Modified Hydrothermal Microwave-Assisted Synthesis of Monoclinic LaPO4:Pr3+ Colloidal Nanorods and their X-ray Excited UV-C Luminescence for Cancer Theranostics

Abstract

A hydrothermal technique with microwave heating (200 °C, 2 hours, 2 magnetrons, 2.45 GHz) was modified to obtain UV-C luminescent LaPO4: Pr3+ colloidal nanorods for the potential use in X-ray cancer theranostics. For further possible biofunctionalization, a compound of tartaric acid formed under basic conditions was used as a coating and stabilizing agent to provide colloidal properties to the surface of nanoparticles in basic to neutral aqueous media, which was confirmed by zeta potential measurements. In addition, the colloidal properties and clustering processes of synthesized LaPO4:Pr3+ nanorods in aqueous solutions with different pH values were studied in real time using a highly sensitive laser ultramicroscope operating according to the “light-sheet” scheme. A comparative analysis of the transmission electron microscopy, X-ray powder diffraction and high-energy spectroscopy showed the different effects of synthesis parameters on the morphological, crystalline and luminescent properties of the obtained nanorods. Through optimization of the synthesis parameters, stable aqueous solutions of m-LaPO4:Pr3+ nanorods with sizes less than 30 nm and an intensity of UV-C luminescence equal to 5-10% of the unmodified nanofibers were obtained.