Microwave-assisted synthesis of praseodymium hydroxide nanorods and thermal conversion to oxide nanorod

Pr(OH)₃ nanorods with uniform diameter of 12 nm and different lengths ranging from 50 to 220 nm were successfully prepared via a facile and rapid microwave-assisted hydrothermal method. Pr₆O₁₁ nanorods were also obtained from calcination of the as-prepared hydroxide nanorods as precursors at 500 °C for 6 h. The results showed that the Pr(OH)₃ with hexagonal phase and Pr₆O₁₁ nanorods with cubic phase have high crystallinity and purity. The mechanism for the microwave-assisted hydrothermal synthesis of Pr(OH)₃ nanorods was preliminarily presented.     

Controlled synthesis of mesoporous α-Fe2O3 nanorods and visible light photocatalytic property

Porous α-Fe₂O₃ nanorods with typical pore size of 2–4 nm were controlled prepared by a facile hydrothermal process of Fe(NO₃)₃·9H₂O aqueous solution in the presence of NaOH, followed by a calcination treatment. Contrast experiments indicate that the morphology and crystalline structure of the hydrothermal products depend greatly on the quantity of NaOH. Hematite nanoparticles and microplates were respectively obtained under conditions without or with excess NaOH. The porous α-Fe₂O₃ nanorods exhibit a high BET surface area of 105.1 m² g^?1 and a pore volume of 0.13 m³ g^?1. UV–vis measurement shows wide absorption to visible light and an obvious blue-shift of the adsorption edge due to the quantum size effect. The visible-light photocatalytic performances of the as-prepared samples were evaluated by photocatalytic decolorization of methylene blue at ambient temperature. The results indicate that the photocatalytic activity of the porous α-Fe₂O₃ nanorods is superior to hematite nanoparticles and platelets and exhibit good reusable feature. The photocatalytic process of porous structure is determined to be pseudo-first-order reaction with apparent reaction rate constant of 1.04 × 10^?2 min^?1. And the optimum photocatalyst dosage is 20 mg per 100 mL of dye solution. The porous α-Fe₂O₃ nanorods are considered potential photocatalyst for practical application due to the excellent photocatalytic behavior and good reusability.     

Facile and large-scale synthesis of single-crystalline manganese oxyhydroxide/oxide nanostructures

On basis of the redox reaction between MnO₄⁻ and Mn²⁺, a facile hydrothermal method combined with the adjustment of pH value in the reaction system has been employed to synthesize single-crystal γ-MnOOH nanorods, and square-like Mn₃O₄ nanoparticles. Additionally, single-crystalline β-MnO₂ and Mn₂O₃ nanorods can be obtained after subsequent calcinations of the as-prepared γ-MnOOH nanostructures at 300 °C and 600 °C, respectively. Furthermore, electrochemical property of as-obtained β-MnO₂ is also studied.     

Synthesis of single-crystalline perovskite barium titanate nanorods by a combined route based on sol-gel and surfactant-templated methods

The single-crystalline perovskite barium titanate nanorods were successfully synthesized by a combined route based on sol-gel and surfactant-templated methods at low temperature. The synthesis was accomplished by using barium acetate (Ba(CH₃COO)₂) and tetrabutyl titanate (Ti[O(CH₂)₃CH₃]₄) as the starting materials and laurylamine as the surfactant, respectively. Well-isolated single-crystalline cubic perovskite BaTiO₃ nanorods with diameters ranging from 20 to 80 nm and lengths reaching up to > 10 μm can be easily fabricated by this route. The crystal form and morphology of the nanorods were characterized by X-ray diffraction, TEM and HRTEM. The mechanism of the formation of the single-crystalline cubic perovskite BaTiO₃ nanorods was discussed based on the theory of oriented attachment.     

An efficient chemical precipitation route to fabricate 3D flower-like CuO and 2D leaf-like CuO for degradation of methylene blue

A facile and eco-friendly way for fabrication of CuO is developed based on an one-step chemical precipitation route without calcination procedure or use of surfactant. The structure features of as-prepared CuO are characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and N₂ adsorption-desorption experiment. X-ray diffraction analysis shows that CuO with particle size of 13.5–19.2 nm and crystallinity of 67.0–72.9% can be fabricated by the transformation of Cu(OH)₂ precursor at bath temperature above 50 °C. By adjusting the oil bath temperature and the content of ammonium hydroxide, we demonstrate a formation mechanism to control CuO to be 2D leaf-like structure with large specific surface area of 33.4 m²/g and pore volume of 0.226 cm³/g, or 3D flower-like ones with specific surface area of 7.45–18.7 m²/g and pore volume of 0.0249–0.0850 cm³/g. The catalytic performances of as-prepared CuO are evaluated by monitoring degradation of methylene blue in the presence of hydrogen peroxide. Almost 100% methylene blue degradation rate can be reached after reaction for 210 min on 3D flower-like CuO synthesized with 10 mL ammonia content in oil bath of 50 °C. The high activity can be correlated with the morphology and pore volume of CuO. The present synthetic strategy is an inexpensive and convenient way suitable for large-scale fabrication of copper oxides, which are potential catalysts for organic compounds degradation.     

Synthesis of α-Sb2O4 nanorods by a facile hydrothermal route

α-Sb₂O₄ nanorods with diameter of 50–150 nm and length of 100–300 nm have been successfully synthesized by a hydrothermal method using SbCl₃ and I₂ as reaction reagents. The obtained sample is characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, and selected-area electron diffraction. The results confirm that the product is pure single-crystalline α-Sb₂O₄ nanorods with few dislocations and defects. The vibrational property of the nanorods is investigated by Raman spectroscopy. Raman spectrum of α-Sb₂O₄ nanorods has a small red shifts compared with that of the bulk α-Sb₂O₄ powders. A possible growth mechanism of α-Sb₂O₄ nanorods is proposed as three stages: the hydrolyzation of SbCl₃ under strong acid condition, the oxidation of Sb₄O₅Cl₂ and the growth of α-Sb₂O₄ nanorods with the aid of iodine transport.     

Porous network of Y2O3 nanorods prepared by electrogeneration of base in chloride medium

A porous network of Y₂O₃ nanorods was successfully prepared by an easy two-step and template-free process. Firstly, Y(OH)₃ was galvanostatically grown on steel cathode by electrogeneration of base in chloride medium. Then it was thermally converted to oxide via heat treatment. Phase transformations during the heat treatment of deposit were proposed. Morphological studies showed that the obtained oxide has a porous network, composed of intercrossed nanorods. The nanorods are 200–300 nm in length and 50–70 nm in diameter. The mechanism of base electrogeneration in chloride medium, the deposition of Y(OH)₃ nanorods on the cathode surface and their thermal conversion to Y₂O₃ have been discussed.     

Facile fabrication of La(OH)3 nanorod arrays and their application in wastewater treatment

Hexagonal and vertically aligned La(OH)₃ nanorod arrays have been fabricated in a large scale via a simple electrochemical method without any hard templates and surfactants. By the aid of potential-time curve, a possible formation process of the La(OH)₃ nanorod arrays is proposed, and the gas bubbles functioning as a dynamic template might be responsible for the growth of ordered La(OH)₃ nanorods. The total absorption capacities of the as-prepared products for Congo red is about 73.5 mg g^− 1, which shows an environmental engineering application in removing organic dye from water. In short, this synthetic method shows prominent advantages such as its low-cost, easy preparation, good adherence and suitability for preparing other nanoarrays.     

Transformation of microporous titanium glycolate nanorods into mesoporous anatase titania nanorods by hot water treatment

High surface area titanium glycolate microporous multi-faceted nanorods were synthesized from the reaction of titanium alkoxides (Ti(OEt)₄, Ti(O ⁱ Pr)₄, or Ti(O ⁿ Bu)₄) with ethylene glycol, using a sol–gel reflux method. The specific surface area of the as-synthesized titanium glycolate nanorods obtained from Ti(OEt)₄ is ~480 m²/g. A hot water treatment at 90 °C for 1 h transformed the titanium glycolate microporous nanorods into mesoporous anatase TiO₂ nanorods. The shape of the nanorods was conserved after hot water treatment and the microporous to mesoporous transformation took place without significant change in the surface area (477 m²/g). Micro Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, solid state NMR, and nitrogen adsorption/desorption were used to characterize the samples. As a demonstration of potential applications, the thus formed mesoporous anatase TiO₂ nanorods were tested for their photocatalytic efficiency in the degradation of crystal violet, and a photodegradation mechanism is proposed.     

Sonochemical synthesis,characterization, and electrochemical properties of MnMoO4 nanorods for supercapacitor applications

In this article, we reported the preparation of manganese molybdate (MnMoO₄) nanorods by a facile sonochemical method and investigated its electrochemical properties for supercapacitor applications. The microstructure, surface morphology and composition were characterized by using field emission scanning electron microscope (FE-SEM), high resolution-transmission electron microscopy (HR-TEM), X-ray diffraction analysis (XRD), Raman spectroscopy and X-ray photo electron microscopy (XPS). The cyclic voltammetry (CV) curves of sonochemically synthesized α-MnMoO₄ nanorods revealed the presence of redox pairs suggesting the pseudocapacitive nature of MnMoO₄. A maximum specific capacitance of the α-MnMoO₄ nanorods was about 168.32 F g⁻¹ as observed from the galvanostatic charge–discharge (GCD) analysis at a constant current density of 0.5 mA cm⁻². Long term cyclic stability study revealed that about 96% of initial capacitance was retained after 2000 cycles.     

3D Co-Doping α-Ni(OH)2 Nanosheets for Ultrastable,High-Rate Ni-Zn Battery

The α-Ni(OH)₂ is regarded as one promising cathode for aqueous nickel-zinc batteries due to its high theoretical capacity of ≈480 mAh g⁻¹, its practical deployment however suffers from the poor stability in strong alkaline solution, intrinsic low electrical conductivity as well as the retarded ionic diffusion. Herein, a 3D (three dimensional) macroporous α-Ni(OH)₂ nanosheets with Co doping is designed through a facile and easily scalable electroless plating combined with electrodeposition strategy. The unique micrometer-sized 3D pores come from Ni substrate and rich voids between Co-doping α-Ni(OH)₂ nanosheets can synergistically afford facile, interconnected ionic diffusion channels, sufficient free space for accommodating its volume changes during cycling; meanwhile, the Co-doping can stabilize the structural robustness of the α-Ni(OH)₂ in the alkaline electrolyte during cycling. Thus, the 3D α-Ni(OH)₂ shows a high capacity of 284 mAh g⁻¹ at 0.5 mA cm⁻² with an excellent retention of 78% even at 15 mA cm⁻², and more than 2000 stable cycles at 6 mA cm⁻², as well as the robust cycling upon various flexible batteries. This work provides a simple and efficient pathway to enhance the electrochemical performance of Ni-Zn batteries through improving ionic transport kinetics and stabilizing crystal structure of cathodes.     

2D SnO2 nanorod networks templated by garlic skins for lithium ion batteries

SnO₂ nanorods with 2D network structure prepared via an effective method of using the skins of garlic bulbs as templates are examined as anode materials for Li-ion battery. The samples are composed of SnO₂ nanorods with length of ca. 80 nm and possess high BET surface area of 163.25 m² g⁻¹. The synthesized SnO₂ electrode shows a high specific capacity (ca. 620 mAh g⁻¹), an excellent cycling stability and a good rate capability but low initial coulombic efficiency. The nanorods characteristics of SnO₂ ensure the fast Li-ion diffusion in the electrode. The loose network structure provides the electrode with a sufficient void space, which sufficiently alleviates the mechanical stress caused by volume change, and thus avoids the electrode to pulverize in the charge–discharge process. Therefore, the obtained SnO₂ electrode shows a good cyclic stability and a high rate performance.     

Hydrothermal synthesis and magnetic properties of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles and nanorods

NiFe₂O₄ nanoparticles and nanorods were synthesized by a facile hydrothermal treatment of Ni(DS)₂ (Nickel dodecyl sulfate), FeCl₃, and NaOH aqueous solution at 120 °C. The products were characterized by powder X-ray diffraction, transmission electron microscopy, and selected area electron diffraction. The magnetic properties were evaluated using a vibrating sample magnetometer. The probable mechanism of the formation of NiFe₂O₄ nanoparticles and nanorods was discussed.     

The morphology of limestone-based pellets prepared with kaolin-based binders

Modifications and pelletization of limestone were investigated in order to improve the utilization of CaO-based materials for different catalytic reactions and environmental applications. Attempts to purify the limestone by ion-exchange with CaCl₂ solution did not result in significant removal of impurities. On the other hand, acetification with 10 vol.% acetic acid enhanced pore surface area and pore volume of the sorbent by 42% and 3-fold, respectively. The acetification was found to widen small pores, and thus create a beneficial pore size distribution with more pores in the range of 25–100 nm. In order to utilize such powdered materials in fluidized beds, pelletization is the next step. Unfortunately, pelletization results suggested that natural kaolin is an unsuitable binder for preparing CaO-based pellets due to its negative impact on pellet morphology. By contrast, Al(OH)₃ binder obtained from kaolin leaching had a strong positive effect on the porous texture of the pellets, demonstrated by pore surface area and volume of 22.48 m² g⁻¹ and 0.051 cm³ g⁻¹ for 1 mm pellets with CaO/binder ratio of 5.5, compared to 10.92 m² g⁻¹ and 0.039 cm³ g⁻¹ for natural materials. The enhancement in pellet morphology is mainly attributed to transformation of Al(OH)₃ to the highly porous Al₂O₃ at high temperatures. Pellets synthesized from limestone modified with 10 vol.% acetic acid with Al(OH)₃ binder (ratio of 5.5) exhibited high pore surface area and volume, represented by 1.3-fold and 44% increase over those for natural limestone. It was concluded that the combination of acetified limestone with Al(OH)₃ binder is a promising approach for synthesis of CaO-based pellets with enhanced morphology.     

Synthesis of hydroxyapatite nanotubes for biomedical applications

Single phase, stoichiometrically pure, hollow nanotubes of hydroxyapatite have been synthesized and single-particle analysis has been performed to successfully prove the sole formation of Ca₁₀(PO₄)₆(OH)₂ phase. The facile synthesis involves a sol–gel process under neutral conditions in the presence of a sacrifical anodic alumina template. The structures formed are hollow nanotubes that have been characterized by XRD, SEM, TEM, SAED, EELS, EDS and BET measurements. The diameter of the resulting tubes is in the range of 140–350 nm, length is on the order of a few microns and the wall thickness of the tubes was found to be ca. 30 nm. Moreover these tubes had a large BET surface area of 115 m²/g and were found to be biocompatible. They displayed inertness in the presence of NIH 3T3 mouse fibroblast cells as dictated by an MTT assay.     

Microwave-assisted synthesis and characterization of LaPO4:Re (Re = Ce3+, Eu3+, Tb3+) nanorods

LaPO₄:Re (Re = Ce³⁺, Eu³⁺ and Tb³⁺) nanorods have been successfully synthesized on a large scale by a facile and rapid microwave heating method. The structure, morphology and physical properties of the as-prepared products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). XRD patterns showed that the as-prepared products had hexagonal structure and high crystallinity and purity. TEM images showed that these LaPO₄:Re nanorods have a high yield and an obvious one-dimensional structure with diameter from 6 nm to 30 nm and length up to 400 nm. The luminescence spectra of the products indicated that different rare-earth ions had been successfully doped in LaPO₄ matrix via the microwave heating method and the actual doping amounts of Re ions were determined by the inductively coupled plasma (ICP).     

Synthesis of mesoporous Al2O3 macrospheres using the biopolymer chitosan as a template: A novel active catalyst system for CO2 reforming of methane

A new and simple method to prepare alumina containing mainly mesopores is described. This alumina has a high surface area (464 m²/g) and a large pore volume ranging from about 0.35 to 0.65 cm³/g. The present method was developed using a biopolymer (chitosan) and Al solution. The Al–chitosan solution was added to NH₄OH solution in the form of drops. A hybrid macrosphere compound of aluminum hydroxide and organic polymer is formed. Through polymer elimination by thermal treatment, porous Al₂O₃ spheres with a high specific surface area are obtained. The Ni-impregnated Al₂O₃ spheres showed a high catalytic activity and stability for dry reforming of methane at 650 °C and a CH₄ / CO₂ = 1 molar ratio.     

A facile approach to synthesize silver nanorods capped with sodium tripolyphosphate

Silver nanorods have been successfully synthesized via a facile route using sodium tripolyphosphate (Na₅P₃O₁₀) as the capping agent. Silver nitrate and glucose served as the Ag⁺ source and green reducing agent in aqueous solution, respectively. The products were characterized by X-ray powder diffraction (XRD), UV–visible spectroscopy (UV–vis), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The results showed that the obtained silver nanorods are highly crystallized with an average diameter of 30 nm and lengths up to 400 nm. The linear structure of the capping agent and slow reaction rate are considered to be key factors in the control of particle morphology. The possible formation mechanism has been discussed based on the experimental results.     

Synthesis of hexagonal β-Co(OH)2 nano-platelets with high catalytic activity via a low-temperature precipitation method

Large-scale β-Co(OH)₂ hexagonal nano-platelets have been synthesized successfully at 70 °C using only CoCl₂ and NaOH as reactants. The physicochemical features of the β-Co(OH)₂ hexagonal nano-platelets were characterized by X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and nitrogen absorption–desorption. Results showed that the β-Co(OH)₂ obtained consisted of thin, regular, hexagonal nano-platelets with diameters and thicknesses of 50–300 nm and 30–80 nm, respectively. A transformation from β-Co(OH)₂ to Co₃O₄ was observed in the temperature range 160–220 °C. The average pore-size and the Brunauer–Emmet–Teller (BET) surface area of the synthesized β-Co(OH)₂ were 16.76 nm and 29.45 m²/g. The prepared product had a significant effect on the catalytic decomposition of ozone.     

Synthesis of barium strontium titanate nanorods in reverse microemulsion

Perovskite Ba_0.7Sr_0.3TiO₃ nanorods were synthesized in Triton X-100 reverse microemulsion at room temperature and characterized by XRD, ICP-AES, ED and TEM. The Ba_0.7Sr_0.3TiO₃ nanorods with a diameter of 60-100 nm and a length of 450-1200 nm showed a single-crystalline tetragonal structure. The size of nanorods was effectively tuned by changing w value (molar ratio of water to surfactant), aging time and reactant concentration.