The cobalt hexacyanoferrate-decorated titania nanotube (CoHCF@TNT) was prepared by dispersing 100 mg of titania nanotube (TNT) to a solution of an equimolar concentration of CoCl2 • 6H2O and K3 [Fe (CN)6] containing 0.05M KCl solution (35mL). The TNT was synthesized by hydrothermal method using Degussa P-25 TiO2 in 2M NaOH as reported in the literature. As far as is known, the pigment Prussian blue was synthesised for the first time in Berlin in the early 1700s. It is commonly assumed that the pigment was not used in paintings before the 1720s. The presence or absence of this pigment is often used to answer questions concerning the dating and authenticity of art objects from the 18th Century. For the very first time, a large collection of French 18th Century paintings by Antoine Watteau (1684-1721) and his circle has been studied in detail. The pigments of more than fifty paintings from the collection of Frederick II of Prussia have been analysed with non-destructive methods using a complementary combination of micro X-ray florescence analysis, optical microscopy and spectroscopy in reflection mode.