Efficient Control of Atom Arrangement in Ternary Metal Chalcogenide Nanoparticles Using Precursor Oxidation State

Abstract

Controlling both the concentration and the distribution of elements in a given material is often crucial to extracting and optimizing synergistic properties of the various constituents. An interesting class of such multielement materials is metal chalcogenide nanoparticles, which exhibit a wide range of composition-dependent optoelectronic properties including both bandgap-mediated processes and localized surface plasmon resonance properties, each of which is useful in applications ranging from energy conversion to sensing. Because metal chalcogenide nanoparticles can support several different metal elements in a variety of chalcogen lattices, this material class has particularly benefited from the ability to control both atom concentration and atom arrangement to tailor final particle properties. The primary method to access complex, multimetallic chalcogenide particles is via a postsynthetic cation exchange strategy. One-pot syntheses have been less explored to access these complex particles, although this route is desirable for economy and scalability. Here, we compare the composition and morphology outcomes from cation exchange and one-pot preparation approaches using a Cu/Ag/Se system, which is already known to exhibit both binary and ternary metal chalcogenide phases. We show that at similar concentrations of the two metal cations, initial reaction conditions for the one-pot method yield multicomponent nanoparticles, whereas cation exchange yields homogeneous ternary metal chalcogenide structures. We then show that by tuning the precursor oxidation state for the one-pot method, this approach can be used to access homogeneous ternary metal chalcogenide particles that are similar in atom arrangement to the particles obtained using cation exchange. Taken together, our results demonstrate reliable synthetic methods that yield a variety of controlled compositions and composition morphologies in the Cu/Ag/Se system. Importantly, we demonstrate that this entire collection of architectures can all be accessed via a one-pot method simply by modifying metal precursor chemistry. The mechanistic insights gained and the resulting streamlined syntheses outlined indicate pathways to easily scaled, highly tailorable syntheses for rapid translation into downstream technologies.

Connecting Cation Exchange and Metal Deposition Outcomes via Hume–Rothery-Like Design Rules Using Copper Selenide Nanoparticles

“…XPS findings confirm the identity of Ag in these samples to be in a 1+ oxidation state with an average Ag 3d 5/2 binding energy of 367.9 ± 0.2 eV and the absence of any loss features (Figure S8). , Studying the elemental distribution of Ag using STEM-EDS, we find that Ag is not distributed homogeneously throughout the particles (Figures C and S9, i.e., each particle does not exhibit the same extent of CE with Ag + ), indicating that the CE process occurs cooperatively. ,, Cooperativity in CE processes suggest that the guest cations diffuse quickly via the presence of vacancies in the host Cu 2‑x Se lattice.…”

“…Instead, when Ag + concentrations were high relative to Cu concentration in the original NP (10:1 vs 2:1 in this report), 40% Ag 2 Se, 50% CuAgSe, and 10% multicomponent Ag 2 Se/ CuAgSe products are formed exclusively, with no unreacted Cu 2-x Se NPs detected (as well as no accompanying discrete Ag NP or pendant metallic AgNP formation observed), indicating full CE conversion. 55 In other words, the amount of Ag added did not produce a transition from CE to MD products.…”

“…53,54 Studying the elemental distribution of Ag using STEM-EDS, we find that Ag is not distributed homogeneously throughout the particles (Figures 1C and S9, i.e., each particle does not exhibit the same extent of CE with Ag + ), indicating that the CE process occurs cooperatively. 12,55,56 Cooperativity in CE processes suggest that the guest cations diffuse quickly via the presence of vacancies in the host Cu 2-x Se lattice.…”

Manipulating Cation Exchange Reactions in Cu2–xS Nanoparticles via Crystal Structure Transformation

“…In many cases, the resulting NPs preserve the morphology and anion structure of the template. − Furthermore, owing to the large surface-to-volume ratio of the NP with respect to their bulk counterpart, the CE can proceed under relatively gentle reaction conditions. In recent years, the utilization of copper-deficient Cu 2– x E NPs, where E is S, Se, and Te, as a CE template has attracted extensive attention, particularly due to the high Cu + mobility in their NP lattices. − In these CE reactions, it is crucial to use phosphines such as trioctylphosphine (TOP) to abstract Cu + from the template lattice because of the strong affinity of TOP molecules with Cu + . In addition, as a matter of fact, Cu + ions are generally smaller in size than that of chalcogen anions, and therefore, one can imagine that the Cu + ions diffuse in a relatively tough chalcogen anion framework, that is, CE reactions occur instead of anion exchange due to the higher Cu + diffusion rate than the chalcogen anion. , Among these Cu 2– x E NPs, Cu 2– x S is emerging as a superior CE template for the production of metastable, multielemental, core@shell, segmented, and porous metal sulfide nanomaterials by substitution of entirety or a portion of the host Cu + . − …”

Tailoring Morphology and Elemental Distribution of Cu-In Nanocrystals via Galvanic Replacement

“…Colloidal synthesis is a powerful and versatile approach to form bimetallic NCs with tunable sizes, shapes, compositions, and crystal structures. ,,,− The control over several reaction parameters has proven useful to advance the mechanistic knowledge on the factors determining the composition and configuration of multicomponent NCs. ,− As for metals, most studies have been performed on noble metal-containing NCs, for which a vast library of bimetallic structures exists . The oxophilicity of other metals complicates their synthesis and makes working with them more unpredictable .…”