Fluorescent chemosensors are chemical systems that can detect and signal the presence of selected
analytes through variations in their fluorescence emission. Their peculiar properties make them
arguably one of the most useful tools that chemistry has provided to biomedical research, enabling the
intracellular monitoring of many different species for medical and biological purposes. In its simplest
design, a fluorescent chemosensor is composed of a fluorescent dye and a receptor, with a built-in
transduction mechanism that converts recognition events into variations of the emission properties of
the fluorescent dye. As soon as fluorescent nanoparticles became available, several applications in the
field of sensing were explored. Nanoparticles have been used not only as better-performing substitutes
of traditional dyes but also as multivalent scaffolds for the realization of supramolecular assemblies,
while their high surface to volume ratio allows for distinct spatial domains (bulk, external surface, pores
and shells) to be functionalized to a comparable extent with different organic species. Over the last few
years, nanoparticles proved to be versatile synthetic platforms for the implementation of new sensing
schemes.
