Noble metal nanoparticles functionalized with novel organic luminophores

Design and synthesis of new organic luminophores with desired structure and photophysical properties for application as fluorescent markers for noble metal nanoparticles is performed. The novel luminophores are 4-methoxy- and 4-pyrollidine derivatives of 1,8-naphthalimide bearing at the imide N atom long methylene chain with SH end groups, which enables their covalent binding to noble metals. The steady state and dynamic photophysical characteristics of the lowest lying singlet and triplet electronically excited states of naphthalimides that specify the luminescence properties of organic molecules on the basis of UV-VIS absorption and fluorescence spectroscopy in solution are determined. The 4-methoxy substituted naphtalimide has strong fluorescence in solution in the blue region of the spectrum at 420 - 450 nm, while the 4-pyrollidine-derivative is characterized by intensive green emission around 500 - 540 nm. The corresponding relative fluorescence quantum yields are extremely high - up to 0.9. The measured natural life time of the first singlet electronically state of 4-methoxy- and 4-pyrrolodine-naphthalimide is between 6 and 10 ns. The novel organic luminophores are applied for fluorescence labeling of both synthetically prepared monolayer protected clusters of Au nanoparticles, and of Au and Ag nanoparticles obtained by picosecond laser ablation.