Manganese Oxide Based Catalytic Micromotors: Effect of Polymorphism on Motion

Abstract

Manganese oxide (MnO) has recently emerged as a promising alternate material for the fabrication of self-propelled micromotors. Platinum (Pt) has been traditionally used as a catalytic material for this purpose. However, the high cost associated with Pt restricts its widespread use toward practical applications where large amounts of material are required. MnO exists in different crystalline forms (polymorphs), which govern its catalytic behavior. In spite of this, the recent reports on MnO based micromotors have seldom reported on the polymorphic form involved. In the present work, we synthesized six different types of MnO based micromotors, which represent different geometrical designs (i.e., spherical, rod-like, and tube-like microparticles) and polymorphs, and characterized their motion behavior in different chemical environments. Out of all micromotors tested, the hollow spherical MnO microparticles reached the maximum velocity of ∼1600 μm s, which represents the fastest MnO based catalytic micromotor reported until date. The findings of this study will have a profound impact on the design and application of the next-generation synthetic micro- and nanomotors based on MnO as a low-cost and environment friendly material.

Electrochemical Deposition Tailors the Catalytic Performance of MnO2‐Based Micromotors

“…Among a diversity of polymorphs including α, β, γ, and ε ‐MnO 2 types, ramsdellite MnO 2 (R‐MnO 2 ) has a better performance as a catalyst. Besides, rhodochrosite MnCO 3 generates as a byproduct, probably following the reaction of…”

“…The catalytic degradation combined with adsorptive bubble separation resulted in remarkable decolorization of dye‐contaminated waters and over 90% of azo‐dyes was decolorized in 1 h. Moreover, Feng and co‐workers synthesized MnO 2 /graphene micromotors with “sandwich‐like structure” via a one‐step hydrothermal method and poly(3,4‐ethylenedioxythiophene) (PEDOT)/MnO 2 tubular microrockets by potentiostatic deposition, both of which could move rapidly in biological media . Safdar et al synthesized MnO 2 ‐based micromotors with different shapes by both chemical reaction and electrochemical deposition, and found electrochemically prepared micromotors exhibit high speed but undergo self‐destruction with limited lifetime . Most recently, Fe 2 O 3 ‐decorated SiO 2 /MnO 2 microjets were obtained by chemical fabrication for the simultaneous removal of industrial organic waste and heavy metals present in wastewater …”

MnO2 Submicroparticles from Chinese Brush and Their Application in Treatment of Methylene Blue Contaminated Wastewater

“…[45][46][47] As a kind of inorganic nanomaterials, MnO 2 have drawn much attention because of their flexible structures and unique properties and have been applied to catalysis, ion exchange, supercapacitors, molecule adsorption, biosensors and so on. 48 One of the recent applications has fo- [49][50][51][52] And micromotors containing manganese oxide and noble metal or graphene have also been studied. [53][54][55] In this work, by consideration of its special microstructure, abundant component of protein, we choose ESM as the biotemplate to help synthesize MnO 2 .…”

Core–shell microspheres for the ultrafast degradation of estrogen hormone at neutral pH

“…Since the intensity of the core peaks was too high, the external shell of MnO 2 was not appreciated, which is in agreement with previously reported works. 20,21 The XRD patterns of the iron oxide obtained by the hydrothermal reaction indicate the formation of a-goethite FeOOH phase (JCPDS no. 029-0713).…”

“…X-ray diffraction data was collected in the 2q range between 20 and 80 using a scan rate of 0.05 by 2 s. The light absorption properties were measured by using a UV-Vis diffuse reectance spectrophotometer (Perkin Elmer Lambda 950 UV-Vis) with a wavelength range of 250-800 nm. A Zeiss Auriga microscope equipped with energy-dispersive X-ray (EDX) detector was used to perform scanning electron microscopy (SEM) and EDX analysis.…”