The association parameters of both bulk and nano-CuSO₄ salts in (EtOH-H₂O) mixed solvents were estimated at room temperature (293.15K) using conductivity method by applying Fuoss-Shedlovsky calculation. The association parameters of nano-CuSO4 was greater than bulk CuSO₄ salt. The interaction between the cation (Cu²+) with ligand (ciprofloxacin, CFL) in (EtOH-H₂O) mixed solvents at room temperature (293.15K) was determined by the conduct metric method. The formation Gibbs free energies change (∆Gf) and transfer Gibbs free energies change (∆Gt) were increased in negative signs with increasing in EtOH content in the binary solvent. Two stoichiometric complexes 1:2 and 1:1 (M:L) are formed and the formation constant and Gibbs free energy of the formed complexes follow the order: Kf (1:1) > Kf (1:2) and ∆Gf (1:1) > ∆Gf (1:2) for (M:L) ( in negative values), which indicate more favorable formation of (1:1) complex compared with (1:2) complex. Also there are a decrease in values of Kf and ∆Gf in case of using nano-CuSO4 than that of using bulk-CuSO₄ but in small difference due to the more solvation effect in case of using nanoparticles
