Balamurugan Devadas

Direct electrochemistry of glucose oxidase at electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid material modified electrode for glucose biosensor.

Direct electrochemistry of glucose oxidase (GOx) at an electrochemically reduced graphene oxide-multiwalled carbon nanotubes hybrid (ERGO-MWCNT) modified glassy carbon electrode (GCE) has been reported. The π-π stacking interaction operating between the MWCNT and graphene oxide (GO) has been revealed by UV-Vis absorption spectroscopy. GOx was well immobilized onto the ERGO-MWCNT hybrid film, as a result direct electrochemistry of GOx has been achieved. Compared with pristine MWCNT, 2.1 fold higher peak current and very low peak to peak separation (ΔE(p)) of 26 mV were observed at the hybrid film, demonstrating faster electron transfer between GOx and the modified electrode surface. Moreover, the modified film exhibited high electrocatalytic activity towards glucose via reductive detection of oxygen consumption and in the presence of mediator. The proposed biosensor exhibits low detection limit of 4.7 μM with wide linear range of 0.01-6.5mM and acquires excellent storage and operational stabilities. The accurate glucose determination in human blood serum and good recoveries achieved in spiked urine samples revealed their great potential in the practical applications.

Highly sensitive and selective determination of pyrazinamide at poly-L-methionine/reduced graphene oxide modified electrode by differential pulse voltammetry in human blood plasma and urine samples.

In this current study we used electrochemically active film which contains poly-L-methionine (PMET) and electrochemically reduced graphene oxide (ERGO) on glassy carbon electrode (GCE) for pyrazinamide (PZM) detection. The electrocatalytic response of analyte at PMET/ERGO/GCE film was measured using both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In addition, electrochemical impedance studies revealed that the smaller R(ct) value observed at PMET/ERGO film modified GCE which authenticates its good conductivity and faster electron transfer rate. The prepared PMET/ERGO/GCE film exhibits excellent DPV response towards PZM and the reduction peak current increased linearly with respect to PZM concentration in the linear range between 0.4 μM to 1129 μM with a sensitivity of 0.266 μA μM(-1) cm(-2). Real sample studies were carried out in human blood plasma and urine samples, which offered good recovery and revealed the promising practicality of the sensor for PZM detection. The proposed sensor displayed a good selectivity, repeatability, sensitivity with appreciable consistency and good reproducibility. In addition, the proposed electrochemical sensor showed good results towards the commercial pharmaceutical PZM samples.

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 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.

Electrochemical determination of selected antihypertensive and antituberculosis drugs at a tyrosine-modified electrode

A simple and sensitive electrochemical method was proposed for the determination of hydralazine hydrochloride (HDH), isoniazid (ISN), ethambutol hydrochloride (EBH) and pyrazinamide (PZM). For the first time, a tyrosine (Tyr)-modified glassy carbon electrode (GCE) was employed for the determination of HDH, ISN, PZM and EBH by the differential pulse voltammetric (DPV) technique. The proposed modified electrode showed strong electrocatalytic activity towards the above-mentioned drugs with a higher peak enhancement than that of an unmodified electrode. The practicality of the proposed electrode for the detection of HDH, ISN, PZM and EBH in human urine and blood serum samples was successfully demonstrated using the DPV technique. The applicability of the proposed method was verified with commercially available pharmaceutical tablets and the obtained results were in good agreement with the claimed label amounts of the tablets. From these results, it is clearly evident that the proposed electrode shows good catalytic activity towards HDH, ISN, PZM and EBH. In addition, this method could be used in the future for the accurate detection of HDH, ISN, PZM, and EBH in clinical and pharmaceutical industries.

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.

Controlled electrochemical synthesis of yttrium (III) hexacyanoferrate micro flowers and their composite with multiwalled carbon nanotubes, and its application for sensing catechin in tea samples

AbstractWe report the hierarchical growth of yttrium (III) hexacyanoferrate (YHCF), having a shape that resembles that of rose flower petals on a glassy carbon electrode (GCE) modified with functionalized multiwalled carbon nanotubes. The modified GCE displays excellent electrocatalytic activity toward catechin (CA) oxidation. The morphology and impedimetric response of YHCF were optimized by controlling the number of depositing cycles. As-synthesized YHCF micro flower was characterized by thin film X-ray diffraction (XRD) and infrared (IR) spectroscopic methods, respectively. By taking the advantage of a template-free, surfactant-less, and simple procedure, YHCF micro flowers have been prepared. The sensitivity and low detection limit of functionalized multiwalled carbon nanotube (fMWCNT)/YHCF/GCE toward CA are 1.311 μA μM−1 cm−2 and 0.28 μM, respectively. Moreover, the fabricated GCE exhibits sufficient recovery for CA determination in green tea and oolong tea samples. Graphical AbstractSchematic representation of electrochemical synthesis of YHCF microflower on fMWCNT modified GCE

Controlled electrochemical synthesis of new rare earth metal lutetium hexacyanoferrate on reduced graphene oxide and its application as a salicylic acid sensor

The hexangular star building-like lutetium hexacyanoferrate (LuHCF) structure with an average size of ca. 8.0 ± 0.5 μm was synthesized using a simple, one-step electrochemical method, and it was highly dispersed on to a reduced graphene oxide (RGO) modified glassy carbon electrode (GCE) support for the first time. The size and shape of the as-synthesized LuHCF micro stars were controlled by the deposition time. The LuHCF/RGO samples were characterized by a variety of analytical and spectroscopy techniques, viz. scanning electron microscopy (SEM), infra-red spectroscopy (IR), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In addition, LuHCF/RGO/GCE was adopted for the novel electrochemical detection of salicylic acid (SA) using cyclic voltammetry (CV) and amperometry methods. The charge transfer resistant value of LuHCF/RGO/GCE was smaller than LuHCF and bare GCE, which exhibit a remarkable electrocatalytic performance towards SA. Notably, the SA sensor was found to exhibit a lower detection limit and high sensitivity of ca. 0.49 μM and 77.2 μA mM-1 cm-2, respectively. The reported SA sensor possesses an excellent real time application with commercially purchased aspirin tablets and salic ointment (which contains salicylic acid). The excellent analytical parameters of the reported sensor, surpasses the previously reported modified electrodes, rendering practical industrial applications.

Novel poly-L-lysine/carboxyl-group enriched graphene oxide/modified electrode preparation, characterization and applications for the electrochemical determination of meloxicam in pharmaceutical tablets and blood serum

Electrochemical determination of meloxicam (MLC) was successfully determined at a poly-L-lysine (PLL)/carboxylated graphene oxide (GO–COOH)/modified glassy carbon electrode (GCE) by cyclic voltammetry (CV) and differential pulse voltammetric (DPV) techniques. The fabricated film characterizations were investigated by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and electrochemical impedance spectroscopy (EIS). The PLL/GO–COOH/GCE was employed for the electrocatalytic oxidation of MLC and the oxidation current of MLC significantly increased when compared to the bare GCE, which clearly shows that the modified electrode shows better electrocatalytic activity than the unmodified GCE. The linear range of the determination of MLC has to be 4 to 104 μM. The low limit of detection (LOD) and sensitivity was found as 0.87 μM and 0.228 μA μM−1 cm−2. The analytical performance of this proposed sensor has been evaluated in commercially available pharmaceutical tablets and the practicality of the proposed sensor further demonstrated in a real blood serum sample. The obtained results for commercially available tablets were almost equal to the labelled claim of the tablets; from these results it was clearly evident that the proposed electrode shows good catalytic activity towards MLC.