Glassy and ceramic multifunctional luminescent nanosystems for applications in thermometry and oximetry

Abstract

The development of remote thermal sensors has attracted much attention in the last decade for temperature monitoring in the microscopic level for the control of biological functions, detection of fires, monitoring of corrosive and electromagnetic environments, etc. Among the possibilities for remote measurement, emphasis is given on the optical techniques that rely on spectral changes induced by temperature variations. Luminescence thermometry explores the dependence of spectral position, bandwidth, intensity, polarization or excited state lifetimes on temperature. Particularly, the Fluorescence Intensity Ratio (FIR) thermometry is the most explored technique, especially in the visible spectral region, because it does not depend on the sample concentration, alignment or excitation power. Less commonly studied is the FIR thermometry in the infrared, taking advantage of the Rare Earth (RE) ions Nd3+, Yb3+ and Tm3+ emissions. For this reason, we propose the study of NaYF4 nanoparticles doped with these ions. the core-shell NPs will be covered with silica layers that will serve as a platform to immobilize quantum dots (QDs) of CdTe e CdS, whose visible emissions respond more sensitively to the presence of molecular oxygen. The QDs that will compose the ""shell"" of the multifunctional NPs are extremely versatile optical probes but present the disadvantages of requiring critical and complicated synthesis conditions, colloidal instability in aqueous media and toxicity in biological media. On the other hand, the incorporation of these species in solid host matrices warrants biocompatibility and the stability of the material in aqueous solution. Taking a step further, in order to secure the versatility of device application, in the bulk or film form, the core-shell NPs will be dispersed in glassy matrices obtained by sol gel methodology. This approach has been successfully used in LEMAF to immobilize YAP:Ce particles in luminescent bulk composites. It is worth mentioning that, besides the main aim of this project which is to obtain multifunctional NPs combining different luminescent species (NaYF4:RE NPs and QDs) - which will be obtained and characterized initially individually, these nanostructures will also serve the research for other possible application such as bioimaging, solar cell efficiency enhancement, development of molecular switches and high order harmonic generation in QD plasmons. Recently, LEMAF has established collaborations with research groups in the University of Münster, Germany, led by Prof. Cornelia Denz (Physics, organic solar cells), Prof. Cristian Strassert (Chemistry, bioimaging), Prof. Bart Jan Ravoo (Nanomaterials, molecular switches) and Prof. Helmut Zacharias (Physics, harmonic generation). The samples obtained in this project will be provided to these research groups giving the opportunity to the student to maximize the application of his materials and his learning opportunities, which can include a scientific internship in Germany or other Country. (AU)