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Photoluminescence enhancement <i>via</i> microwave irradiation of carbon quantum dots derived from solvothermal synthesis of <scp>l</scp> -arginine
摘要： Photoluminescence enhancement of carbon quantum dots was achieved via solvothermal synthesis followed by microwave irradiation. Nitrogen and phosphorous doped carbon quantum dots were prepared by solvothermal heating of L-arginine with phosphoric acid for 12 hours followed by microwave irradiation for 3 minutes. The photoluminescence enhancement was nearly two fold after microwave irradiation. The morphology, structure, and surface properties were the same for the solvothermal (CQDs-S) as well as after microwave (CQDs-M) irradiation. Thus, the enhancement is attributed to the decrease of surface defects within CQDs, which led to a decrease in the non-radiative transitions. The CQDs were quenched selectively by Fe3+ ions. The quenching led to the fabrication of the fluorescence probe for ferric ion determination. The CQDs-M had a low detection limit of 4.0 nM, while CQDs-S had a limit of 50 nM. This study gives a tool for enhancing photoluminescence quantum yields, which is highly desired for biosensing and bioimaging applications.
关键词： Photoluminescence enhancement,Fluorescence probe,Solvothermal synthesis,Ferric ion determination,Microwave irradiation,Carbon quantum dots
更新于2025-11-19 16:56:42
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Effect of microwave irradiation on the electrical and optical properties of SnO2 thin films
摘要： We report the electrical and optical characteristics of SnO2 thin films irradiated by microwaves (MWs) and grown using atomic layer deposition in a commercial MW oven operating at a frequency of 2.45 GHz. The properties of the MW-irradiated SnO2 thin films were compared with those of the as-deposited SnO2 thin films. After MW irradiation, the conductivity and transparency of the thin films were enhanced. In addition, the samples irradiated for 5 min showed optimal carrier concentration, Hall-mobility, resistivity, and transmittance values of 1.5 × 1020 cm-3, 4.6 cm2/V·s, 8 × 10-3 Ω·cm, and 95.77%, respectively. The improved properties of the MW-irradiated samples were attributed mainly to the formation of an oxygen vacancy in the SnO2 lattice during MW irradiation. Our results can be applied for the fabrication of pure SnO2-based transparent conductive oxides; these oxides are generally doped with other elements.
关键词： SnO2,Transparent Conductive Oxide,Microwave Irradiation,Electrical and Optical Properties
更新于2025-09-23 15:23:52
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Exfoliation of graphite as flexible SERS substrate with high dye adsorption capacity for Rhodamine 6G
摘要： Adsorption is one of the most important processes in wastewater treatment, especially for dye removal. In addition to adsorption, there must be a vigilant technique, such as Surface Enhanced Raman spectroscopy (SERS), for detection of low concentration of dye molecules to detect water foiling. Herein, we report a simple, low cost, rapid and e?cient technique for the production of exfoliated graphite (EG) under microwave irradiation at 800 W in 1 min, as excellent adsorption material for Rhodamine 6G (R6G) dye. The e?ect of adsorption process parameters such as pH, contact time, isotherm models (Langmuir and Freundlich) and kinetic models (pseudo-?rst and pseudo-second-order) on dye removal under aqueous solutions, were investigated. The maximum adsorption capacity for R6G dye is 212.72 ( ± 5.3) mg/g. Meanwhile compressing of EG, into a ?exible graphite sheet (FGS) demonstrates responsive SERS for R6G molecules up to detection limit of 10?7 mol/L. However, with silver nanoparticle incorporation, the detection limit increases up to 10?12 mol/L. Performance of ?exible sheet checked over a month by rubbing sheet through paper and cloth doesn’t have any impact on the synthesis of exfoliated graphite. Aging factor of the sheet also shows reproducible SERS spectra after a month. These are the highest reported values till today, for adsorption of R6G dye on Exfoliated graphite, with reasonable SERS detection.
关键词： Microwave irradiation,Flexible graphite sheet,Exfoliated graphite,SERS,Adsorption
更新于2025-09-23 15:22:29
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Detection of Ascorbic Acid Using Green Synthesized Carbon Quantum Dots
摘要： In this work, carbon quantum dots (CQDs) were synthesized by microwave irradiation and were electropolymerized on glassy carbon electrode (GCE) to establish an electrochemical sensor for the selective detection of ascorbic acid (AA). Electrochemical behaviors of the prepared sensor were investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Herein, two wide linear responses were obtained in ranges of 0.01-3 mM and 4-12 mM with a low detection limit of 10 μM to AA. High sensitivities (44.13 μA-1 μM-1 cm-2, 9.66 μA-1 μM-1 cm-2, respectively) corresponding to the linear ranges were also achieved. In addition, the electrochemical sensor exhibited good selectivity and robust anti-interference ability toward AA in the presence of dopamine (DA) and uric acid (UA). These results showed that this sensor can be used as a promising tool to detect AA in real complex systems.
关键词： electrochemical sensor,selective detection,ascorbic acid,carbon quantum dots,microwave irradiation
更新于2025-09-16 10:30:52
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One-Minute Synthesis of Size-Controlled Fucoidan-Gold Nanosystems: Antitumoral Activity and Dark Field Imaging
摘要： Gold nanoparticles (AuNPs) are one of the most studied nanosystems with great potential for biomedical applications, including cancer therapy. Although some gold‐based systems have been described, the use of green and faster methods that allow the control of their properties is of prime importance. Thus, the present study reports a one‐minute microwave‐assisted synthesis of fucoidan‐coated AuNPs with controllable size and high antitumoral activity. The NPs were synthesized using a fucoidan‐enriched fraction extracted from Fucus vesiculosus, as the reducing and capping agent. The ensuing monodispersed and spherical NPs exhibit tiny diameters between 5.8 and 13.4 nm for concentrations of fucoidan between 0.5 and 0.05% (w/v), respectively, as excellent colloidal stability in distinct solutions and culture media. Furthermore, the NPs present antitumoral activity against three human tumor cell lines (MNT‐1, HepG2, and MG‐63), and flow cytometry in combination with dark‐field imaging confirmed the cellular uptake of NPs by MG‐63 cell line.
关键词： gold nanoparticles,microwave irradiation,darkfield imaging,antitumoral activity,fucoidan
更新于2025-09-16 10:30:52
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Preparation of reduced Graphene Oxide (rGO) assisted by microwave irradiation and hydrothermal for reduction methods
摘要： Graphite is a natural carbon source that can be used for graphene synthesis because of its abundant availability and relatively low cost. In this research, Graphene Oxide (GO) and reduced Graphene Oxide (rGO) have been prepared through modified Hummers method that uses microwave irradiation and hydrothermal process as reduction methods. This research can be divided into two main steps, i.e. preparation of GO and preparation of rGO. The preparation of GO was done using modified Hummers method that refers to graphite powder oxidation for five days. Then, preparation of rGO was done using two methods, i.e. microwave irradiation for 8 minutes at 1,000 watts and hydrothermal process for 10 hours at 200°C. The characterization of the samples was observed by Fourier-Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Ultraviolet-Visible Spectroscopy (UV-Vis). XRD pattern of GO sample shows a peak at 2θ = 10.63°, rGO sample from hydrothermal process at 2θ = 25.94°, and rGO sample from microwave irradiation method at 2θ = 25.94° with low intensity and at 2θ = 10.63° that indicates the presence of GO. IR spectroscopy data shows an absorption peak of aromatic C=C at 1,573 cm-1 that indicates rGO formation. SEM images of GO illustrates a structure of stacked flakes. While the morphology of rGO has a structure of stacked flakes that is more transparent than GO. According to UV-Vis spectroscopy, GO and rGO of samples show absorption peak at λmax = 225 nm and λmax = 274 nm, respectively, which indicates π→π* transition of aromatic C=C bond. Based on the results of this study, the preparation of rGO using modified Hummers that combined with hydrothermal reduction method is more effective than microwave irradiation reduction method.
关键词： Graphene Oxide,hydrothermal process,Hummers method,reduced Graphene Oxide,microwave irradiation
更新于2025-09-04 15:30:14