title: Side chains control dynamics and self-sorting in fluorescent organic nanoparticles.
abstract: To develop fluorescent organic nanoparticles with tailored properties for imaging and sensing, full control over the size, fluorescence, stability, dynamics, and supramolecular organization of these particles is crucial. We have designed, synthesized, and fully characterized 12 nonionic fluorene co-oligomers that formed self-assembled fluorescent nanoparticles in water. In these series of molecules, the ratio of hydrophilic ethylene glycol and hydrophobic alkyl side chains was systematically altered to investigate its role on the above-mentioned properties. The nanoparticles consisting of π-conjugated oligomers containing polar ethylene glycol side chains were less stable and larger in size, while nanoparticles self-assembled from oligomers containing nonpolar pendant chains were more stable, smaller, and generally had a higher fluorescence quantum yield. Furthermore, the dynamics of the molecules between the nanoparticles was enhanced if the number of hydrophilic side chains increased. Energy transfer studies between naphthalene and benzothiadiazole fluorene co-oligomers with the same side chains showed no exchange of molecules between the particles for the apolar molecules. For the more polar systems, the exchange of molecules between nanoparticles took place at room temperature or after annealing. Self-assembled nanoparticles consisting of π-conjugated oligomers having different side chains caused self-sorting, resulting either in the formation of domains within particles or the formation of separate nanoparticles. Our results show that we can control the stability, fluorescence, dynamics, and self-sorting properties of the nanoparticles by simply changing the nature of the side chains of the π-conjugated oligomers. These findings are not only important for the field of self-assembled nanoparticles but also for the construction of well-defined multicomponent supramolecular materials in general.
authors.affiliation: Laboratory of Functional Organic Materials and Devices, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
authors.forename: Adrien
authors.initials: A
authors.lastname: Kaeser
authors.forename: Irén
authors.initials: I
authors.lastname: Fischer
authors.forename: Robert
authors.initials: R
authors.lastname: Abbel
authors.forename: Pol
authors.initials: P
authors.lastname: Besenius
authors.forename: Debarshi
authors.initials: D
authors.lastname: Dasgupta
authors.forename: Martijn A J
authors.initials: MA
authors.lastname: Gillisen
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Portale
authors.forename: Amy L
authors.initials: AL
authors.lastname: Stevens
authors.forename: Laura M
authors.initials: LM
authors.lastname: Herz
authors.forename: Albertus P H J
authors.initials: AP
authors.lastname: Schenning
mesh_terms: D005456:Fluorescent Dyes / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D053758:Nanoparticles / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D009930:Organic Chemicals