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FRET study between Carbon Quantum Dots and Malachite Green by Steady State and Time Resolved Fluorescence Spectroscopy
摘要： Background: Understanding the interaction between different organic dyes and carbon quantum dots helps us to understand several photo physical processes like electron transfer, energy transfer, molecular sensing, drug delivery and dye degradation processes etc. Objective: The primary objective of this study is to whether the carbon quantum dots can act as an electron donor and can participate in the different photo physical processes. Methods: In this work, carbon quantum dots (CQDLs) are synthesized in most economical and simple carbonization method where petals of Nelumbo nucifera L. are used as a carbon precursor. The synthesized CQDLs were characterized by using experimental techniques like UV?Vis absorption, FT-IR, transmission electron microscopy (TEM), steady-state and time-resolved fluorescence spectroscopy. Results: The spectral analysis shows that the so synthesized CQDLs are spherical in shape and its diameter is around 4.2 nm. It shows the fluorescence emission maximum at 495 nm with a quantum yield of 4%. In this work the interaction between carbon quantum dots (CQDLs) and an organic dye malachite green (MG) is studied using fluorescence spectroscopic technique under ambient pH condition (At pH 7). The quenching mechanism of CQDLs with MG was investigated using Stern-Volmer equation and time-resolved fluorescence lifetime studies. The results show that the dominant process of fluorescence quenching is attributed to Forster Resonance Energy Transfer (FRET) having a donor acceptor distance of 53 ? where CQDLs act as a donor and MG acts as an acceptor. Conclusion: This work has a consequence that CQDLs can be used as a donor species for different photo physical processes such as photovoltaic cell, Dye sensitized solar cell, and also for antioxidant activity study.
关键词： Carbon quantum dots,stern-volmer plot,Nelumbo nucifera L.,FRET,malachite green
更新于2025-09-19 17:13:59
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Bifurcation analysis of the propagation of femtosecond pulses for the Triki-Biswas equation in monomode optical fibers
摘要： Bifurcation analysis of the propagation of femtosecond pulses for the Triki–Biswas (TB) equation in monomode optical fibers is reported for the first time. Bifurcation of phase plots of the dynamical system is dispensed using phase plane analysis through symbolic computation. It is observed that the TB equation supports femtosecond solitary pulse, periodic pulse, superperiodic pulse, kink and anti-kink pulses, which are presented through time series plot numerically. Analytical forms of the femtosecond solitary pulses are obtained. This contribution may be applicable to interpret the dynamical behavior of various femtosecond pulses in monomode optical fibers beyond the Kerr limit.
关键词： dynamical system,superperiodic pulse,Solitary pulse,phase plot,periodic pulse
更新于2025-09-12 10:27:22
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One-point calibration of Saha-Boltzmann plot to improve accuracy and precision of quantitative analysis using laser-induced breakdown spectroscopy
摘要： Calibration-free laser-induced breakdown spectroscopy (CF-LIBS) has recently gained attention due to its potential to overcome matrix effects on quantitative analysis using LIBS. However, the efficiency of CF-LIBS may be compromised by uncertainties in the experimental and spectroscopic parameters. To minimize these uncertainties and improve quantitative analysis, the one-point calibration (OPC) method was recently introduced to empirically correct the emission line intensities in a Boltzmann plot. In this work, we used the OPC method on a Saha-Boltzmann plot to cover a large energy range and to obtain more precise and accurate plasma temperature and electron density (Ne) values than were obtained with a Boltzmann plot using OPC method. For the analysis, we prepared two sets of sodium chloride (NaCl) samples: one with graphite and another with calcium carbonate (CaCO3). We observed matrix effects when we evaluated the calibration curves of carbon line intensity as a function of carbon concentration. Corrections by the OPC method to the Boltzmann or Saha-Boltzmann plots minimized the matrix effects and also guaranteed that the calculated plasma temperature were the same for the primary elements of each sample, suggesting that they were in local thermodynamic equilibrium. When the OPC method was applied to the Saha-Boltzmann plot, we obtained an uncertainty of less than 0.5% for plasma temperature and Ne; an r2 value of 0.994; and a root mean square relative error (RMSRE) of 8% for C concentration. Meanwhile, the traditional OPC method resulted in an uncertainty of 2.3% for plasma temperature and Ne and a validation with r2 of 0.977 and RMSRE of 13% for C concentration. These results showed that the OPC method efficiently improved the quantitative analyses possible with the Saha-Boltzmann plot using CF-LIBS.
关键词： LIBS,Calibration-free model,One-point calibration,Electron density,Plasma temperature,Saha-Boltzmann plot
更新于2025-09-12 10:27:22
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Ovalbumin antibody-based fluorometric immunochromatographic lateral flow assay using CdSe/ZnS quantum dot beads as label for determination of?T-2 toxin
摘要： This work describes an anti-ovalbumin antibody-based lateral flow immunoassay (LFI) for T-2 toxin. The antibody uses a coating antigen as a bifunctional element for universality and introduces preincubation to improve the detection limits of the method. T-2 toxin and ovalbumin-modified T-2 toxin competitively binds on the anti-T-2 toxin monoclonal antibody modified on CdSe/ZnS quantum dot beads during preincubation. The modified T-2 toxin acts as a bifunctional element that forms immuno complexes during preincubation and combines with anti-ovalbumin antibody coated in the test line through the ovalbumin terminal. Fluorescence is detected at 610 nm on the test zone following photoexcitation at 365 nm. It has a reverse dose-effect relationship with the amount of T-2 toxin. The calibration plot is linear in the 20–110 fg mL?1 T-2 toxin concentration range, and the limit of detection (LOD) is 10 fg mL?1, which is lower by 8-fold than that of the traditional LFI system (LOD 80 fg mL?1) and one order of magnitude than those of LFIs with labels of colloidal gold nanoparticles (LOD 150 fg mL?1) or fluorophores (LOD 190 ng mL?1). Universality was verified through aflatoxin B1 detection using the established ovalbumin antibody-based LFI system (LOD 10 fg mL?1). The performance of the method was compared with that of established systems and a commercial ELISA kit (LOD 360 fg mL?1).
关键词： Fluorometry,Bifunctional element,Calibration plot,Sensitivity,Limit of detection,Aflatoxin B1,Preincubation
更新于2025-09-11 14:15:04
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Improvement in upconversion/downshifting luminescence of Gd2O3 :Ho3+/Yb3+ phosphor through Ca2+ / Zn2+ incorporation and optical thermometry studies
摘要： The Ho3+/Yb3+ doped Gd2O3 phosphor was synthesized via the hydrothermal process. Co-doping of Ca2+ and Zn2+ ions caused a change in the particle morphology and aggregation of the Ho3+/Yb3+: Gd2O3 phosphor. The structural characterization of these particles was performed using X-ray diffraction analysis, Fourier transforms infrared spectroscopy and scanning electron microscopy. The 980 nm excitation assisted upconversion luminescence and 449 nm excitation assisted downshifting luminescence of these phosphor particles were compared through the incorporation of Ca2+ and Zn2+ co-dopants. The co-dopants concentration was varied at 0, 5, 10, 15 and 20 mol %. The change in upconversion/downshifting luminescence under the influence of the optimized molar concentration of these co-dopants was studied and explained based on structural variations in the present phosphor material. The paramagnetic behavior of these particles was characterized and compared to search possible applications of these particles in the biomedical field. The samples were studied comparatively for temperature sensing.
关键词： Temperature sensing,Upconversion/Downshifting,Ca2+/Zn2+,M-H plot,Ho3+/Yb3+: Gd2O3
更新于2025-09-10 09:29:36
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Metal insulator transition driven by hydrated water of tungsten trioxide
摘要： Metallic nature to insulating nature transition (MIT) is found to occur in transition metal oxides and the study is of immense interest in materials research and condensed matter physics. Thermally stable layered orthorhombic WO30.33H2O having weak Van der Waals bonds between adjacent layers is synthesized by hydrothermal method. MIT is observed for the sample at a temperature of 343 K, by the method of dielectric relaxation spectroscopy (DRS). Multiple oxidation states of tungsten obtained from XPS in hydrated tungsten trioxide, caused by variation of oxygen vacancy is found to contribute to the transition. At the transition temperature there is breakage of hydrogen bond, simultaneously trapping the conduction electrons and liberating hydrogen ions for proton conduction. Intercalated water causes proton hoping by Grotthuss mechanism which scaffolds Mott transition and explain MIT in hydrated WO3.
关键词： Grotthuss mechanism,Mott theory,Arrhenious plot,Temperature dependent dielectric study,Hydrated WO3,Metallic to insulating nature transition
更新于2025-09-10 09:29:36
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X-ray Diffraction Line Profile Analysis of Undoped and Se-Doped SnS Thin Films Using Scherrer’s, Williamson–Hall and Size–Strain Plot Methods
摘要： An electrochemical route has been employed to prepare undoped and Se-doped SnS thin films. Six samples including undoped and Se-doped SnS thin films were deposited on the fluorine-doped tin oxide glass substrate. An aqueous solution containing 2 mM SnCl2 and 16 mM Na2S2O3 was used in the electrolyte. Different Se-doped SnS samples were prepared by adding the various amounts of 4 mM SeO2 solution into the electrolyte. The applied potential (E), time of deposition process (t), pH, and bath temperature (T) were kept at -1 V, 30 min, 2.1, and 60°C, respectively. After the completion of the deposition process, x-ray diffraction (XRD) and transmission electron microscopy (TEM) were utilized to characterize the deposited thin films. XRD patterns clearly showed that the synthesized undoped and Se-doped SnS thin films were crystallized in the orthorhombic structure. Using Scherrer’s method, the crystallite size of deposited thin films is calculated. In addition, the crystallite size and lattice strain have been estimated using the modified form of the Williamson–Hall (W–H) method containing a uniform deformation model, a uniform deformation stress model, a uniform deformation energy density model, and by the size–strain plot method (SSP). The shape of SnS crystals was spherical in TEM images. The results showed that there was a good agreement in the particle size obtained from the W–H method and the SSP method with TEM images.
关键词： thin films,Se-doped SnS,size–strain plot method,Line profile analysis,Williamson–Hall method
更新于2025-09-09 09:28:46
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How To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis Spectra
摘要： A misuse of the Tauc plot to determine the band gap energy of semiconductors may lead to erroneous estimates. Particularly large errors can be associated with characterization of modified semiconductors showing a significant absorption of sub-band gap energy photons. Taking the model methyl orange/titanium dioxide system, we address the problem and discuss how to apply the Tauc method correctly.
关键词： band gap energy,UV?Vis spectra,Tauc plot,methyl orange,modified semiconductors,titanium dioxide
更新于2025-09-09 09:28:46
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Effect of image processing constraints on the extent of rotational ambiguity in MCR-ALS of hyperspectral images
摘要： Hyperspectral imaging is a way to explore the spatial and spectral information of the different compounds in chemical or biological samples. In addition, multivariate curve resolution alternating least squares (MCR-ALS) can be used to extract this information based on the bilinearity assumption. However, it is well-known that using proper constraints can reduce the amount of uncertainty in the results of MCR, which is called rotational ambiguity. In MCR-ALS analysis of hyperspectral images, different image processing techniques, such as model fitting, image segmentation or sparse image recovery can be applied as spatial constraints. In this contribution, we aim to investigate how the use of these spatial constraints limits the extent of rotational ambiguity of MCR-ALS solutions. For this purpose, we evaluate the extent of rotational ambiguity and use Borgen plots to visualize it. We show on simulations and real hyperspectral imaging data that accuracy of the results is improved when spatial constraints are applied.
关键词： Borgen plot,Uncertainty,Area of feasible solutions,Spatial constraints,Multivariate Curve Resolution - Alternating Least Squares
更新于2025-09-09 09:28:46
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Fluorescent Chemosensor for Quantitation of Multiple Atmospheric Gases
摘要： Recently, the sensing and monitoring of gases from ambient as well as industrial sources has gained a great importance in order to ensure occupational hygiene, public health, and societal welfare. The development of new technologies for visualizing and detecting gases at trace levels is imperative for various applications. There exist several established traditional methods to detect different gases. In this article, we review the latest trends in the area of fluorescence sensing of gas molecules, which is a high sensitivity technique with minimum or negligible interferences. The gas sensors fabricated with the use of fluorescent nanoparticles as detecting elements possess special feature, like high surface-to-volume ratios, ultra sensitivity, enhanced selectivity, cost effectiveness, and fast response. The inherent properties of the related systems, e.g. a large fluorescence lifetime, nanoscale particle size and a tunable zeta potential, make it possible to devise fluorescent sensors with an attractive pathway of fluorescence ‘off–on’. Several fluorimetric methods are known to detect specific gases from the atmospheric gaseous samples with satisfactory detection results. Modern fluorescent gas sensors are did not cause interference from the co-pollutants thus making the fluorimetric sensing process to be quantitative as well as specific.
关键词： Atmospheric environmental sample,Fluorescent gas sensor,Job’s plot,Fluorescent organic nanoparticles,Analytical method,Fluorescence lifetime
更新于2025-09-04 15:30:14