Muniyandi Rajkumar

In situ electrochemical synthesis of highly loaded zirconium nanoparticles decorated reduced graphene oxide for the selective determination of dopamine and paracetamol in presence of ascorbic acid

Highly loaded zirconium oxide (ZrO2) nanoparticles were supported on graphene oxide (ERGO/ZrO2) via an in situ, simple and clean strategy on the basis of the electrochemical redox reaction between zirconyl chloride and graphene oxide (ZrOCl2 and GO). The electrochemical measurements and surface morphology of the as prepared nanocomposite were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and field emission scanning electron microscopy (FESEM). This ZrO2 decorated reduced graphene oxide nanocomposite modified GCE (ERGO/ZrO2) exhibits a prominent electrocatalytic activity toward the selective detection and determination of dopamine (DA) and paracetamol (PA) in presence of ascorbic acid (AA). The peaks of linear sweep voltammetry (LSV) for DA and PA oxidation at ERGO/ZrO2 modified electrode surface were clearly separated from each other when they co-existed in the physiological pH (pH 7.0) with a potential value of 140 mV (between AA and DA) and 330 mV (between AA and PA). It was, therefore, possible to simultaneously determine DA and PA in the samples at ERGO/ZrO2 nanocomposite modified GCE. Linear calibration curves were obtained for 9-237 μM of PA and DA. The ERGO/ZrO2 nanocomposite electrode has been satisfactorily used for the determination of DA and PA in the presence of AA at pharmaceutical formulations in human urine samples with a linear range of 3-174 μM. The proposed biosensor shows a wide linear range, low detection limit, good reproducibility and acceptable stability, providing a biocompatible platform for bio sensing and bio catalysis.

Electrochemical detection of toxic ractopamine and salbutamol in pig meat and human urine samples by using poly taurine/zirconia nanoparticles modified electrodes

Detection of ractopamine and salbutamol has been developed by employing the facile synthesis of poly taurine/zirconia nanoparticles (ZrO2) modified film glassy carbon electrode. The poly taurine/ZrO2 nanoparticles were directly utilized for the detection of ractopamine and salbutamol using linear sweep voltammetry (LSV). The modified electrode successfully shows the oxidation peak for ractopamine adsorption at 0.65V and salbutamol at 0.71V, which is purely based on the detection of adsorption signals of ractopamine and salbutamol, at the electrode surface. Furthermore, the electrochemical measurements and surface morphology were studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) analysis. The modified electrode successfully detects the oxidation signals of ractopamine in the linear range of 1-28μM and salbutamol in the linear range of 5-220μM in laboratory samples. The proposed film also successfully detects the ractopamine signal (1-26μM) in pig meat samples and salbutamol signal (1-114μM) in human urine samples. It also exhibits two well-separated anodic oxidation peaks for uric acid and salbutamol in salbutamol-spiked human urine samples.

High electrocatalytic performance of platinum and manganese dioxide nanoparticle decorated reduced graphene oxide sheets for methanol electro-oxidation

In this study we report the synthesis of a novel Pt–MnO2–ERGO electrocatalyst by the deposition of MnO2 and Pt nanoparticles decorated on reduced graphene oxide sheets using a simple electrochemical method. The as prepared MnO2 and Pt nanoparticles decorated on the reduced graphene oxide sheets (Pt–MnO2–ERGO electrocatalysts) were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The cyclic voltammetric (CV), chronoamperometric and electrochemical impedance spectroscopic (EIS) measurements show high electrocatalytic activity and stability of the electrodes towards the methanol oxidation reaction in nitrogen saturated sulfuric acid aqueous solutions and in mixed sulfuric acid and methanol aqueous solutions. The voltammetric results show the electrocatalytic characteristics of the Pt–MnO2–ERGO electrocatalysts, which exhibit superior electrocatalytic activity (including good poison tolerance, and low onset potential) and stability toward electro-oxidation of methanol in a model reaction. The electrochemical impedance spectroscopic result shows good electrocatalytic activity in relation to methanol oxidation and improved tolerance of CO. In addition, the as designed Pt–MnO2–ERGO nanocomposite modified electrode with a novel structure can be directly employed for fuel cells.

Electropolymerization of curcumin on glassy carbon electrode and its electrocatalytic application for the voltammetric determination of epinephrine and p-acetoaminophenol.

Here in, we report the simultaneous voltammetric determination of epinephrine (EP) and p-acetoaminophenol (AP) on a poly curcumin (1,7 Bis ((4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5 dione), poly CM) modified glassy carbon electrode (GCE) for the first time. The CM was polymerized on to the GCE surface by simple electro polymerization process. A low peak to peak (ΔEp) separation of 60 mV was observed, indicating fast electron transfer between poly CM and the electrode surface. The electrochemical measurements and surface morphology of the as prepared poly CM film modified electrode were studied using cyclic voltammetry (CV), and field emission scanning electron microscopy (SEM), respectively. Moreover, poly CM modified GCE exhibits enhanced electro catalytic activity toward EP and AP in the linear range of 4.97-230.76 μM and 0.99-230.76 μM and with very low detection limit (LOD) of 0.05 μM and 0.1 μM. The sensitivity is 0.621 and 0.303 μAμM(-1)cm(2) for EP and AP, respectively. The practical feasibility of the proposed poly CM/GCE was evaluated in adrenaline injection (1 mg mL(-1)) solutions and paracetamol tablets for the simultaneous determination of EP and AP. We found maximum recovery of 99.2% for adrenaline injection and 97.4% for paracetamol tablets. Finally the modified electrode exhibit excellent repeatability, reproducibility and stability for the selective and simultaneous determination of EP and AP.

A promising photoelectrochemical sensor based on a ZnO particle decorated N-doped reduced graphene oxide modified electrode for simultaneous determination of catechol and hydroquinone

This paper describes the two-step synthesis of a nitrogen-doped reduced graphene oxide–ZnO (N-doped RGO–ZnO) nanocomposite and its photo electrochemical application. The novel photo electrochemical sensor fabricated from this ZnO–N-doped RGO nanocomposite exhibits superior performance over a glassy carbon or nitrogen-doped reduced GO nanocomposite for the simultaneous determination of hydroquinone (HQ) and catechol (CC). Cyclic voltammetry (CV) studies reveals that the N-doped RGO–ZnO electrode under optimal conditions shows a peak potential separation between HQ and CC of up to 112 mV in the presence of light, which is larger than an N-doped RGO electrode under the same conditions. Square wave voltammetry (SWV) studies of a system with co-existing HQ and CC show that the N-doped RGO–ZnO modified electrode exhibits a wide linear response range of 2–900 μM and 2–600 μM, respectively, with detection limits (S/N = 3) of 10 nM and 10 nM, respectively. The electrode also has good sensitivity, selectivity, high stability and reproducibility. This electrode sensor was further applied to determine HQ and CC in real samples with satisfactory results. The results demonstrate that the N-doped RGO–ZnO is a more robust and advanced carbon electrode material providing a promising platform for photo electrochemical sensors and photo electrocatalytic applications.

A novel voltammetric p-nitrophenol sensor based on ZrO2 nanoparticles incorporated into a multiwalled carbon nanotube modified glassy carbon electrode

Herein, we report the incorporation of zirconium oxide (ZrO2) nanoparticles into functionalized multiwalled carbon nanotubes (fMWCNTs/ZrO2) to form a nanocomposite film via a simple and clean in situ method based on the electrochemical redox reaction of zirconyl chloride (ZrOCl2). The electrocatalytic properties and surface morphology of the as-prepared nanocomposite were studied using cyclic voltammetry, electrochemical impedance spectroscopy and field emission scanning electron microscopy. The as-prepared fMWCNTs/ZrO2 nanocomposite-modified glassy carbon electrode shows a prominent electrocatalytic activity towards the voltammetric determination of p-nitrophenol. The presence of fMWCNTs in the film enhances the surface coverage concentration and also increases the electron transfer rate constant of the ZrO2 nanoparticles. The modified electrode has a linear range of 2–26 μM for p-nitrophenol. The proposed film was also used successfully for the voltammetric determination of p-nitrophenol in river and tap water samples with a linear range of 0–24 μM. A well-defined peak for the detection of p-nitrophenol in water samples has proved this fMWCNTs/ZrO2 nanocomposite-modified electrode to be a successful sensor material. The proposed film has long-term stability.

Investigation of morphologies and characterization of rare earth metal samarium hexacyanoferrate and its composite with surfactant intercalated graphene oxide for sensor applications

Herein, we report a facile electrochemical approach for the hierarchical growth of samarium hexacyanoferrate (SmHCF) on surfactant intercalated reduced graphene oxide (SRGO). The fabricated SRGO/SmHCF modified glassy carbon electrode (GCE) has excellent electrocatalytic activity towards catechol (CC) sensor applications. The sunflower-like SmHCF microparticles were achieved by controlling the number of cycles during the electrodeposition process. In addition, the electrolyte plays a key role in the morphology of SmHCF and was investigated using different electrochemical techniques. The as-prepared SmHCF microparticles were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. In addition, electrochemical impedance spectroscopy (EIS) was carried out to understand the mechanism of interfacial electrochemical reactions on the proposed SmHCF modified glassy carbon electrode (GCE). The obtained EIS data confirmed that the electron transfer rate at SmHCF/GCE was faster than bare GCE. The electrochemical detection of CC using the SRGO/SmHCF modified GCE was performed by cyclic voltammetry and difference pulse voltammetry. The fabricated modified GCE exhibits a good linear range from 50 μM to 250 μM, with a limit of detection (LOD) of 0.38 μM and a sensitivity of 0.430 μA μM−1 cm2 for the CC electrochemical sensor.

An enhanced direct electrochemistry of glucose oxidase at poly(taurine) modified glassy carbon electrode for glucose biosensor

A novel method for detecting glucose that employs glucose oxidase (GOx) at polytaurine (p-taurine)-modified glassy carbon electrode is reported. The polymerization of taurine was assessed by a simple electrochemical approach. The electro-polymerized p-taurine was confirmed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Notably, we obtained a good peak-to-peak separation (ΔEp) of 46 mV for p-taurine/GOx/Nf-modified GCE, indicating an excellent electron transfer process between GOx and the p-taurine-modified electrode. The fabricated composite p-taurine/GOx/Nf provides excellent electrocatalytic activity towards glucose detection. In this investigation, the glucose sensor has been achieved by reductive detection of oxygen consumption without a mediator. The detection of glucose was monitored using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained limit of detection (LOD) and sensitivity of the proposed glucose sensor were 0.06 mM and 26.58 μA−1 mM cm−2, respectively Moreover, the facile biosensor based on the Tau/GOx/Nf composite is preferred due to its simplicity, long-term stability, ultra high sensitivity, reliability, and durability, rendering practical applications even for real sample systems.