Ju Xie

Synergistically enhanced electrochemical response of host-guest recognition based on ternary nanocomposites: reduced graphene oxide-amphiphilic pillar[5]arene-gold nanoparticles.

An amphiphilic pillar[5]arene (AP5) was modified onto the surface of reduced graphene oxide (RGO) to form the water-dispersive RGO-AP5 nanocomposite. And then, as-prepared gold nanoparticles (AuNPs) self-assembled onto the surface of RGO-AP5 through amido groups of AP5 to achieve RGO-AP5-AuNPs nanocomposites. It was verified that a large amount of AP5 molecules had been effectively loaded onto the surface of RGO and lots of AuNPs could be uniformly dispersed on RGO-AP5. Electrochemical results showed that the RGO-AP5 could exhibit selective supramolecular recognition and enrichment capability toward guest molecules. More significantly, in electrochemical sensing the guest molecules, ternary nanocomposites RGO-AP5-AuNPs performed the synergetic action of multifunctional properties, which were excellent performances of RGO, selective supramolecular recognition, and enrichment capability of AP5 and catalytic property of AuNPs for guest molecules. Therefore, RGO-AP5-AuNPs showed an outstanding analyzing performance for DA with broad linear range (1.5 × 10(-8) to 1.9×10(-5) M) and low detection limit (1.2 × 10(-8) M) at a signal-to-noise ratio of 3.

Theoretical study on the ion–pair recognition of Na+/X− (X = F− , Cl− , Br− ) by urea calix[4]bis crown-3 derivative

The structure of tetraurea calix[4]bis crown-3 derivative (Ht) and its complexes with ion–pair Na+/X− (X = F− , Cl− , Br− ) were studied using quantum mechanical (QM) methods (at the B3LYP/6-31G(d,p) level) and molecular dynamics (MD) simulations under various conditions. Two types of complexes (host-separated type (S) and contact type (C)) were found based on QM calculations in the gas phase. The ion-binding sites in Ht, the interaction forces between Na+/X− and Ht and the recognition selectivity for ion pairs were discussed in detail. In the case of host-separated type (S), the MD simulation results showed that the halogen anion gradually broke away from the host molecule in water. However, the anion got into the calix[4]arene subunit and interacted with sodium cation in chloroform solvent. For the contact type, anion and cation were always embraced by the host molecule during a 1-ns simulation both in water and chloroform. These results indicated that Ht could be a potential selective ion–pair receptor, and the QM+MD strategy could provide reasonable descriptions for ion–pair recognitions.

Theoretical study on ion-pair recognition of M(+)X(-) (M = Li, Na, K and X = F, Cl, Br) by formylaminocalix[4]arene derivatives.

DFT calculations were reported for calix[4]arene derivatives [i.e., formylaminocalix[4]arene (1) and formylaminocalix[4]bis-crown-3 (2)] binding cations M+ (Li+, Na+, and K+) and anions X- (F-, Cl-, and Br-) simultaneously. The B3LYP function together with the LANL2DZp basis set was used in order to obtain insights into the factors determining the nature of the interactions of these compounds with X- and M+. Based on the molecular electrostatic potential (MEP) analysis, the result complexes M+X-/H (H = 1, 2) were investigated. For all the complex structures, the most pronounced changes in geometric parameters upon interaction were observed in the host segment compared with the free receptors. Two main types of driving force, N-H∙∙∙X- hydrogen bonds and electrostatic interactions between M+ and oxygen atoms, were confirmed. The recognition trends for 1 and 2 toward M+X- followed the same order: M+F- > M+Cl- > M+Br- (M+ is same to each other) and Li+X- > Na+X- > K+X- (X- is same to each other). The binding energy, enthalpy change, Gibbs free energy change, and entropy change of complexation formation have been studied by the calculated thermodynamic data. In all cases, the inclusion energy changes with 2 were more negative than those with 1, correlating with the flexible space available by the two crown ether moieties in 2. The calculated results of the model system have been reported and should be useful to the experimental research in this field.

Mechanisms for ozone-initiated removal of biomass burning products from the atmosphere

Environmental context An important product of biomass burning is catechol: its presence in the atmosphere can have adverse effects on health, and can lead to the formation of secondary organic aerosols. We report a theoretical study on the mechanisms and kinetics of removal of catechol from the atmosphere by reaction with ozone. These data will provide insight into the ozonolysis of other lignin compounds produced by biomass burning. Abstract We examined the ozone-initiated oxidation of catechol, an intermediate of lignin pyrolysis in the atmosphere, by using the theoretical computational method at the M06-2X/aug-cc-pVDZ//M06-2X/6-31+G(d,p) level. Six ozone-addition channels of the initial reactions and the further reactions of the Criegee intermediates are proposed. The complete degradation processes of the Criegee intermediates in the presence of NO and H2O were elucidated. The predicted reaction products for the ozonolysis of catechol, such as malealdehyde (P10), oxalic acid (P11) and CO2, were detected experimentally in the gas-phase. Moreover, the microcanonical rate constants of the crucial elementary reactions were determined by the Rice–Ramsperger–Kassel–Marcus theory. The total rate constant for the ozonolysis of catechol under atmospheric conditions is 1.37 × 10−18 cm3 molecule−1 s−1, which compares favourably to the experimentally determined values. The bimolecular rate constants showed positive dependence on temperature and negative dependence on pressure. The atmospheric lifetime of catechol with respect to ozone was estimated to be 12.07 days. We also found that the ozonolysis of catechol is more likely to occur in aqueous solution. The present work has provided a comprehensive investigation of the ozonolysis of catechol. The methods we used can serve as a model for analysing the ozonolysis of other lignin compounds.

Theoretical investigation of pillar[4]quinone as a cathode active material for lithium-ion batteries

AbstractThe applicability of a novel macrocyclic multi-carbonyl compound, pillar[4]quinone (P4Q), as the cathode active material for lithium-ion batteries (LIBs) was assessed theoretically. The molecular geometry, electronic structure, Li-binding thermodynamic properties, and the redox potential of P4Q were obtained using density functional theory (DFT) at the M06-2X/6-31G(d,p) level of theory. The results of the calculations indicated that P4Q interacts with Li atoms via three binding modes: Li–O ionic bonding, O–Li···O bridge bonding, and Li···phenyl noncovalent interactions. Calculations also indicated that, during the LIB discharging process, P4Q could yield a specific capacity of 446 mAh g−1 through the utilization of its many carbonyl groups. Compared with pillar[5]quinone and pillar[6]quinone, the redox potential of P4Q is enhanced by its high structural stability as well as the effect of the solvent. These results should provide the theoretical foundations for the design, synthesis, and application of novel macrocyclic carbonyl compounds as electrode materials in LIBs in the future. Graphical AbstractSchematic representation of the proposed charge-discharge mechanism of Pillar[4]quinone as cathode for lithium-ion batteries