Browsing by Author "Manorama Singh"

Now showing 1 - 10 of 10

Advances in Sensors' Nanotechnology
(Wiley Blackwell, 2014) Ida Tiwari; Manorama Singh
Nowadays, sensors are considered as important instruments available particularly in health care systems, for diagnosis and monitoring of diseases as there has been a strong demand for producing highly sensitive, responsive, selective, and cost-effective sensors. As a result, research emphasis is on developing new sensing materials and technologies to amplify signal of biorecognition event. In this context, the use of nanomaterials for the construction of sensor devices constitutes one of the most exciting approaches. The extremely promising prospects of these devices accrue from the unique properties of nanomaterials. Although different nanomaterials (e.g., carbon nanotubes, nanoparticles, graphene, etc.) are employed for the construction of sensors in different fields, it is in medical diagnostics where maximum application can be made due to enhanced analytical performance with respect to other designs. With the advent of nanotechnology, research is on track to create highly selective, highly sensitive and miniaturized sensors for medical applications. Miniaturized sensors can lead to lower power consumption, reduced weight, and low cost. © 2014 Scrivener Publishing LLC. All rights reserved.
An amperometric sensor for nanomolar detection of hydrogen peroxide based on encapsulation of horseradish peroxidase in thymol blue-ormosil composite
(2011) Ida Tiwari; Manorama Singh; V.S. Tripathi; G. Lakshminarayana; Masayuki Nogami
An amperometric biosensor based on horseradish peroxidase and thymol blue-organically modified sol-gel glass composite has been fabricated for the determination of H 2O 2. We are for the first time reporting electrochemistry of thymol blue encapsulated within organically modified sol-gel glass. The biosensor has been characterized by electrochemical and amperometric measurements. The biosensor shows fast response with minimum interference. Under the optimized experimental conditions, H 2O 2 could be determined in a linear calibration range from 1.0×10 -8 M to 1.2×10 -3 M with a correlation coefficient of 0.998, sensitivity of 23.74 μA/mM and a detection limit of 1 nM at S/N ratio = 3. Copyright © 2011 American Scientific Publishers All rights reserved.
An insight review on the application of polymer-carbon nanotubes based composite material in sensor technology
(2009) Ida Tiwari; K.P. Singh; Manorama Singh
Carbon nanotubes (CNT) polymer composites have shown potential applications for sensor/ biosensor fabrication. Methods for preparation, characteristics are highlighted and future aspects are explored. Various analytes and polymeric materials have been cited to prove the importance of polymer/CNT composite systems in sensor technology. © Pleiades Publishing, Ltd., 2009.
Annonaceous Acetogenins from the Seeds of Annona squamosa. Adjacent Bis-tetrahydrofuranic Acetogenins
(1994) Mahendra Sahai; Sanjewon Singh; Manorama Singh; Yogesh Kumar Gupta; Satoko Akashi; Reiko Yuji; Kazuo Hirayama; Hitomi Asaki; Hiroshi Araya; Noriyuki Hara; Tadashi Eguchi; Katsumi Kakinuma; Yoshinori Fujimoto
The petroleum ether extract of the seeds of Annona squamosa L. yielded thirteen adjacent and four non-adjacent bis-tetrahydrofuranic acetogenins, in addition to squamocin (1) and squamostatin-A. The structures of the thirteen acetogenins, named as squamocins-B (2), -C (3), -D (4), -E (5), -F (6), -G (7), -H (8), -I (9), -J (10), -K (11), -L (12), -M (13) and -N (14), have been established on the basis of spectral evidence. Squamocins-B, -D, -E, -F, -I, -K and -N are new acetogenins. The structures of these acetogenins vary in the carbon number (C37 or C35), the number and position of hydroxyl groups (substituted at C-4, C-12, C-28 or C-29) and the stereochemistry at the bis-tetrahydrofuran moiety. Squamocin-N (14) has an unprecedented threo-cis-threo-cis-threo stereochemistry in its bis-tetrahydrofuran portion. Co-occurrence of a diastereoisomeric pair, 9 and 10, is noteworthy. © 1994, The Pharmaceutical Society of Japan. All rights reserved.
Decoration of GO with Fe spinel-Naf/DMAP: An electrochemical probe for sensing H2O2 reduction
(Royal Society of Chemistry, 2016) Manorama Singh; Smita R. Bhardiya; Hemant Kashyap; Fooleswar Verma; Vijai K. Rai; I. Tiwari
We herein report the preparation of graphene oxide decorated with Fe spinel (Fe3O4)-Naf/DMAP for an unprecedented and highly selective non-enzymatic electrochemical sensing of hydrogen peroxide reduction. The linking of 3,7-bis (dimethylamino)-phenothiazin-5-ium chloride (DMAP) to the graphene oxide occurred via electrostatic interactions of the cationic organic compound with negatively charged oxygen-containing groups (-COO- and -O-) available on the edges of the graphene oxide. Fe3O4 (Fe2+, Fe3+) nanoparticles were adhered further on SO3- moieties of the Nafion coated over the DMAP-GO/GCE through electrostatic interactions. This green approach was used to prepare a derived graphene oxide hybrid nano-material. This material was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, X-ray diffraction (XRD), and cyclic voltammetry (CV). The prepared material was utilized to detect H2O2 subjected to electrocatalytic reduction and to determine its concentration in the linear range of 5.5 μM to 2.4 mM. Nafion was employed as a dispersion medium, and an anchor for Fe3O4 to make the composite and to prevent interfering effects of other metabolites. The detection limit of this highly selective and highly reproducible film was estimated to be 0.6 μM with a sensitivity of 32.0 μA mM-1 cm-2. © 2016 The Royal Society of Chemistry.
Electroanalytical properties and application of anthraquinone derivative-functionalized multiwalled carbon nanotubes nanowires modified glassy carbon electrode in the determination of dissolved oxygen
(2012) Ida Tiwari; Manorama Singh; Mandakini Gupta; S.K. Aggarwal
We herein report a simple, low cost and green preparation of nanowires of (anthraquinone-2-carboxylic acid/amino functionalized) multiwalled carbon nanotubes (HOOC-2-AQ/AMWCNTs) which has been further employed for the development of highly sensitive oxygen sensor. The prepared composite has been characterized by TEM and electrochemical studies. The glassy carbon electrode modified with composite shows an irreversible and good electrocatalytic activity for the reduction of oxygen. The reduction potential of the oxygen was shifted 460 mV towards the positive potential with this modified electrode as compared to bare glassy carbon electrode. The prepared material was stable with no leaching observed of the mediator. A linear response range of 0.2-6.8 mg L -1, with a sensitivity of 5.0 μA L mg -1 and a detection limit of 0.02 mg L -1 were obtained with this sensor. © 2012 Elsevier Ltd. All rights reserved.
Electrogenerated superoxide initiated oxidation with oxygen: A convenient method for the conversion of secondary alcohols to ketones
(Georg Thieme Verlag, 1989) Manorama Singh; Ram A. Misra
Various ketones can be prepared by the reaction of secondary alcohols with in situ electrochemically generated superoxide ion and molecular oxygen. As compared to the chemical oxidation of secondary alcohols to ketones, the reported method is milder and represents a useful extension to the known procedures. © 1989 Georg Thieme Verlag. All rights reserved.
Fabrication, characterization and application of carbon ceramic nanocomposite prepared by using multiwalled carbon nanotubes and organically modified sol-gel glasses
(Scientific Publishers, 2014) Ida Tiwari; Manorama Singh; K.P. Singh
We herein report the development of carbon ceramic nanocomposite nanoelectrodes by incorporation of multiwalled carbon nanotubes (MVVCNTs) in organically modified sol-gel glass (Ormosil) matrix which is derived from silane precursors, 3-glycidoxypropyltrimethoxysilane, tetraethoxysilane and 3-aminopropyltrimethoxysilane. The different ratios of the silanes precursors, temperature, and gelation time were all optimized in order to obtain a stable and reproducible film. The ceramic composite was modified with the incorporation of MWCNTs, a redox mediator ferricyanide and the enzyme Horseradish peroxidase (HRP). Characterization of the ceramic composite was performed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and cyclic voltammetry (CV). The ceramic composite sensor was explored towards the sensing of hydrogen peroxide providing a useful electroanalytical performance. © 2014 Scientific Publishers. All Rights Reserved.
Polyaniline/polyacrylic acid/multi-walled carbon nanotube modified electrodes for sensing ascorbic acid
(2012) Ida Tiwari; Karan Pratap Singh; Manorama Singh; Craig E. Banks
A multi-walled carbon nanotube composite electrode incorporating Polyaniline (PANI) and Polyacrylic acid (PAA) is presented by diffusing aniline and PAA into Nafion- MWCNTs membranes supported upon a platinum macrodisc electrode. Nafion is found to be an ideal medium for dispersion of MWCNTs and for the formation of a homogeneous composite. The composite has been characterized utilizing SEM, TEM, FT-IR and electrochemical techniques. Electrochemical characterization reveals that the redox activity of the composite is improved with the cumulative effect of MWCNTs and PAA as additives. The electroanalytical behavior of the composite is evaluated towards the sensing of ascorbic acid in the presence of dopamine and uric acid exhibiting a detection limit of 2.5 × 10 -7 M. © 2012 The Royal Society of Chemistry.
Preparation and characterization of methylene blue-SDS- multiwalled carbon nanotubes nanocomposite for the detection of hydrogen peroxide
(2011) Ida Tiwari; Manorama Singh
A nanocomposite was prepared by physical adsorption of (cationic) methylene blue (MB) on (anionic) sodium dodecylsulfate (SDS) that was wrapped on multiwalled carbon nanotubes (MWCNTs) on the surface of a glassy carbon electrode. This electrostatic interaction enables electrical communication between the electrode and analyte. Horseradish peroxidase was then immobilized in a film of gelatin on the nanocomposite to form a biosensor for hydrogen peroxide. Scanning electron microscopy, transmission electron microscopy, Fourier transform infrared and UV-vis spectrometry, and cyclic voltammetry were applied to characterize the electrode. The addition of both MWCNTs and MB causes a synergistic effect and leads to a large signal enhancement. The prepared nanocomposite material modified sensor shows better response in presence of several interferences. The biosensor has detection limit of 5 nM of hydrogen peroxide (at S/N = 3) with a linear response between 0. 2 μM and 1. 4 mM. Its lifetime is >4 months under dry conditions at 4 °C. © 2011 Springer-Verlag.