The Influence of Medium on Fluorescence Quenching of Colloidal Solutions of the Nd3+: LaF3 Nanoparticles Prepared with HTMW Treatment

Abstract

An original method was proposed to reduce the quenching of the NIR fluorescence of colloidal solutions of 0.1 at. % Nd3+: LaF3 nanoparticles (NPs) synthesized by aqueous co-precipitation method followed by hydrothermal microwave treatment. For this, an aqueous colloidal solution of NPs was precipitated by centrifugation and dissolved in the same volume of DMSO. The kinetics of static fluorescence quenching of Nd3+ donors of doped NPs dispersed in two solvents was analyzed to determine and to compare the concentrations of OH- quenching acceptors uniformly distributed throughout the volume of the NPs. The dependences of the relative fluorescence quantum yield φ of colloidal solutions on the concentration of OH- groups in the NPs were calculated and were also used to determine concentration of acceptors in the volume of NPs in different solvents. It was found that the concentration of OH- groups in NPs dispersed in DMSO is almost two times lower than in NPs dispersed in water. This gives an almost two-fold increase in the relative fluorescence quantum yield φ for the former. The sizes of synthesized NPs were monitored by common TEM and by applying a rapid procedure based on optical visualization of the trajectories of the Brownian motion of NPs in solution using a laser ultramicroscope. The use of two different methods made it possible to obtain more detailed information about the studied NPs.

Fluorination of Eu-doped layered yttrium hydroxides: the role of anionic composition

“…The hydroxyl ion is an effective luminescence quencher [7]. Therefore, eliminating traces of hydroxyl ions is crucial in synthesizing inorganic phosphors.…”

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

“…A surfactant of alkaline solution of ammonium tartrate was used during syntheses in order to provide the colloidal properties to the surface of LaPO4 NPs for the ability to form the stable aqueous solutions in the neutral or weakly alkaline aqueous media. To study the effect of synthesis parameters on the obtained NPs, several series of syntheses of LaPO4: Pr 3+ (1 at.%) NPs were carried out by the HTMW method (200 °C, 2 hours, 2 magnetrons, 2.45 GHz).The influence of various parameters on the morphology and intensity of UV-C luminescence of NPs was studied: the use of solutions of tartaric acid (TA) and ammonium hydroxide (NH4OH) with different amounts of added TA (CTA = 0.027 or 0.08 M) at pH values of 8 or 9, various ratios of excess anions to cations (excess ratio of K2HPO4 = 1 -10), two concentrations of LaPO4: Pr 3+ in the reaction mixture ( Aggregation processes of colloidal NPs synthesized by wet-chemistry methods are a wellknown problem in their use for medical and other purposes [27][28][29]. They can occur both during the synthesis of NPs and during the storage of their solutions.…”