Eswaramoorthy M.

Supramolecular Gating of Ion Transport in Nanochannels

Wed, 01 Jan 2014 00:00:00 GMT

Supramolecular Gating of Ion Transport in Nanochannels Kumar, B. V. V. S. Pavan; Rao, K. Venkata; Sampath, S.; George, Subi Jacob; Eswaramoorthy, Muthusamy Several covalent strategies towards surface charge-reversal in nanochannels have been reported with the purpose of manipulating ion transport. However, covalent routes lack dynamism, modularity and post-synthetic flexibility, and hence restrict their applicability in different environments. Here, we introduce a facile non-covalent approach towards charge-reversal in nanochannels (< 10 nm) using strong charge-transfer interactions between dicationic viologen (acceptor) and trianionic pyranine (donor). The polarity of ion transport was switched from anion selective to ambipolar to cation selective by controlling the extent of viologen bound to the pyranine. We could also regulate the ion transport with respect to pH by selecting a donor with pH-responsive functional groups. The modularity of this approach further allows facile integration of various functional groups capable of responding to stimuli such as light and temperature to modulate the transport of ions as well as molecules. Restricted Access

Self-stabilized Pt-Rh bimetallic nanoclusters as durable electrocatalysts for dioxygen reduction in PEM fuel cells

Wed, 01 Jan 2014 00:00:00 GMT

Self-stabilized Pt-Rh bimetallic nanoclusters as durable electrocatalysts for dioxygen reduction in PEM fuel cells Narayanamoorthy, B.; Datta, K. K. R.; Eswaramoorthy, M.; Balaji, S. Self-stabilized Pt-Rh nanoclusters (NCs) were prepared by using a surfactant-free chemical reduction method with formic acid as the reducing agent. The elemental composition was determined by EDX analysis. The synthesized cluster was used as a supportless (SL) electrocatalyst for the reduction of oxygen (ORR) in acid medium. The composition of Pt-Rh bimetal NCs, in terms of atomic weight percentage, was optimized based on the available electrochemical surface area. Hydrodynamic linear scan voltammetric profiles show that the onset potential for oxygen reduction is 0.78 V vs. RHE at the electrode rotation rate of 2400 rpm with 17.8 mu g cm(-2) loading of the SL Pt3Rh exhibiting the limiting current density of 3.5 mA cm(-2). The durability of the electrocatalysts was investigated by performing the accelerated durability test (ADT): the electrochemical surface area (ECSA) for SL Pt3Rh increased by nearly 9.2% while retaining nearly 85% of its initial limiting current density after 15 000 potential cycles. For comparison Vulcan-carbon-supported Pt3Rh was synthesized under identical conditions and subjected to electrochemical investigations. Both supportless and VC-supported Pt3Rh NC electrocatalysts were found to use a direct 4-electron transfer mechanism. In order to improve the activity, SL Pt@Pt3Rh NC was synthesized and used as the catalyst. At 0.9 V, the mass activity (0.085 mA mu g(-1)) of the Pt@Pt3Rh NC was found to be nearly 34 times greater than that of SL Pt3Rh NC (0.0025 mA mu g(-1)). We conclude that the SL Pt3Rh NC could potentially be used as an electrocatalyst for ORR in a sulfuric acid medium since it possesses good stability compared to Pt-based ORR catalysts reported in the literature. Restricted Access

Glucose- and pH-Responsive Charge-Reversal Surfaces

Wed, 01 Jan 2014 00:00:00 GMT

Glucose- and pH-Responsive Charge-Reversal Surfaces Kumar, B. V. V. S. Pavan; Salikolimi, Krishnachary; Eswaramoorthy, M. We have shown a pH- and glucose-responsive charge reversal on silica surface through heterogeneous functionalization utilizing amines and boronic acid moieties. The dual responsiveness of the charge reversal has been unambiguously demonstrated through the desorption of charged chromophores. Interestingly, we observed a concentration-dependent desorption response to glucose at physiologically relevant levels. Restricted Access

Enhanced Intrinsic Activity and Stability of Au-Rh Bimetallic Nanostructures as a Supportless Cathode Electrocatalyst for Oxygen Reduction in Alkaline Fuel Cells

Fri, 01 Jan 2016 00:00:00 GMT

Enhanced Intrinsic Activity and Stability of Au-Rh Bimetallic Nanostructures as a Supportless Cathode Electrocatalyst for Oxygen Reduction in Alkaline Fuel Cells Narayanamoorthy, B.; Balaji, S.; Sita, C.; Pasupathi, S.; Eswaramoorthy, M.; Moon, Il-Shik The electroreduction of dioxygen on supportless Au-Rh bimetallic nanostructures (Au-Rh NSs) synthesized by a surfactant template-free, single step chemical reduction method occurred with high intrinsic activity in an alkaline medium. Cyclic voltammetry and linear scan voltammetry together with X-ray diffraction and high-resolution electron microscopy showed that the improved performance of the Au-Rh NSs toward dioxygen reduction could be due to the synergistic electronic effects of nanobimetallic combination and its clusterlike morphology. The electrochemically active surface area (ECSA) was estimated to be 37.2 m(2) g(-1) for supportless Au-Rh NS with a 3:1 atomic composition, which was higher than that reported for Ag-based nanocatalysts. The intrinsic activities (IA) of the supportless and carbon supported Au-Rh (3:1) NSs were 3.2S and 3.0 mA/cm(2), respectively, which were higher than those of the standard Pt/C (0.1 mA/cm(2))(45) Au/C catalysts for the oxygen reduction reaction (ORR). Oxygen reduction on both catalysts followed a direct four electron pathway. The accelerated durability test carried out by continuous potential cycling showed that the 3:1 ratio of Au-Rh nanostructures had excellent stability with a 20% increase in ECSA after 10 000 potential cycles, highlighting their potential application for real systems. Open Access (Accepted Manuscript)