Inhibition of fluorescence of styryl phenanthrimidazole on doping nanocrystalline ZnO with bismuth

• Quenching of fluorescence of phenanthrimidazole by Bi3+-doped ZnO nanoparticles.
• Enhancement of fluorescence of phenanthrimidazole by ZnO nanoparticles.
• Azomethine nitrogen binds with Bi3+ in Bi3+-doped ZnO.
• Azomethine nitrogen binds with Zn2+ in pristine ZnO.

Nanocrystalline ZnO was doped with Bi3+ by sol–gel method. It was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and UV–visible diffuse reflectance (DRS) and photoluminescence (PL) spectra. The dynamics of photoelectron transfer from the phenanthrimidazole to Bi3+-doped ZnO has been investigated by absorption, fluorescence and lifetime spectroscopic techniques. The spectral results indicate association of the phenanthrimidazole with Bi3+-doped ZnO nanoparticles. The free energy change (ΔGet) for the electron transfer has been obtained. The phenanthrimidazole–nanoparticulate Bi3+-doped ZnO distance for the critical energy transfer has been calculated. In contrast to our earlier reports of enhancement of fluorescence of the phenanthrimidazole by nanoparticulate ZnO, doping ZnO with Bi3+ quenches the fluorescence. The present findings afford a method to test the presence of Bi3+ in nanocrystalline ZnO.

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