A Non-Conjugated Polymer Acceptor for Efficient and Thermally Stable All-Polymer Solar Cells

A non-conjugated polymer acceptor PF1-TS4 was firstly synthesized by embedding a thioalkyl segment in the mainchain, which shows excellent photophysical properties on par with a fully conjugated polymer, with a low optical band gap of 1.58 eV and a high absorption coefficient >10⁵ cm⁻¹, a high LUMO level of −3.89 eV, and suitable crystallinity. Matched with the polymer donor PM6, the PF1-TS4-based all-PSC achieved a power conversion efficiency (PCE) of 8.63 %, which is ≈45 % higher than that of a device based on the small molecule acceptor counterpart IDIC16. Moreover, the PF1-TS4-based all-PSC has good thermal stability with ≈70 % of its initial PCE retained after being stored at 85 °C for 180 h, while the IDIC16-based device only retained ≈50 % of its initial PCE when stored at 85 °C for only 18 h. Our work provides a new strategy to develop efficient polymer acceptor materials by linkage of conjugated units with non-conjugated thioalkyl segments.     

The Stabilization Effect of CO2 in Lithium–Oxygen/CO2 Batteries

The lithium (Li)–air battery has an ultrahigh theoretical specific energy, however, even in pure oxygen (O₂), the vulnerability of conventional organic electrolytes and carbon cathodes towards reaction intermediates, especially O₂⁻, and corrosive oxidation and crack/pulverization of Li metal anode lead to poor cycling stability of the Li-air battery. Even worse, the water and/or CO₂ in air bring parasitic reactions and safety issues. Therefore, applying such systems in open-air environment is challenging. Herein, contrary to previous assertions, we have found that CO₂ can improve the stability of both anode and electrolyte, and a high-performance rechargeable Li–O₂/CO₂ battery is developed. The CO₂ not only facilitates the in situ formation of a passivated protective Li₂CO₃ film on the Li anode, but also restrains side reactions involving electrolyte and cathode by capturing O₂⁻. Moreover, the Pd/CNT catalyst in the cathode can extend the battery lifespan by effectively tuning the product morphology and catalyzing the decomposition of Li₂CO₃. The Li–O₂/CO₂ battery achieves a full discharge capacity of 6628 mAh g⁻¹ and a long life of 715 cycles, which is even better than those of pure Li–O₂ batteries.     

Proving and Probing the Presence of the Elusive C−H⋅⋅⋅O Hydrogen Bond in Liquid Solutions at Room Temperature

Hydrogen bonds (H bonds) play a major role in defining the structure and properties of many substances, as well as phenomena and processes. Traditional H bonds are ubiquitous in nature, yet the demonstration of weak H bonds that occur between a highly polarized C−H group and an electron-rich oxygen atom, has proven elusive. Detailed here are linear and nonlinear IR spectroscopy experiments that reveal the presence of H bonds between the chloroform C−H group and an amide carbonyl oxygen atom in solution at room temperature. Evidence is provided for an amide solvation shell featuring two clearly distinguishable chloroform arrangements that undergo chemical exchange with a time scale of about 2 ps. Furthermore, the enthalpy of breaking the hydrogen bond is found to be 6–20 kJ mol⁻¹. Ab-initio computations support the findings of two distinct solvation shells formed by three chloroform molecules, where one thermally undergoes hydrogen-bond making and breaking.     

A Layered Cationic Aluminum Oxyhydroxide as a Highly Efficient and Selective Trap for Heavy Metal Oxyanions

Cationic framework materials, especially pure inorganic cationic frameworks that can efficiently and selectively capture harmful heavy metal oxyanions from aqueous solution are highly desired yet scarcely reported. Herein, we report the discovery of a 2D cationic aluminum oxyhydroxide, JU-111, which sets a new benchmark for heavy metal oxyanion sorbents, especially for Cr^VI. Its structure was solved based on 3D electron diffraction tomography data. JU-111 shows fast sorption kinetics (ca. 20 min), high capture capacity (105.4 mg g⁻¹), and broad working pH range (3–10) toward Cr^VI oxyanions. Unlike layered double hydroxides (LDHs), which are poorly selective in the presence of CO₃²⁻, JU-111 retains excellent selectivity for Cr^VI even under a large excess of CO₃²⁻. These superior features coupled with the ultra-low cost and environmentally benign nature make JU-111 a promising candidate for toxic metal oxyanion remediation as well as other potential applications.     

Rhombicuboctahedral Ag100: Four-Layered Octahedral Silver Nanocluster Adopting the Russian Nesting Doll Model

Precise atomic structure of metal nanoclusters (NCs) is fundamental for elucidating the structure–property relationships and the inherent size-evolution principles. Reported here is the largest known FCC-based (FCC=face centered cubic) silver nanocluster, [Ag₁₀₀(SC₆H₃^3,4F₂)₄₈(PPh₃)₈]⁻: the first all-octahedral symmetric nesting Ag nanocluster with a four-layered Ag₆@Ag₃₈@Ag₄₈S₂₄@Ag₈S₂₄P₈ structure, consistent symmetry elements, and a unique rhombicuboctahedral morphology distinct from theoretical predictions and previously reported FCC-based Ag clusters. DFT studies revealed extensive interlayer interactions and degenerate frontier orbitals. The FCC-based Russian nesting doll model constitutes a new platform for the study of the size-evolution principles of Ag NCs.     

ACQ-to-AIE Transformation: Tuning Molecular Packing by Regioisomerization for Two-Photon NIR Bioimaging

The traditional design strategies for highly bright solid-state luminescent materials rely on weakening the intermolecular π–π interactions, which may limit diversity when developing new materials. Herein, we propose a strategy of tuning the molecular packing mode by regioisomerization to regulate the solid-state fluorescence. TBP-e-TPA with a molecular rotor in the end position of a planar core adopts a long-range cofacial packing mode, which in the solid state is almost non-emissive. By shifting molecular rotors to the bay position, the resultant TBP-b-TPA possesses a discrete cross packing mode, giving a quantum yield of 15.6±0.2 %. These results demonstrate the relationship between the solid-state fluorescence efficiency and the molecule's packing mode. Thanks to the good photophysical properties, TBP-b-TPA nanoparticles were used for two-photon deep brain imaging. This molecular design philosophy provides a new way of designing highly bright solid-state fluorophores.     

Anisotropic Protein Organofibers Encoded With Extraordinary Mechanical Behavior for Cellular Mechanobiology Applications

Hydrogels enable a variety of applications due to their dynamic networks, structural flexibility, and tailorable functionality. However, their mechanical performances are limited, specifically in the context of cellular mechanobiology. It is also difficult to fabricate robust gel networks with a long-term durability. Thus, a new generation of soft materials showing outstanding mechanical behavior for mechanobiology applications is highly desirable. We combined synthetic biology and supramolecular assembly to prepare elastin-like protein (ELP) organogel fibers with extraordinary mechanical properties. The mechanical performance and stability of the assembled anisotropic proteins are superior to other organo-/hydrogel systems. Bone-derived mesenchymal cells were introduced into the organofiber system for stem-cell lineage differentiation. This approach demonstrates the feasibility of mechanically strong and anisotropic organonetworks for mechanobiology applications and holds great potential for tissue-regeneration translations.     

Highly Efficient Deep-Red Non-Doped Diodes Based on a T-Shape Thermally Activated Delayed Fluorescence Emitter

Device simplification is of practical significance for organic light emitting diodes (OLEDs), and remains the great challenge for deep-red emitters. Herein, a deep-red thermally activated delayed fluorescence molecule ( p TPA-DPPZ ) is reported which features a T shaped structure containing two triphenylamine (TPA) donors, one either side of a planar dipyridophenazine (DPPZ) acceptor. The rational spatial arrangement of the functional groups leads to limited but sufficient molecular packing for effective carrier transport. The neat p TPA-DPPZ film achieves an around 90-fold improved radiation rate constant of 10⁷ s⁻¹ and the nearly unitary reverse intersystem crossing (RISC) efficiency, as well as accelerated emission decays for quenching suppression. The high radiation and RISC result in a photoluminescence quantum yield of 87 %. The bilayer OLED based on the p TPA-DPPZ emissive layer achieved the record external quantum efficiencies of 12.3 % for maximum and 10.4 % at 1000 nits, accompanied by the deep-red electroluminescence with the excellent color purity.     

Host Differential Sensitization toward Color/Lifetime-Tuned Lanthanide Coordination Polymers for Optical Multiplexing

Optical multiplexing based on luminescent materials with tunable color/lifetime has potential applications in information storage and security. However, the available tunable luminescent materials reported so far still suffer from several drawbacks of low efficiency or poor stability, thus restraining their further applications. Herein, we demonstrate a strategy to develop efficient and stable lanthanide coordination polymers (LCPs) with tunable luminescence as a new option for optical multiplexing. Their multicolor emission from green to red and naked-eye-sensitive green emission with tunable lifetime (from ca. 300 to ca. 600 μs) can be controlled by host differential sensitization and energy transfer between lanthanide ions. The quantum efficiencies of developed samples range from around 20 % to 46 % and the luminescence intensity/lifetime appear quite stable in polar solvents up to ten weeks. Furthermore, with the aid of inkjet printing and concepts of luminescence lifetime imaging and time-gated imaging, we illustrate their promising applications of information storage and security in spatial and temporal domains.     

PyCDFT: A Python package for constrained density functional theory

We present PyCDFT, a Python package to compute diabatic states using constrained density functional theory (CDFT). PyCDFT provides an object-oriented, customizable implementation of CDFT, and allows for both single-point self-consistent-field calculations and geometry optimizations. PyCDFT is designed to interface with existing density functional theory (DFT) codes to perform CDFT calculations where constraint potentials are added to the Kohn–Sham Hamiltonian. Here, we demonstrate the use of PyCDFT by performing calculations with a massively parallel first-principles molecular dynamics code, Qbox, and we benchmark its accuracy by computing the electronic coupling between diabatic states for a set of organic molecules. We show that PyCDFT yields results in agreement with existing implementations and is a robust and flexible package for performing CDFT calculations. The program is available at https://dx.doi.org/10.5281/zenodo.3821097 .