Synthesis of Azo Dyes and Generation of Dot Matrix Using Thin-Layer Chromatography

Abstract

Thin-layer chromatography, which involves the movement of dyes along a silica-coated plate, is used to observe the progress of chemical reactions and to separate mixtures. We took advantage of this phenomenon to devise a method for generating patterns in the shape of numbers with dots (dot matrix). We prepared the azo dyes necessary for generating the dot matrix and successfully generated dot matrix images of numbers 0 to 9 using three azo dyes synthesized from two types of aromatic amines and three types of phenols. All plates were developed in a hexane:acetone = 5:1 solvent. The advantage of this study is that all azo dyes necessary for drawing can be synthesized from common raw materials. Both the dye synthesis and dot matrix generation can be carried out as part of practical work intended for first-year university students. Alternatively, the experiments could be conducted using the dyes prepared in advance by the instructor, and high school students could be encouraged to consider which dye solution to spot on each lane to draw their desired number by dot matrix.