Pyrene Scaffold as Real-Time Fluorescent Turn-on Chemosensor for Selective Detection of Trace-Level Al(III) and Its Aggregation-Induced Emission Enhancement.

A pyrene based fluorescent probe, 3-methoxy-2-((pyren-2yl-imino)methyl)phenol (HL), was synthesized via simple one-pot reaction from inexpensive reagents. It exhibited high sensitivity and selectivity toward Al(3+) over other relevant metal ions and also displayed novel aggregation-induced emission enhancement (AIEE) characteristics in its aggregate/solid state. When bound with Al(3+) in 1:1 mode, a significant fluorescence enhancement with a turn-on ratio of over ∼200-fold was triggered via chelation-enhanced fluorescence through sensor complex (Al-L) formation, and amusingly excess addition of Al(3+), dramatic enhancement of fluorescence intensity over manifold through aggregate formation was observed. The 1:1 stoichiometry of the sensor complex (Al-L) was calculated from Job's plot based on UV-vis absorption titration. In addition, the binding site of sensor complex (Al-L) was well-established from the (1)H NMR titrations and also supported by the fluorescence reversibility by adding Al(3+) and EDTA sequentially. Intriguingly, the AIEE properties of HL may improve its impact and studied in CH3CN-H2O mixtures at high water content. To gain insight into the AIEE mechanism of the HL, the size and growth process of particles in different volume percentage of water and acetonitrile mixture were studied using time-resolved photoluminescence, dynamic light scattering, optical microscope, and scanning electron microscope. The molecules of HL are aggregated into ordered one-dimensional rod-shaped microcrystals that show obvious optical waveguide effect.

Solution-phase synthesis of silver nanodiscs in HPMC-matrix and simulation of UV-vis extinction spectra using DDA based method.

Present investigation demonstrates a very simple seed-mediated route, using hydroxypropyl methyl cellulose (HPMC) as stabilizing agent, for the synthesis of silver nanodiscs in aqueous solution. Central to the concept of seed-mediated growth of nanoparticles is that small nanoparticle seeds serve as nucleation centres to grow nanoparticles to a desired size and shape. It is found that the additional citrate ions in the growth solution play the pivotal role in controlling the size of silver nanodiscs. Similar to the polymers in the solution, citrate ions could be likewise dynamically adsorbed on the growing silver nanoparticles and promote the two-dimensional (2D) growth of nanoparticles. Morphological, structural, and spectral changes associated with the seed-mediated growth of the nanoparticles in the presence of HPMC are characterized using UV-vis and TEM spectroscopic studies. Metal nanoparticles have received increasing attention for their peculiar capability to control local surface plasmon resonance (LSPR) when interacting with incident light waves. Extensive simulation study of the UV-vis extinction spectra of our synthesized silver nanodiscs has been carried out using discrete dipole approximation (DDA) methodology.