Synthesis of {111} Facet-Exposed MgO with Surface Oxygen Vacancies for Reactive Oxygen Species Generation in the Dark

Abstract

Seeking a simple and moderate route to generate reactive oxygen species (ROS) for antibiosis is of great interest and challenge. This work demonstrates that molecule transition and electron rearrangement processes can directly occur only through chemisorption interaction between the adsorbed O and high-energy {111} facet-exposed MgO with abundant surface oxygen vacancies (SOVs), hence producing singlet oxygen and superoxide anion radicals without light irradiation. These ROS were confirmed by electron paramagnetic resonance, in situ Raman, and scavenger experiments. Furthermore, heat plays a crucial role for the electron transfer process to accelerate the formation of ·O, which is verified by temperature kinetic experiments of nitro blue tetrazolium reduction in the dark. Therefore, the presence of oxygen vacancy can be considered as an intensification of the activation process. The designed MgO is acquired in one step via constructing a reduction atmosphere during the combustion reaction process, which has an ability similar to that of noble metal Pd to activate molecular oxygen and can be used as an effective bacteriocide in the dark.

Ozonation inactivation of Escherichia coli in aqueous solution over MgO nanocrystals: modelling and mechanism

“…The results indicate that O 2 •− was not apparently involved in O 3 alone but was one of the ROS in each of the MgO/O 3 processes. By comparisons, it was found that the formation of O 2 •− was due to the existence of MgO, which was also reported by others . Hao et al .…”

“…Hao et al . proved that superoxide anion radicals could be produced on the surface of MgO in the molecule transition and electron rearrangement processes, which occurred through the interaction between the chemisorbed O 2 and the MgO with abundant surface oxygen vacancies (SOVs) without light irradiation . Based on the above results, it is deduced that MgO enhances O 3 mass transfer from gas to liquid phase by promoting the decomposition of aqueous O 3 .…”

“…31,33 Hao et al proved that superoxide anion radicals could be produced on the surface of MgO in the molecule transition and electron rearrangement processes, which occurred through the interaction between the chemisorbed O 2 and the MgO with abundant surface oxygen vacancies (SOVs) without light irradiation. 33 Based on the above results, it is deduced that MgO enhances O 3 mass transfer from gas to liquid phase by promoting the decomposition of aqueous 3 in the presence of MgO. According to the above analysis, two mechanisms are involved: direct reaction with ozone and indirect reaction with radicals produced from the interaction between ozone or oxygen and MgO.…”

High-Efficiency Catalysis of Peroxymonosulfate by MgO for the Degradation of Organic Pollutants

“…Optical investigations can reveal very useful information to understand the physical properties of materials [23,49]; as a result, photoluminescence spectroscopy (PL) of three kinds of MgO with different particle sizes are given in Figure 8. With an excitation wavelength of 325 nm, the PL spectra exhibit an intrinsic emission peak at 372 nm, a purple emission resulted from adsorbed oxygen species centered around 400 nm, and two blue emission around 454 and 469 nm, which are attributed to the oxygen vacancy (F center) [50,51]. When the valence band of MgO is excited by light, some of photogenerated electrons are trapped by oxygen vacancies.…”

Synthesis of nano-octahedral MgOviaa solvothermal-solid-decomposition method for the removal of methyl orange from aqueous solutions

“…15 However, in these synthetic procedures, 9,10,15 researchers have paid less attention to the crystal facet of nano MgO; MgO usually grows into a cubic structure with (100) facets. 16 In the past few years, numerous studies have focused on MgO with the (111) polar facet due to its higher reactivity in catalysis 17,18 and antibacterial 19 applications. However, the reports about nano MgO with (111) polar facets and its properties are rare.…”