Latest ArticlesIt is highly desired to accurately and selectively detect and image intracellular L-lysine and pH in biological systems because they could act as the biomarkers in certain abnormal conditions and may give us a warning of the occurrence of diseases. It has been attracted more focuses to design new ratiometric fluorescent probe for monitoring L-lysine and pH to improve detection accuracy. Carbonized polymer dots (CPDs), which possess carbon/polymer hybrid structure rather than pure carbon structure and constitute of a carbon core and large amounts of functional groups/polymer chains on the surface, rise up as a new type of fluorescent nanomaterials and especially display many advantages for bioanalysis. In this study, o-phenylenediamine (o-PD) and poly(styrene-co-maleic anhydride) (PSMA) are used as the precursors to synthesize the desired CPDs through one-step hydrothermal amide method. The prepared CPDs display two well-resolved fluorescence emission bands, i.e., a very weak emission centered at 470 nm in blue region and a strong emission centered at 558 nm in yellow region. It is found that the two emissions are both responsive to L-lysine based on the surface passivation mechanism, whereas, only the yellow emission is responsive to pH due to the protonation/deprotonation process of the amino groups. Based on the different responsive behaviors, ratiometric detection and imaging of L-lysine and pH are achieved. The prepared ratiometric CPDs probe is successfully applied for L-lysine and pH sensing and imaging at two emission channels in live cell and zebrafish with satisfactory results.
Exploring highly efficient and non-noble-metal-based electrocatalysts for oxygen evolution reaction (OER) is of great importance not only for water splitting but also for rechargeable metal-air batteries and fuel cells. Herein, we describe a simple strategy to prepare hierarchical Ni@Mn-doped NiO hybrids using flower-like Ni-Mn layered double hydroxides (NiMn-LDHs) as a precursor. After calcination at 400 ℃ for an hour under N2 atmosphere, the flower-like NiMn-LDHs transform to porous microspheres consisting of nanoparticles, in which Ni cores are encapsulated by Mn-doped NiO shells (denoted as Ni@Mn-NiO-400). Benefiting to this unique porous, core-shell structures and element doping, the as-prepared Ni@Mn-NiO-400 hybrid shows a low overpotential of 178 mV at the current density of 10 mA/cm2 and Tafel slope of 52.7 mV/dec in 1 mol/L KOH solution. More significantly, the Ni@Mn-NiO-400 hybrid also demonstrates superior stability of 98.6% after 50 h continuously testing, much higher than pristine NiMn-LDHs and commercial IrO2 catalyst. In addition, theoretical simulation shows that Ni core and Mn doping greatly affect the electronic states and electronic structure of NiO. As a result, Ni@Mn-doped NiO hybrid possesses an optimal adsorption activity towards oxygen species than NiO and undoped Ni@NiO hybrid. Considering the compositional and structural flexibility of LDHs, this work may offer a simple method to prepare other non-noble metal-based electrocatalysts for OER.
By developing gem–difluoromethylene allenes as viable partners, regiocontrolled Rh(Ⅲ)-catalyzed redox-neutral C–C coupling/C–N cyclization has been realized to build the pyridin-2(1H)-one motifs with the embedment of a Z-configured monofluoroalkene functionality, in which either (hetero)aromatic or vinylic amides were found to be compatible. Integrated experimental and computational mechanistic studies revealed that a tandem regioselective allene 1,2-insertion/β-H elimination/hydrogen transfer/oxidative addition/cyclization/cis-β-F elimination involving an unconventional Rh(Ⅲ)-Rh(Ⅰ)-Rh(Ⅲ) catalytic cycle accounts for the established transformation. Through further FMO analysis and IGMH maps, a non-covalent weak interaction network between the gem–difluoromethylene part and the OPiv moiety was rationally defined for the unconventional and specific regioselectivity control.
Protein self-labeling tags achieve selective fusion and labeling of target proteins through genetic coding technology, but require exogenous fluorescent probes with fluorogenicity for protein tag binding to have the performance of wash-free fluorescence imaging in live cells. In this paper, we reported a fluorogenic probe 1 capable of ratiometric fluorescence recognition of SNAP-tag proteins. In this probe, the O6-benzylguanine derivative of 3–hydroxy-1,8-naphthalimide underwent a selective covalent linkage reaction with SNAP-tag protein. The hydroxyl group on the naphthalimide fluorophore formed a hydrogen bond with the functional group near the protein cavity. The excited state proton transfer occurred after illumination, to obtain the ratio fluorescence signal from blue emission to red emission, realizing the wash-free fluorescence imaging of the target proteins.
The origin of regioselectivity in meta-selective C-H borylation of benzamides directed by hydrogen bond interaction between ligand and substrate is elucidated through combined computational and experimental studies. We discover that a non-directed pathway, in which the urea moiety in ligand recognizes the O atom in Bpin instead of substrate, competes with the directed pathway and erodes the meta-selectivity. The non-directed pathway is sensitive to steric repulsion between Bpin and urea, and thus can be impeded by introducing a bulky substituent into the urea moiety. Accordingly, we optimize the ligand and improve the meta-selectivity in the Ir-catalyzed C-H borylation of some previously reported unsuccessful arenes.
A novel palladium-catalyzed carbonylative cyclization of alkene-tethered indoles with phenols or arylboronic acids is described, which provides a facile approach to access indolo[2,1-a]isoquinoline scaffolds. This method employs benzene-1,3,5-triyl triformate (TFBen) as the CO surrogate for the incorporation of a carbonyl group into indolo[2,1-a]isoquinoline scaffolds, and a variety of carbonyl-containing indolo[2,1-a]isoquinoline derivatives are prepared in good yields.
Two-photon imaging has attracted increasing attention owing to its deep tissue imaging capabilities. Therefore, many fluorophores have been developed to satisfy its requirements. However, long-wavelength emission fluorophores with an optically tunable group are rarely developed. In this study, two long-wavelength emission fluorophores with an optically tunable amino group were successfully developed by introducing strong electron acceptor and large conjugated group to the TPQL dye. TPCO2 displayed a bright red emission (λem = 638 nm, Φ = 0.15) together with high two-photon action cross section and good water solubility, which enabled higher signal-to-background ratios and deep tissue imaging. The proof-of-concept probe (TPCONO2) was successfully applied to the high signal-to-background ratio imaging of nitroreductase in liver fibrosis, further realizing diagnosis of the degree of hypoxia during liver fibrosis.
Information-carrying capacity has become an important factor in the development of encryption and anti-counterfeiting. Herein, a hydrogen-bonded organic framework (HOF-PyTTA) was developed as novel anti-counterfeiting ink without rare metals and a smartphone-based APP was written for encryption and anti-counterfeiting. We found that the fluorescence of HOF-PyTTA can be quenched by Fe3+ ions and recovered by the addition of ascorbic acid. And the fluorescence of HOF-PyTTA can be enhanced by the increasing concentrations of ethanol. Based on these stimulus-response properties, four anti-counterfeiting models with gradually increased security were studied. Mode one was printed by HOFs ink and decrypted by UV light. Mode two was based on HOF-PyTTA and CsPbBr3 inks (or HOF-PyTTA-Fe3+) which are used to separately print the genuine and pirated information. A decryption reagent was applied to get the genuine information. Furthermore, we successfully construct a dynamic information encryption anti-counterfeiting model using a fluorescence array in combination with an information encryption anti-counterfeiting APP. The circular array is printed by several concentrations of HOF-PyTTA ink and different RGB thresholds are set with the help of the information encryption anti-counterfeiting APP, to obtain distinct encrypted anti-counterfeiting information, thus accomplishing a high information-carrying capacity.
Molybdenum disulfide (MoS2) has attracted great attention in hydrogen peroxide (H2O2) activation as a Fenton-like catalyst and cocatalyst, but the distinct mechanism of generating •OH remains unclear. In this paper, the metallic 1T phase and semiconducting 2H phase of MoS2 nanosheets were prepared and applied in MoS2/H2O2 and MoS2/Fe2+/H2O2 systems with and without light irradiation. Compared with 2H-MoS2, 1T-MoS2 exhibited superior removal rates in degrading organic pollutants in the two systems under light irradiation. However, the phase had little effect on activating H2O2 in the MoS2/H2O2 system under dark conditions. This is because it was difficult for the surface •OHads generated in the MoS2/H2O2 system to diffuse into solution, while the •OHfree radicals were mainly responsible for degrading organic pollutants. When introducing light irradiation, external energy may accelerate the desorption of •OHads into •OHfree. Interestingly, the conversion between Mo4+ and Mo5+ triggered the decomposition of H2O2 in the Fenton-like reaction, while the cycle of Mo4+/Mo6+ promoted the regeneration of Fe3+ when employing 1T-MoS2 as a cocatalyst. Meanwhile, the 1T-MoS2 catalysts exhibited excellent stability and ability to degrade various organics in the two systems. This work offers deeper insight into the MoS2-based Fenton-like and cocatalytic mechanisms.
Clusteroluminescence (CL) materials, as an emerging class of luminescent materials with unique photophysical properties, have received increasing attention owing to their great theoretical significance and potential for biological applications. Although much progress has been made in the design, synthesis and application of CL materials, there is still a big challenge in the emission mechanism. So far, through-space interaction has been proposed as the preliminary mechanism of the corresponding clusterization-triggered emission (CTE) effect, but a systematic theory is still needed. This review summarizes the current mechanistic understanding of CL materials including organic/inorganic small molecules, and polymers with/without isolated aromatic structures. In addition, some strategies to achieve high quantum yield, adjustable emission color, and persistent room temperature phosphorescence in CL materials are also summarized. At last, a perspective of the mechanism and application of CL materials are demonstrated, which inspire the researchers working on the development of new kinds of functional materials.
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