Latest ArticlesThe photocatalytic nitrogen reduction reaction (NRR) has mild reaction conditions and only requires sunlight energy as a driving force to replace the traditional ammonia synthesis method. We herein investigate the catalytic activity and selectivity on Penta-B2C for NRR by using density functional theory calculations. Penta-B2C is a semiconductor with an indirect bandgap (2.328 eV) and is kinetically stable based on molecular dynamic simulations. The optical absorption spectrum of Penta-B2C is achieved in the ultraviolet and visible range. Effective light absorption is more conducive to generate photo-excited electrons and improving photocatalytic performances. Rich B atoms as activation sites in Penta-B2C facilitate capturing N2. The activated N2 molecule prefers the side-on adsorption configuration on Penta-B2C, which facilitates the subsequent reduction reaction. Among considered NRR mechanisms on Penta-B2C, the best pathway prefers the enzymatic mechanism, only required a low onset potential of 0.23 V. The hydrogen evolution reaction is inhibited when the hydrogen adsorption concentration is increased or N2 molecules first occupy the adsorption sites. Our results indicate Penta-B2C is a highly reactive and selective photocatalyst for NRR. Our work provides theoretical insights into the experiments and has guiding significance to synthesize efficient NRR photocatalysts.
n-Alkanes have been widely used as phase change materials (PCMs) for thermal energy storage applications because of their exceptional phase transition performance, high chemical stability, long term cyclic stability and non-toxicity. However, the thermodynamic properties, especially heat capacity, of n-alkanes have rarely been comprehensively investigated in a wide temperature range, which would be insufficient for design and utilization of n-alkanes-based thermal energy storage techniques. In this study, the thermal properties of n-alkanes (C18H38-C22H46), such as thermal stability, thermal conductivity, phase transition temperature and enthalpy were systematically studied by different thermal analysis and calorimetry methods, and compared with previous results. Thermodynamic property of these n-alkanes was studied in a wide temperature range from 1.9 K to 370 K using a combined relaxation (Physical Property Measurement System, PPMS), differential scanning and adiabatic calorimetry method, and the corresponding thermodynamic functions, such as entropy and enthalpy, were calculated based on the heat capacity curve fitting. Most importantly, the heat capacities and related thermodynamic functions of n-heneicosane and n-docosane were reported for the first time in this work, as far as we know. This research work would provide accurate and reliable thermodynamic properties for further study of n-alkanes-based PCMs for thermal energy storage applications.
The development of robust photocatalytic systems is key to harvest the solar power for hydrogen production. In the current study, a series of aluminum-based porphyrinic metal organic frameworks (Al-TCPP) with various morphologies of bulk, carambola-like and nanosheets are synthesized with modulated layer thickness. Morphology-dependent photocatalytic activities in hydrogen production are witnessed and inversely correlate to the thickness of the Al-TCPP micro-platelets or nanosheets. Particularly, the exfoliated metal organic layers (MOLs) of Al-TCPP demonstrated a high hydrogen yield rate of 1.32 × 104 µmol h−1 g−1 that is 21-fold of that from the bulk catalyst, as well as an exceptional TON of 6704 that seldom seen in literature. Through comprehensive photochemical characterizations, the remarkable photocatalytic performance of Al-TCPP-MOL is attributed to the great charge separation efficiency and transfer kinetics endowed by the ultrathin 2D morphology with extended active surface area.
A HAT based large PAH discotic molecule PN8 is developed. The enlarged chromophoric core and doping heteroatoms enable colorimetric and fluorometric sensing of Cu2+ and Zn2+ with highly appreciable optical changes, good selectivity and low detection limit. Moreover, PN8 was demonstrated as an excellent adsorbent to remove Cu2+ and Zn2+ from wastewater.
Inducing ferromagnetism into graphene is vital today because it has a wide range of applications such as spintronics devices and magnetic memory devices. In this paper, we will report a new method to synthesize ferromagnetic graphene by nitrogen doping. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy were utilized to testify the N-doped material and further discuss the N-doped process. The superconducting quantum interference device (SQUID) was put in and used to analyze the magnetic properties of the N-doped graphene sheets. It shows that the material exhibits ferromagnetism at both 3 K and 300 K and the ferromagnetic saturation moment is 0.412 emu/g and 0.051 emu/g, respectively. The mechanism of the origin of the ferromagnetism in N-doped graphene sheets will also be discussed in this paper. It shows that, when the amount graphitic N reached the threshold, the origin of the ferromagnetism will change from defects induced by nitrogen atoms to the transition in energy band caused by graphitic N.
P-doping is an effective way to modulate the electronic structure and improve the Na+ diffusion kinetics of TiO2, enabling enhanced electrochemical performance. However, it is a challenge to prepare TiO2 with a high P-doping concentration starting from TiO2 in a crystalline state. In this work, we design a novel two-step route for constructing a carbon-coated anatase P-doping TiO2 nanospheres (denote as (P-AnTSS)@NC) with high P-doping concentration, by utilizing amorphous TiO2 nanospheres with the ultra-high specific area as P-doping precursor firstly, and followed by carbon coating treatment. Experimental results demonstrate that P is successfully doped into the crystal lattice and carbon layer is well coated on the surface of TiO2, with P-doping and carbon-coating contents of ~13.5 wt% and 10.4 wt%, respectively, which results in the enhanced pseudocapacitive behavior as well as favorable Na+ and electron transferring kinetics. The (P-AnTSS)@NC sample shows excellent rate and cycle performance, exhibiting specific capacities of 177 and 115 mAh/g at 0.1 and 1.0 A/g after 150 and 2000 cycles, respectively.
Surface deposition based on metal-phenolic networks (MPNs) has received increasing interest in recent years. The catechol structure is generally considered to be essential to the formation of MPNs. Our most recent results have demonstrated that some kinds of monophenols can form MPNs on substrate surfaces. Herein, we report a fast and effective surface-coating system based on the coordination of 3-(4-hydroxy-3-methoxyphenyl)-2-propenoic acid, a kind of monophenol, with Fe3+. Compared with other metal ions such as Cu2+ and Ni2+, Fe3+ with stronger electron acceptability can coordinate with the monophenol more strongly to form MPNs, and moreover, the deposition time significantly decreases to 40 min from generally 24 h. It is demonstrated that the deposition process is controlled by the coordination, Fe3+ hydrolysis, and deprotonation of the monophenol. The coatings endow substrates such as polypropylene microfiltration membrane with underwater superoleophobicity, which can be applied in oil/water separation with high separation efficiency and great long-term stability. In addition, the coated membranes are positively charged and thus are useful in selective adsorption of dyes. The present work not only provides a novel, fast, and one-step deposition method to fabricate MPNs, but also demonstrates that the fabrication efficiency of monophenol-based MPNs is comparable with that of polyphenol-based MPNs.
Introduction of iodosylarnes into biomimetic nonheme chemistry has made great achievement on identification of the subtle metal-oxygen reaction intermediates. However, after more than three decades of experimental and theoretical efforts the nature of the metal-iodosylarene adducts and the related dichotomous one-oxidant/multiple-oxident controversy have remained a matter of speculation. Herein, we report a theoretical study of the structure-activity relationship of the noted iron(Ⅲ)-iodsylarene complex, FeⅢ(PhIO)(OTf)3 (1), in oxygenation of cyclohexene. The calculated results revealed that 1 behaves like a chameleon by adapting its roles as a 2e-oxidant or an oxygen donor, as a response to the regioselective attack of the C–H bond and the C=C bond. The oxidative C–H bond activation by 1 was found, for the first time, to proceed via a novel hydride transfer process to form a cyclohexene carbonium intermediate, such non-rebound step triggers the Ritter reaction to uptake an acetonitrile molecule to form the amide product, or proceeds with the rebound of the hydroxyl group return to the solvent cage to form the hydroxylated product. While in the C=C bond activation, 1 is a normal oxygen donor and shows two-state reactivity to present the epoxide product via a direct oxygen atom transfer mechanism. These mechanistic findings fit and explain the famous Valentine's experiments and enrich the non-rebound scenario in bioinorganic chemistry.
Spontaneously blinking probe, which switches between dark and bright state without UV or external additives, is extremely attractive in super resolution imaging of live cells. Herein, a clickable rhodamine spirolactam probe, Atto565-Tet, is rationally constructed for spontaneously blinking after biorthogonal labelling and successfully applied to super resolution imaging of mitochondria and lysosomes.
Novel xanthenoid dyes by replacing the central oxygen atom of the xanthene dyes with less electron-rich bridging groups have been intensively sought after primarily for their long spectral wavelengths. However, the new scaffolds are likely prone to nucleophilic attack at their central methane carbon, as the result of the reduced electron density of the fluorochromic scaffolds. We envisage that the bridging group may be harnessed to sterically shield the central methane carbon from incoming nucleophiles and render high stability and synthesized xantheno-xanthene dyes. Additionally, the xantheno-bridging group can be modified via electrophilic aromatic substitution to introduce functionalities, e.g., sulfonate groups.
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