Ru(bpy)3-doped silica nanoparticle DNA probe for the electrogenerated chemiluminescence detection of DNA hybridization

A sensitive electrogenerated chemiluminescence (ECL) detection of DNA hybridization, based on tris(2,2′-bipyridyl)ruthenium(II)-doped silica nanoparticles (Ru(bpy)₃²⁺-doped SNPs) as DNA tags, is described. In this protocol, Ru(bpy)₃²⁺-doped SNPs was used for DNA labeling with trimethoxysilylpropydiethylenetriamine(DETA) and glutaraldehyde as linking agents. The Ru(bpy)₃²⁺-doped SNPs labeled DNA probe was hybridized with target DNA immobilized on the surface of polypyrrole (PPy) modified Pt electrode. The hybridization events were evaluated by ECL measurements and only the complementary sequence could form a double-stranded DNA (dsDNA) with DNA probe and give strong ECL signals. A three-base mismatch sequence and a non-complementary sequence had almost negligible responses. Due to the large number of Ru(bpy)₃²⁺ molecules inside SNPs, the assay allows detection at levels as low as 1.0 × 10⁻¹³ mol l⁻¹ of the target DNA. The intensity of ECL was linearly related to the concentration of the complementary sequence in the range of 2.0 × 10⁻¹³ to 2.0 × 10⁻⁹ mol l⁻¹.     

Hydroxyl radical-related electrogenerated chemiluminescence reaction for a ruthenium tris(2,2′)bipyridyl/co-reactants system at boron-doped diamond electrodes

An electrogenerated chemiluminescence (ECL) reaction of the Ru(bpy)₃²⁺ (2,2′-bipyridyl, bpy)/co-reactant system in the extremely high-potential region (over 2.6 V versus Ag/AgCl) was probed using a boron-doped diamond (BDD) electrode. At the BDD electrode, three ECL waves (1.25, 2.30 and 3.72 V) were observed in cyclic voltammograms for 20 mM ascorbic acid (AA). For the ECL peaks observed at 1.25 V corresponding to the oxidation potential for Ru(bpy)₃²⁺ (1.15 V), the light intensities and current densities were found to depend on the square root of the AA concentration. This suggests that AA oxidation, followed by the formation of the reducing radical that is necessary for generating the excited state of Ru(bpy)₃^2+* occurred through homogeneous electron-transfer between Ru(bpy)₃³⁺ and the AA species. However, for the ECL peaks at 2.30 V, the current densities and light intensities linearly increased with increasing AA concentration, suggesting that the reducing radical was formed through the direct oxidation at the electrode surface. The ECL reaction at 3.72 V was observed only at the BDD electrode and not at other electrodes. The onset potentials for the light intensity were approximately 2.6 V, independently of the type of the co-reactants (e.g. 2-propanol and AA). The peak potentials exhibited linear relation with the co-reactant concentration. In the analysis of the ECL intensity for various co-reactants (alcohols) that show different reactivity for the hydrogen abstraction reaction, the order of the light intensities at the peaks for alcohols was found to be consistent with that for the rate constants of the hydrogen abstraction reaction. These results indicate that the co-reactant radical was formed through the hydrogen abstraction reaction with the hydroxyl radical (HO) generated during the oxygen evolution reaction.     

Enhanced solid-state electrogenerated chemiluminescence of Au/CdS nanocomposite and its sensing to H2O2

Au nanoparticles (AuNPs) are good quenchers once they closely contact with luminophore. Here we reported a simple approach to obtain enhanced electrogenerated chemiluminescence (ECL) behavior based on Au/CdS nanocomposite films by adjusting the amount of AuNPs in the nanocomposite. The maximum enhancement factor of about 4 was obtained at an indium tin oxide (ITO) electrode in the presence of co-reactant H₂O₂. The mechanism of this enhancement was discussed in detail. The strong ECL emission from Au/CdS nanocomposites film was exploited to determine H₂O₂. The resulting ECL biosensors showed a linear response to the concentration of H₂O₂ ranging from 1.0 × 10⁻⁸ to 6.6 × 10⁻⁴ mol L⁻¹ with a detection limit of 5 nmol L⁻¹ (S/N = 3) and good stability and reproducibility.     

Characterization of electrochemiluminescence of tris(2,2′-bipyridine)ruthenium(II) with glyphosate as coreactant in aqueous solution

Glyphosate, a phosphorus-containing amino acid type herbicide was used as a coreactant for studying of electrochemiluminescence (ECL) reaction of tris(2,2′-bipyridyl)ruthenium(II) [Ru(bpy)₃²⁺] in an aqueous solution. In a phosphate buffer solution of pH 8, glyphosate itself was known to be electrochemically inactive at glassy carbon electrode, however, it participated in a homogeneous chemical reaction with the electrogenerated Ru(bpy)₃³⁺, and resulted in producing Ru(bpy)₃²⁺ species at the electrode surface. Kinetic and mechanistic information for the catalysis of glyphosate oxidation were evaluated by the steady-state voltammetric measurement with an ultramicroelectrode. The simulated cyclic voltammogram based on this mechanism was in good agreement with that obtained experimentally. ECL reaction of Ru(bpy)₃²⁺/glyphosate system was found to be strongly dependent on the media pH. In a pH region of 5-9, an ECL wave appeared at ca. +1.1 V vs. Ag/AgCl, which was caused by the generation of *Ru(bpy)₃²⁺ via a Ru(bpy)₃³⁺-mediated oxidation of glyphosate. When pH >10, a second ECL wave was observed at ca. +1.35 V vs. Ag/AgCl, which was believed to be associated with a reaction between Ru(bpy)₃³⁺ and the species from direct oxidation of GLYP at a GC electrode surface.     

Influence of nature, concentration and pH of buffer acid-base system on rate determining step of the electrochemiluminescence of Ru(bpy)3 with tertiary aliphatic amines

The electrogenerated chemiluminescence (ECL) of Ru(bpy)₃²⁺ (bpy = 2,2′-bipyridyl) with tertiary aliphatic amines as co-reactants, was theoretically and experimentally studied as a function of the pre-equilibria involved in the ammonium proton lost and in relation to the nature of the rate determining step. Transient potential steps were used with a 3-mm glassy carbon disk electrode or carbon fiber ultramicroelectrodes array to investigate emission behavior in a variety of aqueous solution types, containing phosphate, tartrate and phthalate acid-base systems at differing pH values. The emission of Ru(bpy)₃²⁺ resulting from the reaction with n-tripropylamine (TPrA), tri-isobutylamine (TisoBuA), n-tributylamine (TBuA), methyl-di-n-propylamine (MeDPrA) and triethylamine (TEtA) in varying acid-base media was interpreted on the basis of the quoted pre-equilibria, ammonium pK_a being known. The nature of the rate determining steps changes depending on pH. Above pH ≈ 5 the amine neutral radical formation is the rate determining step and, is independent of pH with rate constant close to 10³ s⁻¹; below pH ≈ 5 the rate determining step becomes the deprotonation of the ammonium ion, operated by different bases present in solution. Different amines in the same acid-base system showed analogous ECL behavior, conditioned by the chosen acid base system. A single amine in different acid-base systems showed different kinetic behaviors, due to the dissociation constants of the chosen buffers. The concentration of the acid-base system also played an important role and influenced emission intensity and shape. ECL emission were simulated by finite difference methods, implementing a previously proposed mechanism by including the relevant pre-equilibria. Simulation may also give estimates of the pK_a values of the ammonium ions. An ion pair formation between R₃N⁺ and the mostly charged species present in solution is hypothesized to explain the contradictory experimental results concerning the reaction mechanism of the proton lost of the radical cation.     

联吡啶钌体系电致化学发光测定精胺的研究

基于精胺对Ru（bpy）32＋电化学发光的显著增强效应,利用池内停流技术,建立了精胺的电化学发光测定法。本方法具有灵敏度高,线性范围宽和分析速度快的特点。在最优条件下,相对电化学发光值与精胺浓度在5×10-8~5×10-5mol/L范围内呈现良好的线性关系,对5×10-8mol/L浓度的精胺进行11次平行测定,其相对标准偏差为3.03%,检出限为2.31×10-8mol/L。     

Development of a membraneless ethanol/oxygen biofuel cell

Biofuel cells are similar to traditional fuel cells, except the metallic electrocatalyst is replaced with a biological electrocatalyst. This paper details the development of an enzymatic biofuel cell, which employs alcohol dehydrogenase to oxidize ethanol at the anode and bilirubin oxidase to reduce oxygen at the cathode. This ethanol/oxygen biofuel cell has an active lifetime of about 30 days and shows power densities of up to 0.46 mW/cm². The biocathode described in this paper is unique in that bilirubin oxidase is immobilized within a modified Nafion polymer that acts both to entrap and stabilize the enzyme, while also containing the redox mediator in concentrations large enough for self-exchange based conduction of electrons between the enzyme and the electrode. This biocathode is fuel tolerant, which leads to a unique fuel cell that employs both renewable catalysts and fuel, but does not require a separator membrane to separate anolyte from catholyte.     

Facile functionalization by π-stacking of macroscopic substrates made of vertically aligned carbon nanotubes: Tracing reactive groups by electrochemiluminescence

We report a simple, fast and reliable non-covalent route of functionalization of macroscopic carbon nanotubes (CNTs) surfaces based on the π-stacking of CNTs sidewall with fluorescein derivatives (i.e., amino- and isothiocyanate-). The electrochemiluminescent emission of Ru(bpy)₃²⁺ labels bearing –COOH and –NH₂ side groups coupled with colorimetric and XPS measurements allowed to estimate the quantity of –NH₂ and –NCS functions obtained. The evaluation of reactivity suggests that functionalized CNTs substrates, in particular those carrying –NCS groups, are suitable to covalently bind probe molecules such as proteins and oligonucleotides, thus opening up the possibility of future application in genomics and proteomics fields.     

Synergistic effects of doped Fe3+ and deposited Au on improving the photocatalytic activity of TiO2

Fe³⁺ doped together with Au deposited TiO₂ (Au/Fe³⁺–TiO₂) was successfully prepared, which shows excellent photocatalytic activity for degradation of methyl orange (MO) under both UV and visible light (λ > 420 nm) illumination. Fe³⁺ has been confirmed by EPR to substitute for Ti⁴⁺ in the TiO₂ lattice, and Au exists as Au⁰ on the surface of the photocatalyst indicated by the results of XRD. Fe³⁺ and Au have synergistic effects on improving the photocatalytic activity of TiO₂. A proposed mechanism concerning the synergistic effects is discussed to explain the improvement of the photocatalytic activities.     

Evaluation of electrolytes for redox flow battery applications

A number of redox systems have been investigated in this work with the aim of identifying electrolytes suitable for testing redox flow battery cell designs. The criteria for the selection of suitable systems were fast electrochemical kinetics and minimal cross-contamination of active electrolytes. Possible electrolyte systems were initially selected based on cyclic voltammetry data. Selected systems were then compared by charge/discharge experiments using a simple H-type cell. The all-vanadium electrolyte system has been developed as a commercial system and was used as the starting point in this study. The performance of the all-vanadium system was significantly better than an all-chromium system which has recently been reported. Some metal-organic and organic redox systems have been reported as possible systems for redox flow batteries, with cyclic voltammetry data suggesting that they could offer near reversible kinetics. However, Ru(acac)₃ in acetonitrile could only be charged efficiently to 9.5% of theoretical charge, after which irreversible side reactions occurred and [Fe(bpy)₃](ClO₄)₂ in acetonitrile was found to exhibit poor charge/discharge performance.     

Enhancement of Sm3+ emission by SnO2 nanocrystals in the silica matrix

Silica xerogels containing Sm³⁺ ions and SnO₂ nanocrystals were prepared in a sol–gel process. The image of transmission electron microscopy (TEM) shows that the SnO₂ nanocrystals are dispersed in the silica matrix. The X-ray diffraction (XRD) of the sample confirms the tetragonal phase of SnO₂. The xerogels containing SnO₂ nanocrystals and Sm³⁺ ions display the characteristic emission of Sm³⁺ ions (⁴G_5/2 → ⁶H _J (J = 5/2, 7/2, 9/2)) at the excitation of 335 nm which energy corresponds to the energy gap of the SnO₂ nanocrystals, while no emission of Sm³⁺ ions can be observed for the samples containing Sm³⁺ ions. The enhancement of the Sm³⁺ emission is probably due to the energy transfer from SnO₂ nanocrystals to Sm³⁺ ions.     

Functionalized magnetic core-shell Fe3O4@SiO2 nanoparticles as selectivity-enhanced chemosensor for Hg(II)

A colorimetric and ‘‘turn-on” fluorescent chemosensor Rho-Fe₃O₄@SiO₂ for Hg²⁺ in which N-(rhodamine-6G)lactam-ethylenediamine (Rho-en) is conjugated with the magnetic core-shell Fe₃O₄@SiO₂ NPs has been strategically designed and synthesized. The final product was characterized by X-ray power diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectra (FTIR) and UV-visible absorption and fluorescence emission. Fluorescence and UV-visible spectra results showed that the resultant multifunctional nanoparticles Rho-Fe₃O₄@SiO₂ exhibited selective ‘turn-on’ type fluorescent enhancements and distinct color changes with Hg²⁺. The selectivity of the Rho-Fe₃O₄@SiO₂ for Hg(II) ion is better than that of the Rho-en in the same conditions. In addition, the presence of magnetic Fe₃O₄ nanoparticles in the sensor Rho-Fe₃O₄@SiO₂ NPs would also facilitate the magnetic separation of the Hg(II)-Rho-Fe₃O₄@SiO₂ from the solution.     

Luminescent properties of a novel afterglow phosphor Sr3Al2O5Cl2:Eu,Ce

A series of Eu²⁺ and Ce³⁺ doped/co-doped Sr₃Al₂O₅Cl₂ afterglow phosphors that presented various bright colors were successfully synthesized via high temperature solid state reaction. The structure and luminescence properties of the obtained samples were characterized by X-ray powder diffraction (XRD), photoluminescence (PL) spectra and decay curves as well as the thermoluminescence (TL) glow curves. The XRD results showed that all the phase could be indexed to the orthorhombic structure with the space group P2₁2₁2₁. After being exposed to a 254 nm or 365 nm mercury lamp, blue/yellow-orange afterglow emissions with broad bands peaking around 620 nm/435 nm, which were ascribed to the characteristic 4f⁶5d–4f⁷/5d¹–4f¹ transitions of Eu²⁺/Ce³⁺, could be observed in phosphors of Sr₃Al₂O₅Cl₂:Eu²⁺/Sr₃Al₂O₅Cl₂:Ce³⁺, respectively. Because of the overlap spectral range between the Sr₃Al₂O₅Cl₂:Eu²⁺ and Sr₃Al₂O₅Cl₂:Ce³⁺ phosphors, the energy transfer (ET) from Ce³⁺ to Eu²⁺ occurred. The related ET process was discussed in detail. Moreover, the incorporation of Ce³⁺ could significantly prolong the afterglow duration of Sr₃Al₂O₅Cl₂:Eu²⁺ phosphor, which was due to the increase of trap concentration. Consequently, 6 h of the afterglow duration could be observed in Sr₃Al₂O₅Cl₂:1.0%Eu²⁺, 0.5%Ce³⁺ sample, exhibiting much longer than that of Sr₃Al₂O₅Cl₂: 1.0%Eu²⁺ (3 h). From the afterglow decay curves and the fitting results, the optimal concentration of Ce³⁺ for the enhanced afterglow property was experimentally determined to be 0.5%.     

Potentiometric SO2 gas sensor based on a thick film of Ca2+ ion conducting solid electrolyte

A planar miniaturized SO₂ sensor based upon a thick film of Ca²⁺ ion conductor-CaO·0.6MgO·6Al₂O₃ (CMA) with a Na₂SO₄ auxiliary electrode and a Pt/O₂ reference electrode was fabricated and tested. The thick film was fabricated by screen-printing CMA ink on an alumina substrate and then fired at 1823 K. The solid electrolyte was interfaced with a sodium sulphate auxiliary phase containing Pt paste and the sensor showed a good SO₂ response at 873–1073 K. The electromotive force (emf) values obtained were linearly dependent upon the logarithm values of SO₂ concentration in a range of 10–500 ppm. Both the electrodes were exposed to the same test gas thus eliminating the need to separate the electrode chambers.     

测试——聚乙烯亚胺改性磁性膨润土对Pb2+和Cu2+的吸附性能(测试稿件)

在磁性膨润土(MBent)表面接枝聚乙烯亚胺(PEI)制备了聚乙烯亚胺改性磁性膨润土(PEI/KH560/MBent),采用FTIR、VSM、XRD、TGA、EA、SEM和EDS对其进行了表征,考察了其对水溶液中Pb_²⁺和Cu_²⁺的吸附性能。结果表明,聚乙烯亚胺已成功接枝于磁性膨润土表面,并有效提高其对Pb_²⁺和Cu_²⁺吸附量；溶液初始pH对吸附量影响较大,随着pH的增大,吸附量增加。在pH=5,溶液初始质量浓度为300 mg/L,PEI/KH560/MBent对Pb_²⁺和Cu_²⁺吸附量分别为96.21和61.08 mg/g；吸附过程符合准二级动力学模型,吸附行为符合Langmuir吸附等温模型。热力学研究表明,吸附为自发吸热过程。经过5次循环利用后,其吸附容量仍保持初始的60%以上,表明PEI/KH560/MBent具有一定的重复利用性。     

Preparation of Au/TiO2 catalysts from Au(I)–thiosulfate complex and study of their photocatalytic activity for the degradation of methyl orange

Gold loaded on TiO₂ (Au/TiO₂) catalysts were prepared using Au(I)–thiosulfate complex (Au(S₂O₃)₂³⁻) as the gold precursor for the first time. The samples were characterized by UV–vis diffuse reflectance spectra, X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic absorption flame emission spectroscopy (AAS), and X-ray photoelectron spectroscopy (XPS) methods. Using Au(S₂O₃)₂³⁻ as gold precursor, ultra-fine gold nanoparticles with a highly disperse state can be successfully formed on the surface of TiO₂. The diameter of Au nanoparticles increases from 1.8 to 3.0 nm with increasing the nominal Au loading from 1% to 8%. The photocatalytic activity of Au/TiO₂ catalysts was evaluated from the analysis of the photodegradation of methyl orange (MO). With the similar Au loading, the catalysts prepared with Au(S₂O₃)₂³⁻ precursor exhibit higher photocatalytic activity for methyl orange degradation when compared with the Au/TiO₂ catalysts prepared with the methods of deposition–precipitation (DP) and impregnation (IMP). The preparation method has decisive influences on the morphology, size and number of Au nanoparticles loaded on the surface of TiO₂ and further affects the photocatalytic activity of the obtained catalysts.     

Development of growth cycle for antimony telluride film on Au (1 1 1) disk by electrochemical atomic layer epitaxy

Electrochemical deposition of Sb₂Te₃ thin film on Au (1 1 1) disk via the route of electrochemical atomic layer epitaxy (ECALE) is described in this paper. Electrochemical aspects of Te and Sb on Au, Te on Sb-covered Au, and Sb on Te-covered Au were studied by means of cyclic voltammetry and coulometry. The apparent variation of coverage for Te or Sb on hetero-covered substrate is explained by considering the thermodynamic process of compound formation. A steady ECALE deposition for Sb₂Te₃ compound could be attained after negatively adjusting the underpotential deposition (UPD) potentials of Sb and Te on Au in steps over the initial 40 cycles, and the potentials could be kept constant for the following deposition. A 200-cycle deposit, which was grown with the steady deposition potentials, was proved to be a single phase Sb₂Te₃ compound by X-ray diffraction analysis. The 2:3 stoichiometric ratio of the deposit was further verified by energy dispersive X-ray (EDX) quantitative analysis. The p-type semiconductive property was demonstrated by measurements of the Seebeck coefficient and the electrical resistivity with a value of 145 μV/K and 9.37 μΩm, respectively. The morphologies of deposits with various growth cycle numbers were observed with FE-SEM. The evolvement mechanism of the morphology was investigated. The results show that the morphology of deposit has changed after initial potential adjustment and numberless thin sheets appeared and grew uprightly during the continuous cycle process. Fourier transform infrared spectroscopy (FTIR) absorption measurements suggested a band gap of 0.26 eV in very good agreement with literature reports for Sb₂Te₃ single crystals.     

Key role of the anchoring PEI layer on the electrochemistry of redox proteins at carbon electrodes: Consequences on assemblies involving proteins and clay

The key role of positively charged anchoring films on the electroactivity of various bacterial proteins at a pyrolytic graphite electrode is discussed. Several iron-containing low redox potential proteins, either negatively charged or positively charged were considered. Using quartz crystal microgravimetry (QCM) and electrochemical techniques, it is demonstrated that electron transfer on these proteins can be inhibited or promoted essentially depending on the electrostatic interactions with the positive PEI layer. Consequences of this interaction on the electroactivity of proteins involved in assemblies with clays are discussed. In particular, although bacterial polyhemic cytochrome c₃ is able to form stable LBL assemblies with intercalated clay layers, electroactivity of the so-mounted construction is highly dependant on the structure of the anchoring layer.     

Characteristics and reactivities of Ca(OH)2/silica fume sorbents for low-temperature flue gas desulfurization

Ca(OH)₂/silica fume sorbents were prepared with various Ca(OH)₂/silica fume weight ratios and slurrying times at 65°C and a water/solid ratio of 10/1. Dry sorbents prepared were characterized, and their reactivities toward SO₂ were measured in a differential fixed-bed reactor at the conditions similar to those in the bag filters in the dry and semidry flue gas desulfurization (FGD) processes. The reaction between Ca(OH)₂ and silica fume in the slurry was very fast. The formation of calcium silicate hydrates, which were mainly C-S-H(I), resulted in sorbent particles with a highly porous structure that seemed compressible under high pressures. The sorbents were mesoporous, and their specific surface areas and pore volumes were much larger than those of Ca(OH)₂ alone. The utilization of Ca of sorbent increased with increasing silica fume content mainly due to the increase in the specific surface area of sorbent. The sorbent with Ca(OH)₂ had the maximum SO₂ capture. Sorbents with Ca(OH)₂ contents less than and greater than would have a SO₂ capture greater than that of Ca(OH)₂ alone. Both the utilization of Ca and SO₂ capture per unit specific surface area of sorbent decreased in general with increasing specific surface area. At the same Ca(OH)₂ content, the utilization of Ca or SO₂ capture of the Ca(OH)₂/silica fume sorbent was greater than that of the Ca(OH)₂/fly ash sorbent; however, the amount of SO₂ captured per unit surface area of the former sorbent was smaller than that of the latter sorbent. The results of this study are useful to the preparation of silica-enhanced sorbents for use in the dry and semidry FGD processes.