Au/ZnO nanocomposites: Facile fabrication and enhanced photocatalytic activity for degradation of benzene

Au nanoparticles supported on highly uniform one-dimensional ZnO nanowires (Au/ZnO hybrids) have been successfully fabricated through a simple wet chemical method, which were first used for photodegradation of gas-phase benzene. Compared with bare ZnO nanowires, the as-prepared Au/ZnO hybrids were found to possess higher photocatalytic activity for degradation of benzene under UV and visible light (degradation efficiencies reach about 56.0% and 33.7% after 24 h under UV and visible light irradiation, respectively). Depending on excitation happening on ZnO semiconductor or on the surface plasmon band of Au, the efficiency and operating mechanism are different. Under UV light irradiation, Au nanoparticles serve as an electron buffer and ZnO nanowires act as the reactive sites for benzene degradation. When visible light is used as the light irradiation source, Au nanoparticles act as the light harvesters and photocatalytic sites alongside of charge-transfer process, simultaneously.     

Controllable fabrication of various ZnO micro/nanostructures from a wire-like Zn-EG-AC precursor via a facile solution-based route

In this paper, ZnO particles with various morphologies were prepared though a facile solution-based route. The complexes Zn-EG-AC (EG: ethylene glycol; AC: CH₃COO⁻ groups) obtained by reaction of anhydrous zinc acetate and EG were used as precursors. It is found that the precursor could transform into ZnO in water with no need of assistant of additional alkali as it is sensitive to water. At the same time, it is well dispersed in reaction medium (water and ethanol). Experimental results showed that ZnO particles with various morphologies, such as the hexagonal rings, the hexagonal plates, the tubes, the prisms, and some interesting hierarchical structures, could be obtained by controlling hydrolysis of precursor in water and water/ethanol medium through finely tuning the experimental parameters. The success of shape-controllable fabrication was related intimately with the Zn-EG-AC precursor used in our synthesis.     

Synthesis of cup-like ZnO microcrystals via a CTAB-assisted hydrothermal route

Cup-like ZnO microcrystals were successfully synthesized by using a CTAB-assisted hydrothermal route. Zn(CH₃COO)₂·2H₂O was used as the only precursor to generate cup-like ZnO microcrystals. The morphologies and structures of the samples were characterized by XRD and SEM. The XRD pattern shows that the cup-like ZnO microcrystals are hexagonal. The SEM investigation reveals that the as-prepared ZnO product has cup-like morphology. CTAB was found to play a crucial role in determining the cup-like morphologies. A possible formation process of the cup-like ZnO microcrystals was proposed. Optical property of the product was also investigated by fluorophotometer at room temperature.     

Preparation polystyrene/multiwalled carbon nanotubes nanocomposites by copolymerization of styrene and styryl-functionalized multiwalled carbon nanotubes

Styryl-functionalized multiwalled carbon nanotubes (p-MWNTs) were prepared by esterification based on the carboxylate salt of carbon nanotubes and p-chloromethylstyrene in toluene. Then in situ radical copolymerization of p-MWNTs and styrene initiated by 2,2′-azobis(isobutyronitrile) (AIBN) was applied to synthesize composites of styryl-functionalized multiwalled carbon nanotubes and polystyrene (PS) (p-MWNTs/PS). Characterizations carried out by FT-IR, ¹H NMR, UV–vis show that styryl group covalently bond to the surface of MWNTs. The results of UV showed that the solutions of p-MWNTs/PS in chloroform have the hyperchromic effect. Transmission electron microscopy (TEM) images of p-MWNTs/PS composites and scanning electron microscopy (SEM) images of fracture surface of p-MWNTs/PS composites showed the functionalized nanotubes had a better dispersion than that of the unfunctionalized MWNTs in the matrix. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) suggested that the thermal stability of p-MWNTs/PS composites improved in the presence of MWNTs.     

An organometallic route to highly monodispersed silver nanoparticles and their application to ink-jet printing

Highly monodispersed silver nanoparticles were successfully synthesized by thermolysis of silver alkanoate precursors and were characterized by X-ray diffraction, TGA/DTA and transmission electron microscopy. The results showed that these nanoparticles exhibit spherical shape with FCC crystal structure. The relationship between the carbon chain length and the monodispersity of the nanoparticles was investigated. Furthermore, the size of the particles was controlled by varying the concentration of the stabilizing surfactants. The silver nanoparticles were easily re-dispersed into n-tetradecane and printed onto various substrates using a Microfab head with a single nozzle. The ink-jet printed patterns were sintered at 250 °C and their electrical resistivity was about 6 μΩ cm.     

A new hydrothermal route to nano- and microstructures of trigonal selenium exhibiting diverse morphologies

High purity single crystalline trigonal selenium (t-Se) with different morphologies (wires, rods, flowerlike, and hollow spheres) have been synthesized under hydrothermal conditions through simple one-step at lower temperature (120 °C) using in situ generated sulphurous acid as a new reducing agent. It is noted that the experimental parameters such as reaction duration, temperature and surfactants have an effective and important influence on the formation of different morphologies. The phase analysis, purity, morphology and optical properties of the as obtained products have been characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis spectroscopy, respectively. A possible reaction scheme as well as growth mechanism has been proposed for the formation of t-Se nanowires.     

Selective synthesis of copper nanoplates and nanowires via a surfactant-assisted hydrothermal process

A facile solution-phase process has been demonstrated for the selective preparation of single-crystalline Cu nanoplates and nanowires by reducing Cu⁺ with ascorbic acid (VC) in the presence of cetyltrimethylammonium bromide (CTAB) or cetyltrimethylammonium chloride (CTAC). To study the formation process of nanoplates and nanowires, samples obtained at various stages of the growth process were studied by TEM and XRD. The possible mechanism was discussed to elucidate the formation of different morphologies of Cu nanostructures. UV–vis spectra of the Cu nanoplates and nanowires were recorded to investigate their optical properties, which indicated that the as-prepared Cu nanostructures exhibited morphology-dependent optical property.     

Microwave-assisted hydrothermal synthesis of coralloid nanostructured nickel hydroxide hydrate and thermal conversion to nickel oxide

Coralloid nanostructured nickel hydroxide hydrate has been successfully synthesized by a simple microwave-assisted hydrothermal process using nickel sulfate hexahydrate as precursor and urea as hydrolysis-controlling agent. A pure coralloid nanostructured nickel oxide can be obtained from the nickel hydroxide hydrate after calcination at 400 °C. The thermal property, structure and morphology of samples were characterized by thermogravimetry (TG), temperature-programmed reduction (TPR), X-ray (XRD), infrared spectroscopy (IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM).     

Synthesis and characterization of In2O3 nanocube via a solvothermal-calcination route

In₂O₃ nanocubes have been generated by a two-step process, a simple solvothermal technique for In(OH)₃ nanocubes and subsequent reaction with O₂ to form the In₂O₃ nanocubes, which exhibit morphologies identical to the original In(OH)₃ nanocube. The In(OH)₃ nanocubes and the In₂O₃ nanocubes are well-crystallized single-crystal nanostructure. Under optimal conversion conditions, the final geometry features of In₂O₃ are predetermined by the size and morphology of the In(OH)₃ nanocubes. The size of In(OH)₃ nanocubes is effected by pH value of solution.     

Synthesis of fluorescent carbon nanoparticles directly from active carbon via a one-step ultrasonic treatment

Water-soluble fluorescent carbon nanoparticles were synthesized directly from active carbon by a one-step hydrogen peroxide-assisted ultrasonic treatment. The carbon nanoparticles were characterized by transmission electron microscopy, optical fluorescent microscopy, fluorescent spectroscopy, Fourier transform infrared spectroscopy and ultraviolet-visible spectrophotometer. The results showed that the surface of carbon nanoparticles was rich of hydroxyl groups resulting in high hydrophilicity. The carbon nanoparticles could emit bright and colorful photoluminescence covering the entire visible-to-near infrared spectral range. Furthermore, these carbon nanoparticles also had excellent up-conversion fluorescent properties.     

Shape-controlled synthesis of manganese oxide nanoplates by a polyol-based precursor route

Manganese oxide nanoplates with different shapes have been prepared based on an ethylene glycol-mediated route. The first step consists of precipitating manganese alkoxide precursor in a polyol process from the reaction of manganese acetate with ethylene glycol. During this process, the morphologies of the prepared precursor could be tuned from disc-shaped to hexagonal nanoplates by introducing different organic additives. The second step involves the treatment of the precursor under different conditions. Crystalline Mn₂O₃ with the same morphology was readily obtained by calcination of the manganese alkoxide precursor. Furthermore, Mn₃O₄ nanoplates could be obtained by immersing the precursor into the deionized water.     

Controllable synthesis of hierarchical nanostructures of CaWO4 and SrWO4 via a facile low-temperature route

CaWO₄ and SrWO₄ nanostructures have been synthesized via a simple microemulsion-mediated route. With careful control of the fundamental experimental parameters including the concentration of reactants, the reaction time and the temperature, the products with different morphologies of dumbbell, coral, rod and dendrite have been obtained, respectively. The possible formation mechanism of these unique morphologies has been proposed based on surfactant self-assembly under different experimental conditions. The as-synthesized CaWO₄ samples with various morphologies exhibit different photoluminescence properties. X-ray powder diffraction, transmission electron microscopy, field-emission scanning electron microscopy, and luminescence spectroscopy were used to characterize these products.     

Facile synthesis via a solvothermal route and characterization of Mg–Al layered double hydroxide (LDH) 3D micro–nano structures

Different Mg–Al layered double hydroxide (LDH) 3D micro–nano structures had been synthesized via a facile solvothermal method. By carefully controlling the fundamental experimental parameters, the morphologies of hexagonal nanoplates, rose-like micro–nano structures, chrysanthemum-like micro–nano structures, and spherical micro–nano structures have been efficiently obtained, respectively. And these micro–nano structures are formed from self-assembly of nanoplates in a spontaneous process in solvothermal system. It is also found that the concentration of the reactant and the dosage of CTAB have significant effects on the morphology of the products. The FT-IR spectra and thermal stability of the micro–nano structures were explored.     

Facile synthesis of chondroitin sulfate-stabilized gold nanoparticles

A facile and simple method for the synthesis of biocompatible gold nanoparticles (AuNPs) at room temperature has been developed by using sodium borohydride as the reducing agent and employing an inexpensive water-soluble chondroitin sulfate (CS) biopolymer as the stabilizing agent. The as-prepared AuNPs were characterized with ultraviolet–visible (UV–vis) spectroscopy and transmission electron microscopy (TEM). Additionally, the stability of AuNPs in aqueous solution was investigated as a function of the electrolyte sodium chloride concentration. The experimental results showed that even high sodium chloride concentration (1 M) also did not destabilize the colloidal gold solution. So it could be speculated that the high stability of AuNPs should be attributed to the electrostatic repulsion and steric hindrance between the AuNPs stabilized by CS molecules, which wrapped around the surface of as-prepared AuNPs and prevented their agglomeration, and simultaneously improve biocompatibility of AuNPs as well.     

Fabrication of boehmite AlOOH nanofibers by a simple hydrothermal process

An experimental procedure is presented for synthesis of AlOOH nanofibers by a hydrothermal process in aqueous solution of cetyltrimethyl ammonium bromide (CTAB) surfactant at 200 °C. The structure, morphology, purity and size of the products are investigated by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and standard selected area electron diffraction (SAED). A possible formation mechanism of the AlOOH nanostructures is proposed based on the reaction dynamics process and the surfactant-assisted growth.     

Synthesis of amorphous calcium phosphate using various types of cyclodextrins

Amorphous calcium phosphate (ACP) was synthesised in aqueous solution at room temperature using cyclodextrins. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and thermal analysis (DTA/TGA) were performed on the calcium phosphate precipitates obtained from solutions. We observed that only β-CD could stabilise the amorphous phase in the mother solution because of the lower solubility of β-CD in water and the ACP remained stable in aqueous solution for more than 24 h at room temperature. The ACP particle has an initial particle size of less than 40 nm, Ca/P molar ratio of 1.67 and β-CD absorbed on its surface. The mechanism for the stabilisation of ACP is proposed.     

Synthesis of barium titanate nanoparticles via a novel electrochemical route

An electrochemical route from Ti metal plate in KOH and Ba(OH)₂ electrolyte at room temperature is first established for the synthesis of BaTiO₃ nanoparticles. Anodic sparks play a key role, and KOH concentration is one of the most significant factors which affect the appearance of anodic sparks in this method. XRD patterns show that the powder obtained in our study is a pure perovskite phase BaTiO₃ with a cubic structure, whose size and morphology are subsequently studied by TEM. The mean diameter of the particles is 13.8 nm and the standard deviation (S.D.) fitted is 6.26 nm. It is also found that the mean size of the obtained nanoparticles increase from 13.8 nm to 168.0 nm, when 60 vol.% absolute ethanol is replaced by distilled water as the solvent of the electrolyte.     

Field emission of carbon nanotubes grown on nickel substrate

Carbon nanotubes (CNTs) have been synthesized directly on the electrically conducting nickel substrate without additional catalyst. Field emission properties of the as-prepared sample were characterized using parallel plate diode configurations. It was observed that the field emission qualitatively follows the conventional Fowler–Nordheim (F–N) theory from the straight line of ln(I/V²) versus 1/V plot at the high applied field region. The uniformity and stability of the electron emission have also been examined. The low electron turn-on field (E_to) and high emission current density indicates the potential applications of this new CNT-based emitter.     

Synthesis and characterization of single-crystal Sb2S3 nanotubes via an EDTA-assisted hydrothermal route

Single-crystalline Sb₂S₃ nanotubes have been successfully prepared by a simple hydrothermal method. It was found that ethylenediaminetetraacetic acid (EDTA) plays a key role in the formation of Sb₂S₃ nanotubes. Without EDTA, only irregular particles with a size of several micrometers were produced. The morphology and structure of the obtained Sb₂S₃ nanotubes were characterized by XRD, SEM, TEM, and EDS analysis in detail. UV–vis–NIR spectroscopy was further employed to estimate the band gap energy of the obtained products. The measurement of the optical properties revealed that the obtained nanotubes have a band gap of 1.55 eV. The obtained Sb₂S₃ nanotubes may find potential applications in photoelectronic and solar energy because the experimental band gap is close to the optimum value for photovoltaic conversion.