In strictu sensu an organic–inorganic hybrid material is a combination of organic and inorganic components related by chemical bonds. This concept includes a large variety of materials that can be classified accordingly to the:

Among the molecular hybrids linked by covalent bonds, of particular interest are those derived from sol–gel chemistry routes, because they are the most commonly used hybrids and therefore will occupy a large part of this chapter. The mixing of organic and inorganic components may bring special features to the resulting material in such a way that:

The characteristics of organic–inorganic hybrids can be very useful in the design of thermometric systems. Their excellent mechanical properties and processability make them suitable as hosts for luminescent organic and inorganic thermometric probes (e.g., organic dyes, semiconductor quantum dots (QDs) and tri-valent lanthanide ions, Ln³⁺). The combination of organic and inorganic compounds can also give rise to cooperative effects resulting in an enhancement of the thermometric efficiency, relative to that of the organic or inorganic thermometric probes alone. For instance in inorganic optical thermometers, combination with organic antennas can improve their quantum efficiency. Moreover, new thermometric systems can be designed based on the synergies between organic and inorganic components.^1–6