Purple layer thickness

However, there remains a problem with this arrangement. If too thin a layer of a metal such as gold is deposited, a purple layer of high resistance is formed owing to the deposition of the gold as islands rather than as a continuous film [19] if too thick a layer of gold is deposited, the evanescent... 

Indium oxide doped with tin oxide (indium-tin oxide (ITO)) or fluoride-doped tin oxide (often expressed as SnOaiF) are the two favoured layers of choice for most electrochemists and analysts. The thickness of such oxide layers is typically 0.3-0.6 pm, so the ITO-coated side of the electrode displays a pleasant purple sheen . 

Total internal reflection (TIR) of light within the thin ITO layer removes light of frequencies corresponding to the thickness of the film so, if light of A. = 500 nm is removed, then only red and blue remain, which therefore gives the purple colour. 

On the other hand, the influence of the state of hydration on the photocycle of bacteriorhodopsin is remarkable. In order to study its effect, thin layers of purple membrane were prepared by drying concentrated suspensions of purple membranes in water on a glass sUde at room temperature and atmospheric pressure. Variable hydration of the thin layers was obtained by equilibrating the preparations with various relative humidities produced by saturated salt solutions. The average thickness of the preparation was 1-3 m as determined by scanning electron microscopy. The glass slide containing the preparation was inserted into a cuvette suitable for spectroscopy and equilibrated with the required specific humidity before analysis. 

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