Facile synthesis of rice shaped CuO nanostructures for battery application

The oxides of transition metals are an important class of semiconductors, which have applications in electronics, magnetic storage media, solar applications and catalysis. Among them, CuO has attracted much attention due to its widespread applications. In this paper, a facile synthesis of rice shaped CuO nanostructures have been prepared by reflux method for battery application using Copper nitrate and ammonia as precursors. Samples were prepared at three different reaction timings namely 6, 12 and 24 h. The as-prepared samples were calcinated at 400 °C to ensure the formation of copper oxide. The final products were subjected to X-ray diffraction, scanning electron microscopy, FT-IR and UV–Vis spectroscopy in order to study the effect of reaction time on the properties of the prepared copper oxide nanostructures. It is found that at controlled reaction time rice shaped CuO nanostructures are obtained. Cyclic voltammogram was recorded to understand the electrocatalytic behaviors of the rice shaped CuO sample prepared under optimized condition.     

Low dimensional silver nanostructures: synthesis, growth mechanism, properties and applications

This work presents a review of the recent advances on the low-dimensional (LD) silver nanostructures (e.g., one-dimensional nanorods and nanowires, and two-dimensional nanoplates and nanodisks). First, the methods, either physical or chemical, for the synthesis of silver LD nanostructures are introduced. Then, the use is discussed of advanced experimental techniques (e.g., transmission electron microscope, high-resolution transmission electron microscope, scanning electron microscope, atomic force microscope, ultraviolet-visible and Raman spectra) and theoretical techniques at different time and length scales from quantum mechanics (e.g., ab initio simulation and density function theory) to molecular dynamics method for understanding the principles of governing particle growth, as well as discrete dipolar approximate method for understanding the optical properties of different shapes and sizes of silver LD nanostructures. Subsequently, the functional applications of the LD silver nanostructures in different areas such optical, electronic, and sensing, particularly for those related to surface plasma resonance are summarized based on the recent findings. Finally, some perspectives and comments for future investigation of silver nanostructures are also briefly discussed.     

Synthesis and growth mechanism of CuO nanostructures and their gas sensing properties

CuO nano-particles, nano-rods, nano-sheets and nano-flowers were synthesized by the hydrothermal routes with copper salts under different additions. The obtained samples were characterized by X-ray diffraction and scanning electron microscopy. We investigated the effects of precursors on the formation of CuO with different morphologies and proposed their possible formation mechanisms. In addition, the obtained CuO nano-flowers are found to show better sensing performances than the other three low-dimensional CuO nanostructures. Our results also demonstrate that gas sensing properties of nanocrystals can be significantly improved by tailoring shape and morphology of the nanocrystals. The CuO nano-flowers may hold substantial promise in low-dimensional gas-sensing applications.     

Beta-MnO2 3D nanostructures: mineralizer-assisted synthesis, characterization, and growth mechanism

The beta-MnO2 three-dimensional (3D) nanostructures were synthesized in large area by a mineralizer-assisted hydrothermal route. KNO3 was introduced as inorganic mineralizer to direct the growth of beta-MnO2 3D nanostructures from Mn(NO3)2 solutions. The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). Possible growth mechanism of beta-MnO2 3D nanostructures was proposed based on comparative experiments, indicating that KNO3 mineralizer and the concentration of Mn(NO3)2 solution were the two decisive factors in the fabrication of beta-MnO2 3D nanostructures.     

HEPES-mediated controllable synthesis of hierarchical CuO nanostructures and their analogous photo-Fenton and antibacterial performance

Owing to the strongly morphology and size-dependent properties of nanomaterials, developing a simple and eco-friendly approach for controlling synthesis and assembly of hierarchical CuO nanostructures plays a critical role. In this work, we successfully developed an eco-friendly and facile hydrothermal route for controllable synthesis of various morphologies CuO nanostructures, where traditional and toxic additives were replaced by biocompatible 4-(2-hydroxyethyl)-1-piperazineethane-sulfonic acid (HEPES). The growth rate and orientation of CuO nanoparticles were tuned through adjusting the concentration and pH value of HEPES. The XRD pattern, SEM, UV-DRS, and BET indicated CuO nanostructures maintained high purity and excellent crystalline nature and showed more regular morphology and size with enhanced visible light absorption. The analogous photo-Fenton assay demonstrated that the as-prepared CuO nanostructures present enhanced dye removal capability when compared with CuO synthesized in pure water. Furthermore, the antibacterial assay on S. aureus was also investigated, and CuO nanoparticles with smallest size displayed the best antibacterial performance. These results reveal that HEPES shows a remarkable influence on the possible application of as-prepared CuO nanostructures which having great potential in pollutant removal.     

Controlled synthesis of CuO nanostructures on Cu foil, rod and grid

CuO nanowires are synthesized by heating Cu foil, rod and grid in ambient without employing a catalyst or gas flow at temperatures ranging from 400 to 800 °C for a duration of 1-12 h. Scanning electron microscopy (SEM) investigation reveals the formation of nanowires. The structure, morphology and phase of the as-synthesized nanowires are analyzed by various techniques such as X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). It is found that these nanowires are composed of CuO phase and the underlying film is of Cu₂O. A systematic study is carried out to find the possibilities for the transformation of one phase to another completely. A possible growth mechanism for the nanowires is also discussed.     

One dimensional aluminum nitride nanostructures: synthesis, structural, and luminescence properties

Aluminum nitride (AIN) is a direct bandgap semiconductor with a bandgap about 6.1 eV at room temperature, the largest among semiconductors. This paper emphasizes experimental results of the growth and optical properties of AIN nanostructures by direct nitridation. The nitridation process was performed by chemical vapor deposition method with nitrogen (N2) gas flow. AIN nanostructures were analyzed by scanning electron microscope (SEM) equipped with energy-dispersive X-ray (EDX) spectroscope and photoluminescence (PL) spectroscopy. AIN nanowires with different widths from ultrathin to thick were synthesized with this method. All of the samples had high purity without presence of any other material in EDX spectrum. The PL spectra were obtained by a 325-nm helium-cadmium (He-Cd) laser as the excitation source showing high-intensity light emitting visible wavelengths for these structures at room temperature.     

Microwave-assisted synthesis and characterization of flower shaped zinc oxide nanostructures

A microwave-assisted solution-phase approach has been applied for the synthesis of zinc oxide nanostructures. The synthesis procedure was carried out by using two reagents: hydrazine hydrate and ammonia. Flower shaped particles were obtained with hydrazine hydrate whereas mainly spherical agglomerated particles were observed with ammonia. The nanostructures were influenced by microwave irradiation time, reagent concentration and molar ratio of the precursors. High crystalline materials were found without the need of a post-synthesis treatment. The average crystalline size of ZnO nanostructures has been analyzed by X-ray Diffraction (XRD) pattern and estimated to be 18 nm. The presence of flower shaped zinc oxide with nanorods arranged has been confirmed from Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) micrographs. The samples were further analyzed by Fourier Transform InfraRed (FT-IR), Thermogravimetric Analysis (TGA) and photoluminescence spectroscopic techniques.     

Green and facile synthesis of hierarchical cocoon shaped CuO hollow architectures

Hierarchical cocoon shaped CuO hollow nanostructures have been synthesized on a large scale by a facile green microwave-assisted aqueous process at reflux in the absence of templates and additives. The as-prepared products were investigated by FESEM, TEM, HRTEM, XRD and UV-vis absorption optical properties. The results reveal that cocoon shaped structures, that is ellipsoids, possess a monoclinc phase CuO with the long and short diameters of about 300 nm and 150-200 nm, respectively. The walls of hollow cocoons with around 50 nm in thickness are self-assembled by nanorods with diameters of 6-8 nm. A possible mechanism for the hollow CuO structures was proposed, in which CO₂ bubbles act as soft-template to aggregate the primary monomers. The band gap energies were estimated to be 2.03 eV, which showed the quantum size effect of the nanosized semiconductors.     

Cu and CuO nanostructures: facile hydrothermal synthesis,characterization and photocatalytic activity using new starting reagents

The present investigation reports a simple hydrothermal process for synthesizing Cu and CuO nanostructures using new set of low-cost starting reagents including CuSO₄·5H₂O, ethylenediamine and hydrazine hydrate. The obtained nanostructures were characterized by techniques such as XRD, SEM, EDX, DRS and FTIR. Effect of hydrazine hydrate, ethylenediamine, reaction temperature and time on morphology of prepared nanostructures was well studied. Our results showed ethylenediamine and hydrazine hydrate play crucial role on particle growth, formation mechanism of nanostructures and consequently on morphology of nanostructures. Furthermore, the efficiency of CuO nanostructures as a photocatalyst for the decolorization of methylene blue using ultraviolet light irradiation was evaluated and the CuO nanoparticles compared to nanorods showed more efficient photocatalytic activity.     

Three-dimensional CuO nanobundles consisted of nanorods: hydrothermal synthesis, characterization, and formation mechanism

Novel monoclinic CuO nanobundles, 0.8-1 microm in size, were synthesized at 130 degrees C in the presence of sodium dodecyl benzenesulfonate (SDBS) by a simple hydrothermal method. Each nanobundle was comprised of many nanorods with one ends growing together to form a center and another ends radiating laterally from this center. The length and the diameter of these assembled nanorods are in the range of 200-300 nm and about 20-30 nm, respectively. HRTEM and SAED results indicated that the CuO nanorods grow along the [010] direction. An investigation of the hydrothermal process revealed that the reaction time, temperature and surfactant play important roles in the formation of the resultant CuO nanostructures. Isolated CuO nanorods were obtained when the temperature was increased to 190 degrees C, and CuO microflowers composed of many nanosheets were produced at 130 degrees C when cetyltrimethylammonium bromide (CTAB) was employed instead of SDBS. The possible mechanism for the formation of these CuO nanostructures was discussed simply on the basis of the experimental results.     

Morphology evolution, growth mechanism and optical properties of AlN nanostructures

In the present paper, we prepared various kinds of aluminium nitride (AlN) nanostructures utilizing chemical vapor deposition method at atmospheric pressure. Different nanostructures including flower, rod and film were obtained on bare silicon substrates by controlling the growth temperature between 650 and 800 °C. The formation mechanism of these nanostructures is related to vapor–solid process and Ehrlich–Schwoebel barrier. The crystalline phase and morphologies of the as-prepared AlN samples are investigated systematically. Their microstructures are observed by the scanning electron microscope. The X-ray diffraction results demonstrate that the AlN samples exhibit pure phase and grow preferentially along the c-axis. The Raman examination shows there is a strong stress at the interface between the AlN nanostructures and the silicon substrate. The photoluminescence properties indicate that AlN nanostructures possess a broad luminescence band, which can be divided into two subbands by Gaussian fitting, and they are ascribed to nitrogen vacancy as well as the oxygen impurity.     

磺基水杨酸钠辅助下CuO纳米结构的维度可控合成与表征

以磺基水杨酸钠(SS)作为形貌调控剂,采用水热方法可控合成了各种不同形貌和维度的CuO纳米材料。结果表明,通过简单调节SS/CuCl2的摩尔比,分别合成了CuO纳米棒,纳米枝晶和海胆状球形分级结构。如果体系中不引入SS,产品则是CuO纳米片。紫外-可见光谱显示了各种CuO纳米结构与尺寸和形貌相关的吸收现象,为了探索CuO各种形貌的影响因素,我们进行了系统的实验观察。     

氧化镁新奇纳米结构的合成与生长机理研究

金属镁粉作为原材料,硅片作为衬底,在水蒸气和一定条件下,利用化学气相沉积法合成了大量规则分布在硅衬底上新奇的氧化镁纳米花结构.该纳米花由多根纳米纤维组成,其中纳米纤维的直径大约一致为80nm,长度达到几微米.我们通过一系列实验,在固定其它条件下通过调节加热时间,系统地观察了氧化镁纳米花结构的生长过程.由于在整个反应过程中,没有金属催化剂的参与,加上氧化镁纳米花结构的形貌,我们可以用液-固(VS)生长机制来解释氧化镁纳米花结构的形成.这种新奇的纳米结构对于进一步深入研究氧化镁纳米结构的合成与生长机理具有重要的参考价值.     

One step synthesis of Bi@Bi2O3@carboxylate-rich carbon spheres with enhanced photocatalytic performance

Bi@Bi₂O₃@carboxylate-rich carbon core-shell nanosturctures (Bi@Bi₂O₃@CRCSs) have been synthesized via a one-step method. The core–shell nanosturctures of the as-prepared samples were confirmed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and Raman spectroscopy. The formation of Bi@Bi₂O₃@CRCSs core–shell nanosturctures should attribute to the synergetic roles of different functional groups of sodium gluconate. Bi@Bi₂O₃@CRCSs exhibits significant enhanced photocatalytic activity under visible light irradiation (λ > 420 nm) and shows an O₂-dependent feature. According to trapping experiments of radicals and holes, hydroxyl radicals were not the main active oxidative species in the photocatalytic degradation of MB, but O₂⁻ are the main active oxidative species.     

Hydrothermal synthesis of different TiO2 nanostructures: structure, growth and gas sensor properties

A type of titanium precursor, H-exchanged titanate nanobelts, was used to prepare nanosized anatase titanium dioxide (TiO₂) with various morphologies by hydrothermal method. Nanorods, nanobelts, nano-polyhedrons and nanoparticles were successfully synthesized. We found that CTAB and EDTA-4Na⁺ play critical roles in synthesizing the nanorods and nano-polyhedrons. All the samples exhibit rapid response and recovery time to ethanol, but Nanorods, nanobelts and nano-polyhedrons show lager response than nanoparticles.     

Sonochemical synthesis of CuO nanostructures and their morphology dependent optical and visible light driven photocatalytic properties

A controlled synthesis of CuO nanostructures with various morphologies were successfully achieved by presence/absence of low frequency (42 kHz) ultrasound with two different methods. The size, shape and morphology of the CuO nanostructures were tailored by altering the ultrasound, mode of addition and solvent medium. The crystalline structure and molecular vibrational modes of the prepared nanostructures were analysed through X-ray diffraction and FTIR measurement, respectively which confirmed that the nanostructures were phase pure high-quality CuO with monoclinic crystal structure. The morphological evaluation and elemental composition analysis were done using TEM and EDS attached with SEM, respectively. Furthermore, we demonstrated that the prepared CuO nanostructures could be served as an effective photocatalyst towards the degradation of methyl orange (MO) under visible light irradiation. Among the various nanostructures, the spherical shape CuO nanostructures were found to have the better catalytic activities towards MO dye degradation. The catalytic degradation performance of MO in the presence of CuO nanostructures showed the following order: spherical < nanorod < layered oval < nanoleaf < triangular < shuttles structures. The influence of loading and reusability of catalyst revealed that the efficiency of visible light assisted degradation of MO was effectively enhanced and more than 95 % of degradation was achieved after 3 cycles.