Latest ArticlesReliable and selective sensing of dopamine (DA) is essential for early diagnosis of mental diseases. Among the various potential methods, nanozyme-based sensing systems have demonstrated promising sensitivity and reliability. However, owing to the lack of substrate specificity, it is challenging to selectively detect DA using nanozymes. Herein, based on the reactivity of the DA oxidation intermediates, we report a cascade colorimetric sensing system for the selective detection of DA using only a single nanozyme. It was disclosed that the oxidation product of DA catalyzed by Co-N-doped carbon sheets (Co-N-C, a common oxidase-like nanozyme), dopamine quinone (DAQ), showed significant biocatalytic electron-donating activity in the reduction of O2 to generate O2•−. Further using O2•− to oxidize 3,3′,5,5′-tetramethylbenzidine (TMB), a colorimetric sensing platform for DA was constructed with a linear detection range of 50 nmol/L to 50 µmol/L and a low limit of detection of 4 nmol/L. Thanks to the reactivity of the oxidation product, without any biometric units (such as nucleic acids, enzymes, and antibodies/antigens), the reaction selectivity of DA against other interferences (e.g., ascorbic acid, adrenaline, 5-hydroxytryptamine, and glutathione) was enhanced up to 71-fold. Beyond complicated cascade systems requiring at least two nanozymes, sophisticated artificial recognition via multiple interactions was simplified by exploiting the oxidative properties of product intermediates; thus, only a single common oxidase-like nanozyme was needed. This work offers a new strategy to enhance the selectivity of nanozymes for bioanalytical applications.
An oxidative annulation of 2-arylidene-1,3-indanediones with Meldrum's acid has been developed for the divergent syntheses of spirolactones with a spirocenter located at the γ-position with respect to the carbonyl group. This heteroannulation protocol tolerates various functional groups and delivers moderate-to-good product yields. Interestingly, the reaction outcomes are exclusively controlled by the reaction oxidant/medium. This annulation strategy can also be executed in the flow system with decent product yields. Control experiments revealed that the reaction proceeds via a radical tandem annulation pathway.
Silicon-based anodes including Si, SiOx and SiO2 could deliver ultra-large capacities, but degrade fast owing to huge volume change and low conductivity. Generally, large amounts of elastic binder and conductive additives were composited with nanosized silicon-based materials to yield reasonable cycling stability, which nevertheless not only decrease specific capacity but also induce inhomogeneous lithiation/delithiation as well as uneven stress variations. Artificial nanolattice has exhibited superior mechanical properties which could be ideal structure for silicon-based anodes, but yet faces challenges in integration of chemical reactivity, conductivity and mechanical stability. Herein, we fabricate artificial SiO2 honeycomb nanolattice consisting of numerous nanoscale SiO2 cells interconnected by through-holes, and conformal coating of highly graphitic carbon on the nanolattice is achieved through in situ catalytic graphitization. Moreover, the nanolattice is firmly bonded on Cu substrate through atomic interdiffusion irrespective of surface roughness. This unique structure allows fast charge transportation and homogeneous lithiation/delithiation throughout the micron-meter nanolattice, which results in excellent stability and large reversible capacity over 500 cycles at 1 A/g. The results highlight design and constructing artificial nanolattice can be an effective way to prevent chemo-mechanical degradation of silicon-based anode materials.
The topology of conjugated macrocycles had significant impacts on their photo-physical and photo-chemical properties. Herein, a series of π-conjugated macrocycles with diverse topology were synthesized via intramolecular McMurry coupling. Their chemical structure and macrocyclic topology were unambiguously confirmed via NMR, MALDI-TOF mass spectra, crystal analysis and scanning tunneling microscopy (STM). Depending on the structural topology and structural rigidity, these cyclic compounds display obviously distinctive emission behavior and photochemical reactions in the solution and in the solid state. Monocyclic phenylene vinylene macrocycle (denoted as MST) exhibiting aggregation-induced emission behavior, was more vulnerable to photo-cyclization in solution and triplet sensitizer promoted photo-dimerization due to lower strain and more flourishing intramolecular motions. After UV light irradiation, relatively more flexible MST could yield the anti-dimer via triplet excimer on the HOPG surface confirmed by STM investigation. By contrast, highly constrained bicyclic analogue (named as DMTPE) with central tetraphenylethene core, displayed high emission quantum yields of 68% both in solution and in the solid state, and was relatively inert to photochemical reactions and yield syn-dimer on the surface via singlet excimer involved [2 + 2] photo-dimerization. Based on the solution-mediated photo-polymerization of MST moiety, multicyclic porous carbon-rich ribbon connected with four-membered ring was successfully constructed and validated via STM imaging.
Epilepsy, as a chronic neurological disease of the brain, is closely related to oxidative stress, and the peroxynitrite (ONOO−) significantly rise up in this event. Therefore, ONOO− is considered as a potential biomarker for early prediction of epilepsy. However, some potential diagnostic reagents for epilepsy are hindered by the blood-brain barrier (BBB). Meanwhile, “drug repurposing” is attracting a growing interest. Edaravone (EDA), as a first-line drug in the clinical treatment of cerebral ischemia, plays antioxidant roles in scavenging free radicals, promising potential antiepileptic activity. Thus, it is imperative to develop fluorescent probes for monitoring ONOO− fluctuations in the epileptic brain. Hence, we proposed a novel fluorescent probe with the thiocarbonate as the promising recognition unit for ONOO− and dicyanoisophorone derivative as the fluorophore. Moreover, by the “three-in-one” strategy, the introduction of trifluoromethyl into DCI-ONOO-3 can extend the emission wavelength of the fluorophore, shorten the response and increase lipophilicity. Consequently, DCI-ONOO-3 was used for monitoring ONOO− fluxes in brain of epileptic mice and evaluating the antiepileptic efficacy of EDA. It opens up a new way for the design of BBB permeable fluorescent probes, and provides a convincing new method for the diagnosis and treatment of epilepsy.
Trifluoroacetic acid (TFA) catalyzed condensation reaction between tetraaminooxacalix[4]arene and N-alkylcarbazole-3,6-dicarbaldehyde in CH2Cl2 afforded a single product in 87%–89% yield. Well-defined yet undissolvable 1H NMR spectra suggested formation of robust and discrete structures in solution. X-ray single crystal analysis further revealed a giant twisted double-layer chiral macrocycle in the solid state, which was formed from [4 + 8] condensation of the two reactants via 16 imine bonds. DFT calculations discovered that only the [4 + 8] twisted product is thermodynamically favorable, which accounts for its highly selective and efficient formation out of a library of many other combinations.
Reactive oxygen species (ROSs) in Fenton process are of great importance in treating contaminants in wastewater. It is crucial to understand their chemical properties, formation, and reaction mechanisms with contaminants. This review summarizes the reactive oxygen species in Fenton process, including hydroxyl radical (•OH), superoxide radical (O2•−), singlet oxygen (1O2), hydroperoxyl radical (HO2•), and high-valent iron. •OH shows a trend to react with chemistry groups with abundant electrons through H-atom abstraction, radical adduct formation and single electron transfer. Electron transfer is discovered to be an important pathway when 1O2 degrades organic pollutants. Ring-opening and β-scission are proposed to be the possible ways of 1O2 to certain contaminants. Proton abstraction, nucleophilic substitution, and single electron transfer are proposed to explain how O2•− degrade pollutants. As the conjugated acid of O2•−, radical adduct formation and H-atom abstraction are reported for the reaction mechanisms of hydroperoxyl radical. High-valent iron in Fenton, namely Fe(Ⅳ), reacts with certain pollutants via single- or two-electron transfer. This review is important for researchers to understand the ROSs produced in Fenton and how they react with pollutants.
Post-synthetic modifications (PSM) have drawn great attention as a vigoroso tool to tune or enhance the performance of metal-organic frameworks (MOFs). However, the current PSM method usually have to sacrifice the porosity of MOFs to enrich their functionality, such as pore space partition (PSP) and post-synthetic elimination and insertion (PSE&I), causing a trade-off in this aspect. To address this issue, we herein propose a new PSM strategy of using the size-matching ligands as the bolts to lock MOFs’ pores, which could be anchored onto open metal sites (OMSs) after guest loading through a stepwise manipulation. As a result, the loaded cargoes undergo a controlled releasing process with respect to different bolt ligands. Our proposed strategy provides a promising way to balance the functionality and porosity of MOFs.
The first example of metal Sn-fused perylene diimides (PDI) derivative (Sn-PDI) was designed, synthesized, and investigated. To obtain this type compound, a simple one-pot synthesis, named stannylative cycloaddition reaction, has been successfully developed via a palladium-based catalyst system. The novel mechanism exhibits that the reaction experiences oxidative addition, Pd-cyclization, stannylation, Pd-Sn-cyclization, and reductive elimination processes successively. This stannylative cycloaddition does realize unique σ-π hyperconjugation effect and therefore significantly influencing on the photophysical, electrochemical and excited state properties. Compared with those of PDI, both of the absorption and fluorescence spectra of Sn-PDI display large red-shifts over 20 nm. The electron energy levels of Sn-PDI have changed with an uncommon regulation. And Sn-PDI gives a considerably raised highest occupied molecular orbital (HOMO) level of -6.00 eV More importantly, the singlet excitons of Sn-PDI could efficiently intersystem cross (ISC) into triplet state with a long lifetime of 17.8 µs, which is far longer than that (4.4 ns) of PDI.
Activated pancreatic stellate cells (PSCs) are the main source of collagen layer deposition and the key target in pancreatic fibrosis. However, no effective treatment specific to pancreatic fibrosis clinically, owing to the drug accumulation blocked by the collagen barrier and thus it is difficult to inhibit activated PSCs precisely. Herein, a PSCs-targeting nano-system based on “nanodrill” strategy (LA-PC) was designed to enhance the accumulation of all-trans retinoic acid (ATRA) in PSCs, relying on the platelet-derived growth factor receptor beta (PDGFRβ)-targeting peptide (pPB: C*SRNLIDC*) and collagenase (Col). After being injected into fibrotic mice via tail vein, the Col modified on LA-PC can remove the excess collagen layer, and the drug delivery efficiency through pPB targeting peptide was more than 5 times higher than that of free ATRA, as well as the degree of fibrosis significantly reduced. Notably, this nano-system effectively inhibited platelet-derived growth factor subunit B (PDGF-BB)/PDGFRβ axis on PSCs via a down-regulated extracellular signal-regulated protein kinase (ERK) pathway, and accordingly reduced the level of PDGF-BB. Thus, the smart platform provided a promising strategy for the treatment of pancreatic fibrosis to achieve the precise regulation of PSCs.
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