Cu–Fe–S Nanocrystals Exhibiting Tunable Localized Surface Plasmon Resonance in the Visible to NIR Spectral Ranges

Abstract

Cu-Fe-S nanocrystals exhibiting a strong localized surface plasmon resonance (LSPR) effect were synthesized for the first time. The elaborated reproducible preparation procedure involved copper(II) oleate, iron(III) stearate, and sulfur powder dissolved in oleylamine (OLA) as precursors. The wavelength of the plasmonic resonance maximum could be tuned by changing the Cu/Fe ratio in the resulting nanocrystals, being the most energetic for the 1:1 ratio (486 nm) and undergoing a bathochromic shift to ca. 1200 nm with an increase to 6:1. LSPR could also be observed in nanocrystals prepared from the same metal precursors and sulfur powder dissolved in 1-octadecene (ODE), provided that the sulfur precursor was taken in excess. Detailed analysis of the reaction mixture by chromatographic techniques, supplemented by mass spectrometry and (1)H NMR spectroscopy enabled the identification of the true chemical nature of the sulfur precursor in S/OLA, namely, (C18H35NH3(+))(C18H35NH-S8(-)), a reactive product of the reduction of elemental sulfur by the amine groups of OLA. In the case of the S/ODE precursor, the true precursors are much less reactive primary or secondary thioethers and dialkyl polysulfides.

Copper Iron Sulfide Nanocrystal‐Bulk Silicon Heterojunctions for Broadband Photodetection

“…Most notably, films of these NCs are unique in terms of supporting both photocurrents (PC) as well as a plasmon resonance. [ 14,17–20 ] As CuFeS 2 is a narrow gap semiconductor with a bulk bandgap of 0.52 eV (see the Supporting Information), it is a potential candidate for the fabrication of near‐infrared photodetectors. [ 21 ] Being composed only of light, cheap, earth abundant and environmentally benign elements, it could offer an alternative to conventional Pb based semiconductors.…”

Facile Gram‐Scale Synthesis of the First n‐Type CuFeS2 Nanocrystals for Thermoelectric Applications

“…Very recently we have elaborated two methods of preparing Cu‐Fe‐S nanocrystals, namely heating up and hot‐injection , which enable strict control of their composition, crystal structure, size, and shape.…”

“…The effect of scaling up the synthesis on the size, composition, and structure of the resulting nanocrystals was investigated by electron microscopy, EDS, and X‐ray diffraction. From the EDS spectra (see Figure S1 in the Supporting Information), the inorganic core compositions were determined for the small‐scale batch nanocrystals prepared as described in ref . Fe‐0 and the large‐scale ones, synthesized as described above ( Fe‐1 ), show only minor differences: the determined structure is Cu 1.00 Fe 1.00 S 1.80 (S 2.00 ) for Fe‐0 and Cu 1.00 Fe 1.00 S 1.70 (S 2.00 ) for Fe‐1 (the amount of S 2– required to fully compensate the charge of the metal cations is indicated in parentheses).…”

“…In our previous paper we have demonstrated by complementary NMR spectroscopic and XPS studies that the primary ligands consist of alkyl groups covalently bound to surface sulfur atoms. These rather unusual nanocrystal‐stabilizing groups originate from the transformations of the sulfur precursor in oleylamine.…”

Colloidal Synthesis and Thermoelectric Properties of CuFeSe2 Nanocrystals

“…One potentially attractive, yet not well-studied, copper-based material is CuFeSe 2 , which represents a well-known class of I-III-VI 2 group ternary chalcogenides. Among the I-III-VI 2 group, such as CuInS 2 [22,23,24], CuInSe 2 [24,25,26], CuInTe 2 [27] and CuFeS 2 [24,28,29,30], materials have attracted extensive attention due to their high absorption coefficient, high conversion efficiency, low toxicity and other physical properties and unique chemical properties and have been explored for the fabrication of photovoltaic solar cells in very recent years. However, among these, less attention been paid to the CuFeSe 2 material, as eskebornite with a narrow band gap of 0.16 eV belongs to the tetragonal structure type [31] and the crystal structure of the CuFeSe 2 has the space group P$\stackrel{-}{4}$2c with cell parameters a = 5.521 Å and c = 11.04 Å [32].…”