Seed-Mediated Growth of Silver Nanocubes in Aqueous Solution with Tunable Size and Their Conversion to Au Nanocages with Efficient Photothermal Property.

Abstract

Two seed-mediated approaches for the growth of silver nanocubes in aqueous solution have been developed. Addition of a silver-seed solution to a mixture of cetyltrimethylammonium chloride (CTAC), silver trifluoroacetate, and ascorbic acid and heating the solution at 60 °C for 1.5 h produces uniform Ag nanocubes with tunable sizes from 23 to 60 nm by simply adjusting the volume of silver-seed solution introduced. Alternatively, the silver-seed solution can be injected into a mixture of cetyltrimethylammonium bromide (CTAB), silver nitrate, copper sulfate, and ascorbic acid and heated to 80 °C for 2 h to generate 46 nm silver nanocubes. Plate-like Ag nanocrystals exposing {111} surfaces can be synthesized by reducing Ag(NH3 )2 (+) with ascorbic acid in a CTAC solution. Relatively large Ag nanocubes were converted to cuboctahedral Au/Ag and Au nanocages and nanoframes with empty {111} faces through a galvanic replacement reaction. The nanocages showed a progressive plasmonic band red-shift with increasing Au content. The nanocages exhibited high and stable photothermal efficiency with solution temperatures quickly reaching beyond 100 °C when irradiated with an 808 nm laser for large heat and water vapor generation.