Browsing by Author "Manas Pal"

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A Linear Trinuclear Acetate Bridged Cobalt Complex Containing Pyridine-Based Bicompartmental Ligand: Synthesis, Structural, Magnetic, and Electrocatalytic Oxygen Evolution Studies
(American Chemical Society, 2024) Ezhava Manu Manohar; Soumalya Roy; Sujoy Bandyopadhyay; Manas Pal; Smita Singh; Vellaichamy Ganesan; Robert Pełka; Piotr Konieczny; Michał Rams; Hyosung Choi; Srinu Tothadi; Sourav Das
The reaction of Co(OAc)2·4H2O, LH2, and Et3N in a 1.5:1:3 molar ratio affords a linear trinuclear complex, [Co3(L)2(μ-η1: η1-OAc)2(CH3CN)2] (1). The synthesized complex was characterized by single crystal X-ray diffraction studies, and it exhibited better electrocatalytic activity for the oxygen evolution reaction (OER) compared with the catalyst, RuO2. The complex exhibits an overpotential of 380 mV at 10 mA cm-2 current density for the OER, which is better than that of RuO2 (480 mV) under identical experimental conditions. The Tafel slope values of the complex and RuO2 were calculated to determine the kinetics of the electrochemical reaction and were found to be 58 and 85 mV/dec, respectively, which implies its robust heterogeneous OER catalysis. The DC magnetic studies revealed that the coupling between the Co(II) ions through the dioxo bridges was found to be antiferromagnetic, and the best-fit yielded exchange interaction J = −3.077(3) cm-1, zero field splitting parameters D1 = 46.35(6) cm-1 and D2 = 5.831(7) cm-1, g = 2.56(2), θ = 90.3(1) °, and σχT = 2.4 × 10-5. The positive values of D2 are consistent with the orbital singlet ground term 4A2g in the octahedral coordination, which suggest that the central and terminal Co(II) ions show easy-plane anisotropies. © 2024 American Chemical Society
Catalytic reduction of organic dyes at gold nanoparticles impregnated silica materials: Influence of functional groups and surfactants
(2011) Uday Pratap Azad; Vellaichamy Ganesan; Manas Pal
Gold nanoparticles (Au NPs) in three different silica based sol-gel matrixes with and without surfactants are prepared. They are characterized by UV-vis absorbance and transmission electron microscopic (TEM) studies. The size and shape of Au NPs varied with the organo-functional group present in the sol-gel matrix. In the presence of mercaptopropyl functionalized organo-silica, large sized (200-280 nm) spherical AuNPs are formed whereas in the presence of aminopropyl functionalized organo-silica small sized (5-15 nm) Au NPs are formed inside the tube like organo-silica. Further, it is found that Au NPs act as efficient catalyst for the reduction of organic dyes. The catalytic rate constant is evaluated from the decrease in absorbance of the dyemolecules. Presence of cationic or anionic surfactants greatly influences the catalytic reaction. The other factors like hydrophobicity of the organic dyes, complex formation of the dyes with anionic surfactants, repulsion between dyes and cationic surfactant, adsorption of dyes on the Au NPs also play important role on the reaction rate. © Springer Science+Business Media B.V. 2011.
Effect of gold nanoparticles on the electrocatalytic reduction of oxygen by silica encapsulated cobalt phthalocyanine
(Elsevier B.V., 2012) Manas Pal; Vellaichamy Ganesan
Electrocatalysts based on mercaptopropyl functionalized mesoporous silica supported cobalt phthalocyanine (MPS-CoPc) are prepared by co-condensation of 3-mercaptopropyltriethoxysilane and tetraethyl orthosilicate in the presence of cetyltrimethylammonium bromide as a templating agent followed by incorporation of cobalt phthalocyanine (CoPc). Further, gold nanoparticles (Au NPs) are introduced into/onto the MPS-CoPc materials (i.e. Au-MPS-CoPc). Transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-vis diffuse reflectance are employed to investigate structural and physical properties of catalysts. The electrocatalytic behavior of the above materials for dioxygen reduction is evaluated by cyclic voltammetry (CV). The CV results show that the MPS-CoPc and Au-MPS-CoPc modified electrodes are highly active towards the electrocatalytic oxygen reduction. With the incorporation of Au NPs, significant increase in current and considerable decrease in oxygen reduction potential is observed. © 2012 Elsevier B.V. All rights reserved.
Effect of silver nanoelectrode ensembles on the electrocatalytic reduction of NO2- by zinc phthalocyanine
(2010) Manas Pal; Vellaichamy Ganesan
Ag nanoparticles anchored on mesoporous silica materials with and without zinc phthalocyanine (ZnPc) were prepared (Ag-MPS and Ag-MPS-ZnPc respectively). The morphology, structure and composition of the materials were characterized by transmission electron microscopy, X-ray diffraction, UV/vis diffuse reflectance spectra, and X-ray photoelectron spectroscopy techniques. The new materials were used for electrode modification and the nanoelectrode ensemble (NEE) behavior of Ag-MPS and Ag-MPS-ZnPc materials was semi-quantitatively evaluated by cyclic voltammetry. Further, electrocatalytic reduction of nitrite is demonstrated at these NEE. © 2010 Elsevier Ltd. All rights reserved.
Electrocatalytic activity of cobalt Schiff base complex immobilized silica materials towards oxygen reduction and hydrazine oxidation
(Royal Society of Chemistry, 2012) Manas Pal; Vellaichamy Ganesan
In this study, mesoporous silica spheres (MSS) are selected as a host framework to encapsulate Co(salen) and Co(salophen) (where Co(salen) is [N,N′-bis(salicylaldehyde) ethylenediimino cobalt(iii)] and Co(salophen) is [N,N′-bis(salicylaldehyde)-1,2 phenylenediimino cobalt(iii)]), represented as MSS-Co(salen) and MSS-Co(salophen) respectively. The prepared materials were characterized by various physicochemical methods such as diffuse reflectance, UV-vis, FT-IR and electrochemical techniques. Host-guest interactions with a feeble coordination bond (between one apical Si-O - and the Co3+ metal ion) lead to the successful anchoring of Co(salen) and Co(salophen) to this silica framework. These constructed catalyst materials were applied to oxygen reduction studies as well as to the oxidative analytical determination of hydrazine (HZ). Both oxygen reduction (in 0.05 M HClO4) and HZ oxidation (in neutral pH condition) showed significantly low overpotential on MSS-Co(salen) and MSS-Co(salophen) modified glassy carbon (GC) electrodes (GC/MSS-Co(salen) and GC/MSS-Co(salophen), respectively). Additionally, HZ was determined by two different electrochemical techniques, namely cyclic voltammetry (CV) and amperometry. From amperometry, GC/MSS-Co(salen) exhibits a linear calibration range from 10.0 to 210.0 μM for the HZ determination and GC/MSS-Co(salophen) exhibits two segmented linear calibration ranges from 10.0 to 310.0 μM. The CV technique demonstrates similar two segmented calibration plots (from 1.0 to 400.0 μM) for both GC/MSS-Co(salen) and GC/MSS-Co(salophen). © 2012 The Royal Society of Chemistry.
Electrochemical determination of nitrite using silver nanoparticles modified electrode
(Royal Society of Chemistry, 2010) Manas Pal; Vellaichamy Ganesan
In this work, we report the fabrication and characterization of silver nanoelectrode ensembles (Ag-NEEs) on a glassy carbon electrode. For this purpose, Ag nanoparticles (NPs) were anchored to the mercaptopropyl functionalized MCM-41 type silica spheres utilizing the chemisorption property of Ag NPs by -SH groups. The successful anchoring of Ag NPs into the silica matrix is characterized by several techniques including UV-vis diffuse reflectance and X-ray powder diffraction methods. The surface morphology of the Ag-NEEs was assessed by scanning and transmission electron microscopy (SEM and TEM respectively). Further, nitrite (NO2-) is electrocatalytically oxidized at Ag-NEEs, which leads to a sensitive determination of NO2-. The fabrication, characterization, and efficient sensing of NO2- at the Ag-NEEs are presented. © The Royal Society of Chemistry 2010.
Manganese-Schiff base complex immobilized silica materials for electrocatalytic oxygen reduction
(Indian Academy of Sciences, 2014) Vellaichamy Ganesan; Manas Pal; Manoj Tiwari
Curtailment of platinum catalysts loading in fuel cell is a recent central issue. As substitutes, these days several organic metal chelate compounds having featured moieties of M-N2 or M-N2O2 (M = transition metal ion) are being used as cathode catalysts in fuel cells. Here, in this study, we report in detail the electrocatalytic activity of manganese-Schiff base complexes for oxygen reduction reaction in 0.05 M HClO2 at room temperature. Actually, [Mn(salen)]+: [N,N'-bis(salicylaldehyde) ethylenediimino manganese(III)]+ and [Mn(salophen)]+: [N,N'-bis(salicylaldehyde)-1,2-phenylenediimino manganese(III)]+ were introduced into/onto the MCM-41 type silica spheres and used for the electrocatalytic reduction of oxygen. Synthesized materials were characterized by UV-Vis, FT-IR and electrochemical techniques. Significant low overpotential for oxygen reduction in 0.05 M HClO4 on [Mn(salen)]+- and [Mn(salophen)]+-incorporated silica-modified glassy carbon electrodes was observed. © Indian Academy of Sciences.
Photochemical oxygen reduction by zinc phthalocyanine and silver/gold nanoparticle incorporated silica thin films
(2012) Manas Pal; Vellaichamy Ganesan; Uday Pratap Azad
Silver or gold nanoparticles are synthesized using a borohydride reduction method and are anchored simultaneously into/onto the mercaptopropyl functionalized silica. Later, zinc phthalocyanine is adsorbed onto the above materials. Thin films of these materials are prepared by coating an aqueous colloidal suspension of the respective material onto glass plates. Visible light irradiation of these films in oxygen saturated, stirred aqueous solutions effectively reduces oxygen to hydrogen peroxide. The photocatalytic reduction of oxygen is explained on the basis of the semiconducting properties of the silica films. The back electron transfer reaction is largely prevented by means of a sacrificial electron donor, triethanolamine. © 2012 Elsevier B.V.
Zinc phthalocyanine and silver/gold nanoparticles incorporated MCM-41 type materials as electrode modifiers
(2009) Manas Pal; Vellaichamy Ganesan
Mercaptopropyl functionalized ordered mesoporous silica spheres were prepared (MPS). Ag or Au nanoparticles (NPs) were anchored onto the MPS materials (Ag-MPS or Au-MPS). Further, zinc phthalocyanine (ZnPc) was adsorbed into the channels and surface (MPS-ZnPc, Ag-MPS-ZnPc, Au-MPS-ZnPc). Diffuse reflectance studies revealed the successful incorporation of Ag or Au NPs inside the silica spheres with and without ZnPc. TEM images showed the uniform distribution of Ag or Au NPs in the silica spheres of different size ranging from 4 to 22 nm or 6 to 31 nm, respectively. XRD pattern showed average crystallite particle size of 18 or 28 nm for Ag or Au NPs respectively which were reduced to 14 or 16 nm on introduction of ZnPc which oxidizes the metal NPs partially. Chemically modified electrodes were prepared by coating the colloidal solutions of the silica materials on the glassy carbon (GC) electrodes. Electrocatalytic reductions of O2 and CO2 at the modified electrodes were studied. The presence of Ag or Au NPs was found to increase the electrocatalytic efficiency of ZnPc toward O2 reduction by 290% or 70% based on the current density measured at -0.35 V and toward CO2 reduction by 150% or 120% based on the current density measured at -0.60 V respectively. Catalytic rate constants were increased 2-fold for O2 reduction and 8-fold for CO2 reduction due to Ag or Au NPs, respectively, which act as nanoelectrode ensembles. The synergic effect of ZnPc and metal NPs on the electrocatalytic reduction of O2 is presented. © 2009 American Chemical Society.