Ninie Suhana Abdul Manan

Electrochemistry of Sulfur and Polysulfides in Ionic Liquids

The electrochemistry of elemental sulfur (S(8)) and the polysulfides Na(2)S(4) and Na(2)S(6) has been studied for the first time in nonchloroaluminate ionic liquids. The cyclic voltammetry of S(8) in the ionic liquids is different to the behavior reported in some organic solvents, with two reductions and one oxidation peak observed. Supported by in situ UV-vis spectro-electrochemical experiments, the main reduction products of S(8) in [C(4)mim][DCA] ([C(4)mim] = 1-butyl-3-methylimidazolium; DCA = dicyanamide) have been identified as S(6)(2-) and S(4)(2-), and plausible pathways for the formation of these species are proposed. Dissociation and/or disproportionation of the polyanions S(6)(2-) and S(4)(2-) appears to be slow in the ionic liquid, with only small amounts of the blue radical species S(3)(•-) formed in the solutions at r.t., in contrast with that observed in most molecular solvents.

Volatilisation of ferrocene from ionic liquids: kinetics and mechanism

The evaporation of dissolved ferrocene from non-volatile ionic liquids under a flow of nitrogen gas has been monitored voltammetrically and modelled mathematically. The rate of volatilisation was found to depend on the surface tension of the ionic liquid, and a model is presented.

The kinetics of ferrocene volatilisation from an ionic liquid.

The volatilisation of ferrocene (Fc), dissolved in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [C(4)mpyrr][NTf(2)], to the gas phase has been indirectly monitored by cyclic voltammetry and chronoamperometry. Simulation of the observed trends in concentration with time using a simple model allowed quantification of the process. Volatilisation of dissolved Fc under flowing wet and dry dinitrogen gas (N(2)) was found to be kinetically limited with a rate constant in the region of 2×10(-7) cm s(-1). The activation energy of diffusion for Fc was found to be 28.2±0.7 kJ mol(-1), while the activation energy of volatilisation of Fc from [C(4)mpyrr][NTf(2)] to dry N(2) was found to be 85±2 kJ mol(-1).

Polyaniline-dicationic ionic liquid coated with magnetic nanoparticles composite for magnetic solid phase extraction of polycyclic aromatic hydrocarbons in environmental samples

In this present study, magnetic nanoparticles (MNPs) nanocomposites modified with polyaniline (PANI) coated newly synthesised dicationic ionic liquid (DICAT) forming MNP-PANI-DICAT were successfully synthesised as new generation material for magnetic solid phase extraction (MSPE). MNP-PANI-DICAT was characterised by FT-IR NMR, CHN, BET, SEM, TEM, and VSM techniques and the results were compared with MNP-PANI and native MNP. This new material was applied as a magnetic adsorbent for the pre-concentration and separation of polycyclic aromatic hydrocarbons (PAHs) due to the π-π interaction between polyaniline shell and dicationic ionic liquid (DICAT) with PAHs compounds. Under the optimal conditions, the proposed method was evaluated and applied for the analysis of PAHs in environmental samples using gas chromatography-mass spectrometry (GC-MS). The validation method showed good linearity (0.005-500µgL-1) with the coefficient of determination (R2) > 0.999. The limits of detection (LOD) and quantification (LOQ) of the developed method (MNP-PANI-DICAT-MSPE) were in the range of 0.0008-0.2086µgL-1 and 0.0024-0.6320µgL-1, respectively. The enrichment factor (EF) of PAHs on MNP-PANI-DICAT-MSPE were in the range of 7.546-29.632. The extraction recoveries of natural water, sludge, and soil samples were ranged from 80.2% to 111.9% with relative standard deviation (RSD) less than 5.6%. The newly synthesised MNP-PANI-DICAT possess good sensitivity, reusability, and fast extraction of PAHs under the MSPE procedure in various environmental samples.

A novel potentiometric self-plasticizing polypyrrole sensor based on a bidentate bis-NHC ligand for determination of Hg(II) cation

In this approach, a new potentiometric self-plasticizing polypyrrole sensor was constructed based on a bidentate bis-NHC ligand for the purpose of Hg2+ cation determination. An ionophore, namely bis[1-benzyl-benzimidazoliumethyl]-4-methylbenzenesulfonamide bromide (NHCL) was successfully synthesized and characterized using FT-IR, 1H NMR, 13C NMR spectroscopy, CHN elemental analysis, X-ray single crystal diffraction and UV-Vis spectroscopy. The electrode with a membrane optimum composition demonstrated a good Nernstian response to Hg2+ cations ranging from 1.0 × 10−6 to 1.0 × 10−2 M with a detection limit of 2.5 × 10−7 M and a Nernstian slope of 28.10 ± 0.29 mV per decade over a pH range between 4.5–7.0 with a response time of about 20 seconds at room temperature. The electrode exhibited better selectivity towards Hg2+ ions in comparison with some soft and hard metals; most of these metal ions do not show significant interference . The proposed electrode also has applications in the direct determination of Hg2+ cations in aqueous solutions with sensible accuracy and precision.

Conductivity and Dielectric Studies of Lithium Trifluoromethanesulfonate Doped Polyethylene Oxide-Graphene Oxide Blend Based Electrolytes

Series of polymer blend consisting of polyethylene oxide (PEO) and graphene oxide (GO) as co-host polymer were prepared using solution cast method. The most amorphous PEO-GO blend was obtained using 90 wt.% of PEO and 10 wt.% of GO as recorded by X-ray diffraction (XRD). Fourier transform infrared spectroscopy (FTIR) analysis proved the interaction between PEO, GO, lithium trifluoromethanesulfonate (LiCF3SO3), and ethylene sulfite (ES). Incorporation of 25 wt.% LiCF3SO3 into the PEO-GO blend increases the conductivity to  S cm−1. The conductivity starts to decrease when more than 25 wt.% salt is doped into the polymer blend. The addition of 1 wt.% ES into the polymer electrolyte has increased the conductivity to  S cm−1. Dielectric studies show that all the electrolytes obey non-Debye behavior.

The Effect of Temperature on Kinetics and Diffusion Coefficients of Metallocene Derivatives in Polyol-Based Deep Eutectic Solvents.

The temperature dependence of the density, dynamic viscosity and ionic conductivity of several deep eutectic solvents (DESs) containing ammonium-based salts and hydrogen bond donvnors (polyol type) are investigated. The temperature-dependent electrolyte viscosity as a function of molar conductivity is correlated by means of Walden’s rule. The oxidation of ferrocene (Fc/Fc+) and reduction of cobaltocenium (Cc+/Cc) at different temperatures are studied by cyclic voltammetry and potential-step chronoamperometry in DESs. For most DESs, chronoamperometric transients are demonstrated to fit an Arrhenius-type relation to give activation energies for the diffusion of redox couples at different temperatures. The temperature dependence of the measured conductivities of DES1 and DES2 are better correlated with the Vogel-Tamman-Fulcher equation. The kinetics of the Fc/Fc+ and Cc+/Cc electrochemical systems have been investigated over a temperature range from 298 to 338 K. The heterogeneous electron transfer rate constant is then calculated at different temperatures by means of a logarithmic analysis. The glycerol-based DES (DES5) appears suitable for further testing in electrochemical energy storage devices.

Superhydrophobic magnetic nanoparticle-free fatty acid regenerated from waste cooking oil for the enrichment of carcinogenic polycyclic aromatic hydrocarbons in sewage sludges and landfill leachates

In this study, Fe3O4 nanoparticles grafted with superhydrophobic free fatty acids from waste cooking oil (FFA@MNP) were successfully fabricated as an adsorbent for the magnetic solid phase extraction (MSPE) technique. The synthesized nanomaterial (FFA@MNP) was analyzed using Fourier transform infrared spectroscopy, transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, water contact angle analysis and vibrating sample magnetometry, which confirmed the successful functionalization of free fatty acids onto the surface of Fe3O4 nanoparticles. The adsorption efficiency of the synthesised FFA@MNP in MSPE was evaluated by the extraction of five selected polycyclic aromatic hydrocarbons (PAHs), namely, fluorene (Flu), fluoranthene (FLT), pyrene (Pyr), chrysene (Cry), and benzo(a)pyrene (BaP), from environmental samples prior to HPLC-DAD analysis. The MSPE method was optimized for various parameters such as adsorbent dosage, type of organic eluent, volume of organic eluent, extraction time, desorption time, pH of the solution and sample volume. The low detection limit for the proposed MSPE was found to be 0.001 to 0.05 ng mL−1. Under optimized conditions, the newly synthesized material was applied as an adsorbent for environmental leachate and sludge samples for enrichment of the selected PAHs from these complex matrices. The stability and reusability studies demonstrated that FFA@MNP could be used for up to five cycles. Due to hydrophobic interactions between the long alkyl chains of FFA@MNP and PAHs, good recoveries (82.8–116.6%) with low relative standard deviations ranging from 5.2% to 11.0% were obtained for the spiked leachate samples. For the spiked sludge samples, the recovery range was found to be from 72.3% to 119.9%, with a satisfactory % RSD (4.8–11.8%).

Electrochemical determination of 2,4-dichlorophenol at β-cyclodextrin functionalized ionic liquid modified chemical sensor: voltammetric and amperometric studies

A highly effective approach was developed for the specific detection of 2,4-dichlorophenol (2,4-DCP) in real samples, based on a cyclodextrin functionalized ionic liquid modified carbon paste electrode (β-CD-BIMOTs/CPE). First, systematic optimization procedures were carried out for β-CD-BIMOTs/CPE by cyclic voltammetry (CV) and chrono-amperometry methods. Second, the optimized methods were applied for the determination of 2,4-DCP in environmental samples. A large increase in the peak currents was observed in CV and chrono-amperometry of 2,4-DCP when using β-CD-BIMOTs/CPE compared to native cyclodextrin modified carbon paste electrode (β-CD/CPE) and bare carbon paste electrode (CPE). A comparison of voltammetric behavior between CPE, β-CD/CPE and β-CD-BIMOTs/CPE indicated that the combination of ionic liquid and cyclodextrin in the composition of the carbon paste significantly improved the conductivity and compatibility of the sensor. The introduction of β-CD-BIMOTs as a modifier results in clearly enhanced sensitivity and selectivity towards 2,4-DCP over a wide concentration range of 4 μmol L−1 to 100 μmol L−1, with a detection limit of 1.2 μmol L−1. The interferences from foreign substances in the peak current response were also studied and caused only minor changes in the signals (<4.6%). Good repeatability was achieved because of the stability of the modified electrode. The proposed method was applied to the determination of 2,4-DCP in leachates from landfill, mineral water and lake water with recoveries of (85.46–117.68%), (98.72–107.91%) and (89.25–107.46%), respectively.

Synthesis of PANI/hematite/PB hybrid nanocomposites and fabrication as screen printed paper based sensors for cholesterol detection

In this work, the composites of polyaniline/nano-hematite (α-Fe2O3)/Prussian Blue (PB) were successfully synthesized via a sonochemical method. This nanocomposite (PB/CPANI) has been used for the modification of paper-based sensors for cholesterol detection. The electrochemical studies of this nanocomposite showed a well-defined cyclic voltammogram for hydrogen peroxide (H2O2) with a remarkable electrochemical sensitivity. This nanocomposite modified paper-based electrode also showed excellent electrocatalytic activity towards H2O2 in the interference-free cathodic region. In addition, cholesterol oxidase was immobilized on the PB/CPANI-modified paper-based electrode for selective detection of cholesterol. Under optimum conditions, a linear range of 0.6–6.0 mM with a very low detection limit of 0.52 mM for cholesterol and a good sensitivity of 411.7 μA mM−1 cm−2 were obtained which indicated that the method presented is outstandingly appropriate to determine cholesterol in bovine serum albumin. This work might be an alternative, interference-free, and cost-effective approach for biomonitoring of cholesterol both in methodological studies and in clinical laboratories.