Sistemas ópticos para la caracterización de sistemas coloidales de nanopartículas y consideraciones teóricas cuánticas : diseño, montaje, prueba y aplicación de un sistema termo óptico (de lente térmica) resuelto en frecuencia.

Abstract

This work applies the frequency resolved thermal lensing (TLFR) model for the thermal characterization of nanosuspensions. First, a TLFR-based optical system was developed, calibrated and automated to measure the thermal diffusivity of samples. The experimental system employs a micro-controller to modulate a pump laser and record the photothermal signal carried by a test laser, ensuring accurate data acquisition. These data are used to calculate the thermal diffusivity and, from this, the thermal conductivity of the suspensions. The variety of mate-rials analyzed made it possible to evaluate the effectiveness of the setup and to perform a comprehensive analysis of the thermal response of the nanofluids. The results showed high sensitivity in the system measurements and good reproducibility. However, limitations in the theoretical model were identified, especially with nanoparticles of complex morphology such as bipyramids. Highlighting the need to consider the shape and composition of nanoparticles in the models. The characterization of core-shell nanoparticles was extended using the Sankar-Loeb (SL) model to calculate the absolute porosity, giving very good estimates. The system was also used to monitor the discharge of the-se nanoparticles, analyzing the evolution of thermal diffusivity over time. From this it is concluded that the system is capable of studying these phenomena in media simulating physiological conditions. This research demonstrates that TLFR is a valuable tool for the characterization of na-nosuspensions and has significant potential for future applications.