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Fluorescent detection of Pb2+ pollutant in water samples with the help of Delonix regia leaf-derived CQDs
Heavy metals released from different sources into water bodies are a major concern in the view of environmental protection. Their non-biodegradability and the numerous health hazards add to the issue. Scientists worldwide have emphasized the issue and are trying to resolve it by different means. Among all the methods, the fluorescent method stands out for its simplicity and rapid results. Here, the study focuses on the development of an efficient and sustainable method for the detection of lead in waste-water effluents. Carbon quantum dots (GCDs), a highly non-toxic substance developed from Delonix regia leaves for the purpose via a simple hydrothermal method. The prepared GCDs exhibited good photostability and water solubility; they also displayed a bright red emission when irradiated with ultraviolet (UV) light. Here, the authors propose the synthesized GCDs as an effective fluorescent probe for sensitive detection of lead ions in aqueous samples. Photoluminescence quenching of GCDs by the addition of lead was studied and a good detection limit of 3.3 nM with a linear range of 10180 M was achieved. Further, real sample analysis was also conducted to prove the applicability of the synthesized GCDs. 2022 Elsevier B.V. -
Boosting Surface Coverage of CO Intermediates through Multimetallic Interface Interactions for Efficient CO2 Electrochemical Reduction
Given the inherent challenges of the CO2 electroreduction (CO2ER) reaction, solely from CO2 and H2O, it is desirable to develop selective product formation pathways. This can be achieved by designing multimetallic nanocomposites that provide optimal CO coverage, allowing for tunability in the product formation. In this work, Ag and Zn codoped-SrTiO3 (ZAST) composite immobilized carbon black (CB)-modified GCE working electrode (ZAST@CB/GCE) was developed for the electrochemical conversion of CO2 to multicarbon products. The complete reaction was carried out in a CO2-saturated aqueous system of 0.5 M KHCO3 electrolyte. A potential-dependent product selectivity was suggested based on the NMR results, wherein raising the potential value enhanced the formation of liquid products such as acetone and alcohols while suppressing competitive HER. The total Faradaic efficiency for liquid products reached an impressive 97% at a potential of ?0.6 V vs. RHE. This represents a significant advancement in acetone production pathways and valorization of CO2ER technology. 2025 American Chemical Society. -
Temperature-induced variations in the structural, morphological and optical features of cobalt oxide nanoparticles synthesized via hydrothermal method
Cobalt oxide is a promising material that attracts the researchers to find its application in various fields like catalysts, dielectric applications, gas sensors and electronics devices, etc. In this work, we investigated the effect of temperature in the structural, elemental, morphological and optical properties of Co3O4 nanoparticles synthesized by hydrothermal method. The as-prepared and annealed samples were observed for their structural and optical properties. The structural analysis and micro-strain effects of Co3O4 nanoparticles with cubic spinel structure were carried out through X-ray diffraction (XRD) studies. The crystallite size of as-prepared and annealed samples were around 27 nm and 29 nm, respectively. Raman spectrum showed the lattice vibrations of both oxidation states of cobalt oxide nanoparticles. Elemental analysis were observed through X-ray photoelectron spectroscopy (XPS). The morphology and chemical composition of the samples were determined from the field emission scanning electron microscope (FESEM) image and energy dispersive X-ray spectroscopy (EDAX). Moreover, the internal structure of both samples were compared through transmission electron microscopic (TEM) studies. The optical studies were done using the absorption spectrum and photoluminescence spectroscopy. Two direct band gaps (1.8 and 3.2 eV) were observed in the as-prepared, which got red-shifted on annealing (1.7 and 2.5 eV) due to size effects. The charge transfer process in two oxidation states of cobalt oxide could be identified from these bandgaps. Emission peaks in the photoluminescence spectrum of samples are due to the recombination of free-excitons and point defects in the crystal lattice. 2024 -
Electrochemical characteristics of Co3O4 nanoparticles synthesized via the hydrothermal approach for supercapacitor applications
Cobalt oxide (Co3O4), a transition metal oxide known for its favourable capacitive properties and surface characteristics, is a promising candidate for electrode materials in supercapacitive energy storage applications. This study presents a comprehensive analysis of cobalt oxide nanoparticles synthesized through the hydrothermal method at varying synthesis temperatures, focusing on their structural, optical, electrochemical, and surface properties. X-ray diffraction analysis confirmed the cubic spinel structure of Co3O4, while Raman spectroscopy verified the phase composition of the nanoparticles. X-ray photoelectron spectroscopy offered insights into the near-surface chemistry of the synthesized material. The study determined two direct bandgaps of Co3O4 through absorption spectra and Tauc plots. To assess surface morphology and particle size distribution, field-emitting scanning electron microscopy and transmission electron microscopy were employed. Electrochemical investigations involved cyclic voltammetry and Nyquist plots, while galvanostatic chargedischarge tests demonstrated a specific capacitance (Csp) of 450 Fg?1 at 1 Ag?1. Impedance analysis indicated favourable capacitive behaviour with low charge transfer resistance. Furthermore, the study observed cyclic stability with a capacitive retention rate exceeding 88% at a current density of 20 Ag?1 over 10,000 cycles. The paper also discusses the capacitive and diffusion-controlled charge storage mechanisms at lower scan rates, emphasizing the potential of Co3O4 nanoparticles as the electrode material in the development of supercapacitor devices. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2023. -
Symmetric supercapacitor based on Co3O4 nanoparticles with an improved specific capacitance and energy density
Metal oxides have garnered significant research interest as highly effective electrode materials for supercapacitors. In this study, we synthesized Co3O4, an electrode material for supercapacitors, utilizing an in-situ hydrothermal method with varying pH levels in the precursor solution. The obtained samples underwent through structural, optical, surface morphological, electrical, and electrochemical analyses, affirming their exceptional suitability for supercapacitor applications. The influence of pH fluctuations in the synthesis process, on the specific capacitance values were analyzed. The X-ray diffraction pattern and Raman spectrum confirmed the normal cubic spinel structure of Co3O4 nanoparticles. The X-ray photoelectron spectrum revealed the chemical bond states of Co3O4. The optical bandgap have been investigated from the Tauc plot. The surface area and morphology were determined through Brunauer Emmett and Teller method and field emission scanning electron microscope images. A high specific capacitance of 1195.05 Fg?1 at a current density of 1.5 Ag?1 was obtained in the three-electrode study for the sample synthesized at a pH of 10. A symmetric supercapacitor (SSC) device was fabricated to facilitate practical analysis. The symmetric supercapacitor device demonstrated a notably elevated specific capacitance of 870.6 Fg?1 at an operational current density of 5 Ag?1, concurrently achieving an enhanced energy density of 77.3 W h/kg and superior power density of 1997.7 W/kg. These performance metrics surpassed those of prior studies in the field. Furthermore, the SSC device exhibited an excellent cyclic stability of 88 % after undergoing 970 charge/discharge cycles. As a result, Co3O4 emerges as a promising and efficient electrode material for applications in supercapacitors. 2024 Elsevier Ltd -
The mathematical and machine learning models to forecast the COVID-19 outbreaks in Bangladesh
The COVID-19 virus mutates in many different variants after its outbreak. Although several vaccines have been developed by many countries and implemented worldwide, it is difficult to prevent the outbreaks due to the pops out of different variants from its regular mutations. This study is an attempt to develop models which could precisely forecast the COVID-19 outbreaks in Bangladesh. In this study, we have developed a SEIRD based machine learning model to forecast the next possible one year outbreaks scenario in this country. We have tested the accuracy of this model by fitting the results with the considered historical data from March 08, 2020 to October 14, 2021. Also, we have validated this model by predicting the future inside the existing dataset, which is almost similar to the real dataset. It is observed that the final future forecasting results are very realistic compared to the current outbreak situation. Additionally, we have shown that the classical SEIRD model cannot predict the COVID-19 future outbreaks even it does not fit with the real datasets of outbreaks. Moreover, another machine learning time series forecasting model, FBProphet, has been implemented to forecast the future outbreaks of Bangladesh. Finally, we have analyzed and compared the forecasting results and hence identify the limitations of the proposed models which can improve future research in this field. 2022 Taru Publications. -
Hepatoprotective activity of Peltophorum pterocarpum leaf and bark in the isoniazid and rifampicin-induced hepatotoxic rats
Background: In recent years, various phytomedicines have been used in the treatment of hepatic disorders. The aim of this study is to find out whether Peltophorum pterocarpum bark and leaves can help rats that have been exposed to isoniazid and rifampicin-induced hepatotoxicity. Materials and Methods: The rats were divided into 10 groups each with 6 rats. The liver damage is induced by isoniazid and rifampicin. The leaf and bark of P. pterocarpum extracted with ethanol are freshly mixed in sterile water (100, 200 and 400 mg/kg body weight), and given to rats orally in the early morning as a single dosage per day until the study period. The animals were sacrificed and the tissue and serum samples were collected for further investigations. Results: The liver damage induced by isoniazid and rifampicin altered the various biochemical parameters levels, but after the treatment of P. pterocarpum barks and leaves the levels were significantly altered when compared to the negative control rats. The drug silymarin was used as a standard. Conclusion: The extracts have the protective effect of liver markers and membrane-bound enzymes against the toxin-treated rats. This result highlights the hepatoprotective properties of the leaves and barks of the plant in a similar manner and the formulation (Group 10) have high beneficial effects than other groups. 2024 -
Drill hole surface characterisation of hybrid FRP laminates through statistical analysis
As it is known that the hybrid Fibre Reinforced Polymer (FRP) composite laminate is a recently evolved class of structural material. Hence, the present work deals with secondary processing ability like hole drilling on hard to machine FRP laminate. The influence of drilling attributes on the delamination factor and surface roughness contours are studied for a high thickness hybrid (carbon/glass FRP) laminates. Here, the experimentation was performed utilising Taguchis L27 design of experiments array. Later, on post-drilling, the predominant and optimum variables were studied through taguchi and variance analysis to highlight their contribution on the response functions. Taguchi results indicate that the combination of the 90?tungsten carbide tool, speed of 800 rpm, and rate of feed 50 mm/min gives the best performance concerning the delamination. Also, it was observed that the combination of the 118?tungsten carbide tool, cutting speed of 900 rpm and the rate of feed 60 mm/min give the best performance concerning surface roughness. Whereas, as per ANOVA, the highest percentage contribution factor was concerned to a tool material followed by other factors and analysed data lie with the confidence level of 95%. The work also indicates that tungsten carbide tool yield better results compared to high-speed steel tool. Further, fibre morphology has been studied, which indicates optimal structure with minimal damage. 2020 Engineers Australia. -
CONVECTIVE INSTABILITY IN POROUS MEDIA: IMPACT OF CHEMICAL REACTION ON MAXWELL-CATTANEO COUPLE-STRESS FERROMAGNETIC FLUIDS; [??????????? ??????????? ? ???????? ???????????: ????? ???????? ??????? ?? ?????????? ??? ?????????-???????? ? ????????????? ???????]
The current study analyzes the initiation of convection in a Maxwell-Cattaneo couple-stress ferrofluid within a porous layer, considering the effects of a chemical reaction. Small perturbations are applied to the fluid under the assumption of a zero-order energy release chemical reaction. The system is cooled from the upper layer while maintaining a steady temperature at the lower boundary. We employed linear stability analysis and determined Rayleigh number using the Galerkin Method (GM). This study emphasizes the influence of magnetic, chemical, Maxwell-Cattaneo, and couple-stress parameters on the initiation of ferro-convection. The findings indicate that both magnetic and chemical reaction parameters hasten the initiation of ferro-convection, while the porous medium and couple-stress parameters have a stabilizing effect. Notably, it is demonstrated that the destabilizing effects of chemical reactions and magnetic stresses can be effectively regulated in the presence of couple-stresses. The solutions provide insights into the potential application of ferromagnetic fluids for controlling efficient heat transfer mechanisms. 2024 Oles Honchar Dnipro National University. -
COUPLE STRESS EFFECT ON FERRO-CONVECTION TRIGGERED BY CHEMICAL REACTION IN A POROUS LAYER WITH SPARSE DISTRIBUTION; [????? ??????? ?????????? ?? ?????????????, ??????????? ???????? ???????? ? ????????? ???? ? ??????????? ??????????]
The study delves into the impact of couple stress on the commencement of convection in a porous material oriented horizontally. This layer contains a chemically reactive ferromagnetic fluid and experiences bottom heating. The investigation utilizes small perturbation methodology to explore and understand the impact of couple stress on the initiation of convection in this specific system. With the assumption of a non-autocatalytic exothermic reaction, eigenvalues are determined utilizing the Galerkin method. The analysis explores the effects of magnetic and couple stress parameters, as well as the Frank-Kamenetskii number. The observation indicates that the acceleration of the onset of ferroconvection is influenced by both magnetic forces and chemical reactions. Simultaneously, the presence of the couple stress component serves to stabilize the system. Moreover, when the nonlinearity of magnetization is sufficiently pronounced, the destabilization of the fluid layer is observed to be marginal. 2024 Oles Honchar Dnipro National University; -
Post listing IPO returns and performance in India: An empirical investigation
Objectives: (a) To analyse the performance of Indian IPOs in the short term. (b) To determine the significance of abnormal return of the IPOs. (c) To study the impact of over-subscription, profit after tax, promoters' holdings, issue price and market returns on IPO performance. Design/ Methodology/Approach: This research paper is based on empirical analysis. All the 52 IPO's listed in the NSE (National Stock Exchange, India) during the year 2018 to 2020 were considered for the study. The study is based on secondary data. The daily share price and Nifty-50 index value were taken from NSE website (www.nseindia.com) and other relevant data from red-herring prospectus of the respective company. The research / statistical tools used are: Market adjusted short run performance model, Wealth relative model, 't' test and regression analysis. Scope of the study: The scope of the study is limited to the IPO's listed only in the National Stock Exchange (NSE), India. Period of study: The study covers a period from January 2018 to December, 2020. Limitation of the study: The study considers only the influence of the external factors on the performance of IPOs. Findings: The average IPO return on the first trading day is 13.52%, ranging from -23.15% to 82.16% with standard deviation of 26.72%. The average IPO return on the third trading day was the highest and is found to be14.52%, ranging from -19.22% to 117.55% with standard deviation of 18.57%. The analysis reveals that the over subscription impacts the IPO performance and the other factors namely, issue price, Profit after Tax, market returns and promoters holdings do not influence IPO returns. Originality / Value: This is an original work that analyses the listing gain or loss and the post listing performance of IPO's in India and other factors that might influence the listing gain or loss. Copyright 2021. T. Ramesh Chandra Babu and Aaron Ethan Charles Dsouza. Distributed under Creative Commons Attribution 4.0 International CC-BY 4.0 -
Fluorescent detection of Pb2+ pollutant in water samples with the help of Delonix regia leaf-derived CQDs /
Synthetic Metals, Vol.291, ISSN No: 0379-6779.
Heavy metals released from different sources into water bodies are a major concern in the view of environmental protection. Their non-biodegradability and the numerous health hazards add to the issue. Scientists worldwide have emphasized the issue and are trying to resolve it by different means. Among all the methods, the fluorescent method stands out for its simplicity and rapid results. Here, the study focuses on the development of an efficient and sustainable method for the detection of lead in waste-water effluents. Carbon quantum dots (GCDs), a highly non-toxic substance developed from <em>Delonix regia</em> leaves for the purpose via a simple hydrothermal method. -
Surface modulation and structural engineering of graphitic carbon nitride for electrochemical sensing applications /
Journal of Nanostructure in Chemistry, Vol.12, Issue 5, ISSN No: 2193-8865.
The rediscovery of the old-age material graphitic carbon nitride (g-C3N4), a 2D conducting polymer, has given rise to a tide of articles exploring its diverse applications. Recently, owing to its excellent physicochemical stability and tunable electronic structure, the material has proven to be an eminent candidate for improving the sensing quality of electrodes. Excellent properties of g-C3N4 such as exposed surface area, metal-free characteristics, and low-cost synthesis have attracted facile and economical designing of sensors for a variety of analyte molecules. Herein, the readers are introduced to the historical development of g-C3N4 and escorted to the present findings of its electrochemical sensing applications. Along with its sensing utilities, the review shares some exciting insights into the synthesis, structural, and surface chemistry modulations of g-C3N4. -
Photoresponse and electrochemical behaviour of azobenzene anchored graphene oxide for energy storage application
Solar energy is considered to be a renewable source of energy that is intrinsically more sustainable than fossil fuels. Developing photoactive hybrid materials to store solar energy has recently received much attention. Herein, a photoactive molecule-graphene oxide hybrid was synthesized and characterized systematically. The solar energy storage performances of the hybrids were studied using various photophysical studies. The energy density and power density of the hybrid materials were 47 WhKg?1 and 156.6 WKg-1 respectively which showed 3 fold higher than the pristine compound. The photoelectrochemical behaviour of the hybrid were also studied using Cyclic voltammetry and Electrochemical impedance spectroscopy (EIS). Results showed the electrochemical performances can be varied due to their changing conformations from trans-to-cis isomerization. This work enables the research community in developing a promising material for solar thermal fuels as well as in energy storage devices. 2023 Elsevier B.V. -
Capacitive Behaviour of Imidazole Azo Modified Carbon Nanotubes/Polypyrrole Composite in Aqueous Electrolytes
Here, we reported imidazole azo (Im) modified carbon nanotubes (CNT) grafted polypyrrole (PPy) via the chemical oxidation method. The synthesized hybrid material has shown a unique structure consisting of carbon nanotubes with a conductive network via polypyrrole. The presence of Im derivatives has helped CNTs to enhance their electrochemical performances. The as synthesized composite was characterized using various techniques like FT-IR, XRD, XPS, and Raman spectroscopy. The morphological studies were performed using SEM technique which also confirmed the nature of the composite. The electrochemical performances of the electrode material were investigated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy in various electrolytes. The best performance of the electrode material was observed in 1 M H2SO4 with a specific capacitance of 305 F g?1 at a current density of 1 A g?1. The electrode material also showed a coulombic efficiency of 96% even after 5000 cycles. 2023 The Electrochemical Society (ECS). Published on behalf of ECS by IOP Publishing Limited. -
Azopyridine as a Linker Molecule in Polyaniline-Grafted Graphene Oxide Nanocomposite Electrodes for Asymmetric Supercapacitors
Electronically conducting polymers (ECPs)/carbon nanomaterial-based polyaniline electrodes have received great interest in the field of supercapacitors due to their high specific capacitance, good electronic conductivity, good mechanical strength, good chemical and electrochemical stabilities, etc. Among the various available ECPs, they have received much importance due to their excellent electrochemical performances. Herein, we report a facile synthesis of a PANI-grafted graphene oxide (GO)-azopyridine (Azo) (PANI/GO-Azo) nanocomposite and use it as electrodes for fabricating supercapacitors. The azo units present in the nanocomposite act as a spacer between PANI and GO. The interfacial polymerization method is adopted for the synthesis of PANI/GO-Azo nanocomposites. The PANI/GO-Azo nanocomposite electrode exhibits a gravimetric capacitance of 426 F g-1 at a current density of 0.25 A g-1 in 1 M H2SO4 (aqueous) electrolyte. The electrode possesses good cycling stability of more than 5000 cycles with a Coulombic efficiency of 98.5%. An asymmetric supercapacitor fabricated with PANI/GO-Azo as the positive electrode and activated carbon as the negative electrode delivers an energy density of 12.45 W h kg-1 with a power density of 274.9 W kg-1. This study proclaims that the PANI/GO-Azo nanocomposite electrode is highly promising for next-generation supercapacitors. 2023 American Chemical Society -
Strategically designed multiwalled carbon nanotube/bismuth ferrite/polyaniline nanocomposites and unlocking their potential for advanced supercapacitors
Bismuth ferrite (BF) serves a potential electrode-active material due to its peculiar characteristics such as wide voltage window and high specific capacitance, excellent stability, facile synthesis routes, etc. to name a few. Herein we report the strategic design and facile synthesis of multiwalled carbon nanotubes (MWCNT)/BF/polyaniline (PANI) nanocomposites, particularly for application in advanced supercapacitors. The MWCNT/BF/PANI nanocomposite architecture is a strategic design in which the maximum available surface area is utilized for the electrode nanostructure with increased porosity that allows easy movement of electrolyte-ions through it. The uniform arrangement of BF on MWCNTs helps in mitigating the possible agglomeration, further augmenting the surface area for an enhanced charge storage. The strategic layout of PANI on BF-decorated MWCNTs has given a coral-like structure for the nanocomposite electrode which significantly increased the surface area, reduced ion pathways and facilitating better access to electrolytic K+ ions. The MWCNT/BF/PANI nanocomposite electrode exhibits a specific capacitance of 3640 F g?1 at a current density of 5 A g?1. The innovative design as well as the synergy between the individual components of the nanocomposite electrode play a pivotal role in attaining the enhanced electrochemical performance. 2024 Elsevier B.V. -
One-pot hydrothermal synthesis of MWCNTs/NiS/graphitic carbon nitride as next generation asymmetric supercapacitors
Fabricating new electrode materials with high capacitive properties is crucial in contemporary research. The construction of hybrid supercapacitors developed using transition metal-sulfides and carbonaceous materials provides significant surface area and distinctive charge storage characteristics. In the present work, NH2-multiwalled carbon nanotubes/NiS/g-C3N4 (MNG) hybrid was synthesized by a one-pot hydrothermal method, and pristine g-C3N4 using thermal method. The morphological studies of the hybrid materials show the presence of tube like MWCNTs, sphere-like NiS, and sheet like g-C3N4. The uniform distribution of all the components in the hybrid helps in exhibiting excellent electrochemical performances. The prepared electrode material shows a specific capacitance of 2432 F g?1 at a current density of 4 A g?1. Furthermore, following a series of 10,000 cycling tests, the hybrid ternary composite retains 98 % of its initial capacitance. An asymmetric coin cell of MNG//AC was fabricated with an exceptional energy density of 73.3 Wh kg?1 and a power density of 1599.2 W kg?1. This remarkable rate performance and cycle stability exhibited by the material indicate its potential as a highly efficient electrode material for supercapacitors. 2024 Elsevier B.V. -
Hybrid architecture of Multiwalled carbon nanotubes/nickel sulphide/polypyrrole electrodes for supercapacitor
A hybrid electrode structure consisting of amino functionalised multi-walled carbon nanotube, nickel sulphide, and polypyrrole is successfully synthesized using a two-step synthesis such as hydrothermal and in-situ polymerization method. The resulting MWCNT/NiS/PPy composite exhibits a distinct tube-in-tube morphology with excellent stratification. The combination of different components and the unique structure of the composite contribute to its impressive specific capacitance of 1755 F g?1 at 3 A g?1. The prepared ternary composite enables ample exposure of numerous active sites while improving structural stability, ultimately leading to enhanced energy storage capabilities. They do this by combining the advantages of constituent components, a hierarchical assembly approach, and an integrated composite structure. Furthermore, even after undergoing 10,000 charge-discharge cycles, the supercapacitor retains more than 97% of columbic efficiency. An asymmetric coin cell was fabricated using MWCNT/NiS/PPy//AC device which delivered an energy density and power density of 33.12 Wh Kg?1 and 6750 W kg?1 respectively. These findings highlight the exceptional potential of the fabricated device for future applications in hybrid energy storage systems. 2024 Elsevier Ltd -
Analysis of unsteady flow of blood conveying iron oxide nanoparticles on melting surface due to free convection using Casson model
Iron oxide nanoparticles have great importance in future biomedical applications because of their intrinsic properties, such as low toxicity, colloidal stability, and surface engineering capability. So, blood containing iron oxide nanoparticles are used in biomedical sciences as contrast agents following intravenous administration. The current problem deals with an analysis of the melting heat transfer of blood consisting iron nanoparticles in the existence of free convection. The principal equations of the problem are extremely nonlinear partial differential equations which transmute into a set of nonlinear ordinary differential equations by applying proper similarity transformations. The acquired similarity equalities are then solved numerically by Runge-Kutta Felhsberg 45th-order method. The results acquired are on the same level with past available results. Some noteworthy findings of the study are: the rate of heat transfer increases as the Casson parameter increases and also found that the temperature of the blood can be controlled by increasing or decreasing the Prandtl number. Hence, we conclude that flow and heat transfer of blood have significant clinical importance during the stages where the blood flow needs to be checked (surgery) and the heat transfer rate must be controlled (therapy). 2020 Wiley Periodicals LLC