Fluorescence properties of methylene blue molecules coupled with metal oxide nanoparticles

Abstract

This work deals with the fluorescence properties of the methylene blue (MB) fluorophores loaded on metal oxide nanoparticles, such as TiO 2 , ZnO, and Al 2 O 3 based on laser-induced fluorescence (LIF) spectroscopy. At first, MB is provoked by diode laser at 665 nm, then the fluorescence emissions are recorded using a Czerny-Turner spectrometer. The lucid red shift appears during the right angle LIF measurements of (MB + TiO 2 NPs) suspensions, where NP are well distributed among the fluorophores. Despite that, the LIF of (MB + TiO 2 ) demonstrates notable red shift in terms of NP concentrations; however, (MB + ZnO) and (MB + Al 2 O 3 ) exhibit a negligible one. The larger red shift occurs for the NPs with greater refractive indices due to the optical elongation. Furthermore, the quenching coefficients K TiO 2 , K ZnO , and K Al 2 O 3 are measured according to the linear Stern-Volmer formalism. The quenching effect in a (TiO 2 +MB) attests to be much stronger than that of other nanoparticles of interest. The discrepancy in the fluorescence emissions of MB at the attendance of different metal oxide NPs is very significant during simultaneous imaging/diagnosis and treatment of tumors.