Enhanced photocatalytic activity of N, P, co-doped carbon quantum dots: an insight from experimental and computational approach

Herein, we demonstrate the single-step microwave radiation assisted approach to develop Nitrogen (N) and Phosphorous (P) co-doped carbon quantum dots (NP-CQD). The developed NP-CQD showed enhancement in visible light photocatalytic activity towards methylene blue dye degradation than that of N-CQD and P-CQD due to creation of energy states and reduced work function as estimated by Ultraviolet photoelectron spectroscopy and corroborated by first-principles Density Functional Theory (DFT) calculations

Polymer-wrapped reduced graphene oxide/nickel cobalt ferrite nanocomposites as tertiary hybrid supercapacitors: insights from experiment and simulation

The tertiary hybrid supercapacitor consisting of PEDOT:PSS wrapped reduced graphene oxide/Ni0.5Co0.5Fe2O4 (PGNC) was developed and its supercapacitance performance has been compared with that of the reduced graphene oxide (rGO)/Ni0.5Co0.5Fe2O4 (GNC), carbon nanotube (CNT)/Ni0.5Co0.5Fe2O4 (CNC) and carbon nanotube/reduced graphene oxide/Ni0.5Co0.5Fe2O4 (CGNC). Among all, PGNC exhibits an excellent specific capacitance of 1286 Fg−1 with a capacitance retention of 95% over 6000 cycles at a current density of 0.5 Ag−1. The synergetic effects between rGO, Ni0.5Co0.5Fe2O4 and the PEDOT:PSS polymer result in an increase in the specific surface area and the pore volume, making PGNC an excellent hybrid supercapacitor for energy storage. The enhancement in the specific capacitance of the PGNC nanocomposite is further validated through first-principles density functional theory calculations, which predict an increment in the density of states at the Fermi level of the GNC and CNC nanocomposites compared to the isolated Ni0.5Co0.5Fe2O4 material. The supercapacitance performance of the PGNC nanocomposite is reported for different electrolytes, different stoichiometric ratios of Ni and Co in NixCo1-xFe2O4 and on different substrates

Thermoluminescence, photoluminescence and optically stimulated luminescence characteristics of CaSO4:Eu phosphor: experimental and density functional theory (DFT) investigations

The CaSO4:Eu phosphor in nanocrystalline form was obtained by chemical method. The sample was annealed at various temperatures and quenched. The structural, electronic and optical properties are studied using various experimental techniques. As synthesized CaSO4:Eu particles have nanorod shapes with diameter of ~15 nm and length of ~250 nm. After annealing (at around 900 °C) a significant increase in their size (~2–4 μm) with phase transformation from hexagonal to orthorhombic was observed. Thermoluminescence (TL) and optically stimulated luminescence (OSL) intensities were found to increase with temperature up to 900 °C and decrease thereafter for 1 Gy of test dose of β-rays from 90Sr-90Yr source. However, the maximum OSL sensitivity was found to be more than that of CaSO4:Eu microcrystalline phosphor (prepared by acid recrystallization method) contrary to the usually found in the literature but much less than that of commercially available α-Al2O3:C phosphor. The activation energy for thermally assisted OSL process was found to be 0.0572 ± 0.0028 eV. The dose ranges of TL and OSL response was found from 0.04 Gy to 100 Gy and 0.02 Gy–100 Gy, respectively. The experimental results are also correlated with computational calculations based on density functional theory (DFT). The crystal structures and electronic structures of both hexagonal and orthorhombic CaSO4 and CaSO4:Eu materials show that they are direct band gap (5.67–5.86 eV) insulators, with Ca2+ substitution by Eu2+ found to introduce donor states in the band gap near Fermi level and the valence band edge of CaSO4 on doping with Eu2+ impurity ions

Experimental and computational studies of sonochemical assisted anchoring of carbon quantum dots on reduced graphene oxide sheets towards the photocatalytic activity

Herein, carbon quantum dots (CQDs) are anchored on reduced graphene oxide (rGO) sheets by sonochemical assisted method. The developed carbon quantum dots/reduced graphene oxide (CQDs/rGO) catalyst shows enhancement in the photocatalytic degradation of methylene blue and methyl orange under visible light compared to that of individual CQDs and rGO components. The improved performance of the CQDs/rGO catalyst has been attributed to efficient separation of photogenerated charge carriers as studied by photoluminescence studies and to increase in the surface area as studied by Brunauer-Emmett-Teller method. The photocatalytic degradation is studied in detail by varying catalyst loading, dye concentration and the rate constant is determined by first order kinetics. The enhancement in photocatalytic activity of CQDs/rGO catalyst is validated by first principles density functional theory (DFT) calculations which shows the enrichment in density of states thereby decreasing the work function

Encapsulation of cobalt nanoparticles in cross-linked-polymer cages

10.1016/j.jmmm.2009.01.014Journal of Magnetism and Magnetic Materials321142135-2138JMMM

Characteristics of K2Ca2(SO4)3:Eu TLD nanophosphor for its applications in electron and gamma rays dosimetry

Nanorods (~25 nm × 200 nm) of K2Ca2(SO4)3:Eu phosphor (powder) were synthesized by chemical coprecipitation method followed by annealing at 700 °C. Dimensions of nanorods were confirmed by TEM and XRD. The material (pellets) was irradiated by 60Co gamma rays for various doses over the range of 0.1 Gy–100 kGy and also by 6 MeV electrons at different fluences varying from 2.5 × 1011 e/cm2 to 5 × 1013 e/cm2 at room temperature. Thermoluminescence (TL) and photoluminescence (PL) of the gamma and electron irradiated phosphors were also studied. TL glow curve apparently exhibited a peak at around 152 °C with a small hump around 258 °C. The exact number of peaks in a glow curve were determined by thermal cleaning method and glow curves were further deconvoluted by CGCD method to determine trapping parameters. PL emission spectrum consisted of a single emission band at 388 nm (Eu2+ emission) on excitation by 320 nm. The intensity of this peak increased with the electron fluence up to 5 × 1012 e/cm2 and decreases thereafter. The TL response is linear in the dose range from 0.1 Gy to 1 kGy of gamma radiation and electron fluence range from 2.5 × 1011 e/cm2 to 2.5 × 1012 e/cm2. The electronic structures of the pristine and Eu doped K2Ca2(SO4)3 materials were analyzed by means of first-principles density functional theory (DFT) calculations. The dosimetric characteristics suggest that the K2Ca2(SO4)3:Eu nanophosphor can be useful for its applications in radiation dosimetry, especially, for measurement of high-doses of gamma and electrons

Дослідження концентрації газу NO2 на реакцію тонких плівок CdO, отриманих за новим методом зворотного флюсу

У цьому дослідженні, використовуючи простий і недорогий новий метод зворотного холодильника, тонкі плівки оксиду кадмію (CdO) були успішно нанесені на скляну підкладку. Тут для нанесення CdO на скляну підкладку як джерело іонів Cd+ використовувався хлорид кадмію (CdCl2), а як комплексоутворювач – аміак. Структурний аналіз і морфологію поверхні підготовленої тонкої плівки CdO аналізували за допомогою рентгенівської дифракції та скануючої електронної мікроскопії відповідно. Також тест на змочуваність проводили за допомогою гоніометра, який показав гідрофільну природу осадженої тонкої плівки CdO. Оптичні властивості тонкої плівки CdO було завершено за допомогою УФ-видимої спектроскопії, яка виявила, що осаджена тонка плівка CdO має пряму ширину забороненої зони близько 2,01 еВ. Властивості чутливості газу NO2, такі як чутливість, відновлення відгуку та час відгуку підготовленого датчика CdO, було визначено за допомогою датчика газу Keithley. У цій роботі було вивчено вплив концентрації газу NO2 на відгук датчика CdO, і було з’ясовано, що зі збільшенням концентрації газу NO2 (25 ppm – 100 ppm), відгук датчика CdO також збільшується і стає максимальним, тобто (57 %) для 100 ppm NO2 з оптимізованою температурою 200 ˚C. Було вивчено зміну реакції та часу відновлення залежно від концентрації газу NO2 і було зроблено висновок, що зі збільшенням концентрації газу NO2 час відгуку збільшується, а час відновлення зменшується.In present study, using simple and inexpensive novel reflux method, Cadmium Oxide (CdO) thin films were successfully deposited on glass substrate. Here to deposit CdO on glass substrate, Cadmium Chloride (CdCl2) was used as a source of Cd+ ions, while ammonia was taken as complexing agent. Structural analysis and surface morphology of prepared CdO thin film was analyzed by X-ray diffraction and scanning electron microscopy respectively, Also wettability test was done by using goniometer which showed hydrophilic nature of deposited CdO thin film. Optical properties of CdO thin film was completed by using UV-Visible spectroscopy which revealed that deposited CdO thin film has direct band gap about 2.01 eV. NO2 gas sensing properties like sensitivity, response recovery & response time of prepared CdO sensor was determined by using Keithley gas sensing unit. In present work effect of concentration of NO2 gas on response of CdO sensor was studied and it was cleared that as NO2 gas concentration increases (25 ppm – 100 ppm), the response of CdO sensor was also increases & it becomes maximum i.e. (57 %) for 100 ppm of NO2 with optimized temperature of 200˚C. Variation of response and recovery time with NO2 gas concentration was studied and it was concluded that as concentration of NO2 gas increases, response time increases while recovery time decreases