Pankaj Kumar Rastogi

A promising electrochemical sensing platform based on a silver nanoparticles decorated copolymer for sensitive nitrite determination

In this paper, we report a facile route to synthesize silver nanoparticles (Ag NPs) incorporated into a copolymer of methyl methacrylate (MMA) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) (abbreviated as P(MMA-co-AMPS)) and its application to construct an electrochemical nitrite (NO2−) sensor. The copolymer nano-composite material (Ag–P(MMA-co-AMPS) is characterized by means of transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy, X-ray powder diffraction methods, thermogravimetric analysis and electrochemical impedance spectroscopy. Further, Ag–P(MMA-co-AMPS) is used to prepare an electrochemical sensing platform (ESP) on a glassy carbon electrode (GC) surface. NO2− is electrocatalytically oxidized at the ESP (GC/Ag–P(MMA-co-AMPS), which leads to a sensitive determination of NO2−. The oxidation current of NO2− is linear to its concentration in the range of 1.0–100 000.0 μM and the detection limit is found to be 0.2 μM with a sensitivity 104.6 μA mM−1 cm−2. The observed analytical parameters such as wide linear range, low detection limit, high sensitivity and short response time are comparable or superior to other previously reported NO2− sensors. Kinetic parameters are evaluated using cyclic voltammetry and chronoamperometry. Finally it is demonstrated that the proposed sensor can be used for the selective determination of NO2− present in water samples and the results are quite promising.

Synthesis and characterization of gold nanoparticles incorporated bentonite clay for electrocatalytic sensing of arsenic(III)

AbstractIn the present manuscript, a simple and easy route to synthesize bentonite (bt) clay-supported gold nanoparticles (Au NPs) is reported (represented as Au-bt). Application of this new environmentally benign material in electrocatalytic determination of arsenite (As(III)) was studied. The successful synthesis and incorporation of Au NPs into the bt clay is supported by spectroscopic, microscopic and electrochemical methods. The synthesized Au-bt material was used to modify glassy carbon electrode (GC) by the evaporation of Au-bt aqueous suspension dropped on the surface of the GC (GC/Au-bt). Cyclic voltammetry and chronoamperometry studies of As(III) solutions were performed with this GC/Au-bt electrode which act as efficient platform for the electro-oxidation of As(III) to As(V) at a very low overpotential. Kinetic parameters were evaluated for the oxidation of As(III) at the GC/Au-bt platforms. A wide linear calibration range for the determination of As(III) from 1 to 1700 μM was obtained with high reproducibility and stability. A limit of detection, 0.1 μM was achieved with high sensitivity. Additionally, it showed a good selectivity for the determination of As(III) in the presence of copper(II) and other interfering ions suggesting a promising new route for trace level determination of As(III) in neutral conditions. Graphical AbstractBentonite clay supported, gold nanoparticle-based, biocompatible material was synthesized (represented as Au-bt) and it shows remarkable elecrocatalytic activity for As(III) oxidation. Based on the electrocatalytic activity of synthesized Au-bt material, As(III) determination is demonstrated in neutral electrolyte solution.

Methylene blue incorporated mesoporous silica microsphere based sensing scaffold for the selective voltammetric determination of riboflavin

This study reports the simple, selective and sensitive voltammetric detection of riboflavin (RF) using methylene blue (MB) incorporated sulfonic acid functionalized mesoporous silica microspheres (MSM), represented as MB-SO3H-MSM. MB-SO3H-MSM is synthesized and characterized by spectroscopic and microscopic methods. This material is coated on a glassy carbon (GC) electrode (symbolized as GC/MB-SO3H-MSM) to utilize it in electroanalytical applications. The electrochemical behavior of MB-SO3H-MSM is established using the GC/MB-SO3H-MSM electrode by cyclic voltammetry (CV) and electrochemical impedance spectroscopy techniques. The electrochemical behavior of RF at the GC/MB-SO3H-MSM electrode is also studied by CV. Compared to bare GC and SO3H-MSM coated GC, the GC/MB-SO3H-MSM electrode shows favorable electron transfer kinetics as well as an enhanced and stable electrochemical response of RF. Furthermore CV and differential pulse voltammetry (DPV) are used for the quantitative determination of RF at the GC/MB-SO3H-MSM electrode. The DPV response shows two linear calibration ranges of 10.0 nM to 15.0 μM and 15.0 to 50.0 μM. The detection limit based on the first linear calibration range is calculated as 5.0 nM with a sensitivity of 393.0 μA mM−1 cm−2. The fabricated sensing scaffold shows an excellent selectivity for RF over other soluble vitamins and interfering ions. The stability, reproducibility and determination of RF in pharmaceutical products are also demonstrated effectively.

Non-enzymatic Determination of Uric Acid by Ion Exchange Voltammetry at a Permselective Electrochemical Sensing Platform

Abstract Here we demonstrate a new strategy for electrochemical determination of uric acid (UA) using a cationic polymer as an electrochemical sensing platform (ESP). The cationic polymer is based on branched polyethylenimine (BPEI) cross-linked with ethylene glycol diglycidyl ether (EGDE). Ion exchange property of this cross linked cationic polymer (BPEI-EGDE) with negatively charged electroactive species is studied by cyclic voltammetry. Furthermore, this cationic cross-linked BPEI-EGDE polymer is coated on a glassy carbon electrode (GC) to construct the ESP for the quantitative analysis of biologically important molecule, UA at pH 7.0. It shows efficient oxidation of UA with respect to bare GC due to favorable electrostatic interaction of anionic UA with the positively charged BPEI-EGDE film. Finally it is demonstrated that the BPEI- EGDE films can be used as efficient ESP for non-enzymatic UA determination in the concentration range of 5 to 1500 µM with a sensitivity of 153 µA μM-1cm-2.

Synthesis, characterization and cyclic voltammetric study of copper(II) and nickel(II) polymer chelates.

Graft copolymers based on dextran (Dx) and 2-acrylamido-2-methyl-1-propane sulphonic acid (AMPS) were synthesized by free radical initiated solution polymerization technique using ceric ammonium nitrate as initiator. These graft copolymers were used to prepare Cu(II) and Ni(II) chelates by reactions with Cu(II) and Ni(II) metal ions respectively. Graft copolymer and metal chelates were characterized by elemental analysis, intrinsic viscosity, FT-IR, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA) and powder X-ray diffraction (XRD). Elemental analysis, intrinsic viscosity and FT-IR studies revealed the incorporation of metal ions to form metal chelates. SEM studies showed the change in morphology due to metal incorporation. From AFM studies it was observed that there was increase in Root mean square (RMS) roughness values in case of metal complexes. Metal chelates were observed to be thermally more stable than graft copolymer from TGA. UV-vis spectroscopy study revealed increase in absorbance values and cyclic voltammetric (CV) studies showed more than tenfold increase in redox current due to formation of Cu(II) and Ni(II) metal chelates. The binding constants of each complex determined by using UV-visible spectroscopy revealed that Cu(II) has more binding ability than Ni(II).