Electrogenerated chemiluminescence of poly[(2,2′-bipyridyl)(4-(2-pyrrol-1-ylethyl)-4′-methyl-2,2′-bipyridyl)2]ruthenium (II) film

Elelctrogenerated chemiluminescence (ECL) of electropolymerized films based on [(2,2′-bipyridyl)(4-(2-pyrrol-1-ylethyl)-4′-methyl-2,2′-bipyridyl)₂]ruthenium (II) was firstly investigated in both organic and aqueous solution. The ECL behaviors have been explained by two typical mechanisms, namely, redox-cycling type and oxidative-reduction type. For the former, no co-reactant was required and for the latter, tripropylamine (TPA) and (NH₄)₂C₂O₄ were selected as co-reactants in the organic and aqueous system, respectively.     

Photocatalytic activity of sea water using TiO₂ catalyst under solar light

Wastewater is generally released into the rivers and streams in developing countries. Industrial wastewater usually contains highly toxic pollutants, cyanides, chlorinated compounds. Ultraviolet (UV) radiation from sunlight also decomposes organic compounds by oxidation process. However, the process is less effective due to large amount of toxic effluent entering in the main stream of water. The solar radiation can effectively be applied to accelerate the process by using suitable catalyst for economically cleaning the water sources. This paper describes the photocatalytic degradation of the sea water using novel approach of photoelectrochemical (PEC) reactor module consisting of nine photoelectrochemical cells equipped with spray deposited TiO? catalysts under solar light. The resulted water samples were studied for physicochemical and bacteriological analysis. The complete mineralization of degraded sample was confirmed by total organic carbon (TOC) analysis, COD measurement and estimation of the formation of inorganic ions such as NH?(+), NO??, Cl? and SO2??. Microbiological examinations are performed to determine the bacterial analysis. This implies that photoelectrocatalysis could be a promising way for improving water quality in developing countries with low cost and clean energy reliable resource.     

One-step fabrication of chitosan–hematite nanotubes composite film and its biosensing for hydrogen peroxide

This work reports on a novel chitosan–hematite nanotubes composite film on a gold foil by a simple one-step electrodeposition method. The hybrid chitosan–hematite nanotubes (Chi–HeNTs) film exhibits strong electrocatalytic reduction activity for H₂O₂. Interestingly, two electrocatalytic reduction peaks are observed at −0.24 and −0.56 V (vs SCE), respectively, one controlled by surface wave and the other controlled by diffusion process. The Chi–HeNTs/Au electrode shows a linear response to H₂O₂ concentration ranging from 1 × 10⁻⁶ to 1.6 × 10⁻⁵ mol L⁻¹ with a detection limit of 5 × 10⁻⁸ mol L⁻¹ and a sensitivity as high as 1859 μA μM⁻¹ cm⁻².     

Characterization of anti-reflective and self-cleaning SiO2–TiO2 composite film

Sol–gel dip-coating technique can be used to fabricate SiO₂–TiO₂ composite film with self-cleaning and anti-reflectance properties from low-cost SiO₂ colloid solution and Ti(OC₄H₉)₄. The physical and structural properties have been investigated by UV–visible spectrophotometer, contact angle meter, XRD, FT-IR, FESEM. UV–vis spectra and methyl orange photodegradation experiments showed that the SiO₂–TiO₂ composite film had high light transmittance and photocatalytic activity.     

Mechanism of synthesis of anatase TiO2 pigment from low concentration of titanyl sulfuric–chloric acid solution under hydrothermal hydrolysis

In order to investigate the influence of Cl⁻/SO₄²⁻ molar ratios and hydrolysis temperature on the hydrolysis process and TiO₂ pigment, H₂TiO₃ was prepared with a low concentration of titanyl sulfuric–chloric acid solution by hydrothermal hydrolysis. Under the optimal hydrolysis conditions, 1.5–2.2 μm of H₂TiO₃ samples were achieved. After doping and calcination, anatase TiO₂ pigments demonstrated excellent performance: the achromic ability of tinctorial strength (TCS) and blue phase index (SCX) were 1,429 and 4.07, respectively. As hydrolysis was a significant step in the process, the structure was simplified to a periodic structure of Ti[OH](H₂O)₃Cl(SO₄) to simulate the cluster structures. Based on experimental results and density functional theory (DFT) calculation, the hydrolysis mechanism was presumed to be a process of anionic (OH⁻, Cl⁻ and SO₄²⁻) competition reaction to explain the formation of anatase-type H₂TiO₃, and the crystal growth direction of H₂TiO₃ was also confirmed to be a (OA) and b (OB).     

Flow Injection Analysis of Histidine with Enhanced Electrogenerated Chemiluminescence of Luminol

Histidine is one of the necessary basic amino acids in biological bases, which often controls the catalytic activity of enzymes and acts in holding the higher structure of proteins. Furthermore, it is also an important ingredient in pharmaceutical preparations used for treatment of hetpatosis and nephropathy. Therefore, the determination of histidine in biological fluids and pharmaceutical preparations is of great importance. Various methods have been proposed for the detection of histidine …     

TEM study of interfacial relationships in the V2O5TiO2(anatase) system

A direct study of interfacial relationships in the V₂O₅TiO₂(anatase) system is carried out with specimens consisting of V₂O₅ nucleated from the vapor phase on commercial anatase crystallites. The anatase-supported V₂O₅ as opposed to pure V₂O₅ proved highly unstable under the electron beam and successive structural steps were observed. Consequently the characterization of the elusive V₂O₅TiO₂ interface by electron microscopy was not possible in general. In a few specimens, however, there was evidence of interfacial coherence. The crystallographic fit leading to the coherence is believed to be responsible for the unstability observed. An earlier assumption relating the catalytic behavior of the V₂O₅TiO₂(anatase) system to a crystallographic fit is thus reinforced.     

Investigation of Chemiluminescence with Electrogenerated Reagents and Its Analytical Application

In this paper, studies on chemiluminescence (CL) systems with electrogenerated reagents, including BrO^-, ClO^-, Br2, [Cu-(HIO6)2]^5-, H2O2, Mn^3 , Co^3 and Ag^2 , are described.The analytical applications of the CL system with electrogenerated reagents are reviewed.     

Measurement of Concentration Distribution of Electrogenerated Etchant Using an Electrochemical Probe Technique

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Synthesis, characterization and activity in cyclohexene epoxidation of V2O5–TiO2 anatase xerogel

The system of V₂O₅?CTiO₂ catalysts with V₂O₅ contents from 5 to 20 wt% were prepared by the sol?Cgel route and calcined at 500?°C. The mixed oxide series presented the crystalline structure of TiO₂ anatase phase. BET analysis showed a medium surface area decreasing from 73 to 19?m² g^?1 when V₂O₅ content rose from 5 to 20 wt%. The results of pyridine adsorption followed by FT-IR indicate that the catalysts display identical surface acid densities, independently of the V₂O₅ content, and both Br?nsted and Lewis acid sites are present on their surfaces. The V₂O₅ system presents an activity and selectivity during the cyclohexene oxidation reaction. The presence of V₂O₅ increases the catalyst efficiency and leads to a selectivity change from cyclohexenol (blank test) to epoxide, with a maximum for 15 wt% V₂O₅. The conversion of cyclohexene was 46?% while the selectivity to epoxide was higher (75?%).     

Determination of diquat by flow injection–chemiluminescence

A simple, economic, sensitive and rapid method for the determination of the pesticide diquat was described. This new method was based on the coupling of flow injection analysis methodology and direct chemiluminescent detection; to the authors’ knowledge, this approach had not been used up to now with this pesticide. It was based on its oxidation with ferricyanide in alkaline medium; significant improvements in the analytical signal were achieved by using high temperatures and quinine as sensitiser. Its high throughput (144 h⁻¹), together with its low limit of detection (2 ng mL⁻¹), achieved without need of preconcentration steps, permitted the reliable quantification of diquat over the linear range of (0.01–0.6) μg mL⁻¹ in samples from different origins (river, tap, mineral and ground waters), even in the presence of a 40-fold concentration of paraquat, a pesticide commonly present in the commercial formulations of diquat. Figure Quartz luminometer cell     

Use of novel cardanol-porphyrin hybrids and their TiO₂-based composites for the photodegradation of 4-nitrophenol in water

Cardanol, a well known hazardous byproduct of the cashew industry, has been used as starting material for the synthesis of useful differently substituted "cardanol-based" porphyrins and their zinc(II), copper(II), cobalt(II) and Fe(III) complexes. Novel composites prepared by impregnation of polycrystalline TiO? powder with an opportune amount of "cardanol-based" porphyrins, which act as sensitizers for the improvement of the photo-catalytic activity of the bare TiO?, have been used in the photodegradation in water of 4-nitrophenol (4-NP), which is a toxic and bio-refractory pollutant, dangerous for ecosystems and human health.     

Application of sol–gel TiO2 film for an extended-gate H+ ion-sensitive field-effect transistor

In this study, a sol–gel TiO₂ thin film has been spin-coated on a commercial ITO glass substrate as the extended-gate field effect transistor (EGFET) for hydrogen ion sensing. The as-deposited films are further annealed at various temperatures (T_a) under ambient atmosphere. It is found that the bi-layer structure of TiO₂/ITO EGFET exhibits good linear sensitivity from pH 1 to 11. Anatase TiO₂ appeared as early as T_a = 200 °C and a brookite (121) diffraction evolved at T_a = 500 °C. No prominent influence on the surface fine structures could be found at higher T_a. Due to the reduction or disappearance of the surface hydroxyl groups on TiO₂, the sensitivities of the TiO₂/ITO pH-EGFET device are rapidly reduced. However, the influence of the conductivity decay for ITO substrates annealed at high T_a could not be excluded. A maximum sensitivity 61.44 mV/pH is achieved as T_a = 300 °C.The bi-layer structure of TiO₂/ITO exhibits better long-term stability than the traditional ITO sensing membranes. In addition, the asymmetric hysteresis is more significant in alkaline buffer solutions, which could be explained by a site-binding model because the diffusion of H⁺ ions into the buried sites of the sensing film is more rapid than that of OH⁻ ions.     

Online phototransformation–flow injection chemiluminescence determination of triclosan

A highly selective and sensitive chemiluminescence method for the determination of triclosan is proposed. The method is based on the phototransformation of triclosan to a light-emitting precursor in the presence of fluorescein in alkaline medium and the chemiluminescence reaction is then triggered by strong base or oxidants such as N-bromosuccinimide. Based on this reaction an online phototransformation–flow injection manifold was developed, in which the photoreactor comprises a 150-cm-long × 0.8-mm-i.d. piece of PTFE tubing coiled around a 25-W fluorescent lamp, and the phototransformed products were then injected into a carrier stream of borate buffer. After mixing with the oxidant stream the produced light was detected by a photomultiplier. A wide calibration range from 8.0 × 10⁻⁸ to 1.0 × 10⁻⁴ mol L⁻¹ was obtained under the optimized conditions, and the detection limit was as low as 5.0 × 10⁻⁸ mol L⁻¹. The whole process of analysis, including the online phototransformation and subsequent chemiluminescence detection, could be completed in 6 min. Most of the foreign substances tested showed high tolerance levels, and the proposed method was directly applied to the determination of triclosan in toothpaste samples without any pre-separation procedure. Figure Schematic representation of the phototransformation of triclosan and subsequent chemiluminescence reaction     

Sensitive detection of luteolin based on poly(diallyldimethylammonium chloride)-functionalized graphene-carbon nanotubes hybrid/β-cyclodextrin composite film

Poly(diallyldimethylammonium chloride) (PDDA)-functionalized graphene sheets-multiwalled carbon nanotubes (G-CNTs) hybrid materials (PDDA-G-CNTs) were successfully synthesized. The materials were characterized by transmission electron microscopy (TEM) and Fourier transform infrared (FT-IR) spectra. Then, an electrochemical sensor based on PDDA-G-CNTs/β-cyclodextrin (PDDA-G-CNTs/β-CD) was fabricated for the sensitive determination of luteolin. In 0.2 M HAc–NaAc buffer solution (pH 5.0), the redox peak currents of luteolin increased significantly on PDDA-G-CNTs/β-CD modified glassy carbon electrode (GCE), suggesting that the composite film not only showed excellent electronic properties of PDDA-G-CNTs but also exhibited high molecular recognition capability of β-CD. The chronocoulometry investigation demonstrated that the composite could effectively increase the electrochemical active surface. Under the optimal conditions, the oxidation peak current of luteolin increased linearly with increasing the concentration in the range from 0.05 to 60 μM with the detection limit of 0.02 μM (S/N?=?3). The developed electrochemical sensor exhibited high selectivity, good stability and reproducibility, and also successfully determined luteolin in drug samples.     

Fabrication of an electrochemical immunosensor for α-fetoprotein based on a poly-L-lysine-single-walled carbon nanotubes/Prussian blue composite film interface

Single-walled carbon nanotubes functionalized with poly-L-lysine (PLL-SWCNTs) were successfully prepared and were used as a biocompatible platform to immobilize α-fetoprotein antibody (anti-AFP) which was labeled with horseradish peroxidase (HRP). Then, anti-AFP-HRP/PLL-SWCNT nanocomposites were coated onto a Prussian blue (PB) film-modified glassy carbon electrode surface. Glutaraldehyde was used to further stabilize the biosensing interface through a cross-linking step. All unspecific sites were blocked by bovine serum albumin to fabricate a novel electrochemical immunosensor for α-fetoprotein determination. The immunosensor was characterized by voltammetry and electrochemical impedance spectroscopy. Based on the catalytic current response of H₂O₂, the experimental conditions for α-fetoprotein determination were optimized. Under optimal conditions, the current response was linearly related to α-fetoprotein concentration in the range of 0.05～10.0 and 10.0～50.0 ng/mL with a detection limit of 0.011 ng/mL. The immunosensor was successfully used for the determination of α-fetoprotein in human blood plasma. The results were satisfied with that obtained with ELISA, demonstrating a good accuracy of the immunosensor.     

Ultrasonic-electrodeposition of gold–platinum alloy nanoparticles on multi-walled carbon nanotubes – ionic liquid composite film and their electrocatalysis towards the oxidation of nitrite

We report here for the first time on the electrochemical co-deposition of gold–platinum (AuPt) nanoparticles on multi-walled carbon nanotubes (MWNT) – ionic liquid (i.e. trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P_6,6,6,14][NTf₂]) composite surface in ultrasonic field. The obtained AuPt nanoparticles were characterized by scanning electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy. It was found that they were well-dispersed on the composite surface, with particle size about 10 nm. Furthermore, they exhibited alloy features. Electrochemical impedance spectroscopy and voltammetric experiments showed that the resulted AuPt-MWNT-[P_6,6,6,14][NTf₂] modified electrode possessed rather small electron transfer resistance and good catalytic activity towards nitrite oxidation. Under the optimized conditions, the oxidation current of nitrite was linear to its concentration in the range of 5–200 nM and the detection limit was down to 1.0 nM (S/N = 3).     

Preparation and characterization of crack-free sol–gel based SiO2–TiO2 hybrid nanoparticle film

Owing to the diverse potential applications of hybrid silica–titania thin films, the synthesis and characterization of these films have been carried out with a special focus on application as a medium index layer for multilayered functional coatings. For synthesis, tetraethylorthosilicate and titanium tetraisopropoxide were chosen as precursors for the formation of silica-titania hybrid thin films/nano-composites through an in situ sol–gel process. These films were sequentially obtained on Cu substrate utilizing spin coating. The hybrids were characterized by field emission scanning electron microscope, energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction, atomic force microscopy and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscope morphology displayed a smooth, densified and crack- free layer of silica-titania hybrid nanoparticles in the range of 20–71 nm after calcinations at low temperature of 300ºC for 1 h. X-ray diffraction pattern confirms the phases of titania with higher crystallinity and phase transformation at low temperature. The prepared films were uniform with low 8.852 nm RMS value. The stoichiometry of films was confirmed by EDX results. The FTIR spectroscopy indicated the establishment of heterogeneous chemical bonding between the Ti and Si surfaces through oxygen.