SYNTHESIS AND CHARACTERIZATION OF INDUM PHOPHIDE SEMICONDUCTOR NANOCRYSTALS: APPLICATION IN NANOTHERMOMETRY

Work package:
Nanoscale temperature measurement (or nanothermometry) is a major challenge for a wide range of applications. For example, in the fight against cancer, thermotherapy is a medical technique that is often used as a complement to radio- therapy or chemotherapy, whose effects it potentiates [1] . Heating agents can be magnetic [2] or plasmonic [3] nanoparticles (NPs) whose heating power must be controlled to avoid problems of damage to surrounding healthy cells. In a completely different field, such nano-heaters can be used for nanocatalysis[4] . Activity and selectivity depend then directly on the surface temperature of the nanoparticles catalyzing the reactions. However, whether at high or low temperature, nanoscale temper- ature measurement is not trivial, as there can be very significant temperature gradients between the heating element (mag- netic or plasmonic nanoparticle) and its surroundings[5] . Thermometric probes have been described at low temperatures with fluorophores[6] and as well with semiconductor nanocrystals (or quantum dots - QDs)[7] , since their optical properties vary with temperature (Fig- ure). Compared to fluorescent molecules, QDs are more advantageous be- cause they are more robust, they absorb and emit light more efficiently and their optical properties (absorption and emission wavelengths) can be con- trolled with their size. That’s why, in the recent literature, different types of QDs have been studied as nanothermometers like CdSe[8] or complex structure with core and two successive shells PbS/CdS/CdSe[9] . However, the QDs tested in this purpose are mainly composed of scarce, toxic elements such as cadmium, lead or selenium. The cost and highly negative environmental impact of these elements have simulated the search for alternative, more environ- mentally-friendly materials. Among them, indium phosphide -InP- is focus- ing aPention due to the low toxicity of its constituent elements [10] and its promising optical properties like the ability to emit in the near infrared wavelengths which allow to tackle biological applications [11] . During the past 15 years, our group has developed a strong expertise in InP QDs synthesis and more recently, we have started to study the temperature-dependent emission of InP QDs. The aim of this master project is to measure with InP-based QDs the “local” temperature (near to the surface of nano-heaters) of magnetic heating iron-based NPs which can be used for nanocatalysis and nanomedicine. The objectives of this work will be: (i) to prepare highly emitting core-shell InP/ZnS QDs, (ii) to study the chemical transformation of the InP/ZnS QDs during heating, and (iii) the development of instrumental set up and data processing for the temperature measurement. This topic will cover all organometallic chemistry field to QDs formation, characterization & application. It provides an opportunity to get familiar with techniques for synthesizing and handling air-sensitive products (Schlenk line, glove box) and to master a wide range of characterization techniques: NMR spectroscopies, X-ray powder diffraction and electron microscopies (TEM, HRTEM) specific to the study of nano-objects. It will also be an opportunity to refine an experimental installation and become familiar with Python coding. This project could then be extended as part of a thesis, funding for which is already obtained.