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A facile alloy-dealloy technique performed in aqueous media was employed to prepare a nanoporous gold (NPG) electrode that demonstrated extremely high sensitivity toward hydrazine oxidation. An Ag(∼60)Au(∼40) alloy was electrodeposited at a constant potential on sequentially Cr- and Au-deposited indium tin oxide (Au/Cr/ITO) from a bath that contained sulfuric acid, thiourea, HAuCl(4)·3H(2)O, and AgNO(3). The dealloying step was performed in concentrated HNO(3), where Ag in the alloy was selectively oxidized to leave the NPG structure. The NPG electrode was employed to study the hydrazine oxidation in basic phosphate buffer solution (PBS), and the results were compared with those obtained using the gold nanoparticle (AuNP)-modified ITO (AuNP/ITO) electrode. The NPG electrode demonstrated an unusual surface-confined behavior, which probably resulted from the thin-layer characteristics of the nano-pores. Hydrazine was detected by hydrodynamic chronoamperometry (HCA) at +0.2V (vs. Ag/AgCl). The steady-state oxidative current exhibited a linear dependence on the hydrazine concentration in the concentration range of 5.00 nM-2.05 mM, and the detection limit was 4.37 nM (σ=3). This detection limit is the lower than the detection limits reported in the current literature concerning the electrochemical detection of hydrazine. The NPG electrode indeed demonstrates greater stability after hydrazine detection than the AuNP/ITO electrode., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Commercial CuNi (55/45 wt%) alloy can be electrochemically dealloyed to be the porous Cu‐rich CuNi electrodes, which reveals an enhanced catalytic activity toward nitrate reduction in contrast with that of the mother alloy electrodes. In comparison with the use of aqueous electrolytes, the formation of the porous structures is reproducible if ionic liquid (IL) is used as the electrolyte for the dealloying process. During the dealloying process, a relatively more quantity of Ni but both Ni and Cu were electrochemically oxidized to be Ni(II) and Cu(II) complex ions; different ions seemed to own different coordinating molecules in accordance with the NMR analysis. Cu(II) ions could be reduced to Cu metal and deposited upon the counter electrode during the dealloying process. Ni(II) ions, on the other hand, can be mostly removed from the IL phase by extraction into the immiscible water phase. A sustainable system may be developed for the preparation of nitrate‐active electrodes in accordance with the study shown here. [ABSTRACT FROM AUTHOR]

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]

A nanoporous gold wire electrode (NPGWE) was prepared using a published one-step method from a 0.3 M oxalic acid at room temperature. It was found in this study that the surface morphology, including the pore size and the width of the ligaments, and thus the surface roughness of the NPGWE could be easily manipulated by controlling the solution stirring rate. The NPGWE was used for the study of electrochemical oxidation and determination of glucose in 0.1 M NaOH using cyclic voltammetry. The effect of two potential interferences chloride ion and ascorbic acid was assessed. The electrode showed a linear range of glucose concentration from 0.5 mM to 10 mM with a detection limit of 8 μM. [ABSTRACT FROM AUTHOR]

Abstract: The voltammetric behavior of N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid (BMP-TFSI) containing Cu(I), Mn(II), or mixtures of Cu(I) and Mn(II) as well as the electrodeposition of copper–manganese alloy coatings (Cu–Mn alloy coatings) was studied at 323K. The Cu(I) and Mn(II) species required to prepare these coatings were introduced into the BMP-TFSI by anodic dissolution of the relevant metallic electrodes. Electrodeposits of Cu, Mn, and Cu–Mn with various contents of Mn can be obtained by controlled-potential electrolysis. It was found that the compositions and surface morphology of the electrodeposited Cu–Mn alloy coatings depend on the deposition potentials and the concentration ratio of [Cu(I)]/[Mn(II)] in BMP-TFSI. The Cu–Mn alloy coatings obtained in this study were compact and adherent. They did not show any significant X-ray diffraction signal that could be assigned to the crystalline structures of Cu, Mn, or Cu–Mn alloys. In the aqueous solution containing 0.1M NaCl, the Cu–Mn alloy coatings demonstrated passive behavior—no continuous oxidation was observed. However, a significant oxidation current was observed at the electrodes deposited with Cu or Mn. [Copyright &y& Elsevier]

Abstract: The electrochemistry of manganese was investigated at solid disk electrodes in the hydrophobic room-temperature ionic liquid butylmethylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide (BuMePy-TFSI) by using staircase cyclic voltammetry and chronoamperometry. The Mn(II) species was introduced into the ionic liquid by anodic dissolution of the metallic manganese electrode. The reduction of Mn(II) ions at tungsten and platinum electrodes accompanies with nucleation mechanism and the coupled oxidation wave encounters kinetic hindrance that results in incomplete reoxidation of Mn electrodeposits. The density and absolute viscosity of BuMePy-TFSI were measured over a temperature range from 301.0 to 348.0K. A polynomial equation describing the temperature dependence of the density is presented. The viscosity exhibits the Arrhenius temperature dependence and the relevant equation is provided. The manganese coatings were prepared by electrodeposition at several substrates. The surface morphology and X-ray diffraction patterns of these deposits were studied by scanning electron microscopy and powder X-ray diffraction spectroscopy, respectively. The as-electrodeposited manganese coatings were amorphous; however, α-phase manganese was observed after the deposits were annealed under 723K for 1 day. [Copyright &y& Elsevier]

Abstract: The selective extraction of Cs+ and Sr2+ from aqueous solutions by using the ionophores calix[4]arene-bis(tert-octylbenzo-crown-6) (BOBCalixC6) and dicyclohexano-18-crown-6 (DCH18C6), respectively, was demonstrated in the hydrophobic, room-temperature ionic liquid (RTIL), tri-1-butylmethylammonium bis((trifluoromethyl)sulfonyl)imide (Tf2N−). The electrochemistry of Cs+ coordinated by BOBCalixC6 and Sr2+ coordinated by DCH18C6 was examined at a mercury film electrode (MFE) in this ionic liquid by using cyclic staircase voltammetry, sampled current voltammetry at a rotating electrode, and chronoamperometry. Both BOBCalixC6·2Cs+ and DCH18C6·Sr2+ exhibit well-defined reduction waves at approximately −2.4 and −2.9V versus the ferrocene/ferrocenium (Fc/Fc+) couple, respectively, in which the coordinated ions are reduced to their respective amalgams, permitting the recycling of the ionophores. The diffusion coefficients of BOBCalixC6·2Cs+ and DCH18C6·Sr2+ are (2.7±0.1)×10−9 and (2.1±0.1)×10−9 cm2 s−1, respectively, at 30°C. The coulometric efficiency for the reduction and stripping of Cs at mercury pool electrodes was about 90% and was independent of the deposition time, whereas the efficiency for Sr was slightly less than 90% at short times and decreased with the deposition time, probably due to the formation of a passive layer of Sr(Tf2N)2. [Copyright &y& Elsevier]

• Tangled Zn-nanowires were electrodeposited from an ionic liquid (IL). • Zn-nanowires were converted to NiZn nanotubes via galvanic displacement in IL. • IL is critical because the same process is inapplicable using other solvents. • The cation of ILs is the key factor to the successful formation of nanotubes. • The anodized NiZn nanotubes show high activity towards urea oxidation. In this study, Ni nanotube-modified stainless-steel electrode (SSE\Ni anodized) was prepared by galvanic displacement on tangled Zn nanowire-composed sacrificial template (SSE\Zn) followed by anodization in 1 M NaOH. The tangled Zn nanowires were electrodeposited from an amide-type room temperature ionic liquid (RTIL) 1-butyl-1-methypyrrolidinium bis((trifluoromethyl)sulfonyl)amide ([BMP][TFSA]) containing ZnCl 2 , and then galvanic displacement was conducted in the same RTIL with [NiCl 4 2−. The process was unable to be reproduced by using water or choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES) as the reaction media, indicating the unique properties of RTILs. The cations of RTILs are critical to successfully retaining the skeleton of Zn-nanowire-template. SSE\Ni anodized showed high activity towards the oxidation of urea and possessed a detection limit of 3 μM, a sensitivity of 902.8 μA·mM−1·cm−2, and a dynamic range of 1–20000 μM. Most importantly, the electrode could be regenerated by anodization in 1 M NaOH to remove adsorbed urea without significantly altering the surface morphology and performance of the electrode. A low background current was achieved after the regeneration process, which is important for repeatedly using the same electrode in urea determination. [ABSTRACT FROM AUTHOR]

Abstract: The electrodeposition behavior of nickel was investigated at glassy carbon and polycrystalline copper electrodes in the 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) room-temperature ionic liquid. Amperometric titration experiments suggest that Ni(II) reacted with DCA− anions forming [Ni(DCA)4]2− complex anion, which could be reduced to nickel metal via a single-step electron transfer process. However, the anodic dissolution of the nickel deposits was sluggish. The electrodeposition of nickel proceeds via three-dimensional progressive nucleation with diffusion-controlled growth on both glassy and copper substrates. Scanning electron microscopy images of the nickel deposits indicated that the morphology of the nickel electrodeposits is dependent on the deposition potential. Atomic force microscopy topography illustrated that the roughness of the nickel-deposited surface increased with decreasing deposition potential. The crystalline nature of the nickel deposits was revealed by powder X-ray diffraction spectroscopy results which indicated that the grains size of the nickel deposits decreased with decreasing deposition potential. [Copyright &y& Elsevier]

Tangled-Zn nanowire-composed porous structures were prepared via electrodeposition at particular applied potentials in an amide-type ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl) amide (IL [BMP][TFSA]) containing ZnCl 2. The porous Zn was used as a sacrificial template for preparing a porous nickel duplicate via galvanic displacement in [BMP][TFSA] containing [NiCl 4 2−. The solid tangled Zn-nanowires were converted to hollow NiZn-nanotubes in which a typical galvanic displacement reaction occurred through the alloying/dealloying mechanism, and the Kirkendall effect might also took place to form the bi-walled tubes at some spots. In general, the atomic content of Ni exchanged from Zn increased with the increment of reaction time, concentration of [NiCl 4 2−, and temperature. The obtained NiZn could be almost completely dealloyed as verified by the XPS analyses to form a porous Ni electrode that displayed high stability and activity to electrooxidation of urea in alkaline solutions. This study indicated that [BMP][TFSA] played a crucial role on successfully cloning porous Ni from its Zn counterpart. Unlabelled Image • Tangled Zn nanowires were electrodeposited from an amide-type ionic liquid (IL). • Applied potential was the key to successful nanowire formation. • Zn nanowire template was converted to hollow Ni via galvanic displacement. • IL was the key on retaining the template structure in galvanic displacement. • The Ni electrode showed high and stable activity to urea oxidation reaction (UOR). [ABSTRACT FROM AUTHOR]

In this study, an ionic liquid-Fe 3 O 4 nanoparticles-graphite composite electrode (IL-Fe 3 O 4 NPs-GP) with high sensitivity was fabricated using easy-to-made materials and convenient techniques. A hydrophobic ionic liquid 1-butyl-1-methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (IL BMP-TFSA) was used to substitute paraffin oil that is conventionally used as the organic binder for preparing carbon paste electrodes. Fe 3 O 4 NPs show pseudo-peroxidase activity toward hydrogen peroxide (H 2 O 2 ) that was electrocatalytically reduced at the electrode. This electrode shows the synergistic effect from the combination of IL and Fe 3 O 4 NPs, exhibiting a high sensitivity of 200.7 μA mM −1 cm −2 but a narrower dynamic range of 1–25 μM with a detection limit of 0.5 μM. This electrode also shows good stability and several common interferents show negligible effect on the determination of H 2 O 2 . [ABSTRACT FROM AUTHOR]