A highly efficient process for oxidative degradation of 1,3-dialkylimidazolium ionic liquids in hydrogen peroxide/acetic acid aqueous medium assisted by ultrasonic chemical irradiation is, for the first time, described. It is shown that more than 93% of the 1,3-dialkylimidazolium cation with the corresponding Cl-, Br-, BF4- and PF6- counter-anions at a concentration of 2.5 mM can be degraded at 50 degrees C within 12 h while at 72 h the conversions approach 99%. A tentative mechanism for the degradation of these ILs is for the first time proposed through a detailed kinetic analysis of several characteristic transients and/or immediate products, which are identified during the ILs degradation using GC-MS. The results clearly indicate that three hydrogen atoms in the imidazolium ring are the first sites preferably oxidized, followed by cleavage of the alkyl groups attached to the N atoms from the ring. The nature of the alkyl chain length on the imidazolium ring and the type of counter anion do not seem to affect the degradation process. Further, selective fragmentations of C-N bonds of the imidazolium or derived ring lead to ring opening, forming degraded intermediates. It is also shown that acetoxyacetic acid and biurea are the final kinetically stable degraded products from the ILs under the degradation conditions.
In this work, we prepared large-area, three-dimensional interconnected graphene oxide (GNO) intercalated by self-doped polyaniline nanofibers (SPAN, a copolymer of aniline and m-aminobenzenesulfonic acid) through a simple adsorption and intercalation route via sonication of the mixed dispersions of both components. The strong p-p* stacking between the backbones of SPAN and the GNO basal planes, and the electrostatic repulsion between the negatively charged SPAN and graphene oxide sheets yield a unique free-standing, three-dimensional interconnected nanostructure. The nanocomposite possesses a large specific surface area and maintains a homogenous and stable dispersion with SPAN, which endows it with a high conductivity and good electrocatalytic activity. Because the negative charge and specific structure of the nanocomposite can prompt the adsorption of positively charged guanine and adenine via strong p-p* interactions or electrostatic adsorption, the hybrid was adopted as an excellent sensing platform for highly sensitive determination of guanine and adenine. The electrocatalytic platform exhibited some advantages, such as high sensitivity, good reproducibility and long-term stability.
A novel and simple synchronous electrochemical synthesis of poly(xanthurenic acid, Xa), electrochemically reduced graphene oxide nanocomposite (PXa-ERGNO), via cyclic voltammetry (CV) was reported, where graphene oxide (GNO) and Xa monomer were adopted as precursors. The resulting PXa-ERGNO nanocomposite was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, CV and electrochemical impedance spectroscopy (EIS). The π-π interactions between the conjugated GNO layers and aromatic ring of Xa-enhanced the electropolymerization efficiency accompanied with an increased electrochemical response of PXa. The rich carboxyl groups of PXa-ERGNO film were applied to stably immobilize the probe DNA with amino groups at 5' end via covalent bonding. The captured probe could sensitively and selectively recognize its target DNA via EIS. The dynamic detection range was from 1.0 × 10(-14) mol/L to 1.0 × 10(-8) mol/L with a detection limit of 4.2 × 10(-15) mol/L due to the synergistic effect of integrated PXa-ERGNO nanocomposite. This graphene-based electrochemical platform showed intrinsic advantage, such as simplicity, good stability, and high sensitivity, which could serve as an ideal platform for the biosensing field.
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