Effect of pH on the interaction of hypoxanthine and guanine with colloidal ZnS nanoparticles: A spectroscopic approach

Abstract The purpose of the current research was to study the interaction between the DNA nucleobases (hypoxanthine and guanine) and the ZnS nanoparticles (NPs). A good understanding of such interactions could be beneficial to researchers working in the field of bionanotechnology. The ZnS NPs were synthesized by a reported method and characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The interaction between the DNA nucleobases and the ZnS NPs was investigated by using UV–visible, fluorescence and infrared spectroscopy. The experiments were performed at pH 6.0 and 10.0 to investigate the role of the molecular charge on the interaction process. The UV–visible absorption studies revealed that the absorption bands of the DNA nucleobases were red shifted in the presence of the semiconductor NPs. The red shift was observed to be greater at pH 6.0. The steady-state fluorescence studies showed that the nucleobases quenched the fluorescence emission of ZnS. The quenching was found to depend on the pH of the solution. It was observed that hypoxanthine was more efficient in quenching the fluorescence of the ZnS NPs compared to guanine. The infrared spectroscopic measurements indicated that both hypoxanthine and guanine bonded to the semiconductor surface through their nitrogen atoms.