Optical absorption spectroscopy and dynamic light scattering have been used to study the aggregation behavior of 1,1-diethy1-2,2-carbocyanine (PIN) and 3,3-dimethy1-9-(2-thieny1)-thiacarbocyanine (L-21) dyes in aqueous solutions containing orthovanadate-based ReEuVO4 (Re = Gd,Y, La) nanoparticles (NPs) of various form-factor. It has been shown that the interaction of cationic dye molecules with the negatively charged surface of NPs leads to the dye aggregation and formation of large dye aggregates/NPs complexes. The coagulation process is found to be governed by the NPs surface area, rather than its form factor. The dye aggregate structure is analyzed within the Kasha and McRae exciton model framework. (C) 2015 Elsevier B.V. All rights reserved.