Determination of The Ratio of Cationic Flexible Nanoparticles Binding Constant of Counterions X~- and Br~- (K_X/K_(Br)) using The Semi-Empirical Spectrophotometric (SESp) Technique

摘要

The determination of the ion exchange constant ((K_X)~(Br)) for ion-exchange process occurring between counterions X~- and Br~- (X= (C_6H_5CO_2)~-) at the cationic flexible nanoparticles surface using the semi-emperical spectrophotometric (SESp) technique is described in this paper. The method uses an anionic spectrophotometric probe molecule, N-(2-methoxyphnyl) phthalamate ion (1~-), which measures the effects of varying concentrations of nanoparticles (CTABr/NaX/H_2O) on absorbance, (A_(ob)) at 310 nm of samples containing constant concentration of (1~-), NaOH, CTABr and NaX. The observed data, A_(ob) vs [NaX] fit satisfactorily to an empirical equation which gives the values of two empirical constants. These empirical constants lead to the determination of (K_X)~(Br) (=K_X/K_(Br) with K_X and K_(Br) representing cationic flexible nanoparticles binding constants of counterions X~- and Br~-, respectively). This method gives values of (K_X)~(Br) for moderately hydrophobic X~-. The value of (K_X)~(Br), obtained by using this method, is comparable with the corresponding values of (K_X)~(Br), obtained by the use of semi-emperical kinetic (SEK) method.