title: Ultrasound stimulated nucleation and growth of a dye assembly into extended gel nanostructures.
abstract: A squaraine dye functionalized with a bulky trialkoxy phenyl moiety through a flexible diamide linkage (GA-SQ) capable of undergoing self-assembly has been synthesized and fully characterized. Rapid cooling of a hot solution of GA-SQ to 0 °C results in self-assembled precipitates consisting of two types of nanostructures, rings and ill-defined short fibers. The application of ultrasound modifies the conditions for the supersaturation-mediated nucleation, generating only one kind of nuclei and prompting the formation of crystalline fibrous structures, inducing gelation of solvent molecules. The unique self-assembling behavior of GA-SQ under ultrasound stimulus has been investigated in detail by using absorption, emission, FT-IR, XRD, SEM, AFM and TEM techniques. These studies reveal a nucleation growth mechanism of the self-assembled material, an aspect rarely scrutinized in the area of sonication-induced gelation. Furthermore, in order to probe the effects of nanoscale substrates on the sonication-induced self-assembly, a minuscule amount of single-walled carbon nanotubes was added, which leads to acceleration of the self-assembly through a heterogeneous nucleation process that ultimately affords a supramolecular gel with nanotape-like morphology. This study demonstrates that self-assembly of functional dyes can be judiciously manipulated by an external stimulus and can be further controlled by the addition of carbon nanotubes.
authors.affiliation: Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051-6399844.
authors.forename: Joanna M
authors.initials: JM
authors.lastname: Malicka
authors.forename: Anjamkudy
authors.initials: A
authors.lastname: Sandeep
authors.forename: Filippo
authors.initials: F
authors.lastname: Monti
authors.forename: Elisa
authors.initials: E
authors.lastname: Bandini
authors.forename: Massimo
authors.initials: M
authors.lastname: Gazzano
authors.forename: Choorikkat
authors.initials: C
authors.lastname: Ranjith
authors.forename: Vakayil K
authors.initials: VK
authors.lastname: Praveen
authors.forename: Ayyappanpillai
authors.initials: A
authors.lastname: Ajayaghosh
authors.forename: Nicola
authors.initials: N
authors.lastname: Armaroli
keywords: gels; hybrid materials; nucleation and growth; sonication; squaraine