Gold nanoparticles have good stability, small size effect, surface effect, an optical effect and unique biological affinity, in many areas show a potential application, aroused great interest in science and technology workers, scientists have synthesized a silver (Ag) nanocluster that is virtually identical to a gold (Au) nanocluster. On the outside, the silver nanocluster has a golden yellow color, and on the inside, its chemical structure and properties also closely mimic those of its gold counterpart. The work shows that it may be possible to create silver nanoparticles that look and behave like gold despite underlying differences between the two elements, and could lead to creating similar analogues between other pairs of elements.
The researchers, led by Osman Bakr, Associate Professor of Materials Science and Engineering at King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, have published the paper in a recent issue of the Journal of the American Chemical Society.
“In some aspects, this is very similar to alchemy, but we call it ‘nano-alchemy,'” Bakr told Phys.org. “When we first encountered the optical spectrum of the silver nanocluster, we thought that we may have inadvertently switched the chemical reagents for silver with gold, and ended up with gold nanoparticles instead. But repeated synthesis and measurements proved that the clusters were indeed silver and yet show properties akin to gold. It was really surprising to us as scientists to find not only similarities in the color and optical properties, but also the X-ray structure.”
Like all chemical elements, silver and gold are defined by their number of protons: silver has 47, and gold has 79. The work here doesn’t change the number of protons in an atom of silver; otherwise it would no longer be considered silver. Instead, the researchers synthesized a nanocluster of 25 silver atoms, along with 18 other molecules called “ligands” that surround the silver atoms. The entire negatively charged, silver-based complex ion has the chemical formula [Ag25(SPhMe2)18]-.
Although a few other silver nanoparticle have been synthesized in recent years, this is the first silver nanocluster that has a matching analogue in gold: [Au25(SPhMe2)18]- has previously been reported. Besides both nanoclusters having 25 metal atoms and 18 ligands, they also both have all of their atoms and electrons arranged in almost exactly the same way.
In their study, the researchers performed tests demonstrating that the silver and gold nanoclusters have very similar optical properties. Typically, silver nanoclusters are brown or red in color, but this one looks just like gold because it emits light at almost the same wavelength (around 675 nm) as gold. The golden color can be explained by the fact that both nanoclusters have virtually identical crystal structures.
Related reading: Silver Nanoparticles Antimicrobial antibacterial coating nano silver