Application of De-silylation Strategies to the Preparation of Transition Metal Pnictide Nanocrystals:  The Case of FeP

Abstract

Phase-pure FeP nanoparticles have been synthesized by the reaction of iron(III) acetylacetonate with tris(trimethylsilyl)phosphine at temperatures of 240-320 °C using trioctylphosphine oxide as a solvent and dodecylamine (DA), myristic acid (MA), or hexylphosphonic acid (HPA) as additional capping groups (ligands). The DA-capped particles prepared at 260 °C have an average diameter of 4.65 ( 0.74 nm with FeP being the only observed crystalline phase. Elemental analyses indicate a high percentage yield of FeP (85%) and are consistent with 12% TOPO incorporation in the product. The addition of MA has results similar to those of the addition of DA, whereas addition of HPA seems to inhibit crystallite growth, resulting in very small (ca. 1 nm) or amorphous particles that are difficult to isolate. Magnetic susceptibility data on DA-capped FeP suggest that the moments within each particle are coupled antiferromagnetically, at least over a short range; however, there is no evidence of a Ne ´el transition, in contrast to bulk FeP. It is likely that the FeP particles produced by this route are too small (ca. 5 nm) relative to the magnetic cell (2.9 nm) for the onset of long-range helical antiferromagnetic order, even at low temperatures (5 K) and fields (0.010 T).

Chemical Routes for Production of Transition‐Metal Phosphides on the Nanoscale: Implications for Advanced Magnetic and Catalytic Materials

“…[24] We soon found that co-surfactants such as dodecylamine (DA) or myristic acid (MA) are essential to moderate the reactivity, thus resulting in a high yield (85 % based on iron consumption) of soluble colloid. [25] Consistent with our assumptions about redox-neutral reactions, the powder X-ray diffraction (PXRD) pattern revealed that the likely product was nanocrystalline FeP (Figure 1 a). Furthermore, transmission electron microscopy (TEM) indicated that, in contrast to the solvothermal method, discrete spherical nanoparticles (ca.…”

“…From magnetic susceptibility measurements on nanocrystalline FeP and MnP, we find that in both cases the transition to a helimagnetic state is completely shut down in the nanoparticles. [25,26] We attribute this to the fact that the nanoparticle dimension (4±8 nm) is approaching that of the magnetic unit cell for the helimagnetic configuration, thereby destabilizing this state. The consequence is that nanoparticulate FeP appears to be paramagnetic over the entire temperature range studied (300±5 K, Figure 3), whereas nanoparticulate MnP is ferromagnetic at all temperatures less than T c (Figure 4).…”

“…[25,26] As bulk phases, both crystallize in the MnP structure type, [27] and both demonstrate a complex low-temperature magnetic structure (helimagnet) with net antiferromagnetic interactions, and a magnetic unit cell dimension of~28 ä along the helical propagation axis.…”

Phase Directing Ability of an Ionic Liquid Solvent for the Synthesis of HER-Active Ni2P Nanocrystals

“…[12][13][14] Typical methods used to synthesize high-quality colloidal Ni 2 P nanocrystals use traditional organic solvents (e.g., octadecene (ODE), dioctyl ether), expensive and/or reactive phosphide precursors (tri-n-octylphosphine (TOP), white phosphorus (P 4 ), tris(trimethylsilyl)phosphine (P(TMS) 3 ), and tri-n-butylphosphine), high temperatures, and/or multiple-step reactions. 10,[15][16][17] Triphenylphosphine (PPh 3 ) is a low-cost, less-reactive, and more air-stable phosphide precursor (~15% the cost of TOP in price per mole); 18 however, compared to TOP and P(TMS) 3 , nanocrystals synthesized using PPh 3 are typically large (>45 nm), ill-defined, amorphous, and/or not phase pure. [18][19][20] Herein, we report the one-step, heating up synthesis of Ni 2 P nanocrystals using Ni(acac) 2 , PPh 3 , oleylamine (OAm), and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-Tf 2 N) as the IL solvent (Eq.…”

Ternary Cobalt–Iron Phosphide Nanocrystals with Controlled Compositions, Properties, and Morphologies from Nanorods and Nanorice to Split Nanostructures

“…[4][5][6][7][8][9][10][11] Similarly, ternary metal phosphides in bulk such as Fe 2Àx Mn x P, [12] Fe 2Àx Co x P, [13] Co 1Àx Mn x P, [14] and Ni 2Àx Mo x P [15] have been extensively studied as well; in contrast, their corresponding ternary transition-metal phosphide nanostructures (e.g., M 1Àx M' x P or M 2Àx M' x P) have been rarely explored so far. In comparison, ternary transition-metal oxide or chalcogenide nanostructures like Mg x Zn 1Àx O, Zn x Cd 1Àx S, and Zn x Cd 1Àx Se nanocrystals (e.g., dots, rods, or tetrapods) have been recently prepared and have been shown to exhibit tunable properties by changing their compositions and structures.…”