Mandakini Gupta

Design of screen-printed bulk modified electrodes using anthraquinone–cysteamine functionalized gold nanoparticles and their application to the detection of dissolved oxygen

We investigated the electroanalytical determination of dissolved oxygen using low-cost disposable screen-printed bulk modified electrodes based on nanostructures. A nanostructure based on gold nanoparticles functionalized with an anthraquinone derivative and cysteamine was prepared. The nanostructured material was characterized morphologically using transmission electron microscopy and further physical characterization was carried out by energy-dispersive X-ray spectrometry. The prepared material was incorporated into a screen-printable graphite ink to develop the technology for the economic mass production of the next generation of field sensors. The electroanalytical determination of dissolved oxygen was possible in the range 0.2–6.1 mg L−1 with a detection limit of 0.131 mg L−1 (based on 3σ). We demonstrate proof-of-concept that this approach provides a rapid and inexpensive sensing strategy for the determination of dissolved oxygen in contaminated water samples.

An anthraquinone moiety/cysteamine functionalized-gold nanoparticle/chitosan based nanostructured composite for the electroanalytical detection of dissolved oxygen within aqueous media

This work reports a nanostructured composite electrode comprising gold nanoparticles, anthraquinone derivatives and chitosan electrically wired via immobilisation upon a glassy carbon macroelectrode. The as-prepared nanostructured composite was morphologically characterised using transmission electron microscopy with surface characterization performed with atomic force microscopy while other physical characterization was undertaken by infra-red, UV-Vis, and energy dispersive X-ray spectroscopy. Electrochemical investigations and stability measurements of the composite electrode were performed by cyclic voltammetry. Electrocatalytic activity of the composite electrode was investigated for the oxygen reduction reaction in 0.1 M phosphate buffer solution of pH 6.5. Furthermore, the response characteristics show that this fabricated electrode has a shelf-life of between 3 and 4 months and has improved electrochemical and electrical properties and firm adhesion of the material with homogeneous dispersion at the electrode surface. The linear range and detection limit for the electrochemical detection of dissolved oxygen under the optimum conditions using the nanostructured composite was found to be over the accessible range of 0.2 to 5.8 mg L−1 and 0.03 mg L−1 respectively.

A nanocomposite of ferrocenoyl glutaric acid hydrazone and multiwalled carbon nanotubes as a sensor for azide ions

A nanocomposite containing ferrocenoyl glutaric acid hydrazone and multiwalled carbon nanotubes (MWCNTs) has been synthesized and characterized for its structural, morphological and electrochemical properties. Characterization has been done using scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), infrared (IR), X-ray photoelectron spectroscopy (XPS), and UV-visible studies. The electrochemical behavior and stability of the modified electrode have been investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). A self-standing film of this electroactive and homogeneous composite has been obtained by solution casting method. It is observed that the ferrocenoyl glutaric acid hydrazone (L)/MWCNTs/Nafion composite has better electrochemistry, electrical properties and firm adhesion of the material at the electrode surface. The modified electrode showed an electro-catalytic response to the oxidation of azide ions at the potential of 0.30 V in 0.1 M phosphate buffer solution (pH 7.1). The linear range and detection limit for the azide ion were found to be 0.02 mM to 20 mM and 0.312 μM, respectively.

Modification of Anthraquinone-2-Carboxylic Acid with Multiwalled Carbon Nanotubes and Electrocatalytic Behavior of Prepared Nanocomposite Towards Oxygen Reduction

We herein report a simple method for the preparation of multiwalled carbon nanotubes-anthraquinone-2-carboxylic acid (AQ-COOH-AMWCNTs) nano-composite. For the preparation of the composite, multiwalled carbon nanotubes have been functionalized with amino group (AMWCNTs) using 3-aminopropyltrimetho-xysilane. Then, anthraquinone-2-carboxylic acid is coupled to amino functionalized multiwalled carbon nanotubes (AMWCNTs) by carbodiimide coupling. Characterization of the material has been performed with scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform IR (FTIR) and cyclic voltammetry (CV). The prepared material exhibited electrocatalytic behavior towards the reduction of oxygen to hydrogen peroxide with a detection limit of 0.02 ppm. The prepared material was stable with no leaching observed of the mediator.