Comparison of Different Unmodified and Nano-Material Modified Sensors for the Ultrasensitive Determination of Serotonin Vivek Yadav, Mamta Raj, Rajendra N. Goyal Journal of the Electrochemical Society, 2020 A comparison of response of different unmodified and polymer nanocomposite modified sensors has been monitored for the sensitive determination of serotonin (5-hydroxytryptamine; 5-HT). For the modification of sensors, polymer nanocomposite of poly-bromocresol green (p-BG) with single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and graphene (GRA) were prepared by electro polymerization at the surface of edge plane pyrolytic graphite (EPPG). Surface morphology of the different unmodified and modified sensor surfaces was studied by using Electrochemical Impedance Spectroscopy, Field Emission Scanning Electron Microscopy, cyclic voltammetry and square wave voltammetry (SWV). The calibration curves for 5-HT were recorded using SWV and linear relations between peak current and concentration were found in the wide concentration range. For unmodified electrode surfaces, limit of detection were found as 1.339, 0.850, 0.737, 0.405 and 0.104 μ M for gold, palladium, glassy carbon, basal plane pyrolytic graphite and EPPG surfaces, respectively. The limit of quantification was found as 4.462, 2.835, 2.456¸ 1.349 and 0.348 μ M respectively. Among unmodified sensors, EPPG sensor exhibited lowest detection limit. The modified sensors p-BG/SWCNTs/EPPG, p-BG/MWCNTs/EPPG and p-BG/GRA/EPPG electrocatalyzed the oxidation of 5-HT and a well-defined oxidation peak with enhanced peak current was observed. The detection limit was observed as 5.9, 4.3 and 2.4 nM with quantification limit of 19.66, 14.33 and 8 nM, respectively. The lowest detection limit was found for p-BG/GRA/EPPG sensor in comparison to all unmodified and other modified surfaces. An excellent electrocatalytic activity of p-BG/GRA/EPPG surface towards the sensitive determination of 5-HT was noticed, which exhibited much lower L.O.D in comparison to the ones reported in recent years.
Determination of Tryptophan at Carbon Nanomaterials Modified Glassy Carbon Sensors: A Comparison Jay Gautam, Mamta Raj, Rajendra N. Goyal Journal of the Electrochemical Society, 2020 The effect of surface modification of glassy carbon (GC) by single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs) and graphene has been studied for the determination of tryptophan (Trp). The surface morphology of the unmodified and modified sensors was characterized by Field Emission Scanning Electron Microscopy(FE-SEM), Electrochemical Impedance Spectroscopy (EIS), square wave voltammetry (SWV) and cyclic voltammetry (CV). The unmodified GCE exhibited an oxidation peak for Trp at 846 mV at pH 7.4, whereas after the modification with SWCNTs/GCE the oxidation peak shifted to less potential at 685 mV. At MWCNTs/GCE and Graphene/GCE, a well-defined anodic peak was observed at 669 mV and 769 mV, respectively for the oxidation of Trp. Under optimum conditions, a linear calibration curve was observed at unmodified GCE in the concentration range of 10–100 μ M of Trp with a detection limit of 190 nM. At SWCNTs/GCE, Graphene/GCE and MWCNTs/GCE the detection limits observed were 15.5 nM, 10.3 nM and 4.6 nM, respectively. The oxidation of Trp involved equal number of proton and electron at all the sensors, which was confirmed by pH studies. A comparison of limit of detection indicated that the modified MWCNTs/GCE sensor exhibited best catalytic response for the sensitive determination of Trp.
Silver nanoparticles and electrochemically reduced graphene oxide nanocomposite based biosensor for determining the effect of caffeine on Estradiol release in women of child-bearing age Mamta Raj, Rajendra N. Goyal Sensors and Actuators B Chemical, 2019 A sensitive voltammetric biosensor based on silver nanoparticles (AgNPs) and electrochemically reduced graphene oxide (ErGO) nanocomposite modified pyrolytic graphite (AgNPs:ErGO/PG) has been prepared to determine the effect of caffeine (CAF) on the concentration of estradiol (EST) in the child-bearing aged women (18–35 yr). The modified surface was characterized by Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FE-SEM), Electrochemical Impedance Spectroscopy (EIS), Raman Spectroscopy, cyclic voltammetry (CV) and square wave voltammetry (SWV). The modified sensor exhibited exceptional electrocatalytic effects towards the oxidation of EST and CAF with a significant enhanced peak current. The linear calibration curves were found in the concentration range of 0.001–175 μM and 0.001–200 μM for EST and CAF respectively and the limits of detection were found as 0.046 nM, and 0.54 nM. The common metabolites present in the biological fluid matrix i.e. ascorbic acid (AA), uric acid (UA), xanthine (XT) and hypoxanthine (HX) did not interfere in the simultaneous determination of EST and CAF. The analytical applicability of the proposed sensor has been exhibited by analyzing EST and CAF in the human serum and urine samples of five women of child-bearing age.
Simultaneous detection of ATP metabolites in human plasma and urine based on palladium nanoparticle and poly(bromocresol green) composite sensor Mamta Raj, Jong-Min Moon, Rajendra N. Goyal, Deog-Su Park, Yoon-Bo Shim Biosensors and Bioelectronics, 2019 A sensitive voltammetric sensor based on palladium nanoparticles (PdNPs) and poly-bromocresol green (pBG) composite layer immobilized on amide functionalized single-walled carbon nanotubes (AmSWCNTs) modified pyrolytic graphite (PdNPs:pBG/AmSWCNTs/PG) has been prepared for the simultaneous determination of adenosine triphosphate (ATP) catabolites, inosine (INO), hypoxanthine (HX), xanthine (XT), and uric acid (UA). The modified PdNPs:pBG/AmSWCNTs/PG was characterized by electrochemical experiments and surface analysis, which exhibited exceptional electrocatalytic effects towards the oxidation of INO, HX, XT, and UA with a significant enhanced peak current and well resolved peaks separation for all the analytes. The linear calibration curves were obtained in the concentration range of 0.001-175 µM, 0.001-200 µM, 0.001-150 µM, and 0.001-200 µM and limits of detection were found as 0.95 nM, 1.04 nM, 1.07 nM, and 0.43 nM corresponding to INO, HX, XT, and UA, respectively. The common metabolites present in the biological fluids did not interfere in the determination. The applicability of the proposed sensor was successfully demonstrated by determining INO, HX, XT, and UA in the human plasma and urine and the obtained results were validated by using HPLC.
A Novel Hybrid Nano-composite Grafted Electrochemically Reduced Graphene Oxide Based Sensor for Sensitive Determination of Efavirenz Mamta Raj, Pankaj Gupta, Neeta Thapliyal, Rajendra N. Goyal Electroanalysis, 2017 A novel, facile fabrication, based on electrochemically reduced graphene oxide (ErGO), grafted with Pt nanoparticles and Nafion hybrid nano-composite (ErGO-Pt/Nafion) on the surface of edge plane pyrolytic graphite (EPPG) has been reported. The fabricated sensor has been used for the sensitive and selective determination of efavirenz (EFZ), a well-known drug for HIV infections. The ErGO-Pt/Nafion film was characterized by Field Emission Scanning Electron Microscopy (FE-SEM), Energy-dispersive X-ray spectrometry (EDS) and Electrochemical Impedance Spectroscopy (EIS). The experimental results reveal that the modified sensor displays an excellent electrocatalytic activity towards the oxidation of EFZ and exhibits a large linear dynamic relationship in the range of 0.05 μM to 150 μM, with a detection limit of 1.8 nM. Practical utility of the developed sensor has been demonstrated by determining the EFZ in biological fluids and pharmaceutical samples and a low detection limit with high sensitivity observed makes it valuable for the clinical diagnosis.
Graphene/conducting polymer nano-composite loaded screen printed carbon sensor for simultaneous determination of dopamine and 5-hydroxytryptamine Mamta Raj, Pankaj Gupta, Rajendra N. Goyal, Yoon-Bo Shim Sensors and Actuators B Chemical, 2017 A novel and sensitive electrochemical method has been developed for the simultaneous determination of dopamine (DA) and 5-hydroxytryptamine (5-HT) using graphene (GR) and poly 4-amino-3-hydroxy-1-naphthalenesulfonic acid modified screen printed carbon sensor. The electrochemical measurements were studied using cyclic voltammetry, square wave voltammetry, whereas the surface morphology of the modified sensor was characterized by Electrochemical Impedance Spectroscopy and Field Emission scanning electron microscopy. The fabricated sensor facilitated the analysis of DA and 5-HT in the concentration range 0.05–100 μM and 0.05–150 μM with the detection limit of 2 nM and 3 nM respectively. The fabricated sensor has been explored for the determination of 5-HT in the plasma samples and the selectivity of the proposed work has been proved by the analysis of DA and 5-HT in the presence of common metabolites present in biological fluids. The analytical applicability of the fabricated sensor has also been successfully demonstrated for the simultaneous detection of DA and 5-HT in the pharmacological formulations, human urine and blood samples.
Graphene nanoribbons/poly-bromocresol green based sensor for the simultaneous determination of 3,4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid Mamta Raj, Rajendra N. Goyal Journal of the Electrochemical Society, 2017 A novel voltammetric sensor based on graphene nanoribbons/poly-bromocresol green at the surface of pyrolytic graphite (p-BG/GNRs/PG) has been prepared for the simultaneous determination of 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA); metabolites of neurotransmitters dopamine and serotonin. Graphene nanoribbons (GNRs) were fabricated by longitudinal unzipping of multiwall carbon nanotubes to form one-dimensional form of graphene strip. The characterization of GNRs and p-BG/GNRs/PG sensor has been done by using Raman spectroscopy, X-ray diffraction method, Electrochemical Impedance Spectroscopy, Field Emission Scanning Electron Microscopy, Cyclic Voltammetry and Square Wave Voltammetry. The sensor displayed excellent electrocatalytic effects toward the oxidation of DOPAC and 5-HIAA with a remarkable increment in the peak current and negative shift of the anodic peak potentials for both the analytes. The calibration curves were found to be linear in the wide concentration ranges of 0.05–180 μM and 0.5–200 μM with detection limits as 1.2 nM and 3 nM (n = 3) for DOPAC and 5-HIAA, respectively. The quantification limits were found (for n = 3) as 4.8 nM and 5.6 nM corresponding to DOPAC and 5-HIAA, respectively. The utility of the sensor as a diagnostic tool has been established by determining DOPAC and 5-HIAA in the human plasma and urine samples.
A poly-(melamine)/poly-(glutamic acid) based electrochemical sensor for sensitive determination of 2-Thioxanthine Mamta Raj, Rajendra N. Goyal Sensors and Actuators B Chemical, 2017 A sensitive and selective edge plane pyrolytic graphite sensor, modified using poly-melamine and poly-glutamic acid (p-Mel-Glu/EPPG) co-polymeric film through a single electropolymerization step, has been fabricated for the determination of 2-Thioxanthine (2-TX). The extremely sensitive interlinked polymeric film formed at the surface of pyrolytic graphite was characterized by using Field Emission Scanning Electron Microscopy, Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Square Wave Voltammetry techniques. The sensing surface exhibited electrocatalytic effects towards the oxidation of 2-TX, by displaying the significant enhancement in the sensitivity in terms of an increase in the peak current and shift of the peak potential to less positive potentials. The proposed method exhibited linear relation of the peak current in the concentration range of 0.5–150 μM and the limit of detection and limit of quantification were found as 1.0 nM and 3.4 nM, respectively. The developed approach has successfully been applied for the quantification of 2-TX in the presence of common interferents present in the urine.
A facile method to anchor reduced graphene oxide polymer nanocomposite on the glassy carbon surface and its application in the voltammetric estimation of tryptophan in presence of 5-hydroxytryptamine Rosy, Mamta Raj, Rajendra N. Goyal Sensors and Actuators B Chemical, 2016 A 4-amino-3-hydroxy-1-naphthalenesulfonic acid (AHNSA) and reduced graphene oxide (rGO) based polymer nanocomposite (PNC) has been electrodeposited directly on the surface of glassy carbon electrode (GCE) using cyclic voltammertry. The electrochemical reduction of graphene oxide (GO) to rGO and the synthesis of PNC have been inspected using FE-SEM, TEM and Raman spectroscopy. The modified GCE was further used for the voltammetric quantification of Tryptophan (Trp) in the presence and absence of 5-hydroxytryptamine. The PNC modified sensor exhibited improved sensing and electrocatalytic properties in comparison to unmodified GCE, rGO modified GCE and AHNSA modified GCE. The fabricated sensor showed a linear calibration plot in the range of 0.5–200 μM with sensitivity and limit of detection (L.O.D.) of 0.0451 μA μM −1 and 316 nM (n = 3) respectively in comparison to 0.19 μA μM −1 and 2.54 μM (n = 3) respectively for unmodified GCE. The proposed method was also successfully applied for the determination of Trp in commercially available pharmaceutical formulations, human urine and plasma samples.
Comparison of different unmodified and nano-material modified sensors for the ultrasensitive determination of serotonin V Yadav, M Raj, RN Goyal Journal of The Electrochemical Society 167 (2), 027539 , 2020 2020 Citations: 11
Determination of tryptophan at carbon nanomaterials modified glassy carbon sensors: A comparison J Gautam, M Raj, RN Goyal Journal of the Electrochemical Society 167 (6), 066504 , 2020 2020 Citations: 13
Silver nanoparticles and electrochemically reduced graphene oxide nanocomposite based biosensor for determining the effect of caffeine on Estradiol release in women of child … M Raj, RN Goyal Sensors and Actuators B: Chemical 284, 759-767 , 2019 2019 Citations: 37
Simultaneous detection of ATP metabolites in human plasma and urine based on palladium nanoparticle and poly (bromocresol green) composite sensor M Raj, JM Moon, RN Goyal, DS Park, YB Shim Biosensors and Bioelectronics 126, 758-766 , 2019 2019 Citations: 27
Nanocomposites of Conducting Polymers as Sensors for Detecting Biomolecules and Drugs M Raj, N Kumar, RN Goyal 2019
A poly-(melamine)/poly-(glutamic acid) based electrochemical sensor for sensitive determination of 2-Thioxanthine M Raj, RN Goyal Sensors And Actuators B: Chemical 250, 552-562 , 2017 2017 Citations: 23
Graphene/conducting polymer nano-composite loaded screen printed carbon sensor for simultaneous determination of dopamine and 5-hydroxytryptamine M Raj, P Gupta, RN Goyal, YB Shim Sensors and Actuators B: Chemical 239, 993-1002 , 2017 2017 Citations: 149
A Novel Hybrid Nano‐composite Grafted Electrochemically Reduced Graphene Oxide Based Sensor for Sensitive Determination of Efavirenz M Raj, P Gupta, N Thapliyal, RN Goyal Electroanalysis 29 (2), 456-465 , 2017 2017 Citations: 12
Graphene nanoribbons/poly-bromocresol green based sensor for the simultaneous determination of 3, 4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic Acid M Raj, RN Goyal Journal of The Electrochemical Society 164 (13), B695-B703 , 2017 2017 Citations: 15
A facile method to anchor reduced graphene oxide polymer nanocomposite on the glassy carbon surface and its application in the voltammetric estimation of tryptophan in presence … M Raj, RN Goyal Sensors and Actuators B: Chemical 233, 445-453 , 2016 2016 Citations: 41
Poly-melamine film modified sensor for the sensitive and selective determination of propranolol, a β-blocker in biological fluids M Raj, P Gupta, RN Goyal Journal of The Electrochemical Society 163 (6), H388-H394 , 2016 2016 Citations: 23
MOST CITED SCHOLAR PUBLICATIONS
Graphene/conducting polymer nano-composite loaded screen printed carbon sensor for simultaneous determination of dopamine and 5-hydroxytryptamine M Raj, P Gupta, RN Goyal, YB Shim Sensors and Actuators B: Chemical 239, 993-1002 , 2017 2017 Citations: 149
A facile method to anchor reduced graphene oxide polymer nanocomposite on the glassy carbon surface and its application in the voltammetric estimation of tryptophan in presence … M Raj, RN Goyal Sensors and Actuators B: Chemical 233, 445-453 , 2016 2016 Citations: 41
Silver nanoparticles and electrochemically reduced graphene oxide nanocomposite based biosensor for determining the effect of caffeine on Estradiol release in women of child … M Raj, RN Goyal Sensors and Actuators B: Chemical 284, 759-767 , 2019 2019 Citations: 37
Simultaneous detection of ATP metabolites in human plasma and urine based on palladium nanoparticle and poly (bromocresol green) composite sensor M Raj, JM Moon, RN Goyal, DS Park, YB Shim Biosensors and Bioelectronics 126, 758-766 , 2019 2019 Citations: 27
A poly-(melamine)/poly-(glutamic acid) based electrochemical sensor for sensitive determination of 2-Thioxanthine M Raj, RN Goyal Sensors And Actuators B: Chemical 250, 552-562 , 2017 2017 Citations: 23
Poly-melamine film modified sensor for the sensitive and selective determination of propranolol, a β-blocker in biological fluids M Raj, P Gupta, RN Goyal Journal of The Electrochemical Society 163 (6), H388-H394 , 2016 2016 Citations: 23
Graphene nanoribbons/poly-bromocresol green based sensor for the simultaneous determination of 3, 4-dihydroxyphenylacetic acid and 5-hydroxyindoleacetic Acid M Raj, RN Goyal Journal of The Electrochemical Society 164 (13), B695-B703 , 2017 2017 Citations: 15
Determination of tryptophan at carbon nanomaterials modified glassy carbon sensors: A comparison J Gautam, M Raj, RN Goyal Journal of the Electrochemical Society 167 (6), 066504 , 2020 2020 Citations: 13
A Novel Hybrid Nano‐composite Grafted Electrochemically Reduced Graphene Oxide Based Sensor for Sensitive Determination of Efavirenz M Raj, P Gupta, N Thapliyal, RN Goyal Electroanalysis 29 (2), 456-465 , 2017 2017 Citations: 12
Comparison of different unmodified and nano-material modified sensors for the ultrasensitive determination of serotonin V Yadav, M Raj, RN Goyal Journal of The Electrochemical Society 167 (2), 027539 , 2020 2020 Citations: 11
Nanocomposites of Conducting Polymers as Sensors for Detecting Biomolecules and Drugs M Raj, N Kumar, RN Goyal 2019
