Star-Fruit-Shaped Gold Nanoparticles

Researchers continually seek to craft nanoparticles with complex, exotic structures to produce unique properties. Now a duo of chemists has made gold nanoparticles that look like star fruit (Langmuir, DOI: 10.1021/la300218z). Eugene R. Zubarev and Leonid Vigderman of Rice University thought that combining star shapes and rod shapes into one particle could lead to ideal materials for chemical detection techniques such as surface-enhanced Raman spectroscopy (SERS). In principle, electromagnetic fields should concentrate at the tips of the star fruit spikes and amplify the characteristic Raman signals of sample molecules adsorbed on the particle’s surface, Zubarev says. To make the gold star fruits, the researchers first made gold nanorods with a pentagonal cross section. Next they stirred the rods into a solution of gold chloride, silver nitrate, and cetyltrimethylammonium bromide to deposit more gold on the particles. A few hours later, they filtered the particles and observed their star fruit shape by using scanning electron microscopy. The researchers then ran SERS experiments and found Raman signals from a test molecule with star fruit particles were 25 times as much as those from molecules with flat pentagonal nanorods.