Synthesis, phase transformation, and morphology of hausmannite Mn3O4 nanoparticles: photocatalytic and antibacterial investigations

Abstract

Nano structured Hausmannite (Mn 3 O 4) has efficacious applications in numerous fields, such as catalytic, medical, biosensors, waste water remediation, energy storage devices etc. The potential application in wastewater treatment is due to its distinct structural features combined with fascinating physicochemical properties. Another area of interest is the oxidative properties imparted due to its reduction potential. Larger surface to volume ratio and high reactivity than the bulk form shows great progress as antimicrobial agent to control drug resistant microbial population. The distinct surface morphologies, crystalline forms, reaction conditions and synthetic methods exerts significant impact on the photo catalytic and bactericidal efficiency. Hence, the present paper focuses on a concise review of the multifarious study on synthetic methods of Mn 3 O 4 , growth mechanisms, structural forms, phase transformation and phase control, shape and dimensionality. The review also confers its applications towards photo catalytic and bactericidal studies.

Synthesis of Cu-Doped Mn3O4@Mn-Doped CuO Nanostructured Electrode Materials by a Solution Process for High-Performance Electrochemical Pseudocapacitors

“…Figure 1 a shows the schematic of the synthesis of MO, CO, and CMO@MCO (details described in the Experimental Section ). The reaction mechanism for the formation of MO by reacting MnCl 2 with NaOH can be described as follows 43 while the reaction mechanism for the synthesis of CO by reacting CuCl 2 with NaOH can be presented as follows 44 During the synthesis of CMO@MCO, Cu 2+ and Mn 2+/3+ can be doped into MO and CO, respectively, in three different ways: (I) substitution of Mn 2+/3+ by Cu 2+ in MO and the substitution of Cu 2+ by Mn 2+/3+ in CO, (II) bonding with oxygen, and (III) as a secondary phase. 40 Figure 1 b displays the X-ray diffraction (XRD) patterns of as-prepared MO, CO, and CMO@MCO together with the simulated XRD patterns of MO and CO.…”

A Review on Enhancing the Antibacterial Activity of ZnO: Mechanisms and Microscopic Investigation

“…The antibacterial activity of metal oxide nanoparticles (NPs) is dependent on various parameters such as particle size, surface area, crystallinity, capping/stabilizing agent, morphology, concentration/dosage, pH of the solution, and also the nature of the microorganisms. The smaller the nanoparticles (NPs) and its suitable morphology can penetrate easily through the nanosize pores of the bacteria [ 1 , 2 ]. Therefore, it is advisable to optimize the parameters as much as possible for the development of novel nanomaterials for the treatment of disease-causing pathogens.…”

Manganese oxides synthesized via microwave-assisted hydrothermal method: phase evolution and structure refinement

“…When produced by the ionic liquid method, Mn 3 O 4 , as in this work, also has a small MnO 2 impurity, suggesting that the synthesis environment where there is a high concentration of hydroxyls is adequate to stabilize manganese ions and promote the nucleation of Mn 3 O 4 but can result in spurious phases [6,36]. After the precursors dissociation and the sodium chloride and manganese hydroxide precipitation, partial oxidation of Mn (Mn 2+ to Mn 3+ ) occurs, with the interaction with hydroxyls, resulting in formation of Mn 3 O 4 structure.…”

“…It is known that phase transformations in relation to the temperature variation in manganese oxides depends on the used precursors, stoichiometry, particle size and the morphology of the synthesized materials [6]. The transition temperature from the Mn 3 O 4 phase to Mn 5 O 8 metastable phase, for example, has a range of up to 130 ºC (from 350 ºC to 480 ºC), depending mainly on the used precursors and the particle size of the treated material [10,40,41].…”

“…Mn 3 O 4 (hausmannite), for example, has a spinel-like structure with a unit cell consisting of 32 oxygen atoms and 24 manganese atoms, the latter having di-and trivalent cationic states (with Mn 2+ ions forming the tetrahedral clusters and the ions Mn 3+ forming the octahedral clusters) [6], a particular con guration that allows this material to be used in electrochemical processes [7] and in heterogeneous photocatalysis [8]. Based on these applications, several studies report the use of hausmannite with different crystalline systems in order to photodegrade dyes such as Alizarin Yellow, Methylene Blue and Methyl Orange [9][10][11].…”