Showing papers by "Neelakandapillai Sandhyarani published in 2019"

Surface modification methods for electrochemical biosensors

Abstract: Development of electrochemical biosensors with enhanced performance has gained increasing importance owing to their wide range of applications in various fields ranging from medical diagnostics and healthcare, environmental monitoring, and industrial manufacturing to defense and security. Major challenges associated with the development of biosensors are the attainment of high sensitivity, selectivity, reproducibility, and stability. In addition, the sensor surface should be stable for a longer period, and the interference from other analytes should be of the minimum. All these factors depend on the availability and reactivity of the immobilized biorecognition element, and hence suitable surface modification of the electrode is critical. Surface modifications lead to proper immobilization of biorecognition element, improvement of the signal to noise ratio, enhanced sensitivity, and prevention of nonspecific adsorption. Various surface modification technologies and immobilization strategies used in the electrochemical biosensors are explained in this chapter.

Nanosheets of nickel, cobalt and manganese triple hydroxides/oxyhydroxides as efficient electrode materials for asymmetrical supercapacitors.

Abstract: Transition metals play a significant role in energy storage applications mainly as electrode materials in supercapacitors. In this work, triple hydroxide/oxyhydroxide nanosheets of a nickel, cobalt and manganese (NCM) composite were electrochemically deposited on carbon cloth (CC) and used as electrode materials in supercapacitors. In a three electrode system the composite delivered a specific capacitance of 707 F g−1 at a current density of 3 A g−1 which retained its stability even at a higher current density of 50 A g−1. An asymmetric supercapacitor (ASC) was assembled and characterized using NCM as the positive electrode, activated carbon as the negative electrode and Whatman filter paper soaked in KOH as the separator. The device operated in a working potential window of 1.75 V and it delivered a power density of 13.12 kW kg−1 and an energy density of 23.7 W h kg−1.

1-Pyrene carboxylic acid functionalized carbon nanotube-gold nanoparticle nanocomposite for electrochemical sensing of dopamine and uric acid.

Abstract: A highly sensitive, selective and cost effective method is described for sensing dopamine (DA) and uric acid (UA). A glassy carbon electrode (GCE) was modified with a nanocomposite consisting of gold nanoparticle-loaded multi-walled carbon nanotube (CNT) modified with 1-pyrene carboxylic acid (PCA). The stable aqueous dispersion of non-covalently functionalized CNT-PCA is an efficient bioprobe for the ultra sensitive and selective detection of dopamine and uric acid in the presence of the potentially interfering agent ascorbic acid (AA). The presence of PCA on the CNT introduces anionic carboxyl groups which repel ascorbate. The presence of the pyrene group augments high electrocatalytic activity towards oxidation of DA and UA, and the gold nanoparticles contribute to the amplification of the signal. The modified GCE gives an excellent peak current with well distinguishable peaks for AA, DA and UA (near −0.08 V, +0.14 V, and +0.22 V vs Ag/AgCl) in differential pulse voltammetry. Chronoamperometric detection of DA (working potential of 0.16 V vs Ag/AgCl) and UA (working potential of 0.3 V vs Ag/AgCl) showed linear ranges of 1 nM-150 μM (LOD 1 nM) and 1 μM–240 μM (LOD 1 μM) for DA and UA, respectively. The nanoprobe was validated by monitoring the recovery of spiked DA and UA in human blood serum samples which indicated a recovery within ±2%.

Amorphous Rhenium Disulfide Nanosheets: A Methanol-Tolerant Transition Metal Dichalcogenide Catalyst for Oxygen Reduction Reaction

Abstract: A methanol tolerant catalyst for the reduction of oxygen is important for the effective utilization of direct methanol fuel cells (DMFCs). Herein, the synthesis of a layered transition metal dichalcogenide rhenium disulfide (ReS2) and its utilization as an effective novel precious metal free, methanol tolerant oxygen reduction catalyst is reported. A single step wet chemical synthesis procedure is used to synthesize ReS2, and morphological analysis revealed the formation of ultrathin nanosheets of thickness 1.6 nm. The catalytic activity of ReS2 toward the oxygen reduction reaction (ORR) was monitored in 0.1 M H2SO4, which showed higher current density and excellent stability comparable with the commercially available carbon supported platinum catalyst. The catalyst exhibited selective 4 electron transfer kinetics (n = 3.9) and has remarkable tolerance to methanol in contrast to platinum supported on carbon, which makes it promising as a Pt-free methanol tolerant ORR catalyst.

A graphitic carbon nitride–titania nanocomposite as a promising catalyst support for electro-oxidation of methanol

Abstract: The influence of catalyst support in the field of electrocatalysis is a fascinating area of materials research. The appropriate catalyst support can greatly enhance the catalytic activity of the catalyst either by reducing the activation energy of adsorption or by removing the byproduct of reaction. Here in this work, a graphitic carbon nitride–titania nanocomposite has been successfully synthesized through a facile, single step solvothermal treatment and employed as a catalyst support for electro-oxidation of methanol. The role of supporting catalyst in the electrocatalytic oxidation of methanol is evidenced by the increased mass activity of methanol oxidation reaction. The synergistic effects in the catalyst support arise from the versatile architecture of the composite and the presence of Ti–OH on the surface which assists in the oxidation and removal of adsorbed intermediates which poisons the platinum catalyst. The composite showed a high mass activity of 210 mA mg−1 at 1.03 V for methanol oxidation in acidic media which is higher than that of commercial Pt/C in the absence of catalyst support.

Ceria-based Mixed Oxide Nanoparticles for Diesel Engine Emission Control

Abstract: One of the effective methods for the control of harmful emissions from diesel engines is the use of fuel-borne catalyst. Ceria is commonly used as a redox catalyst, and the catalytic activity of ceria decreases due to particle sintering, especially at high temperatures. The catalytic activity of ceria nanoparticle can be improved by doping it with transition metals such as zirconium, yttrium. A comparative study on the catalytic activity and various physicochemical properties of CeyZr1−yO2, CeyY1−yO2, and CexZryY1−x−yO2 mixed oxide nanoparticles, synthesized by co-precipitation method, is presented in this chapter. The synthesized mixed oxide nanoparticles of ceria were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) analysis. The catalytic activity of ceria and its mixed oxide nanoparticles was compared by means of temperature-programmed reduction with H2 (H2-TPR) technique. The catalytic nanoparticle-dispersed diesel was prepared by mixing mixed oxide nanoparticles in diesel, with oleic acid as surfactant by means of ultrasonicator. Stability studies were done to optimize the concentration of catalytic nanoparticles in diesel for maximum stability. Engine studies on a four-stroke single-cylinder diesel engine show a reduction in the engine exhaust emissions, especially smoke, which agrees with the TPR study.