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Polymeric ionic liquid (such as poly[ViEtIm]Br)-modified reduced graphene oxide (rGO), rGO-poly[ViEtIm]Br, was nominated as an open carrier to construct a degradation platform. The large specific surface of rGO together with the anion-exchange property of poly[ViEtIm]Br terminals led to the wide growth of heteropolyanions (like [PW

In this article, we report a theoretical investigation on the role of several catalysts in the isomerisation mechanisms of HON(O)NNO2 to ON(OH)NNO2 by theoretical method of CBS-QB3. The isomerisati...

CBS-QB3 method has been employed to determine the geometries, the vibrational frequencies of the reactants, the products and the transition states involved in intramolecular hydrogen-transfer and decomposition reactions of the free gas-phase H3N···HN(NO2)2 (ADN*). The results show that the intramolecular hydrogen-transfer reaction of ADN* is more feasible than that of HDN. ADN* and its hydrogen-transfer isomers ADN*-IIa,b,c decompose along four channels to form NH3 + HONO + 2NO (PI), ȮH + ṄO3 + N2 + NH3 (PII), ȮH + ṄO2 + N2O + NH3 (PIII), and HNO3 + N2O + NH3 (PIV), respectively. It has been found that the dominant decomposition channels are PI and PIII. The hydrogen-transfer reaction can reduce the barrier of elimination of NO2 and forming N2O reactions in ADN* and HDN. The decomposition of ADN*-IIc to form NO2 and N2O is more feasible than that of the gas-phase HDN. The rate constants (k) of rate-determining step of ADN* show that kPI and kPIII are higher than kPIV and kPII. Compared with HDN-II...

The effects of (H2O)n (n = 1–2) on hydrogen abstraction reaction (H2O2 + HS → H2S + HO2) have been investigated at the level of theories of B3LYP and CCSD(T). The aug-cc-pVTZ basis set has been used in the present treatment. The catalytic effect has been found to be small for water dimer and is significant for water, because the effective rate constant for the water-catalyzed reaction being 3–4 orders of magnitude larger than the corresponding water-dimer assisted reaction. Compared to the un-catalyzed reaction, the rate enhancement due to water catalysis at lower temperature (e.g., 240 K) was only 0.17%, which was increased to 72.7% at higher temperature (e.g., 325 K).

In the current work, time-dependent density functional theory calculations coupled with a set of multidimensional visualization techniques have been used to investigate the photovoltaic properties (the band gap, optical absorption, reorganization energy, charge transfer integrals, and rates of exciton dissociation and charge recombination.) of PC 61 BM-PTDPPTFT4 system with a simplified molecular model. Calculations reveal that TDPPTFT4 oligomers possess the narrow electronic band gap (1.792–1.903 eV), strong and wide optical absorption ( λ max = 792 nm, f max = 4.962 for TDPPTFT4 trimer) in UV–Vis region, and small internal reorganization energy (0.118 eV) in charge transfer process. In addition, the calculation also shows that the exciton-dissociation rate is very fast (10 10 –10 13 s −1 ) in the interface of PC 61 BM-TDPPTFT4 n=1,2,3 complexes, while the charge-recombination one is relatively slow (10 6 –10 8 s −1 ) under the same condition, which denotes that the exciton dissociation efficiency in the studied donor–acceptor interface is very high. Combining the large mobility (0.47–2.10 cm 2 V −1 s −1 ), we consider that PTDPPTFT4 is a very promising electron donor material of polymer-based solar cells, and worthy of being investigated further in experiments. Our theoretical investigation can promote deeper understanding of the connection between the chemical structure and the optical and electronic properties of the donor–acceptor, and provide some valuable references to the rational design of novel donor–acceptor systems.

The oxidation of CO over Au3− cluster was investigated using the DFT by selecting peroxo-like adsorbate intermediate, Au3CO(O2)−, of CO and O2 over the Au3− cluster, as the reactant model. Based on the transition state investigation at UB3LYP/LANL2DZ, the energies at the UB3LYP/aug-cc-pVTZ-PP//LANL2DZ level theory and corresponding relativistic effective core potential (RECP) for Au, 6-311 + G∗ for carbon and oxygen atoms, the reaction potential energy diagrams and pathways were analyzed. For the selecting Au3CO(O2)− as the initial intermediated proceeded through a typical LH mechanism and forming a complex of CO2 and Au3O−, and the subsequent intermediate, Au3OCO−, formed by the reaction of CO with Au3O− were also analyzed. The results indicated that the CO oxidation followed the LH or ER mechanism, and their rate constants increased with increasing temperature. For the main reason of CO oxidation over Au3− cluster with no perceptible catalytic activity, it should be the no sufficient peroxo-like complex (Au3COO2−, 1A) formation due to the very low content of low-spin O2 under normal conditions, and that the peroxo-like compound also showed a low oxidation rate at low temperature.

Two type routes of HCl···H2SO4-(trans, cis and cage) + HO and HO···H2SO4-(trans, cis and cage) + HCl in H2SO4-catalyzed HCl + HO reaction have been investigated by using CCSD(T)-F12a/cc-pVDZ-F12 //M06-2X/6–311++G(2d,2p) methods, and canonical variational transition state theory with small curvature tunneling. It is shown that the process of HCl···H2SO4-trans + HO is the most favorable in all H2SO4-assisted routes. Within the temperature range of 280–320 K, H2SO4 not only is more effective than HCOOH (0.01 ppbv) and NH3 (0.1 ppbv), but also are competitive with NH3 (10 ppbv) and HCOOH (2 ppbv). However, H2SO4 would not be able to compete with H2O (20–100% RH), NH3 (2900 ppbv), HCOOH (10 ppbv) and the naked reaction of HCl + HO due to its relatively lower concentration.

A comprehensive investigation of the roles of H2O and NH3 on the HO + NH3 → NH2 + H2O reaction in the troposphere has been carried out by CCSD(T)-F12a/cc-pVDZ-F12//M06-2X/6–311+G(2d,2p) method, and the canonical variational transition state theory with small curvature tunneling correction. The results show that both H2O and NH3 catalyzed reactions prefer the single hydrogen atom transfers (HAT) pathways than the double HAT routes. Meanwhile, the catalytic effect of H2O is more obvious as compared with NH3 with its effective rate constant (k'(WM)) larger by 2–5 orders of magnitude. However, within the temperature range of 213–320 K, the calculated value of k'(WM) is smaller by 5–9 orders of magnitude than the corresponding rate constant of the naked reaction. This result is in agreement with H2O catalyzed OH + CH2CH2, OH + CH2O and OH + CH2NH reactions, where water-assisted reaction cannot accelerate the reaction.

Effects of (H2O)n (n = 1–3) on the H2O2 + HO → HO2 + H2O reaction have been investigated by the reactions of H2O2L(H2O)n (n = 1–3) + HO and H2O2 + HOL(H2O)n (n = 1–3) at the CCSD(T)/CBS//M06-2X/aug-cc-pVTZ level of theory, coupled with rate constant calculations by using canonical variational transition state theory. Interestingly, for the former reactions, one-step process and stepwise mechanism are involved, where one-step processes occurring though cage-like hydrogen bonding network complexes and the transition states are favourable. Due to larger effective rate constants, these favourable processes are also favourable than the corresponding latter reactions. Meanwhile, the catalytic effect of (H2O)n (n = 1–3) is mainly taken from water monomer, because the effective rate constant (k'(R_WM2)) of H2O2···H2O + HO reaction is, respectively, larger by 3, 6–10 orders of magnitude than that of H2O2···(H2O)2 + HO (k'(R_WD1)) and H2O2···(H2O)3 + HO (k'(R_WT1)) reactions. Furthermore, the enhancement factor of water molecular (k'(R_WM2)/ktot) is only 0.28% at 240 K, while at high temperature (such as at 425 K), the positive water vapour effect enhances up to 27.13%. This shows that at high temperatures the positive water effect is obvious under atmospheric conditions.

The addition reaction of CH2OO + H2O → CH2(OH)OOH without and with X (X = H2CO3, CH3COOH and HCOOH) and H2O was studied at CCSD(T)/6-311+ G(3df,2dp)//B3LYP/6-311+G(2d,2p) level of theory. Our results show that X can catalyse CH2OO + H2O → CH2(OH)OOH reaction both by increasing the number of rings, and by adding the size of the ring in which ring enlargement by COOH moiety of X inserting into CH2OO···H2O is favourable one. Water-assisted CH2OO + H2O → CH2(OH)OOH can occur by H2O moiety of (H2O)2 or the whole (H2O)2 forming cyclic structure with CH2OO, where the latter form is more favourable. Because the concentration of H2CO3 is unknown, the influence of CH3COOH, HCOOH and H2O were calculated within 0–30 km altitude of the Earth's atmosphere. The results calculated within 0–5 km altitude show that H2O and HCOOH have obvious effect on enhancing the rate with the enhancement factors are, respectively, 62.47%–77.26% and 0.04%–1.76%. Within 5–30 km altitude, HCOOH has obvious effect on enhancing the title rate with the enhancement factor of 2.69%–98.28%. However, compared with the reaction of CH2OO + HCOOH, the rate of CH2OO···H2O + HCOOH is much slower.

In this article, the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH without and with catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2) have been investigated theoretically at the CBS-QB3 level of theory. Our results show that the catalyst X (X = H2O, (H2O)2, (H2O)3, HCOOH, H2SO4 and CH3CH2COOH) shows different positive catalytic effects on reducing the apparent activation energy of the isomerisation reaction processes. Such different catalytic effects are mainly related to the number of hydrogen bonds and the size of the ring structure in X (X = H2O, (H2O)2 and (H2O)3)-assisted transition states, as well as different values of pKa for H2SO4, HCOOH and CH3CH2COOH. Very interesting is also the fact that H2SO4-assisted reaction is the most favourable for the hydrogen transfer from HN(NO2)2 to O2NNN(O)OH, due to the smallest pKa (−3.0) value of H2SO4 than H2O, HCOOH, H2SO4 and CH3CH2COOH, and also because of the largest ∠X•••H•••Y (the angle between the hydrogen bond donor and acceptor) involved in H2SO4-assisted transition state. Compared to the self-catalysis of the isomerisation mechanisms of HN(NO2)2 to O2NNN(O)OH, the apparent activation energy of H2SO4-assisted channel also reduces by 9.6 kcal⋅mol−1, indicating that H2SO4 can affect the isomerisation of HN(NO2)2 to O2NNN(O)OH, most obvious among all the catalysts H2O, (H2O)2, (H2O)3, HCOOH, H2SO4, CH3CH2COOH and HN(NO2)2.

The reaction mechanism of HCHO with HO2 radical has been studied at CBS-QB3 level of theory. Three direct hydrogen abstraction processes, one double hydrogen transfer mechanism, three cooperative hydrogen abstraction processes, and one additional channel have been identified for HCHO + HO2 reaction. The calculated results indicate that the additional mechanism of HOCH2OO formation as well as the direct hydrogen abstraction process of HOC + H2O2 formations is dominant. Other channels may be negligible due to the high barrier heights. Rate constants and branching ratios have been estimated by means of the conventional transition state theory with zero-curvature tunnelling over the temperature range of 275–1800 K. The calculation shows that the overall rate constant in the temperature of 275–1800 K is mainly dependent on the channel of HOCH2OO formation. The three-parameter expression for the total rate constant is fitted to be cm3 molecule−1 s−1 between 275 and 1800 K.

Second-order perturbation theory and transition state theory rate constant calculations have been performed to gain insight into the effect of one and two water molecules on the process of 3O2 formation from the HO2 + HO2 reaction that is proposed to be important in atmospheric chemistry. Based on the reaction of H2O⋯HO2 + HO2 investigated by Zhu and Lin (2002), a comprehensive mechanism for a single water-catalyzed the title reaction was suggested in which the additional reactions of HO2⋯H2O + HO2 were also not neglected, with barrier heights between 1.10 and 1.79 kcal mol−1, and the estimated reaction rate constants 1–2 orders-of-magnitude larger than the naked reaction estimates. At 298 K the total enhancement factor of the reactions of H2O⋯HO2 + HO2 and HO2⋯H2O + HO2 is up to ∼5.70%. The question whether two water molecules will affect 3O2 formation in the HO2 + HO2 reaction was investigated by studying the reactions of H2O⋯HO2 + H2O⋯HO2, H2O⋯HO2 + HO2⋯H2O and HO2⋯(H2O)2 + HO2. The results show that the reaction occurring through the H2O⋯HO2 + HO2⋯H2O reactants is dominant. However, its effective rate constant within the temperature range of 216.7–298.2 K is much smaller than that with a water molecule, showing that the positive water effect for the title reaction mainly comes from one water molecule.

In this paper, a time-domain amplitude decaying (TDAD) method measuring the quality factor ( $$Q$$ Q ) of micro-electro-mechanical system (MEMS) resonators is presented. The decaying amplitudes of the resonators are measured using a lock-in amplifier (LIA) and fitted exponentially to extract the $$Q$$ Q . To suppress the capacitive feedthrough signal, the internal reference of the LIA is used to excite the resonators and the decaying amplitudes are detected with the first harmonic mode (2 $$f$$ f ). $$Q$$ Q s of wafer level packaged MEMS resonators are measured using both the proposed TDAD method and the commonly used sweeping method. The relative error of the measured $$Q$$ Q s using the two methods is $$

A detailed effects of catalyst X (X = H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4) on the HO4H → O3 + H2O reaction have been investigated by using quantum chemical calculations and canonical vibrational transition state theory with small curvature tunnelling. The calculated results show that (H2O)2-catalysed reactions much faster than H2O-catalysed one because of the former bimolecular rate constant larger by 2.6–25.9 times than that of the latter one. In addition, the basic H2O···NH3 catalyst was found to be a better than the neutral catalyst of (H2O)2. However it is marginally less efficient than the acidic catalysts of HCOOH, and H2SO4. The effective rate constant (k't) in the presence of catalyst X have been assessed. It was found from k't that H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K at 0 km altitude. However, compared with the rate constant of HO4H → H2O + O3 reaction, the k eff values for H2O catalysed reaction are smaller by 1–2 orders of magnitude, indicating that the catalytic effect of H2O makes a negligible contribution to the gas phase reaction of HO4H → O3 + H2O. Highlights A detailed effects of catalyst of H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4 on the HO4H → O3 + H2O reaction has been performed.From energetic viewpoint, H2SO4 exerts the strongest catalytic role in HO4H → O3 + H2O reaction as compared with the other catalysts.At 0 km altitude H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K.HO4H → H2O + O3 reaction with H2O cannot be compete with the reaction without catalyst, due to the fact that the effective rate constants in the presence of H2O are smaller. A detailed effects of catalyst of H2O, (H2O)2, NH3, NH3···H2O, H2O···NH3, HCOOH and H2SO4 on the HO4H → O3 + H2O reaction has been performed. From energetic viewpoint, H2SO4 exerts the strongest catalytic role in HO4H → O3 + H2O reaction as compared with the other catalysts. At 0 km altitude H2O (at 100% RH) completely dominates over all other catalysts within the temperature range of 280–320 K. HO4H → H2O + O3 reaction with H2O cannot be compete with the reaction without catalyst, due to the fact that the effective rate constants in the presence of H2O are smaller.

The thermal decomposition of methylcyclohexane (MCH) has been investigated at the CBS-QB3 and CCSD level of theory. The pyrolysis of MCH follows a radical chain mechanism, which mainly includes the C–C bond scission, H-atom abstraction, secondary and biradical reactions. Thermodynamic data for selected species involved in this study are computed at the CBS-QB3 level. The rate constants for all elementary reactions are also evaluated with conventional transition state theory (TST) in the temperature range of 298–2000 K, where Eckart method is adopted to correct the quantum mechanical tunneling effect. The rate constants are reasonable agreement with experimental measurements and previous theoretical reports. Furthermore, the final products of MCH thermal decomposition are methane (CH 4 ), ethylene (C 2 H 4 ), propylene (C 3 H 6 ), 1,3-butadiene (1,3-C 4 H 6 ), isoprene (C 5 H 8 ) and 1,3-pentadiene (1,3-C 5 H 8 ). The main goal of this work is to give an exhaustive description of the MCH thermal decomposition by means of high level quantum chemical methods and provide a reliable reference for thermodynamic and kinetic information.

In this work, four different channels, represented by H2O•••HO2 + HOCl, HO2•••H2O + HOCl, H2O•••HOCl + HO2 and HOCl•••H2O + HO2 have been analysed for water-catalysed formations of H2O2 + ClO to gain insight into the potential impact of the reaction in the atmosphere. The results at the CCSD(T)/aug-cc-pVTZ//MP2/6-311+G(2df,2p) level show that the H2O•••HO2 + HOCl reaction is kinetically the most favourable channel among the four channels. Compared to the channel of H2O2 + ClO formations without water vapour, the effective rate constant of H2O•••HO2 + HOCl reaction is estimated to be faster than the naked reaction by 2–3 orders of magnitude, indicating that the single water molecule in the H2O•••HO2 + HOCl channel exhibits a positive catalytic effect on enhancing the rate of H2O2 + ClO formations. Meanwhile, it is interesting that the transfer process between H2O•••HOCl + HO2 and H2O•••HO2 + HOCl has an activation energy of 0.6 kcal⋅mol−1 and can occur easily under tropospheric conditions.

The mechanism of the reaction of the radical C 2 H 5 S with the radical HO 2 has been investigated theoretically by means of the density functional theory (DFT) and coupled cluster theory (CC). The geometries of all the stationary points and the selected points along the potential energy surfaces for the reaction of C 2 H 5 S with HO 2 were optimized at the B3LYP/6-311G(2d,p) level of theory. The harmonic vibrational frequencies of all the stationary points were calculated at the above same level of theory. The single point energies were further refined at the CCSD(T)/aug-cc-pVDZ level of theory based on the B3LYP/6-311G(2d,p) optimized geometries. Eight possible reaction pathways including eleven reaction channels on both the singlet and triplet potential energy profiles for the title reaction were explored. The calculated results indicated that Path R4, the formation of the products C 2 H 5 SO + OH on the singlet potential energy profile, is likely to be the most favorable channel among Path R1∼4, and Path R5, hydrogen abstraction of HO 2 by the S atom of CH 3 CH 2 S, is the most favorable among Path R5∼8 on the triplet potential energy profile. The major products of the reaction may be C 2 H 5 SH, 3 O 2 , C 2 H 5 SO and OH.

The formations of CHFO, 1 O 2 , O 3 and 3 O 2 in CH 2 FO 2 + HO 2 and CH 2 FO 2 + HO 2 ⋅H 2 O reaction are studied by employing the quantum chemical calculations with B3LYP and CCSD(T) theoretical methods, canonical variational transition (CVT) state theory with small curvature tunneling (SCT) correction. The calculated results show that the formations of CHFO and 3 O 2 are main products in the naked reaction of CH 2 FO 2 + HO 2 . When water is added, the formations of CHFO and O 3 are main products in CH 2 FO 2 + HO 2 ⋅H 2 O reaction. Moreover, the calculated rate constants for the title reaction without and with a water molecule show that, although the single water molecule plays a positive catalytic effect on enhancing the rate for CHFO and O 3 formation, in humid conditions the effective rate of CH 2 FO 2 + HO 2 reaction will changes little with respect to dry conditions.

The hydrogen and oxygen abstraction mechanism for the radical–radical reaction of CH3S with HOO has been investigated at the CCSD(T)/aug-cc-pVDZ//B3LYP/6-311+G(d,p) level of theory on both the singlet and triplet potential energy profiles. Four hydrogen abstraction channels and one oxygen abstraction process are found for the title reaction. The calculations indicate that the triplet potential energy profile is much lower than the singlet energetically. Two hydrogen abstraction channels Rc, Rd and one oxygen abstraction process Re are identified on the triplet potential energy profile. Channel Rc, formation of CH3SH + 3O2, is the most favorable. Furthermore, the rate constants of channel Rc in a temperature range 200–800 K are calculated by means of the canonical variational transition state theory with small-curvature tunneling correction. The fitted three-parameter expression for kCVT/SCT of the major pathway is kCVT/SCT = 2.80 × 10−39T7.49exp(6071/T) cm3 molecule−1 s−1 and it shows a negative dependence in the calculated temperature range.

A theoretical study of the mechanism and the kinetics for the hydrogen abstraction reaction of the biradical hydroperoxy radical has been presented at the CCSD(T)/6-311++G(3d,2p)//CCSD/6-31+G(d,p) level of theory. Our theoretical calculations suppose a stepwise mechanism involving the formation of a postreactant complex in the triplet and singlet entrance channels. Four transition states of the six-membered chain complexes (3TS1 and 1TS1) and six-membered ring complexes (3TS2 and 1TS2) are located at the high dual level CCSD(T)/6-311++G(3d,2p)//CCSD/6-31+G(d,p) method. The rate constants of Path 1 ∼ Path 4 at the CCSD(T)/6-311++G(3d,2p)//CCSD/6-31+G (d,p) level are calculated by means of the conventional transition state theory (TST) and canonical variational TST without and with small-curvature tunneling (SCT) correction within the temperature range of 200–2,500 K. The calculated results show that the triplet channel is the dominating reaction channel and Path 2 is found to be the most favorable pathway. The rate constants of Path 2 are in good agreement with the experimental values at the experimentally measured temperatures. Moreover, the variational effect is not obvious in the low temperature range but is not neglectable in the high temperature range. The SCT plays an important role particularly in the low temperature range. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011