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Due to their low cost, good biocompatibility, and ease of structural modification, organic long-persistent luminescence (LPL) materials have garnered significant attention in organic light-emitting diodes, biological imaging, information encryption, and chemical sensing. Efficient charge separation and carrier migration by the host–guest structure or using polymers and crystal to build rigid environments are effective ways of preparing high-performance materials with long-lasting afterglow. In this study, four types of crystalline materials (MODPA: DDF-O, MODPA: DDF-CHO, MODPA: DDF-Br, and MODPA: DDF-TRC) were prepared by a convenient host–guest doping method at room temperature under ambient conditions, i.e., in the presence of oxygen. The first three types exhibited long-lived charge-separated (CS) states and achieved visible LPL emissions with durations over 7, 4, and 2 s, respectively. More surprisingly, for the DDF-O material prepared with PMMA as the polymer substrate, the afterglow time of DDF-O: PMMA was longer than 10 s. The persistent room-temperature phosphorescence effect caused by different CS state generation efficiencies and rigid environment were the main reason for the difference in LPL duration. The fourth crystalline material was without charge separation and exhibited no LPL because it was not a D-A system. The research results indicate that the CS state generation efficiency and a rigid environment are the key factors affecting the LPL properties. This work provides new understandings in designing organic LPL materials. [ABSTRACT FROM AUTHOR]

Accurately measuring water holdup in horizontal wells is crucial for effectively using heavy oil reservoirs. The capacitance method is among the most widely used and accurate techniques. However, the absence of suitable insulating materials at high temperatures and pressures limits the effectiveness of capacitive water holdup measurement in heavy oil thermal recovery. This study introduces a new composite material based on an aviation-grade, special glass glaze as the insulating medium doped with inorganic components (CaSO4, MgSO4, Ca(OH)2, and SiO2). This new composite material demonstrates outstanding insulating performance under high-temperature and high-pressure conditions in water. A water environment with a high temperature of 350 °C and a pressure of 12 MPa considerably enhances the composite material's insulation. After 72 h of continuous use, the insulation performance remains 0.3 MΩ. The layers exhibit improved insulation and stability, maintaining integrity through five consecutive temperature shocks in 500 °C air and 20 °C water. XRD, IR, SEM, and TEM analyses reveal that the new composite material is amorphous after firing and that the addition of inorganic components improves the bonding between the glass glaze components and contributes to a denser structure. Simultaneously, SEM and TEM analyses indicate that adding inorganic components results in a smoother, crack-free, and more compact surface of the special glass glaze. This enhancement is crucial for the material's long-term stability in high-temperature and high-pressure water environments. [ABSTRACT FROM AUTHOR]

The pulsed-laser photolysis/laser-induced fluorescence method is used to study the kinetics of the reaction of NH2 with H2O2 to yield a second-order rate constant of (2.42 ± 0.55) × 10−14 cm3 molecule−1 s−1 at 412 K in 10–22 mbar of Ar bath gas. There are no prior measurements for comparison. To check this value and enable reliable extrapolation to other temperatures, we also compute thermal rate constants for this process over the temperature range 298–3000 K via multi-structural canonical variational transition-state theory with small-curvature multidimensional tunneling (MS-CVT/SCT). The CVT/SCT rate constants are derived using a dual-level direct dynamics approach utilizing single-point CCSD(T)-F12b/cc-pVQZ-F12 energies—corrected for core-valence and scalar relativistic effects—and M06-2X/MG3S geometries, gradients, and Hessians—for all stationary and non-stationary points along the reaction path. The multistructural method with torsional anharmonicity, based on a coupled torsional potential, is then employed to calculate correction factors for the rate constants, accounting for the comprehensive effects of torsional anharmonicity on the kinetics of this reaction system. The final MS-CVT/SCT rate constants are found to be in good agreement with our measurements and can be expressed in modified Arrhenius form as 2.13 × 10−15 (T/298 K)4.02 exp(−513 K/T) cm3 molecule−1 s−1 over the temperature range of 298–3000 K. [ABSTRACT FROM AUTHOR]

The rate coefficient k 1 for NH 2 + N 2 H 4 was measured to be (5.4 ± 0.4) × 10−14 cm3 molecule−1 s−1 at 296 K. NH 2 was generated by pulsed laser photolysis of NH 3 at 193 nm, and monitored as a function of time by pulsed laser-induced fluorescence excited at 570.3 nm under pseudo-first order conditions in the presence of excess N 2 H 4 in an Ar bath gas. This reaction was also investigated computationally, with geometries and scaled frequencies obtained with M06-2X/6-311+G(2df,2p) theory, and single-point energies from CCSD(T)-F12b/cc-pVTZ-F12 theory, plus a term to correct approximately for electron correlation through CCSDT(Q). Three connected transition states are involved and rate constants were obtained via Multistructural Improved Canonical Variational Transition State Theory with Small Curvature Tunneling. Combination of experiment and theory leads to a recommended rate coefficient for hydrogen abstraction of k 1 = 6.3 × 10−23 T3.44 exp(+289 K/T) cm3 molecule−1 s−1. The minor channel for H + N 2 H 4 forming NH 2 + NH 3 was characterized computationally as well, to yield 5.0 × 10−19 T2.07 exp(-4032 K/T) cm3 molecule−1 s−1. These results are compared to several discordant prior estimates, and are employed in an overall mechanism to compare with measurements of half-lives of hydrazine in a shock tube. [ABSTRACT FROM AUTHOR]

The atomic Cl kinetics was monitored by using the laser flash photolysis resonance fluorescence technique. The kinetic isotope effects in both directions support the mechanism for the reaction of phenyl with HCl with a recommended rate constant for Cl benzene derived from high-temperature measurements and data at room temperature.

The first determination of the temperature dependence of the rate constant [k.sub.1] for the endothermic reaction is presented and compared with the isoelectronic and also endothermic reaction. Ground-state CI atoms were generated by 193 nm excimer laser photolysis of CCl4 and reacted under pseudo-first-order conditions with excess N[H.sub.3].

The rate constant for the reaction of the isocyanato radical, NCO(X(super 2)II) with chlorine atoms, Cl((super 2)P) is measured at 293 and 345 K respectively. The rate constants for this reaction is found to be (2.4 plusmn 1.6) x 10(super -13) and (1.9 plusmn 1.2) x 10(super -13) cm(super 3) molecules(super -1) S(super -1) at 293 and 345 K respectively where the uncertainties include both random and systematic error.

The rate constant for the reaction of the isocyanate radical, NCO (X(super 2)II), with oxygen atoms,O((super3)P) is measured at a temperature of 292 plusmn 2 K to be (2.1 plusmn 0.76) x 10(super -10) cm(super 3) molecule(super-1) s,(super -1) where the error estimate contains both systematic and random errors. The rate constant is found to be independent of both pressure over the pressure range of 1.5 -7.6 Torr and the nature of a third-body collision partner.

The geometry of N2S was obtained at the CCSD(T)/aug-cc-pV(T + d)Z level of theory and energies with coupled-cluster single double triple (CCSD(T)) and basis sets up to aug-cc-pV(6 + d)Z. After correction for anharmonic zero-point energy, core-valence correlation, correlation up to CCSDT(Q) and relativistic effects, D0 for the N-S bond is estimated as 71.9 kJ mol-1, and the corresponding thermochemistry for N2S is ΔfH0°=205.4 kJ mol-1 and ΔfH298°=202.6 kJ mol-1 with an uncertainty of ±2.5 kJ mol-1. Using CCSD(T)/aug-cc-pV(T + d) theory the minimum energy crossing point between singlet and triplet potential energy curves is found at r(N-N) ≈ 1.105 Å and r(N-S) ≈ 2.232 Å, with an energy 72 kJ mol-1 above N2 + S(3P). Application of Troe's unimolecular formalism yields the low-pressure-limiting rate constant for dissociation of N2S k0 = 7.6 × 10-10 exp(-126 kJ mol-1/RT) cm3 molecule-1 s-1 over 700-2000 K. The estimated uncertainty is a factor of 4 arising from unknown parameters for energy transfer between N2S and Ar or N2 bath gas. The thermochemistry and kinetics were included in a mechanism for CO/H2/H2S oxidation and the conclusion is that little NO is produced via subsequent chemistry of NNS. [ABSTRACT FROM AUTHOR]

The rate constant for the reaction of the cyanato radical with the methyl radical was measured and possible products of the reaction were explored. The observed C(sub 2)H(sub 6) temporal profile always peaked at significantly higher concentrations than the model predictions, while the recombination channel was the most likely product channel producing CH(sub 3)NCO and CH(sub 3)OCN.

ABSTRACT A detailed chemical kinetic model for oxidation of acetylene at intermediate temperatures and high pressure has been developed and evaluated experimentally. The rate coefficients for the reactions of C2H2 with HO2 and O2 were investigated, based on the recent analysis of the potential energy diagram for C2H3 + O2 by Goldsmith et al. and on new ab initio calculations, respectively. The C2H2 + HO2 reaction involves nine pressure- and temperature-dependent product channels, with formation of triplet CHCHO being dominant under most conditions. The barrier to reaction for C2H2 + O2 was found to be more than 50 kcal mol−1 and predictions of the initiation temperature were not sensitive to this reaction. Experiments were conducted with C2H2/O2 mixtures highly diluted in N2 in a high-pressure flow reactor at 600-900 K and 60 bar, varying the reaction stoichiometry from very lean to fuel-rich conditions. Model predictions were generally in satisfactory agreement with the experimental data. Under the investigated conditions, the oxidation pathways for C2H2 are more complex than those prevailing at higher temperatures and lower pressures. Acetylene is mostly consumed by recombination with H to form vinyl (reducing conditions) or with OH to form a CHCHOH adduct (stoichiometric to lean conditions). Both C2H3 and CHCHOH then react primarily with O2. The CHCHOH + O2 reaction leads to formation of significant amounts of glyoxal (OCHCHO) and formic acid (HOCHO), and the oxidation chemistry of these intermediates is important for the overall reaction. [ABSTRACT FROM AUTHOR]