Browsing by Author "Ankit Kumar Singh"

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A highly efficient NiCo2O4 decorated g-C3N4 nanocomposite for screen-printed carbon electrode based electrochemical sensing and adsorptive removal of fast green dye
(Springer, 2024) Ankit Kumar Singh; Shreanshi Agrahari; Ravindra Kumar Gautam; Ida Tiwari
Herein, we demonstrate the preparation and application of NiCo2O4 decorated over a g-C3N4-based novel nanocomposite (NiCo2O4@g-C3N4). The prepared material was well characterized through several physicochemical techniques, including FT-IR, XRD, SEM, and TEM. The electrochemical characterizations via electrochemical impedance spectroscopy show the low electron transfer resistance of NiCo2O4@g-C3N4 owing to the successful incorporation of NiCo2O4 nanoparticles on the sheets of g-C3N4. NiCo2O4@g-C3N4 nanocomposite was employed in the fabrication of a screen-printed carbon electrode-based innovative electrochemical sensing platform and the adsorptive removal of a food dye, i.e., fast green FCF dye (FGD). The electrochemical oxidation of FGD at the developed NiCo2O4@g-C3N4 nanocomposite modified screen-printed carbon electrode (NiCo2O4@g-C3N4/SPCE) was observed at an oxidation potential of 0.65 V. A wide dual calibration range for electrochemical determination of FGD was successfully established at the prepared sensing platform, showing an excellent LOD of 0.13 µM and sensitivity of 0.6912 µA.µM−1.cm−2 through differential pulse voltammetry. Further, adsorbent dose, pH, contact time, and temperature were optimized to study the adsorption phenomena. The adsorption thermodynamics, isotherm, and kinetics were also investigated for efficient removal of FGD at NiCo2O4@g-C3N4-based adsorbents. The adsorption phenomenon of FGD on NiCo2O4@g-C3N4 was best fitted (R2 = 0.99) with the Langmuir and Henry model, and the corresponding value of Langmuir adsorption efficiency (qm) was 3.72 mg/g for the removal of FGD. The reaction kinetics for adsorption phenomenon were observed to be pseudo-second order. The sensitive analysis of FGD in a real sample was also studied. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023.
A Study on Dunaliella salina Under Selected Nutrient Manipulation with Reference to the Biomass, Lipid Content Along with Expression of ACCase and RuBisCO Genes
(Springer, 2023) Sk Riyazat Khadim; Abhishek Mohanta; Prabhakar Singh; Priyanka Maurya; Ankit Kumar Singh; Arvind Kumar Singh; Ravi Kumar Asthana
Energy crises and climate change attracted less-explored microalgae as renewable resources. Deficiencies of nitrogen and phosphorus are the most effective inducers of lipid accumulation in microalgae but at the cost of biomass productivity. Therefore, nitrogen, phosphorus, and carbon manipulation of the culture medium was adopted for maximizing lipid as well as biomass production in Dunaliella salina. Phosphate deficiency in combination with 1.25 mM KNO3 (1/8 of the basal) resulted in higher lipid content (341.1 mg g−1 dry cell weight, DCW), but lower biomass (13.12 mgL−1d−1 DCW). The addition of 10.00 mM NaHCO3 to such cultures enhanced not only lipid content to 1.17-fold but also biomass productivity to 2.25-fold. The increase in biomass may be correlated with the stress-ameliorating effects of bicarbonate augmentation which helped in maintaining the health of the cells, as reflected by robust photosynthetic performance. The two important enzymes, RuBisCO and ACCase were also monitored for their expressions. RuBisCO possesses large and small subunits (rbcL and rbcS) responsible for incorporation of CO2, and beta carboxyl transferase (accD) of the heteromeric ACCase is associated with the first and committed step of fatty acid biosynthesis. Enhanced biomass and lipid content in D. salina cells after NaHCO3 augmentation may be ascribed to 6.23-fold increase in the expression of accD and > 2.16-fold increase in rbcL and rbcS genes. Thus, the present work recommends a threshold level of nitrogen and bicarbonate in phosphate deficient D. salina cultures for simultaneously maximizing the biomass and lipid content. © 2022, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
An Array-based Photolithographically Patterned Electrochemical Sensing Platform for Highly Sensitive Determination of Uric Acid, Dopamine, l-Tryptophan, and Pyridoxine in Biological Samples
(Springer Nature, 2024) Ankit Kumar Singh; Shreanshi Agrahari; Shivani Shukla; Ida Tiwari; Muhammad Ahmad; S. Ravi P. Silva
Biomolecules play important roles in physiological functions and pharmacological characteristics of human body. Uric acid (UA) is the end product of purine. Dopamine (DA) is a neurotransmitter of catecholamine group. l-tryptophan is an essential amino acid that can be metabolized to neuroactive substances. Pyridoxine is a water-soluble vitamin playing an important role in nervous system. The abnormalities in their concentration levels led to a wide range of significant mental and physical illnesses. Thus, electrochemical analysis of these analytes on an array system would be beneficial from clinical or scientific points of view. This work was aimed at the development of practical sensor array for determination of multiple analytes on a single sensing platform using individually addressable microelectrodes. The occurrence of adsorption–desorption phenomenon on the surface of palladium microelectrode array (Pd MEA) printed on the silicon wafer through photolithography was exploited for electro-oxidation of UA, DA, l-tryptophan and pyridoxine. The sensing of electroactive UA was done using carbon nanotubes(CNTs) grown Pd MEA as a working electrode, while selectivity for other analytes was achieved by the modification of CNTs/Pd MEA through electrodeposition of poly(l-lysine) (poly(l-lysine)/CNTs/Pd MEA) for DA sensing, poly(l-arginine) (poly(l-arginine)/CNTs/Pd MEA) for l-tryptophan sensing and reduced graphene oxide (rGO/CNTs/Pd MEA) for pyridoxine sensing. The electrochemical differential pulse voltammetry (DPV) analyses reveal excellent linearity in the concentration ranges of 50–6000 µmol/L, 2–8000 µmol/L, 20–15,000 µmol/L, and 10–5000 µmol/L with detection limits of 15.0, 0.5, 10.0, and 1.0 µmol/L for UA, DA, l-tryptophan, and pyridoxine, respectively. The proposed multiple analytes sensor has shown very high sensitivities of 140, 9580, 2280, and 940 µA·(µmol·L−1)−1·cm−2 for UA, DA, l-tryptophan, and pyridoxine sensing, respectively. Further, accuracy and reliability of the fabricated sensor were also tested in real samples. © The Nonferrous Metals Society of China 2024.
Answer to comments on: ‘Voltammetric analysis of epinephrine using glassy carbon electrode modified with nanocomposite prepared from Co-Nd bimetallic nanoparticles, alumina nanoparticles and functionalized multiwalled carbon nanotubes’ by Ida Tiwari et al., (Doi: 10.1007/s11356-022–23660-y)
(Springer Science and Business Media Deutschland GmbH, 2023) Shreanshi Agrahari; Ankit Kumar Singh; Ravindra Kumar Gautam; Ida Tiwari
This is an answer to the letter by the editor that was sent in response to our previously published article entitled “Voltammetric analysis of epinephrine using glassy carbon electrode modified with nanocomposite prepared from Co-Nd bimetallic nanoparticles, alumina nanoparticles and functionalized multiwalled carbon nanotubes." We are grateful to the writers for showing an interest in our manuscript and for providing such helpful feedback. We emphasise that our research was just a preliminary investigation to detect epinephrine in different biological samples, however, in literature a link between epinephrine and acute respiratory distress syndrome (ARDS) is already reported. Hence, we are agreeing to the authors that epinephrine is suggested as a cause for ARDS following anaphylaxis. It is recommended that more research be carried out to evaluate the possibility of epinephrine as a cause for ARDS and to validate the therapeutic relevance of the findings. Additionally, the purpose of our research was electrochemical sensing of epinephrine alternative to the conventional means like HPLC, fluorimetry, etc. for epinephrine detection. We have found that benefits which the electrochemical sensors have, are their simplicity, cost-effectiveness, ease of use owing to their small size, mass manufacture, and straightforward operation, as well as their extreme sensitivity and selectivity, hence the electrochemical sensing methods are more beneficial than conventional techniques for epinephrine analysis. © 2023, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.
Development of g-C3N4/Cu-DTO MOF nanocomposite based electrochemical sensor towards sensitive determination of an endocrine disruptor BPSIP
(Elsevier B.V., 2021) Ankit Kumar Singh; Nandita Jaiswal; Ravindra Kumar Gautam; Ida Tiwari
In the present study, we successfully synthesized graphitic carbon nitride (g-C3N4) and functionalized with copper coordinated dithiooxamide metal organic framework (Cu-DTO MOF) to form g-C3N4/Cu-DTO MOF nanocomposite. The synthesized g-C3N4 and g-C3N4/Cu-DTO MOF nanocomposite were thoroughly characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). The TEM analysis of g-C3N4/Cu-DTO MOF composite material shows the successful immobilization of Cu-DTO MOF particles on the platform of g-C3N4 flakes. The electrochemical sensing performance of g-C3N4 and g-C3N4/Cu-DTO MOF nanocomposite modified electrodes were compared through sensitive determination of an endocrine disruptor i.e., 4-(4-isopropoxy-benzenesulfonyl)-phenol (BPSIP) using cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The detection limit was estimated to be 0.02 µM and sensitivity to be 0.5675 µAµM-1cm−2 for the proposed g-C3N4/Cu-DTO MOF nanocomposite based BPSIP sensor through DPV that are better as compared to g-C3N4 based sensor. Therefore, it was found that the nanocomposite based sensor has better sensing ability and was successfully applied for the determination of BPSIP in river water sample. © 2021 Elsevier B.V.
Electrochemical biosensors based on in situ grown carbon nanotubes on gold microelectrode array fabricated on glass substrate for glucose determination
(Springer, 2023) Ankit Kumar Singh; Nandita Jaiswal; Ida Tiwari; Muhammad Ahmad; S. Ravi P. Silva
A highly sensitive electrochemical sensor is reported for glucose detection using carbon nanotubes grown in situ at low temperatures on photolithographically defined gold microelectrode arrays printed on a glass substrate (CNTs/Au MEA). One of the main advantages of the present design is its potential to monitor 64 samples individually for the detection of glucose. The selectivity of the fabricated MEA towards glucose detection is achieved via modification of CNTs/Au MEA by immobilizing glucose oxidase (GOx) enzyme in the matrix of poly (paraphenylenediamine) (GOx/poly (p-PDA)/CNTs/Au MEA). The electrocatalytic and electrochemical responses of the proposed sensing platform towards glucose determination were examined via cyclic voltammetry and electrochemical impedance spectroscopy. The developed impedimetric biosensor exhibits a good linear response towards glucose detection, i.e., 0.2–27.5 µM concentration range with sensitivity and detection limits of 168.03 kΩ−1 M−1 and 0.2 ± 0.0014 μM, respectively. The proposed glucose biosensor shows excellent reproducibility, good anti-interference property, and was successfully tested in blood serum samples. Further, the applicability of the proposed sensor was successfully validated through HPLC. These results supported the viability of using such devices for the simultaneous detection of multiple electroactive biomolecules of physiological relevance. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s).
Electrochemical deposition of Pd on MoS2 supported graphene nanoflakes over functionalised MWCNTs as an immunosensor for detection of lung cancer biomarker
(Elsevier Inc., 2024) Shreanshi Agrahari; Ankit Kumar Singh; Ida Tiwari; Saripella Srikrishna
An electrochemical immunosensor was designed to quantify carcinoembryonic antigen (CEA), which is regarded as a tumour marker and prognostic indicator. The glassy carbon electrode (GCE) surface was modified using MoS2, graphene nanoflakes (GNs), fMWCNTs, and electrodeposited PdNPs for the first time to prepare a Pd-MoS2-GNs@fMWCNTs/GCE. The platform was activated with monoclonal anti-CEA. The prepared nanocomposite material helps in improving the surface area and conductivity of the GCE. Moreover, PdNPs act as a linker between nanocomposite materials and anti-CEA, which enhances electron transport. The procedure used to analyse CEA involve sequential addition of CEA into the solution of 5 mM [Fe(CN)6]3-/4- prepared in 0.1 M PBS (pH 7.4) in the presence of fabricated electrode and DPV and EIS methods were used as detection technique. The change in signal response for the [Fe(CN)6]3-/4- redox reaction before and after CEA interaction is considered as the immunosensor response which is directly correlated with CEA concentration. Further, in DPV, the signal inhibition approach was used to measure CEA by monitoring the decrease in oxidation peak current of [Fe(CN)6]3-/4- due to the formation of CEA/anti-CEA immunocomplex. The electrochemical immunosensor demonstrated low LOD of 2 pg/mL and a correlation coefficient of 0.98 within a broad linear range of CEA concentration from 0.002 to 500 ng/mL. The fabricated immunosensor displayed excellent selectivity, repeatability, and stability. Further, the proposed immunosensor effectively measured CEA levels in human blood serum, making it an effective tool for testing CEA in clinical samples. © 2023 Elsevier B.V.
Electrochemical Methods for the Detection of Pharmaceutical Residues in Environmental Samples
(CRC Press, 2023) Shreanshi Agrahari; Ankit Kumar Singh; Ravindra Kumar Gautam; Ida Tiwari
In the last decades, pharmaceutical residues have gained increased attention due to their harmful impacts on the environment, owing to their pseudo-persistent nature. Further, they act as potentially active toxic biochemicals present at trace levels (i.e., µg/L or ng/L), which cause long-term impacts both on human and animal welfare. Several techniques have been reported for detecting pharmaceutical residues, including HPLC, GC, LC/MS, GC/MS, optical techniques, immunoassay tests, NMR, Raman spectroscopy, etc. These approaches are expensive; time-consuming; need pre-sample preparation, extraction, purification; and require particular biomolecules (antibodies, antigens, enzymes) for analysis. Electrochemical methods are selective and sensitive and can detect low amounts of pharmaceutical residues in the environment owing to their efficiency, speed, cost-effective manufacturing, and short analysis time. Moreover, electrochemical methods provide quick on-site monitoring of pharmaceutical residues existing in the environment, owing to easy monitoring and automation. © 2024 selection and editorial matter, Vinod Kumar Garg, Ashok Pandey, Navish Kataria, and Caterina Faggio; individual chapters, the contributors.
Electrochemical oxidation and sensing of para benzoquinone using a novel SPE based disposable sensor
(Elsevier Ltd, 2023) Shreanshi Agrahari; Ankit Kumar Singh; Ravindra Kumar Gautam; Ida Tiwari
Para-benzoquinone (PBQ) is an emerging micro-contaminant owing to its chronic toxicity to plants and animals as well as its potential to induce cytotoxicity in primary rat hepatocytes and kidney cell injury. Hence, it is of utmost importance to monitor this contaminant in industrial wastewater and groundwater. In this article, we devised a unique disposable sensor that is based on a screen-printed electrode using MnO2@Co–Ni MOFs/fMWCNTs nanocomposite and is able to detect PBQ. The as-produced nanocomposite was prepared via ultrasonic assisted reflux condition and thoroughly examined by several physicochemical characterisation methods such as SEM, EDX, TEM, Raman, AFM, UV–visible, and FT-IR. Moreover, electrochemical methods like CV, DPV, EIS, and chronoamperometry were used for detecting PBQ on MnO2@Co–Ni MOFs/fMWCNTs/SPCE. Sensor performance has been investigated thoroughly and optimized to enhance the analytical potential of the fabricated sensor. DPV analysis was done on MnO2@Co–Ni MOFs/fMWCNTs that exhibit high selectivity, low peak potential, a broader linear detection range (0.005 mM–30 mM), and a LOD of 0.0027 ± 0.0005 mM. The designed electrode has shown remarkable reproducibility and excellent repeatability, with relative standard deviations of 0.12%, and 0.17%, respectively. Additionally, MnO2@Co–Ni MOFs/fMWCNTs/SPCE have been used to analyse PBQ in industrial wastewater samples, and the results have shown a significant level of recovery between 96.91 and 105.67%. Moreover, the PBQ sensor displays high applicability and was verified via the use of HPLC techniques. This disposable sensor is quick, easy, and cost-effective, so it can be useful in the future for analysing other phenolic contaminants present in environmental samples. © 2023 Elsevier Ltd
Electrochemical Sensing and Biomedical Applications of Green Nanomaterials
(Springer International Publishing, 2023) Ankit Kumar Singh; Ravindra Kumar Gautam; Shreanshi Agrahari; Ida Tiwari
Nanomaterials are used in a variety of fields, including agriculture, food technology, textiles, waste water treatment, cosmetics, sports goods, purification techniques, and medications, due to their huge surface area-to-volume ratio and size-dependent qualities. These nanomaterials are used in almost every aspect of life, yet there are safety concerns for their synthesis that produces long-term effects on the ecology. Green nanomaterials are an alternative that are made with environmentally friendly procedures and ingredients that produce less waste. In the field of materials science, “green” synthesis has received a lot of attention as a dependable, long-lasting, and environmentally friendly method for the preparation of a variety of nanomaterials, such as metal/metal oxide nanoparticles, carbon-based nanomaterials, and composite materials. As a result, green synthesis is recognized as a significant tool for reducing the detrimental impacts of standard nanomaterials synthesis methods used in laboratories and industries. Further, the synthesized green nanomaterials are suited for a variety of therapeutic applications due to their outstanding biocompatibility. They show antitumor characteristics, anticancerous properties, and toxicity to numerous disease-causing organisms. In this chapter, the approaches behind the fundamental process, mechanism, and various techniques for synthesizing green nanomaterials are discussed. The current research on the biogenesis of green nanomaterial and the characteristics of green nanomaterials generated with plant extracts, bacteria, fungus, and algae are summarized in this chapter. Finally, the potential uses of the green nanomaterials in electrochemical sensing and therapeutic fields are also discussed. The chapter’s assessment of green nanomaterials uses, their synthesis, and potential applications will be beneficial to scholars in this burgeoning discipline. © Springer Nature Switzerland AG 2023.
Exploring the recognition behavior of a fluorescein-based probe towards the significant detection of Cu2+ and Zn2+ ions: Experimental and computational studies
(Elsevier B.V., 2025) Navneet Kumar; Pawan Kumar Sada; Amit Kumar Kundan; Amit Bar; Amanpreet Kaur Jassal; Surya Prakash Rai; Vipendra Kumar Singh; Neha Garg; Alok Kumar Singh; Ankit Kumar Singh; Sumit Mohan Kumar; Laxman Singh; Abhishek Rai
A new fluorescein hydrazone (FA1) has been synthesized employing fluorescein hydrazide and 3,5-diiodosalicylaldehyde and its complete physiochemical characterization have been carried out. A single crystal XRD studies of FA1 has been performed. Among the tested metal ions FA1 significantly detects Cu2+ and Zn2+ in EtOH/H2O (8:2, v/v)). There is an emergence of a new absorbance peak at λmax 431 nm with Cu2+ ions. A “turn-on” behavior in fluorescence at λem510 nm was observed with Zn2+ ions owing to chelation enhanced fluorescence. This act of spectrophotometric changes and naked eye color variation from colorless to yellow is because of coordination with the metal ions rather than most common opening of spirolactum ring. FA1-Cu2+ and FA1-Zn2+ensembles display reversible behavior with EDTA2− ions. In a study on latent fingerprint detection using powder compounds, it was found that FA1 and FA1–Zn2+ showed excellent adherence to finger ridges and produced clear features without any background stains. The Hirshfeld surface and fingerprint analysis of FA1 offer a detailed examination of pairwise interactions between atoms. Additionally, topological analysis of FA1 has been conducted using NCI, AIM, ELF, and LOL methodologies. Alamar assay of FA1 on HEK-293 cell lines exhibited biocompatibility with minimal cytotoxicity. Hence, they were effectively applied for live cell imaging for intracellular sensing of Cu2+ and Zn2+ in HEK-293 cells. © 2025 Elsevier B.V.
Fabrication of a novel screen-printed carbon electrode based disposable sensor for sensitive determination of an endocrine disruptor BPSIP in environmental and biological matrices
(Elsevier Inc., 2023) Ankit Kumar Singh; Shreanshi Agrahari; Ravindra Kumar Gautam; Ida Tiwari
A screen-printed electrochemical sensor based on a graphene-modified screen-printed carbon electrode decorated with graphitic carbon nitride (g-C3N4@GN/SPCE) was examined for its ability to act as a sensitive and selective novel sensor for on-site monitoring of an endocrine disruptor, 4-(4-isopropoxy-benzenesulfonyl)-phenol (BPSIP). The successfully prepared g-C3N4 was thoroughly characterized using FESEM, TEM, EDX, FT-IR, XRD, UV– visible studies, and TGA. The prepared g-C3N4 was immobilized on GN/SPCE to prepare a low-cost and disposable sensor for electroanalytical measurement of BPSIP. The concentration of nanomaterial dispersion, pH, and composition of the buffer solution were also optimized for maximal response. At the optimized conditions, BPSIP was determined by cyclic voltammetry in two linear concentration ranges (1–100 µM and 100–1000 µM) with a very low detection limit of 0.02 ± 0.01 µM and unparalleled sensitivity of 0.9162 ± 0.0003 µA.µM−1.cm−2. Further, the electrochemical oxidation of BPSIP occurred at 0.65 V, suggesting the excellent electrocatalytic performance of g-C3N4@GN/SPCE. The proposed sensor has shown high repeatability and reproducibility as well as good anti-interference properties for BPSIP sensing. The feasibility of the as-prepared sensor is also tested in biological and water samples, with excellent recoveries in the range of 98–104 % for BPSIP sensing. © 2023
Fabrication of an innovative electrochemical sensor based on graphene-coated silver nanoparticles decorated over graphitic carbon nitride for efficient determination of estradiol
(Springer, 2024) Ankit Kumar Singh; Shreanshi Agrahari; Ravindra Kumar Gautam; Ida Tiwari
Monitoring small amount of endocrine disrupting chemical, estradiol (E2) residue in environmental and biological samples is extremely important because of its possible connections to breast and prostate malignancies and gastrointestinal disorders. The newly synthesized graphene-coated silver nanoparticles (GN@Ag) decorated on graphitic carbon nitride (g-C3N4)-based hybrid nanomaterial (GN@Ag/g-C3N4) was used to modify glassy carbon electrode (GCE) for electroanalytical measurement of E2. The GN@Ag/g-C3N4 nanocomposite prepared through ultrasonic-assisted reflux methodology was characterized using various physicochemical methods. The scanning electron microscopy and transmission electron microscopy have shown that GN@Ag nanoparticles were decorated and randomly dispersed over g-C3N4 sheets. The exceptional electrochemical response towards the oxidation of E2 was observed through cyclic voltammetry due to the quick electron transfer ability and superior conductivity of GN@Ag/g-C3N4/GCE. The detection limit was found to be 0.002 μM with wide linear range of E2 concentration (0.005–8.0 μM) along with remarkable stability of the fabricated electrode for 21 days showing 91% retention in initial current. The kinetic parameters such as catalytic rate constant and diffusion coefficient for E2 were estimated to be 1.1 × 105 M−1 s−1 and 1.9 × 10−4 cm2 s−1, respectively, by employing chronoamperometry. The proposed sensor also demonstrated its practical applicability for E2 determination in environmental and biological samples with a recovery range of 95–104%. Furthermore, the developed sensing platform is much better compared to reported methods in terms of simplicity, accuracy, detection limit, linearity range, and usefulness in real sample for E2 sensing. Graphical abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2022. Springer Nature or its licensor holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
Fabrication of gadolinium decorated spherical zinc oxide attached on carbon nanotubes (Gd@ZnO-MWCNTs) for electrochemical detection of a bisphenol derivative BPSIP in real sample matrices
(Springer Science and Business Media B.V., 2023) Shreanshi Agrahari; Ankit Kumar Singh; Ravindra Kumar Gautam; Ida Tiwari
In this study, we have developed a reliable electrochemical sensing platform for determining the residue of 4-(4-iso-propoxy-benzenesulfonyl)-phenol (BPSIP), an endocrine disruptor in blood serum, plastic and paper samples. A wide concentration range of BPSIP was electrochemically determined for the first time on glassy carbon electrode modified with newly developed gadolinium doped zinc oxide-multiwalled carbon nanotubes nanocomposite (Gd@ZnO-MWCNTs/GCE). The Gd@ZnO-MWCNTs nanocomposite was prepared by simple procedure through stirring under reflux condition and was characterized by several physicochemical techniques such as Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersive X-ray analysis (EDAX), and X-ray photoelectron spectroscopy (XPS). The electrochemical activity of the prepared nanocomposite was investigated by the differential pulse voltammetry (DPV). It was observed that Gd@ZnO-MWCNTs/GCE exhibits lower oxidation potential toward oxidation of BPSIP due to its fast electron transfer capability and high conductivity. A wide linear concentration ranges from 0.5 to 80 µM was attained with LOD of 0.2 µM. The sensitivities were found to be 26.33 µA mM−1and 14.89 µA mM−1 in two successive concentration ranges. The kinetic studies were also performed by employing chronoamperometry in the presence of BPSIP at Gd@ZnO-MWCNTs/GCE that exhibits catalytic rate constant (kcat) of 7.54 × 102 M−1 s−1 and the diffusion coefficient (D) of 1.56 × 10–5 cm2s−1. Further, the fabricated Gd@ZnO-MWCNTs/GCE has shown excellent reproducibility with resultant RSD of 0.21% and storage stability of 21 days with 86% retention in current. Graphical abstract: [Figure not available: see fulltext.]. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.
Graphene oxide supported Fe3O4-MnO2 nanocomposites for adsorption and photocatalytic degradation of dyestuff: ultrasound effect, surfactants role and real sample analysis
(Taylor and Francis Ltd., 2024) Ankit Kumar Singh; Ravindra Kumar Gautam; Shreanshi Agrahari; Jyoti Prajapati; Ida Tiwari
Present work demonstrates the synthesis, characterisation and application of a novel hybrid nanocomposite GO@Fe3O4-MnO2 for adsorption and catalytic degradation of dyestuff malachite green and tartrazine from wastewater. The nanocomposite GO@Fe3O4-MnO2 was characterised by FT-IR, XRD, SEM-EDS and pHzpc. Effects of various optimising parameters such as contact time, solution pH, surfactants, light, adsorbent dose, ultrasonication and coexisting ions were investigated. The removal efficiencies of malachite green and tartrazine were observed as high as 99.9% and 98% under direct sunlight, respectively. The adsorption kinetics follows the pseudo-second order model (R2 = 0.99) where k2 for malachite green and tartrazine were 0.0097 and 0.0011 g mg−1 min−1, respectively, that means adsorption was controlled by chemisorption. Equilibrium adsorption isotherm of these dyes was analysed in the context of Langmuir and Freundlich models, and the maximum adsorption capacity for Langmuir isotherm was found to be 8.0 and 5.1 mg g−1 for malachite green and tartrazine, respectively. The percentage removal was initially low, but when the ultrasound was irradiated, the removal percentage (96% for malachite green and 98% for tartrazine) was drastically increased because of the formation of highly active •H and •OH radicals in the water through the decomposition of water molecules by the formation of hot spots. On treatment with H2O2, advance oxidation processes were observed with high remediation percentage (99.5% for malachite green and 98% for tartrazine) of dye. The synthesised GO@Fe3O4-MnO2 was finally used for the treatment of dyes from real water samples. The used nanocomposite was separated using an external magnet and recycled with 0.1 N HCl or 0.1 N NaOH as desired. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
Green single-step hydrothermal synthesis of fluorescent carbon dots from Lantana camara flower for the effective fluorescent detection of Cr(VI) and live cell imaging
(Springer Science and Business Media Deutschland GmbH, 2025) Vikky Kumar Mahto; Vikas Kumar Singh; Vipendra Kumar Singh; Avinash K. Singh; Savita S. Singh; Arjun Kumar Mehara; Naina Rajak; Anurag Mishra; Neha Garg; Akanksha Upadhyay; Abhishek Rai; Ankit Kumar Singh
Chromium is one of the heavy metal ions showing high toxicity and mutagenicity. Owing to this, selective sensing of Cr(VI) from sample metrics is a challenging and tedious process. In the present work, we have synthesized fluorescent carbon dots (FCDs) using the flower of Lantana camara through a one-step hydrothermal method. Various spectroscopic techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), EDAX, and Raman analysis well supported the successful synthesis of FCDs. The obtained FCDs revealed a bright blue color under UV-light exposure (@ 365 nm), with excellent optical properties and a fluorescence quantum yield of 29%. Furthermore, FCDs showed excellent fluorescence stability, high ionic strength, good water solubility, low cytotoxicity, and well biocompatibility. Therefore, the proposed FCDs were employed for selective turn-off sensing of toxic Cr(VI) in an aqueous medium with a limit of detection (LOD) of 0.10 µM. Interestingly, the low cytotoxicity and excellent biocompatibility enable the FCDs as a good candidate for cell imaging agents as well as intracellular turn-off sensing of Cr(VI) in HEK-293 cells. Thus, the present work significantly converts biomass of weed plants into a fluorescent probe in a simple and cost-effective way for the detection of Cr(VI) in water samples as well as in living cells. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Green single-step hydrothermal synthesis of fluorescent carbon dots from Lantana camara flower for the effective fluorescent detection of Cr(VI) and live cell imaging
(Springer Science and Business Media Deutschland GmbH, 2024) Vikky Kumar Mahto; Vikas Kumar Singh; Vipendra Kumar Singh; Avinash Singh; Savita Singh; Arjun Kumar Mehara; Naina Rajak; Anurag Mishra; Neha Garg; Akanksha Upadhyay; Abhishek Rai; Ankit Kumar Singh
Chromium is one of the heavy metal ions showing high toxicity and mutagenicity. Owing to this, selective sensing of Cr(VI) from sample metrics is a challenging and tedious process. In the present work, we have synthesized fluorescent carbon dots (FCDs) using the flower of Lantana camara through a one-step hydrothermal method. Various spectroscopic techniques such as transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), EDAX, and Raman analysis well supported the successful synthesis of FCDs. The obtained FCDs revealed a bright blue color under UV-light exposure (@ 365 nm), with excellent optical properties and a fluorescence quantum yield of 29%. Furthermore, FCDs showed excellent fluorescence stability, high ionic strength, good water solubility, low cytotoxicity, and well biocompatibility. Therefore, the proposed FCDs were employed for selective turn-off sensing of toxic Cr(VI) in an aqueous medium with a limit of detection (LOD) of 0.10 µM. Interestingly, the low cytotoxicity and excellent biocompatibility enable the FCDs as a good candidate for cell imaging agents as well as intracellular turn-off sensing of Cr(VI) in HEK-293 cells. Thus, the present work significantly converts biomass of weed plants into a fluorescent probe in a simple and cost-effective way for the detection of Cr(VI) in water samples as well as in living cells. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.
Green synthesis of gold nanoparticles from Dunaliella salina, its characterization and in vitro anticancer activity on breast cancer cell line
(Editions de Sante, 2019) Ankit Kumar Singh; Ratnakar Tiwari; Vikas Kumar Singh; Prabhakar Singh; Sk Riyazat Khadim; Urmilesh Singh; Laxmi; Vikas Srivastava; S.H. Hasan; R.K. Asthana
An ecofriendly and efficient method (photoinduced) has been used for green synthesis of stable gold nanoparticles (AuNPs) using aqueous extract as a reducing and stabilizing agent, derived from halotolerant microalga Dunaliella salina. Synthesis of AuNPs was confirmed by UV–Vis spectroscopy showing sharp SPR band at 560 nm after 30 min exposure of sunlight. The synthesis was optimized further as exposure(75min) to sunlight, aqueous extract of Dunaliella (AED) inoculum dose(30%) and HAuCl 4 .xH 2 O (1 mM). The presence of nearly spherical shape of AuNPs with average size of 22.4 nm and crystalline nature were confirmed by TEM, SAED and XRD analysis. The XPS analysis of AuNPs showed presence of two individual peaks at 85.17 and 88.94eV that attributed to Au 4f7/2 and Au 4f5/2 respectively. Phycochemical analysis of AED demonstrated presence of phenolics, flavonoids, tannin and proteins. AED when subjected to SDS-PAGE showed protein bands of 92 and 66 KDa. AuNPs were tested for anticancer activity on MCF7 (cancer) and MCF 10A (normal) cell lines, keeping commercial drug cisplatin as positive control. AuNPs selectively killed cancer cells and were not detrimental to the normal cell line whereas cisplatin killed normal cells also at 48 h exposure, therefore, such AuNPs may be used as an anticancer agent. © 2019 Elsevier B.V.
In silico and in vitro evaluation of extract derived from Dunaliella salina, a halotolerant microalga for its antifungal and antibacterial activity
(Taylor and Francis Ltd., 2023) Urmilesh Singh; Laxmi; Prabhakar Singh; Ankit Kumar Singh; Sweksha Singh; Deepak Kumar; Sushant Kumar Shrivastava; Ravi Kumar Asthana
In the present study little explored halotolerant wall-less green alga Dunaliella salina was found to be a potent source of antibacterial and antifungal biomolecules. Both the target pathogens, bacteria (Escherischia coli, Klebsiella pneumoniae, and Acinetobacter baumannii) and fungi (Candida albicans, C. tropicalis, and Cryptococus sp.) were WHO prioritized. The bioassay guided approach led us to evaluate antibacterial and antifungal lead molecule(s) from an array of compounds using spectroscopic and in silico studies. The methanol derived crude extract was purified via thin layer chromatography (TLC) using solvent system methanol: chloroform (1:19). Maximum antimicrobial activity was observed in fractions D5, D6 and D7, the components of which were then recognized using high resolution-liquid chromatography/mass spectroscopy (Orbitrap) (HR-LC/MS). The screened compounds were then docked with target enzymes sterol-14-alpha demethylase and OmpF porin protein. The energy scores revealed that amongst all, lariciresinol-4-O-glucoside showed better binding affinity, in silico, using the Schrödinger Maestro 2018-1 platform. The 3-dimensional crystal structures of both the proteins were retrieved from the protein data bank (PDB), and showed binding energies of −14.35 kcal/mol, and −11.0 kcal/mol against respective drug targets. The molecular dynamics (MD) simulations were performed for 100 ns, using Desmond package, Schrödinger to evaluate the conformational stability and alteration of protein-ligand complexes during the simulation. Thus, our findings confirmed that lariciresinol-4-O-glucoside, a lignan derivative and known strong antioxidant, may be used as an important “lead” molecule to be developed as antibacterial and antifungal drugs in the future. Communicated by Ramaswamy H. Sarma. © 2022 Informa UK Limited, trading as Taylor & Francis Group.
Label free and ultrasensitive electrochemical detection of carcinoembryonic antigen using a disposable aptasensor based on Pd and graphene
(Elsevier Inc., 2024) Shreanshi Agrahari; Ankit Kumar Singh; Ida Tiwari; Saripella Srikrishna
We prepared an electrochemical aptasensor for label-free analysis of carcinoembryonic antigen (CEA). Herein, PdNPs were synthesized on the surface of graphene-modified screen-printed carbon electrodes (Pd-GN/SPCE) via electrochemical method for immobilisation of CEA aptamer as a bio-recognition element. The morphological characterizations of the fabricated Pd-GN/SPCE were performed using SEM, EDX, and elemental mapping that confirmed the successful electrochemical deposition of PdNPs. A disposable aptasensor for ultrasensitive electrochemical measurement of CEA was proposed by immobilising CEA aptamer on Pd-GN/SPCE. The electrochemical measurements were performed using 5 mM [Fe(CN)6]3-/4- as a redox probe. The electrochemical deposition of PdNPs improved the electrical conductivity resulting in enhanced current response for the redox probe. When CEA antigen interacts with CEA aptamer, it reduces the oxidation and reduction current of [Fe(CN)6]3-/4- due to the attachment of biomolecules to the electrode surfaces that hinders the electron transfer. The current changes of the redox species before and after CEA binding were measured using DPV. The developed aptasensor possessed a wide calibration range of 0.002–200 ng/mL and detection limit of 1.0 pg/mL. The aptamer-immobilised electrode provides an exceptional selectivity, reproducibility, and sensitive measurement of CEA. Moreover, the effective sensing of CEA in human serum samples with great recoveries (99.4––106 %) demonstrated its capability for clinical analysis. © 2024