Gold Ruby Glass

Gold ruby glass (also known as cranberry glass) obtians its stunning red color from its structure at the nanoscale level.  "Nanoscale" refers to the size scale range typically between 1-100 nanometers.  A nanometer is very small (the prefix "nano" comes from the Greek word for dwarf) - it takes a billion nanometers to make a meter.  For centuries, people have added gold compounds to glass, producing nanoscale gold metal particles - nanoparticles.  These gold particles have the ability to absorb greenish light in a phenomenon called plasmon resonance.  When white light, comprised of all colors, has greenish colors removed by the gold nanoparticles, the resulting light reaching the eyes appears red. 

The photo was taken of a gold ruby glass collection at Bradley University (http://www.bradley.edu/about/publications/hilltopics/2012spring/lydia/). 
Visible light spectroscopy was done on one of the plates (see: http://www.bradley.edu/inthespotlight/story/?id=96b71938-ee8a-4615-a06d-d04080208b2b).  The spectrum is shown below:

A method for using gold compounds to produce gold nanoparticles in transparent silicone and give that spectacular gold ruby color can be found in D. J. Campbell, R. B. Villarreal, T. J. Fitzjarrald, “Take-Home Nanochemistry: Fabrication of a Gold- or Silver-Containing Window Cling” J. Chem. Educ., http://dx.doi.org/10.1021/ed200466k.