Colloidal metals, otherwise known as metallic nanoparticles, have many applications in optoelectronics, semiconductors, catalysis, and magnetic devices, while colloidal gold specifically has applications in drug delivery and health care due to its generally non-toxic characteristics. The functionality of a nanoparticle depends on the material in use as well as the size and surrounding environment.
Sodium citrate can be used as a capping agent to produce gold nanoparticles with an average diameter less than 20 nm. The sodium citrate reduces the gold ions in solution to nanoparticles composed of gold atoms. Polyoxometalates, such as the Keggin species phosphotungstic acid (PTA, α-H3PW12O40), are desirable capping agents due to their ability to selectively reduce metallic ions in solution while remaining bound to the reduced core nanoparticle. Keggin ions have high thermal stability and are able to perform such reductions while remaining bound to the core-nanoparticle because they are capable of undergoing electron transfer without changing structurally. PTA is a favorable capping agent because it remains fully disassociated at low pH. Past studies suggest that PTA is advantageous in the synthesis of gold nanoparticles. Anatase titania (TiO2) has potential applications in the degradation of environmental pollutants. Other work showed that PTA bound to titania allows adequate control over the reduction of gold ions to nanoparticles via photoirradiation due to the high thermal stability of PTA.
This presentation explores multiple procedures in which to synthesize colloidal gold nanoparticles of different sizes. Sodium citrate, PTA, and titantia-functionalized PTA are used as capping agents to reduce gold ions in solution. Methods of analysis include observation of color changes and dispersion, ultraviolet-visible spectrophotometry, and infrared spectroscopy.
Jordan Kemme, ’13
Majors: Biochemistry and Molecular Biology, Psychology
Sponsor: Craig Teague