Latest ArticlesExciton behavior is crucial to the exploitation of light-emitting conjugated polymer (LCPs) for optoelectronic devices. Singlet excitons are easily trapped by the intrinsically defect structures. Herein, we set a polyfluorenol (PPFOH) as an example to systematically investigate its photophysical behavior to check the role of defect structures in LCPs. According to time-resolved photoluminescence analysis, the feature emission peaks from individual chain of PPFOH in diluted DMF solution is effectively avoided the influence of fluorenone formation, but the residual green-band emission at 550 nm is easily observed in the PL spectra of PPFOH dilute toluene solution obtained delay 1.5 ns, confirmed the formation of "guest" physical aggregation-induced defect structure. Remarkably, efficient and ultrafast energy transfer from individual chain to defect structure is observed in PPFOH films. Interestingly, the efficient energy transfer happened for the film obtained from DMF solution (200 ps) than those of toluene ones (600 ps). Meanwhile, compared to relatively stable green-band emission in PPFOH film from toluene solution, red-shifted emission peak (11 nm) of PPFOH film from DMF solutions exposed to saturated DNT vapor also confirmed their different aggregation-induced green-band emission. Therefore, this aggregation defect structures are influenced on the photophysical property of LCPs in solid states.
As an emerging star in the family of two-dimensional (2D) materials, 2D transition metal carbides, carbonitrides and nitrides, collectively referred to as MXenes, have large specific surface area, rich active sites, metallic conductivity and adjustable surface chemical properties. These features make MXenes promising candidates for gas-sensing materials. For the past few years, MXene-based sensors have drawn increasing attention due to their enhanced sensor performance. Based on this, this review systematically represents the structure, synthesis methods and properties of MXenes, and summarizes their applications in gas sensors. Firstly, the types, structure, main synthesis methods and properties of MXenes are introduced in a comprehensive way. Next, the corresponding design principle and working mechanism of MXene-based gas sensor are clarified. Subsequently, the sensing performances of pristine MXenes and the MXene-based nanocomposite are discussed. Finally, some future opportunities and challenges of MXene-based sensors are pointed out.
In this work, semirigid linkers of the alkyl-thiophene-alkyl structure are developed to construct double-cable polymers. Three alkyl units, propyl (C3H6), hexyl (C6H12), and dodecyl (C12H24), are applied as semirigid linkers, yielding three double-cable polymers: PBC6-T, PBC12-T, and PBC24-T, respectively. PBC12-T which uses C6H12-thiophene-C6H12 linkers is found to exhibit the best device efficiency of 5.56%, while PBC6-T and PBC24-T with shorter or longer linkers yield device efficiencies of only 2.65% and 1.09% in single-component organic solar cells (SCOSCs). Further studies reveal that PBC12-T exhibits higher crystallinity and improved charge transport, resulting in better efficiencies. Our work provides an approach to construct double-cable conjugated polymers with long alkyl linkers, and it shows the importance of the linker length for the photovoltaic performance of SCOSCs.
The scope of stereochemistry recognition usually occurs near the chiral scaffold of a ligand or catalyst. Remote stereocontrol, which can surpass the limits of stereorecognition of remote prochiral centers, has long been a challenging object of great interest in asymmetric catalysis. The current work realized the remote stereocontrol of 1,7-zwitterion intermediates formed from Huang's o-amino aryl MBH carbonates. With simple and easily accessible β-ICD as the bifunctional catalyst, multifunctionalized tetrahydroquinoline derivatives could be synthesized via (4 + 2) cycloadditions with excellent enantioselectivity and diastereoselectivity under mild conditions. The strategy possesses broad substrate scope, and three types of electron-deficient enones are successfully applied. Mechanistic studies disclosed the Lewis base-catalyzed reaction pathway, and H-bonding between the catalyst and enones is crucial for long-range stereocontrol. Scale-up reaction and transformations of the tetrahydroquinoline products demonstrated the potential of this strategy.
A method for the generation of alkyl radicals from inert alkyl C-O bonds has been developed via an iron/borane reagent/alkoxide catalytic system, which can be employed for the synthesis of amines from nitroarenes with excellent efficiency. Preliminary mechanistic studies reveal that the amine synthesis may be involving a single electron transfer pathway to form alkyl radicals, and the low-valent iron species may be the active intermediates.
Photodynamic therapy (PDT) is a clinically approved cancer treatment that uses energy of light to generate active substances that cause damage to the cancer. Photosensitizers are employed to absorb light and generate toxic reactive oxygen species (ROS) to damage biomolecules like DNA. At the same time, some chemotherapy drugs like nucleotide analogues can provide mechanism-guided promotion in the treatment efficacy of PDT. However, the photosensitizer and chemotherapy drugs used in PDT is usually organic molecules, which suffers from bad solubility, fast clearance, and acute toxicity. To achieve targeted treatment, a reasonable delivery system is necessary. Therefore, we reported a metal-phenolic network where IR780 and gemcitabine were coupled chemically to overcome these shortcomings. The enhanced PDT effects can be realized by the promoted cell death both in vitro and in vivo. Moreover, the synergistic therapy also induced T-cell mediated anti-tumor immune response, which was significant for the inhibition of distant tumor growth. This work expanded the biomedical application of metal-phenolic materials and contribute to the wider application of photodynamic cancer therapy.
Metal-organic frameworks (MOFs) with inherent porosity and suspended acidic groups are promising proton conducting materials in water or aqua-ammonia media. Herein we report a new lanthanide phosphonate, namely, Dy2(amp2H2)2(mal)(H2O)2·5H2O (MDAF-6). It possesses a 3D open-framework structure, and shows a high NH3 adsorption capacity of 142.4 cm3/g at P/P0 = 0.98 at 298 K due to acid-base interaction. Interestingly, the proton conductivity of MDAF-6-NH3 is enhanced by five orders of magnitude compared to MDAF-6 after 8.5 h exposure in saturated NH3-H2O vapor, indicating the importance of coexistent conjugate acid-base pairs of H3O+-H2O and NH4+-NH3 in promoting proton conduction. Magnetic studies of MDAF-6 revealed slow magnetization relaxation under zero dc field, characteristic of single-molecule magnet behavior. This work provides not only a new multifunctional MOF material, but also a new strategy to improve proton conduction in aqua-ammonia medium.
Mitochondrial damage is closely related to the occurrence of many diseases. However, accurate monitoring and reporting of mitochondrial damage are not easy. Here, we developed a small molecule fluorescent probe named CB-Cl, which has splendid spectral properties (large Stokes shift, strong affinity for RNA, etc.) and excellent targeting ability to intracellular mitochondria. After mitochondria were damaged by external stimuli, CB-Cl would light up the nucleolus as a signal reporter. The cascade imaging of mitochondria and nucleolus using CB-Cl can monitor and visualize the mitochondrial status in living cells in real-time. Based on the above advantages, the probe CB-Cl has reference significance for the related research of mitochondrial damage and the prevention and treatment of related diseases.
A dimesitylboryl-ended oligothiophene with tetrazine as core (BTz) was synthesized and its reactivity and spectral changes toward trans-cyclooctene ((4E)-TCO-OH), cis-cyclooctene and bicyclo[6.1.0]non-4-yn-9-ylmethanol were comprehensively studied. The fluorescence intensity of BTz was enhanced up to more than 100 times upon bioorthogonal reaction with (4E)-TCO-OH. In addition, the first crystal structure of isolated product of tetrazine derivative with cyclooctene was determined, which clearly confirmed a dehydrogenation occurred after Diels–Alder reaction under ambient conditions.
Polycyclic aromatic hydrocarbons (PAHs) play an important role in the industry, and the development of new materials for the selective separation of PAHs is of great significance. In this work, we report a hexahedral metal-organic cage with low symmetry by subcomponent self-assembly. In this cage, the eight ZnⅡ centers adopt an interesting ΛΛ/ΔΔΔΔΔΔ or ΛΛΛΛΛΛ/ΔΔ configuration. This cage with a cavity volume of 520 Å3 can bind anthracene, phenanthrene, and pyrene to form 1:1 host-guest complexes, while the bigger triphenylene, chrysene, perylene, and coronene cannot be encapsulated. The binding constant Ka of pyrene is about 1.110 × 103 (mol/L)−1, which is more than an order of magnitude larger than that of anthracene and phenanthrene (111 (mol/L)−1, 277 (mol/L)−1, respectively). X-ray structure studies reveal that the pyrene is located in the cavity and stabilized by multiple CH⋅⋅⋅π interactions. After separation from a mixture of PAHs, pyrene with > 96.1% purity can be obtained. This work provides a useful method for the first time for the selective separation of pyrene from PAHs mixture by utilizing a metal-organic cage as the material, making it a useful tool for purifying and separating specific compounds from complex mixtures.
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