Electrocatalytic oxidation of hydroxylamine by (RuPc)2 graphite modified electrode

Electrocatalytic oxidation of hydroxylamine on dinuclear ruthenium phthalocyanine (RuPc)₂ modified electrode is studied using cyclic voltammetry (CV) and rotating disc electrode (RDE) techniques. A two-electron oxidation of hydroxylamine to N₂O is observed in the pH range of 9–13. A suitable mechanism is proposed by analyzing the rate equation and the Tafel slope.     

Electrocatalytic oxidation of norepinephrine at a reduced C60-[dimethyl-(β-cyclodextrin)]2 and Nafion chemically modified electrode

The reduced C₆₀-[dimethyl-(β-cyclodextrin)]₂/Nafion chemically modified electrode is demonstrated to catalyze the electrochemical response of norepinephrine (NE) by cyclic voltammetry. A pair of well-defined redox waves were obtained and the calculated standard rate constant (k_s) is 4.4×10⁻³ cm s⁻¹ at this reduced CME, indicating that the reduced C₆₀-[dimethyl-(β-cyclodextrin)]₂ can act as promoter to the electron transfer of NE.     

Mild oxidation of alcohols with periodic acid catalyzed by [Ru(acac)2(CH3CN)2]PF6 in water

A facile [Ru(acac)₂(CH₃CN)₂]PF₆ (Hacac = acetylacetone) (1) catalyzed oxidation of alcohols to aldehydes or ketones using H₅IO₆ as oxidant in water at room temperature is described.     

Selective determination of ascorbic acid with a novel hybrid material based 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid and the Dawson type ion [P2Mo18O62] immobilized on glassy carbon

In this study, we synthesized a new hybrid material using well-Dawson K₆[P₂Mo₁₈O₆₂]·nH₂O and a room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]). CHN elemental analysis showed that one mole of [P₂Mo₁₈O₆₂]⁶⁻ reacts with 6 moles of [BMIM]⁺ to form [BMIM]₆P₂Mo₁₈O₆₂. FT-IR spectra showed the presence of both 1-butyl-3-methylimidazolium cation and the Dawson anion. TG analysis displayed a relative thermal stability of the hybrid material compared to the parent Dawson POM. The new hybrid material [BMIM]₆P₂Mo₁₈O₆₂ was immobilized on glassy carbon (GC) electrode and the modified electrode was investigated by cyclic voltammetry and amperometry. Compared to the electrochemical behavior of dissolved [P₂Mo₁₈O₆₂]⁶⁻, a slight shift in the redox peaks towards negative potentials is observed for the immobilized [BMIM]₆P₂Mo₁₈O₆₂. The relationship between the peak currents of the deposited [BMIM]₆P₂Mo₁₈O₆₂ film and scan rate is shown to be linear, which demonstrates a surface-confined electron transfer processes. [BMIM]₆P₂Mo₁₈O₆₂ modified electrode showed high sensitivities towards pH and shown to be active even at neutral pH. [BMIM]₆P₂Mo₁₈O₆₂ modified GC electrode was subjected to cyclic voltammetry and amperometry in the presence of ascorbic acid (AA) and found to exhibit a remarkable catalytic activity towards the oxidation of AA. The catalytic oxidation peak of AA at [BMIM]₆P₂Mo₁₈O₆₂ modified GC electrode occurs at low potential of ∼0 V vs Ag/AgCl at neutral pH and shifts to more positive potentials when pH decreases. Comparison between [BMIM]₆P₂Mo₁₈O₆₂ and [P₂Mo₁₈O₆₂]⁶⁻ modified GC films towards the oxidation of AA suggests that the significant decrease in the overpotentials recorded with [BMIM]₆P₂Mo₁₈O₆₂ film is related to the presence of ionic liquid cation in the hybrid material, which probably plays the role of the redox mediator. The resulting AA sensor [BMIM]₆P₂Mo₁₈O₆₂/GC has a significant sensitivity of ∼63 nA/μM AA, fast response time (<9 s), low detection limit (<0.1 μM), high selectivity towards endogenous interferences such as uric acid, acetaminophen and dopamine, a linear range from 0.1 μM to at least 22 mM AA and was stable for at least 2 weeks. In addition, such AA sensors can operate in a pH range from 0 to at least 7.     

Evaluation of the microporosity of pillared [Fe(CN)6]–MgAl–LDHs

Layered double hydroxides (LDHs) containing Mg²⁺ and Al³⁺ in the basic layers and NO⁻₃ as an interlayer anion were synthesized by the method of coprecipitation (pH 10). By changing the Mg²⁺/Al³⁺ ratio (1.5–4.5), the charge density on the (NO₃)–MgAl–LDH sheets was varied. After pillaring with Fe(CN)³⁻₆, which was based on an anion exchange process, the interlayer space became accessible. This was reflected in the large created surface areas and micropore volumes. The applied models for the calculation of the micropore size distributions (Maes–Zhu–Vansant and Horvath–Kawazoe) gave matching results, revealing narrow distributions for all the samples, with the majority of the pores smaller than 0.71 nm. A correlation was found between the Mg²⁺/Al³⁺ ratio and the resulting microporosity after pillaring. The optimal ratio was situated around 3.3, resulting in a pillared [Fe(CN)₆]–MgAl–LDH with a Langmuir surface area of 499 m²/g and a micropore volume between 0.158 ml/g (μPV_min) and 0.177 ml/g (μPV_max). As an alternative, direct coprecipitation of the pillared LDHs was evaluated. This one-step mechanism proved to be a method producing similar results. Taking all this into consideration, one can conclude that hexacyanoferrate(III) complexes form ideal anionic pillars for the creation of microporous layered double hydroxides.