Herein, we demonstrate the formation of solid nano-octahedra as well as the clustering of MnO NPs into octahedra using different surfactants, precursor-to-surfactant ratios, and reaction rates. Furthermore, these octahedral nanostructures have a range of applications for example, those of Co 3O 4 and SnO 2 are employed in gas sensing (21) SnO 2 in high-performance Li-ion batteries (22) and MnO octahedra in cataluminescence sensing, (23) supercapacitors, (24) and photodecomposition.

(10) On the other hand, reductive decomposition of noncarbonyl organometallic complexes, such as or [Fe surface atoms and highly energetic edges and corners. In fact, these metal NPs are more prone to oxidation when prepared from the thermal decomposition of precursors with oxygen-containing anions, such as acetates, acetyl acetonates, carbonyls, and so on. (9) The 3d transition metal NPs of Co, Fe, and Ni are the most affected ones, whose ferromagnetic (FM) moments decrease after exposure to air. (7, 8) This surface oxidation, however, compromises the material properties. The uncontrolled inward diffusion of oxygen atoms results in biphasic coreвЂ“shell NPs with the intact core, shelled by the oxide phase of a metal with a higher oxidation state.

(6) Because of the high fraction of surface atoms, their nanoparticles (NPs) are especially prone to surface oxidation in ambient atmosphere. Transition metals and their oxides with different shapes and sizes have been a subject of intense interest among researchers owing to their enormous size and morphology-dependent potential applications in sensors, (1) magnetic resonance imaging, (2) catalysis, (3-5) and high-performance permanent magnets. Thicker the Mn 3O 4 shell, higher is the exchange-biased hysteresis loop shift. The surface oxidation of MnO nano-octahedra was probed by Rietveld analysis of X-ray diffraction patterns and X-ray photoelectron spectroscopy and characterized by magnetic measurements, as the presence of ferrimagnetic Mn 3O 4 shell on the antiferromagnetic MnO core provides an exchange coupling at the coreвЂ“shell interface. The nanostructures were prepared by varying the surfactants, surfactant-to-precursor molar ratio, accelerating agent, and reaction heating rate. For example, the Mn 3O 4 surface layer is 0.4 nm thinner with trioctylphosphine oxide than with trioctylamine as the surfactant.

In addition to morphology control, which restricts the thickness of the Mn 3O 4 surface layer, the binding chemistry of the surfactants plays an essential role. In this study, solid octahedral shapes of MnO limit the inward oxygen diffusion compared to that of the MnO-nanoparticle-assembled octahedra. To overcome this limitation, novel synthesis methodologies are required. Under conditions of counter-diffusion of ZnNTP and Fe 2+ ions, the heteropolynuclear complex Zn 1/2 Fe 1/2 (H 2 O) 3 Вµ-H 4 NTP]n is formed.The intrinsic physical properties of nanostructures of metals and their oxides are altered when they are prone to surface oxidation in ambient atmosphere. At the initial stage of its formation, the passive film is composed of iron oxides, which may further approach the structure of magnetite. The lowest anodic dissolution current is reached at the ZnNTP concentration of about 0.6 g/L. The effect of the inhibitor Na 4 в™±3H 2 O with a certain molecular structure have been studied, including the mechanism of its action. The formation and structure of passive films on steel in a borate buffer environment pH=7.4 containing Chloride ions have been thoroughly investigated.

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