulation of supramolecular chirality on how to induce and control the homochirality in the self-assembly system. Those physical control methods, such as Viedma ripening, hydrodynamic macro- and micro-vortex, superchiral light, and the combination of these technologies, are specifically discussed. It is hoped that the symmetry breaking at a supramolecular level could provide useful insights into the understanding of natural homochirality and further designing as well as controlling of functional chiral materials.

Stable luminescent π-radicals with doublet emission have attracted growing attention for functional molecular materials. However, their chiroptical properties, particularly their doublet emission-based circularly polarized luminescence, have never been investigated. Here, we investigate the circularly polarized luminescence (CPL) properties of a series of achiral luminescent open-shell π-radicals through various chirality regulation approaches, including induction by a magnetic field, supramolecular coassembly and chiral liquid crystal encapsulation.

In this work, lanthanide-doped upconversion nanoparticles (UCNPs) showing upconverted circularly polarized luminescence were demonstrated in an organic–inorganic co-assembled system. Achiral UCNPs (NaYF4:Yb/Er or NaYF4:Yb/Tm) can be encapsulated into chiral helical nanotubes through the procedure of co-gelation. These co-gel systems display intense upconverted circularly polarized luminescence (UC-CPL) ranging from ultraviolet (UV, 300 nm) to near-infrared (NIR, 850 nm) wavelength. In addition, the UV part of UC-CPL can be used to initiate the enantioselective polymerization of diacetylene.

Currently, the development of circularly polarized luminescent (CPL) materials has drawn extensive attention due to the numerous potential applications in optical data storage, displays, backlights in 3D displays, and so on. While the fabrication of CPL-active materials generally requires chiral luminescent molecules, the introduction of the "self-assembly" concept offers a new perspective in obtaining the CPL-active materials. Following this approach, various self-assembled materials, including organic-, inorganic-, and hybrid systems can be endowed with CPL properties. Benefiting from the advantages of self-assembly, not only chiral molecules, but also achiral species, as well as inorganic nanoparticles have potential to be self-assembled into chiral nanoassemblies showing CPL activity. In addition, the dissymmetry factor, an important parameter of CPL materials, can be enhanced through various pathways of self-assembly. Here, the present status and progress of self-assembled nanomaterials with CPL activity are reviewed. An overview of the key factors in regulating chiral emission materials at the supramolecular level will largely boost their application in multidisciplinary fields.

By constructing a supramolecular light-harvesting chiral nanotube in the aqueous phase, we demonstrate a cooperative energy and chirality transfer. It was found that a cyanostilbene-appended glutamate compound (CG) self-assembled into helical nanotubes exhibiting both supramolecular chirality and circularly polarized luminescence (CPL). When two achiral acceptors, ThT and AO, with different energy bands were co-assembled with the nanotube, the CG nanotube could transfer its chirality to both of the acceptors. The excitation energy could be transferred to ThT but only be sequentially transferred to AO. During this process, the CPL ascribed to the acceptor could be sequentially amplified. This work provides a new insight into the understanding the cooperative chirality and energy transfer in a chiral supramolecular system, which is similar to the natural light-harvesting antennas.

Palladium nanoparticle aggregates (Pd-NPAs) with various sizes were prepared by regulating the stability of Pd colloids. Structures of Pd-NPAs and their performances for electrooxidation of ethanol were investigated using power X-ray diffraction, transmission electron microscopy and electrochemical measurements. Experimental data illustrated that the size of Pd-NPAs, the concentration of electrolyte and the process of electrocatalysis jointly affected their electrocatalytic properties. The on-set potentials were negative-shifted during the electrocatalysis of ethanol as the concentration of KOH in the electrolytes continuously increased, while the catalytic current density reached the highest value in 2 M KOH electrolyte. The change of on-set potential, peak potential and peak current of Pd-NPAs during the electrooxidation of ethanol were systematically investigated and analyzed. A "size-electrolyte-process" mechanism was proposed to explain the variation of the electrocatalytic activity promoting in alkane media.