Showing papers by "Edamana Prasad published in 2012"
TL;DR: In this paper, the design, synthesis and study of novel low molecular weight gels (LMWG) based on nonamphiphilic pyrene cored poly(aryl ether) dendron derivatives are described.
Abstract: The design, synthesis and study of morphology as well as photophysical properties of novel low molecular weight gels (LMWG) based on non-amphiphilic pyrene cored poly(aryl ether) dendron derivatives are described. Solvent controlled self-assembly in the system results in nano-sized vesicles, which further aggregate to micro-sized vesicles and finally turned to entangled fibrillar type arrangement in the gel phase. The morphology transformations were investigated by dynamic light scattering (DLS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and confocal laser scanning microscopy (LSCM) experiments. The nano-/micro-sized vesicles and fibre aggregates exhibit an intense light emitting property from the pyrene moiety, which is attached to the dendron through an acylhydrazone spacer group. More interestingly, the luminescence properties were found to be controlled by the solvent polarity, in a rather unusual manner, due to the selective formation of pyrene ‘excimer’ and ‘exciplex’ in solvent controlled aggregates. Furthermore, the system has been utilized to detect fluoride ions through a reversible gel–sol transition, which is associated with a color change from yellow to red.
43 citations
TL;DR: The results described herein imply that the present difficulty of manipulating the extremely reactive excited state of Sm(II) in solution phase can be overcome through stabilizing the excitedstate of the divalent metal ion by careful design of the ligand systems.
Abstract: Electron transfer from the ground and excited states of Sm[15-crown-5]2I2 complex to a series of electron acceptors (benzaldehyde, acetophenone, benzophenone, nitrobenzene, benzyl bromide, benzyl c...
12 citations
TL;DR: In this paper, the detection of Cu(II) and NO at micro and nano-molar concentrations, respectively, by poly(aryl ether) dendron derivatives containing anthracene moiety attached through an acylhydrazone "molecular loop" was reported.
Abstract: We report the detection of Cu(II) and NO at micro and nano-molar concentrations, respectively, by poly(aryl ether) dendron derivatives containing anthracene moiety attached through an acylhydrazone ‘molecular loop’. In the absence of Cu(II), the acylhydrazone moiety undergoes cis–trans photo-isomerization, resulting in negligible emission from anthracene. Conversely, specific binding of Cu(II) by the acylhydrazone unit arrests the isomerization process and triggers aggregation of the molecules through hydrogen bonding and π–π interactions. The metal ion driven self-assembly leads to significant enhancement of the emission intensity from the anthracene excimer with a dendritic effect on the emission quantum yield (maximum Φexcimer emis. ∼0.11 ± 0.01). The binding constants (log K) for the 1 : 1 complexes between the dendron derivatives and Cu(II) were determined using a fluorescence titration method and the values fall between 9.13 and 10.16. The Cu(II)–dendron systems were then exposed to nitric oxide (NO) along with other gases and the systems exhibit specific fluorescent ‘off’ signal towards NO at nano-molar concentrations. The mechanism of quenching was analyzed and the results suggest that the presence of NO leads to de-aggregation in the system.
10 citations