Size and doping effects on the coercive field of ferroelectric nanoparticles

A microscopic model for describing ferroelectric nanoparticles is proposed which allows us to calculate the polarization as a function of an external electric field, the temperature, the defect concentration and the particle size. The interaction of the constituents of the material, arranged in layers, depends on both the coupling strength at the surface and that of defect shells in addition to the bulk values. The analysis is based on an Ising model in a transverse field, modified in such a manner to study the influence of size and doping effects on the hysteresis loop of the nanoparticles. Using a Green function technique in real space we find the coercive field, the remanent polarization and the critical temperature which differ significantly from the bulk behavior. Depending on the varying coupling strength due to the kind of doping ions and the surface configuration, the coercive field and the remanent polarization can either increase or decrease in comparison to the bulk behavior. The theoretical results are compared with a variety of different experimental data.Comment: 16 pages, 7 figure

Synthesis of magnetic fe3o4/znwo4 and fe3o4/znwo4/cevo4 nanoparticles: The photocatalytic effects on organic pollutants upon irradiation with uv-vis light

Magnetic Fe3O4/ZnWO4 and Fe3O4/ZnWO4/CeVO4 nanoparticles with different molar ratios of CeVO4 to other inorganic components were synthesized through co-precipitation with a sonochemical-assisted method. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, vibrating sample magnetometry, and scanning electron microscopy (SEM) methods were used for the physico�chemical characterization of the obtained nanoparticles. As shown in the SEM images, the average sizes of the Fe3O4 /ZnWO4 and Fe3O4 /ZnWO4 /CeVO4 nanoparticles that formed aggregates were approximately 50�70 nm and 80�100 nm, respectively. The photocatalytic performance of these nanoparticles was examined by measuring methylene blue degradation under visible light (assisted by H2O2). The sample with a mass ratio of 1:2:1 (Fe3O4/ZnWO4/CeVO4, S4) exhibited optimal photocatalytic performance, and thus this sample was subsequently used for the photodegradation of different organic pollutants upon irradiation with ultraviolet (UV) and visible light. Approximately 90 and 70 degradation of methyl violet and methylene blue, respectively, was observed after visible light irradiation. Additionally, the mechanism of the photocatalytic reaction was investigated by measuring ·OH release under UV light in a system with terephthalic acid and by measuring the release of·O2 �,·OH, and hole scavengers. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Preparation and characterization of magnetic Fe3O4/CdWO4 and Fe3O4/CdWO4/PrVO4 nanoparticles and investigation of their photocatalytic and anticancer properties on PANC1 cells

Fe3O4/CdWO4 and Fe3O4/CdWO4/PrVO4 magnetic nanoparticles were prepared at different molar ratios of PrVO4 to previous layers (Fe3O4/CdWO4) via the co-precipitation method assisted by a sonochemical procedure, in order to investigate the photocatalytic performance of these systems and their cytotoxicity properties. The physico-chemical properties of these magnetic nanoparticles were determined via several experimental methods: X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transformation infrared spectroscopy and ultraviolet-visible diffuse reflection spectroscopy, using a vibrating sample magnetometer and a scanning electron microscope. The average sizes of these nanoparticles were found to be in the range of 60-100 nm. The photocatalytic efficiency of the prepared nanostructures was measured by methylene blue degradation under visible light (assisted by H2O2). The magnetic nanosystem with a 1:2:1 ratio of three oxide components showed the best performance by the degradation of ca. 70 after 120 min of exposure to visible light irradiation. Afterwards, this sample was used for the photodegradation of methyl orange, methyl violet, fenitrothion, and rhodamine-B pollutants. Finally, the mechanism of the photocatalytic reaction was examined by releasing �OH under UV light in a system including terephthalic acid, as well as O2-, OH, and hole scavengers. Additionally, the cytotoxicity of each synthesized sample was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay against the human cell line PANC1 (cancer), and its IC50 was approximately 125 mg/L. © 2019 by the authors

Synthesis of magnetic fe3o4/znwo4 and fe3o4/znwo4/cevo4 nanoparticles: The photocatalytic effects on organic pollutants upon irradiation with uv-vis light

Magnetic Fe3O4/ZnWO4 and Fe3O4/ZnWO4/CeVO4 nanoparticles with different molar ratios of CeVO4 to other inorganic components were synthesized through co-precipitation with a sonochemical-assisted method. X-ray diffraction, energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, vibrating sample magnetometry, and scanning electron microscopy (SEM) methods were used for the physico�chemical characterization of the obtained nanoparticles. As shown in the SEM images, the average sizes of the Fe3O4 /ZnWO4 and Fe3O4 /ZnWO4 /CeVO4 nanoparticles that formed aggregates were approximately 50�70 nm and 80�100 nm, respectively. The photocatalytic performance of these nanoparticles was examined by measuring methylene blue degradation under visible light (assisted by H2O2). The sample with a mass ratio of 1:2:1 (Fe3O4/ZnWO4/CeVO4, S4) exhibited optimal photocatalytic performance, and thus this sample was subsequently used for the photodegradation of different organic pollutants upon irradiation with ultraviolet (UV) and visible light. Approximately 90 and 70 degradation of methyl violet and methylene blue, respectively, was observed after visible light irradiation. Additionally, the mechanism of the photocatalytic reaction was investigated by measuring ·OH release under UV light in a system with terephthalic acid and by measuring the release of·O2 �,·OH, and hole scavengers. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon

Electrochemical capacitors, also called supercapacitors, store energy in two closely spaced layers with opposing charges, and are used to power hybrid electric vehicles, portable electronic equipment and other devices¹. By offering fast charging and discharging rates, and the ability to sustain millions of ²⁻⁵, electrochemical capacitors bridge the gap between batteries, which offer high energy densities but are slow, and conventional electrolytic capacitors, which are fast but have low energy densities. Here, we demonstrate microsupercapacitors with powers per volume that are comparable to electrolytic capacitors, capacitances that are four orders of magnitude higher, and energies per volume that are an order of magnitude higher. We also measured discharge rates of up to 200 V s⁻¹, which is three orders of magnitude higher than conventional supercapacitors. The microsupercapacitors are produced by the electrophoretic deposition of a several micrometre-thick layer of nanostructured carbon onions⁶‚⁷ with diameters of 6-7 nm. Integration of these nanoparticles in a microdevice with a high surface-to-volume ratio, without the use of organic binders and polymer separators, improves performance because of the ease with which ions can access the active material. Increasing the energy density and discharge rates of supercapacitors will enable them to compete with batteries and conventional electrolytic capacitors in a number of applications

Guía ESC 2015 sobre el tratamiento de la endocarditis infecciosa

[No abstract available

Introducing a novel nanocomposite consisting of nitrogen-doped carbon nano-onions and gold nanoparticles for the electrochemical sensor to measure acetaminophen

In the present study, gold nanoparticles and nitrogen-doped carbon nano-onions (AuNP/NCNO) in a nanocomposite-based sensor were reported for the electrochemical detection of acetaminophen (APAP). The NCNOs from the fullerene family were prepared using a simple and cost-effective method using aminated nanodiamonds (AM-ND) as a substrate. Nitrogen atoms were introduced into CNO cages during the preparation of these nanostructures by annealing AM-NDs under an inert helium atmosphere and reduced pressure. AuNPs were synthesized using a straightforward method. The nanocomposite profoundly enhanced the active surface area of the glassy carbon electrode and amplified the electron transfer rate. Accordingly, electrocatalysis of the APAP was achieved at the modified electrode surface at 0.38 V vs. Ag/AgCl. Under the optimal conditions, the sensor displayed a linear response for APAP detection ranging from 25 nM to 35 mu M with a limit of detection (LOD) of 9 nM. Potentially interfering drugs, such as ascorbic acid and dopamine, with 5-fold higher concentrations did not interfere with APAP detection. The feasibility of the sensor for APAP detection in tablet and serum samples was successfully evaluated. The qualities of this sensor, including its rapid-response, sensitivity and ease of use, maybe beneficial for potential applications in detecting other drugs

Makrostruktura drewna świerka pospolitego (Picea abies [L.] Karst) pochodzącego z powierzchni doswiadczalnej zlokalizowanej na terenie LZD Siemianice

Wood macrostructure of Norway spruce (Picea abies [L.] Karst) coming from an experimental site in the Siemianice Forest Experimental Station. The paper presents results of studies concerning the effect of provenance on the share of latewood in annual rings. Analyses were conducted on seven provenances grown on an experimental site located in the Siemianice Forest Experimental Station. It was established which of the investigated provenances have the greatest share of latewood in annual rings. It was also investigated which of the provenances differ significantly in terms of the analysed trait. Measurements were taken on discs collected from breast height of mean sample trees.Makrostruktura drewna świerka pospolitego (Picea abies [L.] Karst) pochodzącego z powierzchni doświadczalnej zlokalizowanej na terenie LZD Siemianice. Celem pracy bylo zbadanie udziału drewna późnego w przyrostach rocznych wybranych proweniencji świerka pospolitego wyrosłego na powierzchni doświadczalnej znajdującej się na terenie Leśnego Zakładu Doświadczalnego w Siemianicach. Powierzchnia doświadczalna zostala założona w 1975 r. Posadzono na niej najlepsze polskie pochodzenia świerka. W 2012 roku pobrano z wyznaczonych wczesniej drzew modelowych materiał w postaci krążków z wysokości pierśnicy. Szerokość strefy drewna późnego mierzono przy użyciu przyrostomierza Biotronik. Ze względu na unikatowy charakter powierzchni doświadczalnej do analiz przyjęto siedem pochodzeń (Zwierzyniec Białowieski, Międzygórze, Istebna Bukowiec, Orawa, Zwierzyniec Lubelski, Kartuzy i Nowe Ramuki) pobierając po 12 drzew z każdego pochodzenia. Wyniki badań w formie analiz statystycznych wykazaly, ze pochodzenie świerka pospolitego wpływa na udział drewna poznego w przyrostach rocznych. Największym udziałem drewna późnego charakteryzowało się pochodzenie Zwierzyniec, a najmniejszym Międzygórze. Analizy statystyczne wykazały również, że pochodzenie Zwierzyniec Lubelski wykazuje najbardziej istotne zróżnicowanie badanej cechy względem pozostalych proweniencji