E. Murugan - Academia.edu (original) (raw)

Papers by E. Murugan

Research paper thumbnail of Modification of glassy carbon electrode with trigona carbon nanopetals/ferrocene/gold nanoparticles nanocomposite for electrochemical detection of dopamine

Indian Journal of Chemistry -Section A

In this study, we have synthesized a composite using carbon material derived from bio-inspired on... more In this study, we have synthesized a composite using carbon material derived from bio-inspired onion peel morphology like 2D trigona carbon nano petals (TCP) incorporated with ferrocene (FC). The FC is added with the purpose of improving the electrochemical behaviour of TCP. Further, to increase the number of electrochemically active sites in the composite, gold nanoparticles (AuNPs) were again decorated on TCP/FC, and thus derived electrochemically active TCP/FC/AuNPs nanocomposite. We have characterized the properties and surface morphology of this nanocomposite through spectroscopic and microscopic techniques. Further, using this nanocomposite for surface modification of glassy carbon electrode, we have developed an efficient GCE-TCP/FC/AuNPs electrode. The electrochemical efficiency of this electrode has been inspected through sensing and quantification of pharmaceutically valuable biomolecule dopamine through CV, DPV and square wave voltammetry techniques. The observed CV results reveals that the newly designed GCE-TCP/FC/AuNPs electrode has an ability to detect the dopamine with wide linear range of concentration from 5.96 × 10-6 to 0.1 × 10-4 M and its limit of detection was 2.9 × 10-6 M under 0.1 M phosphate buffer medium (pH 7.0). Therefore, it is important to mention here that this newly fabricated electrode can very well be used for real time sample analysis for sensing and detection of dopamine as it plays a key role in the neurotransmission and causes several diseases.

Research paper thumbnail of Facile synthesis of core-shell nanocomposites Au catalysts towards abatement of environmental pollutant Rhodamine B

Heliyon, 2019

Magnetically recoverable Au nanoparticles immobilized/stabilized on core-shell nanocomposites are... more Magnetically recoverable Au nanoparticles immobilized/stabilized on core-shell nanocomposites are synthesized by the combination of suspension polymerization as well as surface initiator atom transfer radical polymerization (SI-ATRP) methods. The magnetic core-shell supported Au nanocatalysts are namely Fe 3 O 4-PAC-AuNPs, Fe 3 O 4-PVBC-g-PAC-AuNPs, Fe 3 O 4-HEA-AuNPs, and Fe 3 O 4-PVBC-g-HEA-AuNPs. Among all the catalysts, Fe 3 O 4-PVBC-g-PAC-Au NPs exhibited an excellent activity in the reduction of Rhodamine B with an apparent rate constant of 10.77 Â 10 À3 s À1 and TOF value of 47.62 Â 10 À3 s À1 under pseudo-first order reaction condition. Further, Fe 3 O 4-PVBC-g-PAC-Au NPs has an outstanding activity and recyclability without applying any external magnetic field. This new approach provides an exciting potential way in the preparation of recyclable metal nano-catalysts with high catalytic activity.

Research paper thumbnail of Fabrication of GC-r-GO-PAMAM (G3)-Pd electrode for electro-catalytic oxidation of formic acid

Advanced Materials Proceedings, 2018

Graphene functionalized with Poly(amidoamine) dendrimer stabilized PdNPs (r-GO-PAMAM-Pd) composit... more Graphene functionalized with Poly(amidoamine) dendrimer stabilized PdNPs (r-GO-PAMAM-Pd) composite was prepared through facile experimental routes and characterized by FT-IR, XRD, Raman, SEM and EDAX techniques. Initially, poly(amidoamine) generation 3 (PAMAM (G3)) dendrimer was functionalized on graphene oxide (GO) and the resulting matrix was loaded with PdNPs through stabilization and thus produced excellent conducting composite material. The electrocatalytic activity of this composite was inspected by coating on bare GCE and thus produced stable and efficient GC-r-GO-PAMAM (G3)-Pd electrode and this in turn demonstrated for the oxidation of formic acid (FA). The occurrence of the oxidation reaction was monitored by cyclic voltammetric (CV) and linear sweep voltammetric (LSV) techniques in 0.5 M H2SO4 medium at the potential window of-0.3 to 1.0 V vs. Ag/AgCl, v = 50 mVs-1. The observed peak potential for the new electrode was located at 0.15V and compared with existing electrodes derived from different GO/Pd composites. The comparative results reveals that the newly designed electrode shown an excellent catalytic activity, more resistant to the surface poisoning and the anodic onset potential was more negative than the reported electrodes. This improved electrocatalytic performance are due to the contribution of synergetic effect of GO, dendrimer and PdNPs.

Research paper thumbnail of Effective Sidewall Functionalization of Multiwalled Carbon Nanotubes with Dichlorocarbene Addition using New Soluble Multi-site Phase Transfer Catalysts

The novel soluble multi-site phase transfer catalysts (MPTCs), viz., 2,6-bis (triethylammoniummet... more The novel soluble multi-site phase transfer catalysts (MPTCs), viz., 2,6-bis (triethylammoniummethylene chloride)-4-methoxytoluene (BTEACM) and 3,3’,5,5’-tetrakis (dimethylaminopyridinium chloride) biphenyl (TDMAPCB) containing two, and four active sites was synthesized, and characterized through Fourier transform infra red spectroscopy (FTIR), proton nuclear magnetic spectroscopy, carbon nuclear magnetic spectroscopy, thermo gravimetric analysis (TGA) and energy dispersive spectroscopy (EDS) analyses. The obtained MPTCs were used as a catalysts for sidewall functionalization of multiwalled carbon nanotubes (MWCNTs) in dichlorocarbene (CCl 2 ) addition, and compared their functionalization yield with commercially available single site PTC and tri-site PTC viz., benzyltriethylammonium chloride (BTEAC) and 2,4,6-tris (triethylammoniummethylene chloride) mesitylene (TTEAMCM). The functionalization of CCl 2 on MWCNTs was established by the appearance of increased peak intensity of C-Cl ...

Research paper thumbnail of Triphase catalysis synthesis and characterization of surface enriched polymer supported phase transfer catalysts and their application in some organic addition reactions a kinetic study

Research paper thumbnail of Preparation of surface-enriched polymersupported phase transfer catalysts and kinetics of dichlorocarbene addition to cycylohexene using 50 % NaOH

Indian journal of chemistry. Sect. A: Inorganic, physical, theoretical & analytical, 1997

Research paper thumbnail of Phase Transfer Catalysis:Effect of Cationic Surfactants on the Free Radical Polymerization of Methylmethacrylate

The effect of cationic surfactants, decyltrimethylammonium bromide (DTAB), dodecyltrimethylammoni... more The effect of cationic surfactants, decyltrimethylammonium bromide (DTAB), dodecyltrimethylammonium bromide (DDTAB) and tetradecyltrimethylammonium bromide (TDTAB), has been studied as phase transfer catalysts (PTCs) on the free radical polymerization of methylmethacrylate (MMA) using potassium peroxydisulfate (PDS, K 2 S 2 O 8 ) in toluene-water biphase system. Of the three PTCs in their respective critical micellar concentration (CMC) and in common concentration, the TDTAB show comparatively high rate of polymerization (Rp), 7.76 × 10 -5 mol.L -1 .S -1 , at the lowest reaction time of 30 min in its concentration of 2 × 10 -2 mol.L -1 . Detailed kinetic study of polymerization of MMA has been carried out using TDTAB at a fixed time of 30 min by varying [MMA], [K 2 S 2 O 8 ], [TDTAB] and temperature. Based on the kinetic results, the free energy of activation has been calculated, and a suitable mechanism and rate law has been proposed.

Research paper thumbnail of New Polymer-Supported Multi-Site Phase Transfer Catalyst in Dichlorocarbene Addition to Styrene

Research paper thumbnail of Synthesis, characterization, and catalytic activity for hybrids of multi-walled carbon nanotube and amphiphilic poly(propyleneimine) dendrimer immobilized with silver and palladium nanoparticle

Four types of new multi-walled carbon nanotube (MWCNT) based nanohybrid catalysts were prepared t... more Four types of new multi-walled carbon nanotube (MWCNT) based nanohybrid catalysts were prepared through simple methods. Initially, MWCNT was functionalized with carboxyl group and subsequently bonded with amphiphilic poly(propyleneimine) dendrimer (APPI) having generation (G2) and (G3). They are abbreviated as MWCNT-APPI (G2) and MWCNT-APPI (G3). Silver nanoparticles (AgNPs) and palladium nanoparticles (PdNPs) were separately immobilized to each hybrid to obtain four types of MWCNT based nanohybrid catalysts. The pseudo-first order rate constants for reduction of 4-nitrophenol revealed that among the four types of MWCNT nanohybrid catalysts, MWCNT-APPI (G3)-PdNPs was more efficient than the other catalysts with five-fold higher efficiency than the homogeneous PPI (G3)-PdNPs. For the same reaction with MWCNTs-APPI (G3)-PdNPs catalyst, the variation of [catalyst] and [NaBH4] was directly proportional to kobs. The study of reusability of MWCNT-APPI (G3)-PdNPs proved no loss in activity...

Research paper thumbnail of Separate and simultaneous determination of vanillin, theophylline and caffeine using molybdenum disulfide embedded polyaniline/graphitic carbon nitrite nanocomposite modified glassy carbon electrode

Diamond and Related Materials

Research paper thumbnail of Rationally designed SERS AgNPs/GO/g-CN nanohybrids to detect methylene blue and Hg2+ ions in aqueous solution

Research paper thumbnail of Silver nanoparticles decorated g-C3N4: An efficient SERS substrate for monitoring catalytic reduction and selective Hg2+ions detection

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Research paper thumbnail of Highly sensitive, stable g-CN decorated with AgNPs for SERS sensing of toluidine blue and catalytic reduction of crystal violet

Journal of Materials Science

SERS substrates with high sensitivity, SERS enhancement and stability are essential for fabricati... more SERS substrates with high sensitivity, SERS enhancement and stability are essential for fabrication of SERS sensors to detect dyes at low concentration. Such substrates generally have a versatile support bonded to metal nanoparticles of optimum size. Simple methodology that yields SERS substrates with reproducible results is mostly desired for sensor fabrication. In this study, silver ions were reduced with safe reducing agent NaBH4 to Ag metal nanoparticles (AgNPs) in the presence of previously prepared g-CN to obtain g-CN decorated with silver nanoparticles (AgNPs@g-CN) of average diameter 22 nm. The results of XPS and UV–Vis spectroscopy unambiguously establish significant interaction between the nitrogen sites of g-CN and AgNPs. The AgNPs@g-CN yielded very high SERS enhancement for toluidine blue at very low concentration (2.5 × 10−09 M), and the SERS results are reproducible. The surface enhancement factor (EF) is one of the important criteria to evaluate and compare SERS materials, and it was equal to 9.13 × 106 toward toluidine blue. The catalytic activity of the substrate for the reduction of crystal violet (CV) to its leuco-form was tested with NABH4. The reaction was monitored by UV Vis spectroscopy. There was a rapid fall in intensity of CV. The reduction of CV mainly occurred via electron transfer from AgNPs, and the product did not interfere with the absorbance of CV. Hence, AgNPs@g-CN could be a convenient choice for fabrication of commercial SERS sensors for detection of dyes at low concentrations. It is also useful as a catalyst for the reduction of organic dyes.

Research paper thumbnail of Amphiphilic Dendrimer Stabilized Ag, Pd And Pt Homogeneous Nanoparticle Catalysts And Their Catalysis For The Reduction Of Methyl Orange

Two different amphiphilic poly(propyleneimine) dendrimers (APPI-G2-(N+Cl-)x) were synthesized by ... more Two different amphiphilic poly(propyleneimine) dendrimers (APPI-G2-(N+Cl-)x) were synthesized by reductive methylation of poly(propyleneimine) dendrimer with HCOOH/HCHO and thus yield methylated dendrimer having eight dimethyl amino end groups. This in turn was converted into amphiphilic form via quaternization with 1-bromooctane. By varying the mole ratio of alkyl bromide to dendrimer, averages of 5&10 quaternary ammonium groups were generated individually. The prepared amphiphilic dendrimer templates were used individually and stabilized the Ag, Pd and PtNPs. The resultant homogeneous nanoparticle catalysts were characterized with UV-Vis, FESEM and EDS techniques. The catalytic activity of the APPI-G2-(N+Cl-)x -NPs were examined through reduction of methyl orange under pseudo-first order condition at ambient temperature. The catalytic efficiency of these catalysts were found in the order of APPI-G2-(N+Cl-)5 -PdNPs > APPI-G2-(N+Cl-)5 –AgNPs > APPI-G2-(N+Cl-)5 –PtNPs.

Research paper thumbnail of A novel Steroid from Elephantopus scaber L. an Ethnomedicinal plant with antidiabetic activity

Phytomedicine, 2009

Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels ... more Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels in streptozotocininduced diabetic rats significantly. Acute toxicity studies revealed the non-toxic nature of the crude extract. Fractionation of the acetone extract yielded a new steroid, 28Nor-22(R)Witha 2,6,23-trienolide. Biological testing of the compound demonstrated a significant antidiabetic activity by reducing the elevated blood glucose levels and restoring the insulin levels in streptozotocin-induced diabetic rats. This compound can be a useful candidate to treat diabetes.

Research paper thumbnail of Catalysis by Hydrophobically Modified Poly(propylenimine) Dendrimers Having Quaternary Ammonium and Tertiary Amine Functionality

Langmuir, 2004

Four different quaternary ammonium chloride-modified poly(propylenimine) (PPI) dendrimers were sy... more Four different quaternary ammonium chloride-modified poly(propylenimine) (PPI) dendrimers were synthesized by alkylation of a PPI dendrimer having eight dimethylamino end groups with 1-bromooctane or 1-bromododecane. By varying the mole ratio of alkyl bromide to dendrimer, averages of 4-10 quaternary ammonium groups were formed. The new amphiphilic dendrimers are surface active and are micellar catalysts in water. The dendrimers have critical aggregation concentrations between 8.5 x 10(-4) and 9.0 x 10(-5) M. Decarboxylation of 6-nitrobenzisoxazole-3-carboxylate at 25 degrees C was 650 times faster than in water alone in the presence of a dendrimer quaternized with eight dodecyl chains at a concentration of 2.45 mM in quaternary ammonium groups. The order of the catalytic efficiency of the new dendrimers decreased with the length and number of hydrophobic alkyl groups in the order (C(12))(8) > (C(12))(4) > (C(8))(10) > (C(8))(5). The pseudo-first-order rate constants for basic hydrolysis of p-nitrophenyl hexanoate in pH 9.4 buffer at 30 degrees C using the (C(12))(8) and (C(12))(4) dendrimers were 26 and 13 times higher than those for hydrolysis with no dendrimer. The kinetic data were fit to a single-site binding model to evaluate the contributions of binding constants of reactants to the dendrimers and catalytic rate constants of the bound species to the overall catalytic activity.

Research paper thumbnail of Preparation and spectroscopic characterization of surface-enriched (with active sites) polymer-supported phase-transfer catalysts and their efficiency in organic addition reactions: A kinetic study

Journal of Polymer Science Part A: Polymer Chemistry, 2003

Research paper thumbnail of Preparation of a novel soluble multi-site phase transfer catalyst and the kinetic study for the C-alkylation of α-pinene

Journal of Molecular Catalysis A: Chemical, 2005

Novel soluble “multi-site” phase transfer catalyst viz.1,3,5-tris(4-(2,2′-bis(N-triethylammoniumm... more Novel soluble “multi-site” phase transfer catalyst viz.1,3,5-tris(4-(2,2′-bis(N-triethylammoniummethylene chloride)eth-1-ene)phenoxymethyl)benzene (TBTEAPB) was synthesized and characterized by different spectral techniques such as FT-IR, 1H NMR, 13C NMR, MALDI-TOF mass and chloride ion analysis. The catalytic potential of this new multi-site TBTEAPB phase transfer catalyst was demonstrated by the C-alkylation of α-pinene with epichlorohydrin using low concentration of base (20% NaOH) at 40°C. The

Research paper thumbnail of A Modified Method for the Synthesis and Characterization of a Novel Surface-Enriched (with Active Site) Polymer-Supported Phase Transfer Catalyst Using Vinyltoluene as a Functionality and Its Catalytic Efficiency in Dichlorocarbene Addition to Olefines—A Kinetic Study

Journal of Macromolecular Science, Part A, 2003

A modified method with respect to an earlier conventional procedure was successfully attempted an... more A modified method with respect to an earlier conventional procedure was successfully attempted and we now report the new procedure for the synthesis of surface-grafting technique by the delayed addition of inexpensive vinyltoluene (VT) functionality to the partially polymerized supporting monomers viz., styrene (St) and divinylbenzene (DVB) via suspension polymerization. The resulting copolymer beads containing surface-enriched with methyl group were converted into a catalyst by chlorination followed by a quaternization process. Two groups (I and II) of SE-PSPTC beads were prepared by fixing the crosslinking amount (DVB) as 2% and 6%, respectively, 25% of VT as a common active site functionality and the rest of the contribution was styrene. Each group contains six different catalysts based on the concentration of active sites on the surface which in turn depends upon the partial polymerization time (PPT) of St/DVB i.e., 0, 3, 6, 9, 12, and 15 hrs. These two different groups and 6 different catalysts categories in each were prepared with the objective to learn the influence of higher/lower crosslinking in the process of surface-grafting of poly(VT) on poly(St/DVB) and to determine the optimized partial polymerization time to bring the maximum active site on the surface. The level of enrichment of an active site of all the catalysts were determined through [chloride], FT-IR, SEM, EDAX, and ESCA analyses. The gradual increase of [chloride], C-N peak intensity from FT-IR, rough surface/nodules concentration from SEM, % of surface chloride from EDAX, decreasing/increase trend of surface carbon/surface chloride in ESCA analyses starting with 0 VT to 15 VT irrespective groups, confirms the gradual increase of active site on the surface beads based on the PPT. The results of [chloride], spectral analyses and the rate constants of all the catalysts in dichlorocarbene addition to various olefines ensure that 9 VT-SE-PSPTC was the best catalyst beads in both the groups due to its two-fold enhancement rather than the conventional catalyst (0 VT) of both groups although we had added the same amount of VT in both preparations.

Research paper thumbnail of Effective functionalization of multiwalled carbon nanotube with amphiphilic poly(propyleneimine) dendrimer carrying silver nanoparticles for better dispersability and antimicrobial activity

Journal of Colloid and Interface Science, 2011

Two multiwalled carbon nanotube hybrids have been prepared: (a) multiwalled carbon nanotubes (MWC... more Two multiwalled carbon nanotube hybrids have been prepared: (a) multiwalled carbon nanotubes (MWCNTs) functionalized with amphiphilic poly(propyleneimine) dendrimer (APPI), viz. MWCNTs-APPI, and (b) silver nanoparticles (AgNPs)-deposited multiwalled carbon nanotubes functionalized with an amphiphilic poly(propyleneimine) dendrimer (MWCNTs-APPI-AgNPs). The degree of covalent functionalization of APPI in MWCNTs and deposition of AgNPs in MWCNTs-APPI were examined by Fourier transform infrared spectroscopy, zeta potential, scanning and high-resolution transmission electron microscopy, energy-dispersive spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The amount of APPI functionalized on MWCNTs determined by thermal gravimetric analysis was about 67% which enables an effective dispersability in aqueous and organic solvents without sonication and these solutions were stable for 6 months without undergoing aggregation of MWCNTs. The electronic properties of the hybrid materials were not altered drastically as verified by the Raman studies. The antimicrobial activities of MWCNTs-APPI and MWCNTs-APPI-AgNPs against three different bacteria, viz. Bacillus subtilis, Staphylococcus aureus, and Escheriachia coli illustrated excellent activity.

Research paper thumbnail of Modification of glassy carbon electrode with trigona carbon nanopetals/ferrocene/gold nanoparticles nanocomposite for electrochemical detection of dopamine

Indian Journal of Chemistry -Section A

In this study, we have synthesized a composite using carbon material derived from bio-inspired on... more In this study, we have synthesized a composite using carbon material derived from bio-inspired onion peel morphology like 2D trigona carbon nano petals (TCP) incorporated with ferrocene (FC). The FC is added with the purpose of improving the electrochemical behaviour of TCP. Further, to increase the number of electrochemically active sites in the composite, gold nanoparticles (AuNPs) were again decorated on TCP/FC, and thus derived electrochemically active TCP/FC/AuNPs nanocomposite. We have characterized the properties and surface morphology of this nanocomposite through spectroscopic and microscopic techniques. Further, using this nanocomposite for surface modification of glassy carbon electrode, we have developed an efficient GCE-TCP/FC/AuNPs electrode. The electrochemical efficiency of this electrode has been inspected through sensing and quantification of pharmaceutically valuable biomolecule dopamine through CV, DPV and square wave voltammetry techniques. The observed CV results reveals that the newly designed GCE-TCP/FC/AuNPs electrode has an ability to detect the dopamine with wide linear range of concentration from 5.96 × 10-6 to 0.1 × 10-4 M and its limit of detection was 2.9 × 10-6 M under 0.1 M phosphate buffer medium (pH 7.0). Therefore, it is important to mention here that this newly fabricated electrode can very well be used for real time sample analysis for sensing and detection of dopamine as it plays a key role in the neurotransmission and causes several diseases.

Research paper thumbnail of Facile synthesis of core-shell nanocomposites Au catalysts towards abatement of environmental pollutant Rhodamine B

Heliyon, 2019

Magnetically recoverable Au nanoparticles immobilized/stabilized on core-shell nanocomposites are... more Magnetically recoverable Au nanoparticles immobilized/stabilized on core-shell nanocomposites are synthesized by the combination of suspension polymerization as well as surface initiator atom transfer radical polymerization (SI-ATRP) methods. The magnetic core-shell supported Au nanocatalysts are namely Fe 3 O 4-PAC-AuNPs, Fe 3 O 4-PVBC-g-PAC-AuNPs, Fe 3 O 4-HEA-AuNPs, and Fe 3 O 4-PVBC-g-HEA-AuNPs. Among all the catalysts, Fe 3 O 4-PVBC-g-PAC-Au NPs exhibited an excellent activity in the reduction of Rhodamine B with an apparent rate constant of 10.77 Â 10 À3 s À1 and TOF value of 47.62 Â 10 À3 s À1 under pseudo-first order reaction condition. Further, Fe 3 O 4-PVBC-g-PAC-Au NPs has an outstanding activity and recyclability without applying any external magnetic field. This new approach provides an exciting potential way in the preparation of recyclable metal nano-catalysts with high catalytic activity.

Research paper thumbnail of Fabrication of GC-r-GO-PAMAM (G3)-Pd electrode for electro-catalytic oxidation of formic acid

Advanced Materials Proceedings, 2018

Graphene functionalized with Poly(amidoamine) dendrimer stabilized PdNPs (r-GO-PAMAM-Pd) composit... more Graphene functionalized with Poly(amidoamine) dendrimer stabilized PdNPs (r-GO-PAMAM-Pd) composite was prepared through facile experimental routes and characterized by FT-IR, XRD, Raman, SEM and EDAX techniques. Initially, poly(amidoamine) generation 3 (PAMAM (G3)) dendrimer was functionalized on graphene oxide (GO) and the resulting matrix was loaded with PdNPs through stabilization and thus produced excellent conducting composite material. The electrocatalytic activity of this composite was inspected by coating on bare GCE and thus produced stable and efficient GC-r-GO-PAMAM (G3)-Pd electrode and this in turn demonstrated for the oxidation of formic acid (FA). The occurrence of the oxidation reaction was monitored by cyclic voltammetric (CV) and linear sweep voltammetric (LSV) techniques in 0.5 M H2SO4 medium at the potential window of-0.3 to 1.0 V vs. Ag/AgCl, v = 50 mVs-1. The observed peak potential for the new electrode was located at 0.15V and compared with existing electrodes derived from different GO/Pd composites. The comparative results reveals that the newly designed electrode shown an excellent catalytic activity, more resistant to the surface poisoning and the anodic onset potential was more negative than the reported electrodes. This improved electrocatalytic performance are due to the contribution of synergetic effect of GO, dendrimer and PdNPs.

Research paper thumbnail of Effective Sidewall Functionalization of Multiwalled Carbon Nanotubes with Dichlorocarbene Addition using New Soluble Multi-site Phase Transfer Catalysts

The novel soluble multi-site phase transfer catalysts (MPTCs), viz., 2,6-bis (triethylammoniummet... more The novel soluble multi-site phase transfer catalysts (MPTCs), viz., 2,6-bis (triethylammoniummethylene chloride)-4-methoxytoluene (BTEACM) and 3,3’,5,5’-tetrakis (dimethylaminopyridinium chloride) biphenyl (TDMAPCB) containing two, and four active sites was synthesized, and characterized through Fourier transform infra red spectroscopy (FTIR), proton nuclear magnetic spectroscopy, carbon nuclear magnetic spectroscopy, thermo gravimetric analysis (TGA) and energy dispersive spectroscopy (EDS) analyses. The obtained MPTCs were used as a catalysts for sidewall functionalization of multiwalled carbon nanotubes (MWCNTs) in dichlorocarbene (CCl 2 ) addition, and compared their functionalization yield with commercially available single site PTC and tri-site PTC viz., benzyltriethylammonium chloride (BTEAC) and 2,4,6-tris (triethylammoniummethylene chloride) mesitylene (TTEAMCM). The functionalization of CCl 2 on MWCNTs was established by the appearance of increased peak intensity of C-Cl ...

Research paper thumbnail of Triphase catalysis synthesis and characterization of surface enriched polymer supported phase transfer catalysts and their application in some organic addition reactions a kinetic study

Research paper thumbnail of Preparation of surface-enriched polymersupported phase transfer catalysts and kinetics of dichlorocarbene addition to cycylohexene using 50 % NaOH

Indian journal of chemistry. Sect. A: Inorganic, physical, theoretical & analytical, 1997

Research paper thumbnail of Phase Transfer Catalysis:Effect of Cationic Surfactants on the Free Radical Polymerization of Methylmethacrylate

The effect of cationic surfactants, decyltrimethylammonium bromide (DTAB), dodecyltrimethylammoni... more The effect of cationic surfactants, decyltrimethylammonium bromide (DTAB), dodecyltrimethylammonium bromide (DDTAB) and tetradecyltrimethylammonium bromide (TDTAB), has been studied as phase transfer catalysts (PTCs) on the free radical polymerization of methylmethacrylate (MMA) using potassium peroxydisulfate (PDS, K 2 S 2 O 8 ) in toluene-water biphase system. Of the three PTCs in their respective critical micellar concentration (CMC) and in common concentration, the TDTAB show comparatively high rate of polymerization (Rp), 7.76 × 10 -5 mol.L -1 .S -1 , at the lowest reaction time of 30 min in its concentration of 2 × 10 -2 mol.L -1 . Detailed kinetic study of polymerization of MMA has been carried out using TDTAB at a fixed time of 30 min by varying [MMA], [K 2 S 2 O 8 ], [TDTAB] and temperature. Based on the kinetic results, the free energy of activation has been calculated, and a suitable mechanism and rate law has been proposed.

Research paper thumbnail of New Polymer-Supported Multi-Site Phase Transfer Catalyst in Dichlorocarbene Addition to Styrene

Research paper thumbnail of Synthesis, characterization, and catalytic activity for hybrids of multi-walled carbon nanotube and amphiphilic poly(propyleneimine) dendrimer immobilized with silver and palladium nanoparticle

Four types of new multi-walled carbon nanotube (MWCNT) based nanohybrid catalysts were prepared t... more Four types of new multi-walled carbon nanotube (MWCNT) based nanohybrid catalysts were prepared through simple methods. Initially, MWCNT was functionalized with carboxyl group and subsequently bonded with amphiphilic poly(propyleneimine) dendrimer (APPI) having generation (G2) and (G3). They are abbreviated as MWCNT-APPI (G2) and MWCNT-APPI (G3). Silver nanoparticles (AgNPs) and palladium nanoparticles (PdNPs) were separately immobilized to each hybrid to obtain four types of MWCNT based nanohybrid catalysts. The pseudo-first order rate constants for reduction of 4-nitrophenol revealed that among the four types of MWCNT nanohybrid catalysts, MWCNT-APPI (G3)-PdNPs was more efficient than the other catalysts with five-fold higher efficiency than the homogeneous PPI (G3)-PdNPs. For the same reaction with MWCNTs-APPI (G3)-PdNPs catalyst, the variation of [catalyst] and [NaBH4] was directly proportional to kobs. The study of reusability of MWCNT-APPI (G3)-PdNPs proved no loss in activity...

Research paper thumbnail of Separate and simultaneous determination of vanillin, theophylline and caffeine using molybdenum disulfide embedded polyaniline/graphitic carbon nitrite nanocomposite modified glassy carbon electrode

Diamond and Related Materials

Research paper thumbnail of Rationally designed SERS AgNPs/GO/g-CN nanohybrids to detect methylene blue and Hg2+ ions in aqueous solution

Research paper thumbnail of Silver nanoparticles decorated g-C3N4: An efficient SERS substrate for monitoring catalytic reduction and selective Hg2+ions detection

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy

Research paper thumbnail of Highly sensitive, stable g-CN decorated with AgNPs for SERS sensing of toluidine blue and catalytic reduction of crystal violet

Journal of Materials Science

SERS substrates with high sensitivity, SERS enhancement and stability are essential for fabricati... more SERS substrates with high sensitivity, SERS enhancement and stability are essential for fabrication of SERS sensors to detect dyes at low concentration. Such substrates generally have a versatile support bonded to metal nanoparticles of optimum size. Simple methodology that yields SERS substrates with reproducible results is mostly desired for sensor fabrication. In this study, silver ions were reduced with safe reducing agent NaBH4 to Ag metal nanoparticles (AgNPs) in the presence of previously prepared g-CN to obtain g-CN decorated with silver nanoparticles (AgNPs@g-CN) of average diameter 22 nm. The results of XPS and UV–Vis spectroscopy unambiguously establish significant interaction between the nitrogen sites of g-CN and AgNPs. The AgNPs@g-CN yielded very high SERS enhancement for toluidine blue at very low concentration (2.5 × 10−09 M), and the SERS results are reproducible. The surface enhancement factor (EF) is one of the important criteria to evaluate and compare SERS materials, and it was equal to 9.13 × 106 toward toluidine blue. The catalytic activity of the substrate for the reduction of crystal violet (CV) to its leuco-form was tested with NABH4. The reaction was monitored by UV Vis spectroscopy. There was a rapid fall in intensity of CV. The reduction of CV mainly occurred via electron transfer from AgNPs, and the product did not interfere with the absorbance of CV. Hence, AgNPs@g-CN could be a convenient choice for fabrication of commercial SERS sensors for detection of dyes at low concentrations. It is also useful as a catalyst for the reduction of organic dyes.

Research paper thumbnail of Amphiphilic Dendrimer Stabilized Ag, Pd And Pt Homogeneous Nanoparticle Catalysts And Their Catalysis For The Reduction Of Methyl Orange

Two different amphiphilic poly(propyleneimine) dendrimers (APPI-G2-(N+Cl-)x) were synthesized by ... more Two different amphiphilic poly(propyleneimine) dendrimers (APPI-G2-(N+Cl-)x) were synthesized by reductive methylation of poly(propyleneimine) dendrimer with HCOOH/HCHO and thus yield methylated dendrimer having eight dimethyl amino end groups. This in turn was converted into amphiphilic form via quaternization with 1-bromooctane. By varying the mole ratio of alkyl bromide to dendrimer, averages of 5&10 quaternary ammonium groups were generated individually. The prepared amphiphilic dendrimer templates were used individually and stabilized the Ag, Pd and PtNPs. The resultant homogeneous nanoparticle catalysts were characterized with UV-Vis, FESEM and EDS techniques. The catalytic activity of the APPI-G2-(N+Cl-)x -NPs were examined through reduction of methyl orange under pseudo-first order condition at ambient temperature. The catalytic efficiency of these catalysts were found in the order of APPI-G2-(N+Cl-)5 -PdNPs > APPI-G2-(N+Cl-)5 –AgNPs > APPI-G2-(N+Cl-)5 –PtNPs.

Research paper thumbnail of A novel Steroid from Elephantopus scaber L. an Ethnomedicinal plant with antidiabetic activity

Phytomedicine, 2009

Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels ... more Acetone extract of Elephantopus scaber, an ethnomedicnal plant, reduced the blood glucose levels in streptozotocininduced diabetic rats significantly. Acute toxicity studies revealed the non-toxic nature of the crude extract. Fractionation of the acetone extract yielded a new steroid, 28Nor-22(R)Witha 2,6,23-trienolide. Biological testing of the compound demonstrated a significant antidiabetic activity by reducing the elevated blood glucose levels and restoring the insulin levels in streptozotocin-induced diabetic rats. This compound can be a useful candidate to treat diabetes.

Research paper thumbnail of Catalysis by Hydrophobically Modified Poly(propylenimine) Dendrimers Having Quaternary Ammonium and Tertiary Amine Functionality

Langmuir, 2004

Four different quaternary ammonium chloride-modified poly(propylenimine) (PPI) dendrimers were sy... more Four different quaternary ammonium chloride-modified poly(propylenimine) (PPI) dendrimers were synthesized by alkylation of a PPI dendrimer having eight dimethylamino end groups with 1-bromooctane or 1-bromododecane. By varying the mole ratio of alkyl bromide to dendrimer, averages of 4-10 quaternary ammonium groups were formed. The new amphiphilic dendrimers are surface active and are micellar catalysts in water. The dendrimers have critical aggregation concentrations between 8.5 x 10(-4) and 9.0 x 10(-5) M. Decarboxylation of 6-nitrobenzisoxazole-3-carboxylate at 25 degrees C was 650 times faster than in water alone in the presence of a dendrimer quaternized with eight dodecyl chains at a concentration of 2.45 mM in quaternary ammonium groups. The order of the catalytic efficiency of the new dendrimers decreased with the length and number of hydrophobic alkyl groups in the order (C(12))(8) > (C(12))(4) > (C(8))(10) > (C(8))(5). The pseudo-first-order rate constants for basic hydrolysis of p-nitrophenyl hexanoate in pH 9.4 buffer at 30 degrees C using the (C(12))(8) and (C(12))(4) dendrimers were 26 and 13 times higher than those for hydrolysis with no dendrimer. The kinetic data were fit to a single-site binding model to evaluate the contributions of binding constants of reactants to the dendrimers and catalytic rate constants of the bound species to the overall catalytic activity.

Research paper thumbnail of Preparation and spectroscopic characterization of surface-enriched (with active sites) polymer-supported phase-transfer catalysts and their efficiency in organic addition reactions: A kinetic study

Journal of Polymer Science Part A: Polymer Chemistry, 2003

Research paper thumbnail of Preparation of a novel soluble multi-site phase transfer catalyst and the kinetic study for the C-alkylation of α-pinene

Journal of Molecular Catalysis A: Chemical, 2005

Novel soluble “multi-site” phase transfer catalyst viz.1,3,5-tris(4-(2,2′-bis(N-triethylammoniumm... more Novel soluble “multi-site” phase transfer catalyst viz.1,3,5-tris(4-(2,2′-bis(N-triethylammoniummethylene chloride)eth-1-ene)phenoxymethyl)benzene (TBTEAPB) was synthesized and characterized by different spectral techniques such as FT-IR, 1H NMR, 13C NMR, MALDI-TOF mass and chloride ion analysis. The catalytic potential of this new multi-site TBTEAPB phase transfer catalyst was demonstrated by the C-alkylation of α-pinene with epichlorohydrin using low concentration of base (20% NaOH) at 40°C. The

Research paper thumbnail of A Modified Method for the Synthesis and Characterization of a Novel Surface-Enriched (with Active Site) Polymer-Supported Phase Transfer Catalyst Using Vinyltoluene as a Functionality and Its Catalytic Efficiency in Dichlorocarbene Addition to Olefines—A Kinetic Study

Journal of Macromolecular Science, Part A, 2003

A modified method with respect to an earlier conventional procedure was successfully attempted an... more A modified method with respect to an earlier conventional procedure was successfully attempted and we now report the new procedure for the synthesis of surface-grafting technique by the delayed addition of inexpensive vinyltoluene (VT) functionality to the partially polymerized supporting monomers viz., styrene (St) and divinylbenzene (DVB) via suspension polymerization. The resulting copolymer beads containing surface-enriched with methyl group were converted into a catalyst by chlorination followed by a quaternization process. Two groups (I and II) of SE-PSPTC beads were prepared by fixing the crosslinking amount (DVB) as 2% and 6%, respectively, 25% of VT as a common active site functionality and the rest of the contribution was styrene. Each group contains six different catalysts based on the concentration of active sites on the surface which in turn depends upon the partial polymerization time (PPT) of St/DVB i.e., 0, 3, 6, 9, 12, and 15 hrs. These two different groups and 6 different catalysts categories in each were prepared with the objective to learn the influence of higher/lower crosslinking in the process of surface-grafting of poly(VT) on poly(St/DVB) and to determine the optimized partial polymerization time to bring the maximum active site on the surface. The level of enrichment of an active site of all the catalysts were determined through [chloride], FT-IR, SEM, EDAX, and ESCA analyses. The gradual increase of [chloride], C-N peak intensity from FT-IR, rough surface/nodules concentration from SEM, % of surface chloride from EDAX, decreasing/increase trend of surface carbon/surface chloride in ESCA analyses starting with 0 VT to 15 VT irrespective groups, confirms the gradual increase of active site on the surface beads based on the PPT. The results of [chloride], spectral analyses and the rate constants of all the catalysts in dichlorocarbene addition to various olefines ensure that 9 VT-SE-PSPTC was the best catalyst beads in both the groups due to its two-fold enhancement rather than the conventional catalyst (0 VT) of both groups although we had added the same amount of VT in both preparations.

Research paper thumbnail of Effective functionalization of multiwalled carbon nanotube with amphiphilic poly(propyleneimine) dendrimer carrying silver nanoparticles for better dispersability and antimicrobial activity

Journal of Colloid and Interface Science, 2011

Two multiwalled carbon nanotube hybrids have been prepared: (a) multiwalled carbon nanotubes (MWC... more Two multiwalled carbon nanotube hybrids have been prepared: (a) multiwalled carbon nanotubes (MWCNTs) functionalized with amphiphilic poly(propyleneimine) dendrimer (APPI), viz. MWCNTs-APPI, and (b) silver nanoparticles (AgNPs)-deposited multiwalled carbon nanotubes functionalized with an amphiphilic poly(propyleneimine) dendrimer (MWCNTs-APPI-AgNPs). The degree of covalent functionalization of APPI in MWCNTs and deposition of AgNPs in MWCNTs-APPI were examined by Fourier transform infrared spectroscopy, zeta potential, scanning and high-resolution transmission electron microscopy, energy-dispersive spectroscopy, thermogravimetric analysis, and Raman spectroscopy. The amount of APPI functionalized on MWCNTs determined by thermal gravimetric analysis was about 67% which enables an effective dispersability in aqueous and organic solvents without sonication and these solutions were stable for 6 months without undergoing aggregation of MWCNTs. The electronic properties of the hybrid materials were not altered drastically as verified by the Raman studies. The antimicrobial activities of MWCNTs-APPI and MWCNTs-APPI-AgNPs against three different bacteria, viz. Bacillus subtilis, Staphylococcus aureus, and Escheriachia coli illustrated excellent activity.