A quantum spin liquid is a state of matter where unpaired electrons’ spins, although entangled, do not show magnetic order even at the zero temperature. The realization of a quantum spin liquid is a ...long-sought goal in condensed-matter physics. Although neutron scattering experiments on the two-dimensional spin-1/2 kagome lattice ZnCu3(OD)6Cl2 and triangular lattice YbMgGaO4 have found evidence for the hallmark of a quantum spin liquid at very low temperature (a continuum of magnetic excitations), the presence of magnetic and non-magnetic site chemical disorder complicates the interpretation of the data. Recently, the three-dimensional Ce3+ pyrochlore lattice Ce2Sn2O7 has been suggested as a clean, effective spin-1/2 quantum spin liquid candidate, but evidence of a spin excitation continuum is still missing. Here, we use thermodynamic, muon spin relaxation and neutron scattering experiments on single crystals of Ce2Zr2O7, a compound isostructural to Ce2Sn2O7, to demonstrate the absence of magnetic ordering and the presence of a spin excitation continuum at 35 mK. With no evidence of oxygen deficiency and magnetic/non-magnetic ion disorder seen by neutron diffraction and diffuse scattering measurements, Ce2Zr2O7 may be a three-dimensional pyrochlore lattice quantum spin liquid material with minimum magnetic and non-magnetic chemical disorder.
Self-assembly of twelve pentatopic tectons, which have complementary edges or can be linked using either digonal or trigonal connectors, represents the optimal synthetic strategy to achieve spherical ...objects, such as chemical capsids. This process requires conditions that secure uninterrupted equilibria of binding and self-correction en route to the global energy minimum. Here we report the synthesis of a highly soluble, deca-heterosubstituted corannulene that bears five terpyridine ligands. Spontaneous self-assembly of twelve such tectons with 30 cadmium(II) cations produces a giant icosahedral capsid as a thermodynamically stable single product in high yield. Nuclear magnetic resonance (NMR) methods, mass spectrometry analyses, small-angle X-ray scattering, transmission electron microscopy, and atomic force microscopy indicate that this spherical capsid has an external diameter of nearly 6 nm and shell thickness of 1 nm, in agreement with molecular modeling. NMR and liquid chromatography evidences imply that chiral self-sorting complexation generates a racemic mixture of homochiral capsids.
Triangular lattice of rare-earth ions with interacting effective spin-1/2local moments is an ideal platform to explore the physics of quantum spin liquids (QSLs) in the presence of strong spin-orbit ...coupling, crystal electric fields, and geometrical frustration. The Yb delafossites,NaYbCh2(Ch=O, S, Se) with Yb ions forming a perfect triangular lattice, have been suggested to be candidates for QSLs. Previous thermodynamics, nuclear magnetic resonance, and powder-sample neutron scattering measurements onNaYbCh2have supported the suggestion of the QSL ground states. The key signature of a QSL, the spin excitation continuum, arising from the spin quantum number fractionalization, has not been observed. Here we perform both elastic and inelastic neutron scattering measurements as well as detailed thermodynamic measurements on high-quality single-crystalNaYbSe2samples to confirm the absence of long-range magnetic order down to 40 mK, and further reveal a clear signature of magnetic excitation continuum extending from 0.1 to 2.5 meV. The comparison between the structure of the magnetic excitation spectra and the theoretical expectation from the spinon continuum suggests that the ground state ofNaYbSe2is a QSL with a spinon Fermi surface.
Four soluble dialkylated tetrathienoacene (TTAR)‐based small molecular semiconductors featuring the combination of a TTAR central core, π‐conjugated spacers comprising bithiophene (bT) or thiophene ...(T), and with/without cyanoacrylate (CA) end‐capping moieties are synthesized and characterized. The molecule DbT‐TTAR exhibits a promising hole mobility up to 0.36 cm2 V−1 s−1 due to the enhanced crystallinity of the microribbon‐like films. Binary blends of the p‐type DbT‐TTAR and the n‐type dicyanomethylene substituted dithienothiophene‐quinoid (DTTQ‐11) are investigated in terms of film morphology, microstructure, and organic field‐effect transistor (OFET) performance. The data indicate that as the DbT‐TTAR content in the blend film increases, the charge transport characteristics vary from unipolar (electron‐only) to ambipolar and then back to unipolar (hole‐only). With a 1:1 weight ratio of DbT‐TTAR DTTQ‐11 in the blend, well‐defined pathways for both charge carriers are achieved and resulted in ambipolar transport with high hole and electron mobilities of 0.83 and 0.37 cm2 V−1 s−1, respectively. This study provides a viable way for tuning microstructure and charge carrier transport in small molecules and their blends to achieve high‐performance solution‐processable OFETs.
Solution‐processable dialkylated tetrathienoacene (TTAR)‐derived organic semiconductor and its blends are investigated for organic transistor applications. Blends of the p‐type DbT‐TTAR with the n‐type DTTQ‐11 in 1:1 weight ratio exhibit maximum ambipolar (hole and electron) mobilities of 0.83 and 0.37 cm2 V−1 s−1, respectively, the largest reported so far.
The passivation of perovskite interfacial defects by the electron transport layer (ETL) has emerged as an effective strategy for enhancing the performance of perovskite solar cells (PSCs). ...Dithieno2,3‐d:2′,3′‐d′thieno3,2‐b:3′,2′‐b′dipyrrole (DTPT)‐based acceptor‐donor‐acceptor (A–D–A) molecules composed of coplanar heteroacene as electron‐donating core end‐capped with various electron‐accepting moieties are designed and examined as ETL modifiers for PSCs. Employing PCBM:DTPTCY as the ETL results in passivation perovskite defects, facilitation energy alignment at the ETL/perovskite interface, and enhancement of carrier transport efficiency. The optimized blended ETL‐based Cs0.18FA0.82Pb(I0.8Br0.2)3 p‐i‐n PSC exhibit performances of 37.2% and 39.9% under TL84 and 3000K LED (1000 lux), respectively. The DTPTCY‐based device demonstrates remarkable stability, retaining 87% of its initial power conversion efficiency (PCE) after 30 days of storage in a 40% relative humidity (RH) ambient air environment without any encapsulation, surpassing the control device, which retains only 67% of its original PCE. These findings underscore the potential of A–D–A‐type molecule‐based interface modification to enhance passivation and contact properties, ultimately leading to high‐efficiency and stable PSCs.
Remarkable results are attained in indoor Perovskite Solar Cells, achieving an impressive efficiency of 39.9% (3000K LED (1000 lux)) through the application of an A–D–A‐type molecule for defect passivation within the electron transport layer.
New 3,3′‐dithioalkyl‐2,2′‐bithiophene (SBT)‐based small molecular and polymeric semiconductors are synthesized by end‐capping or copolymerization with dithienothiophen‐2‐yl units. Single‐crystal, ...molecular orbital computations, and optical/electrochemical data indicate that the SBT core is completely planar, likely via S(alkyl)⋯S(thiophene) intramolecular locks. Therefore, compared to semiconductors based on the conventional 3,3′‐dialkyl‐2,2′‐bithiophene, the resulting SBT systems are planar (torsional angle <1°) and highly π‐conjugated. Charge transport is investigated for solution‐sheared films in field‐effect transistors demonstrating that SBT can enable good semiconducting materials with hole mobilities ranging from ≈0.03 to 1.7 cm2 V−1 s−1. Transport difference within this family is rationalized by film morphology, as accessed by grazing incidence X‐ray diffraction experiments.
New 3,3′‐dithioalkyl‐2,2′‐bithiophene (SBT)‐based small‐molecular and polymeric semiconductors are synthesized by end‐capping or copolymerization with dithienothiophen‐2‐yl units. Charge transport is investigated for solution‐sheared films in field‐effect transistors demonstrating that SBT can enable good charge transport with hole mobilities ranging from ≈0.03 to 1.7 cm2 V−1 s−1.
Molecules based on benzimidazolone‐dioxazine are known as blue/violet pigments and have been commercialized for decades. However, unfavorable solubility limits the application of these structures as ...building blocks of conjugated polymers despite their low band gaps. Herein, a series of donor–acceptor conjugated polymers containing soluble benzimidazolone‐dioxazine structures as the acceptors and oligothiophene as donors are synthesized and investigated. With increasing numbers of thiophene rings, the steric hindrance diminishes and high molecular weight polymers can be achieved, leading to an improved performance in organic field effect transistor devices. The hole mobility of polymers with three to six thiophene units is in the order of 10−1 cm2 V−1 s −1. Among all the polymers, polymer P3 with three thiophene units between benzimidazolone‐dioxazine structures shows the best hole mobility of 0.4 cm2 V−1 s −1. Grazing‐incidence wide‐angle X‐ray scattering results reveal that the high mobility of organic field‐effect transistors (OFETs) can be accredited by matched donor–acceptor packing in the solid thin films.
A series of novel benzimidazolone‐dioxazine‐based donoracceptor conjugated polymers are synthesized and investigated. With increasing numbers of thiophene rings, the steric hindrance diminishes and high molecular weight polymers can be achieved, leading to an improved performance in organic field effect transistor devices. The polymer with three thiophene units shows the best hole mobility of 0.4 cm2 V−1 s−1.
To turn on the fluorescence of the native green fluorescence protein (GFP) chromophore, 4‐hydroxybenzylidene‐dimethylimidazolinone (HBDI), in an artificial supramolecular system has been a ...challenging task, because it requires high local environmental rigidity. This work shows that the formation of H‐aggregates of an HBDI‐containing organogelator results in two orders of magnitude fluorescence enhancement (Φf=2.9 vs. 0.02 %), in which the inter‐HBDI OH⋅⋅⋅OH H‐bonds play a crucial role. The aggregation‐induced fluorescence enhancement of HBDI has important implications on the origin of the high fluorescence quantum efficiency of HBDI in the GFP β‐barrel and on the supramolecular strategy for a full fluorescence recovery of HBDI. These results reveal a new approach to designing rigid chromophore aggregates for high‐performance optoelectronic properties.
Out of the barrel: The formation of H‐aggregates for an 4‐hydroxybenzylidene‐dimethylimidazolinone (HBDI)‐containing organogelator enhances the fluorescence quantum efficiency by two orders of magnitude, a new record for HBDI in an artificial supramolecular system.
The microscopic mechanism governing the zero-resistance flow of current in some iron-based, high-temperature superconducting materials is not well understood up to now. A central issue concerning the ...investigation of these materials is their superconducting gap symmetry and structure. Here we present a combined study of low-temperature specific heat and scanning tunnelling microscopy measurements on single crystalline FeSe. The results reveal the existence of at least two superconducting gaps which can be represented by a phenomenological two-band model. The analysis of the specific heat suggests significant anisotropy in the gap magnitude with deep gap minima. The tunneling spectra display an overall "U"-shaped gap close to the Fermi level away as well as on top of twin boundaries. These results are compatible with the anisotropic nodeless models describing superconductivity in FeSe.
Repurposing existing compounds for new indications may facilitate the discovery of skin prebiotics which have not been well defined. Four compounds that have been registered by the International ...Nomenclature of Cosmetic Ingredients (INCI) were included to study their abilities to induce the fermentation of Staphylococcus epidermidis (S. epidermidis), a bacterial species abundant in the human skin. Liquid coco-caprylate/caprate (LCC), originally used as an emollient, effectively initiated the fermentation of S. epidermidis ATCC 12228, produced short-chain fatty acids (SCFAs), and provoked robust electricity. Application of LCC plus electrogenic S. epidermidis ATCC 12228 on mouse skin significantly reduced ultraviolet B (UV-B)-induced injuries which were evaluated by the formation of 4-hydroxynonenal (4-HNE), cyclobutane pyrimidine dimers (CPD), and skin lesions. A S. epidermidis S2 isolate with low expressions of genes encoding pyruvate dehydrogenase (pdh), and phosphate acetyltransferase (pta) was found to be poorly electrogenic. The protective action of electrogenic S. epidermidis against UV-B-induced skin injuries was considerably suppressed when mouse skin was applied with LCC in combination with a poorly electrogenic S. epidermidis S2 isolate. Exploring new indication of LCC for promoting S. epidermidis against UV-B provided an example of repurposing INCI-registered compounds as skin prebiotics.
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