Enzyme electrodes stabilized by monolayer-modified nanoporous Au for biofuel cells

Open-cell nanoporous Au (np-Au) electrodes with pore size of approximately 40 nm were fabricated by dealloying of Au–Ag, and surfaces of the electrodes were modified with a self-assembled monolayer (SAM) of 4-aminothiophenol to enhance the electrocatalytic activities of immobilized laccase and glucose oxidase. Enzyme-immobilized SAM-modified np-Au working electrodes exhibited additional reduction–oxidation peak pairs in cyclic voltammograms in buffer solution (pH = 5.0). Thus, the SAM on the np-Au facilitated electron transfer between the electrode and reactants. First-principles calculations of perfect and defective Au (111) surfaces indicated that the atomic defects at nanoligament surface of np-Au are critically responsible for the electron transfer enhancement. For the utilization of these results, a glucose/O₂ biofuel cell composed of these enzyme-immobilized SAM-modified np-Au electrodes was preliminarily fabricated, and it exhibited a maximum power density of 52 μW/cm² at 20°C. Further optimization of nanoporous structures and kinds of SAM will improve the performance of biofuel cells.     

Multifunctional and Low-Density Inorganic Nanocomposites

We summarize our recent studies on the use of low-density nanoporous silica structures prepared through templating of a self-assembling disordered liquid-crystalline L ₃ phase, as a matrix for use in numerous applications, including sensing, optical data storage, drug release, and structural. The silica matrix exhibits low density (0.5 g cm⁻³ to 0.8 g cm⁻³ for monoliths, 0.6 g cm⁻³ to 0.99 g cm⁻³ for fibers) coupled with high surface areas (up 1400 m² g⁻¹) and void volumes (65% or higher). High-surface-area coatings are used to increase the sensitivity of mass-detecting quartz crystal microbalances to over 4000 times that of uncoated crystals. Monoliths, films, and fibers are produced using the templated silica gel. Once dried and converted to silica, the nanostructured material exhibits high fracture strength (up to 35 MPa in fibers) and Young’s modulus (30 GPa to 40 GPa in fibers). These values are, respectively, two orders of magnitude and twice those of nanostructured silicas having comparable densities.     

Di-(2-ethylhexyl) dithiophosphoric acid surface protected gold nanoparticles: micellar synthesis, stabilization, isolation, and properties

Gold nanoparticles (AuNPs) were synthesized in the organic solution by means of the reduction of HAuCl₄ by hydrazine in reverse micelles of oxyethylated surfactant Triton N-42, with decane as the dispersion medium. To isolate the powder of particles, the micelles were destroyed with chloroform in the presence of di-(2-ethylhexyl) dithiophosphoric acid as a surface protecting agent. According to the results of several experiments, the yield is within the limits of 90–98%, calculated for gold. The obtained preparations are dark blue hydrophobic powders containing aggregated but not agglomerated gold nanoparticles, as well as microcrystals (∼0.08–0.2 μm) of NaCl. The powders get re-dispersed in weakly polar organic solvents with the formation of colloidal solutions. The shape of the nanoparticles is spherical. Their nuclei are gold single crystals with a narrow size distribution; their diameter (d _Au) is about two times as large as the diameter of the aqueous nucleus (d _c) of initial micelles: d _Au = 7.7 ± 1.4 nm (d _c = 3.6 nm) and 8.8 ± 1.5 nm (4.6 nm). The preparations were studied by means of dynamic light scattering, atomic force microscopy, transmission electron microscopy, UV–vis spectroscopy, IR spectroscopy, X-ray powder diffraction, and thermogravimetric and elemental analyses. In the case of the particles with d _Au = 8.8 nm, the product is a mixture of AuNPs and the salt with the molar ratio Au/NaCl ≈ 1:4.54, while the gross composition of AuNPs per one gold atom is estimated as Au(C₁₆H₃₄O₂PS₂Na∙2N₂H₄)_0.16 with the number of gold atoms in one particle ∼21,000.     

Synthesis and antimicrobial activities of gold(I) sulfanylcarboxylates

Reaction of NaAuCl₄·H₂O and thiodiglycol (1:3 molar ratio) with 3-(aryl)-2-sulfanylpropenoic acids, H₂ xspa = [x:p = 3-phenyl-, f = 3-(2-furyl)-, t = 3-(2-thienyl)-, o-py = 3-(2-pyridyl)-, Clp = 3-(2-chlorophenyl)-, -o-mp = 3-(2-methoxyphenyl)-, -p-mp = 3-(4-methoxyphenyl)-, -o-hp = 3-(2-hydroxyphenyl)-, -p-hp = 3-(4-hydroxyphenyl)-, diBr-o-hp = 3-(3,5-dibromo-2-hydroxyphenyl)] and 2-cyclopentylidene-2-sulfanylacetic acid (H₂cpa) in a 1:1 metal/ligand molar ratio gave compounds of the type [Au(Hxspa)] or [Au(Hcpa)]. These compounds were reacted with diisopropylamine to afford [HQ][Au(xspa)] or [HQ][Au(cpa)] (HQ = diisopropylammonium) and with NaOH to afford Na[Au(xspa)]·H₂O and Na[Au(cpa)]·H₂O. All of the new compounds were isolated and characterised by IR and ¹H and ¹³C NMR spectroscopy. The antimicrobial activities of the complexes against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Candida albicans, Pseudomonas aeruginosa and carbapenem-resistant P. aeruginosa were evaluated and compared to those of the equivalent silver(I) complexes. The comparison shows that the gold compounds generally show better activity than the silver analogues against S. aureus and B. subtilis, but low sensitivity against E. coli, P. aeruginosa and C. albicans, suggesting a different mode of antimicrobial action for equivalent silver and gold compounds.     

Gold complexes with

The reactions of methane with the gold complexes [Au(OH)]⁻, [Au(OCH₃)₄]⁻, [Au(O(CO)₂O₂]⁻ and [Au(O₂CH)₂]⁺, [Au^I(acac)], [Au^III(acac)₂]⁺ (acac-acetylacetonato) were studied using the DFT/PBE method with the SBK basis set. High activation barriers were obtained for the electrophilic substitution in [Au(OH)]⁻, [Au(OCH₃)⁴]⁻, [Au(O(CO)₂O)₂]-and [Au^III(acac)₂]⁺ complexes, which excludes the possibility that these reactions might proceed under mild conditions. The reactions of the [Au(HCO₂)₂]⁺ and [AuI(acac)] complexes with methane have rather low energy barriers and proceed through the formation of an intermediate complex. The alternative mechanism of methane oxidation with a gold complex in the presence of oxygen is simulated.     

Electrochemical properties of carbon-coated LiFePO<Subscript>4</Subscript> and LiFe<Subscript>0.98</Subscript>Mn<Subscript>0.02</Subscript>PO<Subscript>4</Subscript> cathode materials synthesized by solid-state reaction

Olivine structured LiFePO4/C (lithium iron phosphate) and Mn2+-doped LiFe0. 98Mn0. 024/C powders were synthesized by the solid-state reaction. The effects of manganese partial substitution and different carbon content coating on the surface of LiFePO4 were considered. The structures and electrochemical properties of the samples were measured by X-ray diffraction (XRD), cyclic voltammetry (CV), charge/discharge tests at different current densities, and electrochemical impedance spectroscopy (EIS). The electrochemical properties of LiFePO4 cathodes with x wt. ％ carbon coating (x=3, 7, 11, 15) at γ=0. 2C, 2C (1C=170 mAh·g-1) between 2. 5 and 4. 3 V were investigated. The measured results mean that the LiFePO4 with 7 wt. ％ carbon coating shows the best rate performance. The discharge capacity of LiFe0. 98Mn0. 02PO4/C composite is found to be 165 mAh·g 1 at a discharge rate, γ=0. 2C, and 105 mAh·g-1 at γ=2C, respectively. After 10cycles, the discharge capacity has rarely fallen, while that of the pristine LiFePO4/C cathode is 150 mAh·g-1 and 98 mAh·g-1 at γ=0. 2 and 2C, respectively. Compared to the discharge capacities of both electrodes above, the evident improvement of the electrochemical performance is observed, which is ascribed to the enhancement of the electronic conductivity and diffusion kinetics by carbon coating and Mn2+-substitution.     

Effects of silicate concentration on anodic films formed on AZ91D magnesium alloy in solution containing silica sol

Anodic films were prepared on the AZ91D magnesium alloy in 1.0 M and 1.5 M Na₂SiO₃ with varied silica sol addition under the constant current density of 20 mA/cm² at 18 °C. The surface and cross-section morphologies of the anodic films were characterized by scanning electron microscopy (SEM) and energy dispersion spectrometry (EDS). The results showed that both the surface morphologies and the thickness of the anodic film were affected by the concentration of Na₂SiO₃ and the additions of silica sol. The effects of Na₂SiO₃ concentration and silica sol addition on the solution properties were also investigated. The results showed that the addition of silica sol into Na₂SiO₃ solution could decrease the surface energy and the conductivity of the solution. Moreover, the anodic film formed in 1.5 M Na₂SiO₃ with addition of silica sol was more uniform and compact than that formed in 1.0 M Na₂SiO₃ with addition of silica sol. And the electrochemical impedance spectroscopy (EIS) results also indicated that the anodic film formed in 1.5 M Na₂SiO₃ solution with 5 vol.% silica sol addition could provide higher corrosion resistance than that formed in 1.0 M Na₂SiO₃ with the same silica sol addition for the AZ91D Mg alloy substrate.     

A spectroscopic and electrochemical investigation of the oxidation pathway of glycyl-d,l-methionine and its N-acetyl derivative induced by gold(III)

The ¹H nuclear magnetic resonance spectroscopy was applied to study the reaction of the dipeptide glycyl-d,l-methionine (H-Gly-d,l-Met-OH) and its N-acetylated derivative (Ac-Gly-d,l-Met-OH) with hydrogen tetrachloridoaurate(III) (H[AuCl₄]). The corresponding peptide and [AuCl₄]^– were reacted in 1:1, 2:1, and 3:1 molar ratios, and all reactions were performed at pD 2.45 in 0.01 M DCl as solvent and at 25°C. It was found that the first step of these reactions is coordination of Au(III) to the thioether sulfur atom with formation of the gold(III)-peptide complex [AuCl₃(R-Gly-Met-OH-S)] (R=H or Ac). This intermediate gold(III) complex further reacts with an additional methionine residue to generate the R-Gly-Met-OH chlorosulfonium cation as the second intermediate product, which readily undergoes hydrolysis to give the corresponding sulfoxide. The oxidation of the methionine residue in the reaction between H-Gly-d,l-Met-OH and [AuCl₄]^– was five times faster (k ₂ = 0.363 ± 0.074 M^-1s^-1) in comparison to the same process with N-acetylated derivative of this peptide (k ₂ = 0.074 ± 0.007 M^-1s^-1). The difference in the oxidation rates between these two peptides can be attributed to the free terminal amino group of H-Gly-d,l-Met-OH dipeptide. The mechanism of this redox process is discussed and, for its clarification, the reaction of the H-Gly-d,l-Met-OH dipeptide with [AuCl₄]^– was additionally investigated by UV-Vis and cyclic voltammetry techniques. From these measurements, it was shown that the [AuCl₂]^– complex under these experimental conditions has a strong tendency to disproportionate, forming [AuCl₄]^– and metallic gold. This study contributes to a better understanding of the mechanism of the Au(III)-induced oxidation of methionine and methionine-containing peptides in relation to the severe toxicity of anti-arthritic and anticancer gold-based drugs.     

Oxidation Behavior of TiAl<Subscript>3</Subscript>/Al Composite Coating on Orthorhombic-Ti<Subscript>2</Subscript>AlNb Based Alloy at Different Temperatures

This paper reports the oxidation behavior of TiAl₃/Al composite coating deposited by cold spray. The substrate alloy was orthorhombic-Ti-22Al-26Nb (at.%). The oxidation kinetics of the coating was tested at 650, 800, and 950 °C, respectively. The parabolic rate constant for the coating oxidized at 650 °C was k _p = 7.2 × 10⁻² mg·cm⁻²·h^−1/2 for the tested 1200 h. For the coating oxidized at 800 °C, the oxidation kinetics could be separated into two stages with k _p value of 39.8 × 10⁻² mg·cm⁻²·h^−1/2 for the initial 910 h and 17.7 × 10⁻² mg·cm⁻²·h^−1/2 for the stage thereafter. For the coating oxidized at 950 °C, the oxidation kinetics can be separated into three stages with k _p of 136.9 × 10⁻² mg·cm⁻²·h^−1/2 in the first 100 h, followed by 26.9 × 10⁻² mg·cm⁻²·h^−1/2 from 100 to 310 h, and 11.8 × 10⁻² mg·cm⁻²·h^−1/2 from 310 to 1098 h. XRD, SEM, and EPMA were used to study the microstructure of the coating. The results indicated that the oxidation took place throughout the entire coating instead of only at the surface. The aluminum phase in the composite coating was soon oxidized to Al₂O₃ in all tested cases. The aluminum in TiAl₃ phase was depleted gradually and oxidized to Al₂O₃ along with the degradation of TiAl₃ to TiAl₂ and TiAl as the temperature increased and time proceeded. AlTi₂N was also a typical oxidation product at temperature higher than 800 °C. The experimental results also indicated that the protection of the coating was attributed greatly to the interlayer formed between the coating and the substrate.     

Thermal Expansion and Phase Stability Investigations on Cs-Substituted Nanocrystalline Calcium Hydroxyapatites

The high-temperature phase stability of Ca_10−x Cs _x (PO₄)₆(OH)₂, (x = 0–3) compositions synthesized by various wet chemical methods was investigated. The thermal expansion property of Ca₁₀(PO₄)₆(OH)₂ (abbreviated as CaHAp) and Cs-substituted CaHAp was measured by high-temperature XRD and dilatometry. The average crystallite size of the powders synthesized by wet chemical methods was found to be 10–50 nm range as shown by XRD and TEM. Up to 30 mol% Cs loading was observed to show only the apatite phase by XRD when the apatite powder was nanocrystalline in nature. However, high-temperature stability of the Cs-substituted system is limited to ≤5 mol%. Cs₃(PO₄) is observed to be separated out on heating the material above 773 K for compositions substituted with more than 5 mol% of Cs in the Ca-sublattice. The coefficient of thermal expansion measured by HTXRD is α_a = 12.42 × 10⁻⁶ K⁻¹, α_c = 14.98 × 10⁻⁶ K⁻¹; and α_a = 12.62 × 10⁻⁶ K⁻¹, α_c = 12.57 × 10⁻⁶ K⁻¹ for CaHAp and Ca_9.78Cs_0.2(PO₄)₆(OH)_1.96, respectively, in the temperature range of 298-1083 K. Bulk thermal expansion measurements are seen to be in agreement with the lattice expansion results.     

Growth of AlN Films and Its Process Development for the Fabrication of Acoustic Devices and Micromachined Structures

AlN films were grown on silicon substrates by RF reactive magnetron sputtering. At high sputtering powers, (002) preferred orientation as well as Al-N absorption band becomes prominent. The surface roughness and grain size of sputtered films were found to increase with RF power. Surface acoustic wave (SAW) device has been made on the grown (002) oriented piezoelectric AlN film with interdigital transducer (IDT) electrodes spacing corresponding to a wavelength of 60 μm. The centre frequency of the SAW filter was found to be 84.304 MHz, which gives a phase velocity of 5058 m/s with an electromechanical coupling coefficient (K ²) of 0.34%. Low etch rate of AlN films were observed in doped TMAH solution. Three-dimensional suspended Cr/AlN/Cr/SiO₂ microstructures were also fabricated by wet chemical etching.     

Preparation of photocatalytic TiO2−SiO2 thin film by sol-gel coating

TiO₂−SiO₂ composite thin films for photocatalysis were fabricated on window glass with sol-gel technology. By measuring the contact angle of the film surface and the degradation of methylene blue, the super-hydrophilicity and photocatalytic activity of the composite thin films were studied. The results indicate that the TiO₂−SiO₂ composite thin film can yield various glass self-cleaning effects with low maintenance expenses.     

CO<Subscript>2</Subscript> electrochemical reduction via adsorbed halide anions

The electrochemical reduction of CO₂ was studied utilizing halide ions as electrolytes, specifically, aqueous solutions of KCl, KBr, KI. Electrochemical experiments were carried out in a laboratory-made, divided H-type cell. The working electrode was a copper mesh, while the counter and reference electrodes were a Pt wire and an Ag/AgCl electrode, respectively. The results of our work suggest a reaction mechanism for the electrochemical reduction of CO₂ where the presence of Cu-X as the catalytic layer facilitates the electron transfer from the electrode to CO₂. Electron-transfer to CO₂ may occur via the X⁻ _ad(Br⁻, Cl⁻, I⁻)-C bond, which is formed by the electron flow from the specifically adsorbed halide anion to the vacant orbital of CO₂. The stronger the adsorption of the halide anion to the electrode, the more strongly CO₂ is restrained, resulting in higher CO₂ reduction current. Furthermore, it is suggested that specifically adsorbed halide anions could suppress the adsorption of protons; leading to a higher hydrogen overvoltage. These effects may synergistically mitigate the over potential necessary for CO₂ reduction, and thus increase the rate of electrochemical CO₂ reduction.     

Microstructure and Corrosion Resistance of Plasma Sprayed Fe-Based Alloy Coating as an Alternative to Hard Chromium

Fe-based alloy coating (FAC) was prepared from Fe-based amorphous metallic powders on low-carbon steel by plasma spray. The microstructures and corrosion resistances (salt spray and electrochemical tests) of the FAC and the reference hard chromium coatings (HCC) were investigated. The results indicated that the as-sprayed FAC consisted of amorphous phase, nanocrystalline grains, and borides. Both the FAC and HCC adhered well to the low-carbon steel substrate, but there are micro-cracks and pores located in FAC, which disappeared after the sealing treatment. After 60 days (1440 h) of corrosion tests by salt spray, the weight loss of FAC was about 10% of the HCC, but that of the sealed FAC (SFAC) was only about 4% of HCC. The electrochemical tests indicated that the HCC had the lowest E _corr (−629 mV) and highest I _corr (63.2 mA/m²). Correspondingly, the SFAC possessed the highest E _corr (−321 mV) and lowest I _corr (6.97 mA/m²). These suggested that the resistance to corrosion sequence (R) among these coatings was R _SFAC > R _FAC > R _HCC. Therefore, this Fe-based alloy coating could be applied as a good alternative material to hard chromium in corrosion environments.     

Investigation on Oxygen Chemical Diffusion Properties of Perovskite Oxides (La1?x Pr x )0.6Sr0.4Co0.8Fe0.2O3?δ

Perovskite oxide samples of (La_1−x Pr _x )_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ (x = 0.2, 0.4, 0.6, 0.8) are obtained by solid-state reaction method. The oxygen chemical diffusion properties of (La_1−x Pr _x )_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ are determined by electrical conductivity relaxation technique. The results show that the conductivity of (La_1−x Pr _x )_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ increases with the increase of oxygen partial pressure. The (La_1−x Pr _x )_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ samples have a high oxygen chemical diffusion coefficient, which decreases linearly with a decrease in temperature and an increase in Pr content. The oxygen chemical diffusion coefficient D _chem remains fairly constant at high PO₂. The oxygen chemical diffusion coefficient is the highest for (La_1−x Pr _x )_0.6Sr_0.4Co_0.8Fe_0.2O_3−δ with x = 0.2, and attains a value of 9.41 × 10⁻⁵ cm² s⁻¹ at 600 °C. This shows the material’s promise as a cathode material for intermediate temperature solid oxide fuel cells.     

Superplastic Behavior of Al-4.5Mg-0.46Mn-0.44Sc Alloy Sheet Produced by a Conventional Rolling Process

This article describes the superplastic behavior of the Al-4.5Mg-0.46Mn-0.44Sc alloy. The investigated alloy was produced by casting and was conventionally processed to form a sheet with a thickness of 1.9 mm and an average grain size of 11 μm. The superplastic properties of the alloy were investigated using a uniaxial tensile testing with a constant cross-head speed and with a constant strain rate in the range 1 × 10⁻⁴ to 5 × 10⁻² s⁻¹ at temperatures from 390 to 550 °C. The investigations included determinations of the true-stress, true-strain characteristics, the maximum elongations to failure, the strain-rate sensitivity index m, and the microstructure of the alloy. The m-values determined with the strain-rate jump test varied from 0.35 to 0.70 in the temperature interval from 390 to 550°C and strain rates up to 2 × 10⁻² s⁻¹. The m-values decreased with increased strain during pulling. The elongations to failure were in accordance with the m-values. They increased with the temperature and were over 1000%, up to 1 × 10⁻³ s⁻¹ at 480 °C and up to 1 × 10⁻² s⁻¹ at 550 °C. A maximum elongation of 1969% was achieved at an initial strain rate of 5 × 10⁻³ s⁻¹ and 550 °C. The results show that the addition of about 0.4 wt.% of Sc to the standard Al-Mg-Mn alloy, fabricated by a conventional manufacturing route, including hot and cold rolling with subsequent recrystallization annealing, results in good superplastic ductility.     

Corrosion behavior of mild steel in the presence of scale inhibitor in sulfuric acid solution

Surfactants such as non-ionic polyethylene glycol tert-octylphenyl ether (Triton X-114) have been studied as efficient corrosion inhibitors in acid medium. In this study inhibition performance of Triton X-114 has been evaluated as corrosion inhibitor for mild steel in 0.5 mol l⁻¹ H₂SO₄. The electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and linear polarization (LPR) techniques has been applied to determine the electrochemical behaviour of Triton X-114. The maximum efficiency of Triton X-114 was found as 96% at the concentration 5.0 × 10⁻⁵ mol l⁻¹. The adsorption isotherm of inhibitor on the mild steel surface was found to be in a good agreement with the Langmuir and the standard free energy value (ΔG _ads^°) was calculated as −50.1 kJ mol⁻¹, which shows that adsorption of Triton X-114 on the mild steel surface improves the inhibition characteristics in 0.5 M H₂SO₄.     

活性元素Ti和SiO2界面结合机制的第一性原理计算

Ti元素是钎焊SiO_2f/SiO₂复合材料重要的活性元素,因此,使用第一性原理计算研究了Ti和SiO₂的界面结合机制. 分别建立了两种不同的终止面和化学计量比的界面,使用界面分离功、电子行为和界面能研究了界面原子间的结合. 结果表明,在O终止界面中,界面处Ti和O形成很强的离子-共价键,界面分离功最大可达到8.99 J/m2. 在Si终止面界面中,Ti和Si形成共价-离子键,界面分离功为2.65 J/m2. 在温度为1 173 K时,当Si的活度大于e?35时,富Si界面的界面能更低,界面倾向于形成Ti-Si化合物. 当Si的活度小于e?35时,富O界面在热力学上更加稳定,界面倾向于形成Ti-O化合物. SiO₂中的Si被Ti置换出后,Si扩散进入钎料,活度升高,与钎料中的Ti反应生成Ti-Si化合物,所以界面结构为SiO₂/Ti-O化合物/Ti-Si化合物/钎料.     

Cyanide-bridged bimetallic multidimensional structures derived from organotin(IV) and dicyanoaurate building blocks: ion exchange, luminescence, and gas sorption properties

The recent success of using methyltin(IV) cations in constructing multidimensional structures containing the Au–CN–Sn link with interesting physical properties will be surveyed. The methyltin(IV)-dicyanoaurates, Me₃Sn[Au(CN)₂] (1) and Me₂Sn[Au(CN)₂]₂ (2) containing the Au–CN–Sn link can be easily prepared by aqueous reaction of Me₃SnCl or Me₂SnCl₂ with stoichiometric amounts of an aqueous solution of K[Au(CN)₂]. The room temperature solid-state emission spectrum of 1 excited at 254 nm shows two intense emission bands at 442 and 670 nm, and a shoulder at 390 nm. When excited at 320 nm, the crystalline sample shows two intense emission bands at 442 and 720 nm, and a shoulder at 380 nm. After 2 min of grinding, only the blue emission band at 442 nm is observed. In contrast, the emission spectrum of 2 shows only one emission maximum at 422 nm. The porosity of 1 and 2 was probed by gas sorption measurements performed at 77 K. 1 exhibited no detectable microporosity as revealed by the inspection of the N₂, H₂, as well as, O₂ isotherms. The gas adsorption studies reveal that only a small amount of N₂ and H₂ (3.82 and 4.66 cm³ g⁻¹, respectively) is adsorbed by the framework of 2 at 77 K. However, a CO uptake of 11.20 cm³ g⁻¹ can be reached at 1 atm. The framework of 2 can take up significant amounts of O₂ (23.27 cm³ g⁻¹). In addition to intriguing photoluminescence and gas sorption behavior, these complexes also exhibit ion exchange properties in the presence of bivalent transition metal cations, such as cobalt(II), nickel(II), copper(II), and zinc(II).     

Highly ordered self-organized TiO2 nanotube arrays prepared by a multi-step anodic oxidation process

Highly ordered TiO₂ nanotube arrays were prepared using a self-templating multi-step anodic oxidation process in a fluoride-containing electrolyte. The microstructures, chemical compositions, and phases of the self-organized TiO₂ nanotube arrays were analyzed by FESEM, XPS, and XRD, respectively. Hexagonal packing density in TiO₂ nanotube arrays significantly improved after the the multi-step anodic oxidation. The area densities of the hexagonal TiO₂ nanotube arrays increased approximately 3 times from the first to second step in the anodic oxidation steps process (4.9 μm⁻² to 16.4 μm⁻²), but there was no difference between the second and third step (16.4 μm⁻² to 16.0 μm⁻²). The as-anodized TiO₂ nanotube array had an amorphous structure and it transformed to an anatase phase during the annealing process at 450 °C for 1 h. The as-anodized TiO₂ nanotube arrays adsorbed the fluoride, hydrocarbon groups (CH), hydroxyl groups (OH, C-OH), and carboxyl groups (O = C-OH) on their surfaces.