Effect of chelating agent (1,10-phenanthroline) on potassium hydrogen phthalate crystals

The influence of a new organic additive, chelating agent 1,10-phenanthroline (Phen) (∼5.0·10−3 M L−1) on potassium hydrogen phthalate (KHP) single crystals at 30° is investigated. The crystals were grown from the aqueous solutions of pH ∼4.5 at constant temperature by solvent evaporation technique. The chelating agent leads to an increase in metastable zone width and assists the bulk growth process. The growth rate of crystals in the presence of Phen decreases considerably with an increase in impurity concentration. Not much variation is observed in FTIR and cell parameter values, determined by XRD analysis. It appears that the growth promoting effect (GPE) of Phen is caused by the adsorption of the organic additive on the prism of KHP crystals. Differential scanning calorimetry (DSC) and TG-DTA studies reveal the purity of the sample and no decomposition is observed up to the melting point. Scanning electron microscope (SEM) photographs exhibit the effectiveness of the impurity in changing the surface morphology of KHP crystals. Contrary to expectations, Phen depresses the NLO efficiency of KHP, suggesting that the molecular alignments in the presence of Phen results in cancellation effects disturbing the non-linearity.