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Ultrasound Stimulated Nucleation and Growth of a Dye Assembly into Extended Gel Nanostructures

Authors

  • Dr. Joanna M. Malicka,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
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    • These authors contributed equally to this work.

  • Anjamkudy Sandeep,

    1. Photosciences and Photonics Group, Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, 695019 Trivandrum (India), Fax: (+91) 471–2491712, 249018
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    • These authors contributed equally to this work.

  • Dr. Filippo Monti,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
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  • Dr. Elisa Bandini,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
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  • Dr. Massimo Gazzano,

    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
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  • Dr. Choorikkat Ranjith,

    1. Dipartimento di Chimica Organica, Università degli Studi di Milano, Via Golgi 19, 20133 Milano (Italy)
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  • Dr. Vakayil K. Praveen,

    Corresponding author
    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
    • Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
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  • Prof. Dr. Ayyappanpillai Ajayaghosh,

    Corresponding author
    1. Photosciences and Photonics Group, Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, 695019 Trivandrum (India), Fax: (+91) 471–2491712, 249018
    • Photosciences and Photonics Group, Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology (NIIST), CSIR, 695019 Trivandrum (India), Fax: (+91) 471–2491712, 249018
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  • Dr. Nicola Armaroli

    Corresponding author
    1. Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
    • Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche (ISOF-CNR), Via Gobetti 101, 40129 Bologna (Italy), Fax: (+39) 051–6399844
    Search for more papers by this author

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.

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