Preparation of clusters having various interparticle distances based on imidazolium-modified gold nanoparticles via anion exchange

We describe here the preparation of the clusters having various interparticle distances based on the gold nanoparticles modified with imidazolium salts. Three kinds of the imidazolium compounds, which had different hydrophobic substituents and were synthesized and tethered to the surface of gold nanoparticles. By adding the series of anion species for counter anion exchange, the clusters having diverse interparticle distances were obtained. The precipitations were hardly detected through the anion exchange. The significant changes in the light absorption bands originated from the surface plasmon were observed. In addition, it was found that the decreases of the averages of the interparticle distances evaluated in the TEM images were corresponded to the red-shifts of the peaks in the light absorption spectra. We can show the robust technology to maintain the clusters composed of the nanoparticles with highly regulated interparticle distances at the nanometer scale.