Polymer-assisted Sol Gel Method Research Articles

Optimization of the Synthesis of Copper Ferrite Nanoparticles by a Polymer-Assisted Sol-Gel Method.

Magnetic ferrites are used in a wide range of technological applications, such as biomedicine, electronics, or energy. They also present interesting magnetic properties, especially for high-frequency applications. These materials have been prepared by a large variety of methods, from basic solid-state reaction to advanced wet chemical methods. However, most of these approaches are complex and have low production rates. In this work, a deep analysis of an easy polymer-assisted sol–gel synthesis of copper ferrite (CuFe2O4) nanoparticles is done. A multivariate analysis, by means of the design of experiments approach, is carried out to account for two variables at a time. Moreover, a wide experimental domain is explored, and the impact of each variable on the chemical composition and magnetic properties is determined. This work results in an optimization of the synthesis method to obtain high-purity nanoparticles (∼96%).

Surface modification of oxygen-deficient ZnO nanotubes by interstitially incorporated carbon: a superior photocatalytic platform for sustainable water and surface treatments

An interesting architecture of robust, highly reproducible, template-free synthesis of phase pure carbon-incorporated short ZnO nanotubes through polymer assisted sol–gel method is presented here. These nanotubes exhibit enormous surface oxygen vacancies and mid bandgap levels confirmed by X-ray photoelectron spectroscopy. These carbon-modified nanotubes exhibit encouraging results in photocatalytic studies, as there is a 16% greater degradation of contaminant dye than in the pristine ZnO nanotube. The reactive oxygen species generated from the photocatalysts were experimentally confirmed and quantified. Super hydrophilic nature renders these nanotubes suitable for antifogging application as observed from contact angle measurements. Characterisation and mechanism of a competent material with improved photoresponse, promising greater energy efficiency and anti-fog have been described in this investigation.

The broad emission at 785 nm in YAG:Ce3 +,Cr3 + phosphor

Luminescence of defects and/or impurities is important for phosphors. One broad emission band centered at 785nm was observed in (Y0.97Ce0.03)3(Al1–xCrx)5O12 (x=0.005, 0.01, 0.03, 0.06, 0.09), (YAG:Ce,Cr) nano-particles synthesized by polymer-assisted sol-gel method in this work. In order to study the source of this wide emission band, the crystalline phase structure of the phosphors was examined by X-ray diffraction (XRD). No obvious diffraction peaks due to impurity phase were observed even though the calcining temperature of the samples arrived at 1400°C. The anti-site defects were excluded. No detectable signals of impurities were obtained by X-ray Photoelectron Spectroscopy (XPS) or inductively coupled plasma mass spectrometry (ICP-MS). Based on the photo-luminescence results of YAG:Ce,Cr, YAG:Ce and YAG:Fe phosphors, the wide emission band is attributed to the 4T1(4G)→6A1(6S) transition from the trace impurity of Fe3+. The excitation band at 280nm is assigned to Fe3+-O2– charge transfer band.

Luminescent spectroscopy and structural properties of Ce3+-doped low-temperature X1–Y2SiO5 material prepared by polymer-assisted sol–gel method

Cerium (Ce3+)-doped monoclinic X1–Y2SiO5 (YSO)-type oxyorthosilicates powders were prepared by monomer and polymer-assisted sol–gel method. The present work aims to study the influence of ethylene glycol (EG) monomer, polyethylene glycol (PEG) polymer and polyvinyl alcohol (PVA) polymer, as fuels and nucleating agents for the crystallization, on structural and luminescence properties of the Ce3+ (xCe = 0.01)-doped Y2SiO5. The X-ray diffraction technique, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and steady photoluminescence have been used to characterize the samples. It is found that the types of fuels affect the phase purity and luminescent characteristics of phosphors. All samples exhibit intense violet-blue asymmetric emission band in the range of 370–540 nm with a maximum intensity centered at around 420 nm assigned to the 5d → 4f (2F5/2, 2F7/2) interconfigurational transitions of Ce3+ ion in YSO nanomaterial. Finally, the vibronic coupling parameters are estimated and discussed.

Separation of Selenite from Inorganic Selenium Ions using TiO2Magnetic Nanoparticles

A simple and quick separation technique for selenite in natural water was developed using @ nanoparticles. For the synthesis of nanoparticles, a polymer-assisted sol-gel method using hydroxypropyl cellulose (HPC) was developed to control particle dispersion in the synthetic procedure. In addition, titanium butoxide (TBT) precursor, instead of the typical titanium tetra isopropoxide, was used for the formation of the shell. The synthesized nanoparticles were used to separate selenite () in the presence of or selenium anions for the photocatalytic reduction to atom on the shell, followed by magnetic separation using nanoparticles. The reduction efficiency of the photocatalytic reaction was 81.4% at a UV power of 6W for 3 h with a dark adsorption of 17.5% to the nanoparticles, as determined by inductively coupled plasma-mass spectrometry (ICP-MS). The developed separation method can be used for the speciation and preconcentration of selenium cations in environmental and biological analysis.

High-performance porous nanoscaled LiMn2O4 prepared by polymer-assisted sol–gel method

Porous nanoscaled LiMn2O4 sample has been successfully prepared by a polymer-assisted sol–gel method. The porous structure is composed of nanoparticles ranging from 50 to 100nm. The as-obtained LiMn2O4 exhibits specific capacity of 131mAhg−1 at 0.5C and 105mAhg−1 even at 20C. At 2C, the capacity retention reaches 73.3% after 1000 cycles at room temperature and 77.3% after 100 cycles at 60°C. Such outstanding rate capability and cyclic performance can be ascribed to the unique porous nanoscaled structure. Short Li-ion diffusion path and high diffusion coefficient lead to the superior rate capability. The improved cyclic performance originates from low Mn dissolution and accommodation to the structural distortion provided by the porous structure during cycling.

Energy transfer and enhanced 1532 nm emission in Er3+ and Ce3+ co-doped Y3Al5O12 nano-particles

A series of Y3Al5O12:Ce3+, Er3+ (YAG:Ce, Er) nano-particles were synthesized by polymer-assisted sol–gel method. X-ray diffraction measurements reveal that a pure crystalline phase of YAG is achieved at temperature as low as 800 °C. The energy transfer from Ce3+ to Er3+ is studied based on photoluminescence spectroscopy and fluorescence decay patterns. It results that the emission intensity of Er3+ at near infrared (NIR) 1532 nm under indirect excitation of Ce3+ (460 nm) is 10 times stronger than that of direct excitation of Er3+ (275 or 380 nm). The energy transfer efficiency is estimated as 95.5% for YAG:Ce0.03Er0.09 sample. The very efficient energy transfer path and mechanism are also discussed.

Luminescent properties and energy transfer of Y3Al5O12:Ce3+, Ln3+ (Ln=Tb, Pr) prepared by polymer-assisted sol–gel method

Y3Al5O12:Ce3+, Pr3+ and Y3Al5O12:Ce3+, Tb3+ nano-particles have been synthesized by polymer-assisted sol–gel method. Crystal structure, luminescent properties and energy transfer of the phosphors are analyzed. XRD study of polycrystalline powders shows that all the samples are of YAG phase without impurity. Photoluminescence (PL) emission and excitation spectra illustrate that in YAG:Ce, Pr phosphors, energy transfer occurs mutually between Ce3+ and Pr3+, while in YAG:Ce, Tb systems, only one-way path energy transfer of Tb3+→Ce3+ is observed.

Structural, thermal, dielectric and magnetic properties of NiFe2O4 nanoleaf

The leaf-like NiFe2O4 nanostructure formed from nanoparticles has been successfully prepared on polymer assisted sol–gel method. Here ethylene glycol (EG) is used as a gelling agent as well as solvent and PVA as a capping agent. A sequence of control experiments confirms that the polymer concentration with NiFe2O4 has direct influence on the morphology of the products. Characterization of the synthesized nanoparticles and nanoleaf are carried out using powder XRD, FT-IR, TGA, HR-SEM, TEM, HR-TEM, dielectric measurements tangent, microRaman and VSM. On the basis of these experimental results, potential influence mechanisms in the growth processes are proposed.

Judd–Ofelt analysis of luminescence emission from Zn 2SiO 4:Eu 3+ nanoparticles obtained by a polymer-assisted sol–gel method

In this research we prepared Zn 2SiO 4:Eu 3+ phosphor nanopowders using a combination of sol–gel and combustion synthesis with the aim to examine the influence of synthesis conditions on the optical properties of the phosphor. As combustion fuels we used polyethylene glycol (PEG) with different average molecular weights, and the combustion was performed in two ways—in a microwave oven and a conventional furnace. Optical properties were examined by photoluminescence spectroscopy and spectra of all samples showed intense red emission, typical for f–f electronic transitions of the Eu 3+ ions. Emission decays exhibited classical one exponential behavior at longer times and nonlinear nature at short times, with average lifetimes varied from 0.49 to 0.71 ms between samples. Judd–Ofelt theory was applied to experimental data for the quantitative determination of optical parameters such as Ω 2,4 Judd–Ofelt parameters, radiative and nonradiative transition rates and emission quantum efficiency. Calculated parameters vary moderately between samples prepared with different PEGs and combusted in different manner.

Rare-earth doped (Lu0.85Y0.15)2SiO5 nanocrystalline powders obtained by polymer assisted sol–gel synthesis

Abstract In the present work we explored the possibility of obtaining nanocrystalline (Lu 0.85 Y 0.15 ) 2 SiO 5 (LYSO) powders using polymer assisted sol–gel method. The synthesis started from TEOS as alkoxide precursor while polyethylene glycol with average molecular weight of 4000 was used as fuel. The resulting powders were obtained by firing gels in two ways: in conventional furnace and in microwave oven, with further annealing. This modified sol–gel synthetic route enabled production of pure phase LYSO powders at much lower temperatures (1050 °C) compared to classical, -solid-state methods (1400 °C). Crystallization kinetics are examined using differential thermal analysis, and rather low values of crystallization activation energies (around 12 kJ/mol) were found, revealing good potential of this method for low-temperature production of LYSO powder.

Optical and structural properties of Zn 2SiO 4:Mn 2+ green phosphor nanoparticles obtained by a polymer-assisted sol–gel method

A novel procedure for Zn 2 SiO 4 :Mn 2+ phosphor powder synthesis based on a combination of sol–gel and combustion methods is presented. The procedure utilizes Zn-nitrate, Mn-nitrate, tetraethylorthosilicate and polyethylene glycol to produce gel, which is then combusted in a microwave oven to form Zn 2 SiO 4 :Mn 2+ powder and further annealed to crystallize in desired structure. The material has been investigated by X-ray diffraction, scanning electron microscopy, infrared and photoluminescence spectroscopy. These investigations showed well-crystallized powder particles exhibiting intense green light emission.

Effect of poly(vinyl acetate) on structure and property of bismuth-doped strontium titanate thin films derived by sol–gel method

Bismuth-doped strontium titanate thin films with pure perovskite phase have been successfully deposited on Pt (1 1 1)/Ti/SiO 2/Si substrate by polymer-assisted sol–gel method. Poly(vinyl acetate) (PVAc) in precursor solution promoted the formation of perovskite phase during the heat treatment. SEM results revealed an increasing thickness from 40 to 80 nm every single layer and a porous structure with the addition of PVAc. The addition of polymer made the dielectric constant decrease from 140 to 40 and the tunability slightly increase compared with films without polymer in precursor.