We developed a simple and rapid method for dimer and higher multimer formation of gold nanoparticles (AuNPs) in bulk suspension. A coupling of AuNPs modified with COOH-terminated alkanethiol by van-der-Waals interaction between alkyl chains was employed. We demonstrated the tunability of the interparticle gap by changing the alkyl chain length from C5 to C15. Efficient dimer formation that avoids unwanted aggregation was demonstrated for AuNPs with a diameter ranging from 20 nm to 80 nm. For all cases, we found that the interparticle gap is well-defined and uniform. For the shortest alkyl chain (C5), we achieved an interparticle gap as small as 1.0 nm.
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