Nano Gold

Gold nanoparticles (AuNps) are minute sized particle of gold with reduced dimentionality down to nanometers. Nano is a prefix which stands for 1/1 000 000 000 of a meter. They have synthesized for a long time, dating back to medieval times where different sized AuNps are exploited to stained glass windows in churches. Gold nanomaterials larger than 2nm possess metallic characteristics and only behave like a semi-conductor once the nanomaterials are reduced below 2 nm. The semi-conducting AuNps have been reported to induce fluorescence signal due to its valence bands. AuNps are most chemically inert out of the noble metals, stable and robust hence it is by far the preferred nanomaterials for wide range of applications, biomedical field especially for bioimaging and cancer therapies.
AuNps come in various sizes and shapes such as spheres, rods and cubes and their electric, optical and magnetic properties of AuNps differ from bulk gold. Furthermore, these properties are tunable by varying the sizes, shapes and structures of the AuNps via different nanofabrication routes published by an ever-increasing list of literatures. These include hexagonal plates, tetrahedral, octahedral, cubes and rods. These form the building blocks for much complicated morphology such as irregular, branched and multipods which are two to three dimensional clusters superlattices. However, all protocols are very unique with diverse conditions and there are no one method which is particularly reproducible or been rationalized. The electric , optical, transport and magnetic properties of these structures vary with the interaction and the coupling among the AuNps self-assembly. For instance, a thin film self-assembly involve self-organissation into monolayers whereas superlattice preparation require encapsulation of the AuNps by organic coating. The encapsulating agents function as interparticle molecular bonds in order to avoid coalescence. This is a variable which is adjustable to fine tune the...