Solution Coprecipitation Method Research Articles

Mössbauer and magnetic studies of Fe-doped ZnO nanoparticles prepared by solution co-precipitation method

A series of Zn[Formula: see text]FexO ([Formula: see text], 0.015, 0.045, 0.075) nanoparticles were synthesized using the solution co-precipitation method, and their structural and property characteristics were investigated. X-ray diffraction (XRD) analysis revealed that all Zn[Formula: see text]FexO samples exhibited a hexagonal wurtzite crystal structure with the P63mc space group. The introduction of Fe doping led to a slight lattice distortion in the samples. The morphology of the nanoparticles, including polydispersion and agglomeration, as well as the presence of the second phase ZnFe2O4, was examined by scanning electron microscope (SEM) and transmission electron microscope (TEM). UV–Vis diffuse reflectance spectroscopy demonstrated that the band gap of Zn[Formula: see text]FexO lies between 3.152 and 3.163[Formula: see text]eV. With the increase in Fe ion doping, the band gap shows a slight decreasing trend. Mössbauer spectroscopy revealed that iron ions in the nanoparticles existed in a trivalent state and exhibited two different configurations: One involved iron replacing zinc without creating a vacancy, while the other involved iron substituting zinc with a vacancy. The ferromagnetic nature of the Fe-doped samples can be attributed to the exchange interaction between two Fe[Formula: see text] ions mediated by the F-center mechanism.

Achieving Multicolor Emitting of Antimony-Doped Indium-Based Halide Perovskite via Monovalent Metal Induced Phase Engineering.

Lead-free metal halide perovskites have attracted attention because of their excellent optical properties and nontoxicity. Here, we report the synthesis of Sb3+-doped indium halide perovskite Cs2InCl5·H2O:Sb3+ by an improved solution coprecipitation method. The treatment of the Sb3+-doped indium halide perovskite with selected monovalent cation halides led to Cs2MInCl6 (Ag+, K+, Na+) in different crystal structures or phases. Sb3+ has an isolated ns2 electron, and Sb3+-doped metal halide acts as the luminescence center and exhibits bright broadband emission that originated from self-trapped excitons. Under UV light excitation, these phosphors with different crystal structures emitted multicolored luminescence ranging from blue, green, yellow, and red depending on whether or not or which monovalent metal ion was used. The phosphor samples were used to print high-resolution 2D color barcodes for security and anticounterfeiting applications. The study presented here provides a new approach for the design and synthesis of lead-free metal halide perovskites with different crystal structures and unique optical properties.

Nanoflower-like BiOBr/TiO2 p-n heterojunction composites for enhanced photodegradation of formaldehyde and dyes

A nanoflower-like BiOBr/TiO 2 p-n heterojunction photocatalyst was constructed and the possible photocatalytic mechanism was proposed. The construction of BiOBr/TiO 2 p-n heterojunction can significantly enhance the degradation of methyl orange (MO) and gaseous formaldehyde (HCHO) by photocatalysts. • A efficient nanoflower-like p-n heterojunction photocatalyst BiOBr/TiO 2 was prepared by simple solution coprecipitation. • This catalyst has enhanced photocatalytic degradation of dyes and formaldehyde. • P-n heterojunction effectively separates photogenerated carriers of BiOBr, hindering recombination of electrons and holes. The fabrication of p-n heterojunction is a smart strategy to improve the photocatalytic activity, because p-n junction can effectively promote the separation of photogenerated charges and improve the photocatalytic performance. Herein, a low cost nanoflower-like p-n heterojunction photocatalyst BiOBr/TiO 2 (abbreviated as BT-x) was prepared by simple solution coprecipitation method. Under visible light, BiOBr/TiO 2 p-n heterojunction photocatalyst showed enhanced photocatalytic activity in the degradation of Methyl Orange (MO) and gaseous formaldehyde (HCHO). The degradation rates of MO and HCHO by optimized composite BT-0.6 were 97% and 60% respectively. The p-type BiOBr with narrow band gap can effectively improve the visible light absorption, and its p-n heterojunction with TiO 2 can significantly improve the separation efficiency and transfer rate of photogenerated electron hole pairs. Meanwhile, multi-dimensional nanoflower structure is not only conducive to light reflection and improve light utilization, but also can expose more catalytic active sites. This p-n heterojunction composite material can be used as a new and promising catalyst for environmental applications.

Luminescence Characteristics of LiCaAlF\(_6\):Eu TLD Phosphor

The material LiCaAlF\({}_{6}\):Eu (0.1 mol%) in microcrystalline form was prepared through water solution coprecipitation method followed by melting it at around 900 \({}^\circ\)C in a graphite crucible. The ingot was crushed and sieved through standard sieves to obtain powder approximate in the range 100-125 \(\mu\)m. The material was annealed at around 200-800 \({}^\circ\)C. The material was characterized by XRD. The materials were irradiated to different doses of \(\gamma\)-rays using \({}^{60}\)Co radioactive source and thermoluminescence (TL) glow curves were recorded. The powder material was found to be at least 10 times more sensitive than CaSO\({}_{4}\):Dy commercially available TLD pellets. However, as the dosimetry peak is at around 180 \({}^\circ\)C, there is fading around 20%. Considering these facts, the material could be considered as a highly sensitive and suitable TLD phosphor.

Investigations on the compatibilization between poly(lactic-co-glycolic acid)/poly(trimethylene carbonate) blends and poly(lactide-co-trimethylene carbonate)

In this study, the effect of different contents of poly(lactide-co-trimethylene carbonate) (PLT) as a compatibilizer on the blends of PLGA and PTMC has been investigated. The PLGA/PTMC/PLT ternary composites were prepared by using the solution co-precipitation method. The PLT component played a very important role in determining internal structure, and thermal, mechanical, and hydrophilic properties of whole composites. Our results showed that the PLT addition made the glass transition temperature of PLGA and PTMC close to that of each other and improved their compatibility. When the amount of PLT addition was 3 wt%, the two-phase interface of the composite fracture surface almost disappeared, which further demonstrated that PLT could improve the interfacial compatibility of PLGA and PTMC. The tensile strength and tensile modulus and the elongation of the PLGA/PTMC/PLT composites were 54.01 ± 2.1 MPa, 1.11 ± 0.05 GPa, 49.29 ± 3.6% respectively after the 3 wt% random copolymers was added. The results of XRD and POM showed that the crystalline morphology of the composites was spherocrystal, where the second crystalline phase was not found. Interestingly, PLT reduced the hydrophilicity of PLGA/PTMC/PLT composites. In conclusion, PLGA/PTMC/PLT composites are expected to have a fascinating role in the field of bone defect repair.

Particle size effects on the dosimetry characteristics of K3Na(SO4)2:Eu TLD micro- and nanophosphors

K3Na(SO4)2:Eu is a highly sensitive TLD material in its microcrystalline form. It has been found that the material in its nanocrystalline form could also be used for very high dose measurements (of the order of 100 kGy) of high-energy radiations, like γ rays. However, it is not known whether the nanoparticle prepared by different methods of preparation, i.e., prepared using chemical coprecipitation method (by bottom up approach) and by ball milling (top down approach) behave in a similar manner. In the present paper, the TLD material was prepared by the standard solid state diffusion method, crushed and sieved/ball milled for different time periods to get particles of different sizes ranging from micro- to nanosize ranges. TL dosimetry characteristics of the material were studied and compared with our earlier results on the nanoparticles prepared by chemical coprecipitation method. It has been found that the K3Na(SO4)2:Eu powder sample in the particle size range 75–106 µm show the highest sensitivity and could be used up to 10 kGy dose of γ radiation. It has also been found that the nanoparticles prepared by two different approaches behave differently, i.e., the nanoparticles prepared by chemical coprecipitation method though are less sensitive than the microcrystalline but they do not saturate even up to very high doses (∼100 kGy, whereas the nanoparticles prepared by ball milling are equally sensitive to that of prepared by solution coprecipitation method but saturate early (at lower doses). It has been concluded that the surface defects might be playing an important role. The effect of high energy γ radiation on its repeated use as TLD phosphor for high doses (radiation hardening) was also studied and found that another TL peak at high temperature appears and its intensity varies on repeated use but the dosimetry peak remains invariant making the phosphor reusable for several times.

Controlled synthesis various shapes Fe3O4 decorated reduced graphene oxide applied in the electrochemical detection

The various shapes Fe3O4 decorated reduced graphene oxide (Fe3O4/rGO) were prepared by one-step solution co-precipitation method, in which the shapes (sphere, rod and band) of Fe3O4 in the nanocomposites could be carefully controlled by adjusting the mole ratio of Fe2+/Fe3+ in the presence of rGO modified PVP. The structure of Fe3O4/rGO was characterized by SEM, EDS, TEM and Raman. Furthermore, the band Fe3O4/rGO modified glassy carbon electrode (GCE) was characterized by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). And the effect of shapes of Fe3O4 decorated reduced graphene oxide on the electrochemical detection of Pb(II) was investigated in detail. It was found that the shape of Fe3O4 had great effects on sensitivity. The band Fe3O4/rGO modified electrode toward Pb(II) showed high sensitivity (13.6μA/μM), which was higher than that of spherical and rod Fe3O4/rGO modified electrode, respectively. The band Fe3O4/rGO was further demonstrated to be useful for the individual electrochemical detection of Cd(II) and Cu(II) in water for the first time. This report provides an opportunity to study relationship between the shapes and properties of Fe3O4 decorated reduced graphene oxide with high performance.

Preparation of Mg<sub>2</sub>Al Layered Double Hydroxide Nanosheets from Triton X-100 Hexagonal Lyotropic Liquid Crystal and Their Application as Drug Carriers

A hexagonal lyotropic liquid crystal (LLC) was constructed with nonionic surfactant Triton X-100 and mixed magnesium chloride/aluminum chloride aqueous solutions. Layered double hydroxide (LDH) nanosheets (L-LDHs) were prepared using the LLC as a microreactor. A nanohybrid material of L-LDHs intercalated with a model anionic drug, diclofenac sodium (DS; DS/L-LDHs) was synthesized using an ion- exchange method. The drug-release profile of DS/L-LDH was investigated under moderate conditions, i.e., 37.0 °C and pH 7.2. The results were compared with those for common LDH flaky particles (S-LDHs) synthesized using a traditional solution coprecipitation method. The crystalline structures, specific surface areas, and morphologies of these LDHs and DS/LDHs nanohybrids were characterized using powder X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and N2 adsorption-desorption. The results show that the L-LDH

Size-regulated group separation of CoFe2O4 nanoparticles using centrifuge and their magnetic resonance contrast properties

Magnetic nanoparticle (MNP)-based magnetic resonance imaging (MRI) contrast agents (CAs) have been the subject of extensive research over recent decades. The particle size of MNPs varies widely and is known to influence their physicochemical and pharmacokinetic properties. There are two commonly used methods for synthesizing MNPs, organometallic and aqueous solution coprecipitation. The former has the advantage of being able to control the particle size more effectively; however, the resulting particles require a hydrophilic coating in order to be rendered water soluble. The MNPs produced using the latter method are intrinsically water soluble, but they have a relatively wide particle size distribution. Size-controlled water-soluble MNPs have great potential as MRI CAs and in cell sorting and labeling applications. In the present study, we synthesized CoFe2O4 MNPs using an aqueous solution coprecipitation method. The MNPs were subsequently separated into four groups depending on size, by the use of centrifugation at different speeds. The crystal shapes and size distributions of the particles in the four groups were measured and confirmed by transmission electron microscopy and dynamic light scattering. Using X-ray diffraction analysis, the MNPs were found to have an inverse spinel structure. Four MNP groups with well-selected semi-Gaussian-like diameter distributions were obtained, with measured T2 relaxivities (r2) at 4.7 T and room temperature in the range of 60 to 300 mM−1s−1, depending on the particle size. This size regulation method has great promise for applications that require homogeneous-sized MNPs made by an aqueous solution coprecipitation method. Any group of the CoFe2O4 MNPs could be used as initial base cores of MRI T2 CAs, with almost unique T2 relaxivity owing to size regulation. The methodology reported here opens up many possibilities for biosensing applications and disease diagnosis.PACS75.75.Fk, 78.67.Bf, 61.46.Df

Gas sensing properties of Nd2O3 nanostructured microspheres

Nd2O3 microspheres were prepared by a solution-coprecipitation method. The dissolution of neodymium nitrate in formic acid produced, at room temperature, semispherical particles of neodymium formate (Nd(HCOO)3). The size of these particles was in the range 0.5 to 1.4μm. The thermal decomposition at 600°C transformed Nd(HCOO)3 to single-phase Nd2O3, with cubic crystal structure. A decrease of size of ~15% also took place. A detailed inspection of their surface revealed the formation of a sponge-like solid, possessing extensive nanoporosity. The gas sensing characterization was performed on thick films made with the as-prepared Nd2O3 microspheres. Based in the response to the test gases an n-type semiconductor behavior was observed. A reliable detection of CO was observed from 300°C, using an applied frequency of 100kHz; however, better results were obtained at 400°C. For CO2, the best results were registered at 400°C and 100kHz; whereas in ethanol vapor these were obtained at lower temperature and frequency (300°C and 100Hz). Quantitative detection of CO and ethanol vapor was achieved; however, the results were not satisfactory for CO2.

Gas sensing properties of Gd2O3 microspheres prepared in aqueous media containing pectin

Single phase Gd 2 O 3 hollow microspheres were prepared by a direct aqueous solution–coprecipitation method. The synthesis was performed in presence of formic acid and pectin. The precursor dried at 170 °C was identified as gadolinium formate. The calcination at 500 °C produced single-phase Gd 2 O 3 . Hollow microspheres, with diameter between 0.7 μm and 2.5 μm were observed by SEM. Their inspection by TEM revealed that the shells of the microspheres were formed by a network of interconnected nanoparticles. Nanoporosity was also observed in these shells. The use of formic acid played a key role in the formation of Gd 2 O 3 microspheres. The synthesis using acetic acid and pectin produced a material with an irregular shape. The CO 2 and CO gas sensing characterization was performed on thick films using AC (impedance). The films were prepared by a simple deposition method, using the as-prepared microspheres. The n-type semiconductor behavior of Gd 2 O 3 was confirmed by its response to the test gases. Repeatability and reproducibility in the detection of the gases was observed at 470 °C. A significant better performance was observed in CO 2 . Polarization curves qualitatively agreed with the impedance measurements.

Influence of urea on microstructure and optical properties of YPO4:Eu3+ phosphors

YPO4:Eu3+ phosphors were synthesized by solution coprecipitation method assisted by urea in the precursor reaction solution. X-ray diffraction spectral analysis showed that the samples synthesized with urea had smaller particle size and lower crystallinity than those samples synthesized without urea. Moreover, the calculated strain result indicated that the Eu3+ site in the former exhibited a lower crystal field symmetry than that in the latter. Hence, the influence of crystal field symmetry dominated luminescence efficiency rather than crystallinity because the luminescence intensity observed in Eu0.05Y0.95PO4 synthesized with 1.0 g urea was six-fold higher than that of the as-synthesized sample. With increased concentration of Eu3+ ion, the luminescence intensity initially increased, and then subsequently decreased as the concentration of Eu3+ ion exceeded 12 mol.% due to concentration quenching. The optimal condition for YPO4:Eu3+ phosphor was Eu0.12Y0.88PO4 with 1.0 g urea added in the precursor. The luminescence intensity of the optimal condition was again enhanced 1.6-fold relative to that of Eu0.05Y0.95PO4 synthesized with 1.0 g urea.

CO2 sorption and diffusion in polymethyl methacrylate-clay nanocomposites

This study reports the glass transition temperature (Tg), and sorption and diffusion of subcritical CO2 gas in polymethyl methacrylate (PMMA) nanocomposites containing organically modified smectite clay, Cloisite 20A (C20A). A range of methods for preparing the PMMA-clay nanocomposites was investigated and a solution coprecipitation method was selected as the most appropriate. Using this method, PMMA nanocomposite containing 2, 4, 6, and 10 wt% nanoclay loadings were prepared. Wide-angle X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) indicated that the 2 wt% nanocomposite materials had a well-dispersed intercalated clay structure. The Tg for PMMA-C20A nanocomposites, as measured by differential scanning calorimetry (DSC), was found to be independent of the clay loading. CO2 solubility studies from 0 to 65°C and pressures up to 5.5 MPa using an in situ gravimetric technique were performed on compression-molded films. The organoclay was found to have no effect on the solubility of CO2 in PMMA, and therefore the solubility of CO2 in the nanocomposite can be determined from the solubility of CO2 in the matrix polymer alone. Diffusion coefficients were determined using the appropriate transport models for these test conditions and the diffusion coefficients for CO2 in PMMA-C20A composites were found to increase with organoclay loading. It is believed that the processing path taken to prepare the nanocomposites may have resulted in the agglomeration of the C20A organoclay, thereby preventing the polymer chains from fully wetting and intercalating a large number of clay particles. These agglomerations are responsible for the formation of large-scale holes within the glassy nanocomposite, which behave as low resistance pathways for gas transport within the PMMA matrix. POLYM. ENG. SCI., 45:904–914, 2005. © 2005 Society of Plastics Engineers

Ultrafine microsphere particles of zirconium titanate produced by homogeneous dielectric-tuning coprecipitation

Zirconium titanates are widely used in electrical (common microwave dielectrics) and optical devices as well as in bifunctional catalysis and structural ceramics. In this paper, ultrafine amorphous solid microsphere precursor particles of zirconium titanate (Zr x Ti1 − x O2) with possibly tailored intraparticle nanostructure (i.e., nanosized pores) were synthesized by a “dielectric-tuning” solution coprecipitation method, in which inorganic salts were dissolved in a simple water-alcohol mixture and homogeneous nucleation and growth of particles were then induced by heating at temperatures below 100°C. Near-monodispersed particles were obtained. Particle sizes (nanometers to a few micrometers in diameter) were controlled by adjusting the process parameters such as salt concentration, alcohol-to-water volume ratio, temperature, and heating time. Nanosphere particles were produced with a rapid microwave heating nucleation-control scheme. Transmission electron microscopic analysis of each individual microsphere indicates that uniform nanostructures (a few nanometers in pore size) as well as compositional homogeneity (in terms of the Zr/Ti ratio) have been obtained inside each amorphous microsphere. In situhigh-temperature X-ray diffraction data show that no phase segregation was observed in as-preprared microspheres and the transition from amorphous to the single-crystalline ZrTiO4phase occurred around 650°C for a composition of Zr/Ti = 1. Interestingly, thermal analysis (DTA/TGA) data indicate that the solution synthesis condition seems to affect the crystallization activation energy and onset temperature, which varies from 530 to 680°C.

Solid-state 7Li NMR studies of inverse spinel LiNi xCo 1− xVO 4 cathode materials

Solid-state 7Li NMR spectroscopy revealed different Ni/Co distributions in an inverse spinel structure of LiNi x Co 1− x VO 4 cathode materials prepared by either a high-temperature solid-state reaction method (abbreviated as the HT method) or a low-temperature solution co-precipitation method (abbreviated as the LT method). Solid-state 7Li NMR measurements confirmed that the lithium nuclear spin was dominated by a chemical shift anisotropy (CSA) interaction compounded with a small second-order quadrupolar interaction. Ni/Co distribution and inhomogeneity of chemical shift tensors ( δ CSA and η CSA constants) associated with crystalline defects are accountable for the variation in spread of the MAS spinning side-band manifolds between nickel uptake and preparation methods. The NMR study also revealed that the HT method yielded broader Ni/Co distributions with greater lithium defects, while the LT method gave much more homogeneous Ni/Co distributions with smaller defects. The NMR results were consistent with XRD data that showed a gradual expansion in the unit-cell lattice with increasing Co content. All cells suffered a large irreversible loss in overall capacity in the first cycle and became stable in terms of cycle efficiency during later cycling. We have found that LiNi x Co 1− x VO 4 cathode materials prepared by the LT method with more homogeneous Ni/Co distribution and smaller crystalline defects offer a small advantage in capacity over the HT method.