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The synthesis of organosilicon compounds has attracted considerable interest, especially the allyl silanes, which are regarded as ideal building blocks in the synthesis of small molecules and polymers. The traditional synthetic method for allyl silanes relies on the cross-coupling of Grignard reagent and chlorosilane (Silyl-Kumada reaction), transition metal catalyzed silylation of allylic alcohols with disilanes or silylboranes, and regioselective silylation of conjugated alkenes or allenes. Although some other methods were also developed, the using of transition metal catalysts has resulted in disadvantages such as contamination of desired allyl silanes and high production costs. Therefore, a mild and metal-free practical method is highly desired. We herein describe a metal-free difluoroallylation of silanes with α-trifluoromethyl alkenes in the presence of quinuclidine as hydrogen atom transfer (HAT) reagent under the irradiation of 30 W blue light-emitting diode (LED) (460~470 nm) at room temperature. To an oven dried Schlenk-tube, trifluoromethylpropene (0.1 mmol), silane (0.3 mmol), KHCO3 (0.1 mmol), 4-CzIPN (1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzene) (0.002 mmol) and MeCN (1 mL) were added under argon atmosphere. The reaction mixture was stirred under the irradiation of 30 W blue LED (460~470 nm) at room temperature. After completion of the reaction, the reaction solution was removed by reduced pressure and the residue was purified by silica gel chromatographic column to obtain gem-difluoroallylation products. A wide range of aromatic and heterocyclic α-trifluoromethyl alkenes were successfully applied in the difluoroallylation of silanes to afford difluoroallylsilanes. And all of the tested silanes, including trimethylsilane, sterically more demanding silanes as well as dimethylphenylsilane all participated in the present transformation readily to afford the corresponding difluoroallylsilanes in excellent yields. The present methodology has provided an efficient and cost-effective gram scale synthetic method for the preparation of difluoroallylsilanes under blue light irradiation in the presence of 4-CzIPN as organic photosensitizer. The scalability in large scale and excellent functional group compatibility of this transformation ensures broad applicability to a variety of difluoroallylsilanes. The proposed reaction mechanism showed that the reaction proceeded through the radical addition of α-trifluoromethyl alkene with silane free radical and subsequent β-fluoride elimination.
As an anode material for Li-ion capacitors (LICs), TiO2 exhibits pseudocapacitive behavior, low sodium storage potential and small structural changes in lithium storage process. However, poor conductivity and slow ion diffusion lead to sluggish lithium storage kinetics. Using sodium dihydrogen phosphate (NaH2PO4) as a phosphorus source, P-doped TiO2/C (P-TiO2/C) nanotubes are prepared by a simple solvothermal method to improve the lithium storage performance of TiO2. The P-TiO2/C nanotubes composed of nanosheets grown vertically on the surface can provide effective contact areas between electrolyte and active materials. And the C and P in P-TiO2/C are derived from the carbonization of alcohols and decomposition of NaH2PO4. P-doping easily causes P—O—Ti bond formed in TiO2 by P5+ replacing part of Ti4+, which can effectively improve the conductivity of TiO2. Electrochemical tests show that the P-TiO2/C anode for Li-ion batteries exhibits a high specific capacity (335 mAh•g-1 at a current density of 0.1 A•g-1), excellent rate capability (92 mAh•g-1 at a current density of 2.0 A•g-1) and long cycle performance (135 mAh•g-1 at a current density of 1.0 A•g-1 after 1000 cycles). In addition, the pseudocapacitive contribution of P-TiO2/C anode is about 96% at a scan rate of 2 mV•s-1. The superior lithium storage performance of P-TiO2/C nanotubes is derived from the P-doping in TiO2, which can change the electron structure of TiO2, which facilitates the electrons transport and lithium diffusion kinetics. The LICs assembled by P-TiO2/C anodes and activated carbon cathodes have a high energy density of 74.7 Wh•kg-1 at a power density of 250 W•kg-1, which are higher than some LICs based on titanic-based compound anodes. And the capacity retention of the LICs is about 43% after 10000 cycles at a current density of 1.0 A•g-1. In addition, after 10000 cycles test, a fully charged LICs can still light up the “LIC” model composed of 18 red LED lights. This work provides an idea for the design of TiO2 anode materials for high-performance LICs.
The direct synthesis of light olefins from syngas via Fischer-Tropsch synthesis reaction is a promising technology for direct synthesis of olefins from syngas. The key is to improve the selectivity of light olefins through the regulation of product distribution. In this work, the hydrophobic Fe@Si catalyst was prepared by room temperature solid state method- Stöber-silylation method, and then the catalyst was combined with SAPO-34 molecular sieves with different contents to prepare Fe@Si/S-34 composite catalysts. The effects of SAPO-34 molecular sieve content on the physicochemical properties of the catalysts were investigated by X-ray diffraction, scanning electron microscopy, N2 adsorption-desorption, NH3 temperature programmed desorption and water contact angle measurement. The results showed that the content of SAPO-34 molecular sieve has significant influence on the surface area, pore volume, acidity and hydrophobicity of the catalysts. With the increase of SAPO-34 molecular sieve content, the specific surface area and total pore volume of the catalyst increased, the weak acid and medium-strong acid sites increased, and the hydrophobicity weakened. The catalytic performance evaluation results showed that the Fe@Si/S-34 composite catalyst decomposed C5+ hydrocarbons into light hydrocarbons, significantly reduced the selectivity of C5+ products and increased the selectivity of C2~C4 hydrocarbons. Appropriate SAPO-34 molecular sieve could significantly improve the selectivity of C2~C4 olefins. When the mass ratio of Fe@Si catalyst to SAPO-34 is 2, the C2~C4 olefin selectivity of Fe@Si/S-34 catalyst is the highest, the conversion of CO is 80.0%, the selectivity of CO2 in the product is 8.9%, and the selectivity of C2~C4 olefins is 31.1%. In this study, the hydrophobicity of Fe@Si catalyst and the cracking activity of SAPO-34 molecular sieve for C5+ hydrocarbon were coupled together to inhibit the water-gas shift (WGS) reaction, reduce the CO2 selectivity and obtain higher C2~C4 olefin selectivity, which provided a new strategy for the development of catalysts for Fischer-Tropsch synthesis to olefins.
A large number of chiral drug molecules have a chiral structure containing both D- and L-enantiomers, leading to the mirror image arrangements of the two forms eliciting quite different physiological responses. Penicillamine (Pen) is a common chiral drug that is obtained from penicillin, and researchers have been making continuous efforts to achieve rigorous analysis and discrimination of the two enantiomers. Based on chiral Schiff base macrocycles containing NH functionalities have the advantages of mild synthesis conditions and convergence of structural arrangement. Here we report two enantiomers of the mono-Schiff base macrocycle containing chiral NH moiety in the cyclic structure (CR and CS), and the binding affinity and enantioselectivity of the cyclic enantiomers toward small molecules penicillamine (D-Pen and L-Pen). The crystal structures of the mono-Schiff base cyclic enantiomers were determined by X-ray diffraction analysis, and the results show that the two cyclic enantiomers exhibit twisted non-planar conformation, in which the chiral NH proton points to the inside of the ring cavity. The interactions between different enantiomers of the chiral macrocycle and penicillamine were investigated by ultraviolet visible (UV-Vis) and hydrogen nuclear magnetic resonance (1H NMR) titration, and the results show that the chiral macrocycle binds with the enantiomers of penicillamine with a bonding ratio of 1∶1, binding constants around 107 L•mol-1, and the complexes of [C-Pen+H]+ can be easily formed and detected by electrospray ionization-mass spectrometry (ESI-MS). The interactions between different enantiomers of the chiral macrocycle and penicillamine are attributed to the intermolecular hydrogen bonding of enantiomers by the asymmetrical chiral NH moiety in the mono-Schiff base macrocycle. Comparison of bonding constants based on the chiral macrocycle binds with the enantiomers of penicillamine, the results show that the chiral CR exhibits higher enantioselectivity for L-Pen, while CS exhibits the higher enantioselectivity for D-Pen, with a binding constant ratio around 2, respectively. Further, investigation of circular dichroism (CD) spectroscopic titration indicate that the penicillamine with the same chirality as the host macrocycle binds stronger with the host than its enantiomer with the host.
Aqueous zinc ion batteries possess the characteristics of cost-effectiveness, environmental benignancy, intrinsic safety, and relatively high energy density, and are promising to be used in large-scale electrochemical energy storage devices. However, the current commercial zinc foil anode is considerably excessive compared with cathode active materials, which significantly decreases the energy density of the battery. And there are serious problems of anode perforation, tab falling off and so on. Loading zinc on current collector as anode is effective to improve depth of discharge and avoid the electrode perforation. Nevertheless, the zinc dendrites and side reactions are prone to generate at the current collector interface, and they seriously affect the cycle life of the battery. In this review, the causes of zinc dendrites and side reactions and their influence on the electrochemical performance of zinc anode are analyzed, and the design ideas of the zinc anode current collectors are summarized from two aspects of composition selection and structure construction, including the selection of zincophilic materials, the design of preferred-orientation substrates and the construction of three-dimensional current collector structures. Designing an appropriate current collector can effectively regulate the plating and stripping behavior of zinc metal and promote the practical application of aqueous zinc ion batteries.
Copper(I)-catalyzed cycloaddition reactions, such as [3+2] cycloaddition of organic azides with terminal alkynes (CuAAC), unsaturated compounds with isocyanides, and nitrones with alkynes (Kinugasa reaction), are important methods for the constructions of different types of nitrogen-containing heterocycles. Great progresses have been achieved in such transformations and widely applied in various fields of organic syntheses. In these cycloaddition reactions, similar organocopper(I) intermediates are generated in situ, and can be trapped with additional electrophiles for further tandem or one-pot transformations. The development of the strategy to trap organocopper(I) intermediates in these reactions provides practical and efficient methods for the construction of multisubstituted or fused nitrogen-containing heterocycles. The advances in this area are summarized in this review: (1) trapping organocopper(I) intermediates in CuAAC reaction; (2) trapping organocopper(I) intermediates in the [3+2] cycloaddition of isocyanides with electron-deficient alkynes; (3) trapping enolate organocopper(I) intermediates in Kinugasa reaction. The review may be helpful for researchers to better understand the development and limitations for the trapping of organocopper(I) intermediates.
Thioesters play a very important role in biosynthesis and organic synthesis. Due to smaller orbital overlap of the C(2p) and S(3p) orbitals, the α-proton acidity of thioesters is higher than that of the related oxoesters, making thioesters useful enolate precursors in nature as well as in the laboratory. Meanwhile, thioesters are also efficient acylation reagents which can be used for the construction of ester bond and amide bond. Organocatalysis, a biomimetic catalysis usually with metal- free small organic molecules, is an emerging research field that has been booming since the beginning of the 21st century. In the past decade, many important achievements have been made in the organocatalytic asymmetric reactions involving thioester substrates, which have greatly broadened the reaction types of organocatalytic reactions with ester substrates and realized some reactions that cannot be achieved by using their oxoester analogues. The advances in organocatalytic asymmetric reactions involving thioesters are summarized in this review. According to the types of thioester substrates, these advances are classified to two types. One type is the organocatalytic asymmetric reactions with enolizable thioesters such as trifluoroethyl thioesters, malonic acid half-thioesters (MAHTs), monothiomalonates (MTMs) and dithiomalonates (DTMs). For these reactions, noncovalent interactions between catalysts and thioesters, including hydrogen bonding and ion pair interaction, have been used to promote the reaction and to achieve the high enantioselectivity. Another type is the catalytic asymmetric reactions with α,β-unsaturated thioesters. For the reaction of this type, various chiral organocatalysts, including chiral amines, ureas, NHC (N-heterocyclic carbene), isothiourea, amidine and others, not only activate the thioester substrates, but also control the enantioselectivity well through covalent and non-covalent bonds. Meanwhile, the mechanism of representative transformations will be briefly introduced and at last, the perspective in this area will be given.
Polynuclear transition metal complexes are widely used as homogeneous catalysts, and the polymetallic active sites of enzymes also play an important role in the mechanism of biochemical reactions under ambient conditions. As the efficient polymetallic catalysts for the activation of small molecules, trinuclear metal complexes have been attracted extensive attention. In order to understand the role of trinuclear transition metal complexes in catalytic reactions, we have classified the trinuclear transition metal complexes according to metal centers, and summarized the characteristics of their ligands, as well as their catalytic applications. Based on the metal centers, the geometric structure and electronic characteristics of the complexes are discussed. Based on the peripheral ligands, the characteristics of the coordination environment, which enable the aggregation of three independent metal sites, are highlighted. In terms of catalytic applications of trinuclear transition metal complexes, the catalytic mechanisms involving specific chemical bonds activation are focused on. Finally, we outlook the crucial potential application in this emerging field.
As one of the most important solid catalysts in chemical industry, zeolites are widely used in different fields. How to prepare zeolites greenly and efficiently has become a research hot issue with the increase of consumption year by year. Hydroxyl free radical is a highly active species, which can promote the depolymerization and repolymerization of aluminosilicates in the zeolite initial gel, and then accelerating the zeolite crystallization process. Besides accelerating the crystallization of zeolite, many studies have shown hydroxyl free radicals have other functions in zeolite synthesis. In this review, the role of hydroxyl free radicals in the synthesis of zeolites is systematically introduced via different generation methods. The challenges of the hydroxyl free radical assisted strategy are put forward, and its development directions are prospected.
γ-Alkylidenebutenolides [5-alkylidene-2(5H)-furanones] are present in many biologically important natural products. One of the most direct and effective approaches to construct such compounds is the strategy based on vinylogous aldol condensation. However, this typically involves 2~3 reaction steps or a one-pot reaction carried out at high temperature. Compared to imines/iminiums and aldehydes, inert feedstock amides are more stable and readily available starting materials. Benefiting from the significant development of direct transformations of amides over the past few decades, amides have been well served as the surrogate of imine/iminium and aldehyde. In this work, we report a facile and efficient synthesis of γ-benzylidenebutenolides under mild conditions through Ir-catalyzed vinylogous aldol-type condensation between N,N-dimethyl arylformamides and silyloxyfuran. Nineteen examples of amides were transformed and fourteen examples of γ-benzylidenebutenolides were obtained in up to 91% yields and up to 83∶17 Z/E ratio. Notably, this reaction is well compatible with benzamides bearing electron-withdrawing substituents such as halogen, nitro, cyano, vinyl, and CF3 groups, with yields from 67% to 91% and Z/E ratios from 55∶45 to 83∶17. The general procedure is described as following: to a dried 10-mL round-bottom flask containing IrCl(CO)(PPh3)2 (4 mg, 0.50 mmol%) was added a tertiary amide (0.50 mmol) in toluene (2.5 mL) and 1,1,3,3-tetramethyldisiloxane (TMDS) (115 µL, 0.65 mmol) at room temperature. After being stirred for 30 min, the resulting mixture was cooled to 0 ℃. Then CF3CO2H (57 µL, 0.75 mmol) and tert-butyldimethylsilyloxyfuran (TBSOF) (248 mg, 1.25 mmol) were added dropwise successively. The mixture was allowed warm to room temperature, reacted for ca. 10 h. Upon completion of the reaction, the resulted mixture was concentrated under reduced pressure. The residue was purified by flash chromatography on silica gel to provide the corresponding γ-benzylidenebutenolide. Additionally, a summary of the chemical shift values for the characteristic 1H NMR peaks of γ-benzylidenebutenolides was provided, aiding in the verification of the isomers’ Z/E configuration. In the case of E-isomers, the benzylic hydrogen and α-hydrogen of the carbonyl produce 1H NMR peaks at around δ 6.68~6.82 and 6.30~6.50, respectively. Conversely, for Z-isomers, the respective resonances shift upfield by approximately δ 0.75 and 0.15. The transformation of γ-benzylidenebutenolides into γ-benzylbutyrolactones [5-benzyl-2(3H)-dihydrofuranone], which are core skeletons found in many bioactive compounds, can be expediently accomplished through Pd/C hydrogenation reaction.
A class of C1-symmetric chiral N-heterocyclic carbene (NHC) ligands, incorporating both chiral fused-ring and sterically hindered N-substituted groups, were designed and synthesized, with the asymmetric reductive amination of quinoline aldehyde with arylamine compounds as the key step. Subsequently, using palladium-catalyzed intramolecular α-arylation and copper-catalyzed protoboration of functionalization of alkenes as the model reactions, the relationship between the structure of these ligands and their catalytic performance was systematically investigated. It was found that the 8-substituted groups on the tetrahydroquinoline scaffold and the bulky chiral N-substituted groups played important roles in enhancing the chiral induction ability of the ligands.
Oligomerization of propylene or other α-olefins is the main way to obtain various branched α-olefins, which are potential comonomers for the preparation of novel polymers with excellent properties or building blocks for manufacturing fine chemicals. Due to the different coordination-insertion and chain transfer modes involved in the oligomerization process of propylene, propylene oligomers with different structures were generally obtained, thus developing novel catalysts capable of catalyzing selective propylene oligomerization attracts great attention. In this work, a series of novel ethylene-bridged bis(indenyl) complexes meso-/rac-1~7 [ansa-C2H4-(3-R-4,7-Me2-C9H3)2MCl2: M=Zr, R=nBu (meso-/rac-1), iPr (meso-2), CH2Cy (meso-/rac-3), Bn (meso-/rac-4), CH2C6H4(4-CH3) (meso-/rac-5); M=Hf, R=CH2C6H4(4-CH3) (meso-/rac-7); ansa-C2H4-{2-Me-3-Bn-5,6-[1,3-(CH2)3]C9H2}2ZrCl2 (meso-6)] were synthesized via the reaction of the dilithium salts of the proligands with 1 equiv. of ZrCl4 or HfCl4 in Et2O, and in most of the cases, both the rac- and meso-isomers were separated in analytically pure forms via recrystallization. All complexes were characterized by nuclear magnetic resonances (1H NMR, 13C NMR) and elemental analysis (EA) methods. The molecular structures of typical complexes rac-1, meso-1, meso-2, meso-4, meso-5 and meso-6 were further determined by X-ray single crystal diffraction studies. The solid-state molecular structures of these complexes exhibit essentially similar geometrical parameters. The bond lengths between zirconium center and carbon atoms of the π-bonding five-membered ring of the indenyl unit vary slightly, suggesting a η5-coordination mode of the five-membered rings. In the presence of methylaluminoxane (MAO) as the cocatalyst, zirconium complexes meso-/rac-1~3 with an alkyl group on the 3-position of the indenyl ring catalyzed the oligomerization of propylene with high activities up to 9.73×106 g•mol-Zr－1•h－1, affording propylene oligomers with molecular weights of hundreds to thousands. Meanwhile, meso-/rac-1~3 exhibited low selectivities for β-Me elimination, with the highest allyl end group content being 41.3%. Zirconium and hafnium complexes meso-/rac-4~7 with a benzyl group or a substituted benzyl group on the 3-position of the indenyl ring were found to catalyze the dimerization of propylene in the presence of MAO, and mixtures including 1-pentene, 2-methyl-1-pentene, 4-methyl-1-pentene, 2,4-dimethyl-1-pentene were obtained. Temperature is the major factor affecting the activities of dimerization, and among them complex rac-4 showed the highest activity of 1.24×106 g•mol-Zr－1•h－1 at 80 ℃. The distribution of dimers is hardly affected by the reaction temperature or the Al/Zr molar ratio adopted. Among them, the hafnium complex rac-7 showed the highest β-Me elimination selectivity up to 60.1%.
Organic small molecules of low LUMO/HOMO (lowest unoccupied molecular orbital/highest occupied molecular orbital) energy levels are in shortage in terms of both variety and quantity. Their design and synthesis have important scientific and application value. The traditional strategy for designing organic small molecules of ultra-low LUMO/HOMO energy levels is to introduce multiple cyano groups into the molecules. In this work, a polycyclic aromatic hydrocarbon molecule containing four boron and nitrogen coordination bonds and two imide groups is designed and synthesized, without involving any cyano groups. The cyclic voltammetry examination with 0.1 mol•L−1 tetrabutylammonium hexafluorophosphate solution in dichloromethane as the electrolyte solution and ferrocene as the internal standard indicates that the molecule has a low LUMO and HOMO energy level of －4.77 eV and －6.39 eV, respectively. These values are the lowest for the reported fused-ring small molecules with boron and nitrogen coordination bonds and comparable to those of the reported organic small molecules with cyano groups. The density functional theory calculation results at the B3LYP/6-31G(d,p) theoretical level show that the molecule has a curved configuration and its conjugate skeleton has a dihedral angle of 23.6°. Both LUMO and HOMO are uniformly delocalized on the linear benzoid skeleton. It shows obvious near-infrared absorption in both solution and thin film state, with maximum absorption at 768 nm in film. The molecule can be used as a p-type dopant. After its blend doping, the electrical conductivity of the film of a typical p-type polymer P3HT is improved by 3 orders of magnitude. The doping behavior is also confirmed by UV-Vis absorption spectroscopy and electron paramagnetic resonance spectroscopy. This work develops a new strategy to achieve ultra-low LUMO energy level for organic small molecules without using cyano groups.
Mitochondria are the key regulatory organelles of many cell behaviors, and the reduction of mitochondrial membrane potential is considered to be one of the earliest events of cell apoptosis. Therefore, mitochondrial imaging and the detection and analysis of mitochondrial membrane potential are of great scientific significance for the detection and treatment of diseases. In this work, AuNCs/PLEL/JC/KLA, a mitochondrial targeted fluorescent nanoprobe, was developed using Au nanocages (AuNCs) mediated photothermal damage combined with temperature-sensitive drug release. At the same time, the temperature-sensitive hydrogel poly(d,l-lactide)-poly(ethylene glycol)-poly(d,l-lactide) (PDLLA-PEG-PDLLA, PLEL) is used as the outer structure to control the release. A mitochondrial targeting peptide (KLAKLAKKLAKLAK, KLA) was introduced as the "pointer" of the nanoprobe to specifically target the mitochondria. The colocalization experiment showed that the nanoprobe was highly colocalized with mitochondria, indicating that the nanoprobe was selectively enriched in mitochondria. It is worth noting that the nanoprobe has excellent photothermal properties, and its photothermal conversion efficiency can be as high as 39.11%. Therefore, under the irradiation of near infrared light, the probe can absorb light energy into heat. Subsequently, the results of Cell Counting Kit 8 (CCK-8) confirmed that the nanoprobes could achieve local photothermal damage at mitochondrial sites, triggering high temperature mediated mitochondrial dysfunction and inducing apoptosis of cancer cells. Meanwhile, rheological analysis and fluorescence curve showed that high temperature promotes the gel-sol transformation of PLEL thermosensitive hydrogel and realizes the release of fluorescent dye (JC-10). The confocal images of the cells showed that the released JC-10 fluorescent dye can display red and green fluorescence signals based on mitochondrial activity. In conclusion, the fluorescence nanoprobe can not only achieve mitochondrial targeted fluorescence imaging and damage cells, but also monitor the changes of mitochondrial membrane potential.
Luminescent uranyl phosphonate coordination polymers have been used for temperature sensing but have not yet been used for dual-response luminescence thermometers. Herein we report a luminescent uranyl phosphonate based on 2-(phosphonomethyl)benzoic acid (2-pmbH3), namely, (α-C8H12N)[UO2(2-pmb)] (1). This compound crystallizes in monoclinic space group C2/c and shows a layered structure. Within the layer, the uranyl ions are doubly bridged by O—P—O and O—C—O unis forming chains. The equivalent chains are cross-linked through corner-sharing of UO7 pentagonal bipyramids and PO3C tetrahedra forming a layer. The adjacent U···U distances within the layer are 0.5414 and 0.5743 nm. The organic groups of the 2-pmb3− ligand reside on the two sides of the layer. The interlayer space is filled with the racemic protonated phenethylamine cations to charge-balance the anionic layer. The shortest U···U distance between the layers is 1.239 nm. Compound 1 exhibits high thermal and water stability, especially in aqueous solution at pH 5~11 and in boiling water. The UV-Vis spectrum of 1 shows two broad bands peaking at 320 and 412 nm. The scalar-relativistic density functional calculations reveal that the two bands are associated with ligand-to-metal charge transfer (LMCT) transitions from ligand orbitals to metal orbitals lower-fδ (fz(x2−y2)). Photoluminescence properties show that 1 emits green-light at room temperature with six emission peaks at 481, 500, 516, 540, 564 and 591 nm, assigned to the electronic and vibronic transitions of S11-S00 and S10-S0ν (ν=0~4). Interestingly, both the emission intensity and the lifetime of compound 1 are temperature-dependent, making it possible to be used as a dual-response luminescence thermometer in the temperature range of 200~360 K. The intensity-dependent maximum sensitivity is 2.96%•K−1 (330 K) and the lifetime-dependent maximum sensitivity is 2.51%•K−1 (350 K), which are comparable to some lanthanide-based luminescent thermometers. This work provides a rare example of uranyl coordination polymers that can be used as a dual-response luminescence thermometer with wide operating temperature and good sensitivity.
Three types of Dawson type phosphomolybdate were synthesized and the in vitro antioxidant properties of the 11 compounds were investigated by the scavenging effect of different concentrations of polyoxometalates (0~50 mg/mL with distilled water and Vitamin C (VC) as positive control, three parallel experiments were set up for each group) on 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals, hydroxyl radicals, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and superoxide anion radicals. The cytotoxicity of the compounds was assayed by methyl thiazolyl tetrazolium (MTT) assay and combined with the results of in vitro antioxidant and cytotoxicity assays, cellular antioxidant studies were performed on H6[P2Mo18O62], H7[P2Mo17VO62] and H8[P2Mo16V2O62] using HepG2 cells as a model. The total intracellular antioxidant capacity was measured using the ABTS method: 10 μL of the sample/standard solution and 200 μL of the ABTS working solution were mixed in a 96-well plate for 5 min at room temperature, and the absorbance of the sample was measured at 734 nm using a multifunctional enzyme marker. WST-1 assay for cellular superoxide dismutase (SOD) activity: The samples to be tested were diluted to different concentrations and the absorbance values were measured at 450 nm using a multifunctional enzyme marker. The SOD inhibition rate of the sample to be tested was calculated and a sample concentration of 40%~60% inhibition was selected for the experiment. Cellular antioxidant assays showed that H6[P2Mo18O62] had a total cellular antioxidant capacity comparable to that of VC at higher concentrations (25 μmol/L and above); it enhanced the activity of cellular superoxide dismutase (SOD) and was more active than VC. We investigated the interaction mechanisms of molecular docking between polyoxometalates and α-glucosidase. The results showed that all 11 compounds had good antioxidant properties, and molecular docking showed that the binding inhibition of the polyoxometalates to the amino acid residues in the active centre was reversible mainly through hydrogen bonding and van der Waals forces, and that the docking fraction was negative and the reaction could proceed spontaneously, but the types of amino acids involved varied. Among them, H6[P2Mo18O62], H8[P2Mo17Fe(OH2)O61], H8[P2Mo17Ni(OH2)O61], H7[P2Mo17VO62] and H8[P2Mo16V2O62] performed well and could be alternative materials for antioxidants with both α-glucosidase inhibiting effect.
Preparation of undoped rare earth element, inexpensive and environmentally friendly single-phase quantum dots luminescent materials is crucial for realizing large-scale commercial application of white-light quantum dots diodes (WQLEDs). In this work, zinc sulfide quantum dots (ZnS-QDs) were prepared by a one-step hydrothermal method. The experimental method was to add zinc acetate into the mixed solution of water and ethanol, adjust the pH to 5~6, and then add thiourea. All raw materials were evenly mixed and put into a high-temperature hydrothermal reactor, and then ZnS-QDs was synthesized under the high-temperature condition of 240 ℃. By changing the ratio of water and ethanol in the solution and adjusting the pH, ZnS-QDs was obtained. The fluorescence emission peak of ZnS-QDs was about 535~566 nm. The thermogravimetric analysis of the obtained ZnS-QDs showed that the thermal decomposition temperature was up to 680 ℃. The measured fluorescence quantum yield was 16.3%. The luminescence mechanism of zinc vacancy in ZnS-QDs and the influence of changing synthesis conditions on the band gap width were discussed by UV absorption spectrum and theoretical calculation. After the mixture of ZnS-QDs phosphors and organic silica gel was dropped on the ultraviolet LED chip with the excitation light source of 365 nm, the input voltage was 3.4 V and the current was 100~500 mA, the light was lit. Standard white quantum dot LEDs were obtained. The international commission on illumination (CIE) coordinates of WQLEDs at 300 mA are (0.3725, 0.4006), the color rendering index (CRI) is 76.6 and the correlation color temperature (CCT) was 4500 K. The tricolor ratio (R, G, B) was R=14.6%, G=83.5%, B=1.8%. It could be seen that green was the majority of the three colors, and the blue content was relatively small, which was conducive to the protection of eyes. This study provides a promising method for realizing WQLEDs using single-phase quantum dots.
Understanding the relationship between the chemical signals generated by biological materials and cellular behaviors has great significance for the design and preparation of high-performance tissue engineering biomaterials. In the past several decades, silicate bioceramics have been widely used in tissue engineering. Bioactive ions released from silicate bioceramics can act as chemical signals to regulate cellular behaviors and promote the tissue regeneration. Moreover, by regulating the components of silicate bioceramics, silicate bioceramics can generate specific chemical signals to regulate cellular behaviors of multiple cells. Here, by introducing molybdenum (Mo) element into silicate bioceramics, we have successfully developed Mo-containing silicate (MS) bioceramics which are able to regulate cellular behaviors of tendon stem/progenitor cells (TSPCs) and bone marrow mesenchymal stem cells (BMSCs) simultaneously. Using ammonium molybdate as a source of Mo element, MS bioceramics were prepared by chemical coprecipitation method. The synthesized MS bioceramics were mostly below 10 μm in size and had uniform distribution of Mo elements. Moreover, MS bioceramics were composed of high-purity CaMoO4 and CaSiO3. To explore the effect of chemical signals generated from MS bioceramics on TSPCs and BMSCs, we prepared MS extracts for cell culture. MS bioceramics supported the survival of TSPCs and BMSCs and maintained a better cellular state during the culture period of 5 d. Due to the released Ca, Si and Mo ions from MS bioceramics, TSPCs and BMSCs cultured with MS extracts exhibited excellent proliferation and migration activities. Interestingly, after cultured with MS extracts in the appropriate concentration, the expression of osteogenic genes and protein of BMSCs and the expression of tenogenic genes and protein of TSPCs were significantly enhanced, suggesting that chemical signals generated by MS bioceramics simultaneously promoted the specific differentiation of TSPCs and BMSCs. Such MS bioceramics are believed to be an effective “bioactive factor” for repairing injury at the tendon-bone interfaces.
Azulene has attracted significant attention for constructing novel optoelectronic materials. Tuning the dipole orientation of azulene unit in azulene-based conjugated polymers has recently aroused widespread concern and remains a great challenge due to the lack of synthetic method. Herein, we report three 2,6-azulene and 3,4-propylenedioxythiophene (ProDOT) based conjugated copolymers P(AzProDOT-1), P(AzProDOT-2) and P(AzProDOT-3) with different dipole arrangements of azulene moieties. The regioregularity of these 2,6-azulene-ProDOT-based conjugated polymers was tuned by monomer design and direct arylation polymerization strategy, which enables a thorough study of the impact of the regioregularity on the properties of these polymers and their charge transport performance. The dipole orientation of 2,6-azulene units were regiorandom for P(AzProDOT-1), regularity with medium regioregularity for P(AzProDOT-2) and regularity with high regioregularity for P(AzProDOT-3), respectively. The number-average molecular weight values of P(AzProDOT-1), P(AzProDOT-2) and P(AzProDOT-3) estimated by gel permeation chromatography (GPC) were 11.1, 11.4 and 9.3 kDa, respectively, and the chemical structures of these three polymers were also characterized by high-temperature 1H NMR spectra. Ultraviolet-visible (UV-vis) absorption spectra and cyclic voltammetry were conducted to evaluate the optoelectronic properties of these polymers. The blue-shift of the maximum absorption peak for P(AzProDOT-2) indicates its twisted polymer backbone and short effective π-conjugation length, while the red-shift of the maximum absorption peak for P(AzProDOT-3) demonstrates the more planar conjugated skeleton and the longer effective π-conjugation length, although its molecular weight was a little lower. Besides, there was a prominent shoulder peak in the thin film of P(AzProDOT-3) in UV-vis absorption spectrum, indicating the stronger interchain interactions in solid state. All these observations were in agreement with the density functional theory (DFT) calculation results. Due to the electron-donating property of ProDOT, these three polymers displayed strong and sensitive proton responsiveness. The ultraviolet-visible-near infrared (UV-vis-NIR) spectra of these three polymers showed obvious red-shifts (>150 nm) upon protonation, and the films of these polymers also possess strong proton responsiveness properties. Charge-carrier mobilities of these three polymers were measured by the space-charge-limited current (SCLC). The hole mobilities of thin films of P(AzProDOT-1), P(AzProDOT-2) and P(AzProDOT-3) were 1.32×10−5, 9.14×10−5 and 1.41×10−4 cm2•V−1•s−1, respectively, and their electron mobilities were 1.62×10−6, 7.91×10−6 and 1.66×10−5 cm2•V−1•s−1, respectively. The atomic force microscopy (AFM) study demonstrated that the thin film of P(AzProDOT-3) possessed the smoothest surface and the smallest root mean square (RMS) roughness, proving the optimal SCLC performance of P(AzProDOT-3) among these three polymers. Our research highlights the significant and effective strategy of rational control regioregularity of azulene-based copolymer backbone to tune physicochemical properties and molecular packing for achieving better charge transport performance. Our study also aims to give valuable insight into precision synthesis of regioregular conjugated polymers based on low-symmetric conjugated building blocks.
Non-precious metal M-N-C catalysts have a low density of active sites, which requires increasing the catalyst loading amount per unit area to obtain sufficient active sites to ensure the required apparent output current of the proton exchange membrane fuel cells (PEMFCs). This inevitably increases the thickness of the catalytic layer. On the one hand, a thick catalytic layer increases the resistance to material transfer, and on the other hand, a thick catalytic layer is more prone to causing “flooding” problems, which further worsens the material transfer problem of the catalytic layer. To address the water flooding and material transfer efficiency challenges of Fe-N-C cathode catalytic layers, this study employed controlled pyrolysis of perfluorinated sulfonic acid ionomer side chains with hydrophilic sulfonic acid groups within the catalytic layer. The in-situ modulation of the hydrophilic-hydrophobic balance at the active sites of the catalyst creates an efficient three-phase interface, enabling high ion conductivity and efficient water and oxygen transport within the Fe-N-C catalytic layer. Consequently, the output performance and stability of the membrane electrode are significantly improved. The results demonstrate that the degree of sulfonic acid group pyrolysis within the catalytic layer ionomer can be effectively controlled by adjusting the pyrolysis temperature and duration. Using a catalytic layer with an ionomer to Fe-N-C catalyst mass ratio (I/C) of 0.5 as a model, the perfluorinated sulfonic acid ionomer's sulfonic acid group decomposition rate was 16.3% after 40 minutes of heat treatment at 250 ℃ under a N2 atmosphere, resulting in an increased hydrophobicity of the catalytic layer surface, as indicated by a surface water contact angle increasing from 113° to 134° while maintaining high ion conductivity. The corresponding membrane electrode exhibited optimal output performance, with a peak power density of 359.7 mW• cm－2, representing a 38% improvement over the pre-treatment electrode. Additionally, under a constant voltage of 0.4 V, the material transfer resistance of the heat-treated catalytic layer decreased by 29.8% to 242.48 mΩ•cm2 compared to the pre-treatment condition. During the 20-hour constant voltage discharge test at 0.4 V, the heat-treated Fe-N-C catalytic layer exhibited higher discharge current density than the untreated membrane electrode. This study demonstrates that partially controlled pyrolysis of catalytic layer ionomer is an effective method for improving the performance and stability of M-N-C non-precious metal catalyst membrane electrode fuel cells.
Work function-adjustable borophene-based electrode materials are of significant importance for achieving the maximum energy conversion efficiency of electronic devices owing to their vital role in efficient transferring of carriers. Accordingly, understanding the regularity in the gradation of the work function for adatom-borophene nanocomposites with diverse adatoms will facilitate the design of such materials. Herein, the structural stabilities, electronic structures, and work functions of M-decorated experimentally available bilayer α-borophene (M/DBBP; M=Li~Cs; Be~Ba) are investigated systematically. The results obtained indicate that M/DBBP are all thermodynamically and kinetically stable. Moreover, M—B bond length, binding energy (Eb), electron transfer between M and DBBP, and work function (ϕ) are linearly dependent on the ionization potential (IP) in the same adatom family for these investigated systems. Furthermore, we report the two exceptional binding energies of Li/DBBP and Be/DBBP, which deviate from abovementioned IP dependence, owing to their extremely small adatoms and the resulting significantly enhanced effective M—B bonding areas. Impressively, the forming interlayer multi-centered B—B bonds lead to a significantly enhanced interlayer interaction of Ca/DBBP relative to other nine M/DBBP systems. In addition to interpreting that the metallic M/DBBP possesses ionic sp-p and dsp-p bonds for M1/DBBP (M1=Li, Na, Be, Mg, Sr, and Ba) and M2/DBBP (M2=K, Rb, Cs, and Ca), respectively, in particular, we confirm that the positive IP dependence of ϕ for alkali (earth) metal/DBBP originates from the synergistic effect of charge rearrangement and the increasing induced dipole moment. Our predictions not only provide guidance to the experimental efforts towards the realization of work function-adjustable borophene-based electrodes, which can be utilized as cathode materials in electronic devices, but also present a rational understanding of the bonding rules between varying alkali (earth) metal adatoms and bilayer α-borophene.
Zinc ion is an essential component in enzymes and proteins and involves in many biological processes. Although many two-photon zinc ion probes have been synthesized and applied for detecting the zinc ion, the related theoretical study is still in the primary stage. To explore the mechanism of coordination induced two-photon absorption (TPA) enhancement for a piperazine-based zinc ion probe, molecular dynamics simulations in combination with quantum chemical calculations are employed to calculate the TPA properties of the probe and its coordination complexes. The configuration evolution of the probe and the coordination process in water are investigated by molecular dynamics simulations. It is found that there are two coordination modes, which include mono-coordinated mode and bi-coordinated mode, to form zinc complexes. In comparison with the probe, the coordination complexes have more planar backbones and more stable structures. On the basis of the simulated configurations, a series of geometries for the probe and the zinc complexes with two coordination modes are optimized by quantum chemical methods and their TPA properties are calculated by the response theory and two-state model. The results show that the coordination mode and the structure of piperazine unit have important effects on TPA. The twisted piperazine ring in the mono-coordinated complex is very beneficial for improving the strength of TPA without changing the wavelength. The bi-coordination always decreases TPA and produces a blue-shifted wavelength. Through configurational sampling, the averaged TPA spectra for the probe and the complexes are calculated and the influence of the structural flexibility is analyzed. Because the probe has a more flexible structure, its averaged TPA intensity decreases, and then the great increase of TPA can be observed in the zinc complexes with mono-coordinated mode. Therefore, it is the special complex with mono-coordinated mode and the flexibility of the probe that produce the TPA enhancement after coordination in experiment. The present research would be helpful for understanding and predicting of the photophysical properties for two-photon zinc ion probes.
Sodium metal batteries have been regarded as promising candidates for next-generation energy storage systems due to their impressive capacity and natural abundance. However, the high reactivity of Na, unstable solid electrolyte interface (SEI) and Na metal dendrite growth with safety hazards inhibit their applications. Various strategies have been proposed to solve the above issues. Designing porous current collectors has been recognized as one of the most promising solutions. Porous carbon/carbon nanotubes/graphene- based materials are widely investigated as host materials for sodium metal anode. However, the sp2 carbon faces serious issues, such as aggregation or stacking because of their π-π interactions. Herein, we tackle this issue by using ionic liquid as additive during hydrothermal process. The non-covalent interaction between 1-butyl-3-methylimidazolium (Bmim+) and sp2 carbon (carbon nanotubes and reduced graphene oxide) helps to inhibit the aggregation of CNTs and the stacking of rGO layers. Also, their interactions induced the CNTs and rGO to form three dimensional (3D) porous carbon (3D-GC) current collector. The ionic liquid 1-butyl-3-methylimidazolium bisulfate ([Bmim][HSO4]) plays great role as a stabilizer and surfactant. The reduced surface tension of the system is also favorable for uniformly interweaving the CNTs and rGO. The prepared 3D-GC exhibit micro-meso-macro porous structure, which provides a large storage space for sodium metal. Meantime, the composite shows a high electrical conductivity, leading to a low deposition overpotential (5.6 mV) of sodium metal. As a result, the 3D-GC@Na anode exhibit an impressive cycling stability for over 1450 cycles (2900 h) at 1 mA•cm−2 with a capacity of 1 mAh•cm−2. Moreover, when being used in full cells with Na3V2(PO4)2F3 as cathode, they also show well performances.
With the widespread development of new energy vehicles, all-solid-state batteries have attracted wide attention because of their high safety and high energy density. The oxide/sulfide solid electrolyte is expected to combine the low grain boundary resistance, room temperature workability and low interfacial resistance of sulfide with the excellent electrochemical stability and low cost of oxides. However, the lack of reliable preparation techniques for composite solid electrolytes with higher oxide content limits the further reduction of cost and the further improvement of stability. In this work, Li1.3Al0.3Ti1.7(PO4)3 (LATP)/Li8P2S9 (LPS) electrolyte was employed as an example system for the synthesis of sulfide-based solid electrolyte with high oxide content via grinding and subsequent hot compressing. The LATP and LPS was mixed through normal grinding (Gr), low speed ball grinding (LB) and variable speed ball grinding (VB). The results showed that grain refinement of oxide and the decrease of pore content were achieved by VB. In addition, the distribution of S and Ti elements proved that LATP was uniformly dispersed in the VB-LATP/LPS (LATP/LPS prepared by VB). According to the X-ray diffraction (XRD) pattern, the distortion of LATP and LPS lattice in VB-LATP/LPS was attributed to the mutual diffusion of oxygen and sulfur atoms at the interface. As a result, VB-LATP/LPS exhibited high lithium ion conductivity (3.35 mS•cm－1), low electron conductivity (1.53×10－8 S•cm－1) and relatively low lithium ion migration activation energy (11.75 kJ•mol－1) at room temperature. Besides, the good interfacial bonding state and addition of hard oxides contributed to the high stability of the electrolyte/lithium interface. Furthermore, the all-solid-state battery assembled by VB-LATP/LPS showed a high capacity retention rate of 99% after 100 cycles, demonstrating excellent electrochemical stability. Such synthesis idea of combination with soft sulfide electrolyte and hard oxide electrolyte provides a feasible strategy for the synthesis of cost effective composite solid electrolytes.
Active colloidal motors are micro- or nanoparticles that can move actively and perform complex tasks at the micro- or nanoscale. They have great potential for various applications, such as environmental remediation, biomedical applications and micro- and nanomanufacturing. The development and latest research progress of active colloidal motors are reviewed, their driving mechanisms in different environments are discussed, and the development of new colloidal motors and their applications in different fields are explored. Finally, the perspective on the possible application of active colloidal motors in the field of electromagnetic wave absorption, including the mechanism of action, possible preparation strategies for electromagnetic wave absorption, and their potential performance and new functional applications are presented.
Electrochemical sensors are widely employed for the detection of substance concentrations owing to their rapid response, high sensitivity, remarkable selectivity, and ease of quantification. With the rapid advancements in flexible electronics technology, electrochemical sensors have been transitioned into flexible and wearable formats, facilitating the in-situ analysis of biological liquids or gases. This breakthrough has opened avenues for portable, noninvasive continuous monitoring of physiological parameters and health status, thereby unveiling vast potential in the realm of intelligent healthcare and medical applications. Building upon these remarkable progressions, this paper primarily focuses on the design and applications of flexible electrochemical sensors tailored specifically for noninvasive medical detection. Firstly, the basic components of flexible electrochemical sensors are elucidated. Subsequently, the working principles of various types of sensors are expounded upon. Furthermore, we systematically review the latest advancements in the detection of pivotal chemical substances in typical biofluids such as sweat, interstitial fluid, tears, saliva, and breath, using flexible electrochemical sensors. Finally, the challenges and opportunities of flexible electrochemical sensors for applications in noninvasive health monitoring and precision medicine are discussed and proposed.
Photothermal effect refers to the characteristics of materials that could generate heat under the irradiation of sun or laser light. It can not only maximize the efficiency of solar energy conversion, but also break through the spatiotemporal limitation of laser light transmission, which holds excellent potential and application prospect. Currently, researchers have developed many photothermal materials based on three main photothermal effect mechanisms, plasmonic heating, non-radiative relaxation in semiconductors and thermal vibration in molecules, which include metal nanomaterials, inorganic semiconductor materials, carbon materials, two-dimensional transition metal carbides and nitrides (MXenes), organic small molecules, polymer materials, metal organic framework (MOF), covalent organic framework (COF), organic co-crystals materials, etc. Among them, inorganic materials have the advantages of a wide range of sources, simple structure and excellent thermal stability, while organic materials can be easily designed in structure, and have better biocompatibility. Based on these attractive characteristics, the photothermal effects have been extensively investigated in the area of energy utilization, biomedicine, catalytic conversion, intelligent devices, etc., and realized the applications in photothermal solar evaporation, photothermal therapy, photothermal catalysis, photothermal functional materials. In addition to the rapid development of traditional applications, novel applications have also been explored, such as anti-icing coating, reversible adhesive, agriculture heaters, photothermal energy storage, photothermal induced self-healing materials, photothermal-driven soft robots, etc. However, there are still some challenges in the research of photothermal materials, such as narrow absorption range, low photothermal conversion efficiency, limited application development, and difficulty in use of the elevated temperature induced by photothermal effect. This review briefly summarizes the progresses in the development, utilization of photothermal materials. The challenges and the development direction of photothermal materials are also discussed. It is hope that this review could provide inspiration for the further research in terms of construction of new photothermal materials and innovation of their application.
Nucleic acids-based therapy has been developed rapidly in recent years and the effective treatment is closely related to the safe and efficient delivery of nucleic acids. On the one hand, it is difficult for nucleic acids to penetrate cell membranes and express. On the other hand, unlike other drugs, some genetic therapeutics work at the condition of expressing in specific organ or cells. Therefore, delivery vectors are particularly important: they are expected to protect nucleic acids and achieve efficient transfection. Besides, they should be able to target specific sites to increase the probability of nucleic acid expression in target cells. Given the importance of polymer nucleic acid vectors, in this review, the research progress of polymeric delivery systems is summarized, including how to achieve aggregation from the administration site to the target site, and the state of the art of organ-targeting polymer nucleic acid vectors. Finally, the perspective of organ-targeting polymeric nucleic acid vectors is given.
Over the past decades, thanks to the excellent directivity and stability of coordination bond between terpyridine and ruthenium ions, a large number of bis(terpyridine)-ruthenium(II) complexes have been constructed and reported through three synthetic strategies, i.e., direct coordination assembly, stepwise coordination assembly and post-assembly modification. Moreover, due to the unique photoelectric properties of bis(terpyridine)-ruthenium(II) complexes, these structures have shown great promise for applications in photothermal conversion, photovoltaic materials, electronic memory and anion exchange membranes. Therefore, this review summarizes the research progress of bis(terpyridine)-ruthenium(II) complexes with particular focus on small molecules, discrete supramolecules and polymers. Furthermore, current challenges and opportunities are briefly discussed.
Subnanometer scale is an important feature size in the field of material science. Sub-nanometric materials (SNMs) have several unique properties different from molecular-based or traditional nanomaterials, and their size is comparable to the diameters of the polymer single strand/DNA, clusters and the single unit cell of inorganic crystals. The surface atom ratio of SNMs is close to 100%, which brings significant surface atom rearrangement and electron delocalization effects. 1D SNMs are expected to become an entry point to break the boundary between polymers and inorganic materials due to their excellent structural flexibility, machinability, viscosity and gelation. Electron delocalization in SNMs changes the electronic and band structures of the materials, and significantly enhances the external field coupling effects, resulting in excellent photothermal conversion and catalysis properties. This review focuses on the surface atom rearrangement and electron delocalization effects at the subnanometer scale. The precise synthesis and assembly, polymer-like properties, electronic structure, and catalytic properties of SNMs are introduced. It is hoped that this review can help to deeply understand the coupling law of subnanometer scale interactions and structure-function relationship, further promoting the accurate synthesis of SNMs and the construction of functional systems.
Coupled small molecule electrocatalytic oxidation reaction can not only reduce anode overpotential, improve hydrogen evolution reaction (HER) efficiency, but also produce high value-added chemicals, which is an effective strategy to improve the performance of electrocatalytic water splitting. The development of non-noble metal based electrocatalysts with high conductivity and low oxidation potential is the key issue. Herein, Ni3N nanoparticles (Ni3N-NPs) with low oxidation potential and high conductivity were prepared by annealing and nitriding Ni(OH)2 nanosheets precursors. Compared with Ni(OH)2, Ni3N-NPs has a smaller Faraday resistance, a lower oxidation potential, a smaller Tafel slope (29 mV•dec–1), and exhibits the better electrocatalytic oxidation performance towards ethylene glycol (EG). At 1.36 V, the Faraday efficiency of electrocatalytic EG oxidation to formate reached 91.16%. The structure of Ni3N-NPs before and after the electrocatalytic oxidation reaction was characterized in detail by X-ray diffractometer (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). It was found that in the electrocatalytic EG oxidation process, the surface of Ni3N-NPs was oxidized into NiOOH, while EG underwent dehydrogenation and oxidation to form formic acid on the catalyst surface, and the NiOOH was synchronously reduced by H and converted into Ni(OH)2. In addition, Ni3N-NPs has good universality for electrocatalytic oxidation of small organic molecules.
Improving the cathodic oxygen reduction reaction (ORR) activity faces significant challenges due to the linear scaling relationship and disparate adsorption strengths of the intermediate species, *OH and *OOH. This causes the ORR cannot proceed under nearly thermodynamic equilibrium potential, leading to low reaction kinetics compared to the anodic hydrogen oxidation reaction. Even with the use of optimal catalysts like Pt, the theoretical overpotential remains at around 0.45 V, because of the excessively strong *OH adsorption and weak *OOH adsorption, with *OH desorption serving as the potential determining step (PDS). In this study, we aim to enhance the intrinsic catalytic activity of ORR by constructing a three-dimensional spatial geometric structure utilizing a Pt crystalline model with multi-low index surface consisting of (100)-(110)-(111). The density functional theory calculations are employed to investigate the impact of a concave and convex arrangement formed by interlacing polycrystalline surfaces on the adsorption of *OH and *OOH. The results indicate that the investigated spatial configuration can break the linear scaling relationship between *OH and *OOH adsorption and allow for independent optimization of their adsorption strengths, thereby reducing the originally theoretical overpotential. The adsorption of intermediates reveals that the coordination unsaturation of active sites can be utilized as an indicator of the effect of the spatial geometric structure on species adsorption. The adsorption strength of the active site spatial structure follows the order of “concave”<“convex”≤“flat”, with the concave sites of Pt(111)-(100) exhibiting the most optimal adsorption strength for both *OH and *OOH. The 4e– associative mechanism on single sites further reveals that the concave active sites located at Pt(111)-(100) play a significant role in independently regulating the adsorption of intermediate species and show higher catalytic activity than Pt model with single-low index surface. This is due to the minimal coordination unsaturation, which allows for a balance of *OOH and *OH adsorption strengths and then regulates the protonation of *O as the PDS. On the other hand, the 4e– dissociative mechanism demonstrates that dual active sites can further enhance intrinsic catalytic activity compared to single active sites. Specifically, the “flat-concave” dual active sites at Pt(111)-(100) are shown to significantly reduce the theoretical overpotential to 0.27 V. This polycrystalline faceted catalyst with a concave-convex spatial structure is highly promising for use in other reactions that require the selective modulation of multispecies adsorption and the enhancement of intrinsic catalytic activity, particularly those that exhibit a linear scaling relationship.
Construction of biomacromolecules via enzyme-mediated catalytic assembly from small biomolecules is fascinating for preparing functional biological materials. The challenge remains on how to control the structure and functions of biomacromolecules through substrate regulation. A sequence of crucial biomacromolecules, melanin, were prepared via simple substrate derivation, which controls the key polymerization sites in enzyme catalyzed self-assembly process. In detail, we designed three tyrosine derivatives, namely, 3-fluorotyrosine [Tyr(F)], N-acetyltyrosine [Tyr(N-Ac)], and tyrosine ethyl ester [Tyr(OEt)]. The three substrates corresponded to the blockage of different tyrosinase-mediated polymerization active site, and tyrosine was used as the reference. The above small molecules as substrates (1.0 mmol/L) and tyrosinase (2 U) were mixed in phosphate buffer (pH=8.5, 0.10 mol/L, 2.0 mL), which was stirred in an air environment of 25 ℃. After 24 h, the reaction was quenched and the mixture was centrifuged to obtain different melanin nanoparticle products (MNPs). Characterizations from transmission electron microscopy (TEM), infrared spectroscopy (IR), and X-ray photoelectron spectroscopy (XPS) showed that all the melanin products had eumelanin-like skeleton, but were different in the degree of polymerization and microscopic chemical structures. These structure-modified MNPs showed overall absorption in the ultraviolet-visible-near infrared (UV-vis-NIR) region, thus enabling photothermal conversion in the NIR-I region. The photothermal conversion efficiency of MNP, MNP(F), and MNP(OEt) (3 mg•mL-1) was measured to be 46.6%, 37.0%, and 25.8% [laser 808 nm, 1.5 W, where MNP(N-Ac) was not available due to rather low temperature increase]. Interestingly, in vitro experiment showed that MNP(OEt) exhibited better photothermal cytotoxicity than MNP, and this was probably because MNP(OEt) had a smaller particle size and less negative ζ-potential, which could ease cell endocytosis. This work demonstrated the feasibility to regu-late enzyme-mediated catalytic pathway via simple substrate derivation. It provides insights for the construction of new functional melanin materials and for revealing the relationship between biological macromolecular structure and function.
Of numerous environmental problems, the air pollution caused by toxic nitrogen dioxide has become more and more serious. Its timing detection is of utmost importance but challenging. It is known that NO2 sensors fabricated by zinc oxide-derived materials suffer some issues. And thus synthetic strategies such as doping and combining have been developed to improve sensitive performance and modify operation condition. However, the relevant sensing reaction mechanism still remains unclear; moreover, the experimentally structural characterizations on sensitive materials (SMs) and reaction intermediates are rather difficult at the atomic level, which turn much worse for the doped and combined SMs. In the work, density functional theory calculations have been exploited to examine copper-doped zinc oxide (marked as ZOC) and its composites ZOC/CN and ZOC/Gr. CN and Gr are short for 2D materials, graphitic carbon nitride (g-C3N4) and graphene, respectively. The local structures have been accessible for these SMs and their intermediates along the reaction pathway. It is shown that ZOC bears the Cu-Zn heterobimetallic adsorption active sites, which hold NO2 via Cu/Zn-O dative bonds. The introduction of copper increases metal contribution to high-lying occupied molecular orbitals (MOs). Major NO2→ZOC donation and minor back-donation interactions have been recognized by charge decomposition analyses in terms of fragment MOs. Consequently, its adsorption free energy towards NO2 is strengthened by 0.27 eV relative to pristine ZnO. These well interpret the experimental findings that the copper-doped zinc oxide has much faster response time. Further combination with g-C3N4 enhances the NO2-sensing performance, which turns out to be the best SM candidate. Exemplarily, ZOC/CN shows the most negative NO2 adsorption energy (–0.31 eV), very small uphill energy for the rate-determining step (0.27 eV) and modest formation energy of nitrate (–1.06 eV). With these, the SM not only responses NO2 rapidly but also desorbs nitrate at mild experimental condition. In brief, the theoretical study allows to deeply understand synthetic strategies that can improve sensing performance, and helps to search out novel sensitive materials.
The degree of polymerization often affects the blending microstructure of the active layer in polymer solar cells (PSC), resulting in a large difference in device performance. Generally, when the degree of polymerization is low, the power conversion efficiency (PCE) of PSC is usually significantly reduced due to the impact of charge transport. To address this issue, we synthesized a series of polymer donors with rotaxane structure by introducing crown ether into the polymers, and four molecules PM6-C1, PM6-C2, PM6-C3 and PM6-C4 with different contents of crown ether were obtained. The rotaxane structure is composed of cyclic compounds and polymers through non-covalent bonds, which can affect intermolecular stacking by non-covalent interaction while retaining the excellent photoelectric properties of the polymer. The crown ether was randomly inserted into the backbone of polymer in the process of Stille coupling. By limiting the reaction time, the number-average molecular weight was guaranteed to be lower than 50 kDa. The devices and blend films based on the resultant polymers were characterized by means of external quantum efficiency (EQE), light intensity dependence, mobility, atomic force microscopy (AFM), transmission electron microscopy (TEM), grazing incidence wide-angle X-ray scattering (GIWAXS), etc. In order to study the differences in device performance caused by the different introduction methods, the crown ether was directly added as an additive, and the open-circuit voltage (Voc) and PCE of the device were significantly reduced. However, the device performance was different when the crown ether and the polymer backbone formed a rotaxane structure. Compared with PM6-L, the active layer based on PM6-C2 and Y6 exhibited an optimal fiber-like network structure and better phase separation scale, which contributed to better charge extraction efficiency and reduced trap/bimolecular recombination. Ultimately, more excellent short-circuit current density (Jsc) and fill factor (FF) were obtained because of high charge transport and collection efficiency. Therefore, the PM6-C2-based device achieved a PCE of 16.23%, exceeding that of the PM6-L-based device (15.33%). This work indicates that rotaxane structure is beneficial to improve the active layer morphology and show great potential in developing PSC materials.
A small organic molecule 3Ph-TrH with a rigid structure was designed with π-bridge thienyl and fluorenyl groups as hole trapping sites and the fluorenyl and phenyl units as electron trapping sites according to steric hindrance. Then, the floating gate type organic field-effect transistor (OFET) memories based on this small organic molecule through solution processing were fabricated. The experimental results show that there is a hole storage window of 31.2 V and an electron storage window of 11.6 V in this device, exhibiting ambipolar charge storage based on a single small molecule material. To improve the stability of the device, a floating-gate OFET memory based on 3Ph-TrH with polystyrene (PS)-doped film was further prepared. The test results show that the device is equipped with better device stability and tolerance than those based on 3Ph-TrH as a single-component charge trapping layer. After 10000 s of retention times test, ON/OFF current ratio of the device can still be maintained at 1.1×103, only reduced by an order of magnitude. This work can provide an idea for the preparation of a new type of OFET memory with ambipolar storage.
The production of peroxynitrite (ONOO–) in situations of oxidative stress and inflammation has a profound impact on cellular damage, inflammatory responses, and immune regulation. Thus, the advancement of highly sensitive and selective techniques to detect ONOO– is of great significance. These methods are crucial for gaining insights into disease mechanisms, improving early disease diagnosis, and enhancing treatment effectiveness. In this study, we have designed and synthesized a novel fluorescent probe, NR-Pro, specifically for the selective detection of ONOO–. The probe incorporates a 2-hydroxy Nile red derivative (NR-OH) that is organically bound to a 4,4'-azabediyldiphenol group via an alkyl chain. Upon interaction with ONOO–, the probe releases the near-infrared dye NR-OH, leading to a significant “OFF-ON” fluorescence signal response at 658 nm. The mechanism involves the initial attack of ONOO– on the 4,4'-aza-diyl diphenol group, resulting in the formation of an alkylamine-modified Nile red derivative and the release of two 1,4-benzoquinone molecules. Subsequently, the alkylamine group undergoes further oxidation by ONOO–, leading to the liberation of the near-infrared fluorophore NR-OH and acrolein through a 1,3-elimination reaction with the involvement of water. Experimental investigations have demonstrated that the probe exhibits a favorable linear relationship with ONOO– concentration in the range of 0 to 10 μmol/L, with an exceptionally low detection limit of 17.7 nmol/L. Furthermore, the fluorescence emission of NR-Pro remained unaffected by various biological species, including reactive oxygen species (ROSs), metal ions, enzymes, anions, and amino acids. NR-Pro also exhibited minimal cytotoxicity and very high photostability, suggesting its potential suitability for cell imaging applications. Moreover, our study confirms the remarkable imaging capability of the NR-Pro probe in detecting both exogenous and endogenous ONOO– in RAW264.7 cells. These findings present novel insights for the early diagnosis and treatment of diseases, paving the way for potential advancements in the field.
