Search

Fine Co(OH)2 powder was prepared by simple precipitation from aqueous solutions of cobalt sulfate and sodium hydroxide without using sophisticated reagents and/or approaches. The fine powder was homogeneously mixed with protonated betaine bis((trifluoromethyl)sulfonyl)amide ionic liquid ([Hbet][TFSA] IL), an amide-type hydrophobic protic IL, and then dispersed in ethanol with graphene nanopowder for being spin-coated upon screen-printed carbon electrode (SPCE) to prepare the glucose-reactive electrode. Activation of the electrode was essential to expose the glucose-oxidation activity, and the experimental evidences indicated that Co3O4 converted from Co(OH)2 during the activation process was the active species in charge of glucose oxidation. The electrode showed a wide linear dynamic range for glucose from 1 to 1757 µM with a high sensitivity of 632 µA cm− 2 mM− 1 and a detection limit of 1 µM in the electrolyte containing 0.5 M NaOH and 0.1 M NaCl. The electrode showed no response to common interferants, including alcohols, in the concentration the same as to glucose. However, ascorbic acid in the same concentration level showed severe interference but negligible in the physiological level. This study shows that Co(OH)2 prepared by facile precipitation is qualified of being an efficient electrocatalyst precursor for glucose oxidation, and IL is a good binder for immobilizing the electrocatalyst. [ABSTRACT FROM AUTHOR]

Commercially available micro‐sized CuO powder was dispersed in the mixture of ethanol and protonated betaine bis((trifluoromethyl)sulfonyl)amide ([Hbet][TFSA]), a hydrophobic amide‐type protic ionic liquid (IL), to prepare a composite paste for the modification of screen‐printed carbon electrode (SPCE) via spin‐coating. The fabricated SPCE\CuO−IL composite‐based electrode showed a comparable activity as that of the nanonized metal‐oxide based electrodes towards the electrochemical oxidation of glucose in alkaline solutions. Hydrodynamic chronoamperometry tests performed at +0.55 V showed a linear dynamic response of the electrode over the concentration range of 1 μM–2.8 mM with a sensor‐sensitivity of 0.16 μA μM−1 in 0.1 M NaOH. The data also showed a linear dynamic response over the concentration range of 1 μM–4.6 mM with a sensor‐sensitivity of 0.10 μA μM−1 in 0.1 M NaOH with 0.1 M NaCl, indicating that the major interferant Cl− had negligible effects on glucose detection. Ascorbic acid (AA) (in the physiological level) and ethanol also did not interfere with the detection. Detection of glucose in real samples showed the recovery ratios higher than 95 %. This study has clearly demonstrated that commercial CuO powder without nanostructure can provide sufficient reactivity to the electrocatalytic oxidation of glucose by using IL as the organic binder. Facile preparation of the micro‐sized metal oxide‐modified electrodes can be accordingly pursued. [ABSTRACT FROM AUTHOR]

Abstract: The voltammetric behavior of cuprous ions has been studied at disk electrodes of glassy carbon and polycrystalline platinum in a new hydrophilic 1-butyl-3-methylimidazolium salicylate ionic liquid (BMI-SAL IL). Cuprous ions Cu(I) were introduced into the IL by the anodic dissolution of a Cu wire electrode or by the addition of CuCl. This air- and water-stable hydrophilic IL is very similar to dicyanamide (DCA)-based ILs because both DCA anions and salicylate (SAL) anions have very strong ligand properties; therefore, many metal salts, such as metal halides, are very soluble in this IL. However, the source of SAL anions, sodium salicylate, is considerably cheaper than sodium dicyanamide salt. The potentiostatic electrodeposition of copper onto iron substrates has also been investigated in this study. The surface morphologies of the copper deposits were significantly altered by the electrodeposition potential; granular, mirror-like, and porous copper deposits could be obtained at different negative potentials. The activity of the copper deposit-modified iron electrodes toward the electrochemical nitrate reduction in alkaline solutions was found to significantly depend on the surface morphologies. The granular and the porous surfaces showed better activities. The mirror-like surface, however, had no activity on the electrochemical nitrate reduction. [Copyright &y& Elsevier]

A new triazine-derived cupric complex has been synthesized, and characterized to realize its spectroscopic and electrochemical properties. By introducing a side chain with amino-terminal, this complex can be immobilized onto carbon electrodes via the formation of a carbon-nitrogen bond using electrografting. The modified electrode showed electrocatalytic activity towards H 2 O 2 reduction, and a better stability than the carbon ionic liquid electrode (CILE). A Fenton-like mechanism is involved in the H 2 O 2 reduction, inducing the hydroxylation of coumarin to be hydroxycoumarin. This electrode shows the potential to be a H 2 O 2 sensor and a hydroxylation electrode. [ABSTRACT FROM AUTHOR]

Abstract Two electropolymerizable carbazole-functionalized viologen compounds were synthesized and characterized using NMR, ESI-MS, voltammetry, and spectroelectrochemistry. The compounds were electropolymerized onto indium tin oxide electrode and glassy carbon electrode through a radical-induced polymerization triggered by electrochemical oxidation at the carbazole moieties in electrolytes composed of room temperature ionic liquid/organic solvents or NaClO 4 /acetonitrile. It was found that the properties of the electropolymerized polymers were crucially controlled by the chemical structure of the monomer and the electrolyte compositions. The polymer films showed electrochromic behavior, and the color changed from greenish at the potential where carbazole groups were oxidized to violet or colorless at which reduction of viologen groups occurred; violet or colorless depended on which of the two reductive states of the viologen moieties was reached. The polymer films were capable of enhancing the oxidative current of uric acid and ascorbic acid, respectively, in neutral media, which might be due to the concentrating ability of the viologen moieties towards negatively charged species such as ferricyanide ([Fe(CN) 6 ]3−) and ferrocyanide ([Fe(CN) 6 ]2−). Graphical abstract Unlabelled Image Highlights • Carbazole substituted viologen was prepared as electropolymerizable monomers. • Monomers with mono- or di-carbazole groups were prepared. • Single-backbone or two-backbone conducting polymers could be formed. • Not only the monomer structures but the electrolytes control the polymer properties. • The polymers show the electrochromic and anion-adsorptive behavior. [ABSTRACT FROM AUTHOR]

In spite of high mean transfer number and catalytic ability of the oxygen reduction reaction (ORR), α-MnO 2 is lack of electric conductivity and specific surface area to fully exert the performance of rechargeable Zn-air battery. Here, carbons in various forms are chosen as substrates for uniform dispersion of α-MnO 2 to form air electrode catalysts to evaluate the influences of carbon types on the catalytic activities of the ORR and OER (oxygen evolution reaction). The morphology and physicochemical properties of various α−MnO 2 /carbon composites are characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). Electrochemical studies include rotating ring-disk electrode (RRDE) voltammetry of catalysts, linear sweep voltammetry (LSV) of air electrodes, and the charge-discharge-cycling test of full cells. The discharge peak power density of Zn-air batteries varies from 66.3 (α−MnO 2 /carbon nanotubes with diameter ≈10 nm, denoted as α−MnO 2 /CNT10) to 40.5 mW cm −2 (α−MnO 2 /super fine mesophase graphite powder) in 6 M KOH under ambient condition. The rechargeable Zn-air battery with the air electrode containing α−MnO 2 /CNT10 is stably operated for 100 cycles at 10 mA cm −2 , which shows that an increase in 0.09 V between charge (decayed ca. 0.05 V) and discharge (decayed ca. 0.04 V) cell voltages. [ABSTRACT FROM AUTHOR]

Free sulfide anion (S 2− ) in alkaline media was determined using cathodic stripping voltammetry (CSV) and a graphene oxide-modified screen-printed carbon electrode (SPCE/GO) electrodeposited with Ag, Au, or AuAg nanoparticles (NPs). Electrodeposition was achieved using cyclic voltammetry in dilute sulfuric acid containing AgNO 3 and/or HAuCl 4 ·4H 2 O in which thiourea was essential for stabilizing Ag + . The existence of GO resulted in higher density and more uniform distribution of NPs, compared with those electrodeposited on bare SPCE. The composite electrode SPCE/GO/AgNPs showed the greatest sensitivity but poorest reproducibility. The SPCE/GO/AuNPs, in contrast, showed the best reproducibility with a linear dynamic range of S 2− from 6.25 to 400 μM and no significant interference from various inorganic anions and cations. EDTA, however, was essential to eliminate the interfering effects from metal cations. By co-depositing Au and Ag to form SPCE/GO/AuAgNPs, the sensitivity was significantly improved in contrast to SPCE/GO/AuNPs, and the reproducibility was approximately reserved. By using differential-pulse CSV (DPCSV), a linear dynamic range of 0.05∼1.5 μM was observed. A wider but two-segmented dynamic range, 0.5∼12.5 and 12.5∼312.5 μM, was obtained by using liner-scan CSV (LSCSV). SPCE/GO/AuAgNPs, however, showed a poorer resistance against metal cationic interferents, compared with SPCE/GO/AuNPs, although EDTA was used. This study reveals a facile approach of preparing sensitive modified electrodes for the determination of S 2− in alkaline aqueous media. [ABSTRACT FROM AUTHOR]

In this study, a new non-heme iron complex was prepared by mixing FeCl 3 ∙6H 2 O and 2,4,6-tris(2-pyridylmethylamino)-1,3,5-triazine (TPMATA) in ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (IL [BMP + ][TFSA − ]). The iron complex (TPMATA-FeCl 3 ) was used as a modifier for preparing the TPMATA-FeCl 3 -modified carbon ionic liquid electrode (TPMATA-FeCl 3 /CILE). H 2 O 2 was electrocatalytically reduced at the TPMATA-FeCl 3 /CILE in neutral aqueous solutions via Fenton's mechanism in which hydroxyl radical, •OH, was produced, and the radical was detected by using a fluorescence probe. This electrode showed a sensitivity of 22.1 μA∙mM −1 and a dynamic range of 0.025∼4.69 mM with a regression coefficient R 2 of 0.993 (or 0.025∼0.765 mM, R 2 = 0.997, sensitivity = 27.6 μA∙mM −1 ). The detection limit was 0.0125 mM (S/N = 3). This electrode shows the potential to be used as an electrochemical H 2 O 2 sensor or for the production of hydroxyl radicals. [ABSTRACT FROM AUTHOR]