An in situ strategy was introduced for synthesizing carbon modified graphitic carbon nitride(g-C3N4) by using urea/4-aminobenzoic acid(PABA) co-crystal(PABA@Urea) as precursor materials. Via co-calcination of the PABA co-former and the urea in PABA@Urea co-crystals, C guest species were generated and compounded into g-C3N4 matrix in situ by replacing the lattice N of the carbon nitride and forming carbon dots onto its layer surface. The carbon modification dramatically enhanced visible-light harvesting and charge carrier separation. Therefore, visible light photo-catalytic oxidation of methylene blue(MB) pollution in water over the carbon modified g-C3N4(C/g-C3N4) was notably improved. Up to 99% of methylene blue(MB) was eliminated within 60 min by the optimal sample prepared from the PABA@Urea co-crystal with a PABA content of 0.1%(mass ratio), faster than the degradation rate over bare g-C3N4. The present study demonstrates a new way to boost up the photocatalysis performance of g-C3N4, which holds great potential concerning the degradation of organic dyes from water. 相似文献
Solid-state NMR analysis on wurtzite alloyed CdSe1−xSx crystalline nanoparticles and nanobelts provides evidence that the 113Cd NMR chemical shift is not affected by the varying sizes of nanoparticles, but is sensitive to the S/Se anion molar ratios. A linear correlation is observed between 113Cd NMR chemical shifts and the sulfur component for the alloyed CdSe1−xSx (0<x<1) system both in nanoparticles and nanobelts (δCd=169.71⋅XS+529.21). Based on this correlation, a rapid and applied approach has been developed to determine the composition of the alloyed nanoscalar materials utilizing 113Cd NMR spectroscopy. The observed results from this system confirm that one can use 113Cd NMR spectroscopy not only to determine the composition but also the phase separation of nanomaterial semiconductors without destruction of the sample structures. In addition, some observed correlations are discussed in detail. 相似文献
It is known that the kinetics of redox reactions occurring on the surfaces of passive metals depend upon the properties of the passive film, ostensibly due to quantum mechanical tunnelling (QMT) of electrons and holes between the metal and the redox couple at the barrier layer/solution (bl/s) interface. In this paper, the tunnelling probability is used to inter-convert the exchange current densities for the redox reactions occurring at the bl/s interface and on the hypothetical bare metal surface. We review our previous work on combining QMT theory with the point defect model (PDM), which provides an analytical expression for the bl thickness as a function of voltage. By combining QMT theory and the PDM, we derive a modified form of the generalized Butler-Volmer equation that requires as input only the kinetic parameters for the redox reaction on the hypothetical bare surface and parameters contained in the PDM. The application of the theory is illustrated with reference to the corrosion of carbon steel in concrete pore solution, to calculating the corrosion potential of, and crack growth rate in, sensitized type 304 SS in boiling water reactor (BWR) coolant circuits, and the use of hydrogen oxidation on platinum to determine the thickness of the bl as a function of voltage and temperature. This illustrates a new, powerful technique for probing the formation of passive films on metal surfaces.
Fluorescent materials exhibiting two‐photon induction (TPI) are used for nonlinear optics, bioimaging, and phototherapy. Polymerizations of molecular chromophores to form π‐conjugated structures were hindered by the lack of long‐range ordering in the structure and strong π–π stacking between the chromophores. Reported here is the rational design of a benzothiadiazole‐based covalent organic framework (COF) for promoting TPI and obtaining efficient two‐photon induced fluorescence emissions. Characterization and spectroscopic data revealed that the enhancement in TPI performance is attributed to the donor‐π‐acceptor‐π‐donor configuration and regular intervals of the chromophores, the large π‐conjugation domain, and the long‐range order of COF crystals. The crystalline structure of TPI‐COF attenuates the π–π stacking interactions between the layers, and overcomes aggregation‐caused emission quenching of the chromophores for improving near‐infrared two‐photon induced fluorescence imaging. 相似文献
A conjugated copper(II) catecholate based metal–organic framework (namely Cu‐DBC) was prepared using a D2‐symmetric redox‐active ligand in a copper bis(dihydroxy) coordination geometry. The π‐d conjugated framework exhibits typical semiconducting behavior with a high electrical conductivity of ca. 1.0 S m?1 at room temperature. Benefiting from the good electrical conductivity and the excellent redox reversibility of both ligand and copper centers, Cu‐DBC electrode features superior capacitor performances with gravimetric capacitance up to 479 F g?1 at a discharge rate of 0.2 A g?1. Moreover, the symmetric solid‐state supercapacitor of Cu‐DBC exhibits high areal (879 mF cm?2) and volumetric (22 F cm?3) capacitances, as well as good rate capability. These metrics are superior to most reported MOF‐based supercapacitors, demonstrating promising applications in energy‐storage devices. 相似文献
Inhibition of TICT can significantly increase the brightness of fluorescent materials. Accurate prediction of TICT is thus critical for the quantitative design of high‐performance fluorophores and AIEgens. TICT of 14 types of popular organic fluorophores were modeled with time‐dependent density functional theory (TD‐DFT). A reliable and generalizable computational approach for modeling TICT formations was established. To demonstrate the prediction power of our approach, we quantitatively designed a boron dipyrromethene (BODIPY)‐based AIEgen which exhibits (almost) barrierless TICT rotations in monomers. Subsequent experiments validated our molecular design and showed that the aggregation of this compound turns on bright emissions with ca. 27‐fold fluorescence enhancement, as TICT formation is inhibited in molecular aggregates. 相似文献
A rhodium‐catalyzed remote C(sp3)?H borylation of silyl enol ethers (SEEs, E/Z mixtures) by alkene isomerization and hydroboration is reported. The reaction exhibits mild reaction conditions and excellent functional‐group tolerance. This method is compatible with an array of SEEs, including linear and branched SEEs derived from aldehydes and ketones, and provides direct access to a broad range of structurally diverse 1,n‐borylethers in excellent regioselectivities and good yields. These compounds are precursors to various valuable chemicals, such as 1,n‐diols and aminoalcohols. 相似文献
An enantioselective aldehyde α‐alkylation/semipinacol rearrangement was achieved through organo‐SOMO catalysis. The catalytically generated enamine radical cation serves as a carbon radical electrophile that can stereoselectively add to the alkene of an allylic alcohol and initiate ensuing ring‐expansion of cyclopropanol or cyclobutanol. This tandem reaction enables the production of a wide range of nonracemic functionalizable α‐quaternary‐δ‐carbonyl cycloketones in high yields and excellent enantioselectivity from simple aldehydes and allylic alcohols. As a key step, the intramolecular reaction was also successfully applied in the asymmetric total synthesis of (+)‐cerapicol. 相似文献
The simultaneous promotion in mechanical and electrical properties of rigid polyurethane (RPU) is an important task for expanding potential application. In this work, carbon fibers (CFs) reinforced RPU composites were prepared with the goal of improving mechanical and electrical properties. Metallized CFs meet our performance requirements and can be easily achieved via electrodeposition. However, the weak bonding strength in fiber‐metal‐RPU interface restricts their application. Inspired by the reducibility and wonderful adhesion of dopamine (DA), we proposed a new and efficient electrochemical method to fabricate metallized CFs, where DA polymerization was simultaneously integrated coupled with the reduction of metal ions (Ni2+). The characterization results helped us to gain insight about the reaction mechanism, which was never reported as far as we know. Compared with pure RPU, the tensile, interlaminar shear and impact strength of polydopamine (PDA)‐nickel (Ni) modified CFs/RPU composites were improved by 11.2%, 21.0%, and 78.0%, respectively, which attributed to the strong interfacial adhesion, including mechanical interlocking and chemical crosslinking between treated CFs and RPU. In addition, the PDA‐Ni surface treatment method also affected the dispersion of short CFs in the RPU, which increased the possibility of conductor contact and reduced insulator between fibers networks, resulting in higher electrical conductivity. 相似文献