Search

Abstract Colorful circularly polarized luminescence materials are desired for 3D displays, information security and asymmetric synthesis, in which single-emitted materials are ideal owing to self-absorption avoidance, evenly entire-visible-spectrum-covered photon emission and facile device fabrication. However, restricted by the synthesis of chiral broad-luminescent emitters, the realization and application of high-performing single-emitted full-color circularly polarized luminescence is in its infancy. Here, we disclose a single-emitted full-color circularly polarized luminescence system (spiral full-color emission generator), composed of whole-vis-spectrum emissive quantum dots and chiral liquid crystals. The system achieves a maximum luminescence dissymmetry factor of 0.8 and remains an order of 10−1 in visible region by tuning its photonic bandgap. We then expand it to a series of desired customized-color circularly polarized luminescence, build chiral devices and further demonstrate the working scenario in the photoinduced enantioselective polymerization. This work contributes to the design and synthesis of efficient chiroptical materials, device fabrication and photoinduced asymmetric synthesis.

Solid-state electrolytes are key ingredients in next-generation devices for energy storage and release. Machine learning molecular dynamics (MLMD) has shown great promise in studying the diffusivity of mobile ions in solid-state electrolytes, with much higher efficiency than conventional ab initio molecular dynamics (AIMD). In this work, we combine an efficient embedded atom neural network (EANN) approach and an uncertainty-driven active learning algorithm that optimally selects data points from high-temperature AIMD trajectories to construct ML potentials for solid-state electrolytes and validate this strategy in a benchmark system, Li3YCl6, for which several controversy theoretical results exist. Through systematic MLMD simulations, we find that a typically used small supercell in AIMD simulations fails to predict the supersonic transition at a critical temperature, leading to a significant overestimation of the Li+ conductivity in Li3YCl6 at room temperature. Fortunately, thanks to the scalability of the EANN potential, extended MLMD simulations in a sufficiently large cell does yield a notable change of temperature-dependence in conductivity at ∼420 K and a much lower room-temperature conductivity in excellent with experiment. Interestingly, our results are all based on a semi-local PBE density functional, which was argued unable to predict the superionic transition. We analyze possible reasons of the seemingly inconsistent MLMD results reported in literature with different ML potentials. This work paves the way of simply using high-temperature AIMD data to generate more reliable MLMD results of low-temperature ionic conductivities in solid-state electrolytes.

Chiral emitters with high photoluminescence quantum yield are desirable for use in circularly polarized LEDs. The authors demonstrate the transfer of chirality from nanoscale copper iodide clusters to microscale chiral luminescent polycrystals by non-classical crystallization.

Background: Due to their long history, complex admixture processes and large population sizes, more research is required to explore the fine genetic structure of Han populations from different geographic locations of China. Aim: To characterise the paternal genetic structure of the Han Chinese in Henan province, which was once the central living region of the ancient Huaxia population, the precursors of the Han Chinese. Subjects and methods: We sequenced Y chromosomes of 60 males from Zhengzhou, Henan Province, and reconstructed a phylogenetic tree for these samples with age estimation. Results: We observed high diversity of paternal lineages in our collection. We found that the in situ Neolithic expansion of the “Major lineages” contributed to a large portion of the paternal gene pool of the Han population in Henan Province. We also detected a large number of “Minor lineages” that diverged in the Palaeolithic Age. Conclusion: We suggest that the high genetic diversity in the paternal gene pool of modern Han populations is mainly attributed to the reservation of a larger number of lineages that diverged in the Palaeolithic Age, while the recent expansion of limited lineages contributed to the majority of the gene pool of modern Han populations. We propose that such a structure is a basal characteristic for the genetic structure of modern Han populations.

Metal halide perovskite is well-known for the high absorption coefficient; however, its Li-ion transport property remains poorly explored. Here the authors coat an ion conducting metal chloride perovskite interfacial layer on the Li metal anode, enabling good battery performance.

Abstract The application of prestresses is a valuable strategy for enhancing the overall mechanical performances of structural materials. Residual stresses, acting as prestresses, exist naturally in biological structural materials, such as the nacre with the 3D “brick‐and‐mortar” arrangement. Although regulation of the tablets sliding has recently been demonstrated to be vital to improve toughness in synthetic nacre‐like structures, the effects of prestresses on the tablets‐sliding mechanism in these nacre‐like structures remain unclear. Here, by a combination of simulation, additive manufacturing, and drop tower testing the authors reveal that, at a critical prestress, synergistic effects between the prestress‐enhanced tablets sliding and prestress‐weakened structural integrality result in optimized impact resistance of nacre‐like structures. Furthermore, the prestressing strategy is easily implemented to a designed nacre‐inspired separator to enhance the impact resistance of lithium batteries. The findings demonstrate that the prestressing strategy combined with bioinspired architectures can be exploited for enhancing the impact resistance of engineering structural materials and energy storage devices.

All‐inorganic cesium lead halide perovskite colloidal nanocrystals (NCs) (CsPbX3, X = Cl, Br, I) have emerged as potential candidates for next‐generation light‐emitting diodes (LEDs). However, high trap states on the surface of CsPbX3 NCs caused by ionic nature and dynamic bonding of organic ligands limit the performance of CsPbX3 NCs‐based LEDs. Herein, a microemulsion (ME)‐modified strategy to decorate CsPbBr3 NC cores with inorganic PbWO4 is developed. It is demonstrated that ME‐assisted modification plays a crucial role in bridging the WO42− anion solution and the CsPbBr3 NC suspension. Compared with pristine CsPbBr3 NCs, the obtained PbWO4‐modified NCs exhibit improved photoluminescence efficiency. The corresponding NC films also show enhanced stability at elevated temperature and also in humid atmosphere. Consequently, the PbWO4‐modified NCs‐based LED exhibits a pronounced improvement of electroluminescence with an external quantum efficiency from 0.2% to 5.7% and twofold enhancement of the operational lifetime through PbWO4 passivation in comparison with that of pristine CsPbBr3 NCs‐based LED. These results show a promising pathway by ME‐induced anionic modification for high‐performance and stable LEDs based on perovskite NCs.

Lithium metal is the anode of choice for the next-generation high energy density batteries. To address the key technological challenges, the authors report a hybrid Li anode design with hierarchical pores structure derived from natural diatomite and improved electrochemical performance in all-solid-state lithium batteries.

Artificial materials that replicate the mechanical properties of nacre represent important structural materials, but are difficult to produce in bulk. Here, the authors exploit the bottom-up assembly of 2D nacre-mimetic films to fabricate 3D bulk artificial nacre with an optimized architecture and excellent mechanical properties.

Unique ultrathin Co[Se.sub.2]-DETA (protonated) mesostructured nanobelts with multiple stacked layers that are parallel to the axial direction are prepared in a binary solution composed of organic amine and water under mild solvothermal conditions. This strategy might provide new ways for preparing other new mesostructured nanomaterials, which might bring new nontrivial functionalities.

All-inorganic cesium lead-halide perovskite nanocrystals have emerged as attractive optoelectronic nanomaterials owing to their stabilities and highly efficient photoluminescence. Herein we report a new type of highly luminescent perovskite-related CsPb2Br5 nanoplatelets synthesized by a facile precipitation reaction. The layered crystal structure of CsPb2Br5 promoted an anisotropic two-dimensional (2D) crystal growth during the precipitation process, thus enabling the large-scale synthesis of CsPb2Br5 nanoplatelets. Fast anion exchange has also been demonstrated in as-synthesized CsPb2Br5 nanoplatelets to extend their photoluminescence spectra to the entire visible spectral region. The large-scale synthesis and optical tunability of CsPb2Br5 nanoplatelets will be advantageous in future applications of optoelectronic devices. [ABSTRACT FROM AUTHOR]

We theoretically investigate the Autler-Townes (AT) splitting in the photoelectron spectra of three-level ladder K2 molecule driven by a pump-probe pulse via employing the time-dependent wave packet approach. The dependence of AT splitting on two laser intensities and wavelengths are studied in detail. We firstly quantify these effects on peak shift and AT separation. The photoelectron spectra show double splitting with symmetric profiles, but with asymmetric profiles when the wavelength is changed. The magnitude of AT splitting increases with the pump laser intensity, but does not vary with probe intensity. The shifts of the absorption peaks and the splitting between AT doublet are predicted by using an analytical fitting function when the intensity/wavelength of one of the two fields is changed. These novel results are of importance for the molecular spectroscopy and may further stimulate the first principles theoretical studies analytically. [ABSTRACT FROM AUTHOR]

The accurate theoretical expressions of the mean field operator associated with the multi-configuration time-dependent Hartree—Fock (MCTDHF) method are presented in this paper. By using a theoretical formula, derived without approximation, we can study the multi-electron correlation dynamics accurately. Some illustrative calculations are carried out to check the accuracy of the expression of the mean field operator. The results of illustrative calculations indicate the reliability of the accurate expression of the mean field operator. This theoretical calculation method for the mean field operator may be of considerable help in future studies of the correlated dynamics of many-electron systems in strong laser fields. [ABSTRACT FROM AUTHOR]

The morphological and structural transformation process of the water soluble zirconium–glycine hybrid cluster [Zr6(O)4(OH)4(H2O)8(Gly)8]12+(CP-2) in a bovine serum albumin (BSA) protein matrix was comprehensively investigated. Based on the zeta-potential analysis, positive CP-2 clusters tend to adsorb onto the surface of the backbone of BSA, forming BSA–CP-2 hybrids through direct mixing. After aging the solution at 37 °C for several weeks, white floccules appeared in solution indicating the phase transformation of BSA–CP-2 bio–inorganic hybrid. A series of characterizations (zeta-potential measurements, dynamic light scattering measurements, transmission and scanning electron microscopy, X-ray diffraction, and so on) were carried out to analyze the interaction between CP-2 and BSA under varying pH value and salt concentrations in order to demonstrate the transformation of the CP-2 to amorphous ziconium hydroxide. The coagulant action of CP-2 with BSA indicates that the zirconium(iv)–glycine complex may be efficacious as an antiperspirant and in water treatment. [ABSTRACT FROM AUTHOR]

Nanostructural evolution of II–VI semiconductors emerges as a hot research field because it offers a novel route for the synthesis of functional semiconductor nanomaterials. Here, we report a “top-down” process of structural evolution from two dimensional Cd2Se2(pa) hybrid structures to zero- or one- dimensional CdSe nanostructures. We firstly synthesized the Cd2Se2(pa) hybrid by a facile solvothermal reaction and determined the hybrid crystal structure through the Rietveld refinement based on the PXRD data. The (Cd2Se2)(pa) hybrid consists of [Cd2Se2] slabs sandwiched by coordinated n-propylamine layers. Then, we used this hybrid as a precursor to explore the “top-down” fabrication process of structural evolution from two dimensional layered structures to zero- or one- dimensional nanocrystals. It has been shown that various CdSe nanostructures including lamellar structures, nanoparticles, nanowires, and nanorods can be obtained through the pyrolysis of (Cd2Se2)(pa) hybrid precursor under different conditions. It is worth mentioning that the oriented attachment of nanoparticles has been observed during the pyrolysis process. Additionally, the variation of optical properties with structural evolution has been investigated in detail. [ABSTRACT FROM AUTHOR]

Fluorescent graphene-CdSe quantum dot (QD) (G-CdSe) nanocomposites with tunable optical properties can be prepared by a one-pot facile decoration of CdSe QDs on graphene nanosheets. The formation of such nanocomposites is based on the interaction between the surfactants on the surfaces of the synthesized graphene and the CdSe QDs through electrostatic interactions and van der Waals forces of the long chain alkane surfactants. PXRD, TEM and PL spectra have been acquired to demonstrate the successful decoration of CdSe QDs on graphene nanosheets. This kind of nanocomposite may have potential applications in bio-imaging and light emitting devices in the future. [ABSTRACT FROM AUTHOR]

A photo-thermal/catalytic reduction lithography (PRL) approach for the fabrication of photoconductive patterns by 300 W Xe lamp illumination of the (PDDA/GO/PDDA/TiO)20hybrid films formed through layer by layer (LBL) assembly technique has been reported. High quality (PDDA/GO/PDDA/TiO)20hybrid films were fabricated on the glass substrate through alternative LBL self-assembly with graphene oxide (GO), titania (TiO) nanosheets, and poly(diallyldimethylammonium) (PDDA). Then, the photoconductive pattern was fabricated by illuminating the hybrid film equipped with a pre-designed aluminium foil as the shadow mask. The “on-off” photoconductive response of the fabricated pattern was directly tested due to the photo-electro conversion role of TiO nanosheets and electronic transportation of reduced GO (RGO) nanosheets, which shows a high photocurrent generation and good reversibility. [ABSTRACT FROM AUTHOR]

A low molecular weight organic molecule, 1,3-diamino-2-hydroxypropane-N,N,N′,N′-tetraacetic acid, has been found that it could stabilize amorphous calcium carbonate (ACC) for at least three days in a gas diffusion reaction, also it could control the formation of hierarchical calcite crystals. The transformation process from ACC to calcite crystals has been systematically studied. Nucleation sites and intermediates were both captured by time-dependent experiments. It is found that ACC could form a close packed film on the substrate and part of the nucleation occurred on the film. After nucleation, another form of ACC conglomeration was found to be dissolved from inside. The intermediates on the substrate were found to be composed of fibres. A rod-dumbbell-sphere transformation phenomenon was observed. Selective adsorption and the mesocrystal transformation mechanism are assumed to play a key role in the formation of intermediates with different shapes and structures. [ABSTRACT FROM AUTHOR]

Monodisperse cubic pyrite NiS2dodecahedrons and microspheres with a diameter of 6 µm have been synthesized by a solvothermal approach in ethylenediamine–glycol mixed solvent at 200 °C using NiCl2·6H2O and sulfur as precursors. The morphology and the phase transformation of the products were found to be strongly dependent on the reaction temperature, reaction time, and the volume ratio of ethylenediamine to glycol. The thermal stability of the pyrite NiS2dodecahedrons has been studied and they can act as excellent templates for synthesis of porous NiO microspheres by calcination in air. The NiS2dodecahedrons show antiferromagnetic properties between 10 and 300 K. The present solvothermal approach in a mixed solvent system may allow to synthesize other metal chalcogenides with unique shapes and structures. [ABSTRACT FROM AUTHOR]

Highly hierarchical platelike FeWO4 microcrystals have been synthesized by a simple solvothermal route using FeCI3. 6H2O and Na2WO4 2H2O as precursors, where ethylene glycol (EG) plays an important role as a capping agent in directing growth and self-assembly of such unique structures. In addition, a certain amount of CH3COONa (NaAc) was necessary for the formation of such unique FeWO4 microstructures. The photocatalytic property of as-synthesized hierarchical FeWO4 microcrystals has been first studied, which shows excellent photocatalytic activity for the degradation of rhodamine B (RhB) under UV and visible light irradiation (modeling sunlight). Moreover, magnetic measurement indicates that hexangular FeWO4 platelike microcrystals show a small ferromagnetic ordering at low temperature because of spin-canting of antiferromagnetic materials and surface spins of FeWO4 nanoparticles. [ABSTRACT FROM AUTHOR]

A solvothermal reaction in a mixed solvent made of triethylenetetriamine (TETA) and deionized water (DIW) results in the formation of well-defined [Fe 18S 25](TETAH) 14nanoribbons. A suitable volume ratio of TETA and DIW is essential for the formation of elegant [Fe 18S 25](TETAH) 14nanoribbons. The [Fe 18S 25](TETAH) 14nanoribbons can act as efficient precursors for production of either Fe 7S 8nanowires or porous α-Fe 2O 3nanorods by thermal decomposition of [Fe 18S 25](TETAH) 14in an argon or air atmosphere. The present study demonstrates that the combination of small molecule polyamine with magnetic semiconductor makes it possible to obtain new hybrid nanostructured materials. The thermal decomposition of this new hybrid material is a powerful tool as a unique pathway for controlled synthesis of transition metal chacolgenide nanomaterials and porous transition metal oxides. [ABSTRACT FROM AUTHOR]

A new family of lamellar transition-metal (Ni, Co) molybdate-cetyltrimethylammonium (CTA) mesostructured composites has been synthesized by a simple chemical precipitation method. These lamellar mesostructured composites display enhanced capability in treatment of acid fuchsine in comparison with the corresponding metal molybdates and lamellar molybdenum oxide-CTA. [ABSTRACT FROM AUTHOR]

We investigate atomic above-threshold ionization in elliptically polarized strong laser fields with a semiclassical approach. With increasing laser intensity, the Coulomb focusing (CF) effects are found to become stronger in both parallel and perpendicular directions with respect to the polarization plane. The dependence of CF effects on tunnel exit, initial transverse momentum distribution and laser electric field is analyzed. It was revealed that the effects of tunnel exit are most prominent with variation of the laser intensity, and the other two factors both play non-negligible roles. Our results provide a deeper insight to the recent experiments of Coulomb asymmetry [Shafir D, et al., 2013 Phys. Rev. Lett.111 023005 and Li M, et al., 2013 Phys. Rev. Lett.111 023006]. [ABSTRACT FROM AUTHOR]

Although biomimetic designs are expected to play a key role in exploring future structural materials, facile fabrication of bulk biomimetic materials under ambient conditions remains a major challenge. Here, we describe a mesoscale “assembly-and-mineralization” approach inspired by the natural process in mollusks to fabricate bulk synthetic nacre that highly resembles both the chemical composition and the hierarchical structure of natural nacre.The millimeter-thick synthetic nacre consists of alternating organic layers and aragonite platelet layers (91 weight percent) and exhibits good ultimate strength and fracture toughness.This predesigned matrix-directed mineralization method represents a rational strategy for the preparation of robust composite materials with hierarchically ordered structures,where various constituents are adaptable, including brittle and heat-labile materials. [ABSTRACT FROM AUTHOR]

The article reports on a simple method for direct synthesis of the first mesostructed CoSe2-amine nanobelts, triethylenetetramine, and tetraethylenepentamine in a binary solution under solvothermal conditions. The CoSe2-amine nanobelts were synthesized by solvothermal reaction of Co(Ac)2 H2O and Na2SeO3. Moreover, this synthesis strategy may open new avenues toward the syntheses of other new mesostructured nanomaterials.