Latest ArticlesMicroarray technology has been widely applied in biomedical research. The key to microarray study is to develop efficient immobilization method. In this study, we designed a new reversible microarray immobilization method based on thiol-quinone reaction. A quinone-functionalized slide was fabricated through H2O2 treatment of dopamine-coated slides. Various thiol-containing molecules can be anchored onto the quinone-functionalized slides via thioether linker, which could be cleaved under H2O2 treatment to regenerate quinone groups on the surface. The highly versatile approach can be widely used for immobilization of various thiol-containing molecules.
Unremitting and intensive researches about efficient non-precious metal electrocatalysts are necessary for large-scale commercial applications of fuel cells, while iron and nitrogen co-doped carbon (Fe-N-C) materials has become one of the most promising electrocatalysts to replace Pt-based noble metal catalysts. However, the traditional Fe-doped ZIF with rhomb dodecahedron morphology limits the exposure of active sites and the utilization of atoms, even affecting the performance of the catalyst. Herein, a Fe/N co-doped catalyst with a flower-like morphology was prepared using ferric citrate source along with secondary NH3 heat treatment. The optimal catalyst (termed as 4Fecitrate-N-C-3) showed distinguished oxygen reduction reaction (ORR) activity with a half-wave potential of 0.8 and 0.9 V (vs. RHE) in acid and alkaline media, respectively. In addition, 4Fecitrate-N-C-3 maintained more than 80% of original activity even after 50,000 s which is superior to the benchmark Pt/C. The strategy of controlling morphology and composition is meaningful for the optimization of non-precious metal electrocatalysts for ORR in fuel cells or metal-air batteries.
Colorimetric and fluorescent probes have emerged as a potent tool for pH sensing due to easy operation and high sensitivity. However, most of the existing bimodal probes require complicated synthesis, which greatly limits their wide applications. Herein, a simple fluorescent dye (called BFCUR) featuring a D-π-A-π-D conjugated system was developed from the natural polyphenol curcumin (CUR). BFCUR exhibited significant red-shift in UV absorption and fluorescence emission as pH increased because of the deprotonation of the phenolic hydroxyl groups, which resulted in the enhanced intramolecular charge transfer (ICT). The ratiometric pH detection of BFCUR was achieved with remarkable accuracy by monitoring both the absorbance ratio A500/A650 and the fluorescence intensity ratio I622/I743 under various pH values. In addition, the clear color changes of BFCUR under different pH conditions were visible, which enabled BFCUR to be used in test strips for rapid, visual pH detection. Moreover, BFCUR exhibited low cytotoxicity, and was successfully applied for intracellular pH detection, where the fluorescence intensity was linearly related to pH value. This study highlighted the great potential of CUR-derived BFCUR as colorimetric and fluorescent probes for ratiometric-pH sensing and cell imaging.
Surface oxygen vacancy defects of mesoporous CeO2 nanosheets assembled microspheres (D-CeO2) are engineered by polymer precipitation, hydrothermal and surface hydrogenation strategies. The resultant D-CeO2 with a main pore diameter of 9.3 nm has a large specific surface area (~102.3 m2/g) and high thermal stability. The mesoporous nanosheets assembled microsphere structure prevents the nanosheets from aggregation, which is beneficial to effective mass transfer and shortens the migration distance of charge carriers. After surface hydrogenation, the photoresponse extends to long wavelength region, combing with the band gap from 2.63 eV reduced to 2.39 eV. Under AM 1.5 G radiation, the photocatalytic degradation rate of tetracycline (TC) can be up to 99.99%, which is three times as high as that of pristine CeO2 microspheres. The excellent solar-driven photocatalytic performance can be attributed to the efficient surface oxygen vacancy engineering and the mesoporous nanosheets assembled microsphere structure, which narrows the band gap, shortens the migration distance of carriers, promotes the spatial separation of photogenerated electron-hole pairs and favors mass transfer. The strategy provides new insights for fabricating other high-efficient oxide photocatalysts.
A new metal-oxo-clusters-based inorganic framework [NaCo2Mo2O7(OH)3]n (NaCoMo), named as 3D platelike ternary-oxo-cluster, has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction structure analysis, FT-IR spectroscopy, powder X-ray diffraction (PXRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS) analyses, X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA). Structure analysis reveals that there are no classical building units in NaCoMo, and the asymmetric units of NaCoMo are directly extended into a new platelike 3D structure. Density functional theory calculations (DFT) indicates that the crystal formation process is exothermic and the structure is extremely stable. In addition, the compound presents excellent catalytic activity in the condensation and cyclization reaction of sulfonyl hydrazides and 1, 3-diketones to synthesize pyrazoles, and the yield of the desired product is up to 99%. The successful synthesis of NaCoMo represents the discovery of a new kind of non-classical polyoxometalates.
Designing and developing the highly efficient photocatalysts is full of significance to achieve spontaneous photolysis water. In this work, using the first-principles calculations, we have performed a systematic theoretical study of water splitting photocatalytic activity of the InSe/g-CN heterojunction. It is concluded that the InSe/g-CN heterojunction is a typical type-Ⅱ semiconductor, whose electrons and holes can be effectively separated. And the potential of the conduction band minimum (CBM) and valence band maximum (VBM) satisfy the requirements for photolysis water. Moreover, the changes of Gibbs free energy (ΔG) of the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) are calculated to investigate thermodynamic sustainability of photolysis water. The results show that when pH = 7, the potential driving force provided by the InSe/g-CN heterojunction can ensure the spontaneous progress of HER and OER. In addition, it is found that the solar conversion efficiency (ηS) of the InSe/g-CN heterojunction is up to 13.7%, which indicates it has broad commercial application prospects. Hence, the InSe/g-CN heterojunction is expected to be an excellent candidate for photolysis water.
Metal-semiconductor diodes constructed from two-dimensional (2D) van der Waals heterostructures show excellent gate electrostatics and a large built-in electric field at the tunnel junction, which can be exploited to make highly sensitive photodetector. Here we demonstrate a metal-semiconductor photodiode constructed by the monolayer graphene (Gr) on a few-layer black phosphorus (BP). Due to the presence of a built-in potential barrier (~0.09 ± 0.03 eV) at the Gr-BP interface, the photoresponsivity of the Gr-BP device is enhanced by a factor of 672%, and the external quantum efficiency (EQE) increases to 648% from 84% of the bare BP. Electrostatic gating allows the BP channel to be switched between p-type and n-type conduction. We further demonstrate that excitation laser power can be used to control the current polarity of the Gr-BP device due to photon-induced doping. The versatility of the Gr-BP junctions in terms of electrostatic bias-induced or light-induced switching of current polarity is potentially useful for making dynamically reconfigurable digital circuits.
How to utilize inexhaustible solar light as a means of disinfection technology for its cheap and green remains a challenge. In this work, core-shell ZnO@ZIF-8 was synthesized and used for bacterial inactivation synergizing with peroxymonosulfate (PMS) under visible light irradiation. It took 50 min to achieve thorough sterilization for 7.5-log Escherichia coli (E. coli) cells in vis/PMS/ZnO@ZIF-8 system, compared with that 4.5-log reduction completed in vis/PMS/ZnO system under the same conditions. The enhanced photocatalytic disinfection mechanisms of fabricated ZnO@ZIF-8 were investigated by UV–vis diffuse reflectance spectra, electrochemical impedance spectra and Mott-Schottky plots. The promoted bactericidal efficiency was attributed to higher charge-separation efficiency and stronger oxidation ability of photo-generated holes. Moreover, it was found that 1O2 and •OH induced bacterial cell lesion process, and the former was the main active species. The external reactive oxygen species (ROS) caused a series of cell wall damage, intercellular ROS up-regulation and genome DNA unwinding, finally resulted in irreversible bacterial death. A two-route mechanism in vis/PMS/ZnO@ZIF-8 system was proposed, in which the generation of 1O2 was supposed as the product of the oxygen oxidation of photo-generated holes and PMS dissociation. Our work is expected to provide advanced information about a low-cost water disinfection technology of visible light photocatalysis.
Conversion of methane into liquid alcohol such as ethanol at low temperature in a straight, selective and low energy consumption process remains a topic of intense scientific research but a great challenge. In this work, CuFe2O4/CNT composite is successfully synthesized via a facile co-reduction method and used as catalysts to selectively oxidize methane. At a low temperature of 150 ℃, methane is directly converted to ethanol in a single process on the as-prepared CuFe2O4/CNT composite with high selectivity. A mechanism is also proposed for the significant methane selective oxidation performance of the CuFe2O4/CNT composite catalysts.
Ammonia (NH3) is one of the most important building blocks of the chemical industry and a promising sustainable energy carrier. Conventional production of NH3 via the Haber-Bosch process requires high temperature and high pressure, which is energy demanding and suffers safety issues. Photocatalytic nitrogen reduction reaction (NRR) is a green and sustainable route for NH3 production, and has been expected to be an alternative for NH3 production under mild conditions. However, solar-driven N2 activated has appeared as the bottleneck for photocatalytic NRR. In this work, we propose that single Ru atom supported by BeO monolayer is a promising photocatalytic single atom catalyst (SAC) for efficient N2 activation with visible illumination. The high efficiency originates from the enhanced absorption in the visible range, as well as the back-donation mechanism when N2 were adsorbed on the SAC. Our results show that N2 can be efficiently activated by the Ru/BeO SAC and be reduced to NH3 with extremely low limiting potential of −0.41 V. The NRR process also exhibits dominate selectivity respect to hydrogen evolution.
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