Electrochemical immunoassay for CA125 based on cellulose acetate stabilized antigen/colloidal gold nanoparticles membrane

A novel separation-free electrochemical immunosensor for carcinoma antigen-125 (CA125) was proposed based on the immobilization of CA125 antigen on colloidal gold nanoparticles that was stabilized with cellulose acetate membrane on a glassy carbon electrode. A competitive immunoassay format was employed to detect CA125 antigen with horseradish peroxidase (HRP) labeled CA125 antibody as tracer, o-phenylenediamine and hydrogen peroxide as enzyme substrates. After the immunosensor was incubated with a mixture of HRP labeled CA125 antibody and CA125 sample at 35 °C for 50 min, the amperometric response decreased with an increasing CA125 concentration in the sample solution. The decreased percentage of the electrocatalytic current was proportional to CA125 concentration ranging from 0 to 30 U ml⁻¹ with a detection limit of 1.73 U ml⁻¹ (S/N = 3). The proposed immunosensor showed good stability, acceptable accuracy, and would be applicable to clinical immunoassay of CA125.     

Ferromagnetic mixed tribridged dinuclear copper(II) complex [Cu2(OAc)2(OH)(dpa)2]PF6 · H2O (dpa = 2,2′-dipyridylamine): 3D superstructure based on hydrogen bond and π…π interaction

A new dinuclear complex [Cu₂(OAc)₂(OH)(dpa)₂] PF₆ · H₂O (1) is prepared and structurally and magneto-structurally characterized. The monocationic core contains one acetate in familiar bidentate η¹:η¹:μ₂-bridge and another in the rare monoatomic bridge along with one hydroxo intermediary. 1 packs through N–H…O and O–H…O hydrogen bonds and π…π interaction resulting a 3D supramolecular continuum and displays high-energy intraligand ¹(π − π^*) fluorescence and intraligand ³(π − π^*) phosphorescence in glassy solution.     

Enhanced mesoporosity and capacitance property of spherical carbon aerogel prepared by associating Mg(OH)2 with non-ionic surfactant

Non-ionic surfactant F127 (PEO₁₀₆–PPO₇₀–PEO₁₀₆) has been employed to enhance the mesoporosity of carbon aerogel (CA) for electric double layer capacitor application. Field emission scanning electron microscopy images exhibit that CA spheres prepared with F127 possess much coarser surface and smaller diameter. Furthermore, nitrogen sorption measurements show that the total pore volume of CA prepared with 0.6 wt.% F127 is 0.90 cm³ g⁻¹ and the ratio of its mesopore volume to the total pore volume (mesoporosity) could reach 86%. The specific capacitance of this CA electrode is approximately 130.8 F g⁻¹ in 4 M KOH, which is 45% higher than that of CA solely catalyzed by Mg(OH)₂. The high specific capacitance of the CA is believed to be associated with its enhanced mesoporosity as well as the high pore volume. It also performs well in the galvanostatic charge/discharge measurement for supercapacitor.     

Uptake of heavy metal ions from aqueous solution using Mg–Al layered double hydroxides intercalated with citrate, malate, and tartrate

Mg–Al layered double hydroxide (Mg–Al LDH) was modified with organic acid anions using a coprecipitation technique, and the uptake of heavy metal ions from aqueous solution by the Mg–Al LDH was studied. Citrate·Mg–Al LDH, malate·Mg–Al LDH, or tartrate·Mg–Al LDH, which had citrate³⁻ (C₆H₅O₇³⁻), malate²⁻ (C₄H₄O₅²⁻), or tartrate²⁻ (C₄H₄O₆²⁻) anions intercalated in the interlayer, was prepared by dropwise addition of a mixed aqueous solution of Mg(NO₃)₂ and Al(NO₃)₃ to a citrate, malate, or tartrate solution at a constant pH of 10.5. These Mg–Al LDHs were found to take up Cu²⁺ and Cd²⁺ rapidly from an aqueous solution at a constant pH of 5.0. This capacity was mainly attributable to the formation of the citrate–metal, malate–metal, and tartrate–metal complexes in the interlayers of the Mg–Al LDHs. The uptake of Cu²⁺ increased in the order malate·Mg–Al LDH < tartrate·Mg–Al LDH < citrate·Mg–Al LDH. The uptake of Cd²⁺ increased in the order malate·Mg–Al LDH < tartrate·Mg–Al LDH = citrate·Mg–Al LDH. These differences in Cu²⁺ and Cd²⁺ uptake were attributable to differences in the stabilities of the citrate–metal, malate–metal, and tartrate–metal complexes. These results indicate that citrate³⁻, malate²⁻, and tartrate²⁻ were adequately active as chelating agents in the interlayers of Mg–Al LDHs.     

Unique direct synthesis of cyanide-bridged Fe2Cu2 molecular squares by destruction of sodium nitroprusside

The one-pot reaction of copper powder, sodium nitroprusside, ammonium thiocyanate and 2,2′-bipyridine (bpy) in acetonitrile solution at ambient conditions of air and water yields the novel heterometallic [Fe₂Cu₂(bpy)₆(μ-CN)₄(NCS)₂]₂[Fe(CN)₅(NO)](NCS)₂·5H₂O complex 1, which has been structurally and magnetically characterized. The most prominent feature of this complex is the unique tetranuclear squares comprised [Cu(bpy)NCS]⁺ and [Fe(bpy)₂]²⁺ corners with CN edges. The CuCu and FeFe separations are 6.72 and 7.73 Å, respectively. The variable-temperature magnetic susceptibility study revealed that a very weak antiferromagnetic coupling is active between Cu(II) centers (J_CuCu = −0.37 cm⁻¹).     

Solvothermal synthesis of 1D and 2D cobalt(II) and nickel(II) coordination polymers with 2,5-dihydroxy-p-benzenediacetic acid

1D cobalt(II) and nickel(II) coordination polymers {[Co(dba)(H₂O)₄] · H₂O}_n (1) and {[Ni(dba)(H₂O)₄] · H₂O}_n (2) (H₂dba = 2,5-dihydroxy-p-benzenediacetic acid) were synthesized under low temperature solvothermal condition. When 4,4′-bipyridine (bpy) was introduced to the synthetic systems of 1 and 2, respectively, two novel 2D coordination polymers {[Co(dba)(bpy)] · 0.5H₂O}_n (3) and [Ni(dba)(bpy)(H₂O)₂]_n (4) with different structures were obtained. All of the compounds were characterized by elemental analysis, FT-IR, UV–Vis spectra and single crystal X-ray diffraction.     

Calcined tetrabutylammonium kaolinite and montmorillonite and adsorption of Fe(II), Co(II) and Ni(II) from solution

Kaolinite and montmorillonite were modified with tetrabutylammonium (TBA) bromide, followed by calcination. The structural changes were monitored with XRD, FTIR, surface area and cation exchange capacity measurements. The modified clay minerals were used for adsorption of Fe(III), Co(II) and Ni(II) ions from aqueous solution under different conditions of pH, time and temperature. The uptake of the metal ions took place by a second order kinetics. The modified montmorillonite had a higher adsorption capacity than the corresponding kaolinite. The Langmuir monolayer capacities for the modified kaolinite and montmorillonite were Fe(III): 9.3 mg g^− 1 and 22.6 mg g^− 1; Co(II): 9.0 mg g^− 1 and 22.3 mg g^− 1; and Ni(II): 8.4 mg g^− 1 and 19.7 mg g^− 1. The modified kaolinite interacted with Co(II) in an endothermic manner, but all the other interactions were exothermic. The decrease of the Gibbs energy in all the cases indicated spontaneous adsorption.     

Switching on the photochemical reactivity in heterodimetallic Os–Ru bipyridyl complexes containing a bis(bidentate) phosphine

For the first time the excited states of the RuP₂N₄ moiety belonging to a new heterodimetallic Os^II–Ru^II bipyridyl complex are successfully designed in order to introduce photochemical reactivity. This dramatic effect is achieved via the use of the sterically demanding bis(bidentate) phosphine cis, trans, cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb). Thus, the temperature dependence of the luminescence lifetimes ranging from 77 to 298 K for the novel homodimetallic species meso-(ΔΛ/ΛΔ)-[Os₂(dppcb)(bpy)₄](PF₆)₄ (1) and rac-(ΔΔ/ΛΛ)-[Os₂(dppcb)(bpy)₄](PF₆)₄ (2) clearly indicates that the d–d state responsible for photochemistry is not populated. By contrast, the analogous temperature dependence for the new heterodimetallic species ΔΛ/ΛΔ-[Os(bpy)₂(dppcb)Ru(bpy)₂](PF₆)₄ (3) and ΔΔ/ΛΛ-[Os(bpy)₂(dppcb)Ru(bpy)₂](PF₆)₄ (4) unequivocally shows that as a consequence of the population of the d–d state the photochemical reactivity is switched on. Since single crystal X-ray structure analyses are a major clue to the understanding of photophysical and photochemical properties, also the X-ray structures of 1–3 are given.     

Photodegradation of tetrahalobisphenol-A (X = Cl, Br) flame retardants and delineation of factors affecting the process

The photoassisted degradation (HPLC-UV absorption), dehalogenation (HPLC-IC) and mineralization (TOC decay) of the flame retardants tetrabromobisphenol-A (TBBPA) and tetrachlorobisphenol-A (TCBPA) were examined in UV-irradiated alkaline aqueous TiO₂ dispersions (pH 12), and for comparison the parent bisphenol-A (BPA, an endocrine disruptor) in pH 4–12 aqueous media to assess which factor impact most on the photodegradative process. Complete degradation (2.7–2.8 × 10⁻² min⁻¹) and dehalogenation (1.8 × 10⁻² min⁻¹) of TBBPA and TCBPA occurred within 2 h of UV irradiation, whereas only 45–60% mineralization (2.3–2.7 × 10⁻³ min⁻¹) was complete within 5 h for the flame retardants at pH 12 and ca. 80% for the parent BPA. Factors examined in the pH range 4–12 that impact the degradation of BPA were the point of zero charge of TiO₂ particles (pH_pzc; electrophoretic method), particle or aggregate sizes of TiO₂ (light scattering), and the relative number of OH radicals (as DMPO–OH adducts; ESR spectroscopy) produced in the UV-irradiated dispersion. Dynamics of BPA degradation (2.0–2.4 × 10⁻² min⁻¹) were pH-independent and independent of particle/aggregate size, but did correlate with the number of OH radicals, at least at pHs 4 to 8–9, after which the rates decreased somewhat at pH > 9 with decreasing adsorption owing to Coulombic repulsive forces between the very negative TiO₂ surface and the anionic forms of BPA (pK_as ca. 9.6–11.3), even though the number of OH radicals continued to increase at the higher pHs.     

Kinetics of Sn electrodeposition from Sn(II)–citrate solutions

The influence of solution chemistry on the electrodeposition of Sn from Sn(II)–citrate solutions is studied. The distribution of various Sn(II)–citrate complexes and citrate ligands is calculated and the results presented as speciation diagrams. At a SnCl₂·H₂O concentration of 0.22 mol/L and citrate concentration from 0.30 mol/L to 0.66 mol/L, SnH₃L⁺ (where L represents the tetravalent citrate ligand) is the main species at pH below about 1.2 and SnHL⁻ is the main species at pH above about 4. Polarization studies and reduction potential calculations show that the Sn(II)–citrate complexes have similar reduction potentials at a given solution composition and pH. However, the Sn(II)–citrate complexes become more difficult to reduce with higher total citrate concentration and higher solution pH. Nevertheless, SnHL⁻ which forms at higher pH is a favored Sn(II)–citrate complex for Sn electrodeposition due to better plated film morphology, likely as a result of its slower electroplating kinetics. Precipitates are formed from the Sn(II)–citrate solutions after adding hydrochloric acid (to lower the pH). Compositional and structural analyses indicate that the precipitates may have the formula Sn₂L.     

Electrodeposited amorphous iron(III) oxides as anodes for photoelectrolysis of water

Deposition of amorphous iron(III)-oxide films on a conducting glass substrate was achieved via a cathodic bias in a 0.1 M hydrated ammonium iron(II) sulfate ((NH₄)₂Fe(SO₄)₂·6H₂O) solution at −1.6 V versus Ag/AgCl. Analysis by X-ray absorption near edge structure confirmed the iron(III) feature of the amorphous films. The deposited films exhibited n-type semiconducting characteristics by showing photoresponses under an anodic bias. The Mott–Schottky method and cyclic voltammetry were employed to characterize the semiconducting properties of the deposited films, which included the band gap (2.2 eV), the potentials of the conduction and valence band edges and flat band (−0.6, +1.6 and −0.58 V versus Ag/AgCl at pH 7, respectively), and the donor density (1 × 10²²/cm³). The deposited iron(III)-oxide films were suitable to serve as an anode for water splitting under illumination.     

Ferromagnetic coupling in a novel dicyanamide-bridged dinuclear gadolinium(III) complex [Gd2(dca)4(OH)2 (NITpPy)4] (NITpPy = 4-pyridyl-nitronyl nitroxide radical)

The novel six-coordinated gadolinium(III) complex of formula [Gd₂(dca)₄(OH)₂(NITpPy)₄] (1) (dca = dicyanamide, NITpPy = 4-pyridyl-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-oxy-3-oxide) has been prepared and characterized by X-ray crystallography. Compound 1 is a dimer structure made up of double μ_1,5-dca-bridged gadolinium(III) ions and one terminal dca ligand; variable-temperature magnetic susceptibility measurements reveal the occurrence of a significant ferromagnetic interaction directly spin polarization through the NITpPy–Gd(III)–NITpPy pathway with J = 11.56 cm⁻¹.     

Factors influencing the hydration of layered double hydroxides (LDHs) and the appearance of an intermediate second staging phase

The hydration of layered double hydroxides (LDHs) was investigated by changing the interlayer anion species, the Mg/Al ratio of the LDH hosts and the relative humidity (RH). The anions were CO₃²⁻, Cl⁻, Br⁻, NO₃⁻, I⁻, SO₄²⁻, and ClO₄⁻ (listed in the order of ion size, small to large) and LDHs with Mg/Al = 1.90 (LDH2) and 2.91 (LDH3) were used. Their XRD profiles were measured by an XRD diffractometer while controlling the RH in the range 0–95% at 25 °C. Only I⁻, SO₄²⁻, and ClO₄⁻ LDH2s and SO₄²⁻ LDH3 showed a large step-wise basal-spacing expansion, 0.24–0.28 nm, under high RH conditions (> ca. 60%) probably due to the insertion of one water layer into the interlayer space. Such hydration occurred more favorably for the LDHs with larger anions and those with a higher layer charge (LDH2). Among them, I⁻ and ClO₄⁻ LDH2s exhibited the second staging – alternate stacking of hydrated (H) and non-hydrated (NH) interlayers – in the intermediate RH region.     

Influence of the preparation method on the structure–activity of cobalt oxide catalysts supported on alumina for complete benzene oxidation

In the present work we studied the influence of the methodology used for mounting Co(II) species on the γ-alumina surface on the physicochemical properties and the catalytic activity of the ‘cobalt oxide’/γ-alumina catalysts for complete oxidation of benzene.Three series of catalysts of varying Co content (up to 21 wt.% Co) were prepared using three preparation methods: pore volume impregnation (pvi), equilibrium deposition filtration (edf) and pore volume impregnation adding nitrilotriacetic acid (nta) in the impregnation solution. It was found that the catalytic activity for low, medium and high Co content follows, respectively, the orders, nta–pvi pvi edf, nta–pvi edf ≈ pvi and edf > nta–pvi > pvi.The catalysts prepared were characterized using various techniques (BET, UV–vis/DRS, XRD and XPS) at each step of the preparation procedure, namely after the Co(II) mounting on the support surface, after drying as well as after calcination. It was inferred that the most active sites are located on Co₃O₄-supported crystallites, loosely or moderately interacting with the γ-alumina surface. Two critical parameters, related with the method followed for mounting Co(II) species on the γ-alumina surface, control the characteristics of the supported phase and thus the amount and the size of the above-mentioned Co₃O₄ crystallites: the ratio ‘amount of Co(II) deposited in the impregnation step to that remaining in the liquid phase inside the pores precipitating thus in the drying step’ closely related with the ratio ‘amount of Co(II) in the deposited phase (isolated Co(II) surface inner sphere complexes and Co(II) surface precipitates)/amount of Co(II) in the precipitated phase formed in the drying step’ as well as the composition of the precipitated phase.The application of the pvi technique resulted to low values for the above ratios and thus to the formation of a rather unstable precipitated phase consisted mainly by Co(H₂O)₆²⁺·2NO₃⁻. Upon calcination it is transformed into loosely bounded Co₃O₄ crystallites of relatively big size. This is related with the low Co dispersion and thus with the low catalytic activity exhibited by these catalysts.The application of edf resulted to high values for the above-mentioned ratios. Therefore, the deposited phase is predominant. Upon calcination it is transformed to well (very well) dispersed cobalt phases strongly (too strongly) bounded with the support surface and thus reducible at high temperatures (non reducible up to 800 °C). Although these phases are responsible for the high Co dispersion achieved they do not contribute to the catalytic activity unless the deposited phase mainly comprises a Co(II) surface precipitate with relatively large number of layers as it is the case for the sample with the maximum Co content.The application of the nta–pvi technique resulted to very low values for the ratios mentioned above. This is because the [Co(II)–nta]⁻ and [Co(II)–2nta]⁴⁻ complexes, in which the Co(H₂O)₆²⁺ complex is completely transformed, are not practically adsorbed on the support surface. Therefore, in the nta–pvi catalysts a precipitated phase containing the [Co(II)–nta]⁻·NH₄⁺(or H⁺) and [Co(II)–2nta]⁴⁻·4NH₄⁺ (or 4H⁺) complex salts predominates. Upon calcination these are transformed into Co₃O₄ crystallites of small size, which are moderately interacting with the support surface. This is related with the relatively high Co dispersion, mainly that for the catalytically active species, and thus with high catalytic activity.     

Immobilization of horseradish peroxidase on self-assembled (3-mercaptopropyl)trimethoxysilane film: Characterization, direct electrochemistry, redox thermodynamics and biosensing

Highly organized (3-mercaptopropyl)trimethoxysilane (3-MPT) films have been prepared via self-assembled coupled with sol–gel linking technology. Horseradish peroxidase (HRP) is successfully immobilized onto the densely packed three-dimensional (3D) 3-MPT network and the direct electrochemistry of HRP is achieved without any electron mediators or promoters. Redox thermodynamics of HRP on the 3-MPT films, which is obtained from the temperature dependence of the reduction potential, suggests that the positive shift of redox potentials of HRP at the interface of 3-MPT originates from the solvent reorganization effects and conformational change of the polypeptide chain of HRP. Based on the direct electrochemistry and electrocatalytic ability of HRP, a sensitive third-generation amperometric H₂O₂ biosensor is developed with two linear dependence ranges of 5.0 × 10⁻⁷ to 1.0 × 10⁻⁴ and 1.0 × 10⁻⁴ to 2.0 × 10⁻² mol L⁻¹.     

Thin-film CoB catalyst templates for the hydrolysis of NaBH4 solution for hydrogen generation

Thin-film CoB alloy catalysts were prepared on Ni-foam substrates using electroless as well as electroplating techniques. Electroless plating was carried out using cobalt (II) sulfate as the source of Co²⁺, sodium succinate as the complexing agent, and dimethyamine borane as the source of boron as well as the reducing agent. Electroplating was carried out using cobalt (II) sulfate and cobalt (II) chloride as the sources of cobalt, and boric acid as the source of boron. The thin-film CoB/Ni-foam templates were characterized using ICP, XRD and SEM techniques. The normalized B content was in the range of 1.0–1.30 and 0.20–0.60 wt.% for electroless and electroplated templates, respectively. The B content is less than that required for stoichiometric alloy formation, which indicates the simultaneous deposition of the Co metal along with CoB alloy. An optimum condition of 0.100 M L⁻¹ each of cobalt (II) sulfate heptahydrate Co(SO₄)·7H₂O, sodium succinate (Na₂C₄H₄O₄) and dimethylamine borane (CH₃)₂NHBH₃, at 60 °C with the pH value of 4–5 and a plating time of 1 h was identified for the preparation of the catalyst templates by electroless plating. Where as, 0.125 M L⁻¹ each of cobalt (II) chloride hexahydrate (CoCl₂·6H₂O), Co(SO₄)·7H₂O, 0.125 M L⁻¹ of boric acid at the current density range of 160–320 mA cm⁻² and a temperature of 60 °C was identified as the optimum condition for the electroplating method. Maximum H₂ generation rates of 1.64 and 0.30 L min⁻¹ g⁻¹ of catalyst were obtained with electroless and electroplated thin-film CoB/Ni-foam templates, respectively. The suitability of the electroless plated CoB/Ni-foam catalyst template for extended duration of hydrogen generation from NaBH₄ was studied up to 60 h. Activation energies of 44.47 and 54.89 kJ mol⁻¹ were calculated for electroless and electroplated CoB/Ni-foam catalyst templates, respectively.     

The first P–N containing RuCl3NO complex: fac-[RuCl3(NO)(P–N)] (P–N = [o-(N,N-dimethylamino)phenyl]diphenylphosphine)

Complex fac-[RuCl₃(NO)(P–N)] was synthesized from [RuCl₃(H₂O)₂(NO)] in methanol solution under reflux. The orange solid obtained was characterized by NMR (³¹P{¹H}, ¹H, ¹³C) and, cyclic voltammetry, ESI-MS, IR, elemental analysis and X-ray diffraction structure determination. The ³¹P{¹H} reveals the presence of singlet at 36 ppm. IR N–O stretching as KBr pellets or CH₂Cl₂ solution presented 1866 cm⁻¹ and 1872 cm⁻¹, respectively.     

Synthesis, structural characterization and third-order non-linear optical property of new three-dimensional metal-organic polymer [Fe2(μ10-btc)0.5(μ2-ox)0.5(μ2-O)1.5]n

One new metal-organic polymer formulated as [Fe₂(μ₁₀-btc)_0.5(μ₂-ox)_0.5(μ₂-O)_1.5]_n 1 (btc = 1,2,4,5-benzenetetracarboxylate, pyramellitate; ox = oxalate) has been synthesized by low-temperature solid-state reaction and characterized by single-crystal X-ray diffraction, elemental analyses, TGA, IR spectra and UV–visible spectra. Complex 1 presents the first 3D coordination network structure constructed by bridging btc, ox and O mixed ligands. In 1, carboxyl groups of btc are all deprotonated and they have a new type of μ₁₀-btc coordination mode. The third-order non-linear optical (NLO) properties of the title compound 1 were also investigated and they exhibit the reverse saturable absorption and self-defocusing performance with modulus of the hyperpolarizability (γ) 5.98 × 10⁻³⁰ esu for 1 in a 7.45 × 10⁻⁴ mol dm⁻³ DMF solution.     

Synthesis, crystal structure and photophysical properties of a series of new neutral iridium(III) complexes with 2-phenylpyridine

A series of new neutral iridium(III) complexes containing strong-field ancillary ligands, [Ir(ppy)₂(PPh₃)L] (ppy = 2-phenylpyridine, PPh₃ = triphenylphosphine, L = NCS⁻, 1; , 2; NCO⁻, 3), have been synthesized and fully characterized by ¹H NMR, IR, ESI mass spectral and elemental analysis. The crystal structure of 1 has been determined by X-ray analysis. The photoluminescence (PL) spectra of 1–3 show emission maxima at 477, 489 and 485 nm, respectively, corresponding to blue light-emitting of 1 and blue-green light-emitting of 2 and 3. PL quantum yields (PLQYs) of 1–3 are 0.39, 0.13 and 0.43, respectively.     

A novel lamella 2D Ag(I) coordination polymer of graphite-like structure featuring short interlayer distance

The reaction of Ag₂O with a mixture of benzene-1,3,5-tricarboxylic acid (H₃BTC) and 2-aminopyrazine (APYZ) under the ammoniacal conditions gives rise to a novel metal–organic coordination polymer Ag₆(BTC)₂(APYZ)₆·9H₂O (1). The structure of 1 possesses a high ordered lamella 2D structure with an interesting graphite-like 6³ net which is comprised of Ag₄ and Ag₆ fused hexagonal rings respectively. 1 exhibits photoluminescence maximized at 416 nm upon 330 nm excitation at room temperature, which may be mainly ascribed to ligand-to-ligand charge transfer (LLCT). Semiconducting behavior was also measured at ambient temperature with σ values of 5.56 × 10⁻⁷ S cm⁻¹ based on the π–π stacking and Ag(I)–π interactions.