The invention relates to a squarylium type
chemical sensor for colorimetric identification of a
copper ion and a preparation method thereof, belonging to the field of chemical analysis and testing. The squarylium type
chemical sensor is provided with a symmetric 2, 3, 3-trimethyl-indole squarylium compound and is prepared by the following steps of: mixing a 2, 3, 3-trimethyl-indole ring compound and
squaric acid with a
molar ratio of 2:1, adding mixture into a three-necked flask, adding mixed
solvent of
toluene and n-
butanol with a volume ratio of 1:1, performing heating, mixing and back-flowing for 2-24 hours, and separating water produced in reaction with a water separator; stopping heating, cooling to the
room temperature, depressurizing and evaporating to remove part of the
solvent, and filtering to obtain green
solid; and repeatedly washing the obtained green
solid with
ethyl acetate,
drying at 60 DEG C, and recrystallizing with
ethanol solvent to obtain pure green crystals. When the squarylium compound is applied in identification of the
copper ions, the color can change in addition to changes in the absorption spectrum, the characteristics are obvious, and detection of the
copper ions can be facilitated.