Phase-Controlled Colloidal Syntheses of Iron Sulfide Nanocrystals via Sulfur Precursor Reactivity and Direct Pyrite Precipitation

Abstract

In the colloidal synthesis of iron sulfides, a series of dialkyl disulfides, alkyl thiols, and dialkyl disulfides (allyl, benzyl, tert-butyl, and phenyl) were employed as sulfur sources. Their reactivity was found to tune the phase between pyrite (FeS2), greigite (Fe3S4), and pyrrhotite (Fe7S8). DFT was used to show that sulfur-rich phases were favored when the C–S bond strength was low in the organosulfurs, yet temperature dependent studies and other observations indicated the reasons for phase selectivity were more nuanced; the different precursors decomposed through different reaction mechanisms, some involving the oleylamine solvent. The formation of pyrite from diallyl disulfide was carefully studied as it was the only precursor to yield FeS2. Raman spectroscopy indicated that FeS2 forms directly without an FeS intermediate, unlike most synthetic procedures to pyrite. Diallyl disulfide releases persulfide (S–S)2– due to the lower C–S bond strength relative to the S–S bond strength, as well as facile decomposition in the presence of amines through SN2′ mechanisms at elevated temperatures.

General Solution‐Phase Synthesis of Nanoscale Transition Metal Tellurides Using Metal Nanoparticle Reagents

“…While bis (trimethylsilyl)telluride and TOP‐Te as Te sources involve different mechanisms, equilibria, and chemical species, control experiments varying the reaction parameters did not significantly influence the composition of the Pd–Te product, which points to the precursor reactivity as having the most significant effect. This is conceptually analogous to observations of phase formation in the Fe–S system, where sulfur reagents having more labile bonds formed sulfur‐rich phases, such as FeS 2 , while lower reactivity sulfur reagents formed Fe–S phases having less sulfur, such as Fe 3 S 4 or Fe 7 S 8 . Interestingly, attempts to react Pd nanoparticles with bis (trimethylsilyl)sulfide and bis (trimethylsilyl)selenide did not transform them into their derivative Pd chalcogenides.…”

“…isolation of only unreacted Pd nanoparticles) or samples that consisted of mixtures of PdTe 2 and unreacted Pd nanoparticles. However, it is known for sulfide and selenide systems that the reactivity of the chalcogen reagent can influence the composition and morphology of the nanocrystal product that forms , . To better understand the role of precursor reactivity on phase formation, we reacted the Pd nanoparticles with a TOP‐Te complex, formed by dissolving Te powder in trioctylphosphine (TOP), under identical conditions used to react the Pd nanoparticles with bis (trimethylsilyl)telluride.…”

FeS2 Grown Pencil Graphite as an In‐expensive and Non‐enzymatic Sensor for Sensitive Detection of Uric Acid in Non‐invasive Samples

“…In pursuit of a novel functional nanomaterial for the development of electrochemical sensing applications, pyrite iron disulfide (FeS 2 ), a transition metal dichalcogenide has gained substantial considerations because of its profused availability on earth, low‐price, non‐toxicity, narrow band gap (0.95 eV), excellent stability and electro‐catalytic properties . There are several reports on pyrite FeS 2 for energy storage applications while very few studies related to the use of pyrite FeS 2 for electrochemical sensing.…”

Nanocrystalline Pyrite for Photovoltaic Applications

“…There are several factors that play a key role in synthesis of the phase pure pyrite NCs as well as their photoconductivity e. g., precursors (iron source & sulfur source providing units), precursor ratios (Fe:S), reaction temperature, reaction time, precursor concentration, pH of reaction solution, solvents, surfactants and ligands . Recently Rhodes et al . studied the effect of sulfur sources using dialkyl disulfides, alkyl thiols, and dialkyl disulfides (allyl, benzyl, tert ‐butyl, and phenyl) on iron sulfide phases via colloidal route.…”