The thesis aims to shed some light on the massive production of up-converting nanocrystals through solvothermal conditions. Solvothermal route allows to prepare larger quantities of these nanomaterials, as compared to normal glassware-based routes, and increase yield of nanomaterials per synthesis. The synthetic route was optimized through thorough analysis of several parameters Then, the produced nanomaterials were used to propose new optical applications in both biological (encapsulation of the nanomaterials within vesicles based on glicolypids under different pH conditions) and technological fields (the solids were entrapped within a soft-matter matrix that, under a critical temperature, underwent a sol-gel transition and permitted in a low-temperature range (below water boiling point) the modulation of matrix emissions). Lastly a microwave - assisted synthesis was studied, as alternative to solvothermal route, to understand the formation of up-converting nanocrystals, which allowed a versatile post-synthetic coating for further applications of the crystals.
