Tuning Gold Nanorod Synthesis through Prereduction
with Salicylic Acid
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Abstract
Successful
synthesis of gold nanorods requires subtle combination
of additives and reducing species. The latter are of major importance,
as the reducing power determines the rate of metallic gold formation,
which often defines the final shape and anisotropy. Ascorbic acid
is a common reducing agent in the synthesis of gold nanorods, but
its relatively strong reducing power limits the tunability of the
final shape and optical response. We propose here a bimodal reducing
agent system comprising a combination of salicylic acid and ascorbic
acid. While salicylic acid prereduces Au(III) to Au(I) in the growth
solution, ascorbic acid participates in the autocatalytic reduction
of Au(I) to Au(0), selectively occurring on the metallic surface.
This combination provides a fine control over gold reduction at any
stage of nanorod formation, which in turn leads to improved monodispersity,
better reduction yield, and morphology control