Facile and large-scale synthesis of hollow TiO2 nanostructures from TiCl3 solution

Hollow TiO₂ nanostructures were successfully synthesized by a hydrothermal process using TiCl₃ solution as Ti sources. The as-obtained product consists of quasi-spherical hollow nanostructures in the diameter of about 500 nm with anatase phase. The control experiments indicated that the synergism of H₂O₂ and KBF₄ plays an important role in the formation of hollow TiO₂ nanostructures. Compared with solid TiO₂ nanostructures, the photocatalytic property of hollow TiO₂ nanostructures has been markedly improved in degradation of methyl orange under UV light. This synthesis procedure is facile and thus promotes large-scale production of hollow TiO₂ nanostructures.     

Self-template route to MnO2 hollow structures for supercapacitors

Birnessite-type MnO₂ hierarchical hollow structures were prepared through a self-template route, by the direct reaction between the aqueous solution of KMnO₄ and solid MnCO₃ precursor crystals, and followed by the removal of MnCO₃ core with HCl. Field emission scanning microscopy (FESEM) images indicate that the shells of hierarchical hollow structures consist of the interconnected sheets with a thickness of about 30 nm, and transmission electron microscopy (TEM) images show that the thickness of the shells can be adjusted over a range from 50 to 80 nm by changing the molar ratio of MnCO₃/KMnO₄. The electrochemical properties of the as-prepared MnO₂ were characterized by cyclic voltammetry (CV) and galvanostatic charge-discharge tests in 1 M Na₂SO₄ solution. The sample obtained at a higher MnCO₃/KMnO₄ molar ratio (i.e., 50:1) shows a relatively higher specific capacitance of 169 F g^− 1 than 111 F g^− 1 of the sample obtained under a lower molar ratio of 25:1 at the current density of 250 mA g^− 1.     

Facile synthesis of water-soluble YF3 and YF3: Ln nanocrystals

Water-soluble lanthanide-doped YF₃ nanocrystals with cubic structure were successfully synthesized for the first time using a simple solvothermal method with ethanol as solvent at 160 °C for 12 h. SEM and TEM results demonstrated that the obtained nanocrystals have an irregular shape and an average size of below 30 nm. Tb³⁺, Tb³⁺/Ce³⁺ co-doped YF₃ nanocrystals were also prepared and their photoluminescence properties were investigated. The luminescent intensity of the Tb³⁺ for the Tb³⁺/Ce³⁺ co-doped YF₃ nanocrystals is about ten times higher than that of the Tb³⁺ doped YF₃ nanocrystals. The products were characterized by XRD, SEM and TEM. Owing to their water-soluble properties and high processability, extensive applications may be found.     

Facile one-pot synthesis and drug storage/release properties of hollow micro/mesoporous organosilica nanospheres

Novel hollow micro/mesoporous organosilica nanospheres (HMOSNs) of uniform diameter and shell thickness of about 90 nm and 15 nm, respectively, and with wormlike micro/mesoporous shell full of uramido groups, have been successfully fabricated by a facile one-pot route. The micro/mesoporosity of the synthesized HMOSNs has been characterized by small-angle and wide-angle X-ray diffraction (XRD), scan electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption-desorption measurements. The drug storage and release properties of the synthetic HMOSNs are measured by using ibuprofen (IBU) as a model drug, and a high drug storage capacity of 531 mg IBU per gram HMOSNs and a steady drug release behavior are exhibited.     

Solvothermal synthesis of In(OH)3 nanorods and their conversion to In2O3

In this work, we demonstrate that monodisperse indium hydroxide (In(OH)₃) nanorods constructed with parallel wire-like subunits have been fabricated via a acrylamide-assisted synthesis route without any template. NH₃ from the hydrolysis of acrylamide acts as the OH⁻ provider. The structure and morphology of as-prepared products have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and thermogravimetric analysis (TG). A detailed mechanism has been proposed on the basis of time-dependent experimental results. Furthermore, by annealing In(OH)₃ precursors at 500 °C for 3 h in air, In₂O₃ samples were obtained with the designed morphology.     

Selective synthesis of Ni3S4 nanocrystallites with hollow structures through a solution-phase approach

Ni₃S₄ nanocrystallites with hollow structures were selectively fabricated through a facile solution-phase approach. The experimental results revealed that the volume ratio of ethanol or ethylene glycol played an important role on the phases of the products based on XRD characterization. The optical property of the as-prepared Ni₃S₄ was evaluated using UV–vis spectrum at ambient temperature.     

Effect of mixed solvent on the morphologies of nanostructured Bi2S3 prepared by solvothermal synthesis

Different morphologies of nanostructured bismuth sulfide (Bi₂S₃) including nanotubes and nanorods have been prepared by solvothermal synthesis at a low temperature of 120 °C for 12 h using various mixed solvents as the reaction medium and urea as the mineralizer. X-ray diffraction analysis showed that all the as-prepared Bi₂S₃ samples are orthorhombic phase. Transmission electron microscopy analysis showed that the morphologies of the nanostructures are mainly related to the viscosity and surface tension of the mixed solvent used in the solvothermal synthesis.     

Direct synthesis and characterization of spongy CuO with nanosheets from Cu3(btc)2 microporous metal-organic framework

Spongy CuO was successfully synthesized via direct pyrolysis of Cu₃(btc)₂ (btc = benzene-1,3,5-tricarboxylate) microporous metal-organic framework (MOF) in a horizontal tube furnace in the air, in which the Cu₃(btc)₂ was used as the Cu source and complexing molecule precursor. The as-prepared products were characterized by a series of techniques including XRD, SEM, EDX, TEM, and SAED. Results from SEM showed that the as-prepared spongy CuO with average diameter altering from 10 to 20 μm consists of nanosheets with average edge length in the range of 80-200 nm and thickness of about 30 nm, which was also confirmed by TEM analysis. The XRD and SAED results showed that a purity phase of CuO was obtained after pyrolysis. It was also found that the reaction temperature played a key role in the formation of spongy CuO microstructures. The spongy material could be found potential application in various fields such as catalysis, absorption, and gas sensing.     

Solid state-hydrothermal synthesis and photoluminescence of LaVO4: Eu nanophosphors

A modified hydrothermal process is engaged in the synthesis of LaVO₄: Eu³⁺ nanophosphor. All kinds of inorganic salts (solid state hydrated rare earth nitrates and NH₄VO₃) and precipitation reagents (ammonia and urea) are mixed to form the solid state precursors instead of general aqueous solution systems, and a little amount water exists in the hydrothermal reaction systems. Both X-ray powder diffraction (XRD) and transmission scanning electronic microscope (TEM) shows that the uniform microstructure with the particle size of around 60 nm and the product from ammonia possesses the higher phase purity than that from urea. LaVO₄: Eu³⁺ shows a strong red emission at 617 nm originating from the ⁵D₀ → ⁷F₂ hypersensitive transition of Eu³⁺ ion. Especially the LaVO₄: Eu³⁺ nanophosphor from ammonia presents the more excellent photoluminescent property (lifetime and quantum efficiency) than that from urea.     

Synthesis and magnetic studies of nano-crystalline GdFeO3

Nano-crystalline GdFeO₃ was synthesized by three different soft-chemical routes viz. hydrothermal, co-precipitation and combustion. The hydrothermal and co-precipitation methods resulted in amorphous powder which on further heating resulted in GdFeO₃. The combustion method produced phase pure GdFeO₃ in a single step. The particle size was in the range of 50-70 nm as calculated by Scherrer's formula. The transmission electron micrographs (TEM) showed the presence of fairly regular particles. Magnetic studies revealed a paramagnetic behavior. The magnetic susceptibility (in emu/g-Oe) of GdFeO₃ samples as synthesized by hydrothermal, co-precipitation and combustion routes was found to be 9.6 × 10^− 5, 6.7 × 10^− 5 and 4.4 × 10^− 5 respectively.     

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.     

Solvothermal synthesis of the special shape (deformable) hollow g-C3N4 nanospheres

Special shaped (deformable) hollow g-C₃N₄ nanospheres were synthesized by the solvothermal technique using silica spheres as template. The X-ray diffraction (XRD) peaks of the product were indexed to g-C₃N₄ materials. Field-Emission Scanning Electron Microscopy and Transmission Electron Microscopy confirmed that the external diameter of the hollow nanospheres is about 130-150 nm and thickness of the wall is about 20-30 nm. The FTIR spectrum showed absorption peak at 810 cm^-1 can be attributed to the s-triazine (C₃N₃) breathing mode. Raman spectrum exhibited two broad peaks approximately at 1360 cm^-1 (D band) and 1580 cm^-1 (G band). The deformed pie shape or mortars like hollow spheres were first reported. The flexility of the deformable hollow g-C₃N₄ nanospheres may be used in special field such as drug delivery carriers adjusting the delivery ratio by the external pressure, and a good material for studying the mechanical properties of the sp² hybrid g-C₃N₄. The photoluminescence spectrum of the product indicates that the deformable hollow g-C₃N₄ nanospheres may have potential applications in nano-optical device fields.     

Synthesis of hollow sphere-like mesoporous silica with reformer naphtha as a swelling agent

Hollow sphere-like and other shaped mesoporous silicas were prepared using reformer naphtha as a swelling agent via a hydrothermal synthesis process. The mesoporous silicas underwent a complicated process in which their morphology was transformed from a red blood cell-like shape to a golf-ball sphere-like shape, and then from a golf-ball-like shape to a hollow sphere-like shape in response to various synthesis temperatures. Under the control of using reformer naphtha, the mesoporous silica was transformed from a wheat-like shape to a sphere-like shape, and then from a sphere-like shape to a hollow sphere-like shape. The effects of temperature and the swelling agent may have contributed to the formation of reformer naphtha microemulsions in the copolymer aqueous solution, followed by the self-assembly of block copolymer micelles and silica around the emulsions.     

NH4Cl-assisted low temperature synthesis of anatase TiO2 nanostructures from Ti powder

A simple, low temperature and low cost method, which was based on heating the mixture of Ti and NH₄Cl powders in air at 300 °C, has been developed for the controlled synthesis of anatase TiO₂ nanostructures including irregular nanoparticle aggregates, curved nanowires built up by the oriented attachment of nanoparticles, and nanoplates constructed with nanoparticles. The characterization results from X-ray diffraction and Raman spectra indicated that the as-obtained products were anatase TiO₂. Field emission scanning electron microscope images revealed that the products obtained for 3, 10 and 16 h comprised, in turn, irregular nanoparticle aggregates (8-55 nm), curved nanowires built up by the oriented attachment of nanoparticles (~ 9 nm), and nanoplates constructed with nanoparticles (~ 8 nm).     

Self-assembly of FeCl3-S nanotrees and their application in directed growth of nanofibers

Nanoscale tree-like FeCl₃-S structures have been assembled. Their unique characteristics, based on the high reactivity of FeCl₃ moiety and the branched thread morphology of sulfur moiety, endow them multiple excellent functions, particularly acting as reactive seeds or templates to directly induce organic polymerization reaction and guide the growth of polymer nanofibers. Using the excellent ability of these tree-like nanostructures, we have synthesized long and flexible polycyclopentadiene nanofibers in one-step process. This result may lead to a new technical way to control the formation of organic polymer nanofibers and to tailor the growth of microstructures by using reactive nanostructures as structure-directing objects.     

Ultrasonic synthesis of the microporous metal-organic framework Cu3(BTC)2 at ambient temperature and pressure: An efficient and environmentally friendly method

A three-dimensional (3-D) metal-organic framework (MOF) with 3-D channels, i.e. Cu₃(BTC)₂ (HKUST-1, BTC = benzene-1,3,5-tricarboxylate), was synthesized by using ultrasonic method for the first time. The reaction of cupric acetate and H₃BTC in a mixed solution of DMF/EtOH/H₂O (3:1:2, v/v) under ultrasonic irradiation at ambient temperature and atmospheric pressure for short reaction times (5-60min) gave Cu₃(BTC)₂ in high yields (62.6-85.1%). These Cu₃(BTC)₂ nano-crystals have dimensions of a size range of 10-200 nm, which are much smaller than those synthesized using conventional solvothermal method. There were no significant differences in physicochemical properties, e.g. BET surface area, pore volume, and hydrogen storage capacity, between Cu₃(BTC)₂ nano-crystals prepared using ultrasonic method and the microcrystals obtained by using improved solvothermal method. Compared with traditional synthetic techniques, such as solvent diffusion technique, hydrothermal and solvothermal methods, ultrasonic method for the construction of porous MOFs was found to be highly efficient and environmentally friendly.     

Preparation of Bi2S3 nanorods via a hydrothermal approach

Large-scale bismuth sulfide (Bi₂S₃) nanorods with uniform size have been prepared by hydrothermal method using bismuth chloride (BiCl₃) and sodium sulfide (Na₂S·9H₂O) as raw materials at 180 °C and pH = 1-2 for 12 h. The powder X-ray diffraction (XRD) pattern shows the Bi₂S₃ crystal belongs to the orthorhombic phase with calculated lattice constants a = 1.1187 nm, b = 1.1075 nm and c = 0.3976 nm. Furthermore, the quantification of X-ray photoelectron spectra (XPS) analysis peaks gives an atomic ratio of 1.9:3.0 for Bi:S. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopic (TEM) studies reveal that the appearance of the as-prepared Bi₂S₃ is rod-like with typical lengths in the range of 2-5 μm and diameters in the range of 10-30 nm. Finally the influences of the reaction conditions are discussed and a possible mechanism for the formation of Bi₂S₃ nanorods is proposed.     

Facile solution synthesis and characterization of CaCO3 microspheres with urchin-shaped structure

Urchin-shaped CaCO₃ microspheres were successfully synthesized by a facile low-temperature solution-phase method. The product was characterized with X-ray diffraction (XRD), Raman spectra and high resolution transmission electron microscopy (HRTEM). The characterization results revealed that the structure of the urchin-shaped CaCO₃ was grown along the (104) crystal plane with a calcite structure. Furthermore, the valence states and the surface chemical compositions of CaCO₃ were further identified by X-ray photoelectron spectroscopy (XPS). This study provides a simple method to prepare urchin-shaped CaCO₃ microspheres in large scale, which broads their practical applications.     

Room temperature synthesis and characterization of different morphological TbF3 nano/microcrystals

At room temperature, a simple solution-based procedure employing NaBF₄ as the fluoride source has been developed to selectively prepare different morphological TbF₃ nano/microcrystals (disks, peanuts and spindles) with an orthorhombic structure. The crystal structure, morphology and photoluminescence properties of the as-prepared TbF₃ crystals were investigated by x-ray powder diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectrophotometer. The results revealed that large-scale and uniform disks with a mean thickness of 20 nm can be easily synthesized, and the spindle-like and peanut-like TbF₃ crystals were assembled from nanodisks. The effects of synthesis parameters such as NaBF₄, reaction time and molar ratio of the reactants were systematically investigated. The room temperature PL properties of these different morphological TbF₃ microcrystals were measured.     

Controllable synthesis of monodisperse Mn3O4 and Mn2O3 nanostructures via a solvothermal route

A facile one-step solvothermal route was developed to synthesize monodisperse Mn₃O₄ and Mn₂O₃ nanostructures with the introduction of poly(vinyl-pyrrolidone)/stearic acid (PVP/SA) mixture. H₂O₂ played a key role in the determination of the products Mn₃O₄ and Mn₂O₃. The synthesis parameters for nanostructured MnO_x such as surfactant and reaction time were investigated, along with their influences on morphology and composition. The morphology evolution of the Mn₃O₄ and Mn₂O₃ reveals that the nanostructures formed via two distinct mechanisms of nucleation and growth of nanocrystals.