| Abstract Scope |
One-dimensional (wires and rods) and semi-two-dimensional (ribbons and sheets) organic nanostructures have gained significant interest in recent years because of their novel properties and possible applications in electronics and optoelectronics. In a recent work, we have investigated the aggregated states of an electron donor-acceptor molecule, 4-(9-anthryl)- N,N-dimethylaniline (ADMA), in which an N,N-dimethylaniline (donor) moiety is covalently connected to an anthryl (acceptor) moiety, by synthesizing the nano / micro aggregates following the conventional reprecipitation method. As these aggregates were prepared without using any stabilizer, their morphologies and photophysical properties could not tuned. The present work explores the fabrication and study of the fluorescence response of well-defined 1D or semi-2D nanostructures (rods, ribbons and sheets and ultra-long belts) of ADMA in the presence of various additives. Specifically, we use the surfactants to control the morphology of the aggregates. It is shown that that, in the presence of cationic (CTAB) and anionic (SDS) surfactants ADMA forms well defined nanostructures. Interestingly, in presence of neutral surfactant (TX-100), ADMA behaves differently compared to CTAB and SDS. It is found that these morphologies can be tuned by just changing the solubility of ADMA and their sizes could be tuned by changing the concentration. We believe that the surfactants prevent the formation of larger aggregates by adsorbing at the periphery of nanostructures and help to grow along their preferred crystallographic planes. From the steady state absorption spectra, progressive shift of the aggregated band in the longer wavelength region is observed and is attributed to the increasing the particle size. Structural rigidification of the molecule in the nanoparticles is responsible for the high fluorescence quantum yields compared to the solution. |