l-Cystine-assisted growth of Sb2S3 nanoribbons via solvothermal route

l-Cystine was successfully used as a novel kind of sulfur source to grow Sb₂S₃ nanoribbons at 180 °C for 24 h in a mixed solution made of ethylene glycol and distilled water. The nanoribbons were usually tens of micronmeters in length, typically 100–300 nm in width. The structure of the nanoribbons was determined to be of the orthorhombic phase. A reasonable possible mechanism for the growth of Sb₂S₃ nanoribbon structures has been proposed. The as-obtained Sb₂S₃ products were examined using diverse techniques including X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), selected-area electron diffraction, and high-resolution TEM.     

A solvothermal approach for the size-, shape- and phase-controlled synthesis and properties of CuInS2

In this work, Copper Indium disulfide (CIS) nanoparticles of size ∼ 5 nm were prepared via solvothermal approach in ethanol under the nitrogen atmosphere using copper chloride, indium chloride and thiourea (Tu) as starting materials, without any assistance through organic ligands at the reaction temperature of 150 °C. The factors which might affect the morphology, structure, phase of the product during the synthesis were discussed. It was found that the products were significantly affected by the reaction time and solvent. The morphology, structure, phase constituents and optical properties of the as prepared CIS powders were characterized by X-ray diffraction (XRD), Energy dispersive Spectroscopy (EDS), scanning electron microscopy (SEM) and ultraviolet–visible (UV–Vis) spectrometry respectively. The result shows that the CIS nanoparticles can be synthesized by solvothermal method at a reaction time of 2 h and shows that when the reaction time was increased from 2 h to 48 h, CIS porous flower like nanoparticles were obtained as we increase the reaction time. We also observed that in this process, the phase selection of WZ-CIS or CH-CIS is greatly influence by solvent. We also observed that, in this process sulfur source did not influence the phase but participated in the growth of the nanoparticles.     

Facile synthesis of mesoporous core-shell TiO2 nanostructures from TiCl3

The present study reports the synthesis and formation process of mesoporous core-shell TiO₂ nanostructures by employing a glucose-assisted solvothermal process using water-ethanol mixture as solvent and subsequent calcination process at 550 °C for 4 h. X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy and nitrogen adsorption-desorption analysis were used to investigate the structural properties of these nanostructures. By optimizing the preparation conditions, especially the contents of water and ethanol in the mixture solvent, mesoporous core-shell TiO₂ nanostructures were obtained. These mesoporous nanostructures have anatase phase and exhibit the superior photocatalytic activity. This synthesis route is facile due to the usage of stable and low-cost Ti precursor such as TiCl₃ and is thus applicable for large-scale production.     

Polyol mediated synthesis of nanocrystalline M3SbS3 (M=Ag, Cu)

A simple and convenient polyol-mediated route has been developed to produce nanocrystalline Ag₃SbS₃ and Cu₃SbS₃ from AgNO₃ and Cu(NO₃)₂ and SbCl₃ with thiourea at 197 °C. The products were characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Analysis shows that glycol agitated state and injection rate have a great effect on the purity of the final products.     

Synthesis and photocatalytic properties of Zn doped anatase TiO2 nanofibers

Zn²⁺ doped TiO₂ nanofibers were prepared by electrospinning followed by calcination. The results of TGA, FE-SEM, XRD and XPS indicated that the obtained nanofibers with diameter in range of 50–150 nm were composed of anatase TiO₂ phase and Zn²⁺ doping in TiO₂ did not distort the pristine crystal structure of TiO₂. Besides methylene blue (MB) was employed to investigate photocatalytic properties of the obtained samples. The results revealed that Zn²⁺ doped TiO₂ nanofibers had excellent photocatalytic activity, which was symbolized by an optimum photodegradation efficiency of 96.1% under Zn²⁺ doping concentration of 2 at.%. The photocatalytic efficiency of 2 at.% Zn²⁺ doped TiO₂ nanofibers still exceeded 95% after using for five times.     

Sand flower layered double hydroxides synthesized by co-precipitation for CO2 capture: Morphology evolution mechanism,agitation effect and stability

Magnesium–aluminum layered double oxides (Mg–Al-LDO) derived from calcination of layered double hydroxides (LDH) is one of the most capable candidates for CO₂ capture. LDHs with sand flower and dense layered morphology are prepared by co-precipitation method at pH = 10 under different condition with and without stirring. The sand flower LDH prepared with stirring has better CO₂ adsorption performance. Additionally, the sand flower morphology under calcination can be preserved very well, while the morphology can only remain stable below 100 °C after hydrothermal treatment and reconstruction. The formation process of the sand flower LDH is investigated in detail and the related morphology evolution mechanism is proposed. This study can provide insight into the effect of mechanical interaction on chemical reaction and give a new way to control the morphology of layered materials.     

Carbon-nanotube-supported Ag and Cu2O nanoparticles: Dendrimer-mediated synthesis and their broadband optical limiting properties

Multiwalled carbon nanotubes (MWCNTs) were covalently functionalized with fourth-generation poly(amido amine) (PAMAM) dendrimers with a trimesyl core (DT4), and the as-synthesized MWCNT-DT4 was used as the template for in situ growth of Ag and Cu₂O nanoparticles on MWCNTs. Extensive characterizations of the resultant hybrids have been performed using X-ray diffraction, transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy, selected area electron diffraction, thermal gravimetric analysis, and X-ray photoelectron spectroscopy. The side-wall of the nanotubes was uniformly coated with the nanoparticles with mean sizes of 7–8 nm. The optical limiting property measurements of the nanoparticle-modified MWCNTs were carried out by the open-aperture z-scan technique. The results demonstrate that the samples suspended in water show broadband OL performance, and their OL behavior is better than that of MWCNT-DT4 in water due to the presence of Ag and Cu₂O nanoparticles.     

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).     

Facile synthesis of α-MnO2 nanostructures for supercapacitors

Various α-MnO₂ nanostructures have been successfully synthesized by a simple hydrothermal method based on the redox reactions between the MnO₄⁻ and H₂O in mixture containing KMnO₄ and HNO₃. The effect of varying the hydrothermal time to synthesize MnO₂ nanostructures and the forming mechanism of α-MnO₂ nanorods were investigated by using XRD, SEM and TEM. The results revealed an evolvement of morphologies ranging from brushy spherical morphology to nanorods depending upon the hydrothermal time. The surface area of the synthesized nanomaterials varied from 89 to 119 m²/g. Electrochemical properties of the products were evaluated using cyclic voltammetry and galvanostatic charge–discharge studies, and the sample obtained by hydrothermal reaction for 6 h at 120 °C showed maximum capacitance with a value of 152 F/g. In addition, long cycle life and excellent stability of the material were also demonstrated.     

Hybrid photoelectrode by using vertically aligned rutile TiO2 nanowires inlaid with anatase TiO2 nanoparticles for dye-sensitized solar cells

We report a hybrid photoelectrode fabricated by using single crystalline rutile TiO₂ nanowires (NWs) inlaid with anatase TiO₂ nanoparticles (NPs) for efficient dye-sensitized solar cells. For this purpose, ∼4-μm-thick vertically aligned NWs were synthesized on the FTO glass substrate through a solvothermal treatment. Then, as-prepared NW film was treated with the NP colloidal dispersion to construct the NW–NP film. In particular, the NWs offer a fast pathway for electron transport as well as light scattering effect. On the other hand, the inlaid NPs give an extra amount of space for the dye-uptake. Accordingly, the present NW–NP electrode exhibited 6.2% of the conversion efficiency, which corresponds to ∼48% improvement over the efficiency of the NP-DSC. We attribute this notable result to the synergetic effects of the enhanced light confinement, charge collection, and dye-loading.     

Synthesis and selective gas-sensing properties of hierarchically porous intestine-like SnO2 hollow nanostructures

Hierarchically porous intestine-like SnO₂ hollow nanostructures of different dimension were successfully synthesized via a facile, organic template free, H₂O₂-assisted method at room temperature. The morphology as well as texture (congregated solid sphere, intestine-like solid nanostructure, hollow core–shell one, and intestine-like hollow one) of SnO₂ materials can be controlled by varying H₂O₂ concentration and the size of intestine-like hollow SnO₂ can be tuned in the range of 20–120 nm by changing SnSO₄ concentration. The hierarchically porous intestine-like SnO₂ has high specific surface area (142 m² g⁻¹). The gas-sensing behaviors of the intestine-like SnO₂ material to different gas probes such as ethanol, H₂, CO, methane, and butane have been investigated; among them a high selectivity to ethanol was achieved.     

Fabrication of hollow-sphere films of wurtzite CuInS2 on copper substrate

As important semiconductors, I–III–VI₂ compounds have attracted wide attention, among which the wurtzite structured CuInS₂ has been the research focus due to its metastable phase. In this paper, the wurtzite CuInS₂ hollow-sphere films have been successfully prepared on copper substrate in a self-designed solvothermal detached system. The films of Cu(OH)₂ one-dimensional nanostructure arrays and thioacetamide were used as the precursors and triethylene glycol was used as the solvent. Experiments showed that the amount of indium trichloride played a determinative role in the final morphology of the products. Meanwhile, the one-dimensional nanostructure arrays and the detached solvothermal system have great influences on the crystal shape as well. Based on the experimental results, a possible formation mechanism for the CuInS₂ hollow spheres was also proposed. The UV–Vis absorption spectrum showed a broad absorption over the entire visible light and extending into the near-infrared region and presented the band gap of 1.53 eV for the as-prepared wurtzite CuInS₂, which indicates the potential applications in solar cells.     

Synthesis, characterization, and hydrophobic properties of Bi2S3 hierarchical nanostructures

Novel Bi₂S₃ hierarchical nanostructures self-assembled by nanorods are successfully synthesized in mild benzyl alcohol system under hydrothermal conditions. The hierarchical nanostructures exhibit a flower-like shape. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) were used to characterize the as-synthesized samples. Meanwhile, the effect of various experimental parameters including the concentration of reagents and reaction time on final product has been investigated. In our experiment, PVP plays an important role for the formation of the hierarchical nanostructures and the possible mechanism was proposed. In addition, Bi₂S₃ film prepared from the flower-like hierarchical nanostructures exhibits good hydrophobic properties, which may bring nontrivial functionalities and may have some promising applications in the future.     

Silver nanoparticles: Large scale solvothermal synthesis and optical properties

Silver nanoparticles have been successfully synthesized by a simple and modified solvothermal method at large scale using ethanol as the refluxing solvent and NaBH₄ as reducing agent. The nanopowder was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), dynamic light scattering (DLS), UV-visible and BET surface area studies. XRD studies reveal the monophasic nature of these highly crystalline silver nanoparticles. Transmission electron microscopic studies show the monodisperse and highly uniform nanoparticles of silver of the particle size of 5 nm, however, the size is found to be 7 nm using dynamic light scattering which is in good agreement with the TEM and X-ray line broadening studies. The surface area was found to be 34.5 m²/g. UV-visible studies show the absorption band at ∼425 nm due to surface plasmon resonance. The percentage yield of silver nanoparticles was found to be as high as 98.5%.     

Effect of V doping concentration on the electronic structure,optical and photocatalytic properties of nano-sized V-doped anatase TiO2

V-doped TiO₂ with V/Ti ratio of 1–5% has been synthesized by hydrothermal method and then characterized by XRD, TEM, BET specific surface area, XPS and UV–vis. absorption spectra. The photocatalytic activity of the as-synthesized samples was investigated by the degradation of methylene blue in aqueous solution under visible light irradiation. Density functional theory (DFT) based calculations were performed to investigate the mechanism of band gap narrowing, the shift of light absorption edge, the location of V in the TiO₂ lattice and the variation in electronic and optical properties of TiO₂ with the increase of V doping concentration. Irrespective of the V doping concentration, TEM images indicate that all the doped samples were composed of equiaxed spherical anatase TiO₂ particles with good crystallinity and uniform particle size distribution. Both the experimental results from XPS survey and the theoretical calculation argue that the doped V replaces the lattice Ti and form substitutional impurity. The visible light absorption can be optimized by adjusting the V doping concentration. Among the doped samples with different V doping concentrations, the sample with V/Ti ratio of 2% depicts better visible light photocatalytic activity due to the enhanced visible light absorption and improved separation of electron–hole pairs.     

In2O3 hollow spheres: One-step solvothermal synthesis and gas sensing properties

Hollow In₂O₃ spheres were prepared via a P123-assisted one-step solvothermal process for the first time. Ethanol medium played a key role in the direct cubic In₂O₃ phase formation whereas the triblock copolymer acted as a structure directing agent in the formation of the hollow spheres. The gas sensing properties of the as-prepared In₂O₃ hollow spheres were investigated. Compared to the products synthesized without P123, the In₂O₃ hollow spheres exhibited much faster response and higher sensitivity toward HCHO vapor.     

Solvothermal synthesis of chalcopyrite CuIn0.7Ga0.3Se2 nanoparticles and the studies on reaction mechanism and structure defects

By using a solvothermal reaction in ethylenediamine, quaternary chalcopyrite CuIn_0.7Ga_0.3Se₂ nanoparticles have been successfully synthesized at 270 °C. The nanoparticles were characterized by XRD, XPS, TEM, HRTEM. The possible reaction mechanism was simply discussed. The size of nanoparticles ranged from 20 nm to 100 nm, being consistent with the calculated value. We observed point defects and planar defects by using TEM, and the possible formation mechanism was also discussed.     

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.     

Preparation and pseudo-capacitance of birnessite-type MnO2 nanostructures via microwave-assisted emulsion method

A microwave-assisted emulsion process has been developed to synthesize birnessite-type MnO₂ one-dimensional (1D) nanostructures. The prepared samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). TEM images confirmed that the particles were composed of nanowires and nanobelts. As a consequence of the small size, such MnO₂ nanostructures exhibit a high specific capacitance of 277 F g⁻¹ at the current density of 0.2 mA cm⁻². Furthermore, the simple synthetic approach may provide a convenient route for the preparation of birnessite-type MnO₂ nanowires and other 1D nanostructured materials on a large scale.     

Large-scale synthesis and characterization of fan-shaped rutile TiO2 nanostructures

Large-scale fan-shaped rutile TiO₂ nanostructures have been synthesized by means of a simple hydrothermal method using only TiCl₄ as titanium source and chloroform/water as solvents. The physicochemical features of the fan-shaped TiO₂ nanostructures are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), nitrogen absorption-desorption, diffuse reflectance ultraviolet-visible spectroscopy (UV-vis) and Fourier transform infrared spectroscopy (FTIR). Structural characterization indicates that the fan-shaped TiO₂ nanostructures are composed of several TiO₂ nanorods with diameters of about 5 nm and lengths of 300-350 nm. The average pore size and BET surface area of the fan-shaped TiO₂ nanostructures are 6.2 nm and 59 m²/g, respectively. Optical adsorption investigation shows that the fan-shaped TiO₂ nanostructures possess optical band gap energy of 3.11 eV.