Synthesis of colloidal MnSb nanoparticles: consequences of size and surface characteristics on magnetic properties

Abstract

A solution phase methodology was developed for the formation of discrete colloidal MnSb nanoparticles using dimanganesedecacarbonyl and triphenylantimony as the main reaction components. Stoichiometric reactions result in significant Sb impurities, but these can be eliminated by the use of excess Mn reagent, limiting the reaction time, and using a lower temperature (280 °C) relative to that commonly employed for MnP or MnAs synthesis (330-360 °C). The resultant MnSb nanoparticles are, when evidenced by both powder X-ray diffraction and transmission electron microscopy, ca. 14 nm in diameter and exhibit low polydispersity (13±1.7 nm). High Angle Annular Dark Field-Scanning Transmission Electron Microscopy and energy dispersive line scan data revealed that the as-synthesized MnSb nanoparticles are coreshell in nature, having a MnSb core and an amorphous manganese oxide shell. Evidence is presented supporting a pathway for decomposition of MnSb nanoparticles driven by formation of MnO 2 and Sb due to reaction with adventitious O 2 . The MnSb nanoparticles are superparamagnetic at room temperature, and exhibit suppressed moments attributed to surface oxidation arising from the high surface area and intrinsic oxophilicity of Mn. IntroductionBinary and ternary intermetallic compounds formed by combination of 3d transition metals and pnicogens X (X=P, As, Sb or Bi) are of special interest due to their various electronic and magnetic properties. 1 Among transition metal pnictides, manganese arsenide (MnAs), manganese 15 external magnetic field of 100 Oe. The FC plot shows a gradual increase of molar magnetization with decrease of temperature from 320 K which then saturates at temperatures roughly below 50 K. In the ZFC curve, the sample shows a broad maximum in the range of 245-255 K, near the intersection of the FC with the ZFC curve. Collectively, the above behavior suggests superparamagnetic behavior. Under FC conditions, the magnetic moments of the particles are frozen along the direction of applied magnetic field upon cooling, producing saturation at lowtemperature. In contrast, for ZFC samples, the moments are frozen in random orientation at low temperature, and start to align in the field upon heating, reaching a maximum at the blocking temperature,T B , above which superparamagnetic behavior is exhibited, resulting in a drop in magnetization again. The T B depends on the volume of the nanoparticle, the presence of anisotropy (shape or magnetocrystalline), as well as the time-scale of the measurement (~10 -9 s for DC magnetometry). In the present case the peak corresponding to T B is relatively broad suggesting a distribution of values reflecting the polydispersity of the sample. 38 We attribute the irregularity in both FC and ZFC plots around 43 K to a small leak of oxygen into the sample chamber that makes a condensed film of oxygen, resulting a para-antiferromagnetic transition of oxygen around 43 K. 39

Boosting the Catalytic Performance of Iron Phosphide Nanorods for the Oxygen Evolution Reaction by Incorporation of Manganese

“…As we ascertained above, the majority of manganese monomers remain in solution and the quantity that is incorporated into the rods can be increased as a function of time. However, because of the highly oxophilic nature of manganese, some manganese monomers may react with adventitious oxygen in the system to form oxide, which cannot be converted to phosphide . Thus, saturation is attributed to competition between manganese incorporation and manganese oxidation, with the latter serving to remove monomers from the reaction.…”

Structural characterization and magnetic response of poly(p-xylylene)–MnSb and MnSb films deposited at cryogenic temperature

“…One of the key problems in synthesis of MnSb thin films 40 , 54 and nanoparticles 51 , 52 is partial segregation of Sb. Given the powder-like intensity profile of MnSb phase in our samples, one can assume that potentially segregated Sb crystallites should also yield peaks with relative intensities close to those of the powder reference, suggesting the absence of preferred crystal orientation.…”

One-Pot Size-Controlled Synthesis of Tin- and Antimony-Based Intermetallic Nanoparticles

“…57,91,92 In this work, the Mn/Sb precursor ratio was fixed at 2:1 in all reactions forming MnSb, due to an excess of Mn reagent being essential in forming MnSb without Sb impurities persisting in the final product, in agreement with the work of Brock and coworkers. 88,90 Despite this, only the largest nanoparticles in this work contain observable interstitial Mn, suggesting a critical particle size below which the stoichiometric phase is favored.…”