Synthesis and Thermoelectric Properties of Noble Metal Ternary Chalcogenide Systems of Ag–Au–Se in the Forms of Alloyed Nanoparticles and Colloidal Nanoheterostructures

Abstract

ABSTRACT:The optimization of a material functionality requires both the rational design and precise engineering of its structural and chemical parameters. In this work, we show how colloidal chemistry is an excellent synthetic choice for the synthesis of novel ternary nanostructured chalcogenides, containing exclusively noble metals, with tailored morphology and composition and with potential application in the energy conversion field. Specifically, the Ag-Au-Se system has been explored from a synthetic point of view, leading to a set of Ag 2 Se-based hybrid and ternary nanoparticles, including the room temperature synthesis of the rare ternary Ag 3 AuSe 2 fischesserite phase. An in-depth structural and chemical characterization of all nanomaterials has been performed, which proofed especially useful for unravelling the reaction mechanism behind the formation of the ternary phase in solution. The work is complemented with the thermal and electric characterization of a ternary Ag-Au-Se nanocomposite with promising results: we found that the use of the ternary nanocomposite represents a clear improvement in terms of thermoelectric energy conversion as compared to a binary Ag-Se nanocomposite analogue.

Colloidal and Deposited Products of the Interaction of Tetrachloroauric Acid with Hydrogen Selenide and Hydrogen Sulfide in Aqueous Solutions

“…Mixed silver-gold sulfides and selenides, including nanoparticulate ones, have attracted intense interest as minerals and natural sources of precious metals [1][2][3][4][5][6][7][8][9][10][11][12][13][14] and due to high ionic conductivity, tunable optical characteristics, thermoelectric and other properties promising for materials applications [15][16][17][18][19]. Gold chalcogenides, in particular gold selenide, are much less examined, despite aqueous Au chalcogenide-derived complexes play the crucial role as carriers of gold in hydrothermal fluids and brines (e.g., [20][21][22][23][24][25] and references therein), and AuSe, Au(Se,S) and Au(Te,Se,S) phases in intergrowths with native gold have been found in the high-sulfidation epithermal deposits formed from acidic fluids [14].…”

“…It is known from chemistry textbooks (for example [38]) that direct interaction between aqueous gold complexes and selenide ions results in precipitation of unstable gold selenides with unclear compositions. Preparation of nanoscale materials containing gold selenide have been described in a few publications [17,[39][40][41][42][43][44][45]. Nath and co-workers [39] have synthesized "AuSe nanoalloys" via fusion of elemental Au and Se nanoparticles in a micellar solution, typically with an excess of Au NPs.…”

Modulated Triple‐Material Nano‐Heterostructures: Where Gold Influenced the Chemical Activity of Silver in Nanocrystals

“…Elemental analysis (Figure S3, Supporting Information) also supports their alloyed‐type composition of these nanostructures. Partial sulfurization of Ag(0) particles turning to Ag‐Ag 2 S alloyed material heterostructures is widely known . Figure c,d shows the TEM and HRTEM images of these Au‐treated bimetallic and binary alloyed semiconductor heterostructures.…”

Gradual Transformation of Ag2S to Au2S Nanoparticles by Sequential Cation Exchange Reactions: Binary, Ternary, and Hybrid Compositions

“…In the Se analogue we observed that the Se(-II) was working as a sacrificial anion to reduce Au(III) to Au(I), and indeed an amorphous Se layer was observed surrounding ternary NPs. 22 In fact, HRTEM micrographs also point to the formation of a thin amorphous shell after the cation exchange reaction (Figures 3 and 5). Although in principle, S(-II) should be less reducing than Se(-II), experimentally the nucleation of Au(0) is observed in all samples prepared with S and could not be avoided, contrary to what happens with Se.…”