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

Self-assembly of functional organic dyes to form extended nanostructures is a topic of current interest due to possible applications in electronic and optoelectronic devices. Continuous research in this field has developed a number of methods to construct nanostructures with desired shape, function and uses.2 We present the unique behavior of a squaraine derivative GA-SQ, which forms a ill-defined assembly under normal conditions, whereas it generates extended nanostructures and gels upon application of ultrasound .3 With the help of spectroscopic (absorption, emission, FT-IR, XRD) and microscopic (SEM, AFM, TEM) techniques, we demonstrate a nucleation and growth mechanism for the observed self-assembly. Furthermore, the addition of a minuscule amount of single wall carbon nanotubes (SWCNTs) as a nanoscale substrate is found to considerably influence the morphological properties of the GA-SQ sonogel by promoting a heterogeneous nucleation process. This study demonstrates that self-assembly of functional dyes can be manipulated by an external stimulus and can be further controlled by the addition of carbon nanostructures as dopants. 1 A. Ajayaghosh, V. K. Praveen, C. Vijayakumar, Chem. Soc. Rev. 2008, 37, 109. 2 K. Yoosaf, A. Llanes-Pallas, T. Marangoni, A. Belbakra, R. Marega, E. Botek, B. Champagne, D. Bonifazi, N. Armaroli, Chem. -Eur. J. 2011, 17, 3262. 3 J. M. Malicka, A. Sandeep, F. Monti, E. Bandini, M. Gazzano, C. Ranjith, V. K. Praveen, A. Ajayaghosh, N. Armaroli, Chem. -Eur. J. 2013, DOI: 10.1002/chem.201301539.