Latest ArticlesAs one of the 2D transition metal sulfides, 1T phase MoS2 nanosheets (NSs) have been studied because of their distinguished conductivity and suitable electronic structure. Nevertheless, the active sites are limited to a small number of edge sites only, while the basal plane is catalytically inert. Herein, we report that boron (B) doped 1T phase MoS2 NSs can replace precious metals as a co-catalyst to assist in photocatalytic H2 production of 2D layered g-C3N4 nanosheets (g-C3N4 NSs). The H2 evolution rate of prepared B-MoS2@g-C3N4 composites with 15 wt% B-MoS2 (B-MoS2@g-C3N4–15, 1612.75 µmol h−1 g−1) is 52.33 times of pure g-C3N4 NSs (30.82 µmol h−1 g−1). Furthermore, the apparent quantum efficiency (AQE) of B-MoS2@g-C3N4–15 composites under the light at λ = 370 nm is calculated and reaches 5.54%. The excellent photocatalytic performance of B-MoS2@g-C3N4–15 composites is attributed to the B ions doping inducing the distortion of 1T phase MoS2 crystal, which can activate more base planes to offer more active sites for H2 evolution reaction (HER). This work of B-MoS2@g-C3N4 composites offers experience in the progress of effective and low-price photocatalysts for HER.
The synthesis methods of α-fluoro-arylketones were well-established through electrophilic/nucleophilic fluorination and transition metal catalyzed cross-coupling. However, due to the site selectivity and substrate restriction, only a few cases have been developed to afford α-alkyl-α-fluoro-alkylketones. Herein, we report a general and efficient method of preparing diverse α-alkyl-α-fluoro-alkylketones via nickel-catalyzed reductive coupling reaction of monofluoroalkyl triflates with low-cost industrial raw material alkyl carboxylic acids. These transformations demonstrate high efficiency, mild conditions, and excellent functional group compatibility. This strategy provides a general and efficient method for the synthesis of α-alkyl-α-fluoro-alkylketones.
Benefitting from the tunable heterogeneous interface and electronic interaction, metal-polymer-based hybrid composites have attracted wide attention. It is highly desired to develop advanced synthesis methodology and understand the structure-performance relationship. Herein, with the aniline oligomer as the key enabler, we resolve the inferior dynamics issue in the Ag+-aniline reaction system, and successfully fabricate a sub-micron anisotropic eccentric Ag@polyaniline (PANI) particle (an average size up to 340 nm) at room temperature. We demonstrate the synergy mechanism of polyvinyl pyrrolidone and in-situ generated PANI for modifying the dynamic reaction interface. We further clarify the H+ concentration and the surfactant types serve as main descriptors to tune the reaction dynamics. Besides, by applying other aniline oligomers, a series of similar eccentric structures can also be obtained, indicative of the good applicability of our strategy. Such a sub-micron eccentric structure furnishes the Ag@PANI composites with sound performance for microwave absorption, as demonstrated by a minimum reflection loss (RL) value of −35 dB with an effective absorption bandwidth of 3.7 GHz. This study provides an inspiring scope/concept of eccentric microstructure engineering for better meeting the demands in the high-tech military, energy, environment fields, and beyond.
Inosine is a vital RNA modification across three kingdoms of life. It has been demonstrated that inosine plays important roles in modulation of the fate of RNAs. In the current study, we developed a highly sensitive method to determine inosine in a single cell by N-cyclohexyl-N'-β-(4-methylmorpholinium)ethylcarbodiimide p-toluenesulfonate (CMCT) derivatization in combination with mass spectrometry analysis. The results showed that the detection sensitivity of inosine was increased by 556-fold after CMCT derivatization, with the limit of detection (LOD) being 4.5 amol. With the established method, we could detect inosine from 13.0 pg of total RNA of HEK293T cells. Meanwhile, inosine in RNA from a single cell could also be clearly detected due to the improved detection sensitivity. Moreover, we found the level of inosine in RNA of sleep-deprived mice was significantly increased compared to the control mice, indicating that inosine is associated with sleep behavior and might be a potential indicator of sleep disorder. Taken together, the chemical derivatization coupled with mass spectrometry analysis offers a valuable tool in determination of endogenous RNA modifications in a single cell, which should benefit the functional study of RNA modification in rare clinical samples.
Heme responsible for the dioxygen fixation, transport and conversion is a metalloporphyrin complex highly dependent on its diverse geometry of ligand. In this work, a trans-ortho-di-strapped zinc porphyrin with dome-like deformation was synthesized by thermodynamically controlling the formation of trans-precursor of porphyrinogen. Its single-crystal structure demonstrated that the asymmetric treatment of porphyrin achieves three goals of creating two secondary coordination sphere (SCS) bulks, maintaining a unique dome deformation, and making atomic out-of-plane deviation. In this way, this metallic complex integrates at least three key features of the pocket structure, the differentiated axial ligations, and the ring distortion, making it an ideal heme analog.
Base pair mismatch has been regarded as the main source of DNA point mutations, where minor short-lived tautomers were usually involved. However, the detection and characterization of these unnatural species pose challenges to existing techniques. Here, by using systematic structural and ultrafast resonance Raman (RR) spectral analysis for the four possible conformers of guanine-cytosine base pairs, the prominent marker Raman bands were identified. We found that the hydrogen bonding vibrational region from 2300 cm−1 to 3700 cm−1 is ideal for the identification of these short live species. The marker bands provide direct evidence for the existence of the tautomer species, thus offering an effective strategy to detect the short-lived minor species. Ultrafast resonance Raman spectroscopy would be a powerful tool to provide direct evidence of critical dynamical details of complex systems involving protonation or tautomerization.
Covalent organic frameworks (COFs) are promising crystalline materials for the light-driven hydrogen evolution reaction (HER) due to their tunable chemical structures and energy band gaps. However, deeply understanding corresponding mechanism is still challenging due to the multiple components and complicated electron transfer and reduction paths involved in photocatalytic HER. Here, the photocatalytic HER investigation has been reported based on three COFs catalysts, 1–3, which are prepared by benzo[1, 2-b: 3, 4-b': 5, 6-b']trithiophene-2, 5, 8-trialdehyde to react with C3 symmetric triamines including tris(4-aminophenyl)amine, 1, 3, 5-tris(4-aminophenyl)benzene, and (1, 3, 5-tris-(4-aminophenyl)triazine, respectively. As the isostructural hexagonal honeycomb-type COF of 2 and 3 reported previously, the crystal structure of 1 has been carefully correlated through the powder X-ray diffraction study with the help of theoretical simulations. 1 shows highly porous framework with Brunauer-Emmett-Teller surface area of 1249 m2/g. Moreover, the introduction of ascorbic acid into the photocatalytic system of COFs achieves the hydrogen evolution rate of 3.75, 12.16 and 20.2 mmol g–1 h–1 for 1–3, respectively. The important role of ascorbic acid in photocatalysis of HER is disclosed to protonate the imine linkages of these COFs, leading to the obvious absorbance red-shift and the improved charge separation efficiency together with reduced resistance in contrast to pristine materials according to the spectroscopic and electronic characterizations. These innovations of chemical and physical properties for these COFs are responsible for their excellent photocatalytic performance. These results elucidate that tiny modifications of COFs structures is able to greatly tune their band structures as well as catalytic properties, therefore providing an available approach for optimizing COFs functionalities.
With the rapid development of economy, industrial and agricultural pollutants have caused great damage to the ecological environment and the normal development of organisms, posing a serious threat to global public health. Therefore, rapid and sensitive detection of pollutants is very important for environmental safety and people’s health. A stable multi-response fluorescence sensor (RhB@1) with dual emission characteristics was constructed by embedding RhB guest molecules in Zn-MOF using a simple one-pot method. XRD, IR, XPS, Raman and other characterization methods were used to demonstrate the formation of composite materials. The sensor has two fluorescence emission peaks at 415 nm and 575 nm under the excitation of 316 nm. It has high sensitivity and low detection limit (7.94 and 7.82 nmol/L, respectively) in the detection of fluazinam (FLU) and Fe3+. The mechanism of fluorescence quenching may be due to the synergistic effect of IFE and PET. Outstandingly, when ascorbate acid (AA) was added to the quenching system of Fe3+ and RhB@1, its fluorescence gradually recovered, forming the unique “on-off-on” sensor. Therefore, RhB@1 has a fast fluorescence response and good stability, making it potentially useful in practical application and biosensors. More significantly, using Fe3+ and AA as chemical input signals, a binary intelligent logic gate device has been developed based on the “on-off-on” response mode of RhB@1, which extends the application of logic gate switching devices in the chemical field. In addition, a visual portable test paper with good selectivity and high sensitivity was developed, which can be used for rapid detection of FLU, showing its broad application prospect.
Dry eye disease (DED) is a multifactorial chronic inflammatory disease of the ocular surface with complex and unclear etiology. The development of reliable detection tools for the pathology of DED will benefit its treatment, but it is still lacking. In parallel, it has been discovered recently that viscosity changes are involved in inflammation processes. In this regard, we constructed a fluorescent probe V5 with an asymmetric donor-acceptor-donor (D-A-D) feature after rational structural modulation for viscosity detection during DED progression. The probe manifested a remarkable fluorescence enhancement (110 folds) in highly viscous conditions without interferences from polarity and reactive species. Specifically, no aggregation effect of the probe was found in glycerol. Moreover, viscosity increment in human corneal epithelial cells (HCECs) induced by hyperosmosis and inflammation was monitored, and ferroptosis in HCECs also led to the viscosity elevation. A reactive oxygen species (ROS)-dependent viscosity changes during DED progression is demonstrated. Finally, viscosity change in corneal epithelial cell layer from mice treated by scopolamine was also visualized for the first time. We anticipate this work can provide a new lens to the pathogenesis study and diagnosis of DED and other ophthalmic diseases using fluorescence methods.
Compartmentalization in the biological world brings excellent efficiency and specificity to the formation of complex compounds, inspiring supramolecular chemists to continuously search for defined spaces that can mimic such natural binding sites. Bowl-shaped cavitands built up from resorcinarenes (RA) present rigid and preorganized concave surfaces, which are capable of mimicking the molecular recognition properties of enzymes. The versatile scaffold of RA endows the cavitand with terrific variety and excellent binding behavior. This review provides a comprehensive overview over the structural modification to date in the high attention field of RA-based cavitands development. Different strategies for synthesizing diverse cavitands, such as small cavity cavitands, wider cavity cavitands, deep cavity cavitands, biscavitands, and asymmetric cavitands, are discussed in details. Furthermore, insights into their applications including catalysis, separations and sensing are provided.
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