Generation of highly reactive oxygen species on metal-supported MgO(100) thin films

Song, Zhenjun; Fan, Jing; Shan, Yueyue; Ng, Alan Man Ching; Xu, Hu

doi:10.1039/c6cp03236b

Cited by 17 publications

(8 citation statements)

References 47 publications

(73 reference statements)

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“…Thus, the vdW correction was used in the calculations. On the contrary, all possible adsorption structures of O 2 on the tellurene surface have been considered, and the results suggest that the O 2 molecule prefers to chemisorb on the surface because there is a significant charge transfer between O 2 and tellurene, 50 which is similar to the case of O 2 adsorption on bilayer β-Te. 51 The dissociated O atoms are located at two Te−Te bridge sites (see Figure 2b One dissociated O atom occupies the vacancy site, while the other one is located at a Te−O−Te bridge site as shown in Figure 2e, similar to O 2 adsorption on the surface of bilayer β-Te.…”

Section: Resultsmentioning

confidence: 98%

Surface Adsorption and Vacancy in Tuning the Properties of Tellurene

Gan

Wang

et al. 2020

ACS Appl. Mater. Interfaces

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The emerging two-dimensional tellurene has been demonstrated to be a promising candidate for photoelectronic devices. However, there is a lack of comprehensive insight into the effects of vacancies and common adsorbates (i.e., O 2 and H 2 O) in ambient conditions, which play a crucial role in semiconducting devices. In this work, with the aid of firstprinciples calculations, we demonstrate that H 2 O and O 2 molecules behave qualitatively differently on tellurene, while water adsorption can be remarkably promoted by adjacent preadsorbed O 2 . Upon the formation of Te vacancies, the adsorption of both O 2 and H 2 O molecules is enhanced. More importantly, the existence of H 2 O and Te vacancies can dramatically facilitate the dissociation of O 2 , suggesting that tellurene may be readily oxidized in humid conditions. In addition, it is found that the electronic properties of tellurene are well preserved upon either H 2 O or O 2 adsorption on the surface. In sharp contrast, vacancies enable significant modification on the band structure. Specifically, an indirect-to-direct band gap transition is found at a vacancy concentration of 5.3%.

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Section: Resultsmentioning

confidence: 98%

Surface Adsorption and Vacancy in Tuning the Properties of Tellurene

Gan

Wang

et al. 2020

ACS Appl. Mater. Interfaces

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“…37 By coadsorption of water and oxygen, a series of highly reactive oxygen species including superoxide, hydroperoxide, hydroxyl and single oxygen adatoms are formed on metal-supported magnesia films. 38 The X-ray photoelectron and Auger spectroscopy also verified the greatly enhanced dissociation behavior of water on ultrathin magnesia film. 39 Rational manipulation of interfacial local structure by introducing vacancies and ligand field effect, which changes the charge distribution at the oxide surface, play important role in controlling the surface reactions.…”

Section: Introductionmentioning

confidence: 78%

Homolytic cleavage of water on magnesia film promoted by interfacial oxide−metal nanocomposite

Song

Zhao

Wang

et al. 2019

Applied Surface Science

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The atomic-scale insights into the interaction of water with oxide surface are essential for elucidating the mechanism of physiochemical processes in various scientific and practical fields, since the water is ubiquitous and coats multifarious material surface under ambient conditions. By utilizing periodic density functional theory calculations with van der Waals corrections, herein we report for the first time the energetically and thermodynamically favorable homolytic dissociative adsorption behavior of water over magnesia (001) films deposited on metal substrate. The water adsorption on pristine magnesia (001) is quite weak and the heterolytic dissociation is the only fragmentation pathway, which is highly endothermic with large activation barrier of 1.167 eV. The binding strength for the molecular and dissociative adsorption configurations of water on MgO(001)/Mo(001) are significantly larger than corresponding configurations on bare magnesia (001). The homolytic dissociative adsorption energy of water on monolayer oxide is calculated to be -1.192 eV, which is even larger than all the heterolytic dissociative adsorption states. With the increase of the oxide thickness, the homolytic dissociative adsorption energy decreases promptly, indicating the nanoscale of oxide film play a crucial role in homolytic splitting of water.The homolytic dissociative adsorption structure could be obtained by transformation reaction from heterolytic dissociative adsorption structure, presenting activation barriers 0.733, 1.103, 1.306, 1.571, and 1.849 eV for reactions on 1 ML -5 ML films.Bader charge population and differential charge density contours are analyzed to interpret charge transfer mechanism in the composite structure and between surface and adsorbates. The electronic states of dissociative adsorbates are located at lower relative energy ranges, with decreasing film thickness, which further implies the ultrathin oxide films are more favorable for stabilizing the produced hydride and hydroxyl species. The bonding characteristics between hydride/hydroxyl of homolytically dissociated water with ultrathin magnesia (001) are uncovered by characterizing the electron localization function and particular occupied orbitals. It is anticipated that the results here could provide inspiring clue and versatile strategy for enhancing chemical reactivity and properties of insulating oxide toward homolytic water-splitting processes involved in novel and unprecedented applications.

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“…Trapped electrons can be transferred to surface-adsorbed O 2 molecules to produce O 2 •– . O 2 •– -induced antimicrobial activity , of various MgO nanostructures such as microrods, nanoparticles, and microspheres has been examined by researchers. ,− While O 2 •– generation by most of the nanostructures was studied under light irradiation, a previous study shows that ZnO nanoparticles could facilitate O 2 •– generation in the dark due to the migration of trapped electrons at the surface of ZnO . A recent study by Hao et al also illustrated that oxygen vacancies in MgO nanostructures can produce O 2 •– in the dark .…”

Section: Results and Discussionmentioning

confidence: 99%

Effect of Morphology and Concentration on Crossover between Antioxidant and Pro-oxidant Activity of MgO Nanostructures

et al. 2018

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The toxicity of nanomaterials can sometimes be attributed to photogenerated reactive oxygen species (ROS), but these ROS can also be scavenged by nanomaterials, yielding opportunities for crossover between the properties. The morphology of nanomaterials also influences such features due to defect-induced properties. Here we report morphology-induced crossover between pro-oxidant activity (ROS generation) and antioxidant activity (ROS scavenging) of MgO. To study this process in detail, we prepared three different nanostructures of MgO (nanoparticles, nanoplates, and nanorods) and characterized them by HRTEM. These three nanostructures effectively generate superoxide anions (O2 •–) and hydroxyl radicals (•OH) at higher concentrations (>500 μg/mL) but scavenge O2 •– at lower concentrations (40 μg/mL) with successful crossover at 200 μg/mL. Nanorods of MgO generate the highest levels of O2 •–, whereas nanoparticles scavenge O2 •– to the highest extent (60%). Photoluminescence studies reveal that such crossover is based on the suppression of F2+ and the evolution of F+, F2 +, and F2 3+ defect centers. The evolution of these defect centers reflects the antibacterial activity of MgO nanostructures which is initiated at 200 μg/mL against Gram-positive S. aureus ATCC 29737 and among different bacterial strains including Gram-positive B. subtilis ATCC 6633 and M. luteus ATCC 10240 and Gram-negative E. coli ATCC K88 and K. pneumoniae ATCC 10031. Nanoparticles exhibited the highest antibacterial (92%) and antibiofilm activity (17%) against B. subtilis ATCC 6633 in the dark. Interestingly, the nitrogen-centered free radical DPPH is scavenged (100%) by nanoplates due to its large surface area (342.2 m2/g) and the presence of the F2 + defect state. The concentration-dependent interaction with an antioxidant defense system (ascorbic acid (AA)) highlights nanoparticles as potent scavengers of O2 •– in the dark. Thus, our findings establish guidelines for the selection of MgO nanostructures for diverse therapeutic applications.

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Generation of highly reactive oxygen species on metal-supported MgO(100) thin films

Cited by 17 publications

References 47 publications

Surface Adsorption and Vacancy in Tuning the Properties of Tellurene

Surface Adsorption and Vacancy in Tuning the Properties of Tellurene

Homolytic cleavage of water on magnesia film promoted by interfacial oxide−metal nanocomposite

Effect of Morphology and Concentration on Crossover between Antioxidant and Pro-oxidant Activity of MgO Nanostructures

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