@article { ISI:000311971400028, title = {Novel porous silica encapsulated Au nanoreactors as peroxidase mimic for one-pot glucose detection}, journal = {New Journal of Chemistry}, volume = {36}, number = {12}, year = {2012}, month = {DEC}, pages = {2625-2629}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

The peroxidase family of natural enzymes facilitate H2O2 reduction by one electron transfer through aromatic substrates, if chromogenic, they can be used in the colorimetric detection of H2O2 and subsequently glucose in tandem with glucose oxidase. Au nanoparticles encapsulated within porous silica exhibited peroxidase mimetic activity and kinetic parameter evaluation indicates an excellent affinity for H2O2. It is also shown to have a detection capability for glucose in very low concentrations and could be used for glucose detection in a one-pot assay. The material is synthesised by using cation-ended thiol-stabilised ultra small gold clusters as precursors. Removal of the thiols creates micropores within the silica, making this material unique in that the active centres are protected inside the silica, yet are accessible to reactant molecules. This characteristic makes the material ideal as a detection tool where attrition resistance will be advantageous.

}, issn = {1144-0546}, doi = {10.1039/c2nj40665a}, author = {Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @article { ISI:000299584800014, title = {Ultrasmall gold cluster arrays encapsulated in silica nanospheres: applications in fluorescence imaging and catalysis}, journal = {Journal of Physical Chemistry C}, volume = {116}, number = {2}, year = {2012}, month = {JAN}, pages = {1748-1754}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Facile synthesis of ultrasmall gold nanoclusters of size \<2 nm dispersible in water using a novel quaternary ammonium ligand is reported. Further, arrays of these nanoclusters are encapsulated in monodisperse silica nanospheres of size 25-30 nm. The photophysical characteristics of the clusters are found to be intact upon encapsulation, rendering the resulting composite material ideal for fluorescence imaging applications. We have further shown the utilization of these materials in catalysis as precursors for Au nanopartides encapsulated in porous silica.

}, issn = {1932-7447}, doi = {10.1021/jp2093737}, author = {Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @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} } @article { ISI:000329137400042, title = {Selective imaging of quorum sensing receptors in bacteria using fluorescent Au nanocluster probes surface functionalized with signal molecules}, journal = {ACS Applied Materials \& Interfaces}, volume = {5}, number = {24}, year = {2013}, month = {DEC}, pages = {13076-13081}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Fluorescent ultrasmall gold clusters decorated with bacterial quorum sensing signal molecules, acyl homoserine lactone, are synthesized. These fluorescent probes are found to have emission in the near-infrared spectral region advantageous for bioimaging. Imaging studies using different. strains of bacteria with and without acyl homoserine lactone receptors with the aid of confocal microscopy have shown that the probe interacts preferentially with cells possessing these receptors. This indicates that, with appropriate surface functionalization, the Au clusters can be used for receptor specific detection with enhanced selectivity.

}, keywords = {Au nanoclusters, Biosensor, fluorescence imaging, quorum sensing}, issn = {1944-8244}, doi = {10.1021/am404093m}, author = {Mukherji, Ruchira and Samanta, Anupam and Illathvalappil, Rajith and Chowdhury, Somak and Prabhune, Asmita and Devi, R. Nandini} } @article { ISI:000332388900042, title = {Confined space synthesis of fully alloyed and sinter-resistant AuPd nanoparticles encapsulated in porous silica}, journal = {Journal of Materials Chemistry A}, volume = {2}, number = {12}, year = {2014}, month = {JAN}, pages = {4398-4405}, publisher = {ROYAL SOC CHEMISTRY}, type = {Article}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Facile synthesis of highly sinter-resistant silica encapsulated Au-Pd alloy nanocatalysts with average particle size stabilized at similar to 4.5 nm even after calcination at 750 degrees C temperature is reported. The synthesis was achieved by utilizing thiol protected ultra small clusters of Au and Pd as precursors for silica encapsulation. The presence of intimate mixtures of the clusters within silica encapsulation ensures the formation of fully alloyed nanoparticles at high temperatures, at the same time controlling further growth and sintering. At optimum alloy compositions, these catalysts showed high catalytic activity for CO oxidation displaying low light-off temperatures.

}, issn = {2050-7488}, doi = {10.1039/c3ta15194h}, author = {Samanta, Anupam and Rajesh, Thattarathody and Devi, R. Nandini} } @article { ISI:000354137000018, title = {Encapsulation of ultra small metal clusters in silica: evolution of the concept of nanoreactors and the case of Ag-Pd@SiO2 alloy catalyst}, journal = {Catalysis Today}, volume = {251}, year = {2015}, note = {7th Tokyo Conference on Advanced Catalytic Science and Technology (TOCAT), Kyoto, JAPAN, JUN 01-06, 2014}, month = {AUG}, pages = {114-120}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The concept of encapsulation of ultra small clusters within silica evolved as a means to address the sintering of active metal nanoparticles and subsequent deactivation observed in supported noble metal catalysts. It is hypothesised that sintering, which mainly occurs due to mobility of metal species on the support surfaces, can be minimised if the growth and movement of metal nanoparticles are constrained. First, nanoparticles are isolated inside 1D channels in 2D mesoporous compounds and the idea develops to complete encapsulation of thiol protected ultra small nanoclusters in silica spheres. Sintering is better controlled in the latter due to the confined space for growth of nanoparticles. Access of reactant molecules to the active metal surfaces also is ensured by porosity created in the silica matrix forming the basis of the concept of nanoreactors. In this paper, we elaborate on the evolution of this concept from our earlier work on highly sinter resistant silica encapsulated Au, Pd and Au-Pd alloys to the present system of Ag-Pd alloy encapsulated in silica. Silver, with the lowest Tammann temperature among noble metals, is highly prone to sintering which is adequately controlled by alloying with Pd as well as encapsulation in silica. Its enhanced activity in paranitrophenol reduction in comparison with pure metals indicates the advantageous effect of alloying. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Ag-Pd alloy, Encapsulation, Sinter resistant, Sintering, Ultra small nanoclusters}, issn = {0920-5861}, doi = {10.1016/j.cattod.2014.11.006}, author = {Mondal, Sourik and Samanta, Anupam and Dhar, Basab B. and Devi, R. Nandini} } @article {44411, title = {Ultra small nanoclusters to nanoparticles: fine tuning of particle size in water dispersible cation functionalized thiolate protected Pd system}, journal = {Materials Today-Proceedings}, volume = {4}, year = {2017}, month = {MAR}, pages = {9440-9444}, abstract = {Monolayer protected noble metal nanoparticles have attracted considerable attention in the past decade with potential applications in fields ranging from catalysis to biosensors [1, 2,]. We have developed a novel procedure for the synthesis of water dispersible Pd nanoparticles based on a bifunctional ligand, N,N,N-tripropyl(11-mercaptoundecyl) ammonium chloride in which thiol group binds to the metal, hydrophobic middle alkyl chain acts as capping agent and provides steric stability and on the other end the ammonia group helps in making nanoparticles hydrophilic. In this paper, we report the fine-tuning of size of water dispersible Pd nanosystems ranging from clusters to nanoparticles by adjusting the synthetic parameters and their characterization. (C) 2017 Elsevier Ltd. All rights reserved.}, author = {Dhanraj, Prakriti and Samanta, Anupam and Devi, R. Nandini} } @article {46702, title = {Photocatalytic hydrogen generation and CO2 conversion using g-C3N4 decorated dendritic fibrous nanosilica: role of interfaces between silica and g-C3N4}, journal = {ACS Applied Energy Materials}, volume = {3}, year = {2020}, month = {SEP }, pages = {8150-8158}, type = {Article}, abstract = {

We have synthesized g-C3N4 decorated over dendritic fibrous nanosilica (DFNS). The generation of C-N-Si interfaces by coating each fiber of DFNS with g-C3N4 not only provided high surface area but also affected the optical and electronic properties of the composite. The catalyst synthesis reproducibility issue of g-C3N4 was resolved using a vacuum-sealed quartz tube. The extended light absorption in the visible region, enhanced lifetime of photogenerated charge carriers due to the formation of interfaces between silica and g-C3N4 (confirmed by solid-state NMR), and increased surface area result in the improved photocatalytic activity of DFNS/g-C(3)N(4)for hydrogen generation and CO2 conversion.

}, keywords = {CO2 conversion, DFNS, g-C3N4, Hydrogen generation, nanocatalysts, photocatalysts, Solid-state NMR}, issn = {2574-0962}, doi = {10.1021/acsaem.0c01265}, author = {Rawool, Sushma A. and Samanta, Anupam and Ajithkumar, T. G. and Kar, Yusuf and Polshettiwar, Vivek} }