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Tryptophan (Trp), tyrosine (Tyr), and histidine (His), known as three essential amino acids, are also precursors of vital neurotransmitters in brain nutrient metabolism. In this study, we have conducted a gas-phase study on their interactions with silver ions by a customized reflectron time-of-flight mass spectrometer combined with a magnetron sputtering source and a downstream flow tube reactor. It is unveiled that these physiological molecules are readily dissociated in the presence of Ag+ ions, giving rise to fragmentation and recombination products. Utilizing density functional theory calculations, we have clarified the reaction mechanism of the dissociative process. It is found that the silver ions facilitate the hydrogen atom transfer reaction followed by competitive Cα–Cβ and Cβ–Cγ bond dissociation. This study enriches the basic and precise properties of such neurotransmitter molecules and helps us understand similar physiological mechanisms in vivo. [ABSTRACT FROM AUTHOR]

Bulk cobalt does not react with water at room temperature, but cobalt nanometals could yield corrosion at ambient conditions. Insights into the cobalt cluster reactions with water and oxygen enable us to better understand the interface reactivity of such nanometals. Here we report a comprehensive study on the gas-phase reactions of Con±/0 clusters with water and oxygen. All these Con±/0 clusters were found to react with oxygen, but only anionic cobalt clusters give rise to water dissociation whereas the cationic and neutral ones are limited to water adsorption. We elucidate the influences of charge states, bonding modes and dehydrogenation mechanism of water on typical cobalt clusters. It is unveiled that the additional electron of anionic Con– clusters is not beneficial to H2O adsorption, but allows for thermodynamics- and kinetics-favourable H atom transfer and dehydrogenation reactions. Apart from the charge effect, size effect and spin effect play a subtle role in the reaction process. The synergy of multiple metal sites in Con– clusters reduces the energy barrier of the rate-limiting step enabling hydrogen release. This finding of water dissociation on cobalt clusters put forward new connotations on the activity series of metals, providing new insights into the corrosion mechanism of cobalt nanometals. Cobalt-based materials have a wide range of applications from information storage to electromagnetic absorbers in aerospace manufacturing, but the corrosion of cobalt nanosurfaces is poorly explored. Here, the authors combine mass spectrometry and DFT to study gas-phase reactions of Con±/0 (n = 1–30) with water and oxygen and find that only anionic cobalt clusters give rise to water dissociation, whereas the cationic and neutral ones are limited to water adsorption. [ABSTRACT FROM AUTHOR]

The reactivity of Nbn+ (1 ≤ n ≤ 21) clusters with B2H6 is studied by using a self-developed multiple-ion laminar flow tube reactor combined with a triple quadrupole mass spectrometer (MIFT-TQMS). The Nbn+ clusters were generated by a magnetron sputtering source and reacted with the B2H6 gas under fully thermalized conditions in the downstream flow tube where the reaction time was accurately controlled and adjustable. The complete and partial dehydrogenation products NbnB1–4+ and NbnB1–4H1,2,4+ were detected, indicative of the removal of H2 and likely BHx moieties. Interestingly, these NbnB1–4+ and NbnB1–4H1,2,4+ products are limited to 3 ≤ n ≤ 6, suggesting that the small Nbn+ clusters are relatively more reactive than the larger Nbn>6+ clusters under the same conditions. By varying the B2H6 gas concentrations and the reactant doses introduced into the flow tube, and by changing the reaction time, we performed a detailed analysis of the reaction dynamics in combination with the DFT-calculated thermodynamics. It is demonstrated that the lack of cooperative active sites on the Nb1+ cations accounts for the weakened dehydrogenation efficiency. Nb2+ forms partial dehydrogenation products at a faster rate. In contrast, the Nbn>6+ clusters are subject to more flexible vibrational relaxation which disperse the energy gain of B2H6-adsorption and thus are unable to overcome the energy barriers for subsequent hydrogen atom transfer and H2 release. [ABSTRACT FROM AUTHOR]