Reaction Kinetics of CHOO and -CHCHOO Criegee Intermediates with Acetaldehyde.

Criegee intermediates exert a crucial influence on atmospheric chemistry, functioning as powerful oxidants that facilitate the degradation of pollutants, and understanding their reaction kinetics is essential for accurate atmospheric modeling. In this study, the kinetics of CHOO and -CHCHOO reactions with acetaldehyde (CHCHO) were investigated using a flash photolysis reaction tube coupled with the OH laser-induced fluorescence (LIF) method. The experimental results indicate that the reaction of -CHCHOO with CHCHO is independent of pressure in the range of 5-50 Torr when using Ar as the bath gas.

Water-participated mild oxidation of ethane to acetaldehyde.

The direct conversion of low alkane such as ethane into high-value-added chemicals has remained a great challenge since the development of natural gas utilization. Herein, we achieve an efficient one-step conversion of ethane to C oxygenates on a Rh/AC-SNI catalyst under a mild condition, which delivers a turnover frequency as high as 158.5 h.

The simplest Criegee intermediate CHOO reaction with dimethylamine and trimethylamine: kinetics and atmospheric implications.

We have used the OH laser-induced fluorescence (LIF) method to measure the kinetics of the simplest Criegee intermediate (CHOO) reacting with two abundant amines in the atmosphere: dimethylamine ((CH)NH) and trimethylamine ((CH)N). Our experiments were conducted under pseudo-first-order approximation conditions. The rate coefficients we report are (2.

Sulfur Poisoning and Self-Recovery of Single-Site Rh /Porous Organic Polymer Catalysts for Olefin Hydroformylation.

Sulfur poisoning and regeneration are global challenges for metal catalysts even at the ppm level. The sulfur poisoning of single-metal-site catalysts and their regeneration is worthy of further study. Herein, sulfur poisoning and self-recovery are first presented on an industrialized single-Rh-site catalyst (Rh /POPs).

Full-dimensional neural network potential energy surface and dynamics of the CHOO + HO reaction.

An accurate global full-dimensional machine learning-based potential energy surface (PES) of the simplest Criegee intermediate (CHOO) reaction with water monomer was developed based on the high level of extensive CCSD(T)-F12a/aug-cc-pVTZ calculations. This analytical global PES not only covers the regions of reactants to hydroxymethyl hydroperoxide (HMHP) intermediates, but also different end product channels, which facilities both the reliable and efficient kinetics and dynamics calculations. The rate coefficients calculated by the transition state theory with the interface to the full-dimensional PES agree well with the experimental results, indicating the accuracy of the current PES.

Kinetics of the Simplest Criegee Intermediate CHOO Reaction with -Butylamine.

The kinetics of the simplest Criegee intermediate (CHOO) reaction with -butylamine ((CH)CNH) was studied under pseudo-first-order conditions with the OH laser-induced fluorescence (LIF) method at the temperature range of 283-318 K and the pressure range of 5-75 Torr. Our pressure-dependent measurement showed that at 5 Torr─the lowest pressure measured in the current experiment─this reaction was under the high-pressure limit condition. At 298 K, the reaction rate coefficient was measured to be (4.

A molecular beam-surface apparatus for quantum state-resolved adsorption studies.

Understanding the microscopic mechanism of molecule-surface interaction is of great importance in the study of chemical dynamics. Yet, it remains challenging to experimentally acquire quantum state resolved results, particularly the results related to different degrees of freedom of the reactants. Here, we report the design and performance of a new apparatus for molecule-surface dynamics studies, which enable the measurement of quantum state-resolved adsorption.

Chloride-Mediated Peroxide-Free Photochemical Oxidation of Proteins (PPOP) in Mass Spectrometry-Based Structural Analysis.

Ultraviolet (UV) laser photolysis of hydrogen peroxide (HO) for the generation of hydroxyl radicals (OH) is a widely utilized strategy in the oxidation footprinting of native proteins and mass spectrometry (MS)-based structural analysis. However, it remains challenging to realize peroxide-free photochemical oxidation footprinting. Herein, we describe the footprinting of native proteins by chloride-mediated peroxide-free photochemical oxidation of proteins (PPOP).

Photochemical bromination and iodination of peptides and proteins by photoexcitation of aqueous halides.

Although halogen atoms can greatly improve the stability, selectivity, and bioactivity of proteins, direct halogenation of proteins or peptides by chemical strategy has been never achieved. Herein, we describe the developments of direct photochemical bromination and iodization of unprotected proteins and peptides in the direct irradiation device and the single-pulsed irradiation capillary reactor with biocompatible aqueous halides Br and I, respectively. These novel photochemical modifications are triggered by 193 nm laser photoexcitation of commonly photo-inert halide ions to form active radical species.

Experimental and Computational Studies of Criegee Intermediate -CHCHOO Reaction with Hydrogen Chloride.

Hydrogen chloride (HCl) contributes substantially to the atmospheric Cl; both species could affect the composition of Earth's atmosphere and the fate of pollutants. Here, we present the kinetics study for -CHCHOO reaction with HCl using experimental measurement and theoretical calculations. The experiment was conducted in a flow tube reactor at a pressure of 10 Torr and temperatures ranging from 283 to 318 K by using the OH laser-induced fluorescence (LIF) method.

Kinetics of CHOO and -CHCHOO reaction with acrolein.

The kinetics for the reactions of CH2OO and syn-CH3CHOO with acrolein, a typical unsaturated aldehyde in the atmosphere, were studied in a flash photolysis flow reactor using the OH laser-induced fluorescence (LIF) method. The bimolecular reaction rate coefficients were measured at temperatures ranging from 281 to 318 K, and pressures ranging from 5 to 200 Torr. No obvious dependence of the rate coefficients on pressure was observed under the current experimental conditions.

Environmentally friendly, durable and transparent anti-fouling coatings applicable onto various substrates.

Anti-fouling coatings are of great interest because of their unique wettability and self-cleaning property, but their widespread applications are seriously hindered by low stability, heavy usage of fluorinated compounds and low transparency, etc. Here, we report a new kind of smooth anti-fouling coatings based on methyltrimethoxysilane. The coatings were fabricated by preparing a stock solution via hydrolytic condensation of methyltrimethoxysilane in isopropanol, followed by wiping the glass slide with the non-woven fabric that sucked the stock solution.

Temperature- and pressure-dependent rate coefficient measurement for the reaction of CHOO with CHCHCHO.

Propionaldehyde is one of the most abundant aldehydes, which are an important class of volatile organic compounds. In this work, the rate coefficient of the reaction of the simplest Criegee intermediate CH2OO with propionaldehyde (CH3CH2CHO) was measured for the first time in a flash photolysis reaction tube by using the OH laser-induced fluorescence (LIF) method at temperature and pressure in the range of 283 to 318 K and 5 to 200 Torr. This reaction is observed to be pressure- and temperature-dependent.

Kinetic Studies for the Reaction of -CHCHOO with CFCH═CH.

Hydrofluoroolefins (HFOs, CFCH═CH) have great potential to replace hydrofluorocarbons (HFCs) as refrigerants. Here the kinetics for the reaction of -CHCHOO with CFCH═CH (HFO-1243zf), the simplest of HFOs, have been studied in a flash photolysis flow reactor at a total pressure of 50 Torr, by using the OH laser-induced fluorescence (LIF) method. The bimolecular reaction rate coefficients were measured at temperatures ranging from 283 to 318 K.

In situ formation of mononuclear complexes by reaction-induced atomic dispersion of supported noble metal nanoparticles.

Supported noble metal nanoclusters and single-metal-site catalysts are inclined to aggregate into particles, driven by the high surface-to-volume ratio. Herein, we report a general method to atomically disperse noble metal nanoparticles. The activated carbon supported nanoparticles of Ru, Rh, Pd, Ag, Ir and Pt metals with loading up to 5 wt.

Unimolecular Reaction Rate Measurement of -CHCHOO.

The unimolecular reactions of Criegee intermediates (CIs) are thought to be one of the significant sources of atmospheric OH radicals. However, stark discrepancies exist in the unimolecular reaction rate of the methyl-substituted CI CHCHOO, typically from ozonolysis of alkenes such as -2-butene, between the results of ozonolysis of alkene experiments and the up-to-date theoretical calculations. That no further progress has been made since the method that directly produces CIs in the laboratory was developed is mostly attributed to the existence of two conformers, - and -CHCHOO, and the methodological limitations of sensitive conformer-specific detection.

Kinetics of the reaction of the simplest Criegee intermediate with ammonia: a combination of experiment and theory.

The kinetics of the reaction of the simplest Criegee intermediate (CH2OO) with ammonia has been measured under pseudo-first-order conditions with two different experimental methods. We investigated the rate coefficients at 283, 298, 308, and 318 K at a pressure of 50 Torr using an OH laser-induced fluorescence (LIF) method. Weak temperature dependence of the rate coefficient was observed, which is consistent with the theoretical activation energy of -0.

A kinetic study of the CHOO Criegee intermediate reaction with SO, (HO), CHI and I atoms using OH laser induced fluorescence.

The OH laser induced fluorescence method was used to study the kinetics of CHOO reacting with SO, (HO), CHI and I atoms. Decay of CHOO is not strictly first-order since its self-reaction is rapid. With this consideration, we derived the rate coefficient of CHOO + SO/(HO)/CHI/I taking into account the contribution of the CHOO self-reaction.

Coherent superposition of M-states in a single rovibrational level of H2 by Stark-induced adiabatic Raman passage.

We prepare an ensemble of isolated rovibrationally excited (v = 1, J = 2) H2 molecules in a phase-locked superposition of magnetic sublevels M using Stark-induced adiabatic Raman passage with linearly polarized single-mode pump (at 532 nm, ∼6 ns pulse duration, 200 mJ/pulse) and Stokes (699 nm, ∼4 ns pulse duration, 20 mJ/pulse) laser excitation. A biaxial superposition state, given by [line]ψ(t)⟩ = 1/√(2)[[line]ν = 1, J = 2, M = -2⟩ - [line]ν = 1, J = 2, M = +2⟩], is prepared with linearly but cross-polarized pump and Stokes laser pulses copropagating along the quantization z-axis. The degree of phase coherence is measured by using the O(2) line of the H2 E,F-X (0,1) band via 2 + 1 resonance enhanced multiphoton ionization (REMPI) at 210.

Optical preparation of H2 rovibrational levels with almost complete population transfer.

Using stimulated Raman adiabatic passage (SARP), it is possible, in principle, to transfer all the population in a rovibrational level of an isolated diatomic molecule to an excited rovibrational level. We use an overlapping sequence of pump (532 nm) and dump (683 nm) single-mode laser pulses of unequal fluence to prepare isolated H2 molecules in a molecular beam. In a first series of experiments we were able to transfer more than half the population to an excited rovibrational level [N.

Thermodynamics of the enantiomers of amino acid and monosaccharide binding to fullerenol used as an artificial sweet taste receptor model.

Fullerenol was used as sweet taste receptor model to investigate the binding affinities of structurally related pairs of enantiomers by isothermal titration calorimetry (ITC). It reveals that amino acid binding with fullerenol are enthalpy-cost and entropically-driven processes, whereas enthalpy contributes to monosaccharide binding to fullerenol. Spontaneous binding of amino acids was found through two sequential steps in which the sweeter enantiomer displays larger binding constants.

Communication: transfer of more than half the population to a selected rovibrational state of H2 by Stark-induced adiabatic Raman passage.

By using Stark-induced adiabatic Raman passage (SARP) with partially overlapping nanosecond pump (532 nm) and Stokes (683 nm) laser pulses, 73% ± 6% of the initial ground vibrational state population of H(2) (v = 0, J = 0) is transferred to the single vibrationally excited eigenstate (v = 1, J = 0). In contrast to other Stark chirped Raman adiabatic passage techniques, SARP transfers population from the initial ground state to a vibrationally excited target state of the ground electronic surface without using an intermediate vibronic resonance within an upper electronic state. Parallel linearly polarized, co-propagating pump and Stokes laser pulses of respective durations 6 ns and 4.

Experimental and theoretical differential cross sections for a four-atom reaction: HD + OH → H₂O + D.

Quantum dynamical theories have progressed to the stage in which state-to-state differential cross sections can now be routinely computed with high accuracy for three-atom systems since the first such calculation was carried out more than 30 years ago for the H + H(2) system. For reactions beyond three atoms, however, highly accurate quantum dynamical calculations of differential cross sections have not been feasible. We have recently developed a quantum wave packet method to compute full-dimensional differential cross sections for four-atom reactions.

Transition-state spectroscopy of partial wave resonances in the F + HD reaction.

Partial wave resonances, quasi-bound resonance states with well-defined rotation in the transition state region of a chemical reaction, play a governing role in reaction dynamics but have eluded direct experimental characterization. Here, we report the observation of individual partial wave resolved resonances in the F + HD --> HF + D reaction by measuring the collision energy-dependent, angle- and state-resolved differential cross section with extremely high resolution, providing a spectroscopic probe to the transition state of F + HD --> HF + D. The agreement of the data with the high-level theoretical calculations confirms the sensitivity of this probe to the subtle quantum mechanical factors guiding this benchmark reaction.