Segmented metal−metal heterostructure nanorods/nanowires are very promising for development in photoelectric devices, wearable electronics, biomedicine, and energy storage due to unique surface and interface and adjustable electronic and optical properties. Regretfully, most of the segmented heterojunctions are presently synthesized in organic solvent, and its electronic dynamics is still rarely studied and poorly understood. Here, we reported a pressure-assisted one-step aqueous-phase strategy to successfully synthesize segmented Ag−Au−Ag heterojunction nanorods (HJNRs), the aspect ratios and heterojunction contents of which can be well controlled by varying pressure value. The heterojunction-induced femtosecond-to-nanosecond dynamics in 1D direction of the Ag−Au− Ag HJNRs were for the first time acquired and presented a unique regularity tendency (e.g., electron−phonon scattering time). The unprecedented aqueous-phase strategy opens up horizons of synthesis of other segmented metal−metal HJNRs, and the fascinating Ag−Au−Ag HJNRs are hopeful for the development of a new class devices in photothermal and photoelectronic fields.
Although the growth mechanisms (e.g., seed-induced
growth and capping agent orientation) of bimetal nanocrystals (e.g., core–shell, alloy, segmented, and branched)
from artificial experimental speculation and theoretical calculation
have been widely accepted, precisely revealing their growth mechanisms
is still tremendously challenging. In this work, we utilized redox
reaction kinetics for the first time to successfully reveal the aqueous
sequential growth mechanism between Au and Ag nanocrystals of segmented
Ag-Au-Ag heterojunction nanorods (HJNRs) in a one-step and high-temperature
aqueous system. Herein, electrode potentials of different electrical
pairs (e.g., Ag+/Ag and AuCl4
–/Au) at 200 °C could be calculated through
using the Helgeson–Kirkham–Flowers state and other equations,
from which whether Au and Ag nanocrystals grew successively and formed
segmented Ag-Au-Ag HJNRs could be correctly assessed. The redox reaction
kinetics mechanism can also explain well the aqueous-phase growth
mechanisms of other bimetal nanocrystals and paves a promising avenue
for the design and synthesis of other one-dimensional segmented metal
nanostructures.
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