Nitrogen-doped C60 as a robust catalyst for CO oxidation.

The O2 activation and CO oxidation on nitrogen-doped C59 N fullerene are investigated using first-principles calculations. The calculations indicate that the C59 N fullerene is able to activate O2 molecules resulting in the formation of superoxide species ( O2-) both kinetically and thermodynamically. The active superoxide can further react with CO to form CO2 via the Eley-Rideal mechanism by passing a stepwise reaction barrier of only 0.20 eV. Ab initio molecular dynamics (AIMD) simulation is carried out to evidence the feasibility of the Eley-Rideal mechanism. In addition, the second CO oxidation takes place with the remaining atomic O without any activation energy barrier. The full catalytic reaction cycles can occur energetically favorable and suggest a two-step Eley-Rideal mechanism for CO oxidation with O2 catalyzed by the C59 N fullerene. The catalytic properties of high percentage nitrogen-doped fullerene (C48 N12 ) is also examined. This work contributes to designing higher effective carbon-based materials catalysts by a dependable theoretical insight into the catalytic properties of the nitrogen-doped fullerene. © 2017 Wiley Periodicals, Inc.

Nitrogen-doped carbon nanotube as a potential metal-free catalyst for CO oxidation.

We elucidate the possibility of nitrogen-doped carbon nanotube as a robust catalyst for CO oxidation. We have performed first-principles calculations considering the spin-polarization effect to demonstrate the reaction of CO oxidation catalyzed by the nitrogen-doped carbon nanotube. The calculations show that O2 species can be partially reduced with charge transfer from the nitrogen-doped carbon nanotube and directly chemisorbed on the C-N sites of the nitrogen-doped carbon nanotube. The partially reduced O2 species at the C-N sites can further directly react with a CO molecule via the Eley-Rideal mechanism with the barriers of 0.45-0.58 eV for the different diameter of nanotube. Ab initio molecular dynamics (AIMD) simulations were performed and showed that the oxidation of CO occurs by the Eley-Rideal mechanism. The relationship between the curvature and reactivity of the nitrogen doped carbon nanotube was also unraveled. It appears that the barrier height of the rate-limiting step depends on the curvature of the nitrogen-doped carbon nanotube in the trend of (3,3)-NCNT < (4,4)-NCNT < (5,5)-NCNT (decreases with increased curvature). Using this relationship, we can predict the barriers for other N-doped carbon nanotubes with different tube diameters. Our results reveal that the nitrogen doped carbon nanomaterials can be a good, low-cost, and metal-free catalyst for CO oxidation.

To Transfer or Not to Transfer? Development of a Dinitrosyl Iron Complex as a Nitroxyl Donor for the Nitroxylation of an Fe(III) -Porphyrin Center.

A positive myocardial inotropic effect achieved using HNO/NO(-) , compared with NO⋅, triggered attempts to explore novel nitroxyl donors for use in clinical applications in vascular and myocardial pharmacology. To develop M-NO complexes for nitroxyl chemistry and biology, modulation of direct nitroxyl-transfer reactivity of dinitrosyl iron complexes (DNICs) is investigated in this study using a Fe(III) -porphyrin complex and proteins as a specific probe. Stable dinuclear {Fe(NO)2 }(9) DNIC [Fe(µ-(Me) Pyr)(NO)2 ]2 was discovered as a potent nitroxyl donor for nitroxylation of Fe(III) -heme centers through an associative mechanism. Beyond the efficient nitroxyl transfer, transformation of DNICs into a chemical biology probe for nitroxyl and for pharmaceutical applications demands further efforts using in vitro/in vivo studies.

Hydrogen generation by the reaction of H2O with Al2O3-based materials: a computational analysis.

The mechanisms for H2O adsorption on γ-Al2O3(110) surface were investigated to illustrate the influence of oxide modifiers on the hydrogen generation reaction. Periodic density functional theory (DFT) calculations with the projected augmented wave (PAW) approach were carried out to study the adsorption of H2O, OH, O and H species, as well as the reaction mechanisms of H2O splitting and H2 generation. Their corresponding structures and adsorption energies are also reported. The calculation results show that H2O, OH, O and H are preferably bound at Al(I)-top, Al(III)-bridge, Al(I,II)-bridge and Al(III)-bridge sites with adsorption energies of -0.42, -5.01, -8.70 and -2.38 eV, respectively. The potential energy profiles for water splitting and hydrogen generation on the γ-Al2O3(110) surface are mapped out. We find that hydrogen generation on the surface occurs via two processes, namely, H2O dehydrogenation and direct H2 generation with an overall exothermicity of 2.24 eV. The nonexistence of intrinsic transition-state barriers and the high exothermicity for the reaction of H2O(g) + γ-Al2O3(110) → O(ads)/γ-Al2O3(110) + H2(g) result in rapid H2 generation. The stepwise H2 generation mechanism of adsorption on the γ-Al2O3(110) surface was also demonstrated using first-principles molecular dynamics simulations. In addition, the nature of the interaction between the adsorbate and the surface during the reaction was also analyzed by the local density of states and by Bader charge calculations.

Computational study of the kinetics and mechanisms for the HCO + O3 reaction.

The mechanisms of radical-molecule reactions between HCO (formyl radical) and O3 (ozone) have been investigated by using BH&HLYP and QCISD methods with the 6-311++G(3df,2p) basis set. The energetics have been refined with CCSD(T) and QCISD(T) theoretical approaches with the same basis set based on the geometries calculated at the QCISD method. The intermediates of hydrogen-bonded complexes and the critical transition states are also examined with the multireference methods. Two possible reaction pathways containing hydrogen-abstraction and association-elimination processes for the interaction of HCO with O3 are proposed. Both reaction mechanisms can occur via the prereactive hydrogen-bonded complex, O3-HCO, with 2.45 kcal/mol stability at the CCSD(T) approach with respect to the reactants; even so, the hydrogen-abstraction mechanism exhibits a lower energy barrier. The rate constants for both processes are also predicted. The total rate constant at 298 K is calculated to be in close agreement with the experimental value of 8.3 × 10(-13) cm(3) molecule(-1) s(-1).

Thiolated Mesoporous Silica Nanoparticles as an Immunoadjuvant to Enhance Efficacy of Intravesical Chemotherapy for Bladder Cancer.

The characteristics of global prevalence and high recurrence of bladder cancer has led numerous efforts to develop new treatments. The spontaneous voiding and degradation of the chemodrug hamper the efficacy and effectiveness of intravesical chemotherapy following tumor resection. Herein, the externally thiolated hollow mesoporous silica nanoparticles (MSN-SH(E)) is fabricated to serve as a platform for improved bladder intravesical therapy. Enhanced mucoadhesive effect of the thiolated nanovector is confirmed with porcine bladder. The permeation-enhancing effect is also verified, and a fragmented distribution pattern of a tight junction protein, claudin-4, indicates the opening of tight junction. Moreover, MSN-SH(E)-associated reprogramming of M2 macrophages to M1-like phenotype is observed in vitro. The antitumor activity of the mitomycin C (MMC)-loaded nanovector (MMC@MSN-SH(E)) is more effective than that of MMC alone in both in vitro and in vivo. In addition, IHC staining is used to analyze IFN-γ, TGF-ß1, and TNF-α. These observations substantiated the significance of MMC@MSN-SH(E) in promoting anticancer activity, holding the great potential for being used in intravesical therapy for non-muscle invasive bladder cancer (NMIBC) due to its mucoadhesivity, enhanced permeation, immunomodulation, and prolonged and very efficient drug exposure.

Computational study on reaction mechanisms and kinetics of RNCN (R = H, F, Cl, Br, CH3) radicals with NO.

We carried out a computational study of radical reactions of RNCN (R = H, F, Cl, Br, CH(3)) + NO to investigate how the substitution can influence their corresponding energy barriers and rate coefficients. The preferable reactive sites of RNCN radicals with various substituents are calculated by employing the Fukui functions and hard-and-soft acid-and-base theory, which were generally proved to be successful in the prediction and interpretation of regioselectivity in various types of electrophilic and nucleophilic reactions. Our calculated results clearly show that if the substituted RNCN radical has electron-donating substituent (for R = CH(3)), its corresponding barrier heights for transition states will be substantially decreased. The possible explanations of the observed increase and/or decrease in the energy barriers for the varied substituted RNCN radicals are also analyzed in this article.