@article { ISI:000254872600028, title = {Heteropoly acid encapsulated SBA-15/TiO(2) nanocomposites and their unusual performance in acid-catalysed organic transformations}, journal = {Chemistry-A European Journal}, volume = {14}, number = {10}, year = {2008}, month = {FEB}, pages = {3200-3212}, publisher = {WILEY-BLACKWELL}, type = {Article}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

The preparation of SBA-15/TiO(2) nanocomposites with different loadings of Keggin-type 12-tungsto-phosphoric acid (TPA) nanocrystals in their mesochannels through a simple and effective vacuum impregnation method is reported for the first time. The catalysts have been characterised by various sophisticated techniques, including XRD, HRSEM, and TEM. It has been found that the acidity and the textural parameters of the nanocomposites can be controlled by simply changing the loadings of TPA and TiO(2) or the calcination temperature. TPA and TiO(2) loadings of 15 and 22.4 wt \%, respectively, and a calcination temperature of 1123 K have proved to be optimal for obtaining mesoporous nanocomposite materials with the highest acidity. Moreover, the activities of these catalysts in promoting hydroamination as well as Mannich and Claisen rearrangement reactions have been extensively investigated. The results show that the amount of TPA has a great influence on the activity of the nanocomposites in all of the reactions studied. The effects of other reaction parameters, such as temperature and reaction time, on the conversion and product selectivity have also been studied in detail. A kinetic analysis of the formation of the products under various reaction conditions is presented. It has been found that the activity of the nanocomposite composed of 15 wt \% TPA deposited on 22.4 wt of TiO(2) on SBA-15 in promoting the studied reaction is remarkably higher than the catalytic activities shown by pure TPA, TiO(2)-loaded SBA-15, or TPA-loaded SBA-15. The results obtained have indicated that the acidity and the structural control of the nanocomposite materials are highly critical for obtaining excellent catalytic activity, and the presented highly acidic nanocomposites are considered to show great potential for use as catalysts in promoting many acid-catalysed organic transformations.

}, keywords = {Bronsted acids, mesoporous materials, nanoreactors, nanotechnology, supported catalysts}, issn = {0947-6539}, doi = {10.1002/chem.200701562}, author = {Sawant, Dhanashri P. and Justus, Josena and Balasubramanian, Veerappan V. and Ariga, Katsuhiko and Srinivasu, Pavuluri and Velmathi, Sivan and Halligudi, Shivappa B. and Vinu, Ajayan} } @article { ISI:000258442800007, title = {Nanoreactors for nanostructured materials}, journal = {International Journal of Chemical Reactor Engineering}, volume = {6}, year = {2008}, month = {JAN}, pages = {A62}, publisher = {BERKELEY ELECTRONIC PRESS}, address = {2809 TELEGRAPH AVENUE, STE 202, BERKELEY, CA 94705 USA}, abstract = {

Organized systems such as micelles, reverse micelles, vesicles, polyelectrolyte capsules, liquid crystals, etc., formed through a self-assembling process represent nanoreactors that can be used for preparing nanostructured materials. Besides a fascinating academic subject, these nanoreactors provide a unique way to develop a special type of advanced material for a wide variety of applications in electronics, photonics, biomedical and other areas. The article examines the formation, functioning, properties and special attributes of these nanoreactors with a view towards their engineering analysis, design and possible integration in manufacturing technology.

}, keywords = {nanoreactors, Nanostructured materials, organized self-assemblies}, issn = {1542-6580}, author = {Khomane, Ramdas B. and Kulkarni, Bhaskar D.} } @article { ISI:000320929200041, title = {Pd ultra-small clusters as precursors for silica-encapsulated Pd nanoreactors: highly sinter-resistant catalysts}, journal = {Chemcatchem}, volume = {5}, number = {7}, year = {2013}, month = {JUL}, pages = {1911-1916}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Sintering and consequent deactivation in supported metal catalysts is a severe problem encountered in heterogeneous catalysis. This problem can be addressed by encapsulating active metal nanoparticles within inert oxides such as silica, provided the oxide shell is porous to enable access of reactant molecules to the nanoparticle surface to facilitate catalysis. We report the synthesis of highly sinter-resistant silica-encapsulated Pd catalysts with nanoparticle sizes stabilized at (3.4 +/- 0.6)nm at high temperatures of approximately 750 degrees C. The synthesis was achieved by utilizing thiol-protected ultra-small clusters of Pd as precursors for silica encapsulation. The ultra-small clusters were synthesized by using propyl ammonium functionalised thiols making them water-dispersible and amenable for silica encapsulation. Abundance of organics also aided in creating porosity subsequent to calcination at high temperatures.

}, keywords = {cluster compounds, Encapsulation, nanoreactors, Palladium, silicates}, issn = {1867-3880}, doi = {10.1002/cctc.201200908}, author = {Samanta, Anupam and Devi, R. Nandini} }