indicates that the majority of the gold colloids are of size less than 10 nm (< 10 nm). Overall, the colloid solution appears very stable and the colloids free from aggregation. Transmission Electron Microscopy (TEM) TEM analysis was used to evaluate the size and shape of the gold colloids. A selection of TEM images taken at different magnification is shown below. The size of the gold colloids can be determined by comparison with the scale bar on each image. Most colloids have a diameter of < 10 nm (~ 5 nm); very few particles show to be slightly larger (~ 15 to 20 nm in size). The gold colloids are of spherical or elliptical shape.