Surface stress generation during formation of alkanethiol self-assembled monolayer (SAM)

A high resolution curvature interferometer [Wang, J., Shrotriya, P., Kim, K.S., 2006. Surface residual stress measurement using curvature interferometry. Experimental Mechanics 46 (1), 39–46] is utilized to measure surface stress development associated with formation of self-assembled monolayers (SAM) of octadecanethiols on macroscale domains (25 mm × 25 mm). Atomistic simulations are performed to investigate surface stress generation associated with SAM formation. The results of the molecular simulations are incorporated into the multiscale framework to understand the surface stress generation and curvature change observed during experiments at continuum scale.     

Formation of Peracetic Acid upon Aging of Perborate in Acetic Acid. Kinetics of the Oxidation of S-Phenylmercaptoacetic Acids

 Upon aging, perborate in glacial acetic acid generates peracetic acid and thus oxidizes S-phenylmercaptoacetic acid rapidly. Perborate dissolved in ethylene glycol, however, does not show the aging effect, and the corresponding oxidation proceeds smoothly. The oxidation is of second order and not acid catalyzed. Boric acid and borate do not influence the oxidation. In the smooth oxidation, is the reactive species. The oxidation of some para-substituted S-phenylmercaptoacetic acids conforms to the Exner relationship, indicating operation of a common mechanism. Also, the oxidation obeys the Hammett equation with a negative reaction constant. However, the oxidation of p-nitro-S-phenylmercaptoacetic acid follows a different kinetic pathway.     

Molybdenum(VI) catalysis of perborate or hydrogen peroxide oxidation of iodide ion

Summary Perborate in aqueous solution generates H₂O₂; in its presence the molybdenum(VI) catalysed oxidation of iodide ion is first order with respect to the oxidant and catalyst, and is independent of [I^–] and [H⁺]. Kinetic studies point to peroxymolybdenum(VI) species as the oxidizing species.     

A Clean Clay Catalysed Synthesis of á,N-Diarylnitrones

Abstract: The first clean and the facile clay catalysed synthesis of á,N-diarylnitrones in good yield is reported.     

Chitosan-based tyrosinase optical phenol biosensor employing hybrid nafion/sol-gel silicate for MBTH immobilization

The development of an optical biosensor based on immobilization of 3-methyl-2-benzothiazolinone hydrazone (MBTH) in hybrid nafion/sol-gel silicate film and tyrosinase in chitosan film for the detection of phenolic compounds has been described. Tyrosinase was immobilized in chitosan film deposited on the hybrid nafion/sol-gel silicate film containing MBTH. The enzymatic oxidation product of phenolic compounds were stabilized through formation of adduct with MBTH to produce a maroon color adduct. The color intensity of adduct was found to increase proportionally with the increase of the substrate concentrations after 5 min exposure. The linearity of the biosensor towards phenol, catechol and m-cresol were in the respective concentration range of 0.5-7.0, 0.5-10.0 and 1.0-13.0 mg/L with detection limit of 0.18, 0.23 and 0.43 mg/L, respectively. The biosensor shows a good stability for at least 3 months.     

Vanadia-catalyzed solar photooxidation of aniline

Vanadia photocatalyzes the oxidation of aniline to azobenzene in ethanol. The reaction was studied using natural sunlight and UV irradiation (365 nm) as a function of [aniline], catalyst loading, airflow rate, solvent composition, etc. The photocatalyst exhibits sustainable catalytic activity. The product formation is greater with illumination at 254 nm than at 365 nm. Electron donors such as triphenylphosphine, diphenylamine, and hydroquinone enhance the photocatalysis. The singlet oxygen quencher azide ion fails to inhibit the catalysis. The photocatalysis takes place in both protic and aprotic solvents. The mechanism of photocatalysis is discussed and the product formation analyzed using a kinetic model.     

Molecular constants of XeO3F2

The force constants of XeO₃F₂ have been evaluated using the general valence force field. The mean square amplitudes of vibration, the generalised mean square amplitudes and shrinkage constants, Coriolis coupling coefficients and centrifugal distortion constants have also been calculated for the first time using the vibrational frequencies and the structural parameters. The thermodynamic properties have been computed for the ideal gaseous state at 1 atmospheric pressure for 11 temperatures from 100° to 1000°K using a rigid rotor harmonic oscillator approximation.     

Lack of Linear Free Energy Relationships in the p-Toluenesulfonic Acid Mediated Chromium(VI) Oxidation of Organic Sulfides

 The oxidation of methylphenyl sulfide by imidazolium dichromate in acetonitrile mediated by p-toluenesulfonic acid is first order in IDC and TsOH and zero order in MeSPh in the concentration range studied. The IDC oxidation of 14 para-, meta-, and ortho-substituted phenylmethylsulfides at 20–45°C conforms to the isokinetic relationship but not to any of the linear free energy relationships; the isokinetic temperature lies within the experimental temperature range.     

Kinetics of hydrogen sulfide decomposition in a DBD plasma reactor operated at high temperature

The present study investigates the kinetics of hydrogen sulfide（H₂S） decomposition into hydrogen and sulfur carried out in a nonthermal plasma dielectric barrier discharge（NTP-DBD） reactor operated at～430 K for in situ removal of sulfur condensed inside the reactor walls. The dissociation of H₂S was primarily initiated by the excitation of carrier gas（Ar） through electron collisions which appeared to be the rate determining step.The experiments were carried out with initial concentration of H₂S varied between 5 and 25 vol%at 150 mL/min（at standard temperature and pressure） flow rate in the input power range of 0.5 to 2 W.The reaction rate model based on continuous stirred tank reactor（CSTR） model failed to explain the global kinetics of H₂S decomposition,probably due to the multiple complex reactions involved in H₂S decomposition,whereas Michaelis-Menten model was satisfactory.Typical results indicated that the reaction order approached zero with increasing inlet concentration.