Control of Electron Beam-Induced Au Nanocrystal Growth Kinetics through Solution Chemistry

Abstract

Measurements of solution-phase crystal growth provide mechanistic information that is helpful in designing and synthesizing nanostructures. Here, we examine the model system of individual Au nanocrystal formation within a defined liquid geometry during electron beam irradiation of gold chloride solution, where radiolytically formed hydrated electrons reduce Au ions to solid Au. By selecting conditions that favor the growth of well-faceted Au nanoprisms, we measure growth rates of individual crystals. The volume of each crystal increases linearly with irradiation time at a rate unaffected by its shape or proximity to neighboring crystals, implying a growth process that is controlled by the arrival of atoms from solution. Furthermore, growth requires a threshold dose rate, suggesting competition between reduction and oxidation processes in the solution. Above this threshold, the growth rate follows a power law with dose rate. To explain the observed dose rate dependence, we demonstrate that a reaction-diffusion model is required that explicitly accounts for the species H(+) and Cl(-). The model highlights the necessity of considering all species present when interpreting kinetic data obtained from beam-induced processes, and suggest conditions under which growth rates can be controlled with higher precision.

Electrochemical electron beam lithography: Write, read, and erase metallic nanocrystals on demand

“…Calculations that account for the formation rate of each product, its destruction due to reactions with other species, and its diffusion out of the irradiated area show that within milliseconds, for typical TEM liquid cell conditions, each radiolysis product reaches a steady-state concentration, which depends on dose rate and position ( 24 , 25 ). Some radiolysis products can diffuse far from the irradiated area, but ${\mathit{e}}_{\mathrm{h}}^{-}$, in particular, is so reactive that its concentration is high only where it is generated within the irradiated area and for a few nanometers outside ( 23 – 25 ). …”

“…Nanocrystals may nucleate in the bulk of the solution or on the interior surfaces of the windows ( 27 , 28 ). Depending on the conditions, nanocrystal growth rates may be determined either by the electron dose rate (production rate of ${\mathit{e}}_{\mathrm{h}}^{-}$) or by the rate of supply of the metal ions from the unirradiated bulk solution ( 22 , 23 , 25 ). In the present experiments, where growth occurs only when ions are released from the electrode, the growth rate is clearly limited by the arrival of metal ions at the irradiated area, where they react with ${\mathit{e}}_{\mathrm{h}}^{-}$ created by the beam.…”

Single-Crystalline Gold Nanowires Synthesized from Light-Driven Oriented Attachment and Plasmon-Mediated Self-Assembly of Gold Nanorods or Nanoparticles

“…As a result, the natural OA processes always take a long time for nanoclusters to aggregate, align and form a large-sized crystal. Because of that, a few of methods using extreme conditions (high pressure14, higher temperature15), different types of irradiation energy (light16171819, two-photon20, electron beam21, X ray22) or surface tension (capillary force)2324 have been proposed to enhance the OA process of NPs for forming a micron-sized crystal. On the other hand, the interplay of chemical and physical properties of the surface modification and medication (e.g.…”

Using Scanning Transmission X-ray Microscopy to Reveal the Origin of Lithium Compositional Spatiodynamics in Battery Materials

“…These fundamental relationships are critical to the development of next generation batteries. The initial liquid-electrochemistry microscopy studies were all conducted in the TEM [1][2][3][4][5]. Starting with work on open-cell systems using ionic liquids [1], which expanded work on in-situ TEM of solid-electrolyte materials, moving to closed-cell liquid TEM studies with battery electrode/electrolyte systems that are directly used in the current generation batteries.…”