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Intramolecular Charge Transfer Probe Induced Formation of α-Cyclodextrin Nanotubular Suprastructures: A Concentration Dependent Process

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journal contribution
posted on 31.07.2008, 00:00 by S. Syed Jaffer, Subit Kumar Saha, G. Eranna, Ashok K. Sharma, Pradipta Purkayastha
A suitably sized charge transfer probe of an elongated geometry can induce the formation of α-cyclodextrin nanotubular suprastructures, a rare event because of size restriction of the host. The specific molecular structure is found to be responsible only for the 1:2 guest−host complex formations. No evidence of the formation of the 1:1 complex is found. Steady-state fluorescence anisotropy and atomic force microscopy show that the nanocomposites club with other such species very efficiently to form nanotubes and nanoclusters because of primary interactions through hydrogen bonding and develop nanotubular suprastructures due to secondary interactions. The degree of formation of the suprastructures is found to be very much controlled by the probe concentration. In aqueous environment, 2 μM is observed to be the best concentration for the fluorophore form of large rodlike aggregates. Concentrations as low as 1 μM and as high as 4 μM induce the formation of relatively smaller structures. The findings encourage the applications of cyclodextrin nanotubular clusters toward nanotechnology and pharmaceutical research. The concentration dependent phenomenon will dictate the drug dosage as also the extent of formation of the nanostructures in the formation of insulated nanowires. The work is purely indicating the anchoring capability of the used molecule to form nanotubular α-CD suprastructures which otherwise does not form so frequently.