Cation Exchange-Mediated Synthesis of Library of Plasmomagnetic Nanoheterostructures: Transformation of 2-Dimensional-Shaped Fe₇S₈ Nanoplates to Cu–Fe–S-Based Ternary Compound

Abstract

Cation exchange mediated synthesis of nanoheterostructures (NHSs), core–shell structure or segmented nanostructures are gaining high interest in nanoscience research as the process gives a wide window of opportunity to tune and enhance the photophysical properties of semiconductors. Presence of point defects or layered structure of the material accelerates cation exchange process, which is well established for copper chalcogenide system. Here, we are reporting facile synthesis of high-quality Fe7S8 hexagonal nanoplate by colloidal synthesis route and studied the effect of Cu­(I) ion addition by in situ and ex situ condition. The addition and consequent increase of Cu­(I) precursor concentration to presynthetic Fe7S8 nanocrystals (ex situ) leads to successive compositional and morphological transformations as follows: Fe7S8 (hexagonal nanoplate) → Fe7S8@Cu5FeS4 (multigrained heterostructure) → Cu1.97S/Cu5FeS4/Cu1.97S (nanodumbbell) → Cu1.97S/Cu5FeS4 (segmented nanohat) → Cu1.97S (nanodisk). Native Fe vacancies in layered crystalline structure of original Fe7S8 drive intercalation and cation exchange processes to stabilize a particular NHS. Different diffusion rates and channels of incoming Cu and outgoing Fe ions result in linear and bent nanodumbbells. The position of strong localized surface plasmon resonance (LSPR) band in NHSs is shifted from visible region to infrared region of the spectrum due to the variation of hole concentration originating from intrinsic Cu vacancy. The LSPR bands in NHS are further tuned by generating more holes through oxidation of Cu­(I) → Cu­(II) reaction in oxygen atmosphere. Shape anisotropy in NHS gives rise to multiple plasmon modes. Fe7S8 (hexagonal nanoplate) and Cu1.97S/Cu5FeS4/Cu1.97S (nanodumbbell) exhibit features of ferrimagnetism with transition temperature of above 300 and 320 K, respectively. In situ chemical synthesis using same Cu and Fe precursors as that of ex situ process yields CuFeS2 and Cu5FeS4 phases under Cu-deficit and Cu-rich environment. The LSPR resonance bands with high plasmonic sensitivity are also tuned by controlling the hole concentration.

Aqueous Adsorption of Heavy Metals on Metal Sulfide Nanomaterials: Synthesis and Application

“…Since ion exchange leads to hollowing or tunneling of solid precursor wires, rods, and spheres without destroying the morphologies and structures [12], the original stability of MSs may be retained in the cation exchange-generated MSs. In general, the cation exchange preparation of MSs is governed by lattice structure stability [70] and defects in the crystal structure [71,72] of the precursor sulfide.…”

Enhanced Photophysical Properties of Bi2S3/AgBiS2 Nanoheterostructures Synthesized via Ag(I) Cation Exchange-Mediated Transformation of Binary Bi2S3

“…Moreover, CE has been employed as an effective tool for the synthesis of NHSs, and till now, there are several reports on different cations, like Cu + , 23 Cd 2+ , 24 Pb 2+ , 25 Hg 2+ , 26 and Ag + , 27 which have been used for this kind of reaction to occur. Copper cation exchange is widely studied as it is a fruitful way to fabricate copper-based systems; among which, many of these are emerging as an important plasmonic materials, for example, Cu 3 SbSe 3 , 28 Cu 5 FeS 4 , 29 Cu 3 BiS 3 , 30 CuInS 2 , 31 CuInSe 2 , 32 and so forth.…”

“…Moreover, CE has been employed as an effective tool for the synthesis of NHSs, and till now, there are several reports on different cations, like Cu + , Cd 2+ , Pb 2+ , Hg 2+ , and Ag + , which have been used for this kind of reaction to occur. Copper cation exchange is widely studied as it is a fruitful way to fabricate copper-based systems; among which, many of these are emerging as an important plasmonic materials, for example, Cu 3 SbSe 3 , Cu 5 FeS 4 , Cu 3 BiS 3 , CuInS 2 , CuInSe 2 , and so forth. Although there is a huge research activity on the copper-based cation exchange reaction, fewer reports have been found on Ag + cation-exchanged heterostructure formation where Ag + ion plays a key role in cation exchange transformation.…”

Spontaneous Formation of Heterodimer Au–Fe7S8 Nanoplatelets by a Seeded Growth Approach

“…Pyrrhotite (Fe 7 S 8 ) is one of the many stoichiometric forms of iron sulfide and is an attractive candidate for electrocatalytic applications and used as an anode material for lithium–sodium ion batteries. − Despite its potential, this material has not been investigated much. Only a few attempts have been made where Fe 7 S 8 was laminated, doped, and partially and completely cation-exchanged with another material to attain a hybrid heterogeneous structure, but even this study still lacked a systematic synthesis approach. In the last decade, multiple noble metal-iron oxide based hybrid heterodimers and trimers have been reported.…”

“…[18][19][20] Despite its potential, this material has not been investigated much. Only few attempts have been made where Fe7S8 was laminated, 19 doped, 21 partially and completely cation exchanged 22 with another material to attain hybrid heterogeneous structure but even this study still lacked a systematic synthesis approach. Since last decade, multiple noble metal-iron oxide based hybrid heterodimers and trimers have been reported.…”