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Polypyrrole-sepiolite (PPy/SPL) nanofibers were prepared by in situ chemical oxidation polymerization in the presence of sepiolite. A PPy/SPL composite modified glassy carbon electrode (PPy/SPL/GCE) was prepared and characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and electrochemical methods. Differential pulse anodic stripping voltammetry for the simultaneous determination of trace Pb(II) and Cd(II) was carried out at the PPy/SPL/GCE. Operational parameters such as the deposition potential and time, the amount of modified suspension, and the pH values were optimized for the purpose of determination of trace metal ions in 0.10 M acetate buffer solution. Under the optimal conditions, the stripping peak currents showed good linear relationships with Pb(II) and Cd(II) at concentration ranges of 5.0 x [10.sup.-9] - 1.2 x [10.sup.-6] M and 5.0 x [10.sup.-9] - 1.2 x [10.sup.-7] M, and the detection limits were 1.2 and 1.5 nM, respectively. The proposed method is applicable to the simultaneous determination of trace Pb(II) and Cd(II) in real water samples with the relative standard deviations of less than 4.4% and the recovery rates of 97.9-102.2%. Keywords: polypyrrole, sepiolite, differential pulse anodic stripping voltammetry, Pb(II), Cd(II), Lead and cadmium have long been recognized as harmful environmental pollutants, which can cause a variety of adverse health impacts even at lower levels [1-3]. Therefore, the selective and sensitive [...]

In order to improve the electrochemical behavior of graphitic carbon nitride (g-C3N4), ZnO nanoparticles were coupled with g-C3N4 nanosheets to form functional nanocomposite through hydrothermal method. The morphologies of nanocomposite were characterized by TEM and XRD. The results revealed that the addition of g-C3N4 can efficiently inhibit the growth of ZnO along the c-axis to obtain smaller size ZnO nanoparticles, which could bring the enhanced electrochemical response. Hydrogen peroxide was selected as a model to investigate the electrochemical behavior of nanocomposite in neutral condition. Compared with pure ZnO and g-C3N4 modified electrodes, the oxidation of H2O2 could be greatly enhanced at the ZnO/g-C3N4 modified electrode, revealing that the coupling of g-C3N4 with metal oxide could significantly improve its conductivity and electrochemical response. As a result, H2O2 could be sensitively detected at the modified electrode in the range of 5 μM to 0.2 mM. The proposed method could be successfully used in the detection of H2O2 in tap water samples with satisfactory results. [ABSTRACT FROM AUTHOR]

ABSTRACT Chemiluminescence (CL) of a cyclometallated iridium (III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium(III)} in the presence of potassium permanganate and oxalic acid is reported for the first time. Cysteine exhibits sufficient enhancing effect on the CL generated from the cyclometallated iridium(III) complex, which make it possible for the sensitive detection of cysteine using a flow-injection-chemiluminescence (FI-CL) method. The optimum conditions for the chemiluminescence emission were investigated. Under the optimal condition, the linear range for the determination of cysteine was 1.0 × 10-9-5.0 × 10-6 mol/L with a detection limit of 6.9 × 10-10 mol/L. A relative standard deviation of 1.6% was obtained for eight replicate determinations. The mechanisms of CL are proposed and the emitting species was identified as the metal-to-ligand charge-transfer (MLCT) excited states of the iridium complex. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT A novel chemiluminescence (CL) system, including the cyclometallated iridium(III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium}, potassium permanganate and oxalic acid, is proposed for the determination of benzenediols. This method is based on the fact that hydroquinone and catechol exhibited an inhibiting effect, while resorcinol exhibited an enhancing effect on CL intensity. The optimum conditions for CL emission were investigated. Under optimal conditions, the detection limits of hydroquinone, catechol and resorcinol were 6.4 × 10−8, 2.7 × 10−9 and 8.1 × 10−7 mol/L, respectively. The method has been successfully applied to the determination of benzenediols in different types of water sample. The luminophors of the CL systems were all identified as the metal-ligand charge-transfer (MLCT) excited state of the iridium complex. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Environmentally benign methods for gold recovery and detection are highly desirable for a sustainable future. Herein, we demonstrate a selective recovery and detection strategy of gold with cucurbit[ n ]urils (Q[ n = 5-7]) by means of outer-surface interactions. Tetrachloroaurate anion ([AuCl 4 ] - ) is able to be rapidly precipitated with Q[ n ] in forms of supramolecular adducts. X-ray crystallography of four Q[ n = 5-7]·[AuCl 4 ] - complexes reveal that strong outer-surface interactions between Q[ n = 5-7] and [AuCl 4 ] - are the major driving force for the formation of Q[ n = 5-7]·[AuCl 4 ] - complexes. Impressively, each Q[6] macrocycle is surrounded by 12 [AuCl 4 ] - anions. Each of these 12 [AuCl 4 ] - anions is connected to four adjacent [AuCl 4 ] - anions, leading to the formation of a three-dimensional supramolecular framework with tubular channels. In addition, we found an interesting inclusion complex [Au(OH 2 ) 4 ] 3+ ⊂Q[7] in the Q[7]·[AuCl 4 ] - complex, which is the first example of hydrated metal cation encapsulated inside the cavity of Q[ n ]. Spectroscopic data suggest that Q[ n = 5-7] possess a high affinity and selectivity for [AuCl 4 ] - even in the presence of other transition-metal ions. Q[ n ] modified electrodes are found to be an effective material for the detection of trace gold in dilute solutions.

Chemiluminescence (CL) of a cyclometallated iridium (III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium(III)} in the presence of potassium permanganate and oxalic acid is reported for the first time. Cysteine exhibits sufficient enhancing effect on the CL generated from the cyclometallated iridium(III) complex, which make it possible for the sensitive detection of cysteine using a flow-injection-chemiluminescence (FI-CL) method. The optimum conditions for the chemiluminescence emission were investigated. Under the optimal condition, the linear range for the determination of cysteine was 1.0 × 10(-9) -5.0 × 10(-6)  mol/L with a detection limit of 6.9 × 10(-10)  mol/L. A relative standard deviation of 1.6% was obtained for eight replicate determinations. The mechanisms of CL are proposed and the emitting species was identified as the metal-to-ligand charge-transfer (MLCT) excited states of the iridium complex., (Copyright © 2011 John Wiley & Sons, Ltd.)

A novel chemiluminescence (CL) system, including the cyclometallated iridium(III) complex {tris[1-(2,6-dimethylphenoxy)-4-(4-chlorophenyl)phthalazine]iridium}, potassium permanganate and oxalic acid, is proposed for the determination of benzenediols. This method is based on the fact that hydroquinone and catechol exhibited an inhibiting effect, while resorcinol exhibited an enhancing effect on CL intensity. The optimum conditions for CL emission were investigated. Under optimal conditions, the detection limits of hydroquinone, catechol and resorcinol were 6.4 × 10(-8), 2.7 × 10(-9) and 8.1 × 10(-7)  mol/L, respectively. The method has been successfully applied to the determination of benzenediols in different types of water sample. The luminophors of the CL systems were all identified as the metal-ligand charge-transfer (MLCT) excited state of the iridium complex., (Copyright © 2011 John Wiley & Sons, Ltd.)