Mechanism of the layer-by-layer process. Initially positively charged species will adsorb onto the substrate surface. In the next step, negatively charged species will adsorb onto the now positively charged surface. After n repetitions, a multistacked bilayer composite film is built-up. In between each step the substrate is washed to remove any excess of not specifically adsorbed species.
Scheme of the spray deposition setup. The upper section shows which parts of the hardware are controlled by the program. A nested list of commands is given by the operator to instruct the program. The left side of the picture shows the movable sample holder. The sample holder is attached to a stepper motor via a transmission. On the right-hand side there is the nozzle arrangement. In the center is the photoelectric barrier that controls the amount of liquid that is dispersed by the nozzles.
Photograph of the nozzle arrangement and the laser unit. On the left-hand side all nozzles are turned off. On the right, the 2nd nozzle is turned on. The laser light that comes from the far end is partially scattered by the spray mist (indicated by the dark circle). The resulting change of intensity is detected by the phototransistor in the foreground.
(a) Evolution of the UV-Vis absorption of the samples with different numbers of bilayers. (b) AFM image of a 30 bilayer LbL film that displays a scratch to reveal the thickness of the film. (c) Amount of liquid dispersed by the nozzles as a function of the spraying time (controlled with the laser unit).
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