Hydrothermal synthesis and photoluminescence properties of SrCO3

Well-crystallized strontium carbonate (SrCO₃) nanoparticles were successfully synthesized by a simple hydrothermal method. The products were characterized by X-ray diffraction (XRD), which is in good agreement with orthorhombic SrCO₃. Raman spectrum is in accordance with its crystal structure. Field emission scanning electron microscopy (FE-SEM) characterization indicates that the as-synthesized SrCO₃ nanoparticles are of mean size about 80 nm. The band gap of SrCO₃ was estimated by Wood and Tauc method through UV-visible reflection spectrum, showing a band gap value of 3.17 eV (391 nm). The photoluminescence properties of the as-synthesized SrCO₃ were measured at room temperature, which shows excellent emissions with two emission centers ranging from ultraviolet to red. The ultraviolet emission center locates at 390 nm, and the green emission center locates at 523 nm, respectively.     

Low temperature synthesis and optical properties of CaTiO3 nanoparticles from Ca(NO3)2·4H2O and TiO2 nanocrystals

Choosing low-melting-point Ca(NO₃)₂·4H₂O and high-reactive-activity TiO₂ nanocrystals as the raw materials, a simple and cost-effective route was developed for the synthesis of CaTiO₃ nanoparticles at 600 °C, which is much lower than that (about 1350 °C) used in the conventional solid state reaction methods. X-ray diffraction, energy dispersive X-ray spectroscopy and field emission scanning electron microscopy revealed the formation of orthorhombic phase CaTiO₃ nanoparticles with oxygen-deficiency at the surface. UV-vis absorption spectrum of the as-obtained CaTiO₃ nanoparticles displayed an absorption peak centered at around 325 nm (3.8 eV), together with a tail at lower energy side. Room temperature photoluminescence spectrum of the as-obtained CaTiO₃ nanoparticles upon laser excitation at 325 nm demonstrated a strong and broad visible light emission ranging from about 527 to 568 nm, which may be originated from the surface states and defect levels.     

Solid phase preparation of submicron-sized SrTiO3 crystallites from SrO2 nanoparticles and TiO2 powders

Submicron-sized SrTiO₃ crystallites were prepared by a low temperature solid state method. The proposed preparation method involved two simple steps: firstly, SrO₂ nanoparticles of 35–90 nm were precipitated from the reaction of Sr(NO₃)₂ and H₂O₂ in an alkalescent aqueous solution (pH = 8) under the ambient condition; secondly, perovskite phase SrTiO₃ with a minor amount of SrCO₃ impurity were produced by heating the mixture of excessive SrO₂ nanoparticles and commercial TiO₂ powders in air at 700 °C for 10 h, which could be easily washed with 1 mol/l HNO₃ aqueous solution and distilled water to yield pure SrTiO₃ crystallites with the size of about 125–320 nm. The phase, purity and size of the as-obtained product were characterized by means of powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM).     

A simple route to synthesis of BaCO3 nanostructures in water/ethylene glycol mixed solvents

Barium carbonate (BaCO₃) nanostructures with different morphologies were synthesized using Ba(NO₃)₂ and (NH₄)₂CO₃ in the water/ethylene glycol (EG) mixed solvents by oil bath heating at 80 °C for 30 min. The molar ratio of water to EG had an effect on the morphology of BaCO₃. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM).     

Hydrothermal synthesis of alpha Fe2O3 nanoparticles capped by Tween-80

Surface modified α-Fe₂O₃ nanoparticles capped by Tween-80 were prepared by the hydrothermal treatment of Fe(NO₃)₂.9H₂O at 200 °C. The spherical nanoparticles possessed good crystallinity with an average crystallite size of 21 nm. The presence of Tween-80 on the surface of α-Fe₂O₃ was confirmed by FTIR and Mössbauer analysis. The surfactant was effective in controlling the particle shape and restricted the particle growth to a narrow range around 40-60 nm as observed by scanning electron microscopy. The α-Fe₂O₃ nanoparticles obtained without Tween-80 were irregular in shape with a wide size distribution in the range of 150-300 nm.     

Microwave synthesis of SrCO3 one-dimensional nanostructures assembled from nanocrystals using ethylenediamine additive

One-dimensional SrCO₃ nanostructures assembled from nanocrystals have been successfully synthesized by a microwave-assisted aqueous solution method at 90 °C using Sr(NO₃)₂, (NH₄)₂CO₃ and ethylenediamine (C₂H₈N₂). Our experiments show that the microwave heating time plays an important role in the size and morphology of SrCO₃. A rational mechanism based on the oriented attachment self-assembly is proposed for the formation of SrCO₃ nanostructures. The products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected-area electron diffraction (SAED). This method is simple, fast, low-cost and suitable for large-scale production of SrCO₃ nanostructures with different morphologies. We expect that this method may be extended to the preparation of nanostructures of other kinds of carbonates.     

Low temperature biomimetic synthesis of the Li2ZrO3 nanoparticles containing Li6Zr2O7 and high temperature CO2 capture

Li₂ZrO₃ nanoparticles containing Li₆Zr₂O₇ were prepared by a biomimetic soft solution route and characterized with X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption. The results show that the tetragonal Li₂ZrO₃ nanoparticles containing monoclinic Li₆Zr₂O₇ can be obtained using this simple method. The mean diameter of the nanoparticles is approximately 90 nm and the corresponding specific surface area is 23.7 m² g^− 1. Moreover, the Li₂ZrO₃ nanoparticles obtained were thermally analyzed under a CO₂ flux to evaluate their CO₂ capture capacity at high temperature. It was found that the as-prepared Li₂ZrO₃ nanoparticles would be an effective acceptor for high temperature CO₂ capture.     

Synthesis and characterization of stable and crystalline Ce0.6Y0.4O1.8 nanoparticle sol

Ce_0.6Y_0.4O_1.8 (40YCO) nanoparticle sol was synthesized via the hydrolysis of a Ce-Y-triethanolamine (TEA) complex derived from the reaction of hydrate cerium (III) nitrate (Ce(NO₃)₃·6H₂O), yttrium nitrate (Y(NO₃)₃·6H₂O) and TEA in alcohol solution at room temperature. The resultant sol possessed excellent UV shielding ability and high transparency in visible light region, and can be stable for one month. Transmission electron microscopy (TEM) showed a particle size distribution of 4.1 ± 0.7 nm for 40YCO. X-ray diffraction (XRD) as well as selected area electron diffraction (SAED) gave evidence that the as-synthesized nanoparticles were well crystalline. The formation of a solid solution was monitored by XRD and ICP-MS. Moreover, zeta potential measurement and infrared spectra were employed to study the YCO particles.     

Synthesis and characterization of bundle-like structures consisting of single crystal Ce(OH)CO3 nanorods

Bundle-like structures consisting of single crystal cerium hydroxide carbonate (Ce(OH)CO₃) nanorods have been synthesized successfully by a hydrothermal method at 100 °C using cerium nitrate (Ce(NO₃)₃·6H₂O) as the cerium source, aqueous carbamide both as an alkaline and carbon source and cetyltrimethylammonium bromide (CTAB) as surfactant. X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were used to characterize such bundle-like structures. SEM and TEM images show that Ce(OH)CO₃ bundle-like structures were composed of nanorods with diameters of ∼ 100 nm. The XRD pattern and electron diffraction (ED) pattern indicate that Ce(OH)CO₃ has a pure orthorhombic single crystal structure.     

Synthesis of single-crystalline Ce(CO3)(OH) with novel dendrite morphology and their thermal conversion to CeO2

Single-crystalline cerium carbonate hydroxide (Ce(CO₃)(OH)) with dendrite morphologies have been successfully synthesized by hydrothermal method at 150 °C using Ce(NO₃)₃·6H₂O as the cerium source, aqueous carbamide as both an alkaline and carbon source and poly(vinyl pyrrolidone) (PVP) as surfactant. Ceria (CeO₂) with dendrite morphologies have been fabricated by a thermal decomposition-oxidation process at 500 °C for 6 h using single-crystalline Ce(CO₃)(OH) dendrites as the precursor. The dendrite morphologies of Ce(CO₃)(OH) was sustained after thermal decomposition-oxidation to CeO₂. The as-prepared products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TG).     

Ag-catalyzed synthesis of europium borate Eu(BO2)3 nanowires, growth mechanism and luminescent properties

Eu(BO₂)₃ nanowires with diameters of 10-20 nm were fabricated through direct sintering Eu(NO₃)₃·6H₂O and H₃BO₃ with Ag as catalyst. The result of X-ray diffraction (XRD) indicated that the nanowire was single-crystalline with body-centered monoclinic structure. Based on the fact that Ag nanoparticles attached to the tips and middles of nanowires, a vapor-liquid-solid (VLS) growth mechanism of the Eu(BO₂)₃ nanowires is proposed. Three well-defined stages have been clearly identified during the process: Ag-Eu-B-O cluster process, crystal nucleation, and axial growth. The photoluminescence characteristics under UV excitation were investigated. The dominated Eu³⁺ orange-red emission corresponding to the magnetic dipole transition ⁵D₀ → ⁷F₁ is centered at 591 nm, indicating that Eu³⁺ is located at high symmetry crystal field with inversion center.     

Hydrothermal fabrication of various morphological α-Fe2O3 nanoparticles modified by surfactants

Two kinds of various morphological α-Fe₂O₃ nanoparticles modified by anionic surfactant (sodium dodecylsulfonate, SDS) and cationic surfactant (hexadecyipyridinium chloride, HPC), respectively, have been synthesized via hydrothermal method, using simple inorganic salt (NH₄)₃Fe(C₂O₄)₃ and alkali NaOH as starting precursors. Meanwhile, α-Fe₂O₃ nanoparticles without surfactant are also fabricated under the same conditions for comparison. The resultant products were characterized by means of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron micrograph (TEM) combined with electron diffraction (ED) and magnetization measurements. It is interesting that the obtained α-Fe₂O₃ nanoparticles without surfactant are polyhedral with average particle size of 90 ± 35 nm; while the obtained α-Fe₂O₃ nanoparticles modified by SDS are ellipsoidal with mean particle size of major axis: ca. 420 nm; minor axis: ca. 205 nm and those modified by HPC are spherical with mean particle size of ca. 185 nm observed from TEM. In addition, magnetic hysteresis measurements reveal that the α-Fe₂O₃ nanoparticles modified by two surfactants show enhancement in coercivity (H_c) and the remanent magnetization (M_r) compared with those of the obtained α-Fe₂O₃ nanoparticles without surfactant at room temperature. The experimental results suggest that the surfactants not only significantly influence the size and shape of the particles, but also their magnetic properties.     

Green synthesis of ZnO2 nanoparticles from hydrozincite and hydrogen peroxide at room temperature

A green method based on the reaction between hydrozincite (Zn₅(CO₃)₂(OH)₆) powder and hydrogen peroxide (H₂O₂, 30 wt.%) in aqueous solution at room temperature was developed for the synthesis of ZnO₂ nanoparticles. Results from X-ray diffraction, transmission electron microscopy and Raman demonstrated that the resultant products were pure cubic phase ZnO₂ nanoparticles, whose sizes were in the range of 3.1-4.2 nm. Thermogravimetric analysis indicated that between 180 and 350 °C, the as-synthesized ZnO₂ nanoparticles had a weight loss of about 16.7%, consistent with the theoretical amount (16.4%) of the O₂ released from ZnO₂ decomposition (ZnO₂ = ZnO + 1/2O₂). The present method was green, simple and cost-effective, which should be suitable for large-scale production of multifunctional ZnO₂ nanoparticles.     

Synthesis of GaN nanoparticles from NH4[Ga(OH)2CO3] under a flow of ammonia gas

In this investigation, we report the synthesis of gallium nitride (GaN) nanoparticles from ammonium-carbonato-dihydroxo-gallate (NH₄[Ga(OH)₂CO₃]) in the flow of NH₃ gas in a temperature range of 500-900 °C. The GaN nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR). The FTIR and XPS revealed that the conversion of NH₄[Ga(OH)₂CO₃] to GaN under a flow of ammonia proceeds stepwise via amorphous gallium oxynitrides (GaO_xN_y) intermediates. Nanosized GaN particles with an average diameter of approximately 20-40 nm were obtained. The results obtained demonstrate that the large-quantity nanosized GaN particles can be synthesized from NH₄[Ga(OH)₂CO₃] powders.     

A mild solvothermal route to α-Fe2O3 nanoparticles

A mild solvothermal route has been developed to synthesize α-Fe₂O₃ nanoparticles using Fe(NO₃)₃ as a starting material. The results from XRD and TEM indicate the α-Fe₂O₃ powders possess a rhombohedrally centered hexagonal structure, and the size of particles from alcohothermal method at 160 °C is about 50-100 nm.     

Hydrothermal synthesis of GdBO3:Eu nanofibres

Large-scale GdBO₃:Eu³⁺ nanofibres with uniform diameter were controllably synthesized by a glycine-assisted hydrothermal method at 170 °C using Gd(NO₃)₃, Eu(NO₃)₃ and Na₂B₄O₇·10H₂O as the precursors. X-ray diffraction (XRD) results show that the luminescent nanofibres are pure hexagonal structure and no other impurity phase appeared. Transmission electron microscopy (TEM) studies indicate that GdBO₃:Eu³⁺ has a nanofibre structure. Photoluminescence (PL) spectra results demonstrate that the GdBO₃:Eu³⁺ nanofibres have three strong ⁵D₀ → ⁷F₁ (595 nm) and ⁵D₀ → ⁷F₂ (613 and 627 nm) transition peaks corresponding to orange-red and red colors, respectively.     

Flame-made single phase Zn2TiO4 nanoparticles

Using zinc naphthenate and titanium tetra isopropoxide (1:1 mol.%) dissolved in ethanol as precursors, single phase Zn₂TiO₄ nanoparticles were synthesized by the flame spray pyrolysis technique. The Zn₂TiO₄ nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). The BET surface area (SSA_BET) of the nanoparticles was measured by nitrogen adsorption. The average diameter of Zn₂TiO₄ spherical particles was in the range of 5 to 10 nm under 5/5 (precursor/oxygen) flame conditions. All peaks can be confirmed to correspond to the cubic structure of Zn₂TiO₄ (JCPDS No. 25-1164). The SEM result showed the presence of agglomerated nanospheres with an average diameter of 10-20 nm. The crystallite sizes of spherical particles were found to be in the range of 5-18 nm from the TEM image. An average BET equivalent particle diameter (d_BET) was calculated using the density of Zn₂TiO₄.     

Characterization of Bi2S3 with different morphologies synthesized using microwave radiation

Bi₂S₃ with different morphologies (nanoparticles, nanorods and nanotubes) was synthesized using bismuth nitrate pentahydrate (Bi(NO₃)₃·5H₂O) and two kinds of sulfur sources (CH₃CSNH₂ and NH₂CSNH₂) in different solvents (water, ethylene glycol and propylene glycol) via a microwave radiation method at 180 W for 20 min. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that all of the products are orthorhombic Bi₂S₃ phase of nanoparticles, nanorods and nanotubes, influenced by the sulfur sources and solvents. Formation mechanisms of the products with different morphologies are also proposed.     

Synthesis of sodium iron silicate(NaFe(III)[SiO3]2) nanorods and electrochemical characterization

Sodium iron silicate (NaFe(III)[SiO₃]₂) nanorods have been synthesized using iron nitrate (Fe(NO₃)₃) and sodium silicate (Na₂SiO₃) solutions by means of hydrothermal method. The mixture solution is processed in hydrothermal autoclave first at 180-200 °C for two days and then dried at 70 °C to obtain nanotructured NaFe(III)[SiO₃]₂. It was revealed that NaFe(III)[SiO₃]₂ nanorod with the average diameter of ~ 15 nm and length of several hundreds nm was confirmed by X-ray power diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Cyclic voltammeter (CV) and electrochemical impedance spectra (EIS) investigations show that this kind of NaFe(III)[SiO₃]₂ nanostructures have evident and stable electrochemical redox behavior between potential range of − 0.1-0.55 V in alkaline solution.     

Synthesis and microwave dielectric properties of CaO-MgO-SiO2 submicron powders doped with Li2O-Bi2O3 by sol-gel method

Using Ca(NO₃)₂·4H₂O, Mg(NO₃)₂·6H₂O, Si(OC₂H₅)₄, LiNO₃ and Bi(NO₃)₃·5H₂O as raw materials, CaO-MgO-SiO₂ submicron powders were prepared at low temperature by sol-gel method. The crystallization temperature was decreased enormously by the introduction of Li-Bi liquid phase sintering aids into Ca-Mg-Si sol, and the powders with average particle sizes of 80-100 nm and 200-400 nm were obtained at the calcining temperature of 750 °C and 800 °C, respectively. The sintering characteristic and dielectric properties of powders calcined at 750 °C with different content of powders calcined at 800 °C were studied. When the content of powders calcined at 800 °C was 10 wt%, the dielectric ceramic sintered at 890 °C had compact structure, and possessed excellent microwave dielectric properties: ?_r = 7.16, Q × f = 25630 GHz, τ_f = −69.26 ppm/°C.