Browsing by Author "Pradeep Kumar Yadav"

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A Facile and Simple Strategy for the Synthesis of Label Free Carbon Quantum Dots from the latex of Euphorbia milii and Its Peroxidase-Mimic Activity for the Naked Eye Detection of Glutathione in a Human Blood Serum
(American Chemical Society, 2019) Daraksha Bano; Vijay Kumar; Vikas Kumar Singh; Subhash Chandra; Devendra Kumar Singh; Pradeep Kumar Yadav; Mahe Talat; Syed Hadi Hasan
Herein a green synthetic route has been developed for the synthesis of water-soluble CQDs by facile single-step hydrothermal treatment of latexes of E. milii plant for the first time. This methodology is zero-cost; uses ultrapure water as a green solvent; does not use strong concentrated acid; and avoids the use of post surface passivating agents. The as-prepared CQDs exhibited excellent optical properties, including high QY up to 39.2%, resistance to high salt strength, and long time photostability. Furthermore, the as-prepared CQDs served as an intrinsic peroxidase-mimic activity to catalyze the chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) associated with H 2 O 2 , which resulted into a blue-colored reaction with a characteristic absorbance peak at 652 nm. Afterward, the proposed TMB-based oxidation system act as a probe for the detection of GSH and offers the high selectivity relative to the different amino acids and various other interfering agents which can be easily seen with naked eye. The limit of detection (LOD) was found to be 5.3 nM in a linear range 0.02 to 0.1 μM of GSH concentration which showed to be superior under the optimal condition as compared with another probe. To demonstrate the practical feasibility for the GSH detection, the present system was successfully applied on human blood serums with good recovery. © 2018 American Chemical Society.
An overview on emerging and innovative technologies for regulating arsenic toxicity in plants
(wiley, 2022) Arun Kumar; Pradeep Kumar Yadav; Anita Singh
Arsenic (As) is counted among the major metalloid elements that can cause cancer in human beings along with other harmful consequences. It occurs in several chemical forms such as arsenate [As (V)], arsenite [As (III)], and methylated As (monomethyl As acid [MMA], and dimethyl As acid [DMA]). There are natural as well as anthropogenic sources of As that affect each environmental component including the plant system. Among all forms, As (V) holds for the most dominant phytoavailable form of As present, particularly in aerobic soils. In plants, its uptake is known to occur by the high-affinity phosphate uptake system owing to its analogous nature to that of phosphate. The accumulation of As leads to several adverse effects on plant physiological processes that consequently reduce the yield of plants. Therefore, there is utmost need for affordable and efficient technologies to control the negative impacts of As contamination. These technologies can manage to reduce its availability and toxicity in plants, which further reduce the risk to human health. The present chapter includes the uptake process of As by the plants and its toxic response. It is mainly focused on the different remediation approaches for the reduction of As toxicity in the plants. Through the administration of signaling molecules, phytohormones along with some new technologies like the use of nanoparticles (NPs) and genetic manipulation, the level of toxicity can be reduced in the As-contaminated plants. Among all the techniques, the most efficient and sustainable techniques should be promoted with further research progress. © 2023 John Wiley & Sons, Inc.
An Overview on Management of Micronutrients Deficiency in Plants Through Biofortification: A Solution of Hidden Hunger
(Springer Singapore, 2020) Pradeep Kumar Yadav; Anita Singh; S.B. Agrawal
Nowadays, malnutrition is one of the major problems, especially for the poor population of developing countries. The major staple crops are found to be deficient in some mineral elements, especially the micronutrients that result in the problem of hidden hunger. There are several promising strategies that are applied in agricultural fields to solve this problem. They enhance the bio-available concentrations of micronutrients in edible crops. One of the recent strategy is biofortification, which can be used to increase the content and/or bioavailability of vital nutrients in food crops through genetic (genetic transfor- mation/plant breeding) and agronomic pathways (application of nutrient fertilizers). These strategies provide more nutritious diets to more people. Along with the traditional agricultural practices, the “omics” technologies can modify the crops by genetic transformation that improves the uptake, transport, and mineral accumulation in hybrid plants. This chapter has detail information about the nutrient constituents and its uptake in the plants along with a critical comparison of the several strategies that have been developed to enhance mineral levels and bioavailability of micronutrients in most of the important food crops. The use of biofortified crops should be promoted by educating the farmers by government agencies, so that they can be included in their diet to solve the problem of malnutrition up to certain extent. © Springer Nature Singapore Pte Ltd. 2020.
An overview on the modulation of pesticide detoxification mechanism via salicylic acid in the plants
(Taylor and Francis Ltd., 2023) Arun Kumar; Pradeep Kumar Yadav; Shikha Singh; Anita Singh
The continuous application of pesticides leads to several harmful effects on the ecosystem and get accumulated in the food chain. To regulate the toxicity of pesticides there are several strategies available. In relation to this, the endogenous as well as exogenous role of salicylic acid in pesticide regulation is less overviewed. To regulate the pesticide stress, in presence of salicylic acid, the genes, and proteins related to reduced glutathione (GSH) metabolism, biosynthesis of secondary metabolites, glyoxylate, and dicarboxylate metabolism get upregulated and are found to be more differentially expressed for pesticide detoxification. Salicylic acid regulates pesticide toxicity by activating gene expression of P450, antioxidant enzymes, ABC transporters subfamilies to form a defense network. In this context, the present review tries to comprehend the pesticide detoxification processes involving salicylic acid to regulate the stress caused thereby in plants and further utilize this strategy for wider application. © 2023 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Bright-blue-emission nitrogen and phosphorus-doped carbon quantum dots as a promising nanoprobe for detection of Cr(vi) and ascorbic acid in pure aqueous solution and in living cells
(Royal Society of Chemistry, 2018) Vikas Kumar Singh; Virendra Singh; Pradeep Kumar Yadav; Subhash Chandra; Daraksha Bano; Vijay Kumar; Biplob Koch; Mahe Talat; Syed Hadi Hasan
Highly fluorescent nitrogen and phosphorus-doped carbon quantum dots (N,P-CQDs) were synthesized via a one-step hydrothermal method and fully characterized via various techniques such as TEM, DLS, FT-IR, P-XRD and XPS analysis. The as-synthesized N,P-CQDs showed excellent optical properties and exhibited bright blue colour under UV-light with CIE coordinate (0.20, 0.22) along with a high quantum yield of 73%, due to which they could act as on-off fluorescent nanoprobes for the selective and sensitive detection of highly toxic Cr(vi) below its permissible limit via the inner filter effect (IFE) and static quenching mechanism. In addition, Cr(vi) could be reduced to lower valent chromium species. Therefore, the N,P-CQDs + Cr(vi) system further acted as a selective off-on sensor for reductant ascorbic acid (AA) because it reduced Cr(vi) to Cr(iii) species, resulting in the elimination of IFE and recovery of fluorescence of N,P-CQDs. Notably, this system possesses excellent biocompatibility and negligible cytotoxicity; therefore, it can be potentially applied for fluorescence imaging of intracellular Cr(vi) and ascorbic acid (AA) in living cells and complex biological systems. © 2018 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Effect of Rhizospheric application of NO on soil characteristics and functional attributes of Spinacia oleracea grown in untreated wastewater irrigated soil of Lohta Varanasi
(Springer Science and Business Media Deutschland GmbH, 2025) Pradeep Kumar Yadav; Arun Vishnu Kumar; Anita K. Singh
Aims: Heavy metal contamination in soils poses a serious threat to crop health and productivity, necessitating eco-friendly mitigation approaches. This study investigates the potential of nitric oxide (NO), applied as sodium nitroprusside (SNP), as an exogenous agent to alleviate metal-induced toxicity in Spinacia oleracea. It evaluates NO’s role in regulating metal accumulation, oxidative stress, and overall plant performance. Method: NO was applied at five concentrations (10, 50, 100, 200, and 500 µM) in the rhizospheric zone of metal-contaminated soil for growing spinach plants. Untreated contaminated soil served as the control. Physiological attributes such as oxidative biomarkers [hydrogen peroxide (H₂O₂), superoxide radicals (SOR), and malondialdehyde (MDA) content], antioxidant enzyme activities [superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)], and leaf surface morphology using scanning electron microscopy (SEM) were assessed. High-resolution mass spectrometry (HRMS) was used to quantify metabolite profiles to find out their role in regulating metal toxicity. Results: Among all treatments, 100 µM NO was found to be most effective, significantly enhanced biomass and reduced levels of H₂O₂, SOR, and MDA. A concurrent reduction in SOD, POD, and CAT activities indicated alleviated oxidative stress. SEM analysis showed improved leaf surface integrity, and HRMS confirmed better metabolic balance and reduced metal ion concentrations in the plant parts. Conclusion: Application of NO at 100 µM will be able to mitigate heavy metal toxicity, for enhancing physiological performance and growth of S. oleracea. This approach offers a promising and sustainable strategy for improving crop productivity in metal-contaminated soils. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2025.
Fluorometric sensing probe using carbon quantum dots for selective detection of doxycycline antibiotic
(Springer, 2025) Deepak Kumar; Subhash Chandra; Vivek V. Kumar; Pradeep Kumar Yadav; Syed Hadi Hasan
Due to the sturdy photoluminescence and absorption, CQDs emerged as a suitable candidate for optical sensing probe. The present study deals with the synthesis of blue-fluorescent Carbon Quantum Dot (TAA-CQD) using tannic acid and glycine as novel precursors. The TAA-CQD were synthesised hydrothermally with the high production yield and QY to be 86.12 and 21%, respectively, and an average particle size of 1.9 nm. The TAA-CQD aqueous solution displays excitation-dependent fluorescence emission in the excited range from 420 to 650 nm. The CIE co-ordinates in a highly blue region at (0.14, 0.19) confirmed the synthesised TAA-CQD were blue in fluorescent. Fluorescence of TAA-CQD was stable under all pH range, resisted the high ionic strengths condition and stable over 8 months. Furthermore, the fluorescent TAA-CQD was capable in detecting a tetracycline-classed antibiotic Doxycycline (DXY) along with remarkable selectivity and sensitivity. The measures limit of detection (LOD) was very low 2.42 mM in comparison to other methods. Moreover, the applicability of the proposed work has been fruitfully employed on the pharmaceutical waste. Thus, our designed TAA-CQD based fluorescence sensing system hold great promise for the advanced sensing materials in the detection of DXY and we believe that our approach will be promising and viable in a clinical applications. © The Author(s), under exclusive licence to Korean Carbon Society 2025.
Gas hydrate saturation from NGHP 02 LWD data in the Mahanadi Basin
(KeAi Communications Co., 2024) Uma Shankar; Pradeep Kumar Yadav; Sneha Devi; Udham Singh Yadav
During the Indian National Gas Hydrate Program (NGHP) Expedition 02, Logging-while-drilling (LWD) logs were acquired at three sites (NGHP-02-11, NGHP-02-12, and NGHP-02-13) across the Mahanadi Basin in area A. We applied rock physics theory to available sonic velocity logs to know the distribution of gas hydrate at site NGHP-02-11 and NGHP-02-13. Rock physics modeling using sonic velocity at well location shows that gas hydrate is distributed mainly within the depth intervals of 150–265 m and 100–215 mbsf at site NGHP-02-11 and NGHP-02-13, respectively, with an average saturation of about 4% of the pore space and the maximum concentration of about 40% of the pore space at 250 m depth at site NGHP-02-11, and at site NGHP-02-13 an average saturation of about 2% of the pore space and the maximum concentration of about 20% of the pore space at 246 m depth, as gas hydrate is distributed mainly within 100–246 mbsf at this site. Saturation of gas hydrate estimated from the electrical resistivity method using density derived porosity and electrical resistivity logs from Archie's empirical formula shows high saturation compared to that from the sonic log. However, estimates of hydrate saturation based on sonic P-wave velocity may differ significantly from that based on resistivity, because gas and hydrate have higher resistivity than conductive pore fluid and sonic P-wave velocity shows strong effect on gas hydrate as a small amount of gas reduces the velocity significantly while increasing velocity due to the presence of hydrate. At site NGHP-02-11, gas hydrate saturation is in the range of 15%–30%, in two zones between 150-180 and 245–265 mbsf. Site NGHP-02-012 shows a gas hydrate saturation of 20%–30% in the zone between 100 and 207 mbsf. Site NGHP-02-13 shows a gas hydrate saturation up to 30% in the zone between 215 and 246 mbsf. Combined observations from rock physics modeling and Archie's approximation show the gas hydrate concentrations are relatively low (<4% of the pore space) at the sites of the Mahanadi Basin in the turbidite channel system. © 2023 Sinopec Petroleum Exploration and Production Research Institute
Green Carbon Quantum Dots for Efficient Sensing of Heavy Metal Ions
(Springer Science and Business Media Deutschland GmbH, 2024) Pradeep Kumar Yadav; Vellaichamy Ganesan
Owing to their unique fluorescence properties, carbon quantum dots (CQDs), the new zero-dimensional carbon nanomaterials have intrigued many research interests. CQDs have attracted massive attention worldwide because of their stunning properties like high solubility, high fluorescence intensity, biocompatibility, low toxicity, and easy surface functionalization. As a result, CQDs can cover various possible applications in many fields including catalysis, medical, light-emitting diodes, energy-related fields, and sensing. The selective and sensitive detection of heavy metal ions using CQDs involves exploiting the unique properties of these nanomaterials, particularly their fluorescence behavior. The use of green carbon quantum dots (CQDs) for detecting heavy metal ions is an area of growing interest due to the eco-friendly nature of the synthesis process and the unique properties of CQDs. Green synthesis typically involves using natural extracts, such as plant extracts or waste materials to produce CQDs. In this chapter, we will summarize and discuss the synthesis methods, surface passivation and functionalization, stability, mechanism of fluorescence sensing, and applications of CQDs for selective and sensitive detection of heavy metal ions. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
Green Synthesis of Fluorescent Carbon Quantum Dots from Azadirachta indica Leaves and Their Peroxidase-Mimetic Activity for the Detection of H 2 O 2 and Ascorbic Acid in Common Fresh Fruits
(American Chemical Society, 2019) Pradeep Kumar Yadav; Vikas Kumar Singh; Subhash Chandra; Daraksha Bano; Vijay Kumar; Mahe Talat; Syed Hadi Hasan
In the present study, an ecofriendly and zero-cost approach has been demonstrated for the preparation of carbon quantum dots by one-pot hydrothermal treatment of leaf extracts of neem (Azadirachta indica). The as-synthesized neem carbon quantum dots (N-CQDs) exhibited high fluorescent quantum yields (QYs) up to 27.2%. Moreover, N-CQDs also act with a peroxidase-like-mimetic activity toward the oxidation of peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) in association with hydrogen peroxide (H 2 O 2 ). Further, the kinetics of peroxidase-like catalytic activity follows the Michaelis-Menten and ping-pong pathway. In addition, the H 2 O 2 sensitive TMB oxidation motivated the colorimetric detection of H 2 O 2 which showed linearity from 0.1 to 0.5 mmol/L with a detection limit (LOD) of 0.035 mmol/L. Furthermore, the blue colors of oxidized TMB (ox-TMB) were selectively reduced in native TMB with ascorbic acid (AA) without any interference of other reducing agents. The linear range of AA detection was lying between 5 and 40 μM with a LOD up to 1.773 μM. The practicability assay of the proposed sensing system toward the detection of AA was also investigated in real sample analysis such as common fruits which showed good sensitivity to the presence of AA. Therefore, this convenient, ecofriendly, and cost-effective peroxidase-based sensing system opens a new platform for analysis of AA in real samples and in complex biological systems. Copyright © 2018 American Chemical Society.
Highly sensitive electrochemical sensing of ascorbic acid (vitamin C) using Pd-doped MnO2 supported on carbon quantum dots (Pd-MnO2@CQD) in water and fruit juices
(Springer, 2025) Deepak Kumar; Daraksha Bano; Subhash Chandra; Bharat Kumar; V. Sampath Sampath Kumar; Pradeep Kumar Yadav; Syed Hadi Hasan
The Pd-MnO2 nanoparticles attached to carbon quantum dots nanocomposite were synthesized using the green synthesis and hydrothermal process. Characterization of the as-prepared nanocomposite was intensively performed by FT-IR, powder XRD, XPS, and HR-TEM analysis. The synthesized nanomaterial was further examined for its selective and sensitive ascorbic acid (ASA) sensing using a Pd-MnO2@CQD modified glassy carbon electrode (GCE). The Pd-MnO2@CQD nanocomposite exhibits a distinct and improved peak current of ASA when compared to electrodes treated with Pd-MnO2 and bare GCE. The designed sensor has excellent performance, with a linear range of 10–1500 μM, a low detection limit of 0.14 μM (S/N = 3), a high sensitivity of 1.9671 μAµM−1 cm−2. Furthermore, the constructed sensor demonstrates good sensitivity for detecting ASA in a variety of real samples. © The Author(s), under exclusive licence to The Japan Society for Analytical Chemistry 2025.
Hydrogen sulfide (H2S) as a protagonist to regulate metal stress in plants: an overview of physiological steps
(Springer, 2025) Pradeep Kumar Yadav; Arun Vishnu Kumar; Anita K. Singh
Hydrogen sulfide (H2S) is one of the gaseous molecules that act as a signaling agent at lower concentrations. It performs significant action in protecting the plants against adverse conditions by being part of the signaling network. In the current review, heavy metal stress has been considered as one of the major stress factors, as it affects the vital function of plants. The heavy metals also activate the expression of transcription factors and protein signaling pathways to regulate the expression of several stress-responsive genes. Further, H2S signaling triggers gene expression in the antioxidant defense system. Along with the endogenous level, the exogenous treatment with H2S up to a certain concentration maintains the redox balance and dynamic regulation of antioxidant enzyme systems to regulate the metal toxicity. It promotes more expression of chelators synthetic genes like PCS1, PCS2, MT1A, MT1B, and MT2B to produce more phytochelatins (PCs) and Metallothioneins (MTs), to scavenge the metals. H2S manages metal toxicity through various signaling processes by modulating extracellular signals into intracellular responses. The present review is based on the understanding of metal toxicity regulation with the intrusion of H2S signaling molecules. Overall, it will try to provide mechanistic action of H2S signaling on physiological performance and ultra-structure changes in the plant in order to regulate the metal stress. © The Author(s), under exclusive licence to Society for Plant Biochemistry and Biotechnology 2025.
Linear Model for Pore Pressure Predication in Gas Hydrate-bearing Sand Formation of Krishna-Godavari Basin (India) – A Case Study
(Geological Society of India, 2024) Pradeep Kumar Yadav; Uma Shankar
Pore pressure is a crucial geomechanical parameter, to decide the mud density while well drilling. The mud weight should be between formation pressure (pore pressure) and the fracture gradient of the reservoir rock, otherwise various kind of unwanted incidents like, kicks, blowout, breakout, well collapse, mud loss and lost circulation can happen; which can increase the cost of drilling and in worst case it may lead to a dangerous accident and consequently loss of life and assets at drilling site. In this study we are trying to find pore pressure within water bearing shale formations and gas hydrate (solid) bearing sand formation of four wells of Area B in the Krishna-Godavari Basin, namely, NGHP-02-17A, 19A, 22A, and 23A. Bower’s sonic, Eaton’s resistivity and Eaton’s sonic empirical equations have been used to estimate effective stress in the water-bearing shale formation. In gas hydrate-bearing sand formations these empirical equations cannot be useful for effective stress or pore pressure estimation and hence a linear model based on pressure-core data, relating effective stress and depth in meter below seafloor (mbsf) is generated. This model is applicable for the effective stress estimation in gas hydrate bearing sand formations of the Krishna-Godavari basin. The effective stress estimated from linear model and from core data are found in good agreement in all the wells. At site NGHP-02-23, in-situ pore-pressure was measured between depth of 270.38 to 271.38 mbsf with the help of modular dynamic formation tester (MDT) tool. The in-situ pore pressure (28.2 MPa) and estimated pore pressure (27.8 MPa) from the linear model are found in good agreement. Further, fracture pressures from Matthew-Kelly and Eaton’s method were estimated. The mud weight base on the reported mud density 1.3g/cc are found to higher than the pore pressures and lower than the fracture pressures and hence fulfil the criteria for safe drilling. © 2024 Geological Society of India, Bengaluru, India.
Mitigating cypermethrin stress in Amaranthus hybridus L.: Efficacy of foliar-applied salicylic acid on growth, enzyme activity, and metabolite profiles
(Elsevier B.V., 2024) Arun Kumar; Pradeep Kumar Yadav; Anita Singh
The study aimed to evaluate the role of foliar-applied salicylic acid (SA) (5-50 µM) in mitigating the effects of cypermethrin (CYP) stress on Amaranthus hybridus L., at its recommended (100 PPM) and double dose (200 PPM). CYP application at recommended dose proliferated the growth of the crop, while the double dose affected negatively. SA boosted the performance of the CYP-treated plants by reducing oxidative radical formation via increasing the activity of catalase, superoxide dismutase, peroxidase, ascorbate peroxidase, glutathione s-transferase, dehydroascorbate reductase, ascorbate, and proline. SA increased photosynthetic activity by increasing the leaf area, chlorophyll content and regulating the level of intracellular CO2, stomatal conductance, and transpiration in the CYP-treated plants. The fresh weight of the crop showed maximal increase with 10 µM SA (57 %) at recommended dose and with 20 µM SA (36.8 %) at double dose of CYP. Additionally, CYP residues showed maximum decline with 10 µM and 20 µM SA application in 100P and 200P plants, respectively. UHPLC-MS analysis showed increased levels of crucial secondary metabolites such as antheraxanthin, violaxanthin, kaempferol, rutin, cinnamic acid, ferulic acid, trigonelline, coumarin, scoparone, esculin, caryophyllene oxide, jasmonal with SA supplementation at 10 µM with 100P and at 20 µM with 200P treatments. The observed changes in enzyme activities, physiology and metabolite profiles underscore the potential of SA in mitigating pesticide-induced stress and enhancing plant growth and health. This study could further be explored in future by combining SA with other phytohormones and applying omics approaches could enhance crop resilience across diverse environments. © 2024
Modulations of functional traits of Spinacia oleracea plants exposed to cadmium stress by using H2S as an antidote: a regulatory mechanism
(Springer, 2023) Pradeep Kumar Yadav; Arun Kumar; Prashasti Pandey; Deepak Kumar; Anita Singh
The present study is based on the application of H2S as an exogenous antidote in Spinacia oleracea (spinach) plants grown in Cd-contaminated (50 ppm) soil. The different doses of H2S in the form of NaHS (10, 50, 100, 200, and 500 μM) have been applied as a foliar spray to regulate the physiological attributes under Cd toxicity. Over to control, the plants grown in Cd alone showed a reduction in the fresh biomass by 48% with more production of oxidative biomarkers (H2O2, SOR, and MDA content) and antioxidative enzymes (SOD, POD, APX, and GR). Further, with the exogenous application of H2S, among all the doses the fresh biomass was found to be maximally increased at 100 μM dose by 76%, and the Cd content was reduced significantly by 25% in the shoot compared to plants grown in Cd treated soil alone. With the decrease in Cd content in the shoot, the production of H2O2, SOR, and MDA content was reduced by 52%, 40%, and 38% respectively, at 100 μM compared to the plants grown in Cd-treated soil. The activities of estimated antioxidative enzymes showed a reduction in their activities up to 100 μM. Whereas, Glutathione reductase (GR) and Phytochelatins (PCs) showed different trends with their higher values in plants treated with NaHS in the presence of Cd. At 100 μM the GR and PCs, respectively showed 48% and 37% increment over Cd-treated plants alone. At this dose, the relative expression of SOD, POD, APX, GR, and PCS5 (Phytochelatin synthetase enzyme) genes, and other functional activities (SEM and fluorescence kinetics) supported the best performance of plants at 100 μM. Therefore, among all the doses, 100 μM dose of H2S has significantly reduced the Cd toxicity by maintaining the growth and other functional traits of plants. The correlation analysis also supported the result by showing a relationship between H2S application and Cd uptake. So, with this strategy, the plants grown in metal-contaminated fields can be improved qualitatively as well as quantitatively. With further experimentation, the mode of application could be explored to increase its efficiency and to promote this strategy at a wider scale. © 2023, Prof. H.S. Srivastava Foundation for Science and Society.
Mustard seeds derived fluorescent carbon quantum dots and their peroxidase-like activity for colorimetric detection of H 2 O 2 and ascorbic acid in a real sample
(Elsevier B.V., 2019) Subhash Chandra; Vikas Kumar Singh; Pradeep Kumar Yadav; Daraksha Bano; Vijay Kumar; Vinay Kumar Pandey; Mahe Talat; Syed Hadi Hasan
Herein, we were synthesized fluorescent carbon quantum dots via facile one-step hydrothermal treatment of mustard seeds (M-CQDs). It showed excellent optical property with fluorescent quantum yield 4.6%. The as-prepared M-CQDs exhibited peroxidase-like mimetic activity and catalyzed the oxidation of chromogenic substrate 3,3‘,5,5‘-tetramethylbenzidine (TMB) in the presence of H 2 O 2 to produce a blue color reaction mixture with the prominent peak at 652 nm. Furthermore, the peroxidase-like catalytic performance of M-CQDs followed the steady-state kinetics behavior and exhibited similar catalytic activity as that of natural enzyme Horseradish peroxidase (HRP). In addition to this, the double reciprocal plot showed a parallel line which suggested the occurrence of Ping-Pong type of mechanism. The H 2 O 2 dependent oxidation of TMB was helpful for the colorimetric detection of H 2 O 2 in the linear range of 0.02–0.20 mM with the limit of detection (LOD) of 0.015 mM. Interestingly, the oxidized TMB (ox-TMB) was further reduced to native TMB by the reducing agent ascorbic acid. Hence M-CQDs showed its potential towards the selective and sensitive detection of ascorbic acid in the linear range of 10–70 μM having a correlation coefficient of 0.998 with LOD of 3.26 μM. The practical feasibility of the proposed detection method of AA was also investigated in common fresh fruits. © 2018 Elsevier B.V.
Nitrogen doped fluorescent carbon quantum dots for on-off-on detection of Hg2+ and glutathione in aqueous medium: Live cell imaging and IMPLICATION logic gate operation
(Elsevier B.V., 2019) Vikas Kumar Singh; Virendra Singh; Pradeep Kumar Yadav; Subhash Chandra; Daraksha Bano; Biplob Koch; Mahe Talat; Syed Hadi Hasan
The present work describes the synthesis of N-CQDs via one step hydrothermal methods. The synthesized N-CQDs was fully characterized by TEM, P-XRD, FT-IR, XPS and Zeta sizer. It exhibited excitation independent emission behaviour with fluorescent quantum yield of 41% respect to quinine sulphate standard. The excellent optical properties of N-CQDs made it fluorescent probe for turn off detection of toxic heavy metal ion Hg2+ with good selectivity and sensitivity. The limit of detection was found to be 0.08 μM with correlation coefficient (R2 = 0.992). After addition of various reducing agent such as amino acid, EDTA and GSH in the quenched solution of N-CQDs + Hg2+, the fluorescence property was selectively recovered in the presence of GSH and hence the quenched solution further acts as selective turn on sensing of GSH up to lower limit of 2.0 μM with correlation coefficient (R2 = 0.996). The on-off-on sensing behaviour of N-CQDs was utilized for the implication of logic gate in absence and presence of Hg2+ and GSH to construct the molecular switches. The MTT assay of N-CQDs was performed on MCF-7 cancer cell line to check their applicability in biological system and the result showed negligible cytotoxicity and good permeability. The cell imaging on MCF-7 cells visualized in dichromic region (blue and green). Therefore, it could be smart material for sensing of heavy toxic metal as well as cell imaging application. © 2019 Elsevier B.V.
Nitrogen/sulfur-co-doped carbon quantum dots: a biocompatible material for the selective detection of picric acid in aqueous solution and living cells
(Springer, 2020) Subhash Chandra; Daraksha Bano; Priyadarshika Pradhan; Vikas Kumar Singh; Pradeep Kumar Yadav; Devanjan Sinha; Syed Hadi Hasan
Here, a fast and eco-friendly one-pot hydrothermal technique is utilized for the synthesis of nitrogen/sulfur-co-doped fluorescent carbon quantum dots (NS-CQDs) from a simple precursor of citric acid (CA) and thiosemicarbazide (TSC). The obtained NS-CQDs exhibited strong blue emission under UV light, with fluorescence quantum yield (QY) of ~37.8%. The Commission internationale de l’eclairage (CIE) coordinates originated at (0.15, 0.07), which confirmed the blue fluorescence of the synthesized NS-CQDs. Interestingly, the prepared NS-CQDs were successfully used as a selective nanoprobe for the monitoring of environmentally hazardous explosive picric acid (PA) in different nitro- and non-nitro-aromatic derivatives of PA. The mechanism of the NS-CQDs was also explored, and was posited to occur via the fluorescence resonance electron transfer (FRET) process and non-fluorescent complex formation. Importantly, this system possesses excellent biocompatibility and low cytotoxicity in HeLa cervical cancer cells; hence, it can potentially be used for PA detection in analytical, environmental, and pathological applications. Furthermore, the practical applicability of the proposed sensing system to pond water demonstrated the feasibility of our system along with good recovery. [Figure not available: see fulltext.] © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
Peroxidase mimetic activity of fluorescent NS-carbon quantum dots and their application in colorimetric detection of H2O2 and glutathione in human blood serum
(Royal Society of Chemistry, 2018) Vikas Kumar Singh; Pradeep Kumar Yadav; Subhash Chandra; Daraksha Bano; Mahe Talat; Syed Hadi Hasan
Interest is growing in the development of artificial enzymes to overcome the drawbacks of natural enzymes. Herein, we have synthesized nitrogen-sulphur dual-doped carbon quantum dots (NS-CQDs) via a one-step hydrothermal method; the NS-CQDs possess excellent optical properties and a high fluorescent quantum yield (46%). Significantly, the NS-CQDs exhibited peroxidase mimetic enzyme activity without support from metals or polymeric materials and efficiently catalyzed the oxidation of peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue solution with an absorption maximum at 652 nm. Mechanistic studies suggest that the small size and high electron density of NS-CQDs play vital roles and accelerate the reduction of H2O2 to generate OH radical, which facilitates the oxidation of TMB. The catalytic activity is based on Michaelis-Menten kinetic behavior, and steady state kinetic analysis suggests that the NS-CQDs exhibit a higher affinity for H2O2 than TMB, similar to the natural enzyme horseradish peroxidase (HRP). Moreover, the catalytic pathway follows a ping-pong mechanism. Therefore, these findings offer a worthy platform for colorimetric detection of H2O2 in a linear range of 0.02 mM to 0.1 mM with a limit of detection of 0.004 mM. Interestingly, the blue colour of oxidized TMB showed excellent selectivity over non-thiolate biological molecules, especially amino acids, and glutathione can be detected up to 0.07 μM via colorimetric and fluorimetric assays. Additionally, this system showed excellent recovery (96.0-108.3%) of GSH from human blood serum. Thus, the proposed sensing system is simple, convenient, and straightforward and can be potentially applied for real time monitoring of H2O2 and glutathione in biological samples. © 2018 The Royal Society of Chemistry.
Petro-physics Analysis and Rock Physics Modeling for Estimation of Gas Hydrate Saturation: A Case Study in the Mahanadi Offshore Basin
(Springer, 2022) Pradeep Kumar Shukla; Dip Kumar Singha; Pradeep Kumar Yadav; Kalachand Sain
Gas hydrate saturation (Sh) is the most challenging key parameter of petrophysical evaluations for reservoir characterization. In total three wells were used (namely, NGHP-01-19, NGHP-01-09, and NGHP-01-08) to compute the petrophysical parameters in the gas hydrate-bearing sediments of the Mahanadi offshore basin. Initially, effective porosity and volume of shale are computed using conventional log data varying from 11–36% and 55–75% respectively. The most prominent technique responding to the physical property has been used to compute the Sh by using Archie’s empirical electrical resistivity method. The presence of gas hydrate, free gas, and other lithology affects the sonic velocity which is widely used to quantify the hydrate saturation. Therefore, an attempt is made to quantify the Sh from the wellbore sonic velocity using a rock physics model at higher porosity (∼62%) for unconsolidated marine sediments below the seafloor. The model is best suited for gas hydrate zones where velocity increases with the hydrate saturation but underestimates the saturation for free gas zones below the bottom simulating reflector. In the study area, Sh ranges from 5–13% in the depth interval of 175–200 mbsf for well NGHP-01-19 whereas, small amount of 3–10% and 2–8% for well NGHP-01-09 and NGHP-01-08 respectively. The Sh obtained from the rock physics model is insignificantly mismatched with the saturation obtained from temperature and resistivity data due to the presence of an isotropic layer with fracture filling sediments having anisotropic properties. © 2022, Geological Society of India.