@article { ISI:000363668200036, title = {Multifaceted core-shell nanoparticles: superparamagnetism and biocompatibility}, journal = {New Journal of Chemistry}, volume = {39}, number = {11}, year = {2015}, month = {AUG}, pages = {8513-8521}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

NicoreAgshell nanoparticles were synthesized by redox transmetallation reaction. Reduction potential match was encouraging to attempt the synthesis of the NicoreAushell system too. However, it could be achieved only after an effective surface modification on the Ni-core. Thorough characterization (UV-Vis spectroscopy, fluorescence spectroscopy, XRD, XPS, FTIR, TEM, and EDX) proved the necessity of surface modification and the success of synthesis of both types of core-shell structures. The chemical composition and topography were determined using STEM-HAADF analysis and EFTEM imaging. Fourier transform infrared (FTIR) spectroscopy confirmed the surface modification of Ni nanoparticles and the interactions involved between the ligands and metals (in the core and/or the shell) at various steps of the synthetic process. Even after the formation of the noble metal shell, the magnetic core was found to retain its superparamagnetic nature. In addition, the Au-shell protected the core from aerial oxidation and decreased toxicity as compared to pristine Ni nanoparticles as observed by MTT assay on normal cells (PBMCs).

}, issn = {1144-0546}, doi = {10.1039/c5nj01481f}, author = {Sardar, Debasmita and Neogi, S. K. and Bandyopadhyay, Sanjoy and Satpati, Biswarup and Ahir, Manisha and Adhikary, Arghya and Jain, Ruchi and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {44169, title = {Metallic cobalt to spinel Co3O4-electronic structure evolution by near-ambient pressure photoelectron spectroscopy}, journal = {Journal of Physical Chemistry C}, volume = {121}, year = {2017}, month = {OCT}, pages = {21472-21481}, type = {Article}, abstract = {

In the present study, valence band (VB) and core level photoelectron spectroscopy was carried out to investigate the electronic structural changes from polycrystalline Co to spinel Co3O4, via CoO at near ambient pressures (NAP; similar to 0.1). O-2 Co and H-2-CoOx gas solid oxidative and reductive interactions, respectively, have been explored with UV photons (He I) or low kinetic energy electrons (\<= 16 eV) under NAP conditions. Typical VB features of Co metal, CoOx Co3O4, and a mixed phase between any two adjacent features were observed and well corroborated with core level changes. Very significant and characteristic changes were observed with Co 3d features in the VB for each stage from Co oxidation to Co3O4 as well as Co3O4 reduction to CoOx Co(3O)4 and CoO can be reversibly obtained by alternating the conditions between 0.1 mbar of H-2 at 650 K and 0.1 mbar of O 2 at 400 K, respectively. A meaningful correlation is observed between the changes in work function with cation oxidation state; small changes in the stoichiometry can strongly influence the shift in Fermi level and changes in work function under NAP conditions. Reversible work function changes are observed at a constant BE (similar to 5 ev) between oxidation and reduction conditions. While the O 2 p derived feature for CoOx was observed at throughout the redox conditions, the Co 3d band and molecular oxygen or hydrogen vibration feature shifts significantly underscoring the physicochemical changes, such as charge transfer energy and hence changes in satellite intensity. The peak close to E-F originated from the 3d(6)L final state of the octahedral Co3+ 3d band of Co3O4.

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.7b06661}, author = {Reddy, Kasala Prabhakar and Jain, Ruchi and Ghosalya, Manoj Kumar and Gopinath, Chinnakonda S.} } @article {43171, title = {Multiple functionalities of Ni nanoparticles embedded in carboxymethyl guar gum polymer: catalytic activity and superparamagnetism}, journal = {Applied Surface Science}, year = {2017}, month = {JAN}, abstract = {Composites comprising of metallic nanoparticles in polymer matrices have allured significant importance due to multifunctionalities. Here a simple protocol has been described to embed Ni nanoparticles in carboxymethyl guar gum (CMGG) polymer. The composite formation helps in the stabilization of Ni nanoparticles which are otherwise prone towards aerial oxidation. Further the nanoparticles retain their superparamagnetic nature and catalytic capacity. Ni-Polymer composite catalyses the reduction of 4-Nitrophenol to 4-Aminophenol very efficiently in presence of NaBH4, attaining a complete conversion under some experimental conditions. Ni-Polymer composite is well characterized using UV{\textendash}vis spectroscopy, FTIR, XPS, powder XRD, TGA, SEM and TEM. A detailed magnetic measurement using superconducting quantum interference device-vibrating sample magnetometer (SQUID-VSM) reveals superparamagnetic behaviour of the composite.}, author = {Sardar, Debasmita and Sengupta, Manideepa and Bordoloi, Ankur and Ahmed, Md. A. and Neogi, S. K. and Bandyopadhyay, Sanjoy and Jain, Ruchi and Gopinath, Chinnakonda S. and Bala, Tanushree} } @article {46135, title = {Morphology-dependent, green, and selective catalytic styrene oxidation on Co3O4}, journal = {Dalton Transactions}, volume = {48}, year = {2019}, month = {APR }, pages = {4574-4581}, type = {Article}, abstract = {

Despite the great successes in the controlled fabrication of nanomaterials with specific composition and morphology, it is still challenging to have the desired control on the defect sites of catalyst materials. For unfolding the mystery of this aspect, catalytic styrene epoxidation was attempted on spinel Co3O4 with two different morphologies, namely, SNR (nanorods prepared by the solvothermal method with the (110) facet), HNR (nanorods prepared by the hydrothermal methodwith the (111) facet) and NC (nanocubes with the (110) facet) were synthesized and subjected to olefin oxidation with O-2. Even without any catalyst pretreatment, all three Co3O4 catalyst systems were found to be active for selective epoxidation of styrene with O-2 at ambient pressure in the liquid phase. The correlation between catalytic activity and selectivity trend suggests that the reaction is highly structure-sensitive and facile on the (110) facet. Temperature-dependent near ambient pressure X-ray photoelectron spectroscopy (NAPXPS) was carried out at 0.1 mbar O-2 pressure to understand the mechanistic aspects. The distinct catalytic activity of NC (110) and SNR (110) can be attributed to the population of defect sites on the catalyst surface. NC morphology with comparatively fewer defect sites shows high activity and selectivity, suggesting that styrene oxidation on Co3O4 is structure-sensitive; however, unlike metal surfaces, fewer defects are more favourable for catalytic styrene epoxidation due to facile adsorption and activation of the substrate and O-2 on Co3+ sites. The present investigations suggest that surface defects need not necessarily increase catalytic activity.

}, issn = {1477-9226}, doi = {10.1039/c8dt05154b}, author = {Jain, Ruchi and Gopinath, Chinnakonda S.} }