Turning Silver into Gold at Least on the Nanoscale



The color of metal colloids is highly dependent on their size and therefore being able to control the size is very important to tune the metal colors systematically. By controlling the wavelength of optical resonance of metal nanoparticles and their composition, researchers in South Korea have found a way to fabricate various colored metal colloids both easily and reproducibly. These findings could be very useful for biological assays.

The deposition of metal nanoparticles on the surface of nanospheres gives rise to significant changes in the optical properties. Compared with originally colorless polymers, metal-coated polymers turn to yellow or red, depending on the components of the deposited metals. This then makes them useful in biological sensing applications such as contrast agents, blood flow cytometry or surface-enhanced Raman scattering.

To control the color of metal colloids, numerous researchers have tried to fabricate different sized and shaped nanoparticles using various metals. They succeeded in synthesizing various colored metal colloids by controlling the size, shapes (spherical, cube, rod, triangle, prism, etc) and geometry (core/shell, hollow, etc) ot the particles. However, they need different chemical reaction conditions to synthesize different colored metal colloids.

One of the disadvantages of current approaches is the fact that it is very difficult to synthesize monodispersed metal colloids on a large scale. The production yields are also very low.

The full article can be found on the Nanowerk website.





Turning Silver into Gold at Least on the Nanoscale