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Rare base-pairs consists of guanine (G) paired with rare bases, such as 5-methylcytosine (5-meCyt), 5-hydroxymethylcytosine (5-hmCyt), 5-carboxylcytosine (5-caCyt), and 5-formylcytosine (5-fCyt), have become the focus of epigenetic research because they can be used as markers to detect some chronic diseases and cancers. However, the correlation detection of these rare base-pairs is limited, which in turn limits the development of diagnostic tests and devices. Herein, the interaction of rare base-pairs adsorbed on pure and B/N-doped γ-graphyne (γ-GY) nanosheets was explored using the density functional theory. The calculated adsorption energy showed that the system of rare base-pairs on B-doped γ-GY is more stable than that on pure γ-GY or N-doped γ-GY. Translocation time values indicate that rare base-pairs can be successfully distinguished as the difference in their translocation times is very large for pure and B/N-doped γ-GY nanosheets. Meanwhile, sensing response values illustrated that pure and B-doped γ-GY are the best for G-5-hmCyt adsorption, while the N-doped γ-GY is the best for G-Cyt adsorption. The findings indicate that translocation times and sensing response can be used as detection indexes for pure and B/N doped γ-GY, which will provide a new way for experimental scientists to develop the biosensor components. [ABSTRACT FROM AUTHOR]

The products resulting from the reactions between atmospheric acids and SO3 have a catalytic effect on the formation of new particles in aerosols. However, the SO3 + HCl reaction in the gas-phase and at the air–water interface has not been considered. Herein, this reaction was explored exhaustively by using high-level quantum chemical calculations and Born Oppenheimer molecular dynamics (BOMD) simulations. The quantum calculations show that the gas-phase reaction of SO3 + HCl is highly unlikely to occur under atmospheric conditions with a high energy barrier of 22.6 kcal mol−1. H2O and (H2O)2 play obvious catalytic roles in reducing the energy barrier of the SO3 + HCl reaction by over 18.2 kcal mol−1. The atmospheric lifetimes of SO3 show that the (H2O)2-assisted reaction dominates over the H2O-assisted reaction within the altitude range of 0–5 km, whereas the H2O-assisted reaction is more favorable within an altitude range of 10–50 km. BOMD simulations show that H2O-induced formation of the ClSO3−⋯H3O+ ion pair and HCl-assisted formation of the HSO4−⋯H3O+ ion pair were identified at the air–water interface. These routes followed a stepwise reaction mechanism and proceeded at a picosecond time scale. Interestingly, the formed ClSO3H in the gas phase has a tendency to aggregate with sulfuric acids, ammonias, and water molecules to form stable clusters within 40 ns simulation time, while the interfacial ClSO3− and H3O+ can attract H2SO4, NH3, and HNO3 for particle formation from the gas phase to the water surface. Thus, this work will not only help in understanding the SO3 + HCl reaction driven by water molecules in the gas-phase and at the air–water interface, but it will also provide some potential routes of aerosol formation from the reaction between SO3 and inorganic acids. [ABSTRACT FROM AUTHOR]

The reactions between SO3 and atmospheric acids are indispensable in improving the formation of aerosol particle. However, relative to those of SO3 with organic acids, the reaction of SO3 with inorganic acids has not received much attention. Here, we explore the atmospheric reaction between SO3 and H2SO4, a typical inorganic acid, in the gas phase and at the air-water interface by using quantum chemical (QC) calculations and Born-Oppenheimer molecular dynamics simulations. We also report the effect of H2S2O7, the product of the reaction between SO3 and H2SO4, on new particle formation (NPF) in various environments by using the Atmospheric Cluster Dynamics Code kinetic model and the QC calculation. The present findings show that the gas phase reactions of SO3 + H2SO4 without and with water molecule are both low energy barrier processes. With the involvement of interfacial water molecules, H2O-induced the formation of S2O72-⋅⋅⋅H3O+ ion pair, HSO4- mediated the formation of HSO4-⋅⋅⋅H3O+ ion pair and the deprotonation of H2S2O7 were observed and proceeded on the picosecond time-scale. The present findings suggest the potential contribution of SO3-H2SO4 reaction to NPF and aerosol particle growth as the facts that i) H2S2O7 can directly participate in H2SO4-NH3-based cluster formation and can facilitate the fastest possible rate of NPF from H2SO4-NH3-based clusters by about a factor of 6.92 orders of magnitude at 278.15 K; and ii) the formed interfacial S2O72- can attract candidate species from the gas phase to the water surface, and thus, accelerate particle growth. [ABSTRACT FROM AUTHOR]

Liu et al. (Proc. Natl. Acad. Sci. U. S. A, 2019, 116, 24966–24971) showed that at an altitude of 0 km, the reaction of SO3 with CH3OH to form CH3OSO3H reduces the amount of H2SO4 produced by the hydrolysis of SO3 in regions polluted with CH3OH. However, the influence of the water molecule has not been fully considered yet, which will limit the accuracy of calculating the loss of SO3 in regions polluted with CH3OH. Here, the influence of water molecules on the SO3 + CH3OH reaction in the gas phase and at the air–water interface was comprehensively explored by using high-level quantum chemical calculations and Born–Oppenheimer molecular dynamics (BOMD) simulations. Quantum chemical calculations show that both pathways for the formation of CH3OSO3H and H2SO4 with water molecules have greatly lowered energy barriers compared to the naked SO3 + CH3OH reaction. The effective rate coefficients reveal that H2O-catalyzed CH3OSO3H formation (a favorable route for CH3OSO3H formation) can be competitive with H2O-assisted H2SO4 formation (a favorable process for H2SO4 formation) at high altitudes up to 15 km. BOMD simulations found that H2O-induced formation of the CH3OSO3−⋯H3O+ ion pair and CH3OH-assisted formation of HSO4− and H3O+ ions were observed at the droplet surface. These interfacial routes followed a loop-structure or chain reaction mechanism and proceeded on a picosecond time scale. These results will contribute to better understanding of SO3 losses in the polluted areas of CH3OH. [ABSTRACT FROM AUTHOR]

Methyl hydrogen sulfate (MHS) as a common nucleation precursor that has important effect on new particle formation (NPF). Liu et al. showed that MHS and sulfuric acid (SA) generation are competitive due to consumption of the common precursor SO3, and the nucleation ability of SA is better than MHS. Thus, MHS inhibits the SA‐DMA‐based clusters formation particularly in regions with high [MO] (methanol) (Liu et al., Proc. Natl. Acad. Sci. U.S.A. 2019, 116, 24,966). However, in regions where [H2O] is much higher than [MO] ([SA] > > [MHS]), the SO3 consumed by the generation of less MHS will not significantly reduce the [SA], whether MHS still inhibits SA‐A‐based clusters formation and how MHS affects the growth pathways of MHS‐SA‐A‐based clusters remains unclear. Hence, quantum chemistry calculations combining Atmospheric Cluster Dynamics Code (ACDC) are used to investigate the role of MHS in the SA‐A‐based system. Our conclusions show two different effects of MHS in NPF process: "inhibiting" in regions with high [MO] and "weakly facilitating" in regions with high [H2O] and low [MO]. The growth pathways show that with the increasing [MHS], the role of MHS in NPF gradually changes from "transporter" to "participator", and the contribution to the pathways increases from 7 to 85%. Our results contribute to understanding the NPF in low‐temperature regions with different concentrations of MO and H2O. [ABSTRACT FROM AUTHOR]

Catalytic oxidation of toluene was implemented over SmMnO3, Sm0.8A0.2MnO3 (ABO3, A=Ce, Sr, Ca) and Sm1-xCaxMnO3 (x=0.0, 0.1, 0.2, 0.3) perovskite oxides synthesized via sol-gel method. The effects of A-site substitution of SmMnO3 and the amount of calcium substitution of SmMnO3 perovskite-type catalyst on the catalytic activity of toluene were investigated in a fixed bed reactor. The structure and chemical properties of the perovskites were studied by XRD, SEM, XPS, and H2-TPR. The results showed that the substitution of Ce and Ca had a positive impact about the catalytic properties of toluene oxidation, while a negative impact was caused by the substitution of Sr. The catalytic activity of toluene oxidation followed the order of Sm0.8Ca0.2MnO3>Sm0.8Ce0.2MnO3>SmMnO3>Sm0.8Sr0.2MnO3 in terms of the temperature of T90%, at toluene concentration=1,000 ppm and weight hourly space velocity (WHSV)=3,000 mL/ g·h. Sm0.8Ca0.2MnO3 had the highest catalytic capacity (T90%=238 °C), which could be attributed to its high adsorbed oxygen concentration, Mn4+/Mn3+, and the best low-temperature reducibility (H2 consumption=0.36). Meanwhile, the Sm0.8Ca0.2MnO3 catalysts showed great long-term stability after 30 h of the reaction, and the toluene degradation rate remained over 95% at 350 °C. [ABSTRACT FROM AUTHOR]