Decorating multiwalled carbon nanotubes with zinc oxide nano-crystallines through hydrothermal growth process

Multiwalled-carbon nanotubes coated with nano-crystalline zinc oxide （ZnO） was prepared by in situ growth of nano zinc oxide on the surfaces of carbon nanotubes through hydrothermal method. X-ray diffraction, transmission electron microscopy and scanning electron microscopy analysis techniques were used to characterize the samples. It was observed that a layer of nano-crystalline ZnO with the wurtzite hexagonal crystal structure was uniformly coated on the nanotube surfaces with good adhesion, which resulted in the formation of a novel ZnO-nanotuhe nano composite. In this work, the carbon nanotubes decorated by metal oxide nanoparticles were synthesized by a simple chemical-solution route which is suitable for the large-scale production with low cost.

Hydrothermal growth of MoS_2/Co_3S_4 composites as efficient Pt-free counter electrodes for dye-sensitized solar cells

MOS2/Co3S4 composite films were prepared via a facile one-step hydrothermal method, and used as efficient and low-cost Pt-free counter electrodes （CEs） for dye-sen- sitized solar cells （DSSCs）. Characterizations revealed that Co3S4 and MoS2 were obtained simultaneously during the facile hydrothermal process. The composites afforded a promising synergistic effect on the catalyzing of triiodide reduction. Enhanced electrocatalytic performance of the resultant composite films was confirmed through cyclic voltammetry （CV） and electrochemical impedance spec- troscopy （EIS） analyses. DSSCs using MoS2/Co3S4 composite CEs outperform the devices with pristine MoS2 or Co3S4 CEs in power conversion efficiency （PCE）. Furthermore, a PCE of 6.77% is obtained for the optimized devices using MoS2/Co3S4 composite CEs measured under standard 1 sun illumination （100 mW cm-2, AM 1.5G）, which is comparable to that of the devices fabricated under the same conditions with conventional thermally deposited Pt CEs （7.14%）. The results demonstrate that MoS2/Co3S4 composites are promis- ing alternatives to Pt to be applied as CEs for DSSCs,

Hydrothermal growth of symmetrical ZnO nanorod arrays on nanosheets for gas sensing applications

The hierarchical ZnO nanostructures with 2-fold symmetrical nanorod arrays on zinc aluminum carbonate （ZnAl-CO3） nanosheets have been successfully synthesized through a two-step hydrothermal process. The primary nanosheets, which serve as the lattice-matched substrate for the self-assembly nanorod arrays at the second-step of the hydrothermal route, have been synthesized by using a template of anodic aluminum oxide （AAO）. The as-prepared samples were characterized by XRD, FESEM, TEM and SAED. The nanorods have a diameter of about 100 nm and a length of about 2μ m. A growth mechanism was proposed according to the experimental results. The gas sensor fabricated from ZnO nanorod arrays showed a high sensitivity to ethanol at 230℃. In addition, the response mechanism of the sensors has also been discussed according to the transient response of the gas sensors.

Effect of Temperature on Anisotropic Crystal Growth of Boehmite under Hydrothermal Condition

Temperature effect （200-400 ℃） on the anisotropic crystal growth of boehmite under hydrothermal conditions with and without octanoic acid was investigated. The crystallinity and the size of particles increased with increasing the treatment temperature. The crystal growth was facilitated greatly above the critical temperature of water. Although several possible factors could affect the crystal growth behavior, the experimental results were discussed in terms of water properties, such as dielectric constant and viscosity The crystallization was enhanced when the viscosity and dielectric constant of water were low. The viscosity reduction at higher temperature may enhance diffusion and crystallization, in particular, without octanoic acid. The enhancement of crystallization at lower dielectric constant implies that the formation of particles, which are less polar than precursor ions, favorably proceeds in such media. The crystal growth along c-axis showed less temperature dependence around the critical temperature in the experiments with octanoic acid, which suggests that the modification reaction on the （001） surface was also facilitated because the modification reaction forms less polar products. This is probably the reason why the aspect ratio （a/c） was considerably higher for the products obtained with the treatments above the critical temperature.

Effect of growth time on morphology and photovoltaic properties of ZnO nanowire array films

Single-crystalline ZnO nanowire arrays with different aspect ratios and nanowire densities were prepared by the hydrothermal growing method using polyethyleneimine （PEI） as a surfactant. PEI can only hinder the lateral growth of the ZnO nanowires, which is observed by high resolution transmission electron microscopy （HRTEM） analysis. Dye-sensitized solar cells were assembled by the ZnO nanowire arrays with different thicknesses, which can be controlled by the growing time and characterized using photocurrent-voltage measurements. Their photocurrent densities and energy allover conversion efficiencies increased with increasing ZnO nanowire lengths. Short-circuit current density of 4.31 mA.cm-2 and allover energy conversion efficiency of 0.87% were achieved with 12.9-μm-long ZnO nanowire arrays.

Hydrothermal Processing,Characterization and Theoretical Calculations of a Copper(Ⅱ) Compound with 1,10-Phenanthroline Derivative Ligand:2-(4-Methoxyphenyl)-1H-imidazo[4,5-f][1,10] Phenanthroline

The metal-organic compound [Cu（MOPIP）2（OH）2] 1（MOPIP = 2-（4-methoxy-phenyl）-1H-imidazo[4,5-f][1,10] phenanthroline） was hydrothermally synthesized and structurally characterized by elemental analysis,Fourier-transformed infrared spectroscopy,thermogravimetric analysis,single-crystal X-ray diffraction and theoretical calculations in Gaussian 03.In the crystal structure,the copper（Cu） atoms are tetra-coordinated with four different nitrogen atoms from two different MOPIP ligands,and the Cu atom is one of the five vertexes of the tetrahedron.Presumably due to the steric bulk of the phenyl ligands,compound 1 adopts a slightly distorted tetrahedral configuration.Moreover,it exhibits a zero-dimensional structure with Cu-MOPIP as the building units.Natural Bond Orbital（NBO） analysis was performed by using the NBO method built in Gaussian 03 Program.The calculation results showed a covalent interaction between the coordinated atoms and Cu（Ⅱ） ion.

Citrate-Mediated Hydrothermal Route to Synthesis A Large-Scale Y_2O_3∶Eu^(3+) Hexangular Prism

Europium-doped yttrium oxide (Y2O3∶Eu3+) hexangular microprisms were synthesized through a citrate-mediated hydrothermal method followed by subsequent calcination. The as-prepared products were characterized by X-Ray Powder Diffractometer (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), and fluorescence spectrometer. The sizes of the Y2O3∶Eu3+ hexangular prisms are about 3 μm in rim and 10 μm in length. The citrate additive was found to be responsible for tailoring the crystal growth dynamically: the concentration of hydroxides in solution is reduced via forming citrate-rare earth ion complexes, giving rise to large crystals with perfect facets; the ratio of growth rate of hydroxides along the c-axis and other crystal facets is suppressed, leading to relatively small aspect ratio. The smooth surface and large size led to the luminescence intensity of hexagonal-prism phosphors higher than that of needle-like bundle products obtained without using trisodium citrate additive.

Hydrothermal Synthesis and Characterization of Nd Doped One-dimensional Hexagonal CePO_4 Nanowires

One-dimensional Nd doped CePO4 hexagonal nanowires have been synthesized for the first time at 140 ℃ for 24 hours via a hydrothermal method using P123 surfactant as the template.The products were characterized by X-ray diffraction,transmission electron microscopy,photoluminescence and high-resolution transmission electron microscopy.Compared with CePO4,one-dimensional nanomaterials we have synthesized,Nd doped CePO4 nanomaterials remain their hexagonal one-dimensional morphology and smooth surface.However,their photoluminescence emissions are greatly enhanced at the wavelength of 348 nm.With their novel fluorescence-emission property,the Nd doped CePO4 nanomaterials are potential in many fields such as optics and electronics.

Synthesis of large FeSe superconductor crystals via ion release/introduction and property characterization

Large superconducting Fe Se crystals of（001） orientation have been prepared via a hydrothermal ion release/introduction route for the first time. The hydrothermally derived Fe Se crystals are up to 10 mm×5 mm×0.3 mm in dimension. The pure tetragonal FeSe phase has been confirmed by x-ray diffraction（XRD） and the composition determined by both inductively coupled plasma atomic emission spectroscopy（ICP-AES） and energy dispersive x-ray spectroscopy（EDX）. The superconducting transition of the Fe Se samples has been characterized by magnetic and transport measurements. The zero-temperature upper critical field H（c2） is calculated to be 13.2–16.7 T from a two-band model. The normal-state cooperative paramagnetism is found to be predominated by strong spin frustrations below the characteristic temperature T（sn）, where the Ising spin nematicity has been discerned in the FeSe superconductor crystals as reported elsewhere.

Advances in advanced solution-synthesis-based structural materials for tactile sensors and their intelligent applications

Intelligent applications,with tactile sensors at their core,represent significant advancement in the field of artificial intelligence.However,achieving perception abilities in tactile sensors that match or exceed human skin remains a formidable challenge.Consequently,the design and implementation of hierarchical structural materials are considered the optimal solution to this challenge.In contrast to conventional methods,such as complicated lithography and three-dimensional printing,the cost-effective and scalable nature of advanced solution-synthesis methods makes them ideal for preparing diverse tactile sensors with hierarchical structural materials.However,the process and applicability of advanced solution synthesis methods have yet to form a seamless system.Accordingly,the development and intellectualization of tactile sensors based on advanced solution synthesis methods are still in their early stages,and require a comprehensive and systematic review to usher in progress.This study delves into the advantages and disadvantages of various advanced solution synthesis methods,providing detailed insights.Furthermore,the positive effects of hierarchical structural materials constructed using these methods in tactile sensors and their intelligent applications are also discussed in depth.Finally,the challenges and future opportunities faced by this emerging field are summarized.

Sensitization of Hydrothermally Grown Single Crystalline TiO2 Nanowire Array with CdSeS Nanocrystals for Photovoltaic Applications

An oriented array of electron transporting nanowires, grown directly on a transparent conductor constitutes an optimal architecture for efficient photovoltaic applications. In addition, semiconductor nanocrystals can work as efficient light absorbers because of their tunable optical properties. In this paper, we use an oriented array of TiO2 nanowires grown directly on a transparent conductive electrode and subsequently sensitized with colloidally grown CdSeS nanocrystal quantum dots （QDs）, using an efficient bi-linker assisted methodology, to demonstrate photovoltaic cells. Upon excitation with light, exciton dissociation takes place at the nanowire-nanocrystal interface, after which, electrons are transported to the fluorine-doped tin oxide （FTO） electrode via single-crystalline TiO2 nanowire channels. We demonstrate that an ex situ ligand exchange of QDs followed by sensitization on oxygen-plasma treated TiO2 nanowires results in enhanced loading of QDs, as compared to the in situ ligand exchange approach. An array of 1μm long TiO2 nanowire sensitized with CdSeS nanocrystals exhibits photovoltaic effects with a short-circuit current of 2-3 mA/cm2, an open circuit voltage of 0.6-0.7 V and a fill factor of 52-5%, resulting in devices with efficiencies of up to 0.6%.

Hydrothermal synthesis of lanthanide(hydr)oxide micro/nanorods in presence of tetrabutylammonium hydroxide

Uniform and well-defined lanthanide hydroxide and oxide micro/nanorods Ln（OH）_3（Ln=La, Pr, Sm, Eu, Gd, Er） and Gd（OH）_3：Eu^（3＋）, Gd_2O_3：Eu^（3＋） were successfully synthesized through a green and facile hydrothermal method. Tetrabutylammonium hydroxide（TBAH） and lanthanide nitrides were used as the hydrothermal precursors without the addition of any templates/surfactants. The products were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM） and photoluminescence（PL） spectra. The result demonstrated that lanthanide hydroxide micro/nanorods with 20–80 nm in diameter and 50–450 in length were obtained. The size of the Ln（OH）_3（Ln=La, Pr, Sm, Eu, Gd, Er） rods increased with the increase of the atomic number. The size of the Gd（OH）_3：Eu^（3＋） rods decreased with the increase of p H value by modulating the amount of the TBAH solution. The as-formed product via the hydrothermal process, Gd（OH）_3：Eu^（3＋）, could be transformed to Gd_2O_3：Eu^（3＋） with the same morphology and a slight shrinking in size after a post annealing process. It is a facial method to synthesize photoluminescent nanomaterial of Gd_2O_3：Eu^（3＋）. The Gd_2O_3：Eu^（3＋） microrods exhibited strong red emission corresponding to ~5D）0→~7F_2 transition（610 nm） of Eu^（3＋） under UV light excitation（257 nm）.

Template-free approach for hydrothermal fabrication of ZnO microspheres

Wurtzite ZnO microspheres, 5.5-11 μm in diameter and with smooth surfaces, were prepared in absolute ethanol via a simple template-free method in the presence of ethylenediamine. The products were characterized using X-ray powder diffraction, scanning electron microscopy and transmission electron microscopy. This simple method to fabricate ZnO microspheres shows high yield （〉90%） and good reproducibiliry. The formation process of ZnO microspheres was discussed. The as-obtained ZnO microspheres are expected to provide some immediate advantages for optical, microelectronic, and biological applications.

Influence of temperature and solution composition on the formation of calcium sulfates

Calcium sulfates （anhydrite and hydrates） were synthesized by mixing CaCl2 and Na2SO4 solutions at room temperature followed by aging the resulting slurries at elevated temperatures. The variation of the morphology and structure of the calcium sulfates with aging temperature was investigated. Experimental results indicated that CaSO4.2H20 plates, CaSO4.0.5H2O whiskers and CaSO4 spindles were formed at 〈100℃, 130-160℃ and 〉170℃, respectively. The formation and conversion of the calcium sulfates were discussed on the basis of characterization of the products and chemical analysis of the solutions. Compared to NaCl solution, pure water favors one-dimensional hydrothermal growth of CaSO4.0.BH2O whiskers owing to lower supersaturation.

Microwave-assisted solvothermal synthesis of ZSM-22 zeolite with controllable crystal lengths

ZSM-22 （TON） zeolite crystal morphology was successfully controlled using a microwave-assisted solvothermal fabrication method. Different co-solvents, including ethanol, 2-propanol, glycerol, and ethylene glycol, were also applied in the synthesis mixture. The effects of various parameters such as the aging time, the type and amount of co-solvent on the ZSM-22 crystal aspect ratio were investigated. When employing this microwave irradiation synthesis, a long aging time was crucial to obtain smaller and more uniform crystal sizes. The addition of co-solvent resulted in elongated ZSM-22 crystals, regard- less of the actual co-solvent used, although ZSM-22 zeolite crystallinity was sensitive to the co-solvent type. In general, the use of a co-solvent stimulated the appearance of ZSM-5 zeolite as an impurity and the amount of this impurity was proportional to the concentration of co-solvent in the synthesis mixture.