Fast formation of thick and transparent titania nanotubular films from sputtered Ti

Ti films sputtered on transparent fluorine-doped tin oxide glass substrates were anodized in fluoride-containing organic electrolyte in the presence of H₂O. In this work, anodic TiO₂ nanotubes (ATNs) as long as 9.2 ± 0.3 μm were obtained with high growth rate of 0.64 ± 0.3 μm min^?1. We demonstrated the optimum anodization conditions for ATN growth on foreign substrates, were within the range of 0.3–0.5% (wt) NH₄F, with 3–5% (vol) H₂O at 60 V. XPS and ICP-MS were utilized to elucidate the increase of thickness and volume expansion obtained from the sputtered Ti film to their ATN forms. The ATN films exhibited excellent uniformity and adhesion to the substrates.     

Electrochemical formation of self-organized zirconium titanate nanotube multilayers

The present work reports the formation of multilayers of self-organized zirconium titanate nanotubes by anodizing a Ti–35Zr alloy in 1 M (NH₄)₂SO₄ + 0.5 wt% NH₄F electrolytes. It was found that multilayers consisting of different diameter nanotubes can be produced by repeated anodization steps under different conditions. Formation of new nanotubes starts in the gaps between the existing tubes. The process allows the formation of multilayer stacks consisting of layers of several 100 nm in length and adjustable nanotube diameters in a range from 50 to 180 nm.     

Novel poly (neutral red) nanowires as a sensitive electrochemical biosensing platform for hydrogen peroxide determination

Poly (neutral red) nanowires (PNRNWs) have been synthesized for the first time by the method of cyclic voltammetric electrodeposition using porous anodic aluminum oxide (AAO) template and were examined by scanning electron microscopy (SEM) and transmission electron microscope (TEM). Moreover, horseradish peroxidase (HRP) was encapsulated in situ in PNRNWs (denoted as PNRNWs–HRP) by electrochemical copolymerization for potential biosensor applications. The PNRNWs showed excellent efficiency of electron transfer between the HRP and the glassy carbon (GC) electrode for the reduction of H₂O₂ and the PNRNWs–HRP modified GC electrode showed to be excellent amperometric sensors for H₂O₂ at −0.1 V with a linear response range of 1 μM to 8 mM with a correlation coefficient of 0.996. The detection limit (S/N = 3) and the response time were determined to be 1 μM and <5 s and the high sensitivity is up to 318 μA mM⁻¹ cm⁻².     

Iron(II) spin transition 1,2,4-triazole chain compounds with novel inorganic fluorinated counteranions

New one-dimensional spin transition coordination polymers of formula [Fe(NH₂trz)₃](AF₆) · nH₂O (A = Ti, Zr, Sn; NH₂trz = 4-amino-1,2,4-triazole) have been synthesized in MeOH and EtOH media. These materials display an abrupt and hysteretic spin transition around 200 K as well as a reversible thermochromic effect on cooling. A preliminary evaluation of the lattice dynamics in the high-spin and low-spin states is presented.     

Effect of water content of ethylene glycol as electrolyte for synthesis of ordered titania nanotubes

Anodization of Ti using fluoride containing polyhydric alcohols such as ethylene glycol or glycerol as electrolyte results in ordered arrays of TiO₂ nanotubes with a smooth surface and a very high aspect ratio. However, the reproducibility of the result is affected by many experimental parameters, notably the water content. In this investigation, anodizations of Ti foil in anhydrous ethylene glycol +0.2 wt% NH₄F solution (EG solution) with 0–1.0 wt% water additions were carried out at 20 V for 45 min in a dry-argon filled controlled-atmosphere glove box. It was observed that a minimum amount of 0.18 wt% of water addition was required to form a well ordered TiO₂ nanotubular arrays. When the anhydrous EG solution was reused for third time, ordered arrays of nanotubes started to form. When the water addition to the EG solution was more than 0.5 wt%, formation of ridges was observed on the nanotubes. XPS results showed presence of un-anodized Ti element in the anhydrous condition and presence of organic and (NH₄)₂TiF₆ type compounds in all the anodized samples in addition to the regular TiO₂ phase. The results underline the influence of water content and local pH condition to form the ordered nanotubular arrays.     

Enhancing the bioactivity of zirconium with the coating of anodized ZrO2 nanotubular arrays prepared in phosphate containing electrolyte

Bioactive zirconium oxide nanotubular arrays on zirconium alloys are prepared electrochemically in fluoride and phosphate containing electrolyte. Geometric factors of the ZrO₂ nanotubular layers, particularly the pore diameter and thickness, are affected by the electrochemical conditions, including applied potential and anodization time. Under specific sets of conditions, highly ordered ZrO₂ nanotubular arrays are formed with diameters varying from 30 nm to 75 nm and lengths varying from 2 μm to 12 μm. XPS shows that the nanotubular layer contains a significant amount of phosphate species distributed almost homogeneously over the entire tubular length. The ZrO₂ nanotubular layer formed in fluoride and phosphate containing electrolyte highly enhances the formation of bioactive hydroxyapatite coating in simulated biological fluid (SBF).     

High performance cathode-supported SOFC with perovskite anode operating in weakly humidified hydrogen and methane

A high performance cathode-supported solid oxide fuel cell (SOFC), suitable for operating in weakly humidified hydrogen and methane, has been developed. The SOFC is essentially made up by a YSZ/LSM composite supporting cathode, a thin YSZ film electrolyte, and a GDC-impregnated La_0.75Sr_0.25Cr_0.5Mn_0.5O₃ (LSCM) anode. A gas tight thin YSZ film (∼27 μm) was formed during the co-sintering of cathode/electrolyte bi-layer at 1200 °C. The cathode-supported SOFC developed in this study showed encouraging performance with maximum power density of 0.182, 0.419, 0.628 and 0.818 W cm⁻² in air/3% H₂O–97% H₂ (and 0.06, 0.158, 0.221 and 0.352 W cm⁻² in air/3% H₂O–97% CH₄) at 750, 800, 850 and 900 °C, respectively. Such performance is close to that of the cathode-supported cell (0.42 W cm⁻² vs. 0.455 W cm⁻² in humidified H₂ at 800 °C) developed by Yamahara et al. [Solid State Ionics 176 (2005) 451–456] with a Co-infiltrated supporting LSM-YSZ cathode, a (Sc₂O₃)_0.1(Y₂O₃)_0.01(ZrO₂)_0.89 (SYSZ) electrolyte of 15 μm in thickness and a SYSZ/Ni anode, indicating that the performance of the GDC-impregnated LSCM anode is comparable to that made of Ni cermet while stable in weakly humidified methane fuel.     

The application of Bimetallic metal–organic frameworks for antibiotics adsorption

Fe/Zr-base metal–organic frameworks(Fe/Zr-MOFs) were prepared using a solvothermal method from 1,3,5-phthalic acid (H₃BTC, 98 %) as the organic chain and ferrous heptahydrate (FeSO₄·7H₂O) and zirconium acetate Zr(CH₃COO)₄] as the metal ions. The resulting material was used to remove Doxycycline hydrochloride (DC). The experimental results showed that when the concentration of DC was 10 ppm and the mass of Zr/Fe-MOFs was 100 mg, the maximum removal rate after 5 h was 87.5 %. The results showed that the correlation coefficients (R²) of the pseudo-second-order kinetics model and Freundlich isotherm model of Zr/Fe-MOFs adsorption of DC were greater than 0.99, indicating good consistency. The results showed that the adsorption process of DC by Zr/Fe-MOFs was endothermic and spontaneous. Fe/Zr-MOFs had a high adsorption capacity for DC removal and good application prospects.     

Porous cuprous oxide microcubes for non-enzymatic amperometric hydrogen peroxide and glucose sensing

Using porous cuprous oxide (Cu₂O) microcubes, a simple non-enzymatic amperometric sensor for the detection of H₂O₂ and glucose has been fabricated. Cyclic voltammetry (CV) revealed that porous Cu₂O microcubes exhibited a direct electrocatalytic activity for the reduction of H₂O₂ in phosphate buffer solution and the oxidation of glucose in an alkaline medium. The non-enzymatic amperometric sensor used in the detection of H₂O₂ with detection limit of 1.5 × 10^?6 M over wide linear detection ranges up to 1.5 mM and with a high sensitivity of 50.6 μA/mM. This non-enzymatic voltammetric sensor was further utilized in detection of glucose with a detection limit of 8.0 × 10^?7 M, a linear detection range up to 500 μM and with a sensitivity of ?70.8 μA/mM.     

Ammonium beryllium selenate dihydrate, (NH4)2Be(SeO4)2·2H2O: Preparation,X-ray powder diffraction,and vibrational spectra

The solubility in the three-component (NH₄)₂SeO₄–BeSeO₄–H₂O system is studied at 25 °C by the method of isothermal decrease of supersaturation. (NH₄)₂Be(SeO₄)₂·2H₂O crystallizes from solutions containing 31.35 mass% beryllium selenate and 30.66 mass% ammonium selenate up to solutions containing 26.84 mass% beryllium selenate and 46.84 mass% ammonium selenate. The X-ray powder diffraction data show that (NH₄)₂Be(SeO₄)₂·2H₂O is isostructural with the respective K₂Be(SeO₄)₂·2H₂O, K₂Be(SO₄)₂·2H₂O and Rb₂Be(SO₄)₂·2H₂O. (NH₄)₂Be(SeO₄)₂·2H₂O crystallizes in the monoclinic space group P2₁/c: a = 11.747(3) Å, b = 12.212(4) Å, c = 7.649(2) Å, β = 96.94(3)°, V = 1089.3(3) Å³, Z = 4. Vibrational spectra (infrared and Raman) of the title compound are presented and discussed with respect to the internal modes of both the ammonium and the selenate tetrahedra, hydrogen bond strengths and the lattice vibrations of the BeO₄ tetrahedra (skeleton vibrations).     

Atomic layer deposition of TiO2 nanotubes and its improved electrostatic capacitance

Titanium dioxide (TiO₂) nanotubes are fabricated into anodic aluminum oxide (AAO) membrane via atomic layer deposition (ALD). For the ALD of TiO₂, gaseous precursors, titanium (IV) isopropoxide and water are sequentially applied and chemically reacted with each other. A thickness of nanotubes is precisely controlled by the applied cycle numbers of ALD and the morphology of nanostructures is investigated by SEM and TEM. The amorphous property of TiO₂ nanostructures is revealed by XRD and the composition of nanotubes is measured by TEM–EDX. The impurity contents and binding structure of the nanostructures are analyzed by XPS. The electrostatic capacitance of TiO₂ nanotubes into AAO is 480 μF/cm² and it is about 3 times higher compared with AAO membrane (172 μF/cm²).     

Spray deposited amorphous RuO2 for an effective use in electrochemical supercapacitor

The structural, surface morphological and optical properties of sprayed ruthenium oxide thin film were investigated using XRD, SEM and optical absorption measurements. The structural analysis from XRD pattern showed the formation of RuO₂ in amorphous phase. The scanning electron micrographs revealed network-like morphology of ruthenium oxide. The optical studies showed a direct band gap of 2.4 eV for ruthenium oxide films. Ruthenium oxide thin film exhibited a cyclic voltammogram indicative high reversibility of a typical capacitive behavior in 0.5 M H₂SO₄ electrolyte. A specific capacitance of 551 F/g was obtained with ruthenium oxide thin film (electrode) prepared by spray pyrolysis method. The specific capacitances of 551 and 450 F/g at the scan rate of 5 and 125 mV/s, respectively, indicate that the capacitance value varies inversely with scan rate.     

Synthesis of Co3O4 nanostructures using a solvothermal approach

The controlled synthesis of Co₃O₄ nanostructures with morphologies of micro-spheres, nanobelts, and nanoplates was successfully achieved by a simple solvothermal method. Various comparison experiments showed that several experimental parameters, such as the reaction temperature and the concentration of NH₃·H₂O, play important roles in the morphological control of Co₃O₄ nanostructures. A lower temperature and a lower concentration of NH₃·H₂O favor spherical products with a diameter of 1–1.5 μm, whereas a higher temperature and a higher concentration of NH₃·H₂O generally lead to the formation of nanobelts with a width of 20–150 nm. In addition, Co₃O₄ hexagonal nanoplates with an edge length of about 200–300 nm are also obtained by adding surfactant CTAB. A rational mechanism is proposed for the selective formation of various morphologies. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and field-emission scanning electron microscope (FE-SEM) were used to characterize the products.     

F–B-codoping of anodized TiO2 nanotubes using chemical vapor deposition

Chemical vapor deposition (CVD) was firstly used to simultaneously codope fluorine and boron into TiO₂ nanotubes anodized Ti in C₂H₂O₄ · 2H₂O + NH₄F electrolyte. F–B-codoping was successfully carried out by annealing the anodized TiO₂ nanotubes through CVD, as evidenced from XPS analysis. SEM images showed that the higher the annealing temperature, the greater structure damage of F–B-codoped sample. XRD results confirmed that annealing temperature had an influence on the phase structure and boron and fluorine impurities could retard anatase–rutile phase transition. F–B-codoped samples displayed remarkably strong absorption in both UV and visible range. Under visible-light irradiation, F–B-codoped samples showed the higher I_ph and catalytic activity in methyl orange photoelectrodegradation than F-doped sample and B-doped sample. This showed a convincing evidence of F–B-codoping of TiO₂ had an obvious synergistic effect on the enhancement of photocurrents and photoelectrocatalytic activity.     

Sulfur tolerant redox stable layered perovskite SrLaFeO4 − δ as anode for solid oxide fuel cells

Redox stable K₂NiF₄ type layered perovskite SrLaFeO_4 − δ(SLFO_4 − δ) has been prepared and evaluated as anode for solid oxide fuel cell (SOFC). The SLFO_4 − δ shows linear thermal expansion behavior with TEC of 14.3 × 10^− 6 K^− 1. It also demonstrates excellent catalytic activity for various fuels. A scandia stabilized zirconia (ScSZ, 180 μm) electrolyte supported SOFC with the anode achieves maximum power densities (P_max) of 0.93, 0.76, 0.63, and 0.46 Wcm^− 2 at 900–750 °C, respectively, in wet H₂. P_maxs of cells supported by 250 μm ScSZ reach 0.57, 0.60 and 0.50 Wcm^− 2 in H₂, H₂ + 50 ppm H₂S and propane, respectively, at 800 °C. Moreover, the cells show stable power output during ~ 100 h operation at 800 °C under 0.7 V in various fuels. The P_max at 800 °C in wet H₂ even increases by ~ 11% in the subsequent two thermal cyclings, indicating that SLFO_4 − δ is a promising anode candidate for SOFC with good electro-catalytic activity, high stability and resistance to sulfur and coking.     

Dimeric and monomeric palladium(II) parent-amido (NH2) complexes: Synthesis,characterization, and reactivity

The treatment of [PdL₃(NH₃)]OTf (L₃ = (PEt₃)₂(Ph) (1), (2,6-(Cy₂PCH₂)₂C₆H₃) (3)) with NaNH₂ in THF afforded dimeric and monomeric parent-amido palladium(II) complexes with bridging and terminal NH₂, respectively, anti-[Pd(PEt₃)(Ph)(μ-NH₂)]₂ (2) and Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂) (4). The dimeric complex 2 crystallizes in the space group P2₁/n with a = 13.228(2) Å, b = 18.132(2) Å, c = 24.745(2) Å, β = 101.41(1)°, and Z = 4. It has been found that there are two crystallographically independent molecules with Pd(1)–Pd(2) and Pd(3)–Pd(4) distances of 2.9594 (10) and 2.9401(9) Å, respectively. The monomeric amido complex 4 protonates from trace amounts of water to give the cationic ammine species [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₃)]⁺. Complex 4 reacts with diphenyliodonium triflate ([Ph₂I]OTf) to give aniline complex [Pd(2,6-(Cy₂PCH₂)₂C₆H₃)(NH₂Ph)]OTf (5). Reaction of 4 with dialkyl acetylenedicarboxylate (DMAD, DEAD) yields diastereospecific palladium(II) vinyl derivative (Z)–(Pd(Cy₂PCH₂)₂C₆H₃)(CR = CR(NH₂)) (R = CO₂Me (6a), CO₂Et (6b)). Reacting complexes 6a and 6b with p-nitrophenol produces (Pd(Cy₂PCH₂)₂C₆H₃)(OC₆H₄–p-NO₂) (8) and cis-CHR = CR(NH₂), exclusively.     

Isopiestic studies on the saturated systems {H2O + BaCl2(sat) + NaCl + NH4Cl} and {H2O + BaCl2(sat) + mannitol(sat) + NaCl + NH4Cl} at the temperature 298.15 K: Comparison with the ideal-like solution model

Isopiestic measurements have been carried out at the temperature 298.15 K for two saturated aqueous solutions: {H₂O + BaCl₂(sat) + NaCl + NH₄Cl} saturated with barium chloride and {H₂O + BaCl₂(sat) + mannitol(sat) + NaCl + NH₄Cl} saturated with barium chloride and mannitol. Taking sodium chloride (aq) as reference solutions, osmotic coefficients of the aqueous solutions were determined. The experimental results are well represented by the ideal-like solution model.     

Dual-signal anodic stripping voltammetric determination of trace arsenic(III) at a glassy carbon electrode modified with internal-electrolysis deposited gold nanoparticles

A glassy carbon electrode (GCE) modified with internal-electrolysis deposited gold nanoparticles (AuNPs_ied) was applied to sensitively and selectively detect As(III) by anodic stripping linear sweep voltammetry (ASLSV). The AuNPs_ied/GCE was prepared based on the redox replacement reaction between a supporting-electrolyte-free aqueous HAuCl₄ and a copper sheet in saturated KCl separated by a salt bridge. Under optimum conditions (0.5 M aqueous H₂SO₄, 300-s preconcentration at − 0.4 V), the ASLSV peak current for the As(0)–As(III) oxidation responded linearly to As(III) concentration from 0.02 to 3 μM with a limit of detection (LOD) of 0.9 nM (0.07 μg L^− 1) (S/N = 3), while that for the As(III)–As(V) oxidation was linear with As(III) concentration from 0.02 to 1 μM with a LOD of 4 nM (0.3 μg L^− 1) (S/N = 3). An appropriate high-scan-rate for ASLSV can enhance both the sensitivity and signal-to-noise ratio. This method was applied for analyses of As(III) in real water samples.     

Crystal structure of a new small-pore zirconosilicate Na2ZrSi2O7·H2O and its relation to stoichiometrically and topologically similar compounds

The small-pore zirconosilicate Na₂ZrSi₂O₇·H₂O crystallizes in monoclinic system with space group C2/c, a = 5.4715(4); b = 9.4111(6); c = 13.0969(8) Å, β = 92.851(7)°. Its framework consists of layers built of ZrO₆ octahedra and SiO₄ tetrahedra and forming condensed [Si₂O₇] pyrogroups by connection. The sodium ions and water molecules are placed in channels set up between the layers. The stoichiometric and structural similarities of the studied phase with anhydrous compounds having general chemical formula A₂₍₃₎MT₂O₇ (A = Na,K; M = Zr,Lu,Sc; T = Si,Ge) are discussed. The topological relationship of their structures is interpreted in the light of spatial combination of silicon and zirconium polyhedra as basic building units into larger composite building units and their three-dimensional arrangement.     

Evaluation of tungsten–rhodium coating on an integrated platform as a permanent chemical modifier for cadmium,lead, and selenium determination by electrothermal atomic absorption spectrometry

A tungsten–rhodium coating on the integrated platform of a transversely heated graphite atomizer is proposed as a permanent chemical modifier for the determination of Cd, Pb, and Se by electrothermal atomic absorption spectrometry. It was demonstrated that coating with 250 μg W+200 μg Rh is as efficient as the conventional Mg(NO₃)₂+NH₄H₂PO₄ or Pd+Mg(NO₃)₂ modifiers for avoiding most serious interferences. The permanent W–Rh modifier remains stable for 300–350 firings of the furnace, and increases tube lifetime by 50%–100% when compared to pyrolytic carbon integrated platforms. Also, there is less degradation of sensitivity during the atomizer lifetime when compared with the conventional modifiers, resulting in a decreased need of re-calibration during routine analysis. The characteristic masses and detection limits achieved using the permanent modifier were respectively: Cd 1.1±0.4 pg and 0.020 μgL⁻¹; Pb 30±3 pg and 0.58 μgL⁻¹ and Se 42±5 pg and 0.64μgL⁻¹. Results from the determination of these elements in water reference materials were in agreement with the certified values, since no statistical differences were found by the paired t-test at the 95% level.