Papers by Keyword: Polyol Method

Abstract: Green light-emitting YPO₄:Tb³⁺ and YPO₄:Tb³⁺: Ce³⁺ nanoparticles were synthesised at low temperatures using the polyol method. The phase purity, micromorphology and luminescence characteristics were studied using Transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier Transfer Infrared absorption spectroscopy (FT-IR) and Photoluminescence spectroscopy (PL). Combined XRD and TEM analysis showed that the YPO₄ nanoparticles crystallised into a single phase of tetragonal (I41/amd) structure. For all samples, the emission intensity at λ_em=543 nm assigned to ⁵D₄→⁷F₅ is more prominent than ⁵D₄→⁷F₆ with a maximum at λ_em=488 nm, and the asymmetric ratio was calculated and analysed. The asymmetric ratio is strongly correlated with the symmetry around the local environment of Tb³⁺ ions. A significant increase in the asymmetric ratio is observed with an increase in annealing temperature. The energy transfer from Ce³⁺ ions to Tb³⁺ ions was tested by studying the photoluminescence properties of YPO₄:Tb³⁺ and YPO₄:Tb³⁺: Ce³⁺ nanoparticles and how it results in the improvement of the luminescence intensity. The Ce³⁺ 5d−4f and Tb^{3+ 5}D₄→⁷F_J (J = 6 − 3) transitions were observed.

Abstract: In this study, silver nano/micro structures were successfully synthesized from silver nitrate via a polyol method at 160 °C. In our synthesis route, ethylene glycol (EG) was used as both as solvent and reducing agent, and polyvinylpyrrolidone (PVP) with different molecular weight was employed as capping agent. When reduced the PVP’s molecular weight from 58000 to 8000, the spherical morphology of silver particles changed to rod shape. Moreover, by changing the injection method of PVP and controlling the reaction time, silver nanoparticles with uniform spherical morphology and size was prepared. The obtained silver nanoparticles were characterized by X-ray diffraction (XRD) and ultraviolet-visible spectrophotometry (UV-vis) which indicated the formation of nanoparticles. Scanning electron microscopy (SEM) contributed to the particle morphology and size analysis. The morphology and particle size of the resulting silver nanoparticles were depended on the PVP’s molecular weight and the injection method.

Abstract: Silver ions have superior bactericidal properties, and their bactericidal activity ranks second among all metals (mercury ranks first, toxic, not used now). Due to its unique physical and chemical properties, nano-silver has also received increasing attention from researchers, and its antibacterial properties are far superior to traditional silver ion bactericides, such as silver nitrate and silver sulfadiazine. But the properties and performance of nanosilver materials depend on their size and morphology.In this paper, the nano-silver line was prepared by the polyol method. By controlling the ratio of AgNO₃ and PVP, the concentration of NaCl and the acidity and alkalinity of the reaction solution, the effects of reaction time and reaction temperature on the morphology and diameter of the silver wire were investigated. The antibacterial properties of nanosilver were determined by the perforation inhibition method. The experimental results showed that as the reaction temperature increased, the silver particles in the product decreased significantly, the diameter of the silver wire tended to be uniform, but the diameter increased. Finally, the optimal reaction temperature for preparing the silver oxide wire by the polyol method was 150 °C, the reaction time was 10 hours, and the diameter of the silver wire was 100 nm to 200 nm. Based on the measurement of the antibacterial diameter of nano-silver with different morphologies on Escherichia coli and Staphylococcus aureus, it can be found that nano-silver with different morphologies has excellent antibacterial effect, and silver cube is superior to silver particles and nano-silver lines.

Abstract: Effect of temperature on the formation of silver nanorods (AgNRs) synthesized using polyol method has been investigated. In this experiment, materials were used silver nitrate (AgNO₃) as main raw material, ethylene glycol (EG) as a solvent, small amount of sodium chloride (NaCl) as a mediated agent, while polyvinyl alcohol (PVA) as a capping agent to assist the growth of AgNRs. To apply a constant temperature at each synthesis process, an Erlenmeyer flask containing the sample was immersed in a controllable magnetic stirrer oil bath. It is found that the presence of heat as represented by the temperature of oil bath has been shown to have a strong impact on the AgNRs formation. The scanning electron microscope (SEM) confirmed uniform and high density of AgNRs when the oil bath temperature during polyol process was 140 °C. In the same condition, the UV-vis spectra also confirmed formation process of AgNRs with appearance of the transverse plasmon peak about 350 nm. Finally, the X-ray diffraction (XRD) pattern represented that the final product of AgNRs was highly crystallized.

Abstract: Silver (Ag) nanostructures, such as nanoparticles and nanowires, were formed by electroless deposition in ethylene glycol at 160 °C for 1h. Polyvinyl pyrrolidone (PVP) were used both as a capping agent and structure-directing agent to prevent agglomeration and promote the growth of Ag nanowires. The effect of its molecular weight and concentration on the morphology of Ag was examined by X-Ray Diffraction (XRD) and scanning electron microscopy (SEM). XRD analysis showed peaks corresponding to the face-centered cubic (FCC) structure of metallic silver. At low PVP molecular weight of 10,000, spherical Ag nanoparticles with a mean diameter of about 170 nm were formed. A mixture of Ag nanoparticles and nanowires were produced when the molecular weight was increased to 55,000 and 360,000.

Abstract: Metal oxide nanocomposites were prepared by two different routes: polyol and sol-gel. Characterization by X ray diffraction showed that the first process produces directly a two-phase material, while the sol-gel powder never showed second phase below 600°C. Light spectroscopy of the treated powders indicated similarities for the processed materials. Although the overall material compositions are about the same, different structural characteristics are found for each processing. With the exception of Ti-Zn materials, all the double metal oxide powders showed higher absorbance than either TiO₂ powder_.

Abstract: Nanostructured composites based on titanium dioxide have been studied in order to improve optical and photo-catalytic properties, as well as their performance in gas sensors. In this work, titanium and tin dioxides were simultaneously synthesized by the polyol method resulting in TiO₂ platelet coated with SnO₂ nanoparticles as was observed by scanning electron microscopy. The thermal analysis showed that the combined synthesis promotes more easily the crystallization of the TiO₂ rutile phase. The composite obtained after heat treatment at 500 °C showed to be formed of almost only rutile phases of both oxides. The optical properties analyzed by UV-Vis spectroscopy showed that the combined oxides have higher absorbance, which reinforces a model found in the literature based on the flow of photo-generated electrons to the conduction band of SnO₂ delaying the recombination of charges.

Abstract: This paper elaborates Ni_0.8-Cu_0.2-coated YSZ material prepared with the hard template method and the polyol method, with the composition and microstructure being analyzed with X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). With YSZ as electrolyte material, LSM as cathode material and Ni_0.8Cu_0.2O_x prepared with sol-gel method and partially-tubular YSZ material coated with Ni_0.8-Cu_0.2 as anode material, electrolyte-supported cells were prepared, and with methane as fuel gas, the electrical properties of cells were determined. It was indicated that Ni and Cu prepared with traditional sol-gel method and YSZ were granular structure, and the contact area was small relatively. The new material prepared was a mixture of Ni, Cu and YSZ, where the YSZ was of partial fiber-tubular structure and the Ni and Cu granules were applied to the interior and exterior surfaces of the structure. It was able to effectively increase the contact surface of catalytic metal and electrolyte, which added to the three phase boundary of the SOFC anode and lead to power performance 80% higher than the former.

Abstract: Plate-like LiMnPO₄ particles were prepared by polyol method. The chemical and physical properties of plate-like LiMnPO₄ particles were characterized by XRD and SEM. The thickness of plate-like LiMnPO₄ particles was approximately 35 nm. XRD pattern of plate-like LiMnPO₄ was good agreement with orthorhombic olivine structure. The first discharge capacity of C/LiMnPO₄ cathode was approximately 95 mAh/g. 99.9 % of initial discharge capacity was maintained after 100 cycles.

Abstract: Nanoparticles based on tin compounds and alloys have been prepared by using the polyol and/or sonochemical methods. Thus, nanoparticulated Fe1-xCoxSn2 solid solutions were prepared by using the polyol method or, alternatively, a combination of the polyol and the sonochemical methods, and the Rietveld refinements of the XRD patterns confirm the formation of the solid solutions solutions. Pure or pyrolyzed polyacrylonitrile (PAN) can be used to create a matrix that encapsulate the metallic particles and improve the electrochemical cycling behavior. Thus, MSn2@PAN (where M=Fe or Co) have been prepared by using dimethylformamide like solvent of PAN and applying high-intensity ultrasonication to achieve small particle size, poor crystallinity and high dispersion. The very small particles of MSn2 exhibit higher tendency to be oxidized in air atmosphere than the larger particles. The very small particle size of the alloy and the organic phase (PAN) contribute to stabilize the interfaces and the contacts in the electrode, as is evidenced by the electrochemical cycling and the impedance spectra. A model is proposed for the electrochemical behavior of the MSn2@PAN electrode materials. MSn2@C materials can be prepared throughout the pyrolysis of the PAN molecules matrix.