Search

Knot-like structures were found to have interesting magnetic properties in condensed matter physics. Herein, we report on topologically chiral molecular knots as efficient spintronic chiral material. The discovery of the chiral-induced spin selectivity (CISS) effect opens the possibility of manipulating the spin orientation with soft materials at room temperature and eliminating the need for a ferromagnetic electrode. In the chiral molecular trefoil knot, there are no stereogenic carbon atoms, and chirality results from the spatial arrangements of crossings in the trefoil knot structures. The molecules show a very high spin polarization of nearly 90%, a conductivity that is higher by about 2 orders of magnitude compared with that of other chiral small molecules, and enhanced thermal stability. A plausible explanation for these special properties is provided, combined with model calculations, that supports the role of electron–electron interaction in these systems.

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.

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-dependent charge reorganization (SDCR) effect. By having two surfaces with opposite magnetization, it was possible to simultaneously crystallize on each surface a different enantiomer. The method does not require any seeding or chemical modification and is generally employable to any conglomerate. A system is presented for performing the separation, while the racemic mixture flows between the two magnetic surfaces.

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.

Consecutively boosted circularly polarized luminescence (CPL) with controlled handedness has been demonstrated in a supramolecular assembly from a completely achiral molecule. It is found that achiral C3symmetric molecules exhibit strong supramolecular chirality as well as CPL through a vortex-accompanied assembly method. Surprisingly, the remarkable chiroptical property and the excited energy of the achiral molecules can be further transferred to another achiral dye, resulting in an amplified CPL with a dissymmetry factor over 0.1. This work not only provides a scenario for realizing the emergence, amplification, and transfer of CPL in the supramolecular system from achiral molecules, but also paves an easy yet efficient way to construct a strong and tunable circularly polarized emission based on the coupling with achiral fluorophores.

Arrays of nanoparticle (NP) clusters with controlled architectures show broad applications in nanolasers, sensors, and photocatalysis, but the fabrication of these arrays on substrates remains a grand challenge. This review presents a highly effective polymer-based strategy for the process-directed self-assembly of binary polyelectrolyte-grafted NPs (PGNPs) bearing opposite charges into stable colloidal molecules (CMs) on substrates via electrostatic interactions. The coordination number (x) of ABxCMs can be tuned by adjusting the pH or ionic strength of the solution or by employing different combinations of PGNPs with varying charge densities. Large-area CMs with diverse structures ranging from AB to AB7can be constructed on substrates in high yields. This approach is applicable to PGNPs with different cores of NPs. This assembly strategy offers a useful tool for the fabrication of structurally precise assemblies on substrates with broad applications.

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.

Two types of PdCu2nanoparticles 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 the PdCu2catalysts and the relationship between their structure and properties were discussed in this paper.

Research on chiral selection and recognition not only is of fundamental importance in resolving the origin of biological homochirality, but also is instructive in the fabrication of controlled molecular organization in supramolecular systems to modulate their chirality-related functional properties. Here we report an enantioselective assembly process between a chiral energy donor and two enantiomeric energy acceptors, which further results in chirality-controlled energy transfer and enantioselective triplet–triplet annihilation upconversion (TTA-UC). It is found that the chiral energy donor Pd(II) octaethylporphyrin derivative PdOEP-LG12 (RD) can selectively coassemble with the chiral energy acceptor LGAn (RA) with the same chiral scaffold but tends to form segregation with the energy acceptor DGAn (SA) with the opposite chiral scaffold in a thermodynamic equilibrium state. Thus, the coassembly of RA/RDshows more effective triplet–triplet energy transfer (TTET) and stronger upconverted luminescence and upconverted circularly polarized luminescence in comparison to the segregation of SA/RD. The establishment of such an enantioselective TTA-UC system highlights the applications of chirality-regulated triplet fusion in optoelectronic materials.