02354nas a2200241   4500008004100000022001400041245014200055210006900197260007300266300001200339490000800351520144600359653001601805653001801821653002101839653001401860653002901874100001901903700002001922700002001942700001801962856013201980       2015                        eng d  a0920-586100aEncapsulation of ultra small metal clusters in silica: evolution of the concept of nanoreactors and the case of Ag-Pd@SiO2 alloy catalyst0 aEncapsulation of ultra small metal clusters in silica evolution   aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG  a114-1200 v2513 a<p>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.</p>10aAg-Pd alloy10aEncapsulation10aSinter resistant10aSintering10aUltra small nanoclusters1 aMondal, Sourik1 aSamanta, Anupam1 aDhar, Basab, B.1 aDevi, Nandini  uhttps://library.ncl.res.in/content/encapsulation-ultra-small-metal-clusters-silica-evolution-concept-nanoreactors-and-case-ag-002275nas a2200205   4500008004100000245010900041210006900150260000800219300001400227490000800241520153900249100002401788700002901812700001801841700002201859700001501881700002001896700002201916856013101938       2017                        eng d00aElectrochemical formation of Fe-V (O) and mechanism of its reaction with water during O-O bond formation0 aElectrochemical formation of FeV O and mechanism of its reaction  cMAR  a3414-34240 v23 3 aA detailed electrochemical investigation of a series of iron complexes (biuret-modified tetraamido iron macrocycles FeIII-bTAML), including the first electrochemical generation of Fe-V(O), and demonstration of their efficacy as homogeneous catalysts for electrochemical water oxidation (WO) in aqueous medium are reported. Spectroelectrochemical and mass spectral studies indicated FeV(O) as the active oxidant, formed due to two redox transitions, which were assigned as Fe-IV(O)/Fe-III(OH2)and Fe-V(O)/Fe-IV(O). The spectral properties of both of these high-valent iron oxo species perfectly match those of their chemically synthesised versions, which were thoroughly characterised by several spectroscopic techniques. The O-O bond-formation step occurs by nucleophilic attack of H2O on FeV(O). A kinetic isotope effect of 3.2 indicates an atom-proton transfer (APT) mechanism. The reaction of chemically synthesised Fe-V(O) in CH3CN and water was directly probed by electrochemistry and was found to be first-order in water. The pK(a) value of the buffer base plays a critical role in the rate-determining step by increasing the reaction rate several-fold. The electronic effect on redox potential, WO rates, and onset overpotential was studied by employing a series of iron complexes. The catalytic activity was enhanced by the presence of electron-withdrawing groups on the bTAML framework. Changing the substituents from OMe to NO2 resulted in an eightfold increase in reaction rate, while the overpotential increased threefold.1 aPattanayak, Santanu1 aChowdhury, Debarati, Roy1 aGarai, Bikash1 aSingh, Kundan, K.1 aPaul, Amit1 aDhar, Basab, B.1 aGupta, Sayam, Sen  uhttps://library.ncl.res.in/content/electrochemical-formation-fe-v-o-and-mechanism-its-reaction-water-during-o-o-bond-formation