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Laser parameters effects of pump-probe pulse on improvements of spectral continuum and attosecond pulse signal from H-2(+)
No full textGenerally, by properly choosing the delay time of the pump-probe field, the harmonic yield from H-2(+) can be enhanced due to the charge-resonance-enhanced-ionization. In this paper, through controlling the laser parameters of pump-probe pulse, the improvements of spectral continuum and attosecond pulse signal from H-2(+) have been further investigated. For the case of controlling pump pulse, it is found that the harmonic yield of H-2(+) can be enhanced as the pump pulse duration increases. However, as the pump wavelength increases, although the harmonic cutoff can be extended, the harmonic yield is decreased. Furthermore, when the carrier envelope phase of pump pulse is chosen to be 1.0 pi, the intensity of spectral continuum can be further enhanced slightly. For the case of controlling probe pulse, it is shown that the harmonic cutoff can be extended when the probe pulse duration increases. Moreover, by properly adding a down-chirp in the probe pulse, the harmonic cutoff can be further extended, showing a broader spectral continuum with a stable intensity. Furthermore, with the introduction of inhomogeneous effect of the laser field, a larger harmonic cutoff can be found and a spectral continuum with a bandwidth of 116 eV can be obtained. Moreover, the signal of this spectral continuum is only contributed by a single harmonic emission peak. Finally, through the Fourier transformation of some selected harmonics on this spectral continuum, a single attosecond pulse with the duration of 48 as can be obtained
An organic-base catalyzed asymmetric 1,4-addition of tritylthiol to in situ generated aza-o-quinone methides at the H2O/DCM interface (vol 55, pg 2668, 2019)
No full textCorrection for 'An organic-base catalyzed asymmetric 1,4-addition of tritylthiol to in situ generated aza-o-quinone methides at the H2O/DCM interface' by Xianghui Liu et al., Chem. Commun., 2019, 55, 2668-2671
Microenvironment Engineering of Ruthenium Nanoparticles Incorporated into Silica Nanoreactors for Enhanced Hydrogenations
No full textIt is a challenging task to promote the activity and selectivity of a catalyst via precisely engineering the microenvironment, an important factor related with the catalytic performance of natural catalysts. Motivated by the water effect in promoting the catalytic activity explored in this work, a nanoreactor modified with phosphine ligand enabled the efficient hydrogenation of benzoic acid (BA) over Ru nanoparticles (NPs) in organic solvent under mild conditions, which cannot be achieved in unmodified nanoreactors. Both density functional theory (DFT) calculations and catalytic performance tests showed that the phosphine ligands can manipulate the adsorption strength of BA on Ru NPs by tuning the surface properties as well as preferentially interacting with the carboxyl of BA. The insights obtained in the present study provide a novel concept of nanoreactor design by anchoring ligands near catalytically active centers
Enhancing single-molecule magnet behaviour through decorating terminal ligands in Dy-2 compounds
No full textThe utilization of two isomorphic ligands with different substituents leads to two centrosymmetric Dy-III dimers, namely, [Dy-2(bfbpen)(2)(H2O)(2)]center dot 2I(-) (1) and [Dy-2(bcbpen)(2)(H2O)(2)]center dot 2I(-)center dot 0.5H(2)O (2) (H(2)bfbpen = N,N '-bis-(2-hydroxy-5-fluoro-benzyl)-N,N '-bis-(pyridin-2-ylmethyl)ethylenediamine and H(2)bcbpen = N,N '-bis-(2-hydroxy-5-chloro-benzyl)-N,N '-bis-(pyridin-2-ylmethyl)ethylenediamine). Although Dy ions in both compounds uniformly exhibit a square-antiprism geometry, the critical difference found in the terminal substituents of the two ligands fine-tunes the local crystal field around Dy centers and the dinuclear molecular structures of 1 and 2. Magnetic investigations unveil that both 1 and 2 display dynamic magnetic relaxation of single-molecule magnet (SMM) behaviour with different energy barriers of 20.9 K for 1 and 72.7 K for 2 under a zero direct-current (dc) field, as well as 26.9 K for 1 under a 1200 Oe dc field. Compared to 1, the stronger uniaxial anisotropy and magnetic exchange in 2 render it a better SMM as evidenced by the higher energy barrier. Ab initio calculations are also performed on both Dy-2 compounds to rationalize the observed discrepancy in their magnetic behaviours. The contribution illustrates that the SMM behaviour could be effectively enhanced by means of deliberate local structural manipulation
Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt-Hydroxyapatite Catalyst
No full textAromatic alcohols are essential components of many solvents, coatings, plasticizers, fine chemicals, and pharmaceuticals. Traditional manufacturing processes involving the oxidation of petroleum-derived aromatic hydrocarbons suffer from low selectivity due to facile overoxidation reactions which produce aromatic aldehydes, acids, and esters. Here we report a Co-containing hydroxyapatite (HAP) catalyst that converts ethanol directly to methylbenzyl alcohols (MB-OH, predominantly 2-MB-OH) at 325 degrees C. The dehydrogenation of ethanol to acetaldehyde, which is catalyzed by Co2+, has the highest reaction barrier. Acetaldehyde undergoes rapid, HAP-catalyzed condensation and forms the key intermediate, 2-butenal, which yields aromatic aldehydes through self-condensation and then MB-OH via hydrogenation. In the presence of Co2+, 2-butenal is selectively hydrogenated to 2-butenol. This reaction does not hinder aromatization because cross-coupling between 2-butenal and 2-butenol leads directly to MB-OH without passing through MB=O. Using these insights a dual-bed catalyst configuration was designed for use in a single reactor to improve the aromatic alcohol selectivity. Its successful use supports the proposed reaction mechanism