Jayashree S. Gamare

Highly Sensitive Detection of Arsenite Based on Its Affinity toward Ruthenium Nanoparticles Decorated on Glassy Carbon Electrode.

Metallic ruthenium nanoparticles (Ru NPs) are formed on the glassy carbon electrode (GC) at electrodeposition potential of -0.75 V, as observed from X-ray photoelectron spectroscopy. Thus formed Ru NPs have the arsenite selective surface and conducting core that is ideally suited for designing a highly sensitive and reproducible response generating matrix for the arsenite detection at an ultratrace concentration in aqueous matrices. Contrary to this, arsenate ions sorb via chemical interactions on the ruthenium oxide (RuO2 and RuO3) NPs formed at -0.25 V, but not on the Ru NPs. For exploring a possibility of the quantification of arsenite in the ultratrace concentration range, the Ru NPs have been deposited on the GC by a potentiostatic pulse method of electrodeposition at optimized -0.75 V for 1000 s. Arsenite preconcentrates onto the Ru surface just by dipping the RuNPs/GC into the arsenite solution as it interacts chemically with Ru NPs. Electrochemical impedance spectroscopy of As(III) loaded RuNPs/GC shows a linear increase in the charge transfer resistance with an increase in As(III) conc. Using a differential pulse voltammetric technique, arsenite is oxidized to arsenate leading to its quantitative determination without any interference of Cu(2+) ions that are normally encountered in the water systems. Thus, the use of RuNPs/GC eliminates the need for a preconcentration step in stripping voltammetry, which requires optimization of the parameters like preconcentration potential, time, stirring, inferences, and so on. The RuNPs/GC based differential pulse voltammetric (DPV) technique can determine the concentration of arsenite in a few min with a detection limit of 0.1 ppb and 5.4% reproducibility. The sensitivity of 2.38 nA ppb(-1) obtained in the present work for As(III) quantification is considerably better than that reported in the literature, with a similar detection limit and mild conditions (pH = 2). The RuNPs/GC based DPV has been evaluated for its analytical performance using the lake water, ground water, and seawater samples spiked with known amounts of As(III).

Ruthenium Nanoparticles Mediated Electrocatalytic Reduction of UO22+ Ions for Its Rapid and Sensitive Detection in Natural Waters

Reduction of UO22+ ions to U4+ ions is difficult due to involvement of two axially bonded oxygen atoms, and often requires a catalyst to lower the activation barrier. The noble metal nanoparticles (NPs) exhibit high electrocatalytic activity, and could be employed for the sensitive and rapid quantifications of U022+ ions in the aqueous matrix. Therefore, the Pd, Ru, and Rh NPs decorated glassy carbon electrode were examined for their efficacy toward electrocatalytic reduction of UO22+ ions and observed that Ru NPs mediate efficiently the electro-reduction of UO22+ ions. The mechanism of the electroreduction of UO22+ by the RuNPs/GC was studied using density functional theory calculations which pointed different approach of 5f metal ions electroreduction unlike 4p metal ions such as As(III). RuNP decorated on the glassy carbon would be hydrated, which in turn assist to adsorb the uranyl sulfates through hydrogen bonding thus facilitated electro-reduction. Differential pulse voltammetric (DPV) technique, was used for rapid and sensitive quantification of UO22+ ions. The RuNPs/GC based DPV technique could be used to determine the concentration of uranyl in a few minutes with a detection limit of 1.95 ppb. The RuNPs/GC based DPV was evaluated for its analytical performance using seawater as well lake water and groundwater spiked with known amounts of UO22+.

A novel biamperometric methodology for thorium determination by EDTA complexometric titration

Abstract A biamperometric methodology is described for the determination of thorium by EDTA complexometric titration, based on the observed electrochemical behaviour of EDTA when the applied potential was ≥200 mV between the twin Pt electrodes. Studies carried out showed that a pH range of 2.4–2.7 was optimum for the determination. Accuracy and precision of the method were evaluated using different amounts of thorium ranging from 50 μg to 5 mg. Studies on the interference of uranium were carried out with different amounts of uranium ranging from 20 to 80% using the presently developed approach of biamperometry as well as the conventional indicator method. The method was employed for the determination of Th in (Th,U)O2 samples containing different amounts of Th and U.

Novel Electrochemical Synthesis of Polypyrrole/Ag Nanocomposite and Its Electrocatalytic Performance towards Hydrogen Peroxide Reduction

A simple electrochemical method of synthesis of polypyrrole/silver (PPy/Ag) nanocomposite is presented. The method is based on potentiodynamic polymerization of pyrrole followed by electrodeposition of silver employing a single potentiostatic pulse. The synthesized PPy film has embedded Ag nanocubes. The morphology and structure of the resulting nanocomposite were characterized by field emission scanning electron microscopy and X-ray diffraction. Electron paramagnetic resonance studies showed that silver nanoparticle deposition on polypyrrole leads to an increase in carrier density, indicative of enhanced conductivity of the resulting composite. Electrocatalytic performance of the prepared composite was examined for reduction of hydrogen peroxide and was compared with corresponding PPy film and bare glassy carbon electrode.

Poly(3,4-ethylenedioxythiophene)–Poly(styrenesulfonate)-Coated Glassy-Carbon Electrode for Simultaneous Voltammetric Determination of Uranium and Plutonium in Fast-Breeder-Test-Reactor Fuel

Uranium (U) and plutonium (Pu) contents in nuclear materials must be maintained to a definite level in order to get the desired performance of the fuel inside the reactor. Therefore, high accuracy and precision is an essential criterion for the determination of U and Pu. We already reported the voltammetric determination of Pu in the presence of U in fast-breeder-test-reactor (FBTR) fuel samples, but interfacial, coupled chemical reactions between U(IV) and Pu(IV) enhance the peak-current density of U(VI) reduction and thus make voltammetry unsuitable for the quantitative determination of U in the presence of Pu. Thus, developing a voltammetric method for the simultaneous determination of U and Pu is highly challenging. Herein, we report the simultaneous voltammetric determination of U and Pu in 1 M sulfuric acid (H2SO4) on a poly(3,4-ethylenedioxythiophene) (PEDOT)-poly(styrenesulfonate) (PSS)-modified glassy-carbon (GC) electrode (PEDOT-PSS/GC). The modified electrode shows enhanced performance compared with bare GC electrodes. The peak-current density for U(VI) reduction is enhanced in the presence of Pu(IV), but it attains saturation when [Pu]/[U] in solution is maintained ≥2. Hence, under these circumstances, the variation of Pu concentration no longer influences the U(VI)-reduction peak, and thus the quantitative determination of U in the presence of Pu is possible. No interference is observed from commonly encountered impurities present in FBTR fuel samples. This method shows accuracy and precision comparable to those of the biamperometry method. High robustness, fast analysis, simultaneous determination, reduced radiation exposure to the analyst, and ease of recovery of U and Pu from analytical waste makes it a suitable candidate to substitute the presently applied biamperometry method.