Iron Pyrite Nanocrystal Inks: Solvothermal Synthesis, Digestive Ripening, and Reaction Mechanism

Abstract

Colloidal iron pyrite nanocrystals (or FeS 2 NC inks) are desirable as active materials in lithium ion batteries and photovoltaics and are particularly suitable for large-scale, roll-to-roll deposition or inkjet printing. However, to date, FeS 2 NC inks have only been synthesized using the hot-injection technique, which requires air-free conditions and may not be desirable at an industrial scale. Here, we report the synthesis of monodisperse, colloidal, spherical, and phase-pure FeS 2 NCs of 5.5 ± 0.3 nm in diameter via a scalable solvothermal method using iron diethyldithiocarbamate as the precursor, combined with a postdigestive ripening process. The phase purity and crystallinity are determined using X-ray diffraction, transmission electron microscopy, farinfrared spectroscopy, and Raman spectroscopy techniques. Through this study, a hypothesis has been verified that solvothermal syntheses can also produce FeS 2 NC inks by incorporating three experimental conditions: high solubility of the precursor, efficient mass transport, and sufficient stabilizing ligands. The addition of ligands and stirring decrease the NC size and led to a narrow size distribution. Moreover, using density functional theory calculations, we have identified an acid-mediated decomposition of the precursor as the initial and critical step in the synthesis of FeS 2 from iron diethyldithiocarbamate.

Nanocrystalline Pyrite for Photovoltaic Applications

“…The monodisperse, colloidal, spherical, and phase‐pure FeS 2 NCs with the size of 5.5 ± 0.3 nm in diameter were synthesised using single source precursor iron diethyldithiocarbamate via post digestive ripening process by Yoder et al . They proposed mechanism of two acid‐catalysed steps for decomposition of the ligand that provided quantum mechanically based insight into the reaction for both hydrothermal and solvothermal reactions (Figure ).…”

Digestive Ripening at Nanoscale and Its Application in the Preparation of Monodisperse Nanomaterials

“…Jagirdar 等 [119,120] 利用消化熟化法合成了 Cu 和 Zn 等金属单分散纳米粒子, 然后经过共消化熟化得到了 Cu@ZnO 的核壳结构; Yang 等 [121] 把溶剂热法合成的多 分散 FeS 2 纳米晶(7.4±1.4 nm)经过消化熟化后获得了 FeS 2 纳米晶单分散体系(5.5±0.3 nm); Viswanatha 等 [33] 研究发现, 在油酸和油胺存在下, 经 200 ℃热处理得到 大尺寸的 FeCoS 2 纳米片, 然后再升温到 300 ℃, 可以 转变为 9 nm 的高度单分散的球状纳米晶.…”

Synthesis of iron chalcogenides from single source precursors

“…XRD pattern showed that water and dimethylformamide both produced phase‐pure face‐centered cubic FeS 2 (Fig. ) . Iron sulfide nanosheets were also prepared by pyrolyzing the above mentioned precursors (Figs (a) and (c)) in OLA.…”

“…Non‐toxicity, environmental friendliness, ability to produce electricity and abundance of iron and sulfur help to maintain a clean environment and enhance the importance of iron sulfides . Controlling the ratio of iron and sulfur in iron sulfides is a difficult challenge due to the presence of reducible ferric and oxidizable sulfide ions .…”

“…Also, by using different surfactants and different concentrations, phase and morphology can be changed which in turn effect the mechanical strength, corrosion and luminescent properties . Because of their natural abundance, ease of preparation and cheapness iron chalcogenides are favored over other metal chalcogenides . Iron chalcogenides are also used in photovoltaic cells because they are non‐toxic .…”