Search

The graphitic nitrogen carbide/alpha-iron oxide (g-C3N4/ $\alpha $ -Fe2O3) nanostructure is prepared by hydrothermal method. The g-C3N4/ $\alpha $ -Fe2O3 hybrid was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray (XRD). The hybrid material was deposited over interdigital sensing electrodes on a PET substrate. The prepared sensor exhibited excellent response characteristics for detecting H2S gas, which was superior than that of pure $\alpha $ -Fe2O3 counterpart. The detection limit of the sensor for H2S gas is 0.5 ppm at room temperature. Moreover, the g-C3N4/ $\alpha $ -Fe2O3sensor has a higher selectivity over the interference gas species of SO2F2, CO, and SO2. The results suggest that the $\alpha $ -Fe2O3 sensor is a good candidate for sensing decomposed SF6 products in environ and healthcare fields.

The application of low-powered, sustainable sensors to detect the leak of toxic gases in factories has gradually become a future trend. In our work, we proposed a NO2 gas sensor based on an In2O3/SnS2 composite powered by a high-stability triboelectric nanogenerator (TENG), where weighing paper and a polytetrafluoroethylene (PTFE) film were used as friction materials. The peak-to-peak voltage of the TENG can reach stable 600 V and the output power can up to 13 mW, which exhibits superior performance. The TENG can power small portable electronic devices such as 50 LEDs and calculators. The TENG is directly connected in series with a chemoresistive gas sensor to form a TENG-driven nitrogen dioxide sensor (TENS) for the spontaneous detection of the concentration of NO2. The sensor exhibits a high response (∼15) and rapid response/recovery time (45 s/147 s) towards 50 ppm NO2 at 43% RH and room temperature of 25 °C. Finally, a self-powered alarm system based on the TENS has been developed to monitor the concentration of NO2 in the surrounding environment. This work not only broadens the application field of the TENG as a self-powered gas sensor, but also meets the requirements of industrial IoT technology for miniaturized, low-powered, and maintainable sensors.

Traumatic peripheral nervous system (PNS) injuries currently lack suitable treatments to regain full functional recovery. Schwann cells (SCs), as the major glial cells of the PNS, play a vital role in promoting PNS regeneration by dedifferentiating into a regenerative cell phenotype following injury. However, the dedifferentiated state of SCs is challenging to maintain through the time-period needed for regeneration and is impacted by changes in the surrounding extracellular matrix (ECM). Therefore, determining the complex interplay between SCs and differing ECM to provide cues of regenerative potential of SCs is essential. To address this, a strategy was created where different ECM proteins were adsorbed onto a tunable polydimethylsiloxane (PDMS) substrate which provided a platform where stiffness and protein composition can be modulated. SCs were seeded onto the tunable substrates and critical cellular functions representing the dynamics of SC phenotype were measured. To illustrate the interplay between SC protein expression and cellular morphology, differing seeding densities of SCs in addition to individual microcontact printed cellular patterns were utilized and characterized by immunofluorescence staining and western blot. Results showed that cells with a smaller spreading area and higher extent of cellular elongation promoted higher levels of SC regenerative phenotypic markers. This methodology not only begins to unravel the significant relationship between the ECM and cellular function of SCs, but also provides guidelines for the future optimization of biomaterials in peripheral nerve repair.

In this paper, a new plasma spray technology working in low pressure condition has been successfully applied to deposit Lix(Ni,Co)yO2 catalyst/electrode layers for low-temperature solid oxide fuel cells (LT-SOFCs). The low pressure induced distinctive phenomena were illustrated for presenting the characteristics and advances of such coating technique. Micro-nano crystalline microstructure was generated on the plasma sprayed coatings simultaneously with phase transformation taking place. To study the effect of high temperature on such catalyst material, sintering experiments were carried out at 600–1000 °C. The results show that the ratio of x/y decreased when increasing temperature and sintering time because of the degradation of Li from Lix(Ni,Co)yO2 phase. The catalytic property and stability of the Lix(Ni,Co)yO2 at various temperatures were also discussed.

Peripheral nerve injuries require a complex set of signals from cells, macrophages, and the extracellular matrix (ECM) to induce regeneration across injury sites and achieve functional recovery. Schwann cells (SCs), the major glial cell in the peripheral nervous system (PNS), are critical to nerve regeneration due to their inherent capacity for altering phenotype postinjury to facilitate wound healing. The ECM plays a vital role in wound healing as well as regulating cell phenotype during tissue repair. To examine the underlying mechanisms between the ECM and SCs, this work sought to determine how specific ECM cues regulate the phenotype of SCs. To address this, SCs were cultured on polydimethylsiloxane substrates of a variable Young's modulus coated with ECM proteins. Cells were analyzed for spreading area, proliferation, cell and nuclear shape, and c-Jun expression. It was found that substrates with a stiffness of 8.67 kPa coated with laminin promoted the highest expression of c-Jun, a marker signifying a "regenerative" SC. Microcontact printed, cell adhesive areas were then utilized to precisely control the geometry and spreading of SCs and by controlling spreading area and cellular elongation; expression of c-Jun was either promoted or downregulated. These results begin to address the significant interplay between ECM cues and phenotype of SCs, while offering a potential means to enhance PNS regeneration through cellular therapies.

Large-size, superparamagnetic, and highly magnetic Fe3O4@PDA core−shell submicrosphere-supported nano-palladium catalysts were prepared in this study. Dopamine was encapsulated on the surface of Fe3O4 particles via self-polymerization and then protonated to positively charge the microspheres. PdCl42− was dispersed on the surface of the microspheres by positive and negative charge attraction and then reduced to nano-palladium. With air as oxidant, the catalyst can successfully catalyze the dehydrogenation of benzyl alcohols to produce the corresponding aldehydes at 120 °C.

Schwann cells (SCs) are a highly plastic cell type capable of undergoing phenotypic changes following injury or disease. SCs are able to upregulate genes associated with nerve regeneration and ultimately achieve functional recovery. During the regeneration process, the extracellular matrix (ECM) and cell morphology play a cooperative, critical role in regulating SCs, and therefore highly impact nerve regeneration outcomes. However, the roles of the ECM and mechanotransduction relating to SC phenotype are largely unknown. Here, we describe the role that matrix stiffness and cell morphology play in SC phenotype specification via known mechanotransducers YAP/TAZ and RhoA. Using engineered microenvironments to precisely control ECM stiffness, cell shape, and cell spreading, we show that ECM stiffness and SC spreading downregulated SC regenerative associated proteins by the activation of RhoA and YAP/TAZ. Additionally, cell elongation promoted a distinct SC regenerative capacity by the upregulation of Rac1/MKK7/JNK, both necessary for the ECM and morphology changes found during nerve regeneration. These results confirm the role of ECM signaling in peripheral nerve regeneration as well as provide insight to the design of future biomaterials and cellular therapies for peripheral nerve regeneration.

Diversiform sensors and sensing devices with high reliability and self-powered features are critical in future wearable and flexible electronics of various fields. As a new energy harvesting technology, nanogenerator represented by triboelectric nanogenerator (TENG) and piezoelectric nanogenerator (PENG) has attracted wide attention because it can effectively utilize renewable energy. Self-powered sensing technology based on TENG and PENG has been greatly developed because of its advantages over traditional power supply technology. The recent progress of TENG and PENG as self-powered smart sensors or power supply of sensing systems for a variety of applications has comprehensively summarized, such as environmental monitoring, biomedical application, and human–machine interface system. The latest achievements are also systematically reviewed from the aspects of advanced triboelectric/piezoelectric materials, implementation performance and prospective applications. The development of emerging nanomaterials makes TENG and PENG exhibit great application potential in the fields of nano-power sources, self-powered nano-devices, and micro-implantable chips. Moreover, some insights about future development trends and challenges of TENG and PENG in sensing fields were put forward. Triboelectric and piezoelectric nanogenerator has great prospective applications for the micro/nano energy and self-power of diversiform sensors and sensing systems as an emerging technology.

Fucoidan, a type of sulfated polysaccharide known for its anticoagulant, anti-tumor and anti-inflammatory effects, has been reported to have strong affinity towards P-selectin. P-selectin, which plays an important role in metastasis by enhancing the adhesion of cancer cells to endothelium and activated platelets in distant organs, is overexpressed on many cancer types. This study demonstrates the synthesis of a fucoidan-based drug delivery system for minimizing the side effects of doxorubicin (Dox) with the help of active targeting toward P-selectin. Fucoidan-doxorubicin nanoparticles (FU-Dox NPs), developed by direct conjugation of Dox to the fucoidan backbone, showed a well-controlled size distribution and sustained release. The active targeting capability of FU-Dox NPs toward P-selectin resulted in enhanced cellular uptake and cytotoxicity against the MDA-MB-231 cell line with high P-selectin expression compared to the MDA-MB-468 cell line with low P-selectin expression.

A novel method is developed for the enantioselective synthesis of highly functionalized 3,4-disubstituted dihydro-2(1H)-quinolinones bearing two trans contiguous stereogenic centers with excellent diastereoselectivities (up to >99 : 1 dr) and high to excellent enantioselectivities (up to >99% ee). The process combines an enantioselective organocatalytic Michael–hemiaminalization reaction and a highly efficient oxidation reaction sequence with good yields and stereoselectivity.

An organocatalytic Michael reaction of cycloheptanone and cyclooctanone with nitrodienes and nitroolefins catalyzed by a hydroquinine-based primary amine catalyst has been accomplished. The corresponding Michael adducts were obtained in good yields (up to 88%) with good to excellent diastereoselectivities (up to >100 : 1) and enantioselectivities (up to >99% ee). The absolute configuration of the Michael product was assigned by TDDFT simulation of the ECD spectrum. And the Michael products can be readily converted into analogues of cycloalkano[b] fused pyrrolidines.

Flexible self-powered humidity sensors with high response and good flexibility have attracted extensive interest in wearable electronics, motion monitoring and personal healthcare. In this work, we reported a high-performance flexible tin disulfide nanoflowers/reduced graphene oxide (SnS2/RGO) nanohybrid-based humidity sensor driven by a poly(tetrafluoroethylene) triboelectric nanogenerator (TENG). The humidity sensitive film of SnS2/RGO was screen-printed on a flexible PET substrate with Au interdigital electrodes. The TENG has a peak-to-peak voltage of 500 V and maximum output power of 378 μW. The tribotronic constant voltage source is achieved by integrating TENG with voltage rectifier and stabilizer circuits to steadily power the humidity sensor. The performance of the self-powered triboelectric humidity sensor (TEHS) at different humidity levels was systematically investigated, which exhibits high steady output voltage (0–24 V), fast response/recovery time (4 s/3 s for 33%RH, 6 s/15 s for 97%RH), wide sensing range (0–97%RH), great stability, and ultralow power consumption (29.78 μW). Furthermore, the TEHS demonstrated the potential ability of monitoring human breath with differ frequency, human cough, and finger approach in various applications for humidity sensing. This work provides a novel thought to design the self-powered humidity sensor, and also proposes the promising applications of TENG for the self-powered electronic devices.

A Cu(0)/Selectfluor system-mediated oxidative cyclization of 1,5-enynes with concomitant C-C bond cleavage to access 3-formyl-1-indenone derivatives is described. Preliminary mechanistic investigations disclosed that the C-C bond cleavage involved a novel water-participated oxygen-insertion β-carbon elimination through double oxycuprations.

The reaction allows the formation of xanthenones and chromans with three contiguous stereocenters with high to excellent enantioselectivity and moderate to mostly excellent diastereoselectivity.

A combination of copper powder and Selectfluor permits the generation of cationic copper species that efficiently catalyze 1,2-dicarbonylation of alkynes under mild conditions with water and dioxygen as inexpensive and environmentally benign sources of oxygen.

A gold(I)-catalyzed oxidative diketonization of alkynes by water in the presence of Selectfluor has been achieved. The application of the present protocol for the one-pot synthesis of quin­oxaline derivatives from alkynes and o-phenylenediamines has also been successful.

A K(2)S(2)O(8)-mediated direct cross-coupling of quinoxalines (or benzothiazoles) with methanol leading to 2-quinoxalinyl (or 2-benzothiazolyl) carbaldehyde dimethyl acetals has been achieved. 2-Quinoxalinyl carbaldehyde dimethyl acetals were readily converted into 2-quinoxalinyl carbaldehydes in good to excellent yields under acidic conditions. Preliminary mechanistic studies suggest that the reaction proceeds via multifold bond cleavage and formation between methanol and N-heterocycles involving a dioxygen-participated radical process. This method allows for the synthesis of a variety of 2-quinoxalinyl (or 2-benzothiazolyl) carbaldehyde dimethyl acetals directly via cross-coupling of simple N-heterocyclic C-H bond and methanol under aldehyde-, acid-, and transition-metal-free conditions.

An approach for the synthesis of fluorinated indene derivatives has been developed via a gold-catalyzed three-component tandem reaction between allene esters, Selectfluor, and water.

A mild and efficient protocol for the synthesis of fluorinated pyrazoles has been developed via gold(I)-catalyzed tandem aminofluorination of alkynes in the presence of Selectfluor. This method offers a broad substrate scope.

The first highly enantioselective organocatalytic Michael addition of 4-hydroxycoumarins is reported.

An efficient and highly selective approach for the synthesis of functionalized 4H-chromenes has been developed via gold(III)-catalyzed condensation/annulation tandem reaction of ketones with phenols.

Either [1,3]- or [3,3]-sigmatropic rearrangements were selectively accessed by controlling the reaction temperature in the gold(III)-catalyzed tandem rearrangement/cyclization of (E)-2-(aryloxymethyl)alk-2-enoates to afford diversely substituted 3,4-dihydrocoumarin derivatives in moderate to good yields and in excellent regioselectivity.

Today gold is without a doubt the “star metal” in chemistry because of the focus of attention on gold-catalyzed organic transformations in recent years. 1 , 2 , 3 , 4 , 5 , 6 , 7 Among various new ...

Tiefsee-Diels-Alder-Reaktion: Die asymmetrische organokatalytische Diels-Alder-Reaktion zwischen Cyclohexenonen und aromatischen Nitroolefinen gelingt in Meerwasser und gesattigter Kochsalzlosung. Die Reaktion verlauft als saurekatalysierte Enaminaktivierung uber eine einstufige konzertierte Addition (siehe Schema).

Efficient and stereoselective rearrangement catalyzed by only one mole-percent gold(I) chloride/silver(I) trifluoromethanesulfonate of Baylis-Hillman acetates afforded 2-(acetoxymethyl)alk-2-enoates under mild reaction conditions in good to high yields with 100% E-selectivity. For cyclohex-2-enone-derived Baylis-Hillman acetates, the reaction gave 2-alkylidenecyclohex-3-enones in good yields.

An enantioselective oxa-Michael-Henry reaction of substituted salicylaldehydes with nitroolefins that proceeds though an aromatic iminium activation (AIA) has been developed by using a chiral secondary amine organocatalyst and salicylic acid as a co-catalyst. The corresponding 3-nitro-2H-chromenes were obtained in moderate-to-good yields with up to 91% ee under mild conditions. Based on the experimental results and ESI-mass spectrometric detection of the intermediates, a plausible transition state has been proposed to explain the origin of the activation and the asymmetric induction.

A series of trisubstituted alkenes containing (Z)-allylthio moieties as key structural units, that is, sodium (Z)-allyl thiosulfates, symmetrical di(Z-allyl) sulfides, and di(Z-allyl) disulfides, unsymmetrical diallyl sulfides were prepared in moderate to good yields via chemical transformations from the acetates of Baylis--Hillman adducts. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:188–198, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20394

The direct asymmetric Michael addition of ketones to nitroolefins catalyzed by 2-[(imidazol-2-ylthio)methyl]pyrrolidine, constructed from natural L-proline and imidazolylthio platforms, with salicylic acid as a co-catalyst has been developed to give the products in high yields (up to 95 %) and with excellent enantioselectivities (up to 99 % ee). The highly efficient catalytic performance may be attributed to the dual activation of the Michael substrates by the trifunctional organocatalysts and the co-catalyst salicylic acid, leading to the formation of a stable transition state complex through the synergic effect of hydrogen-bonding and electrostatic interactions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Selective formation of (2E)‐2‐methylalk‐2‐enoates or 2‐methyl alkanoates could be achieved in moderate to good yields under mild conditions via Sm/HOAc/EtOH system–mediated reduction of Baylis–Hillman acetates depending on the amount of samarium consumed in the reactions.

Benzene is nitrated by a novel atom‐economic nitration procedure with a NO2‐O2 system in the presence of a mixture of solid oxides and Ln(OTf)3. The only by‐product in this novel method is water. The efficiency of NO2 is much high than 50%, the theoretical efficiency of NO2 of the known methods. Among the solid oxides and Ln(OTf)3 studied, HZSM‐5 and Sm(OTf)3 were the most efficient catalysts in this process. Therewith, the yield of the benzene nitration reached 72.5%, calculated by NO2.

A novel class of pyrrolidine–pyridinium based organocatalysts has been developed and demonstrated to efficiently catalyze the asymmetric Michael addition reactions of unmodified cyclohexanone to nitroalkenes in the ionic liquid BMImBF 4 with up to 95% yield and nearly 100% ee. The catalytic system could be reused for four times and still retained high enantioselectivity. X-ray crystallographic analysis results suggested that a sterically hindered pyridinium moiety on the catalyst played an important role in the chiral induction.

2-(2,2,2-Trichloroethyl)alk-2-enoates could be formed in good E-selectivity by the reductive coupling of Baylis-Hillman acetates with tetrachloromethane in good 76-92% yields in the presence of catalytic Al/PbCl 2 and DMF.

Catalyzed by ytterbium(III) triflate, asymmetrical carbonate can be chemoselectively synthesized from alcohols and dimethyl carbonate (DMC) in moderate to good yield under the mild conditions.

A concise synthesis of highly functionalized dihydroquinolinones with excellent diastereoselectivities and enantioselectivities by sequential organocatalytic Michael—hemiaminalization/oxidation reactions under mild reaction conditions is presented.

Michael adducts [(III) and (V)] are synthesized in good yields and high enantioselectivities using a hydroquinine-based primary amine as catalyst.

A series of 4‐arylidene‐2‐phenyl‐5(4)‐oxazolones were synthesized from cyclodehydration–condensation of hippuric acid, aromatic aldehydes, and acetic anhydride catalyzed by ytterbium(III) triflate under mild conditions in excellent yields.

Imidazolium-supported-pyrrolidine-catalyzed asymmetric Michael addition reactions of unmodified ketones and aldehydes to nitroalkenes were performed in [BMIm]PF 6 to give products in up to 98% yield and 99% enantioselectivity. The catalytic system presented a synergistic effect in the improvement of reaction performance and could be recycled.

A novel class of chiral-amine-functionalized ionic liquids (CAFILs) has been synthesized efficiently from natural amino acids, and their structures have been determined by spectroscopic analysis and low temperature X-ray diffraction analysis. The CAFILs have been characterized by physical properties such as melting point, glass transition temperature, thermal degradation and specific rotation. NMR measurements indicate that the CAFILs may be promising alternatives in the field of chiral discrimination.

A facile and stereoselective synthesis of unsymmetrical diallylsulfides was achieved in moderate to good yields via indium-promoted one-pot reaction of Baylis-Hillman acetates, sodium thiosulfate, and allyl bromide.

Ionic liquids (ILs) were for the first time found to be alternatively excellent media for the heterogeneously catalyzed hydrogenation of halonitrobenzenes to corresponding haloanilines over three type catalysts of Raney nickel, carbon-supported platinum and palladium. The ionic liquids give rise to higher selectivity and lower dehalogenation in the hydrogenating process compared with that observed in conventional organic solvents.

A novel selective fluorination reaction of aromatic and olefinic ketoximes is developed using NSFI as fluorine source in the presence of a Pd-catalyst and KNO3 or AgNO3 as co-catalyst.

A novel water-induced oxygen-insertion/β-carbon elimination via double oxy-cupration is proposed to be involved in the C—C bond cleavage step.

The reaction allows the formation of xanthenones and chromans with three contiguous stereocenters with high to excellent enantioselectivity and moderate to mostly excellent diastereoselectivity.

A novel and facile C-H bond fluorination proceeds under remarkably mild conditions (close to room temperature in most cases). Both aromatic and olefinic C(sp(2))-H bonds with a wide range of electronic properties are selectively fluorinated in the presence of a catalytic amount of simple, cheap, and nontoxic nitrate as the promoter. A Pd(II)/Pd(IV) catalytic cycle that is initiated by an in situ generated cationic [Pd(NO3)](+) species was proposed based on preliminary mechanistic studies.