Controlled synthesis of light rare-earth hydroxide nanorods via a simple solution route

Ln(OH)₃ (Ln=La, Pr, Nd, Sm, Eu, Gd) nanorods are synthesized without using any surfactants or templates at room temperature. The as-obtained nanorods are within 4–25 nm in diameter and up to 200 nm in length. The most important improvement is that the aspect ratio of the obtained nanorods can be effectively controlled by adjusting the reaction time and pH value of the reaction system. The as-synthesized nanorods are characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It is interesting to find that both the inherent crystal structure of light lanthanide hydroxide and the chemical potential affect the formation of nanorods. The photoluminescence (PL) instrument is used to investigate the optical properties of the Eu(OH)₃ nanorods and its abnormal luminescence behaviors are observed.     

Humidity sensing properties of Ni(OH)2 nanoparticles synthesized via sonochemical method

This work focuses on humidity sensor based Ni(OH)₂ nanoparticles. The sonochemical method was employed to prepare nanoparticles and impedance analysis was used to characterize sensitivity, response, and recovery time of the prepared sensor. The Ni(OH)₂ sensor was found to have high sensitivity and fast response/recovery time to humidity, and its impedance changed approximately two orders of magnitude from about 2.01 MΩ in dry air 20% RH (relative humidity) to 0.0258 MΩ in 90% RH air. Our results demonstrate the potential application of Ni(OH)₂ nanoparticles for fabricating high performance humidity sensors.     

Investigation of the doped transition metal promotion effect on CO2 chemisorption on Ni (1 1 1)

The chemisorption of CO₂ on the pure Ni (1 1 1) and doped Ni (1 1 1) by transition metal (Co, Rh, Cr, Ce, La) were investigated by using the generalized gradient approximation (GGA) and the Perdew–Burke–Emzerhof (PBE) functional. The optimized structure of doped metal surface showed that Rh, Cr, Ce, La atoms upward shift from the surface of Ni (1 1 1) plane, while the atom radius of Co is the minimum offset which lead to the height is ?0.03 Å. The ability of CO₂ chemisorption follows the order of La/Ni (1 1 1) > Ce/Ni (1 1 1) > Cr/Ni (1 1 1) > Co/Ni (1 1 1) > pure Ni (1 1 1). It is exothermic when CO₂ chemisorbed on Cr/Ni (1 1 1) Ce/Ni (1 1 1) and La/Ni (1 1 1), while it is endothermic on the Co/Ni (1 1 1) and pure Ni (1 1 1). CO₂ molecular chemisorbed on all the metal surfaces are negatively charged, result from the electron transfer between the metal surfaces and the CO₂ molecular. The transition metals La, Ce and Cr can promote the transformation of electron and make the CO bonds longer than the pure Ni (1 1 1). We also analyzed the dissociation of CO₂ on the Ni-based surface and found that the La/Ni (1 1 1) surface is the preference surface for the dissociation of CO₂, which improved the ability to hinder carbon deposition.     

Estimation of the solubility product of hydrocalumite–hydroxide,a layered double hydroxide with the formula of [Ca2Al(OH)6]OH·nH2O

From aqueous NaOH/Ca(OH)₂/NaAl(OH)₄ mixtures, after allowing short reaction times we observed the precipitation of Ca(OH)₂(s) at lower, and a mixture of Ca(OH)₂(s) and a layered double hydroxide, hydrocalumite (HC) at higher aluminate concentrations. From the maximum aluminate concentration, at which the equilibrium solid phase is still portlandite (i.e., further increase in the aluminate concentration results in HC appearing in the precipitate beside the portlandite), the concentration based solubility products of two polymorphs of HC with the formula of [Ca₂Al(OH)₆]OH·nH₂O (differing in n) has been estimated and was found to be log L_HC=−11.4 at 25 °C and −12.1 at 75 °C, respectively (where L_HC=[Ca²⁺]²[Al(OH)₄⁻][OH⁻]³) and at constant ionic strength (I=1 M NaCl). To the best of our knowledge, this is the first published estimate for the solubility product of hydrocalumite. Additionally, from the composition obtained for NaOH/Ca(OH)₂/NaAl(OH)₄ mother liquors in equilibrium with Ca(OH)₂(s), attempts were made to extract the formation constant of the ion pair CaAl(OH)₄⁺. It was found, that the effects caused by the supposed formation of this solution species are too small to be reliably determined, which allowed an upper estimate for its formation constant, K, to be suggested in the temperature range of 25–75 °C (K<200 and 40 M⁻¹ at 25 and 75 °C, respectively).     

Mono(pyridine-N-oxide) analog of DOTA as a suitable organic reagent for a sensitive and selective fluorimetric determination of Ln(III) ions

The mono(pyridine-N-oxide) analog of the H₄dota macrocylic ligand, H₃do3a-py^NO, is capable of forming thermodynamically stable and kinetically inert Ln(III) complexes. Its Eu(III) and Tb(III) complexes display a strong long-lived fluorescence as a result of the antenna effect of the pyridine-N-oxide fluorophore in the reagent. It is shown that H₃do3a-py^NO can be used as a fluorogenic reagent for the determination of Eu(III) and Tb(III) at pH 6.5 and c_L=1 mM. At an excitation wavelength of 286 nm, the emission maxima are 615 nm (Eu(III)-complex), and 547 nm (Tb(III)complex). Detection limits are at concentrations around 1.0 μM and linearity of the method spans over 2 orders of magnitude. The method was applied to artificial and real samples (spiked mineral waters, extracts from cathode ray tube luminophore dust) and gave satisfactory results. The method is simple, rapid, and hardly interfered by other metal ions.     

Spray pyrolyzed NiO–C nanocomposite as an anode material for the lithium-ion battery with enhanced capacity retention

NiO–C nanocomposite was prepared by a spray pyrolysis method using a mixture of Ni(NO₃)₂ and citric acid solution at 600 °C. The microstructure and morphology of the NiO–C composite were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) mapping, and thermogravimetric analysis (TGA). The results showed that the NiO nanoparticles were surrounded by amorphous carbon. Electrochemical tests demonstrated that the NiO–C nanocomposites exhibited better capacity retention (382 mAh g^− 1 for 50 cycles) than that of pure NiO (141 mAh g^− 1 for 50 cycles), which was also prepared by spray pyrolysis using only Ni(NO₃)₂ as precursor. The enhanced capacity retention can be mainly attributed to the NiO–C composite structure, composed of NiO nanoparticles surrounded by carbon, which can accommodate the volume changes during charge–discharge and improve the electrical conductivity between the NiO nanoparticles.     

Synthesis of nanoparticles of CoxFe(3−x)O4 by combustion reaction method

Nanocrystalline magnetic particles of Co_xFe_(3−x)O₄, with x ranging from 0.79 to 1.15, has been synthesised by combustion reaction method using iron nitrate Fe(NO₃)₃.9H₂O, cobalt nitrate Co(NO₃)₂·6H₂O, and urea CO(NH₂)₂ as fuel without template and subsequent heat treatment. The process is quite simple and inexpensive since it does not involve intermediate decomposition and/or calcining steps. The maximum reaction temperature ranged from 850 to 1010 °C and combustion lasted less then 30 s for all systems. X-ray diffraction patterns of all systems showed broad peaks consistent with cubic inverse spinel structure of CoFe₂O₄. The absence of extra reflections in the diffraction patterns of as-prepared materials ensures phase purity. The average crystallite sizes determined from the prominent (3 1 1) peak of the diffraction using Scherre's equation and TEM micrographs consisted of ca. 27 nm in spherical morphology. FTIR spectra of the as-prepared material showed traces of organic and metallic salts byproducts. However, when the same material was washed with deionised water the byproducts were rinsed off, resulting in pure materials. Magnetic properties such as saturation magnetisation, remanence magnetisation and coercivity field measured at room temperature were 48 emu/g, 15 emu/g and 900 Oe, respectively.     

Sonochemical synthesis of Dy2(CO3)3 nanoparticles,Dy(OH)3 nanotubes and their conversion to Dy2O3 nanoparticles

Dysprosium carbonates nanoparticles were synthesized by the reaction of dysprosium acetate and NaHCO₃ by a sonochemical method. Dysprosium oxide nanoparticles with average size about 17 nm were prepared from calcination of Dy₂(CO₃)₃·1.7H₂O nanoparticles. Dy(OH)₃ nanotubes were synthesized by sonication of Dy(OAC)₃·6H₂O and N₂H₄. The as-synthesized nanostructures were characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR). Photoluminescence measurement shows that the nanoparticles have two emission peaks around 17,540 cm^?1 and 20,700 cm^?1, which should come from the electron transition from ⁴F_9/2 → ⁶H_15/2 levels and ⁴F_9/2 → ⁶H_13/2 levels, respectively. The effect of calcination temperature and sonication time was investigated on the morphology and particle size of the products. The sizes could be controlled by the feeding rate of the precipitating agent (NaHCO₃ and N₂H₄) and slower feeding rate lead to smaller nanoparticles.     

Hydrothermal synthesis and magnetic studies of transition metal nocerites M3(BO3)F3 (M=Fe,Co, Ni)

Polycrystalline samples of M₃(BO₃)F₃ (M=Fe, Co, Ni), isostructural with nocerite Mg₃(BO₃)(OH,F)₃, have been prepared in supercritical hydrothermal conditions. These compounds represent with boracites, M₃B₇O₁₃F (M=Mg, Cr, Mn, Fe, Co, Zn), the only transition metal fluoride borates known to date. Co₃(BO₃)F₃ and Ni₃(BO₃)F₃ are antiferromagnetic with T_N=17(2) and 40(2) K, respectively. Spin-flop transitions at B_C1=4.0 T and B_C2=7.5 T occur at 1.6 K in Co₃(BO₃)F₃, while a parasitic ferromagnetism (0.02 μ_B/Ni²⁺ at 1.6 K) appears below T_N in Ni₃(BO₃)F₃. The magnetic structures consist of three spin sub-lattices of double rutile-type ferromagnetic chains.     

Surface modification of Ni and Co metal nanowires through MeV high energy ion irradiation

Nickel (Ni) and cobalt (Co) metal nanowires were fabricated by using an electrochemical deposition method based on an anodic alumina oxide (Al₂O₃) nanoporous template. The electrolyte consisted of NiSO₄ · 6H₂O and H₃BO₃ in distilled water for the fabrication of Ni nanowires, and of CoSO₄ · 7H₂O with H₃BO₃ in distilled water for the fabrication of the Co ones. From SEM and TEM images, the diameter and length of both the Ni and Co nanowires were measured to be ∼ 200 nm and 5–10 μm, respectively. We observed the oxidation layers in nanometer scale on the surface of the Ni and Co nanowires through HR–TEM images. The 3 MeV Cl²⁺ ions were irradiated onto the Ni and Co nanowires with a dose of 1 × 10¹⁵ ions/cm². The surface morphologies of the pristine and the 3 MeV Cl²⁺ ion-irradiated Ni and Co nanowires were compared by means of SEM, AFM, and HR–TEM experiments. The atomic concentrations of the pristine and the 3 MeV Cl²⁺ ion-irradiated Ni and Co nanowires were investigated through XPS experiments. From the results of the HR–TEM and XPS experiments, we observed that the oxidation layers on the surface of the Ni and Co nanowires were reduced through 3 MeV Cl²⁺ ion irradiation.     

Effect of processing conditions on sonochemical synthesis of nanosized copper aluminate powders

Nanosized copper aluminate (CuAl₂O₄) spinel particles have been prepared by a precursor approach with the aid of ultrasound radiation. Mono-phasic copper aluminate with a crystallite diameter of 17 nm along the (3 1 1) plane was formed when the products were synthesized using Cu(NO₃)₂·6H₂O and Al(NO₃)₃·9H₂O as starting materials, with urea as a precipitation agent at a concentration of 9 M. The reaction was carried out under ultrasound irradiation at 80 °C for 4 h and a calcination temperature of 900 °C for 6 h. The synthesized copper aluminate particles and the effect of different processing conditions such as the copper source, precipitation agents, sonochemical reaction time, calcination temperature and time were analyzed and characterized by the techniques of powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and Fourier transformation infrared spectroscopy (FT–IR).     

Sonocatalytic injury of cancer cells attached on the surface of a nickel–titanium dioxide alloy plate

The present study demonstrates ultrasound-induced cell injury using a nickel–titanium dioxide (Ni–TiO₂) alloy plate as a sonocatalyst and a cell culture surface. Ultrasound irradiation of cell-free Ni–TiO₂ alloy plates with 1 MHz ultrasound at 0.5 W/cm² for 30 s led to an increased generation of hydroxyl (OH) radicals compared to nickel–titanium (Ni–Ti) control alloy plates with and without ultrasound irradiation. When human breast cancer cells (MCF-7 cells) cultured on the Ni–TiO₂ alloy plates were irradiated with 1 MHz ultrasound at 0.5 W/cm² for 30 s and then incubated for 48 h, cell density on the alloy plate was reduced to approximately 50% of the controls on the Ni–Ti alloy plates with and without ultrasound irradiation. These results indicate the injury of MCF-7 cells following sonocatalytic OH radical generation by Ni–TiO₂. Further experiments demonstrated cell shrinkage and chromatin condensation after ultrasound irradiation of MCF-7 cells attached on the Ni–TiO₂ alloy plates, indicating induction of apoptosis.     

Exploring the electronic structure of Pb2+ ions containing material Pb16(OH)16(NO3)16

A theoretical band structure calculation for lead nitrate hydroxide Pb₁₆(OH)₁₆(NO₃)₁₆ single crystal was performed based on the experimental crystallographic data obtained by Chang et al. Calculations exhibit that the conduction band minimum (CBM) is situated at Γ the center of the Brillouin zone (BZ) while the valence band maximum (VBM) is located between Γ and Y points of the BZ, resulting in an indirect energy band gap of about 3.70 eV in close agreement to the measured one (3.78 eV). The angular momentum resolved projected density of states reveals the existence of the strong hybridization between the orbitals and the VBM is originated from Pb-6s/6p and O-2p orbitals while the CBM from N-2p and Pb-6p orbitals. The calculated valence electronic charge density distribution explore the bond characters and the dominancy of the covalent bonding between Pb–O of PbO_n ployhedra and N–O of [NO₃]⁻ triangle. The calculated bond lengths and angles show good agreement with the experimental data.     

Detection of OH radical and O atom during triboluminescence of hydrated cerium/terbium sulfates

Triboluminescence of Се₂(SO₄)₃·8H₂O and Tb₂(SO₄)₃·8H₂O crystals has been studied. For the first time spectral evidence for a contribution of light-emitting products OH^? (283 and 290 nm maxima, 1–0 transition; 308.4 and 309.6 nm, 0–0 transition) and excited oxygen atom O^? (777 nm, 3P⁵P—3S⁵S) produced via mechano-chemical decomposition of H₂O and O₂ molecules in the destruction of crystal hydrates of the salts to the gas-phase component of triboluminescence has been obtained.     

Ultrasound-assisted mineralization of organic contaminants using a recyclable LaFeO3 and Fe3+/persulfate Fenton-like system

A recyclable heterogeneous catalyst has been successfully developed for application in a Fenton-type advanced oxidation process without adding external H₂O₂. LaFeO₃ was prepared from Fe(NO₃)₃·9H₂O and La(NO₃)·6H₂O by a simple sol-gel method and its catalytic efficiency was evaluated for mineralization of 4-chlorophenol using a Fenton-like process. The mineralization process was carried out under ultrasonication in presence of heterogeneous LaFeO₃ catalyst with H₂O₂ that was produced during ultrasonication. The mineralization process was monitored through total organic carbon (TOC) analysis. Very importantly, utmost 5-fold synergism was evidenced by the ultrasound mediated LaFeO₃-catalyzed system. Besides, more than twofold synergism was observed by combining the ultrasound assisted LaFeO₃ catalytic process and potassium persulfate (KPS) assisted advanced oxidation process. It is worth to mention that complete mineralization (∼96%) of 4-chlorophenol (initial concentration of 1.25 × 10⁻⁴ M) was observed within 1 h in the presence of LaFeO₃ (0.5 g L⁻¹) and KPS (1.0 mmol) under ultrasonication (40 kHz). Even after four cycles, the activity of LaFeO₃ remained intact which proved its recyclability. Extremely reusable heterogeneous LaFeO₃ catalyst makes the system more interesting from both economic and environmental points of view.     

Enhanced UVB emission and analysis of chemical states of Ca5(PO4)3OH:Gd3+,Pr3+ phosphor prepared by co-precipitation

Hydroxyapatite (Ca₅(PO₄)₃OH) is a well-known bioceramic material used in medical applications because of its ability to form direct chemical bonds with living tissues. This mineral is currently used as a host for rare-earth ions (e.g. Gd³⁺, Pr³⁺, Tb³⁺, etc.) to prepare phosphors that can be used in light emitting devices of different types. In this study Ca₅(PO₄)₃OH:Gd³⁺,Pr³⁺ phosphors were prepared by the co-precipitation method and were characterised by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, high resolution transmission electron microscopy, energy dispersive x-ray spectroscopy and photoluminescence spectroscopy. The x-ray diffraction pattern was consistent with the hexagonal phase of Ca₅(PO₄)₃OH referenced in JCPDS card number 73-0293. The x-ray photoelectron spectroscopy data indicated that Ca²⁺ occupied two different lattice sites, referred to as Ca1 and Ca2. The photoluminescence data exhibited a narrowband emission located at 313 nm, which is associated with the ⁶P_7/2→⁸S_7/2 transition of the Gd³⁺ ion. This emission is classified as ultraviolet B and it is suitable for use in phototherapy lamps to treat various skin diseases. The photoluminescence intensity of the 313 nm emission was enhanced considerably by Pr³⁺ co-doping.     

Ab-initio study of Sr-doping effects on nitric oxide adsorption on the LaO (001) surface of LaFeO3

Density-functional calculations of molecular nitric oxide (NO) on defective (La,Sr)O (001) surfaces of (La,Sr)FeO_3 ? δ using slab models are performed to elucidate the oxygen vacancy formation problem on the LaO (001) surface of LaFeO_3 ? δ.From the estimation of the NO adsorption energy, NO adsorption is found on (La,Sr)O surfaces of (La_0.83,Sr_0.17)FeO_3 ? δ with δ = 0 or 0.25.The absolute value of the NO adsorption energy shows a remarkable increase at oxygen vacancies in the top surface layer, where the nitrogen atoms of the adsorbed molecules are embedded in the first (La,Sr)O layer, because a bond with Fe in the second FeO₂ layer is formed.Our data shows that Sr doping promotes formation of oxygen vacancies, which keep the NO adsorption ability high.Thus, we conclude that if Sr doping increases the number of oxygen vacancy sites by a charge compensation effect, NO adsorption on LaFeO₃ is enhanced, which provides an explanation for several experimental observations.     

First analysis of the 3ν9−ν9 hot band of difluoroboric acid (BF2OH). Further evidence of large amplitude effects for the OH torsion

The hot band 3ν₉?ν₉ of the isotopologue ¹¹BF₂OH (difluoroboric acid) located at 1034.78 cm^?1 was investigated for the first time by Fourier transform infrared spectroscopy. During previous studies both, the ν₉ mode (OH-torsion relative to the BF₂ moiety, at 522.87 cm^?1) and the ν₄ mode (in-plane OH bend) had been shown to exert large amplitude motion, and splittings of 0.0051 and 0.0038 cm^?1 had been observed in the interacting 2ν₉ and ν₄ bands located at 1042.87 and 961.49 cm^?1, respectively. The present work establishes large amplitude effects also for the 9³ excited state located at 1557.655 cm^?1. Numerous P and R transitions of the 3ν₉–ν₉ hot band were identified in the 2ν₉ manifold, and doublets corresponding to a torsional splitting of 0.031 cm^?1 in the 9³ state were observed. The vibrational assignment of the 9³ state was confirmed by the detection of the 3ν₉?2ν₉ hot band Q branch in the 19 μm region.     

Facile synthesis of low-dimensional SnO2 nanostructures: An investigation of their performance and mechanism of action as anode materials for lithium-ion batteries

Owing to high-energy density of rechargeable lithium-ion batteries (LIBs), they have been investigated as an efficient electrochemical power sources for various energy applications. High theoretical capacities of tin oxide (SnO₂) anodes have led us a path to meet the ever-growing demands in the development of high-performance electrode materials for LIBs. In this paper, a facile approach is described for the synthesis of porous low-dimensional nanoparticles and nanorods of SnO₂ for application in LIBs with the help of Tween-80 as a surfactant. The SnO₂ samples synthesized at different reaction temperatures produced porous nanoparticles and nanorods with average diameters of ~7–10 nm and ~70–110 nm, respectively. The SnO₂ nanoparticle electrodes exhibit a high reversible charge capacity of 641.1 mAh/g at 200 mA/g after 50 cycles, and a capacity of 340 mAh/g even at a high current density of 1000 mA/g during the rate tests, whereas the porous nanorod electrodes delivers only 526.3 mAh/g at 200 mA/g after 50 cycles and 309.4 mAh/g at 1000 mA/g. It is believed that finer sized SnO₂ nanoparticles are much more favorable to trap more Li⁺ ion during electrochemical cycling, resulting in a large irreversible capacity. In contrast, rapid capacity fading was observed for the porous nanorods, which is the result of their pulverization resulting from repeated cycling.     

Ni(NO3)2·6H2O/I2/water: A new,mild and efficient system for the selective oxidation of alcohols into aldehydes and ketones under sonic condition

A new, simple, efficient and rapid method for the oxidation of alcohols into respective aldehydes and ketones by Ni(NO₃)₂·6H₂O/I₂/water system under ultrasonic irradiation is reported. The process is mild and inexpensive; the yields are high and the reactions go to completion within 2–7 min.