_Applied_  
_sciences_  
_Article_  
**Encapsulation of Dual Emitting Giant Quantum Dots**  
**in Silica Nanoparticles for Optical Ratiometric**  
**Temperature Nanosensors**  
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and for assisting early diagnosis and therapy. Temperature influences the equilibrium constants and biochemical reaction kinetics in fundamental cell processes, including enzyme activity, gene expression, cell division and energy metabolism [1; 2; 3; 4]. In cases of diseases such as cancer, pathological studies have revealed that malignant cells in tissues change their metabolic activities, leading to acute deviation of the intracellular temperatures from the normal state [1; 2; 3; 4]. Furthermore, accurate information on the local temperature profile is also relevant in carrying out therapeutic treatments, such as phototherapy, for the selective and local killing of diseased cells, to avoid unwanted destruction of the healthy tissue surrounding the treated area. Since temperature variation inside cells occurs typically at a very small length scale [5], conventional thermal sensors based, for example, on thermocouples cannot be effectively applied due to their low spatial resolution. They generally operate in the contact mode, thus requiring a challenging fabrication procedure to miniaturize thermometers down to nanometer regime for temperature detection in cells. Such essential requirements have stimulated research on the design and development of novel nanoscale temperature sensors [6], able to provide an accurate and sensitive temperature measurement with high spatial resolution. Different types of nanothermometers [7; 8; 9; 10; 11; 12] have been developed that offer a direct read-out of the temperature by transducing a temperature-dependent change of an optical property of the selected material, such as absorption, emission or Raman scattering. In this regards, fluorescent nanoparticles (NPs), such as quantum dots (QDs) [9; 13; 14], luminescent semiconductor [15], carbon dots [12; 16], rare earth doped up-converting or down-converting NPs [1; 7; 8; 17; 18], polymeric particles [2; 3; 11; 19] or organic dyes [10] are emerging as promising luminescence nanothermometry devices. They take advantage of the thermally induced changes of a fluorescence characteristic such as band intensity, band shape, spectral position and lifetime for a precise, and often multiparametric and ratiometric, [3; 7; 9; 10; 20] temperature detection. Due to the complex cellular environment, fluorescent temperature sensors for in vitro measurements need to be bright enough to overcome the background signals and the autofluorescence from cellular materials, being, at the same time, non-toxic for the cells in long term cellular studies. Inorganic semiconductor QDs, characterized by a high quantum yield and superior photostability, represent fluorescent systems more robust than organic dyes that, conversely, suffer from too fast fluorescence bleaching, thus appearing inappropriate for long term monitoring [21].