Browsing by Author "Monali Singh"

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A reduced graphene oxide-cyclodextrin-platinum nanocomposite modified screen printed electrode for the detection of cysteine
(Elsevier B.V., 2018) Monali Singh; Nandita Jaiswal; Ida Tiwari; Christopher W. Foster; Craig E. Banks
This article presents a highly sensitive and specific new sensing platform for cysteine determination. For the fabrication of electrochemical sensor, reduced graphene oxide-β-cyclodextrin-platinum nanocomposite (GR/CD/Pt) was prepared and surface of screen-printed electrodes were bulk modified with this nanocomposite which exhibited excellent electrocatalytic activity towards the sensing of cysteine. The GR/CD/Pt was characterized using SEM, TEM, AFM, FT-IR, TGA. The electrochemical behaviour of the fabricated sensor was investigated using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. During the determination of cysteine, a good electrocatalytic response current was obtained which is linear with respect to the concentration of cysteine over the range 0.5–170 μM with the limit of detection corresponding to 0.12 μM. © 2018 Elsevier B.V.
Design of screen-printed bulk modified electrodes using anthraquinone-cysteamine functionalized gold nanoparticles and their application to the detection of dissolved oxygen
(Royal Society of Chemistry, 2015) Ida Tiwari; Monali Singh; Mandakini Gupta; Jonathan P. Metters; Craig E. Banks
We investigated the electroanalytical determination of dissolved oxygen using low-cost disposable screen-printed bulk modified electrodes based on nanostructures. A nanostructure based on gold nanoparticles functionalized with an anthraquinone derivative and cysteamine was prepared. The nanostructured material was characterized morphologically using transmission electron microscopy and further physical characterization was carried out by energy-dispersive X-ray spectrometry. The prepared material was incorporated into a screen-printable graphite ink to develop the technology for the economic mass production of the next generation of field sensors. The electroanalytical determination of dissolved oxygen was possible in the range 0.2-6.1 mg L-1 with a detection limit of 0.131 mg L-1 (based on 3σ). We demonstrate proof-of-concept that this approach provides a rapid and inexpensive sensing strategy for the determination of dissolved oxygen in contaminated water samples. This journal is © The Royal Society of Chemistry.
Electrochemical detection of a pathogenic Escherichia coli specific DNA sequence based on a graphene oxide-chitosan composite decorated with nickel ferrite nanoparticles
(Royal Society of Chemistry, 2015) Ida Tiwari; Monali Singh; Chandra Mouli Pandey; Gajjala Sumana
In this report, an electrochemical genosensor has been fabricated for Escherichia coli O157:H7 (E. coli) detection using a graphene oxide-nickel ferrite-chitosan (GO/NiF/ch) nanocomposite film as the sensing platform. The prepared GO/NiF/ch nanocomposite was characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy and thermo-gravimetric analysis. Nucleic acid hybridization technique was employed for the detection of a specific sequence of E. coli. The hybridization between the complementary DNA and probe DNA was investigated by differential pulse voltammetry (DPV) using methylene blue as redox indicator. The fabricated biosensor exhibits a linear response to complementary DNA in the concentration range of 10-6 to 10-16 M with a detection limit of 1 × 10-16 M. © The Royal Society of Chemistry.
Electrochemical genosensor based on graphene oxide modified iron oxide-chitosan hybrid nanocomposite for pathogen detection
(Elsevier B.V., 2015) Ida Tiwari; Monali Singh; Chandra Mouli Pandey; Gajjala Sumana
In this report, a nucleic acid sensor has been fabricated via covalent immobilization of Escherichia coli O157:H7 (E. coli) specific probe oligonucleotide sequence, onto graphene oxide modified iron oxide-chitosan hybrid nanocomposite (GIOCh) film. The size of the GIOCh, as determined by dynamic light scattering and TEM, varies from 350 to 300 nm, while the zeta potential for the composite remains near 60 mV at pH 4.0. The prepared GIOCh are electrophoretically deposited onto indium tin oxide (ITO) coated glass substrate, used as cathode, while parallel platinum plate is used as counter electrode. The pDNA immobilized onto GIOCh/ITO electrode has been characterized using scanning electron microscopy; contact angle and Fourier transform infrared spectroscopy. Further, the electrochemical response studies carried out using electrochemical impedance spectroscopy reveals that this nucleic acid sensor exhibits a linear response to complementary DNA in the concentration range of 10-6-10-14 M with a detection limit of 1 × 10-14 M. Under optimal conditions, this biosensor is found to retain about 90% of the initial activity after 6 cycles of use. © 2014 Elsevier B.V. All rights reserved.
Electrochemical sensing of hydrogen peroxide using brominated graphene as mimetic catalase
(Elsevier Ltd, 2017) Shikha Singh; Monali Singh; Kheyanath Mitra; Rajshree Singh; Susanta Kumar Sen Gupta; Ida Tiwari; Biswajit Ray
Recently we have reported the peroxidase mimicking ability of metal free brominated graphene (GBR) (Analytical Chemistry, 89, 783–791, 2017) at a pH less than 7.2. Here we report the novel catalase mimicking ability of GBR via electrochemical (electro-oxidation) detection of hydrogen peroxide (H2O2) at pH ≥ 7.2. We have fabricated successfully a low cost electrochemical sensor using GBR coated glassy carbon electrode (GCE) [(GBR-GCE)-working electrode] and showed its excellent cyclic voltametry (CV) response towards electro-oxidation of hydrogen peroxide (H2O2), which is so far shown by electrodes made of platinum-group metals like Pt, Ir, Ru etc. Thus, GBR has exhibited the dual mimicking ability as peroxidase and also as catalase under different conditions. A plausible mechanism of sensing of hydrogen peroxide has been proposed involving the formation of perhydroxyl radical (HO2˙) facilitated by GBR-GCE as the electrode. Calibration curves for H2O2 detection using both CV and differential pulse voltametry (DPV) techniques have been constructed over 0.1–10 mM linearity range with the limits of detection of 0.048 and 0.063 mM, respectively. This fabricated electrochemical sensor is highly selective, specific and its response current is least affected by the presence of interfering analytes. The results are found highly reproducible and the use of GBR has also minimized the problem and specificity associated with natural enzymes, as it can easily be stored at room temperature. Real samples have also been successfully analyzed using our fabricated sensor. © 2017 Elsevier Ltd
Electrooxidation of dopamine at N-(1,3-dimethylbutyl)-N'-phenyl-p- phenylenediamine/multiwalled carbon nanotubes nanocomposite-modified electrode
(2013) Ida Tiwari; Mandakini Gupta; Monali Singh
A nanocomposite-modified electrode has been prepared by functionalizing multiwalled carbon nanotubes (MWCNTs) with N-(1,3-dimethylbutyl)-N′- phenyl-p-phenylenediamine (p-PDA). The physical characterization o. The prepared composite has been done using infrared spectroscopy and ultraviolet-visible spectroscopy. The morphologies o. The prepared p-PDA/MWCNTs/ionophore film have been characterized using scanning electron microscopy and transmission electron microscopy. The electrochemical studies o. The prepared composite electrode have been investigated by cyclic voltammetry technique. We observed tha. The p-PDA/MWCNTs/ionomer composite has better electrochemistry, film adhesion with homogeneous dispersion a. The electrode surface and an electrocatalytic activity towar. The oxidation of dopamine (DA) in 0.1 M phosphate buffer solution (pH 7.0) at a potential of 50 mV. The linear range and detection limit fo. The detection of DA was found to be 62-625 and 5 ÂM respectively. The modified electrode also exhibited several attractive features such as simple preparation, fast response, good stability and repeatability. © 2013 Materials Research Society.
Highly sensitive and selective determination of dopamine using screen-printed electrodes modified with nanocomposite of N′-phenyl-p-phenylenediamine/multiwalled carbon nanotubes/nafion
(Elsevier Ltd, 2018) Monali Singh; Ida Tiwari; Christopher W. Foster; Craig E. Banks
The presented research investigation focuses on the electroanalytical sensing of dopamine using disposable and economic nanocomposite based screen-printed bulk modified electrodes. A multiwalled nanotube based nanostructured composite of N'-phenyl-p-phenylenediamine and nafion was prepared. The prepared composite has been characterized morphologically using X-Ray diffraction, atomic force microscopy while the other physical characterization were carried out via Brunauer–Emmett–Teller (BET) measurements and thermal gravimetric analysis. The material was further employed within a graphitic ink for the development of a next generation sensor, which can be mass produced at an economical rate allowing for further development of this technology from the laboratory into the field. The electroanalytical determination of dopamine is found to be possible over the concentration range of 1μM–110 μM with a corresponding limit of detection of 0.01 μM (based on 3-sigma). In this paper, we demonstrate proof-of-concept that provides a rapid strategy for the determination of dopamine within real samples. © 2018 Elsevier Ltd
Synthesis, crystal structure and nuclease activity of a Cu(II) complex having two different co-ordination geometries in the same unit cell
(Elsevier B.V., 2013) Virendra Kumar; Rakesh K. Mishra; Sachin Shukla; R. Mishra; Monali Singh; Ida Tiwari; Kamlesh Thapliyal; K.K. Upadhyay
A new Cu(II) complex of a Schiff base ligand having N2O donor set has been synthesized and fully characterized through its single crystal X-ray studies. Two different co-ordination patterns viz. square planar and square pyramidal for Cu(II) were observed within the same unit cell. The DNA binding of copper(II) complex was investigated through UV-vis, fluorescence as well as cyclic voltammetric studies. The complex exhibited efficient functional mimicking of nuclease activity over the plasmid pBR322 DNA. © 2013 Elsevier B.V. All rights reserved.