Polymer-Directed Growth of Plasmonic Aluminum Nanocrystals

Abstract

The challenge of controllable chemical synthesis of aluminum nanocrystals (Al NCs) has been met with only limited success. A major barrier is the absence of effective ligands to control the nucleation and growth of Al NCs.Here we demonstrate the size-and shape-controlled synthesis of monodisperse Al NCs using a polymer ligand, cumyl dithiobenzoate-terminated polystyrene (CDTB-PS). Density functional theory (DFT) calculations indicate that CDTB-PS shows selective absorption on Al{100} facets, inducing the formation of nanocubes and trigonal bipyramids. An excess of CDTB-PS, however, decreases the supersaturation of Al atoms, leading to the formation of {111} facetterminated octahedral and triangular plates. The concentration of the catalyst, titanium (IV) isopropoxide, determines the size of Al NCs by controlling the number of seeds. Depending on nanoparticle size, the solutions of Al NCs possess distinct colors, a characteristic feature of plasmonic nanomaterials. This robust and controlled chemical synthesis of Al NCs lays a foundation for Al as a sustainable plasmonic material for current and future applications.

Wulff-Based Approach to Modeling the Plasmonic Response of Single Crystal, Twinned, and Core–Shell Nanoparticles

“…5 Unlike Ag, Au NPs are stable toward oxidation and biocompatible, enabling biomedical applications. 3 Alternatives to the rather expensive Ag and Au are becoming commonplace, Al being an example that is earth abundant and sustains LSPRs in the visible and ultraviolet (UV) region, providing opportunities for UV plasmonics 6 All three metals have well-established synthetic techniques 7,47,48 leading to a variety of single-crystal and twinned NPs 49 whose shape-dependent plasmonic properties can be predicted or confirmed via numerical simulations. Here, Au and Ag cubes, {100}-capped bipyramids, and decahedra are chosen as examples of single crystal, monotwin and pentatwin noble metal shapes, respectively, while cubes, octahedra, and {100}-capped bipyramids are chosen as representative Al shapes.…”

Prominence of the Instability of a Stabilizing Agent in the Changes in Physical State of a Hybrid Nanomaterial

“…Stabilizing agents (SAs) used for the preparation of nanoparticles in solution are of tremendous importance for the control of their size and shape [1–7] as well as for their colloidal stability [8–11] . Their role on the nanomaterial's properties is also established for magnetic, [8,12] optical, [13–15] thermoelectric, [16] catalytic properties, [17–21] and biocompatibility [22–24] .…”

Exploiting Colloidal Metamaterials for Achieving Unnatural Optical Refractions

“…On one hand, the chemical synthesis can lead us to obtain sub‐100 nm metallic colloids of single‐crystal quality, atomically smooth surface, and high uniformity, which are essential for the high precision and performance of the resonant nano‐optics. [ 64–84 ] More importantly, their shapes can be precisely controlled to spheres or various polyhedrons (i.e., cube, octahedra, and so on). [ 64–84 ]…”

“…These challenges have motivated the use of colloidal self‐assembly as a toolset for the development of optical metamaterials. [ 25–63 ] By benefitting from the recent advances in synthetic strategy, the diversified shapes of metallic and dielectric colloids spanning from 5 to 1 µm in size have come to the fore with sufficiently high yield; [ 64–91 ] at the moment, these subwavelength‐scale nanoparticles can serve as optical meta‐atoms with controlled electric and magnetic responses. [ 37,51–61,67,85,86,88–90,92–94 ] For example, merely by dispersing subwavelength‐scale metallic colloids within the medium, effective electrical parameters such as effective permittivity (ε eff ) and the resultant refractive index ( n eff ) at optical frequencies can be broadly enhanced beyond the naturally available regimes.…”