Showing papers in "Science China-chemistry in 2021"

Frontiers in circularly polarized luminescence: molecular design, self-assembly, nanomaterials, and applications

Abstract: The research in circularly polarized luminescence has attracted wide interest in recent years. Efforts on one side are directed toward the development of chiral materials with both high luminescence efficiency and dissymmetry factors, and on the other side, are focused on the exploitations of these materials in optoelectronic applications. This review summarizes the recent frontiers (mostly within five years) in the research in circularly polarized luminescence, including the development of chiral emissive materials based on organic small molecules, compounds with aggregation-induced emissions, supramolecular assemblies, liquid crystals and liquids, polymers, metal-ligand coordination complexes and assemblies, metal clusters, inorganic nanomaterials, and photon upconversion systems. In addition, recent applications of related materials in organic light-emitting devices, circularly polarized light detectors, and organic lasers and displays are also discussed.

High-performance polymer solar cells with efficiency over 18% enabled by asymmetric side chain engineering of non-fullerene acceptors

Abstract: Side-chain engineering has been considered as one of the most promising strategies to optimize non-fullerene small-molecule acceptors (NFSMAs). Previous efforts were focused on the optimization of alkyl-chain length, shape, and branching sites. In this work, we propose that asymmetric side-chain engineering can effectively tune the properties of NFSMAs and improve the power conversion efficiency (PCE) for binary non-fullerene polymer solar cells (NFPSCs). Specifically, by introducing asymmetric side chains into the central core, both of the absorption spectra and molecule orientation of NFSMAs are efficiently tuned. When blended with polymer donor PM6, NFPSCs with EH-HD-4F (2-ethylhexyl and 2-hexyldecyl side chains) demonstrate a champion PCE of 18.38% with a short-circuit current density (JSC) of 27.48 mA cm−2, an open circuit voltage (VOC) of 0.84 V, and a fill factor (FF) of 0.79. Further studies manifest that the proper asymmetric side chains in NFSMAs could induce more favorable face-on molecule orientation, enhance carrier mobilities, balance charge transport, and reduce recombination losses.

Achieving 16.68% efficiency ternary as-cast organic solar cells

Abstract: State-of-the-art organic solar cells (OSCs) often require the use of high-boiling point additive or post-treatment such as temperature annealing and solvent vapor annealing to achieve the best efficiency. However, additives are not desirable in large-scale industrial printing process, while post-treatment also increases the production cost. In this article, we report highly efficient ternary OSCs based on PM6:BTP-ClBr1:BTP-2O-4Cl-C12 (weight ratio=1:1:0.2), with 16.68% power conversion efficiency (PCE) for as-cast device, relatively close to its annealed counterpart (17.19%). Apart from obvious energy tuning effect and complementary absorption spectra, the improved PCE of ternary device is mainly attributed to improved morphological properties including the more favorable materials miscibility, crystallinity, domain size and vertical phase separation, which endorse suppressed recombination. The result of this work provides understanding and guidance for high-performance as-cast OSCs through the ternary strategy.

An A-D-A′-D-A type unfused nonfullerene acceptor for organic solar cells with approaching 14% efficiency

Abstract: In recent years, power conversion efficiency (PCE) of organic solar cells (OSCs) has made significant improvement. A large number of studies were reported to achieve high PCEs through exploring new active layer materials, especially the high efficiency fused ring acceptors (FRAs). Compared with FRAs, a nother type of so-called unfused-ring acceptors (UFAs), possessing some advantages such as simple synthesis and low cost, have attracted a lot of attention. Herein, a new UFA BTzO-4F , incorporating with a benzotriazole moiety and S···O intramolecular noncovalent interactions, has been successfully synthesized. The photovoltaic device based on PBDB-T: BTzO-4F achieved a record PCE of 13.8% for UFAs, which indicates that introducing the benzotriazole moiety is an effective strategy for high quality acceptors. Thus, these findings of this work demonstrate the great potential of UFAs for high performance OSCs.

Red-emitting, self-oxidizing carbon dots for the preparation of white LEDs with super-high color rendering index

Abstract: Carbon dots (CDs), as a kind of carbon nanomaterials, have attracted widespread attention due to their unique structure and excellent optical properties, and they are low-cost, environmentally friendly and biocompatible. However, the development of near-infrared (NIR) emission CDs remains a challenge. In this study, we successfully prepared CDs with a maximum emission of 714 nm using citric acid as the carbon source, thiourea and ammonium fluoride as the dopant source, and N,N-dimethylformamide as the solvent. The quantum yield (QY) is as high as 22.64%. Interestingly, the prepared CDs self-oxidize in the presence of oxygen, resulting in a blue shift of their emission. Therefore, they can be used to prepare white light-emitting diodes (WLEDs) without adding other fluorescent substances. Notably, the work presented herein constitutes the first report of WLEDs preparation from single CDs.

Nucleic Acids Analysis

Abstract: Nucleic acids are natural biopolymers of nucleotides that store, encode, transmit and express genetic information, which play central roles in diverse cellular events and diseases in living things. The analysis of nucleic acids and nucleic acids-based analysis have been widely applied in biological studies, clinical diagnosis, environmental analysis, food safety and forensic analysis. During the past decades, the field of nucleic acids analysis has been rapidly advancing with many technological breakthroughs. In this review, we focus on the methods developed for analyzing nucleic acids, nucleic acids-based analysis, device for nucleic acids analysis, and applications of nucleic acids analysis. The representative strategies for the development of new nucleic acids analysis in this field are summarized, and key advantages and possible limitations are discussed. Finally, a brief perspective on existing challenges and further research development is provided.

Challenges and perspectives of covalent organic frameworks for advanced alkali-metal ion batteries

Abstract: Covalent organic frameworks (COFs) are a class of porous crystalline polymers that have been widely investigated in various fields, including energy storage, photo/electrocatalysis, drug delivery. The covalent-bond interconnection allows COFs extraordinary chemical and thermal stability, and the porous structure ensures a high ion-diffusion coefficient. These merits compensate for the drawbacks of organic electrodes that are easy to dissolve and have low charge conductivity, and promote the development of novel electrode materials with excellent performance, environmental friendliness, and low price. However, the application of COFs also encountered many problems, such as poor electronic conductivity due to the large band gap. Moreover, in some three-dimensional (3D) COFs and stacked two-dimensional (2D) COFs, the huge crystal structure, aligned ultralong channels, and numerous crystal defects usually impede ion transport, and the large molecular weights of COFs generally decrease the specific capacities. These issues are urgently needed to be solved. Here in this review, we summarize the latest progress, core challenges and coping strategies concerning with the use of COFs in alkali-metal ion batteries, discuss the impact of material structure on energy storage, and propose strategies for the construction of high-performance COF-based electrodes.

Rapid and selective uranium extraction from aqueous solution under visible light in the absence of solid photocatalyst

Abstract: Extraction of uranium from radioactive waste-water is of significant importance for environmental protection and the recovery of uranium resource. Different from the previous reports to use the solid absorbent/photocatalyst for U(VI) removal, herein, we proposed a new eco-friendly method for the rapid and selective extraction of uranium from aqueous solutions under visible light without solid materials. At optimal pH value and in the presence of organics like alcohols, the U(VI) could be extracted efficiently to form brown uranium solid over wide uranium concentrations under anaerobic condition and visible light, by utilizing the excitation of the given U(VI) species. With comprehensive modelling of the electronic ultraviolet-visible (UV-Vis) properties, it is proved that pH adjusting towards U(VI) could induce efficient ligand-to-metal-charge-transfer (LMCT) within the uranyl complex under visible light and the reduction of U(VI) to form U(V), which can be transformed into U(IV) via disproportionation reaction. The resulting U(IV) in solid phase makes the extraction much more convenient in operation. More importantly, the excellent selectivity for uranium extraction over interfering alkali metal ions, transition metal ions and the lanthanide metal ions shows a powerful application potential.

15.4% Efficiency all-polymer solar cells

Abstract: We report all-polymer solar cells (All-PSCs) with record-high power conversion efficiency (PCE) through tuning the molecular weights of the polymer donor (PBDB-T) to form optimal active layer morphology. By combining the polymer donors with a newly reported polymer acceptor (PJ1), an unprecedented high PCE of 15.4% and fill factor over 75% were achieved for the All-PSCs with the medium molecular weight polymer donor (PBDB-TMW), which is the highest value for All-PSCs reported so far. Detailed morphology investigation revealed that the proper phase separation in the PBDB-TMW:PJ1 blend should account for the superior device performance as PBDB-TMW exhibits appropriate miscibility with the polymer acceptor PJ1. These results demonstrated that the device performance of All-PSCs could be fully comparable to that of small molecular acceptor-based PSCs. The formation of optimized morphology via precise control of molecular weights of polymer donors and acceptors is crucial to achieve this goal.

Highly sensitive, sub-microsecond polymer photodetectors for blood oxygen saturation testing

Abstract: Bottom surface of active layers and interface of indium tin oxide (ITO) electrodes and active layers play a crucial role in determining the performance of polymer photodetectors with photomultiplication (PM-PPDs). The interfacial trapped electron distribution closing to ITO electrodes will determine spectral response range and external quantum efficiency (EQE) of PMPPDs. The bottom interface is more sensitive than top interface when light is coming from the ITO side, and the larger density of generated charge on the bottom interfaces will induce interfacial band more bending for efficient charge tunneling injection. Highly sensitive and sub-microsecond PM-PPDs are achieved with PMBBDT:Y6 (100:7, w/w) as active layers under forward bias, yielding EQE of 18,700% at 320 nm, 21,700% at 600 nm and 16,400% at 810 nm under a bias of 7 V, respectively, as well as fast response time of 79 μs. The high EQE of the PM-PPDs is attributed to efficient hole tunneling injection from ITO electrode under forward bias. The electron traps closing to ITO electrode will be quickly filled up when light is coming from ITO side, leading to interfacial band more bending for hole tunneling injection. Importantly, the PM-PPDs is performed to measure heart rate (HR) and blood oxygen saturation (SpO2), and the measured data by the PM-PPDs are very similar with those obtained by commercial photodetectors.

N-heterocyclic carbene-catalyzed radical reactions

Abstract: While N-heterocyclic carbene (NHC) catalyzed electron-pair-transfer processes have been developed into an important tool for synthetically important bond formations during the past decades, the corresponding radical reactions via NHC catalysis have only received growing attention in the past six years. Taking into account the advantages NHC-catalyzed radical reactions might bring, such as creating new activation modes that were previously unobtainable, it is worthwhile to provide a conceptual understanding of this emerging area. Therefore, herein we give an overview of NHC-catalyzed radical reactions via different synthetic techniques.

Optically actuating ultra-stable radicals in a large π-conjugated ligand constructed photochromic complex

Abstract: Producing ultra-stabilized radicals via light irradiation has raised considerable concern but remains a tremendous challenge in functional materials. Herein, optically actuating ultra-stable radicals are discovered in a sterically encumbered and large π-conjugated tri(4-pyridyl)-1,3,5-triazine (TPT) ligands constructed photochromic compound Cu3(H-HEDP)2TPT2·2H2O ( QDU-12 ; HEDP=hydroxyethylidene diphosphonate). The photogeneration of TPT• radicals is the photoactive behavior of electron transfer from HEDP motifs to TPT units. The ultra-long-lived radicals are contributed from strong interchain π-π interactions between the large π-conjugated TPT components, with the radical lifetime maintained for about 18 months under ambient conditions. Moreover, the antiferromagnetic couplings between TPT• radicals and Cu2+ ions plummeted the demagnetization to 35% of its original state after light irradiation, showing the largest room temperature photodemagnetization in the current radical-based photochromic materials.

Promoting nitric oxide electroreduction to ammonia over electron-rich Cu modulated by Ru doping

Abstract: Electrocatalytic nitric oxide (NO) reduction is a promising strategy to produce ammonia. Developing a facile approach to synthesize efficient catalysts with enhanced NO electroreduction performance is highly desirable. Here, a series of Ru-doped Cu materials are constructed through in situ electroreduction of corresponding metal hydroxides. The optimized Ru0.05Cu0.95 exhibits superior electrocatalytic performance for ammonia synthesis by using NO/Ar (1/4, n/n) as the feedstocks (Faradaic efficiency: 64.9%, yield rate: 17.68 μmol cm−2 h−1), obviously outperforming Cu counterpart (Faradaic efficiency: 33.0%, yield rate: 5.73 μmol cm−2 h−1). Electrochemical in situ Fourier transform infrared (FTIR) spectroscopy and online differential electrochemical mass spectrometry (DEMS) are adopted to detect intermediates and unveil the possible reaction pathway. The downshift of the Cu d-band center induced by Ru doping facilitates the rate-limiting hydrogenation step and decreases the desorption energy of NH3, leading to high Faradaic efficiency and yield of ammonia.

C-F bond activation under transition-metal-free conditions

Abstract: The unique properties of fluorine-containing organic compounds make fluorine substitution attractive for the development of pharmaceuticals and various specialty materials, which have inspired the evolution of diverse C-F bond activation techniques. Although many advances have been made in functionalizations of activated C-F bonds utilizing transition metal complexes, there are fewer approaches available for nonactivated C-F bonds due to the difficulty in oxidative addition of transition metals to the inert C-F bonds. In this regard, using Lewis acid to abstract the fluoride and light/radical initiator to generate the radical intermediate have emerged as powerful tools for activating those inert C-F bonds. Meanwhile, these transition-metal-free processes are greener, economical, and for the pharmaceutical industry, without heavy metal residues. This review provides an overview of recent C-F bond activations and functionalizations under transition-metal-free conditions. The key mechanisms involved are demonstrated and discussed in detail. Finally, a brief discussion on the existing limitations of this field and our perspective are presented.

Rational design of a cationic polymer network towards record high uptake of 99TcO4− in nuclear waste

Abstract: 99Tc is a long-lived radionuclide present in large amounts as TcO4- anion in used nuclear fuel. Its removal from the waste stream is highly desirable because of its interference capability with actinide separation and its volatile nature during the nuclear waste vitrification process. Despite the progress achieved in the past few years, the design of anion-exchange materials with optimized Tc uptake property and improved stability under the extreme condition, is still a research goal beneficial for reducing the volume of secondary radioactive solid waste generated during the waste partitioning process. However, their design philosophy remains elusive, with challenges coming from charge repulsion, steric hindrance, and insufficient reactive sites within the materials. Herein, we present a design philosophy of cationic polymer network materials for TcO4- separation by systematic precursor screening and structure prediction. This affords an optimized material, SCU-CPN-2 (SCU=Soochow University), with extremely high positive charge density while maintaining high radiation resistance. SCU-CPN-2 exhibits a record high adsorption capacity (1,467 mg/g towards the surrogate ReO4-) compared to all anion-exchange materials reported up to date. In addition to ultrafast adsorption kinetics, SCU-CPN-2 has remarkable selectivity over nitrate and sulfate, and facile recyclability.

Photocatalytic decarboxylative alkylations of C(sp 3 )-H and C(sp 2 )-H bonds enabled by ammonium iodide in amide solvent

Abstract: A simple ammonium iodide salt in amide solvent catalyzes regioselective decarboxylative alkylation of C(sp3)-H bonds of N-aryl glycine derivatives, of C(sp2)-H bond of heteroarenes, and cascade radical addition to unsaturated bond followed by intramolecular addition to arene, with a broad scope of N-hydroxyphthalimide derived redox active esters under visible light irradiation. The reactions are suggested to proceed through photoactivation of a transiently assembled chromophore from electron-deficient phthalimide moiety and iodide anion through an anion-π interaction in solvent cage followed by diffusion to generate solvated free radical species to react with C-H substrates The simplicity, practicality, and broad substrate scope of this method highlight the synthetic power of photocatalysis through transiently assembled chromophore, and will hopefully inspire further developments of low cost photocatalysis based on various non-covalent interactions, which are prevalent in supramolecular chemistry and biosystems, for sustainable organic synthesis.

Conductive phthalocyanine-based metal-organic framework as a highly efficient electrocatalyst for carbon dioxide reduction reaction

Abstract: Porous crystalline metal-organic frameworks (MOFs) are one class of promising electrode materials for CO2 electroreduction reaction (CO2RR) by virtue of their large CO2 adsorption capacities and abundant tunable active sites, but their insulating nature usually leads to low current density. Herein, a two-dimensional (2D) Ni-phthalocyanine-based MOF (NiPc-Ni(NH)4) constructed by 2,3,9,10,16,17,23,24-octaaminophthalocyaninato nickel(II) (NiPc-(NH2)8) and nickel(II) ions attained high electrical conductivity due to the high overlap of d-π conjugation orbitals between the nickel node and the Ni-phthalocyanine-substituted o-phenylenediamine. During CO2RR, the NiPc-Ni(NH)4 nanosheets achieved a high CO Faradaic efficiency of 96.4% at −0.7 V and a large CO partial current density of 24.8 mA cm−2 at −1.1 V, which surpassed all the reported two-dimensional MOF electrocatalysts evaluated in an H-cell. The control experiments and density functional theory (DFT) calculations suggested that the Ni-N4 units of the phthalocyanine ring are the catalytic active sites. This work provides a new route to the design of highly efficient porous framework materials for the enhanced electrocatalysis via improving electrical conductivity.

Cystine proportion regulates fate of polypeptide nanogel as nanocarrier for chemotherapeutics

Abstract: The physicochemical characteristics of nanoparticles are closely related to their drug delivery performances in vitro and in vivo. A well-designed nanocarrier can prolong the drug half-life in the blood circulation, upregulate the drug accumulation at the target site, and enhance the treatment efficacy. To elucidate the impact of physicochemical properties on the fate of nanogel as a nanocarrier of chemotherapeutics, three methoxy poly(ethylene glycol)-poly(L-phenylalanine-co-L-cystine) (mPEG-P(LP-co-LC)) nanogels with different L-cystine proportions were developed, namely mPEG-P(LP10-co-LC5) (NG10-5), mPEG-P(LP10-co-LC10) (NG10-10), and mPEG-P(LP10-co-LC15) (NG10–15). The three nanogels shared similar surface charge and reduction-responsive behavior, but they had distinct diameters and different drug release profiles. Among them, NG10-5, which has the smallest diameter, was preferentially internalized by tumor cells in vitro and showed rapid migration to the tumor site in vivo. Using doxorubicin (DOX) as a model chemotherapeutic agent, NG10-5/DOX had the most prolonged blood circulation period and highest tumor accumulation after intravenous administration. NG10-5/DOX also had the most potent antitumor effect of all three drug-loaded nanogels. Accordingly, adjusting physicochemical characteristics by changing the amino acid composition might improve the therapeutic efficacies of nanogels and enhance their potential for clinical application.

Novel boron- and sulfur-doped polycyclic aromatic hydrocarbon as multiple resonance emitter for ultrapure blue thermally activated delayed fluorescence polymers

Abstract: Boron (B)- and sulfur (S)-doped polycyclic aromatic hydrocarbons (PAHs) are developed as a novel kind of multiple resonance emitters for ultrapure blue thermally activated delayed fluorescence (TADF) polymers with narrowband electroluminescence. The combination of electron-deficient B atom and electron-rich S atom in PAH can form an intramolecular push-pull electronic system in a rigid aromatic framework, leading to reduced singlet-triplet energy splitting and limited structure relaxation of excited states. The critical roles of S atom in determining emission properties with respect to the oxygen analogues are in two aspects: (i) reducing energy bandgap to shift emission from human-eye-insensitive ultraviolet zone to blue region, and (ii) promoting reverse intersystem crossing process by heavy-atom effect to activate TADF effect. The resulting polymer containing B,S-doped PAH as emitter and acridan as host exhibits efficient blue electroluminescence at 458 nm with small full-width at half-maximum of 31 nm, representing the first example for ultrapure TADF polymer with narrowband electroluminescence.

Engineering of dendritic dopant-free hole transport molecules: enabling ultrahigh fill factor in perovskite solar cells with optimized dendron construction

Abstract: Developing dopant-free hole-transporting materials (HTMs) for high-performance perovskite solar cells (PVSCs) has been a very active research topic in recent years since HTMs play a critical role in optimizing interfacial charge carrier kinetics and in turn determining device performance. Here, a novel dendritic engineering strategy is first utilized to design HTMs with a D-A type molecular framework, and diphenylamine and/or carbazole is selected as the building block for constructing dendrons. All HTMs show good thermal stability and excellent film morphology, and the key optoelectronic properties could be fine-tuned by varying the dendron structure. Among them, MPA-Cz-BTI and MCz-Cz-BTI exhibit an improved interfacial contact with the perovskite active layer, and non-radiative recombination loss and charge transport loss can be effectively suppressed. Consequently, high power conversion efficiencies (PCEs) of 20.8% and 21.35% are achieved for MPA-Cz-BTI and MCz-Cz-BTI based devices, respectively, accompanied by excellent long-term storage stability. More encouragingly, ultrahigh fill factors of 85.2% and 83.5% are recorded for both devices, which are among the highest values reported to date. This work demonstrates the great potential of dendritic materials as a new type of dopant-free HTMs for high-performance PVSCs with excellent FF.

Leaf-inspired design of mesoporous Sb2S3/N-doped Ti3C2Tx composite towards fast sodium storage

Abstract: Owing to excellent conductivity and abundant surface terminals, MXene-based heterostructures have been intensively investigated as energy storage materials. However, elaborate design of the structure and composition of MXene-based hybrids towards superior electrochemical performance is still challenging. Herein, we present an ingenious leaf-inspired design for preparing a unique Sb2S3/nitrogen-doped Ti3C2Tx MXene (L-Sb2S3/Ti3C2) hybrid. In-situ TEM observations reveal that the leaflike Sb2S3 nanoparticles with numerous mesopores can well relieve the large volume changes via an inward pore filling mechanism with only 20% outward expansion, whereas highly conductive N-doped Ti3C2Tx nanosheets can serve as the robust mechanical support to reinforce the structural integrity of the hybrid. Benefiting from the structural and constituent merits, the L-Sb2S3/Ti3C2 anode fabricated exhibits a fast sodium storage behavior in terms of outstanding rate capability (339.5 mA h g−1 at 2,000 mA g−1) and high reversible capacity at high current density (358.2 mA h g−1 at 1,000 mA g−1 after 100 cycles). Electrochemical kinetic tests and theoretical simulation further manifest that the boosted electrochemical performance mainly arises from such a unique leaf-like Sb2S3 mesoporous nanostructure with abundant active sites, and enhanced Na+ adsorption energy on the heterojunction formed between Sb2S3 nanoparticles and Ti3C2 matrix.

SbVO 4 based high capacity potassium anode: a combination of conversion and alloying reactions

Abstract: As the key to optimizing potassium ion batteries’ (PIBs) performance, the development of high capacity potassium anode is the footstone. Here, through a one-step solvothermal method, uniformly dispersed SbVO4 nanoparticles on the reduced graphene oxide nanosheets (SbVO4@RGO) were synthesized and used as PIBs anodes. SbVO4@RGO anode shows high capacity due to alloying and conversion reactions occur simultaneously in the cyclic process. The anode delivers a capacity as high as 447.9 mAh g−1 at 100 mA g−1. Besides, a cycling life of 500 cycles with small average capacity decay rate (only 0.106% per cycle) is also revealed. It was found in the initial discharge process, SbVO4 transforms into Sb and K3VO4. And in the following cycle Sb and K3VO4 simultaneously react with K+ via the alloying/de-alloying and conversion reaction, respectively. The present study of SbVO4@RGO may provide insight for high performance alloying-based/conversion-based potassium anodes.

High-performance all-polymer solar cells enabled by a novel low bandgap non-fully conjugated polymer acceptor

Abstract: The non-fully conjugated polymer as a new class of acceptor materials has shown some advantages over its small molecular counterpart when used in photoactive layers for all-polymer solar cells (all-PSCs), despite a low power conversion efficiency (PCE) caused by its narrow absorption spectra. Herein, a novel non-fully conjugated polymer acceptor PFY-2TS with a low bandgap of ~1.40 eV was developed, via polymerizing a large π-fused small molecule acceptor (SMA) building block (namely YBO) with a non-conjugated thioalkyl linkage. Compared with its precursor YBO, PFY-2TS retains a similar low bandgap but a higher LUMO level. Moreover, compared with the structural analog of YBO-based fully conjugated polymer acceptor PFY-DTC, PFY-2TS shows a similar absorption spectrum and electron mobility, but significantly different molecular crystallinity and aggregation properties, which results in optimal blend morphology with a polymer donor PBDB-T and physical processes of the device in all-PSCs. As a result, PFY-2TS-based all-PSCs achieved a PCE of 12.31% with a small energy loss of 0.56 eV enabled by the reduced non-radiative energy loss (0.24 eV), which is better than that of 11.08% for the PFY-DTC-based ones. Our work clearly demonstrated that non-fully conjugated polymers as a new class of acceptor materials are very promising for the development of high-performance all-PSCs.

Dual-atom catalysts: controllable synthesis and electrocatalytic applications

Abstract: Electrocatalysis, as the nexus for energy storage and environmental remediation, requires developing low-cost and high-performing heterogeneous catalysts. Compared with the single atom catalysts (SACs), dual-atom catalysts (DACs) are attracting ever-increasing interest due to their higher metal loading, more versatile active sites and unique reactivity. However, controlled synthesis of DACs remains a great challenge, and their electrocatalytic applications are still in infancy. This review first discusses the synthesis of DACs by highlighting several synthetic strategies. Subsequently, we exemplify the unique reactivities of DACs in electrocatalytic applications including water splitting, oxygen reduction, carbon dioxide reduction and nitrogen reduction. The structure-activity relations of DACs are specifically discussed in comparison with that of SACs, on the basis of experimental and theoretical studies. Finally, the opportunities and challenges of DACs are summarized in terms of rational design, controlled synthesis, characterization, and applications.

Ultralong organic room-temperature phosphorescence of electron-donating and commercially available host and guest molecules through efficient Förster resonance energy transfer

Abstract: Ultralong organic room-temperature phosphorescence (RTP) materials have attracted tremendous attention recently due to their diverse applications Several ultralong organic RTP materials mimicking the host-guest architecture of inorganic systems have been exploited successfully However, complicated synthesis and high expenditure are still inevitable in these studies Herein, we develop a series of novel host-guest organic phosphorescence systems, in which all luminophores are electron-rich, commercially available and halogen-atom-free The maximum phosphorescence efficiency and the longest lifetime could reach 236% and 362 ms, respectively Experimental results and theoretical calculation indicate that the host molecules not only play a vital role in providing a rigid environment to suppress non-radiative decay of the guest, but also show a synergistic effect to the guest through Forster resonance energy transfer (FRET) The commercial availability, facile preparation and unique properties also make these new host-guest materials an excellent candidate for the anti-counterfeiting application This work will inspire researchers to develop new RTP systems with different wavelengths from commercially available luminophores

Pillararene-based supramolecular systems for theranostics and bioapplications

Abstract: As an emerging type of important macrocycles for supramolecular chemistry, pillararenes and their derivatives have been widely studied and applied in numerous fields, which intensively promotes the development of chemistry, materials science and biology. Pillararene-based theranostic systems are of special interest in the biological and medical areas as they have shown very promising results. Owing to easy preparation, reliable guest affinity, good biocompatibility and stability, pillararenes are frequently used to construct functional biomaterials. On one hand, pillararenes can either be used individually or form diversiform self-assemblies such as micelles, nanoparticles and vesicles to increase water solubility and biocompatibility of drugs. On the other hand, it is promising to modify solid materials like framework materials, silica nanoparticles and graphene oxides with pillararene derivatives to enhance their functions and controllability. In this review, we summarize recent endeavors of pillararene-based supramolecular systems with theranostics and other biological applications comprising drug delivery/chemotherapy, photodynamic/photothermal therapy, antimicrobials, bioimaging, etc . By introducing several typical examples, the design principles, preparation strategies, identifications and bio-applications of these pillararene-based supramolecular systems are described. Future challenges and directions of this field are also outlined.

Late-stage azolation of benzylic C‒H bonds enabled by electrooxidation

Abstract: The installation of azoles via C–H/N–H cross-coupling is significantly underdeveloped, particularly in benzylic C–H azolation due to the requirement for external chemical oxidants and the challenge in controlling the site- and chemo-selectivity. Herein, a late-stage azolation of benzylic C‒H bonds enabled by electrooxidation is described, which proceeds in an undivided cell under mild, catalyst- and chemical-oxidant-free reaction conditions. The strategy empowers the C‒H azolation on primary, secondary, and even challenging tertiary benzylic positions selectively. The remarkable synthetic utility of our approach is highlighted by its easy scalability without overoxidation of products and ample scope with valuable functional groups. The approach can be directly used to install benzyl and azole motifs on highly functionalized drug molecules.

Construction of CoS2 nanoparticles embedded in well-structured carbon nanocubes for high-performance potassium-ion half/full batteries

Abstract: Metal sulfides have been widely investigated as promising electrode materials for potassium-ion batteries (PIBs) due to their high theoretical capacities. However, the practical application of metal sulfides in PIBs is still hindered by their intrinsic shortcomings of low conductivity and severe volume changes during the potassiation/depotassiation process. Herein, a simple template-based two-step annealing strategy is proposed to impregnate CoS2 nanoparticles in the well-structured carbon nanocubes (denoted CoS2/CNCs) as an advanced anode material for PIBs. The ex-situ XRD measurements reveal the K+ storage mechanism in CoS2/CNCs. Benefiting from the unique structures, including abundant active interfacial sites, high electronic conductivity, and significantly alleviated volume variation, CoS2/CNCs present a high specific capacity (537.3 mAh g−1 at 0.1 A g−1), good cycling stability (322.4 mAh g−1 at 0.5 A g−1 after 300 cycles), and excellent rate capability (153.1 mAh g−1 at 5 A g−1). Moreover, the obtained nanocomposite shows superior potassium storage properties in K-ion full cells when it is coupled with a KVPO4F cathode.

Donor-acceptor 2D covalent organic frameworks for efficient heterogeneous photocatalytic α-oxyamination

Abstract: Covalent organic frameworks (COFs) have received widespread interest due to their high porosity, excellent crystallinity, tailorable structures, and broad application prospects. It has been demonstrated that proper combination and arrangement of electron donor and acceptor units in 2D conjugated COF lattice could promote efficient charge separation and electron transfer, and thus is beneficial for photocatalysis. In this article, three donor-acceptor (D-A) 2D COFs were prepared by Schiff base reaction of electron acceptor 4,4′,4″,4‴-(benzo[1,2-d:4,5-d′]bis(oxazole)-2,4,6,8-tetrayl)tetraaniline (BBO) with different electron donors: thieno[3,2-b]thiophene-2,5-dicarbaldehyde (TT), benzo[1,2-b:4,5-b′]dithiophene-2,6-dicarboxaldehyde (BDT) and terephthalaldehyde (Ph), respectively. These D-A 2D COFs exhibited prominent photocatalytic activity towards α-oxyamination of 1,3-dicarbonyl with 2,2,6,6-tetramethyl-1-piperdinyloxy (TEMPO) upon visible light irradiation. Among these D-ABBO-COFs, DTT-ABBO-COF exhibited the highest photocatalytic rates, which can be ascribed to the more negative highest occupied molecular orbital (HOMO) and narrower bandgap. The excellent stability, high activity and superior recyclability render DTT-ABBO-COF as a potential and environmentally friendly heterogeneous catalyst for α-oxyamination.

Tunable room-temperature phosphorescence and circularly polarized luminescence encoding helical supramolecular polymer

Abstract: Supramolecular polymers with different functionalities have been continuously developed in the past decade because of their indispensable role in soft materials. However, pure organic supramolecular polymers with stable room temperature phosphorescence (RTP) emission were very rarely reported for the difficulties of synthesis and achieving RTP in solution. Herein, soluble helical supramolecular polymers with circularly polarized room-temperature phosphorescence were developed via a facile host-guest strategy. Through assembly, a transition from pure fluorescence to almost pure RTP emission was achieved. Adjusting the asymmetry of guest could easily control the chiroptical property of supramolecular polymers. This work provides new opportunities for the design and development of intelligent soft functional soft materials.