Indian Association for the Cultivation of Science

About: Indian Association for the Cultivation of Science is a education organization based out in Kolkata, India. It is known for research contribution in the topics: Excited state & Catalysis. The organization has 3867 authors who have published 10457 publications receiving 220098 citations.

Direct synthesis of ZnO nanowire arrays on Zn foil by a simple thermal evaporation process.

Abstract: ZnO nanowire arrays were synthesized on zinc foil by a simple thermal evaporation process at relatively low temperature. Morphology and size controlled synthesis of the ZnO nanostructures was achieved by variation of the synthesis temperature, reaction time and the surface roughness of the substrate. A gas–solid and self-catalytic liquid–solid mechanism is proposed for the growth of nanowires at different temperatures. High-resolution transmission electron microscopy (HRTEM) showed that the as-grown nanowires were of single crystal hexagonal wurtzite structure, growing along the [101] direction. Photoluminescence exhibited strong UV emission at ~382 nm and a broad green emission at ~513 nm with 325 nm excitation. Raman spectroscopy revealed a phonon confinement effect when compared with results from bulk ZnO. The nanowire arrays also exhibited a field emission property.

Role of Surface Coating in ZrO2/Eu3+ Nanocrystals

Abstract: The sol-emulsion-gel method is used for the preparation of Eu3+ ion-doped and coated ZrO2 nanocrystals. Here, we report the role of surface coating, dopant concentration, and temperature of heating in the modification of their crystal structure and photoluminescence properties. It is found that the volume fraction of the tetragonal phase increases from 28.08 to 91.56% because of surface coating. This is a significant modification of the crystal phase in ZrO2 nanocrystals due to surface coating by Eu2O3. It is found that the photoluminescence properties are sensitive to the crystal structure, which is again controlled by surface coating, concentration, and heating temperature. It is found that the decay time (tau) of Eu-doped ZrO2 nanocrystals increases with increasing the concentration of dopant and with increasing the temperature of heating because of changes in their crystal phase. The emission intensity of the peak at 611-617 nm (5D0 --> 7F2) of the Eu3+ ion-activated ZrO2 nanocrystals (doped and coated) is also found to be sensitive to the nanoenvironment. The average decay times are 770 and 488 mus for 1100 degrees C-heated 1.0 mol % Eu2O3-doped and coated ZrO2 nanocrystals, respectively. Our analysis suggests that the site symmetry of the ions plays the most important role in the modifications of the radiative and nonradiative relaxation mechanisms as a result of the overall photoluminescence properties.

Solvent-controlled halo-selective selenylation of aryl halides catalyzed by Cu(II) supported on Al2O3. A general protocol for the synthesis of unsymmetrical organo mono- and bis-selenides.

Abstract: Alumina-supported Cu(II) efficiently catalyzes selenylation of aryl iodides and aryl bromides by diaryl, dialkyl, and diheteroaryl diselenides in water and PEG-600, respectively, leading to a general route toward synthesis of unsymmetrical diaryl, aryl-alkyl, aryl-heteroaryl, and diheteroaryl selenides. A sequential reaction of bromoiodobenzene with one diaryl/diheteroaryl/dialkyl diselenide in water and another diaryl/diheteroaryl/dialkyl diselenide in PEG-600 in the second step produces unsymmetrical diaryl, diheteroaryl, or aryl-alkyl bis-selanyl benzene. A library of functionalized organo mono- and bis-selenides, including a potent biologically active molecule and a couple of analogues of bioactive selenides, were obtained in high yields by this protocol. The reactions are chemoselective and high yielding. The Cu-Al2O3 catalyst is recycled for seven runs without any appreciable loss of activity.

Functionalized Plasmonic-Fluorescent Nanoparticles for Imaging and Detection

Abstract: Plasmonic-fluorescent composite nanoparticles are considered as unique, multifunctional nanoprobes for plasmon- and fluorescence-based imaging and detection. However, their synthesis is challenging due to fluorescence quenching of the fluorophore by plasmonic particles and most of the successful methods produce composite particles of large size (diameter > 50 nm), which limit their wider applications. Here we report 20-30 nm diameter plasmonic-fluorescent composite nanoparticles with reasonable fluorescence quantum yield (12-16%). These particles are composed of 3-6 nm diameter Au/Ag cores and fluorescein-incorporated polymeric shells. They have high water solubility, good colloidal stability, stable fluorescence properties, and are amenable in deriving various functional nanoprobes. Different functional nanoprobes are derived from these composites and successfully used for fluorescence-based cell labeling as well as plasmon-based detection applications.