A silica nanoparticle comprising a. a micelle, said micelle having a hydrophilic shell and a hydrophobic central portion; b. a core, which is located in the area of the micelle central portion and comprises a silicate network; c. a plurality of molecules of at least a surfactant, which molecules comprise at least a molecule of a functionalized surfactant having the following structure: M 1 -Hydro 1 -Lipo-Hydro 2 - M 2 wherein Lipo represents a hydrophobic chain, Hydro 1 and Hydro 2 represent, independently of each other, a respective hydrophilic chain; M 1 is a recognition functionality; M 2 is selected from the group consisting of: -H, -OH, a recognition functionality and a hetero group; d. a first and at least a second dye in said core b); wherein said first and/or said at least second dye are covalently linked to the silicate network of said core b) or said first and/or said at least second dye are insoluble in water, whereby they are confined in said core b); and wherein said first and said at least second dye have a respective relationship of donor-acceptor couple in an energy transfer process and have a molar absorption coefficient ε ≥ 10,000 M -1 cm -1 for the considered spectral region, a fluorescence quantum yield φ ≥ 0.01, an overlap integral J defined according to the Förster theory that is greater than 1 x 10 12 M -1 cm -1 nm 4, between said donor and said acceptor dye; said dyes may be lipophilic or may present a functionality useful for the introduction of a trialkoxysilane moiety. a. a micelle, said micelle having a hydrophilic shell and a hydrophobic central portion; b. a core, which is located in the area of the micelle central portion and comprises a silicate network; c. a plurality of molecules of at least a surfactant, which molecules comprise at least a molecule of a functionalized surfactant having the following structure: M 1 -Hydro 1 -Lipo-Hydro 2 - M 2 wherein Lipo represents a hydrophobic chain, Hydro 1 and Hydro 2 represent, independently of each other, a respective hydrophilic chain; M 1 is a recognition functionality; M 2 is selected from the group consisting of: -H, -OH, a recognition functionality and a hetero group; Lipo represents a hydrophobic chain, Hydro 1 and Hydro 2 represent, independently of each other, a respective hydrophilic chain; M 1 is a recognition functionality; M 2 is selected from the group consisting of: -H, -OH, a recognition functionality and a hetero group; d. a first and at least a second dye in said core b); wherein said first and/or said at least second dye are covalently linked to the silicate network of said core b) or said first and/or said at least second dye are insoluble in water, whereby they are confined in said core b); and wherein said first and said at least second dye have a respective relationship of donor-acceptor couple in an energy transfer process and have a molar absorption coefficient ε ≥ 10,000 M -1 cm -1 for the considered spectral region, a fluorescence quantum yield φ ≥ 0.01, an overlap integral J defined according to the Förster theory that is greater than 1 x 10 12 M -1 cm -1 nm 4, between said donor and said acceptor dye; said dyes may be lipophilic or may present a functionality useful for the introduction of a trialkoxysilane moiety.