Sayee Kannan Ramaraj

A non-enzymatic amperometric hydrogen peroxide sensor based on iron nanoparticles decorated reduced graphene oxide nanocomposite

A simple and facile green process was used for the synthesis of iron nanoparticles (FeNPs) decorated reduced graphene oxide (rGO) nanocomposite by using Ipomoea pes-tigridis leaf extract as a reducing and stabilizing agent. The as-prepared rGO/FeNPs nanocomposite was characterized by transmission electron microscopy, X-ray spectroscopy and Fourier transform infrared spectroscopy. The nanocomposite was further modified on the glassy carbon electrode and used for non-enzymatic sensing of hydrogen peroxide (H2O2). Cyclic voltammetry results reveal that rGO/FeNPs nanocomposite has excellent electro-reduction behavior to H2O2 when compared to the response of FeNPs and rGO modified electrodes. Furthermore, the nanocomposite modified electrode shows 9 and 6 folds enhanced reduction current response to H2O2 than that of rGO and FeNPs modified electrodes. Amperometric method was further used to quantify the H2O2 using rGO/FeNPs nanocomposite, and the response was linear over the concentration ranging from 0.1μM to 2.15mM. The detection limit and sensitivity of the sensor were estimated as 0.056μM and 0.2085μAμM-1cm-2, respectively. The fabricated sensor also utilized for detection of H2O2 in the presence of potentially active interfering species, and found high selectivity towards H2O2.

A novel Laccase Biosensor based on Laccase immobilized Graphene-Cellulose Microfiber Composite modified Screen-Printed Carbon Electrode for Sensitive Determination of Catechol

In the present work, we demonstrate the fabrication of laccase biosensor to detect the catechol (CC) using laccase immobilized on graphene-cellulose microfibers (GR-CMF) composite modified screen printed carbon electrode (SPCE). The direct electrochemical behavior of laccase was investigated using laccase immobilized different modified SPCEs, such as GR/SPCE, CMF/SPCE and GR-CMF/SPCE. Compared with laccase immobilized GR and CMF modified SPCEs, a well-defined redox couple of CuI/CuII for laccase was observed at laccase immobilized GR-CMF composite modified SPCE. Cyclic voltammetry results show that the as-prepared biosensor has 7 folds higher catalytic activity with lower oxidation potential towards CC than SPCE modified with GR-CMF composite. Under optimized conditions, amperometric i-t method was used for the quantification of CC, and the amperometric response of the biosensor was linear over the concertation of CC ranging from 0.2 to 209.7 μM. The sensitivity, response time and the detection limit of the biosensor for CC is 0.932 μMμA−1 cm−2, 2 s and 0.085 μM, respectively. The biosensor has high selectivity towards CC in the presence of potentially active biomolecules and phenolic compounds. The biosensor also accessed for the detection of CC in different water samples and shows good practicality with an appropriate repea.

A Facile Electrochemical Preparation of Reduced Graphene Oxide@Polydopamine Composite: A Novel Electrochemical Sensing Platform for Amperometric Detection of Chlorpromazine

We report a novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode. The RGO@PDA composite was prepared by electrochemical reduction of graphene oxide (GO) with PDA. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behavior to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. Amperometric i-t method was used for the determination of CPZ. Amperometry result shows that the RGO@PDA composite detects CPZ in a linear range from 0.03 to 967.6 μM. The sensor exhibits a low detection limit of 0.0018 μM with the analytical sensitivity of 3.63 ± 0.3 μAμM–1 cm–2. The RGO@PDA composite shows its high selectivity towards CPZ in the presence of potentially interfering drugs such as metronidazole, phenobarbital, chlorpheniramine maleate, pyridoxine and riboflavin. In addition, the fabricated RGO@PDA modified electrode showed an appropriate recovery towards CPZ in the pharmaceutical tablets.

One pot electrochemical synthesis of poly(melamine) entrapped gold nanoparticles composite for sensitive and low level detection of catechol

A simple and cost effective synthesis of nanomaterials with advanced physical and chemical properties have received much attention to the researchers, and is of interest to the researchers from different disciplines. In the present work, we report a simple and one pot electrochemical synthesis of poly(melamine) entrapped gold nanoparticles (PM-AuNPs) composite. The PM-AuNPs composite was prepared by a single step electrochemical method, wherein the AuNPs and PM were simultaneously fabricated on the electrode surface. The as-prepared materials were characterized by various physicochemical methods. The PM-AuNPs composite modified electrode was used as an electrocatalyst for oxidation of catechol (CC) due to its well-defined redox behavior and enhanced electro-oxidation ability towards CC than other modified electrodes. Under optimized conditions, the differential pulse voltammetry (DPV) was used for the determination of CC. The DPV response of CC was linear over the concentration ranging from 0.5 to 175.5μM with a detection limit of 0.011μM. The PM-AuNPs composite modified electrode exhibits the high selectivity in the presence of range of potentially interfering compounds including dihydroxybenzene isomers. The sensor shows excellent practicality in CC containing water samples, which reveals the potential ability of PM-AuNPs composite modified electrode towards the determination of CC in real samples.

A highly sensitive and selective electrochemical determination of Hg(II) based on an electrochemically activated graphite modified screen-printed carbon electrode

A highly sensitive and selective Hg(II) sensor based on an electrochemically activated graphite (EAG) modified screen-printed carbon electrode (SPCE) was developed. The fabricated EAG modified SPCE showed an enhanced current (Ipa) response towards Hg(II) relative to that of a graphite SPCE, an activated SPCE and a bare SPCE. Under optimum conditions, the EAG modified SPCE showed a wider linear range at Hg(II) concentrations of 0.05–14.77 ppm. The limit of detection was calculated to be 4.6 ppb with a sensitivity of 81.5 μA ppm−1 cm−2. The World Health Organization and the United States Environmental Protection Agency recommend maximum contaminant levels of Hg(II) in drinking water of 30 and 10 ppb, respectively. Therefore, the observed limit of detection (4.6 ppb) is considerably below these guideline values for Hg(II) in drinking water. In addition, the EAG modified SPCE exhibits a high selectivity for the electrochemical detection of Hg(II) in the presence of other heavy metal ions.

Selective Colorimetric Detection of Nitrite in Water using Chitosan Stabilized Gold Nanoparticles Decorated Reduced Graphene oxide

Excess nitrite (NO2-) concentrations in water supplies is considered detrimental to the environment and human health, and is associated with incidence of stomach cancer. In this work, the authors describe a nitrite detection system based on the synthesis of gold nanoparticles (AuNPs) on reduced graphene oxide (rGO) using an aqueous solution of chitosan and succinic acid. The AuNPs-rGO nanocomposite was confirmed by different physicochemical characterization methods including transmission electron microscopy, elemental analysis, X-ray diffraction, UV-visible (UV-vis) and Fourier transform infrared spectroscopy. The AuNPs-rGO nanocomposite was applicable to the sensitive and selective detection of NO2− with increasing concentrations quantifiable by UV–vis spectroscopy and obvious to the naked eye. The color of the AuNPs-rGO nanocomposite changes from wine red to purple with the addition of different concertation of NO2−. Therefore, nitrite ion concentrations can be quantitatively detected using AuNPs-rGO sensor with UV-vis spectroscopy and estimated with the naked eye. The sensor is able to detect NO2− in a linear response ranging from 1 to 20 μM with a detection limit of 0.1 μM by spectrophotometric method. The as-prepared AuNPs-rGO nanocomposite shows appropriate selectivity towards NO2− in the presence of potentially interfering metal anions.

A sonochemical synthesis of cyclodextrin functionalized Au-FeNPs for colorimetric detection of Cr 6+ in different industrial waste water

This paper describes a simple, selective and sensitive colorimetric sensing of Cr6+ ions using β-Cyclodextrin (β-CD) functionalized gold-iron nanoparticles (β-CD/Au-FeNPs). The sonochemically synthesized nanoparticles are winered in colour due to the SPR band of β-CD functionalized bimetalic nanoparticles Au-FeNPs. The capping and stabilizing of Au-FeNPs by redox β-CD is confirmed by FT-IR. The particles are spherical in shape and it posses the effective diameter of 18-20 nm. Under optimized conditions, in the presence of Cr6+ the wine red Au-FeNPs solution was turned to colourless, accompanying the broadening and red shifting of SPR band. The ratio between the absorbance wavelength at 573 nm to 535 nm (A573/A535) is linearly correlated with the Cr6+ concentrations ranging from 50 nM to 500 nM, with a detection limit of Cr6+ of 2.5 nM was achieved for the first time using β-CD/Au-FeNPs by spectrophotometry. The selectivity of the β-CD/Au-FeNPs towards other interfering metal ions. Finally the proposed method has been successfully employed for the determination of Cr6+ ion in various industrial waste water with good recoveries.

Degradation of Methylene Blue Dye in the Presence of Visible Light Using SiO2@α-Fe2O3 Nanocomposites Deposited on SnS2 Flowers

Semiconductor materials have been shown to have good photocatalytic behavior and can be utilized for the photodegradation of organic pollutants. In this work, three-dimensional flower-like SnS2 (tin sulfide) was synthesized by a facile hydrothermal method. Core-shell structured SiO2@α-Fe2O3 nanocomposites were then deposited on the top of the SnS2 flowers. The as-synthesized nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis Spectroscopy, Brunauer–Emmett–Teller (BET) surface area analysis, and photoluminescence (PL) spectroscopy. The photocatalytic behavior of the SnS2-SiO2@α-Fe2O3 nanocomposites was investigated by observing the degradation of methylene blue (MB). The results show an effective enhancement of photocatalytic activity for the degradation of MB especially for the 15 wt % SiO2@α-Fe2O3 nanocomposites on SnS2 flowers.

A novel and Disposable Amperometric Hydrazine Sensor based on Polydimethyldiallylamine Stabilized Copper(II)hexacyanoferrate Nanocubes modified Screen- printed Carbon Electrode

© 2017 The Authors. A cubic shaped copper(II)hexacyanoferrate was prepared by wet chemical method by mixing an equimolar concentration of CuCl 2 with K 3 [Fe(CN) 6 ] 2 in the presence of poly(diallyldimethylammonium chloride) (PDDA). The X-ray diffraction, field emission scanning electron microscopy, elementa l analysis, Fourier transform infrared spectroscopy and thermal gravimetric analysis were used to confirm the formation of PDDA stabilized copper(II)hexacyanoferrate nanocubes (PDDA@copper(II)hexacyanoferrate nanocubes). The electrocatalytic behavior of the PDDA@copper(II)hexacyanoferrate nanocubes modified screenprinted carbon electrode (SPCE) towards electrochemical oxidation of hydrazine was studied by cyclic voltammetry (CV). The CV results revealed that PDDA@copper(II)hexacyanoferrate nanocubes modified SPCE exhibits an enhanced electrocatalytic activity and lower oxidation potential towards hydrazine than bare SPCE. Under optimized conditions, amperometric i-t method was used for the determination hydrazine, and PDDA@copper(II)hexacyanoferrate nanocubes modified SPCE can able to detect hydrazine in the linear concentration ranges from 0.03 to 533.6 μM with a detection limit of 10 nM. The PDDA@copper(II)hexacyanoferrate nanocubes modified SPCE is highly selective in the presence of potentially active interfering compounds including high concentration of ascorbic acid. In addition, the developed hydrazine sensor shows acceptable practicality with excellent long-term stability towards the detection of hydrazine.