Manganese‐Based Micro/Nanomotors: Synthesis, Motion, and Applications

Abstract

As emerging micro/nano‐scale devices, micro/nanomotors have been innovatively applied in the environmental and biomedical applications. In this paper, the recent advances of Mn‐based micro/nanomotors (Mn‐micro/nanomotors) in catalytic oxidation of organic contaminants and the mechanisms in decomposition of H2O2 (e.g., the generation of O2 bubbles and reactive oxygen species) are reviewed. The intrinsic characteristics and synthetic strategies of Mn‐based materials are discussed, aiming to gain comprehensive understandings on the asymmetric design of micro/nanomotors. Mn‐micro/nanomotors have many advantages such as flexible structures, biocompatibility, powerful motion, long lifetime, and low‐cost as compared to noble‐metal micro/nanomotors. These merits fulfil Mn‐micro/nanomotors great promises from proof‐of‐concept studies to realistic applications, including pollutant decomposition, trace detection of heavy metal ions, oil removal, drug delivery, isolation of biological targets, and killing bacteria and cancer cells. The great flexibility in fabrication enables diverse and innovative strategies to address challenges for Mn‐micro/nanomotors, including high consumption of H2O2 and non‐directional motion. Meanwhile, a perspective of Mn‐micro/nanomotors in water remediation by coupling the motors with other Fenton/Fenton‐like systems to enhance the catalytic activity and to yield more reactive oxygen species is presented. Directions to the design of on‐demand H2O2‐fueled Mn‐micro/nanomotors for advanced purification of organic contaminants in aquatic systems are also proposed.

Activation of O2 over three-dimensional manganese oxide nanoprisms under ambient conditions towards oxidative removal of aqueous organics

“…47,48 Among manganese oxides, MnO 2 materials have been applied in adsorption, catalysis and battery materials due to their porosity, crystallinity, mixed valence and semi-conductivity. [49][50][51] In the case of catalysis, the structural dimension of a catalytic material plays a dominant role in heterogeneous catalytic processes from the perspective of adsorption, diffusion, and mass transfer of reactants. [52][53][54][55] For instance, 1D α-MnO 2 is usually used as a catalyst for the activation of ozone and persulfates in AOPs, while 2D δ-MnO 2 catalysts are frequently used for VOC removal, such as formaldehyde oxidation.…”

Fluid Field Modulation in Mass Transfer for Efficient Photocatalysis

“…Based on the investigations on mass transfer process via theoretical simulation calculation, more and more photocatalysts with ingenious structures and subtle functions were developed to facilitate photocatalytic activity via manipulating kinetic process of mass transfer. [142][143][144] Among them, photocatalyst-based micro/nanomotors and cilia-like photocatalyst films with viable structure design have aroused intensive attentions, exhibiting great potential in promoting mass transfer and thus enhancing photocatalytic performance, which will be summarized and discussed below. [145,146]…”

Reactive oxygen species on transition metal-based catalysts for sustainable environmental applications

“…96,97 However, the O]O bond of O 2 has a high bond energy (498 kJ mol À1 ) that must be overcome to initiate O 2 -mediated oxidation reactions. Transition metal-based catalysts (e.g., transition metal complexes, 98 TMO, 99 and transition metal suldes 100 ) critically improve the reactivity of O 2 by effectively adsorbing the O 2 molecules and weakening the O]O bond of O 2 through efficient charge transfer, and photocatalysis is frequently used to promote electron transfer in the activation of O 2 . 101 (4) Lattice oxygen: metal oxides are the carrier of O L and they maintain the lattice structure throughout the reaction.…”

“…Transition metal-based catalysts ( e.g. , transition metal complexes, 98 TMO, 99 and transition metal sulfides 100 ) critically improve the reactivity of O 2 by effectively adsorbing the O 2 molecules and weakening the OO bond of O 2 through efficient charge transfer, and photocatalysis is frequently used to promote electron transfer in the activation of O 2 . 101…”