Cover Picture: Ultrasound Stimulated Nucleation and Growth of a Dye Assembly into Extended Gel Nanostructures (Chem. Eur. J. 39/2013)

• Published in: Chemistry : a European journal Vol. 19; no. 39; p. 12909
• Main Authors: Malicka, Joanna M., Sandeep, Anjamkudy, Monti, Filippo, Bandini, Elisa, Gazzano, Massimo, Ranjith, Choorikkat, Praveen, Vakayil K., Ajayaghosh, Ayyappanpillai, Armaroli, Nicola
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 23.09.2013; Wiley Subscription Services, Inc
• Subjects: Chemistry; gels; hybrid materials; nucleation and growth; sonication; squaraine
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201390149

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.