Sample Solution

illuminated from the inside. In 1980, the cup was confirmed to contain nanoparticles of silver and gold, with diameters ranging from 50nm to 100nm. The green colour is due to the diffusion of light from the outside, and the red colour is due to the silver-gold alloy that is present and absorbs at 515nm.13
Although gold nanoparticles are a new branch of medicine, gold itself has been used for medicinal applications as early as 2500BC in Ancient Egypt, and records show gold being used to treat fevers in the 17th Century and later syphilis in the 19th Century
The simplest and most common method of gold nanoparticle synthesis is the Turkevich method, involving the reduction of gold. This reaction is carried out at 100°C, and chloroauric acid is reduced by sodium citrate with constant stirring. It is possible to have variation in the diameters of the gold nanoparticles by varying the concentration of citrate used.17 This method was first proposed in 1951 by Turkevich, and in the 1970s was improved by Frens. Other methods which include the reduction of gold are the Brust-Schriffin method, using sodium borohydride as the reducing agent; the Murphy method, which uses ascorbic acid as the reducing agent; the Perrault method, where hydroquinone is the reducing agent, and the Polyol process, with various diols reducing the gold. Each of these methods will produce “colloidal gold”, i.e. gold nanoparticles in the liquid phase.13
This section will discuss the various methods proposed of synthesising gold nanostructures which are biocompatible and have NIR absorption, ideal for application in cancer diagnosis and therapy. The cost of materials will also be evaluated for each method, as well as the time consumed and ease of preparing the nanostructures.