Browsing by Author "Rupali Gupta"

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Amperometric assay of hydrazine utilizing electro-deposited cobalt hexacyanoferrate nanocrystals on graphene oxide sheets
(Springer, 2020) Mamta Yadav; Vellaichamy Ganesan; Rupali Gupta; Dharmendra Kumar Yadav; Piyush Kumar Sonkar
Abstract: In-situ electrochemical deposition of cobalt hexacyanoferrate (CoHCF) on graphene oxide (GO) and its application for the electrocatalytic hydrazine determination in real samples are described in this research study. Co2+ is immobilized on GO and the resulting material, GO-Co2+ is coated on the surface of glassy carbon (GC) electrode. The fabricated electrode (GC/GO-Co2+) is subjected to a continuous potential cycling in the range of 0.0–1.0 V which results in the formation of a thin CoHCF film on the surface of GO coated on the GC electrode (abbreviated as GC/GO-CoHCF). The synthesized GO-CoHCF composite material is characterized by Fourier transform infrared and scanning electron microscopy. GC/GO-CoHCF electrode electrocatalytically oxidizes hydrazine at low overpotential (0.63 V) and this phenomenon is subsequently utilized for the sensitive determination of hydrazine in aqueous solutions. It exhibits a wide linear calibration range (0.1–400 µM), high sensitivity (0.93 µA µM−1 cm−2) and low limit of detection (17.5 nM) for the determination of hydrazine. Further, this electrode is employed for hydrazine determination in real samples. Graphic abstract: [Figure not available: see fulltext.] © 2020, Indian Academy of Sciences.
Benzimidazole based mesogenic Schiff-bases: Synthesis and characterization
(Elsevier B.V., 2017) Ragini Dubey; Rajasekhar Yerrasani; M. Karunakar; Angad Kumar Singh; Rupali Gupta; Vellaichamy Ganesan; T.R. Rao
Two homologous series of mesogenic Schiff-bases, N-4-((alkoxy)-(phenyl-3-hydroxy-4-(4-(5-methylbenzimidazol))-2-alkoxysalicylaldimine)benzoate (7a–d) and N-4′-(5-methyl-benzimidazole)-phenyl-4-alkoxysalicylaldimine (8a–d) incorporating benzimidazole moiety have been prepared and the molecular structures studied by FT-IR, NMR and ESI-MS spectrometry. Mesogenic behaviour was investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC) and variable temperature powder X-ray diffraction (PXRD) techniques. Changing the spacer (ester-linked to non-ester linked) of the Schiff-base results in enhancement of thermal stability and phase transition temperature. The members of series-I show monotropic SmA while those of series-II reflect enantiotropic SmA mesomorphism. An electrochemical study of a representative Schiff base in each series (7d and 8c) showed an electrical band gap 1.26 eV and 1.22 eV respectively. © 2017 Elsevier B.V.
Co(II)-porphyrin-decorated carbon nanotubes as catalysts for oxygen reduction reactions: An approach for fuel cell improvement
(Royal Society of Chemistry, 2017) Piyush Kumar Sonkar; Kamal Prakash; Mamta Yadav; Vellaichamy Ganesan; Muniappan Sankar; Rupali Gupta; Dharmendra Kumar Yadav
The development of high-performance and cost-effective catalysts for the oxygen reduction reaction (ORR) is essential for the advancement of fuel cells. In this work, three different functionalized cobalt porphyrins, meso-tetraphenylporphyrinatocobalt(ii) (CoTPP), meso-tetrakis(4′-hydroxyphenyl)porphyrinatocobalt(ii) (CoTHPP) and meso-tetrakis(4′-carboxy-phenyl)porphyrinatocobalt(ii) (CoTCPP), are prepared. These porphyrins are immobilized non-covalently on multiwalled carbon nanotubes (MWCNTs) and used for the ORR in 0.1 M HClO4, 0.1 M phosphate buffer solution (pH 7.0) and 0.1 M KOH media. The composite materials are characterized by using spectroscopic and electrochemical techniques and their oxygen reduction efficiencies are compared in different media. Kinetic interpretations and hydrodynamic voltammetry (in three media) studies demonstrated that the MWCNT-CoTPP, MWCNT-CoTHPP and MWCNT-CoTCPP composite materials exhibit significant efficiency with decreased overpotential, considerable methanol tolerance and long term operational stability (up to 3000 cycles) for the ORR similar to commercially available platinum carbon (Pt-C) catalysts. These results reveal that the new MWCNT-cobalt porphyrin composite materials can be a potential alternative to the expensive Pt-C catalysts or other commercial cathode materials in fuel cells. © 2017 The Royal Society of Chemistry.
Cobalt oxide nanocrystals anchored on graphene sheets for electrochemical determination of chloramphenicol
(Elsevier Inc., 2019) Mamta Yadav; Vellaichamy Ganesan; Rupali Gupta; Dharmendra Kumar Yadav; Piyush Kumar Sonkar
This study demonstrates the hydrothermal synthesis of cobalt oxide (Co 3 O 4 ) nanocrystals on reduced graphene oxide (rGO) which is further utilized to construct an electrochemical sensing scaffold for precise determination of chloramphenicol (CP). CP is an antibiotic used for the treatment of typhoid fever and infections including salmonellosis. Due to its antibacterial property, low cost and availability it was extensively used in the fields of agriculture, but its presence in animal derived food products create detrimental effects on consumers. Therefore it is important to monitor the level of CP in different food products. The formation of Co 3 O 4 on rGO (Co 3 O 4 @rGO) is characterized with FT-IR, XRD, TEM and SEM techniques. The working electrode is fabricated by drop coating the catalyst (0.1% Co 3 O 4 @rGO in DMF) on glassy carbon (GC) electrode (symbolized as GC/Co 3 O 4 @rGO) and further used for electrochemical sensing of CP with cyclic voltammetry (CV), amperometry and differential pulse voltammetry (DPV) techniques. The calibration curve for the determination of CP through CV shows a linear range from 1 to 2000 μM with two different slopes. Sensitivity of the CP determination and limit of detection (LOD) are calculated to be 1.32 μA μM cm −2 and 0.55 μM, respectively. Further the sensing scaffold, GC/Co 3 O 4 @rGO is successfully applied for the CP determination present in real samples like milk products. © 2019 Elsevier B.V.
Copper oxide immobilized clay nano architectures as an efficient electrochemical sensing platform for hydrogen peroxide
(Springer, 2020) Dharmendra Kumar Yadav; Vellaichamy Ganesan; Rupali Gupta; Mamta Yadav; Piyush Kumar Sonkar; Pankaj Kumar Rastogi
Abstract: An electrochemical sensor for hydrogen peroxide (H2O2) present in face bleach cream is fabricated using a composite based on bentonite (Bt) clay and copper oxide(CuO) nanoparticles (CuO-Bt). The CuO nanoparticles’ immobilization into Bt was carried out by a two-step process in which Cu2+ is ion-exchanged into Bt layers (Cu2+-Bt) in the first step followed by the chemical reaction of NaOH with Cu2+-Bt in the second step to get the target material, CuO nanoparticles immobilized Bt (CuO-Bt). The successful immobilization of CuO nanoparticles into Bt is investigated by a variety of techniques like scanning electron microscopy, transmission electron microscopy, FT-IR spectroscopy, UV-Vis spectroscopy, and electrochemical methods. The CuO-Bt composite is coated on a glassy carbon electrode and used as a selective electrochemical sensing platform for the determination of H2O2 based on the significant electrocatalytic property of CuO-Bt towards the H2O2 oxidation. This amperometric electrochemical sensor shows two linear detection ranges (5–50 μM and 50–10000 μM) with a limit of detection of 4.9 μM. The sensitivity is calculated to be 0.06 µA µM−1 cm−2. This electrochemical sensor exhibits high selectivity, stability, and practical applicability for the H2O2 determination in real samples. Graphic Abstract: [Figure not available: see fulltext.]. © 2020, Indian Academy of Sciences.
Dual Electrocatalytic Behavior of Oxovanadium(IV) Salen Immobilized Carbon Materials Towards Cysteine Oxidation and Cystine Reduction: Graphene Versus Single Walled Carbon Nanotubes
(Wiley-Blackwell, 2016) Piyush K. Sonkar; Vellaichamy Ganesan; Dharmendra K. Yadav; Rupali Gupta
Oxovanadium(IV) salen (VO(salen)) (where salen=N,N’-bis(salicylidene)ethylenediamine) is embedded onto reduced graphene oxide (rGO) and single walled carbon nanotubes (SWCNTs). The resulting materials, VO(salen) embedded rGO (rGO-VO(salen)) and VO(salen) embedded SWCNTs (SWCNTs-VO(salen)) show remarkable electrocatalytic activity for cysteine oxidation and cystine (the oxidized product of cysteine) reduction as demonstrated by cyclic voltammetry (CV). The materials, rGO-VO(salen) and SWCNTs-VO(salen) are characterized through spectroscopic and microscopic techniques. Transmission electron microscopy exhibits nanocrystalline view of VO(salen) on rGO-VO(salen) while it appears like aggregated nodules in the SWCNTs-VO(salen) revealing the nano-structures excellently. Electrochemical cysteine oxidation is studied using rGO-VO(salen) coated glassy carbon (GC) electrode (GC/rGO-VO(salen)) and SWCNTs-VO(salen) coated GC electrode (GC/SWCNTs-VO(salen)). The efficiency of the catalytic platforms is compared. Overall number of electrons and electron transfer rate constant are obtained using rotating disc electrode for cysteine oxidation at GC/rGO-VO(salen) and GC/SWCNTs-VO(salen). Calibration curves for the determination of cysteine at GC/rGO-VO(salen) and GC/SWCNTs-VO(salen) exhibit linear range from 1.0 μM to 5.0 mM and 1.0 μM to 4.0 mM, respectively. GC/rGO-VO(salen) and GC/SWCNTs-VO(salen) are successfully applied for the real samples analysis with remarkable recovery. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Effect of structural modifications on the oxygen reduction reaction properties of metal-organic framework-based catalysts
(Elsevier, 2022) Dharmendra Kumar Yadav; Rupali Gupta; Vellaichamy Ganesan; Ramasamy Ramaraj
In the present era, technological advancements are significantly progressed due to the rapid depletion of traditional energy resources. These energy resources are anticipated to be drained out due to their limited availability and nonrenewable nature in the near future. Therefore, intense research has to be carried out to explore alternative energy resources. A judicious solution to this menace is the exploitation of alternative energy sources which have minimum hazards to the environment. A very impactful method could be the use of electrochemical energy conversion systems such as fuel cells, metal-air batteries, etc. For these electrochemical energy conversion systems, oxygen reduction reaction (ORR) is the essential half-cell reaction that takes place at the cathode. However, the major hindrance which results in slow kinetics of the ORR is the conversion of O-O bond to O-H bond which requires high activation energy. Such a high energy barrier associated with this conversion limits its efficiency and conversion rates. Additionally, the high cost and mediocre durability of precious-metal-based catalysts such as platinum which made a benchmark for ORR put a limit on their commercial application. Therefore, it becomes very much essential to design and implement efficient and cost-effective electrocatalysts which can facilitate this conversion by alleviating the energy barrier. In the recent past, a unique class of functional material, known as metal-organic frameworks (MOFs) and their derivatives has gained limelight among the researchers worldwide, on account of its prominent efficiency as electrocatalysts for various electrochemical processes. MOFs are composed of metal ions or clusters bridged by organic linker molecules. The periodic structural design offers them a crystalline nature with high surface area and porosity. Meanwhile, on account of the hybrid nature of the structural components (i.e., organic as well as inorganic), MOFs display tailorable pore size and chemical environment rendering them variable physical and chemical properties. The porous nature of these MOFs results in the rapid diffusion of substrates through them thereby enhancing the number of active sites for the catalytic process. As the metal ion/cluster sites are isolated in the MOFs, they are analogical to the molecular catalysts. The structural design offers stability and robustness to the MOFs. Moreover, a careful approach toward structural and functional modification paves new ways of their utility for a large number of applications. Despite all these advantages, MOFs suffer from serious drawbacks of poor electrical conductivity and stability which hinders their utility as electrocatalysts for ORR. However, these shortcomings can be overcome by integrating these MOFs with highly conductive, advanced materials such as graphene, metal nanoparticles, nanocarbons, carbon nanotubes which results in the formation of MOF-based composites with improved electrical conductivity and stability. Additionally, thermal treatment methods like carbonization and pyrolysis can also be employed to convert MOFs and their composites to inorganic derivatives which find their applicability as ORR electrocatalyst on account of their superior conductivity and improved stability. Here, in this chapter, the ORR process and the role of MOFs as electrocatalysts for the ORR are described. In addition, different processes employed for the structural modifications of MOF and their successful utilization as the electrocatalysts for the ORR process are also described. © 2022 Elsevier Inc. All rights reserved.
Electrochemical investigation of gold nanoparticles incorporated zinc based metal-organic framework for selective recognition of nitrite and nitrobenzene
(Elsevier Ltd, 2016) Dharmendra Kumar Yadav; Vellaichamy Ganesan; Piyush Kumar Sonkar; Rupali Gupta; Pankaj Kumar Rastogi
An electrochemical sensing platform which comprises gold nanoparticles (Au NPs) incorporated zinc based metal-organic framework (MOF-5) is developed for the sensitive determination of nitrite and nitrobenzene. MOF-5 and Au NPs incorporated MOF-5 (Au-MOF-5) are synthesized and characterized by UV-vis absorption, powder X-ray diffraction, FT-IR, scanning electron microscopy with energy dispersive X-ray analysis and elemental mapping, transmission electron microscopy and atomic force microscopy. Oxidation of nitrite is effectively electrocatalyzed at Au-MOF-5 with significant increase in oxidation current (41 and 38% in comparison with bare glassy carbon (GC) and MOF-5 coated GC (GC/MOF-5) electrodes, respectively) and with considerable decrease in the oxidation potential (0. 17 and 0.25 V in comparison with bare GC and GC/MOF-5 electrodes, respectively). The electrocatalytic reduction of nitrobenzene at GC/Au-MOF-5 is confirmed by an appreciable increase in the reduction current (79 and 36% in comparison with bare GC and GC/MOF-5 electrodes, respectively) and a small shift in the reduction potential (20 mV in comparison with GC/MOF-5). The detection limit is calculated as 1.0 μM with a sensitivity of 0.23 μAμM-1 cm-2 for nitrite and 15.3 μM with a sensitivity of 0.43 μAμM-1cm-2 for nitrobenzene determinations. The Au-MOF-5 based electrochemical sensing platform shows high stability and selectivity even in the presence of several interferences (including phenols, inorganic ions and biologically important molecules) with a broad calibration range. Certain kinetic parameters of nitrite oxidation and nitrobenzene reduction have also been studied by hydrodynamic voltammetry. © 2016 Elsevier Ltd. All rights reserved.
Electrochemical sensing of rifampicin in pharmaceutical samples using meso-tetrakis(4-hydroxyphenyl)porphyrinato cobalt(II) anchored carbon nanotubes
(Springer Netherlands, 2018) Piyush Kumar Sonkar; Mamta Yadav; Kamal Prakash; Vellaichamy Ganesan; Muniappan Sankar; Dharmendra Kumar Yadav; Rupali Gupta
Abstract: In this work, an electrochemical sensing platform is prepared for rifampicin determination based on multiwalled carbon nanotubes (MWCNTs) modified with meso-tetrakis(4-hydroxyphenyl)porphyrinato cobalt(II) (CoTHPP) nanocomposite (abbreviated as MWCNTs-CoTHPP). The material is characterized by different techniques such as UV–Vis, Fourier transform-infrared, Raman, transmission electron microscopy, scanning electron microscopy, and energy dispersive X-ray analysis. For the electrochemical sensing platform, the nanocomposite, MWCNTs-CoTHPP is immobilized on glassy carbon (GC) electrode (represented as GC/MWCNTs-CoTHPP) and applied for electrochemical recognition of rifampicin. It is found that the GC/MWCNTs-CoTHPP electrode facilitates the electrochemical oxidation of rifampicin with decreased overpotential in 0.1 M acetate buffer (pH 4.7). Further, GC/MWCNTs-CoTHPP exhibits broad calibration range (0.01 µM–5.0 mM), high sensitivity (217 µA mM−1 cm−2), high reproducibility (relative standard deviation = 4.83%, n = 6), and low detection limit (0.008 µM) for rifampicin determination. In addition, this method is successfully applied for real sample (rifampicin capsule) analysis with consistent results. The results suggest that MWCNTs-CoTHPP is a potential candidate for an effective, rapid, and simple electrochemical sensor to detect rifampicin in pharmaceutical formulations. © 2018, Springer Nature B.V.
Electrochemical sensing platform for hydrogen peroxide determination at low reduction potential using silver nanoparticle-incorporated bentonite clay
(Springer Netherlands, 2016) Dharmendra Kumar Yadav; Rupali Gupta; Vellaichamy Ganesan; Piyush Kumar Sonkar; Pankaj Kumar Rastogi
Abstract: The electrocatalytic activity of silver nanoparticle-incorporated bentonite clay (Ag-Bt) for hydrogen peroxide (H2O2) reduction is investigated in 0.1 M pH 7.0 phosphate buffer solution. Ag-Bt material-coated glassy carbon (GC) electrode displays high electrocatalytic activity for H2O2 reduction with increased current response in comparison with GC/Bt electrode. The catalytic current increases linearly with incremental addition of H2O2 from 10 µM to 5.0 mM (based on the amperometric experiments at an applied potential −0.3 V). The apparent diffusion coefficient for H2O2 and catalytic rate constant for H2O2 reduction at the GC/Ag-Bt platform are calculated to be 2.3 × 10−5 cm2 s−1 and 2.20 × 104 M−1 s−1, respectively. The practical application using the Ag-Bt material is shown for the determination of H2O2 in real sample. The GC/Ag-Bt platform exhibits low detection limit (9.1 µM), high selectivity, reproducibility and stability. Graphical abstract: [Figure not available: see fulltext.] © 2015, Springer Science+Business Media Dordrecht.
Enhanced Four-Electron Selective Oxygen Reduction Reaction at Carbon-Nanotube-Supported Sulfonic-Acid-Functionalized Copper Phthalocyanine
(John Wiley and Sons Inc, 2023) Mamta Yadav; Devesh Kumar Singh; Dharmendra Kumar Yadav; Piyush Kumar Sonkar; Rupali Gupta; Vellaichamy Ganesan
In the present work, the oxygen reduction reaction (ORR) is explored in an acidic medium with two different catalytic supports (multi-walled carbon nanotubes (MWCNTs) and nitrogen-doped multi-walled carbon nanotubes (NMWCNTs)) and two different catalysts (copper phthalocyanine (CuPc) and sulfonic acid functionalized CuPc (CuPc-SO3−)). The composite, NMWCNTs-CuPc-SO3− exhibits high ORR activity (assessed based on the onset potential (0.57 V vs. reversible hydrogen electrode) and Tafel slope) in comparison to the other composites. Rotating ring disc electrode (RRDE) studies demonstrate a highly selective four-electron ORR (less than 2.5 % H2O2 formation) at the NMWCNTs-CuPc-SO3−. The synergistic effect of the catalyst support (NMWCNTs) and sulfonic acid functionalization of the catalyst (in CuPc-SO3−) increase the efficiency and selectivity of the ORR at the NMWCNTs-CuPc-SO3−. The catalyst activity of NMWCNTs-CuPc-SO3− has been compared with many reported materials and found to be better than several catalysts. NMWCNTs-CuPc-SO3− shows high tolerance for methanol and very small deviation in the onset potential (10 mV) between the linear sweep voltammetry responses recorded before and after 3000 cyclic voltammetry cycles, demonstrating exceptional durability. The high durability is attributed to the stabilization of CuPc-SO3− by the additional coordination with nitrogen (Cu-Nx) present on the surface of NMWCNTs. © 2023 Wiley-VCH GmbH.
Gold nanoparticles decorated mesoporous silica microspheres: A proficient electrochemical sensing scaffold for hydrazine and nitrobenzene
(Elsevier B.V., 2017) Rupali Gupta; Pankaj Kumar Rastogi; Vellaichamy Ganesan; Dharmendra Kumar Yadav; Piyush Kumar Sonkar
In this report, an electrochemical sensing scaffold (ESS) for hydrazine (HZ) and nitrobenzene (NB) have been developed based on gold nanoparticles decorated mesoporous silica microspheres (Au-MSM) modified glassy carbon (GC) electrode (represented as GC/Au-MSM). The presence and formation of gold nanoparticles in Au-MSM composite material is verified by X-ray diffraction, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, scanning electron microscopy, transmission electron microscopy and by electrochemical methods. The textural and thermal properties are studied by nitrogen adsorption-desorption and thermogravimetric analysis, respectively. The electrocatalytic sensing behavior of GC/Au-MSM towards HZ and NB are investigated in detail employing various electrochemical techniques. Amperometry measurements as a function of HZ concentration exhibit two linear calibration ranges of 5.0 μM to 0.5 mM and 0.5–18.0 mM. Similarly, the differential pulse voltammetry measurements as a function of NB concentration show a linear calibration range of 0.1 μM to 2.5 mM. The limit of detection is evaluated to be 0.11 μM and 15.0 nM for HZ and NB, respectively. The kinetic parameters for HZ oxidation and NB reduction are discussed using chronoamperometry. The proposed GC/Au-MSM ESS shows good selectivity over potent interferences and applied to determine HZ and NB in various water samples. © 2016 Elsevier B.V.
Gold nanoparticles impregnated mesoporous silica spheres for simultaneous and selective determination of uric acid and ascorbic acid
(Elsevier, 2015) Rupali Gupta; Vellaichamy Ganesan
This work reports the individual as well as simultaneous determination of ascorbic acid (AA) and uric acid (UA) by glassy carbon electrode (GCE) modified with a nanocomposite film of gold nanoparticles (Au NPs) inclusively adhered to MCM-41 type mesoporous silica spheres (Au-MSS). The impregnation of Au NPs into mesoporous silica spheres (MSS) is well established by surface characterization and electrochemical techniques. The Au-MSS modified GCE (GCE/Au-MSS) exhibits stable redox peaks, characteristics of Au NPs. Further, GCE/Au-MSS shows effective electrocatalytic oxidation of both AA and UA diminishing the overpotentials by 580 and 405 mV, respectively, than at bare GCE. Similarly, GCE/Au-MSS diminishes the oxidation overpotentials of AA and UA by 200 and 210 mV, respectively, relative to GCE/MSS. Differential pulse voltammetry technique is employed for the simultaneous determination of AA and UA in the presence of one another. The limit of detection is found to be 1.65 μM and 2.14 μM for AA and UA, respectively. The kinetic parameters like diffusion coefficient and the catalytic rate constant for the AA and UA electro-oxidations have been computed using chronoamperometric techniques. High sensitivity is displayed by the modified electrode and has been successfully employed for the analysis of UA in human blood serum. © 2015 Elsevier B.V. All rights reserved.
Gold Nanoparticles Incorporated in a Zinc-Based Metal-Organic Framework as Multifunctional Catalyst for the Oxygen Reduction and Hydrogen Evolution Reactions
(Wiley-VCH Verlag, 2018) Dharmendra K. Yadav; Rupali Gupta; Vellaichamy Ganesan; Piyush K. Sonkar; Mamta Yadav
Successful synthesis of gold nanoparticles incorporated in a zinc-based metal-organic framework (Au@Zn-MOF) is reported in this paper. The synthesis of Au@Zn-MOF is confirmed by UV-Vis, FT-IR and X-ray photoelectron spectroscopy (XPS) studies. The Au@Zn-MOF catalyst demonstrates electrocatalytic activity towards the oxygen reduction reaction (ORR) and the hydrogen evolution reaction (HER). The relative catalytic performance of Au@Zn-MOF towards ORR and HER has been studied under acidic condition. ORR proceeds via a two electron and two proton mechanism with hydrogen peroxide as the end product, while HER follows the Volmer mechanism i. e., adsorption of H+ on the catalyst's active sites. Au@Zn-MOF exhibits an ORR onset potential of 0.45 V (vs. RHE) with two different Tafel slopes, −93 and −103.6 mV in acidic solution. Further, an excellent catalytic activity is observed for HER with an onset potential of 0.02 V (vs. RHE) and a Tafel slope of 87 mV in N2 saturated 0.1 M HClO4 solution. However, in O2 saturated 0.1 M HClO4 solution, a HER onset potential of 0.04 V (vs. RHE) is observed with two different Tafel slopes, 610 and 220 mV. The value of Tafel slopes in the presence of O2 advocates the diminution of the ORR activity because of the HER. Thus, Tafel slope values of HER and ORR suggest that protons and O2 compete to reach the electrode surface for getting reduced. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Highly dispersed multiwalled carbon nanotubes coupled manganese salen nanostructure for simultaneous electrochemical sensing of vitamin B2 and B6
(Elsevier B.V., 2017) Piyush Kumar Sonkar; Vellaichamy Ganesan; Susanta K. Sen Gupta; Dharmendra Kumar Yadav; Rupali Gupta; Mamta Yadav
A nanocomposite of Mn(salen)Cl (where salen is N,N′-bis(salicylidene)ethylenediamine) and multiwalled carbon nanotubes (MWCNTs) is prepared. The advantageous properties of MWCNTs and catalytic properties of Mn(salen)Cl (represented as MnIIIsalen) are combined in this new nanocomposite (represented as MWCNTs-MnIIIsalen). Several techniques including electrochemical ones are used for the characterization of the MWCNTs-MnIIIsalen nanostructure. After complete characterization it is utilized for simultaneous determination of vitamin B2 (riboflavin) and B6 (pyridoxine) using differential pulse voltammetry (DPV). MWCNTs-MnIIIsalen coated on glassy carbon electrode (GC), represented as GC/MWCNTs-MnIIIsalen exhibits high sensitivity and low detection limit. This electrode demonstrates high reproducibility (R.S.D. = 3.7% and 3.4% for vitamin B2 and B6, respectively) and long storage stability (more than 10 days under normal room temperature condition). Methodologies for the analysis of vitamins B2 and B6 using GC/MWCNTs-MnIIIsalen in pharmaceutical formulations using simple electrochemical techniques are elucidated. © 2017
Improving Functional Behavior of MCM-41 by Encapsulating MnO2 Nanorods towards Simultaneous Determination of Purine Bases in DNA Samples
(Wiley-VCH Verlag, 2018) Rupali Gupta; Dharmendra Kumar Yadav; Vellaichamy Ganesan; Piyush Kumar Sonkar; Mamta Yadav
MnO2 nanorods incorporated MCM-41 nanocomposite (MnO2@MCM-41) is synthesized and employed as an electrode modifier for individual as well as simultaneous detection of purine bases, guanine (GU) and adenine (AD). For this purpose MnO2 nanorods are encapsulated within MCM-41 by simple one pot synthetic approach. FT-IR, UV-vis absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and electrochemical methods are employed to characterize the nanocomposite and other materials. The electrochemical attributes of glassy carbon electrode (GCE) modified with the MnO2@MCM-41 (represented as GCE/MnO2@MCM-41) towards the determination of GU and AD is studied in detail. Upon incorporation of MnO2 nanorods on MCM-41, noticeable upsurge in anodic peak current with a decline in peak potential is observed for both GU and AD oxidations in cyclic voltammetry studies. Individual as well as simultaneous determination of GU and AD are performed using differential pulse voltammetry (DPV) technique which offered a linear range of 100 nM to 100 μM for GU and AD with respective limit of detections, 44 and 66 nM. The practical applicability of the GCE/MnO2@MCM-41 for real world samples analysis is satisfactorily demonstrated with certain DNA samples by DPV. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
In situ Electrochemical Synthesis of a Composite Film Containing Nickel Hexacyanoferrate and Bentonite Clay for the Sensitive Determination of Acetaminophen and Dopamine
(Wiley-VCH Verlag, 2020) Mamta Yadav; Preeti Singh; Vellaichamy Ganesan; Rupali Gupta; Piyush Kumar Sonkar; Dharmendra Kumar Yadav
A composite film of nickel hexacyanoferrate (NiHCF) and bentonite (Bt) clay (abbreviated as NiHCF−Bt) is synthesized by an in situ electrochemical method. For this synthesis, nickel ions are immobilized on Bt clay by an ion-exchange process, equilibrating Bt clay with nickel nitrate. On a glassy carbon electrode (GCE), the nickel ion-exchanged Bt clay (Ni2+−Bt) is coated to get the modified electrode which is represented as GCE/Ni2+−Bt. The NiHCF−Bt composite film is prepared on the GCE surface using the GCE/Ni2+−Bt and scanning the electrode potentials between −0.10 to 1.00 V continuously in an aqueous solution containing potassium hexacyanoferrate and potassium chloride. This NiHCF−Bt modified GCE (GCE/NiHCF−Bt) exhibits redox peaks due to the oxidation and reduction of the central metal ion, Fe2+. The electro-generated Fe3+ present in the GCE/NiHCF−Bt, electrocatalytically oxidizes a range of drugs like acetaminophen (AC), dopamine (DA), and tyrosine (TY) at decreased overpotentials with high current. This property is advantageously used for the precise quantification of AC, DA, and TY. Sensitivity, limit of detection, and linear calibration range for the determination of AC are found to be 0.20 μA μM−1 cm−2, 1.5 μM, and 25.0–1000.0 μM, respectively. Further, the amount of AC present in pharmaceutical products is satisfactorily quantified which demonstrated the use of the NiHCF−Bt composite film in electroanalysis. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Individual and simultaneous voltammetric determination of ascorbic acid, uric acid and folic acid by using a glassy carbon electrode modified with gold nanoparticles linked to bentonite via cysteine groups
(Springer-Verlag Wien, 2017) Dharmendra Kumar Yadav; Rupali Gupta; Vellaichamy Ganesan; Piyush Kumar Sonkar
A voltammetric sensor for both the individual and the simultaneous determination of ascorbic acid (AA), uric acid (UA) and folic acid (FA) is described. It is based on a glassy carbon electrode (GCE) that was modified with bentonite (Bnt) that was first functionalized with cysteine (Cys) to which gold nanoparticles were linked. The resulting material (referred to as Au-Cys-Bnt) and the other materials were characterized by UV-vis spectroscopy, powder X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray analysis and electrochemical methods. The XRD peak positions of bentonite and Cys-functionalized bentonite prove the incorporation of Cys into bentonite. The XPS spectrum of Au-Cys-Bnt confirms the interaction of gold nanoparticles with the thiol group of Cys. The modified GCE displays high electrocatalytic activity for the oxidation of AA, UA and FA, typically at 0.19, 0.41, and 0.73 V (vs. SCE), respectively. Differential pulse voltammetric data show a linear response that covers the 1 μM to 25 mM concentration range for AA, the 1 to 200 μM concentration range for UA, and two linear ranges for FA, one from 5 to 100 μM and one from 100 μM to 1.5 mM. The sensor was applied to the determination of AA, UA and FA in (spiked) multi-vitamin syrup, bird serum and milk samples. [Figure not available: see fulltext.]. © 2017, Springer-Verlag Wien.
Insight into efficient bifunctional catalysis: Oxygen reduction and oxygen evolution reactions using MWCNTs based composites with 5,10,15,20-tetrakis(3′,5′-dimethoxyphenyl)porphyrinato cobalt(II) and 5,10,15,20-tetrakis(3′,5′-dihydroxyphenyl)porphyrinato cobalt(II)
(Elsevier Ltd, 2020) Mamta Yadav; Piyush Kumar Sonkar; Kamal Prakash; Vellaichamy Ganesan; Muniappan Sankar; Dharmendra Kumar Yadav; Rupali Gupta
Development of cost-effective, durable, and efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is still required for efficient fuel cells, metal-air-batteries, and water electrolysis. For that purpose we have prepared tetrakis(3′,5′-dimethoxyphenyl)porphyrinato cobalt(II) (CoDMTPP) and 5,10,15,20-tetrakis(3′,5′-dihydroxyphenyl)porphyrinato cobalt(II) (CoDHTPP). Further, multi-walled carbon nanotubes (MWCNTs) based composites of CoDMTPP (MWCNTs-CoDMTPP) and CoDHTPP (MWCNTs-CoDHTPP) are also prepared and characterized through spectroscopy (UV–vis, FTIR, and XPS), microscopy (SEM, TEM with EDAX), X-ray diffraction, thermogravimetry, and electrochemical techniques. The materials, MWCNTs-CoDMTPP and MWCNTs-CoDHTPP are immobilized on glassy carbon (GC) electrodes, represented as GC/MWCNTs-CoDMTPP and GC/MWCNTs-CoDHTPP. They show efficient ORR activity in acidic, basic, and neutral (pH 7.0 buffer) mediums. Further, both of these electrodes exhibit significant OER activity in 0.1 M KOH, indicating the bifunctional activity in basic medium. Based on the kinetic studies, the presence of –OH in the CoDHTPP is found to enhance the ORR activity. The electrodes, GC/MWCNTs-CoDMTPP and GC/MWCNTs-CoDHTPP exhibit high methanol tolerance capacity. A very small change in onset potential of 12 mV at GC/MWCNTs-CoDMTPP and 3 mV at GC/MWCNTs-CoDHTPP electrodes are observed for the ORR after 3000 continuous potential cycles indicating the high operational stability of the modified electrodes. © 2020 Hydrogen Energy Publications LLC
Ion exchange voltammetry at branched polyethylenimine cross-linked with ethylene glycol diglycidyl ether and sensitive determination of ascorbic acid
(Elsevier Ltd, 2013) Vellaichamy Ganesan; Pankaj Kumar Rastogi; Rupali Gupta; Matthew T. Meredith; Shelley D. Minteer
The construction and characterization of an electrochemical sensing platform based on a cationic polymer modified electrode are described in this work. The cationic polymer is prepared as a thin film on a glassy carbon electrode (GC) surface by in situ cross-linking of branched polyethylenimine (BPEI) with ethylene glycol diglycidyl ether (EGDE). Positively charged amino groups of this polymer (BPEI-EGDE) act as effective anion exchange groups. The ion exchange properties of BPEI-EGDE are investigated by determining the permeability of electroactive anions through the polymer film using cyclic voltammetry. Furthermore, the modified electrodes are used for the electrochemical detection of ascorbic acid (AA), which is feasible with the films alone or when hexacyanoferrate ([Fe(CN)6]4-), is electrostatically confined (by ion exchange) in the cationic BPEI-EGDE film. When compared with bare GC electrodes, a large decrease in AA oxidation overpotential is observed at the [Fe(CN)6]4--modified electrode surface. Kinetic parameters of electrocatalytic oxidation of AA by electrogenerated [Fe(CN)6]3- are evaluated by cyclic voltammetry and chronoamperometry. Finally, this method is employed for the determination of AA in a pharmaceutical tablet. © 2013 Elsevier Ltd. All rights reserved.