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The analysis of plasmonic photoelectrochemical reactions on nanostructured noble metal electrodes is an attractive field, but little is known about the detailed competition between the photochemica...

The economical, efficient and durable oxygen reduction catalysts facilitate the enhancement of electrochemical energy devices competitiveness towards widespread applications. In view of this, we provide an innovative sulfuration inducing method for the synthesis of ZnS and cobalt nanoparticles decorated N, S co-doped CNTs (ZnS/Co-NSCNTs) catalyst. S introduced into the zinc-based zeolitic imidazolate frameworks (ZIF-8) and cobalt-based zeolitic imidazolate frameworks (ZIF-67) precursors via pyrolysis, and induced the generation of ZnS/Co-NSCNTs have been confirmed by XRD, SEM, TEM, and XPS techniques. The key features including activity sites, transfer channels and adsorption energy back up the excellent electrocatalytic activity of the as-prepared ZnS/Co-NSCNTs towards oxygen reduction reactions (ORR). ZnS/Co-NSCNTs additionally exhibited a positive half-wave potential of 0.871 V (vs. RHE) with improved current density towards ORR. In alkaline medium, ZnS/Co-NSCNTs catalyst displayed a high tolerance towards methanol and an excellent long-term cycling stability. The observed onset potential for our prepared ZnS/Co-NSCNTs catalyst is analogous with the commercially available noble metal catalysts. Also, ZnS/Co-NSCNTs catalyst as a cathode in zinc-air battery displayed an enhanced electrochemical performance with a highly specific capacity of 750.1 mAh g−1, outstanding cycling stability, and high rate behavior. This work provides a new approach for the construction of stable low-cost alternative air-cathode catalysts for other energy conversion and storage applications.

Adsorption and chemical enhancement of p-methylbenzenethiol (PMBT) on silver and gold nanoparticle surfaces have been studied using surface enhanced Raman spectroscopy (SERS) and density functional...

Metal–organic frameworks (MOFs) are the more desirable electrode materials in the recent development of electrocatalyts. Still, the electrocatalytic behavior as well as the stability of the prepared MOFs were diminished by its poor conductance. In this work, Cobalt hydroxide (Co (OH)2) functionalized multi-walled carbon nanotubes (MWCNTs) with enhanced electro activity has been prepared using Co-based metal−organic framework (Co MOF, ZIF-67) templates through room temperature electrochemical synthesis. The as synthesized composite has been utilized in the construction of MWCNTs-Co(OH)2 modified glassy carbon electrode (GCE) for the determination of hydrazine (N2H4) and hydrogen peroxide (H2O2). The higher electrochemical performance of MWCNTs-Co(OH)2/GCE compared to individual MWCNTs/GCE and Co(OH)2/GCE was evident from the cyclic voltammetric studies. The characterizations of the composite have been carried out using various techniques. The electrochemical parameters such as linear range, limits of detection and sensitivity of MWCNTs-Co(OH)2/GCE were found to be more comparable with the previous N2H4 and H2O2 amperometric sensors reported in the literatures. The outcomes of practicability inspections were adequate with the recovery results of conventional methods. The high selectivity of MWCNTs-Co(OH)2 modified GCE towards N2H4 and H2O2 has been further demonstrated in the presence of several biologically interfering molecules.

Hydrogen peroxide (H2O2) sensing and oxygen reduction reaction (ORR) has considered to be a highly desirable in the areas of sensing and energy production. In recent years, researchers focus on the replacement of noble metal-based electrocatalyst used for the ORR and H2O2 sensing by low-cost materials. In this current work, we have synthesized carbon black supported LaMnO3 (LMO@C) via dry particle coating method and studied its electrocatalytic activity towards ORR and H2O2 sensing. The characterization of synthesized LMO@C was performed by using field emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy techniques. Furthermore, the synergistic effect between LMO and carbon was established through electrochemical measurements. In case of ORR, our prepared LMO@C composite possess longer life-time (89.8%) than 20 wt% Pt/C (77.6%). In another case, this electrocatalyst (LMO@C) owns wide working range, low limits of detection and high sensitivity for the determination of H2O2. The experimental data of LMO@C towards the electrochemical sensing of H2O2 and ORR demonstrates its potential applications in the construction of sensors and energy generation devices.

The synthesis of highly stable metallic organic–inorganic hybrid nanocomposites from the non-toxic and biodegradable organic–inorganic metallic precursors, which are the natural polymer products of organic molecules, carbohydrates, and amino acids, has engrossed the recent researchers. In this work, a simple potentiostatic approach has been designed for the electrochemical preparation of gold nanoparticle-decorated copper cross-linked pectin (CuCP–AuNPs). Here, CuCP act as a scaffold or stabilizing agent for the preparation of uniform AuNPs. The studies for surface morphology and crystal structure of our composite were carried out using field emission scanning electron microscopy (FESEM) and X-ray diffraction spectroscopy (XRD). Energy-dispersive X-ray spectroscopy (EDX) was employed for the elemental analysis of the composite. A remarkable cathodic peak current response was obtained by our modified electrode for the presence of H2O2. CuCP–AuNP-modified glassy carbon electrode (GCE) possesses the values for limits of detection (LOD) and sensitivity of 0.22 μΜ and 6800 μA mM cm−2, respectively, in a linear range from 1 to 2110 μΜ. The detection of H2O2 in presence of other biologically interfering molecules represents the high selectivity of our fabricated electrode. The examination for the sensitive determination of H2O2 conducted in commercially available lens cleaning solutions validates the practical feasibility of the proposed modified electrode.

An oxygen generator using Y-doped Bi2O3 as electrolyte to transport oxygen ions has been developed, having honeycomb-type structure with dimensions of 40 mm × 35 mm × 30 mm and consisting of 13 × 12 channels. External wire circuitry for the channels arrayed using parallel, series, and hybrid connection was evaluated to achieve the best oxygen separation efficiency. It was observed that the oxygen generator with hybrid connection facilitated evolution of oxygen at maximum of 117 sccm and high purity > 99.9% at 550°C under current flow of 14 A. Addition of 5 wt.% silane and 3 wt.% glass–ceramic powder to the Ag slurry used at both electrodes not only increased the coverage of the metal electrode on the ceramic substrate during dip coating but also prevented cracking at the electrode layer of the module under stress from the electric field and temperature during high-temperature operation, thus reducing the decay rate of the oxygen generator in durability testing.

We have synthesized the hierarchical mesoporous graphite oxide (HMGO) through simple single step carbonization method by using MIL-100(Al) metal-organic framework as a template. To study the influence of temperature in the synthesis of HMGO, various carbonization temperatures (700, 800, and 900 °C) were fixed without any additional carbon sources. The newly prepared HMGO showed uniform morphology, pore-size distribution centered on 10 nm with high surface area (370–470 m2/g) and excellent electrochemical ability. Hence, we have constructed an amperometric sensor for the trace level detection of caffeic acid (CA) by using HMGO as a modifier in glassy carbon electrode (GCE). The good electro catalytic activity of HMGO film modified GCE can be explained from the low over potential and high redox peak current obtained toward the detection of CA. Our demonstrated sensor works in a wide linear range (0.01–608 µM) with low limits of detection (0.004 µM) and high sensitivity (429 µA/mM/cm2). In addition, the selective determination of CA even in presence of other interfering molecules, reveals the good selectivity of HMGO/GCE. The commercially available wine samples were further utilized to demonstrate the practical feasibility of HMGO modified GCE. The acceptable values of stability, repeatability and reproducibility also support the practical applications of our fabricated electrode.

A novel, single step preparation of copper nanoparticles decorated silver nanoleaves (AgNLs–CuNPs) bimetallic composite at glassy carbon electrode (GCE) was done through electrochemical potentiostatic method. Three different morphologies namely, nanoparticles, nanodentrites and nanoparticles decorated nanoleaves were obtained for copper, silver and silver–copper as the result of deposition. Moreover, the obtained AgNLs–CuNPs composite is highly dense compared to their individuals. This was confirmed by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The crystal planes and elemental composition of the prepared nanocomposites were examined by X-ray diffraction (XRD) spectroscopy, Energy dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS). The highly dense AgNLs–CuNPs composite modified GCE showed a well-defined cathodic peak at −0.195 V towards H 2 O 2 . The cyclic voltammetry and amperometric studies revealed the excellent electrocatalytic ability of AgNLs–CuNPs/GCE towards the reduction of H 2 O 2 compared to only AgNDs and CuNPs. Remarkably, the fabricated AgNLs–CuNPs/GCE displayed a very low detection limit (0.095 μM) with high sensitivity (6190 μA mM −1 cm −2 ). Our demonstrated sensor holds good in a linear range from 0.5 to 1015 μM. Additionally, the selective determination of hydrogen peroxide was achieved using AgNLs–CuNPs/GCE even in the presence of other interfering biomolecules. The real sample analysis was performed in commercial clinical lens cleaning solutions to demonstrate the practicability of our sensor.

Manganese oxide nanoflakes incorporated functionalized multi-walled carbon nanotubes (f-MWCNTs/MnO2 NFs) have been prepared through a simple chemical method. The morphology and structure of the prepared composites were characterized by field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and X-ray photoelectron spectroscopy (XPS). Our present study demonstrated that enzymeless hydrogen peroxide sensor holds good in a wide linear range from 5 to 4530 μM with the calculated limits of detection and sensitivity values to be 0.952 μM and 219.05 μA mM−1, respectively. During hydrogen peroxide detection, f-MWCNT/MnO2 NF-modified glassy carbon electrode reached 95% of the steady-state response current within 4 s. In addition, our finding selectively detects hydrogen peroxide even in the presence of other interfering biomolecules. Ease of preparation, good electrocatalytic ability, and feasible practicality can potentially extend our fabricated electrode towards the applications of such biosensors and energy storage devices in the near future.

The authors describe an electrochemical approach for the preparation of a glassy carbon electrode (GCE) modified with graphene oxide and silver nanodentrites (AgNDs). The coating was obtained by using an aqueous solution containing silver nitrate, phosphate and ammonia. The phosphate anions act as a scaffold for the improved deposition of AgNDs. The effects of deposition potential and time and concentration of electrolyte on the formation of the AgNDs were optimized. The modified GCE displays good electrocatalytic activity towards the oxidation of dissolved hydrazine. The electron transfer coefficient and diffusion coefficient are 0.60 and 4.64 × 10−5 cm2 s−1 respectively. The electrode exhibits a linear response over the 100 nM to 670 μM hydrazine concentration range and a detection limit (LOD) of 33 nM. The sensitivity of the modified electrode is 2077 μA mM−1 cm−2 at a typical working voltage of 0.1 V (vs Ag/AgCl). This LOD is much lower than that of the allowable concentration of hydrazine in drinking water as defined by the US EPA and the WHO.

We delineate the electrochemical preparation of cobalt hydroxide nanoflakes Co(OH)2 NFs on multi-walled carbon nanotubes (MWCNTs) by potentiostatic methods. The preparation was done on the surface of glassy carbon electrode (GCE). The prepared nanocomposite was characterized by field emission scanning electron microscopy (FESEM), X-ray diffraction spectroscopy (XRD) and X-ray photo electron spectroscopy (XPS). The resulting f-MWCNTs/Co(OH)2 NFs modified GCE exhibits a good electrocatalytic activity for the oxidation of hydrazine in terms of decreasing over potential and increasing peak current. The modified electrode holds good in the linear range from 0.5 to 15.5 μM with limit of detection as 87.5 nM. The sensitivity of our modified electrode is calculated to be 5733 μA/mM cm-2. Remarkably, the obtained LOD value of our sensor is very lower compared to the recommended concentration of hydrazine in water by World health organization (WHO) and Environmental protective agency (EPA). The modified electrode detects hydrazine selectively even in the presence of common interferants. Various water samples were chosen to study the practical feasibility of our sensor. The sensor also exhibited an appreciable stability, repeatability and reproducibility.

Several nanomaterials and techniques for the detection of mercuric ions (Hg 2+ ) have been developed in the past decade. However, simple, low-cost and rapid sensor for the detection of heavy metal ions yet remains an important task. Herein, we present a highly sensitive electrochemical sensor for the femtomolar detection of Hg 2+ based on polypyrrole, pectin, and graphene (PPy/Pct/GR) which was prepared by one step electrochemical potentiodyanamic method. The effect of concentration of pectin, polypyrrole and graphene were studied for the detection of Hg 2+ . The influence of experimental parameters including effect of pH, accumulation time and accumulation potential were also studied. Different pulse anodic stripping voltammetry was chosen to detect Hg 2+ at PPy/Pct/GR/GCE modified electrode. The fabricated sensor achieved an excellent performance towards Hg 2+ detection such as higher sensitivity of 28.64 μA μM −1 and very low detection limit (LOD) of 4 fM at the signal to noise ratio of 3. The LOD of our sensor offered nearly 6 orders of magnitude lower than that of recommended concentration of Hg 2+ in drinking water by United States Environmental Protection Agency and World Health Organization. Compared to all previously reported electrochemical sensors towards Hg 2+ detection, our newly fabricated sensor attained a very LOD in the detection of Hg 2+ . The practicality of our proposed sensor for the detection of Hg 2+ was successfully demonstrated in untreated tap water.

This work presents a simple green approach for the chemical synthesis of cobalt oxide nano hexagons (Co3O4 NHs) with an average size of 160±40 nm incorporated graphene nanosheets (GR). The techniques used to confirm the formation of GR−Co3O4 NHs are transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction spectroscopy (XRD). The dopamine (DA) sensor was fabricated by drop casting GR−Co3O4 NHs on the pre-cleaned glassy carbon electrode (GCE). GR−Co3O4 modified GCE displayed a sensitive and selective electrochemical determination of DA compared to only GR and Co3O4 NHs modified GCE. Our fabricated sensor showed a wide linear range from 0.2 to 3443 μM with low limit of detection (84 nM) towards the determination of DA. The sensitivity of our fabricated sensor was calculated to be 108 μA mM−1 cm−2. As well, a significant storage stability, repeatability and reproducibility were attained by GR−Co3O4 NHs modified GCE. Human urine samples were targeted for the demonstration of practicality of our sensor.

β-cyclodextrin (β-CD) functionalized silver nanoparticles (AgNPs) and reduced graphene oxide (RGO) via one step electrochemical potentiodyanamic method has been prepared. Scanning electron microscopy, Energy-Dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the role of β-CD on preparation of AgNPs and RGO. RGO/β-CD/AgNPs modified GCE showed good electrochemical activity towards electro-oxidation of hydrazine in terms of decreasing the over potential and increasing the peak current. The kinetic parameters such as electron transfer coefficient (α) and diffusion coefficient (Do) of the modified electrode towards hydrazine were determined to be 0.66 and 0.97×10−6 cm2 s−1, respectively. The LOD of our sensor was many folds lower than that of recommended concentration of hydrazine in drinking water by United States Environmental Protection Agency and World Health Organization. The sensor exhibited a wide linear range from 0.08 to 1110 µM and a very low detection limit (LOD) of 1.4 nM. In addition, the sensor selectively determined hydrazine even in the presence of common interferents.

Plasmonic metal nanomaterials (PMNMs) have been targeted as noble photocatalysts in various energy related applications because of their strong surface plasmon resonance (SPR). It has been recently revealed that, these PMNMs on photoexcitation can induce the efficient hot carriers (hot electron/hole) transfer to the targeted molecules which is essential for the rate-limited process of photocatalysis. The profound understanding of reaction mechanisms is in need for the development of novel plasmonic catalysts towards chemical transformations of targeted molecules at PMNMs modified electrodes. The two diversely unique properties of electric field and electromagnetic field co-occur with different nanostructures in electrochemical surface enhanced Raman spectroscopy (EC-SERS) systems. Further, the EC-SERS experiments and their applications are deliberated from the construction of PMNMs coated electrodes for studying the SERS mechanisms and characterization of adsorption configuration and photoelectrochemical reaction mechanisms of targeted species. In this review, the recent investigation of the plasmon mediated photoelectrochemical transformation of para-aminothiophenol (PATP) at PMNMs modified electrodes will be discussed using EC-SERS method and theoretical calculations. The influence of applied potential, solution pH, and applied laser light power for binding and transformation of PATP at PMNMs will be discussed in detail. Ultimately, summary and future prospective of this study have been discussed briefly.

Bifunctional electrocatalysts to enable efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are essential for fabricating high performance metal–air batteries and fuel cells. Here, a defect rich nitrogen and sulfur co-doped graphene/iron carbide (NS-GR/Fe3C) nanocomposite as an electrocatalyst for ORR and OER is demonstrated. An ink of NS-GR/Fe3C is developed by homogeneously dispersing the catalyst in a Nafion containing solvent mixture using an ultrasonication bath (Model-DC150H; power − 150 W; frequency − 40 kHz). The ultrasonically prepared ink is used for preparing the electrode for electrochemical studies. In the case of ORR, the positive half-wave potential displayed by NS-GR/Fe3C is 0.859 V (vs. RHE) and for the OER, onset potential is 1.489 V (vs. RHE) with enhanced current density. The optimized NS–GR/Fe3C electrode exhibited excellent ORR/OER bifunctional activities, high methanol tolerance and excellent long-term cycling stability in an alkaline medium. The observed onset potential for NS–GR/Fe3C electrocatalyst is comparable with the commercial noble metal catalyst, thereby revealing one of the best low-cost alternative air–cathode catalysts for the energy conversion and storage application.

We describe a simple and elegant electropolymerization method to prepare highly stable tetraamino functionalized cobalt phthalocyanine (pTACoPc) at electrochemically reduced graphene oxide (RGO). The described method efficiently bridges the excellent physicochemical properties of RGO with the rich redox chemistry of TACoPc. Graphene oxide was electrochemically reduced to RGO at the electrode surface along with concominent electropolymerization of TACoPc. The electrochemical studies showed that RGO on pTACoP/GCE increased effective surface area, reduced charge transfer resistance and enhanced electrochemical signal. The RGO-pTACoPc film modified electrode exhibits excellent electrocatalytic ability to oxidize cysteine and hydrazine. To determine cysteine, the RGO-pTACoPc sensor displayed a linear concentration range of 50 nM to 2.0 μM, detection limit of 18.5 nM and sensitivity of 10.19 nA nM−1 cm−2. Besides, the sensor displayed a linear concentration range of 50 nM to 2.6 μM, detection limit of 10 nM and sensitivity of 1.62 nA nM−1 cm−2 to determine hydrazine. The electrocatalytic ability of RGO-pTACoPc shows better performance over other cobalt phthalocyanine derivatives. Furthermore, the described sensor exhibited long-term storage stability, good repeatability and reproducibility. The practical applicability of the sensor has been assessed in biological and water samples.

Herein, we have demonstrated a preparation of palladium nanoparticles on electroactivated graphite nanosheets modified screen printed carbon electrode (PdNPs-EGNS/SPCE) by a simple electrochemical method. The well-prepared electrocatalyst was potentially applied to the high performance electrocatalytic oxidation of hydrazine in neutral medium. The PdNPs-EGNS novel composite was characterized by scanning electron microscope (SEM) and the average diameter and thickness of PdNPs and EGNS were found to be ∼38 nm and 85 nm, respectively. The high performance electrocatalytic determination of hydrazine was performed by the amperometric i-t method. The fabricated sensor displayed irreversible electrocatalytic oxidation of hydrazine with diffusion-controlled electrode process. The oxidation of hydrazine at PdNPs-EGNS/SPCE showed wider linear range 0.05–1415 µM and high sensitivity 4.382 µA µM−1 cm−2. The as-prepared electrocatalyst achieved quick response towards hydrazine with a lower detection limit 4 nM.

A simple electrodeposition approach has been described for the preparation of copper nanoparticles (CuNPs) using biopolymer pectin as a scaffold and graphene as a support. The formation of graphene/pectin-CuNPs was confirmed by scanning electron microscopy, UV-Visible spectroscopy and X-ray diffraction studies. The graphene/pectin-CuNPs film modified electrode was prepared and its electrocatalytic applications to the oxidation of glucose and reduction of H2O2 have been explored. An amperometric glucose sensor was fabricated which exhibited excellent sensor performance in terms of wide linear range (10 μM–5.5 mM), low detection limit (2.1 μM) and high sensitivity (0.0457 μAμM−1 cm−2). Likewise, an amperometric sensor has been fabricated for the determination of H2O2 which displayed linear range of 1 μM–1 mM, detection limit of 0.35 μM and sensitivity of 0.391 μAμM−1 cm−2. The sensor displayed appreciable repeatability, reproducibity and stability. Furthermore, practical feasibility of the sensor has been demonstrated in human serum and contact lens cleaning solution to determine glucose and H2O2, respectively. The main advantages of sensor include simple and green fabrication approach, roughed and stable electrode matrix, high sensitivity and stability, fast in sensing and highly reproducible.

We describe the electrochemical preparation of bismuth nanoribbons (Bi-NRs) with an average length of 100 ± 50 nm and a width of 10 ± 5 μm by a potentiostatic method. The process occurs on the surface of a glassy carbon electrode (GCE) in the presence of disodium ethylene diamine tetraacetate that acts as a scaffold for the growth of the Bi-NRs and also renders them more stable. The method was applied to the preparation of Bi-NRs incorporated into reduced graphene oxide. This nanocomposite was loaded with the enzyme glucose oxidase onto a glassy carbon electrode. The resulting biosensor displays an enhanced redox peak for the enzyme with a peak-to-peak separation of about 28 mV, revealing a fast electron transfer at the modified electrode. The loading of the GCE with electroactive GOx was calculated to be 8.54 × 10−10 mol∙cm−2, and the electron transfer rate constant is 4.40 s−1. Glucose can be determined (in the presence of oxygen) at a relatively working potential of −0.46 V (vs. Ag|AgCl) in the 0.5 to 6 mM concentration range, with a 104 μM lower detection limit. The sensor also displays appreciable repeatability, reproducibility and remarkable stability. It was successfully applied to the determination of glucose in human serum samples.

We have described the fabrication of high-performance amperometric sensors derived from graphene oxide–multiwalled carbon nanotube (GO–MWCNT) composite for the sensitive determination of diuron and fenuron. GO–MWCNT composite was prepared by simple solution-based approach, and its formation was confirmed by scanning electron microscopy, transmission electron microscopy and UV-visible spectroscopy methods. GO–MWCNT film-modified glassy carbon electrode exhibited excellent electrocatalytic performance in the oxidation of diuron and fenuron in terms of less overpotential and highly enhanced peak currents. GO–MWCNTs have presented significantly improved electrocatalytic performance than dimethylformamide-dispersed MWCNTs. GO–MWCNT-based amperometric sensor has been fabricated which detects diuron in wide linear range between 9 μM and 0.38 mM with high sensitivity of 0.645 μA μM−1 cm−2. The amperometric sensor also detects fenuron in broad linear range between 0.9 and 47 μM with sensitivity of 1.20 μA μM−1 cm−2. Moreover, the sensor offers appreciable repeatability, reproducibility, and stability results. Practical feasibility of the prepared amperometric sensor has been assessed in various water samples collected from agricultural areas.

Hydrazines are well-known for their diverse biological properties but especially for their toxicity. An amperometric hydrazine sensor was developed at multi-walled carbon nanotubes (MWCNT) and iron tetrasulfonated phthalocyanine (FeTsPc) composite modified electrode for the first time. The TEM and UV-Vis spectroscopy results revealed the successful formation of MWCNT/FeTsPc composite. Compared with the response of MWCNT and FeTsPc modified electrodes, the MWCNT/FeTsPc composite showed enhanced oxidation current response with lower overpotential for hydrazine. Under optimum conditions, the amperometric i–t response of hydrazine was linear in the concentration range from 100 nM L−1 to 3 μM L−1 with the detection limit of 7.6 nM L−1. The response time of hydrazine was found as 6 s with a high sensitivity of 7.615 μA/μM L−1 cm−2.

We prepared graphene (GR)-cobalt phthalocyanine (CoPc) and GR-iron phthalocyanine (FePc) composites by simple and facile chemical reduction method for enzymatic fuel cell (EFC) applications. The successful formation of the composites was confirmed by scanning electron microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction and electrochemical methods. The as-prepared composites were used for the construction of glucose/O2 EFC. The anode of the EFC was prepared by immobilizing glucose oxidase (GOx) at the GR-CoPc composite modified glassy carbon electrode (GCE). GCE/GR-CoPc/GOx exhibited excellent electrocatalytic ability towards oxidation of glucose. In addition, the modified electrode showed appreciable stability, repeatability and reproducibility. GR-FePc composite exhibited superior electrocatalytic ability towards oxygen reduction reaction (ORR). A membraneless glucose/O2 EFC has been fabricated employing GCE/GR-CoPc/GOx and GCE/GR-FePc as anode and cathode respectively. The fabricated EFC offered a maximum power density of 23 μW cm−2 which is comparable with the previously reported EFCs and it exhibited appreciable stability and repeatability. From this study, we infer that GR based MPcs have great potential for the fabrication of EFCs.

In the present study, a simple and sensitive amperometric enzyme-free glucose sensor was developed at a multiwalled carbon nanotube and cobalt tetrasulfonated phthalocyanine (MWCNT–CoTsPc) modified electrode. The morphology of the fabricated composite was characterized and confirmed by transmission electron microscopy and UV-Vis spectroscopy. UV-Vis spectroscopy results confirmed that the MWCNT–CoTsPc composite was formed via the strong π–π interaction between CoTsPc and MWCNT. Compared with pristine CoTsPc, the MWCNT–CoTsPc composite modified electrode showed a higher electrocatalytic activity and lower overpotential towards the oxidation of glucose. Amperometric i–t technique was used for the determination of glucose. The response of glucose was linear over the concentration ranging from 10 μM to 6.34 mM with a sensitivity of 122.5 μA mM−1 cm−2. The response time of the sensor was determined to be 2 s with a limit of detection of 0.14 μM (S/N = 3). The fabricated sensor also exhibited a good selectivity in the presence of common interfering species. In addition, the fabricated sensor exhibited special advantages, such as low working potential, good sensitivity along with good repeatability and reproducibility, for the determination of glucose.

The nickel tetrasulfonated phthalocyanine (NiTsPc) functionalized multiwalled carbon nanotube (MWCNT) nanocomposite was prepared by a simple so- nochemical method. Here, NiTsPc served as a dispersing agent for MWCNT via pp interaction between MWCNT and NiTsPc. The activated glassy carbon elec- trode (AGCE) modified with MWCNT-NiTsPc composite exhibited a good electrocatalytic ability toward dopamine and displayed a good linear dependence in the concentra- tion range of 20 nM-1.384 mM with a sensitivity of 0.17 mA mM � 1 cm � 2 . The detection limit is 1 nM based on the signal-to-noise ratio of 3.

We describe a glassy carbon electrode (GCE) modified with gold nanoparticles that were stabilized with calcium-crosslinked pectin (CCLP) and electrodeposited on multiwalled carbon nanotubes (MWCNTs) by cyclic voltammetry. The resulting electrode was used for the selective determination of L-cysteine (L-Cys). Its characterization showed that the CCLP acts as a scaffold to form highly stable, uniform and electrochemically active AuNPs. Electrochemical studies showed the MWCNT to significantly promote the electrodeposition of the CCLP-AuNPs. The new GCE exhibited excellent electrocatalytic ability towards oxidation of L-Cys in showing a lower overpotential and giving a higher oxidation peak current. The diffusion coefficient for the oxidation of L-Cys was calculated to be 3.0 × 10−6 cm2 s−1. This amperometric sensor displays a wide linear range (from 0.1 to 1,000 μM), high sensitivity (0.46 μA μM−1 cm−2) and a detection limit as low as 19 nM (at a signal-to-noise ratio of 3). The sensor was applied to specifically detect L-Cys even in the presence of 500-fold excess of interferents. It also is stable and possesses good repeatability and reproducibity, and was successfully applied to the determination of L-Cys in spiked samples of human serum.

A simple electrochemical deposition strategy is proposed for the preparation of gold nanoparticles (Au NPs) at the electrode surface using biopolymer pectin as stabilizing agent. The formation of the nanoparticles was confirmed by scanning electron microscopy (SEM), UV-visible spectroscopy and X-ray diffraction (XRD) studies. A pectin-stabilized, gold nanoparticle film-modified glassy carbon electrode (pectin–Au NP/GCE) was prepared, which exhibited excellent electrocatalytic ability towards oxidation of dopamine (DA). At the pectin–Au NP/GCE, the redox couple corresponding to the redox reaction of DA was observed at the formal potential of 0.20 V with highly enhanced peak currents. A thin layer of nafion coating was applied on the pectin–Au NP composite to improve its selectivity. Two linear ranges of detection were found: (1) 20 nM to 0.9 μM with a limit of detection (LOD) of 6.1 nM, (2) 0.9 μM to 1 mM with a LOD of 0.64 μM. The fabricated sensor selectively detects DA even in the presence of high concentrations of interferents. Moreover, practical feasibility of the sensor was addressed in pharmaceutical samples, which presented appreciable recovery results. The main advantages of the sensor are its very simple and green fabrication approach, roughed and stable structure, and fast and highly reproducible detection of dopamine.

We have described a hybrid material that consists of molybdenum disulfide nanosheets (MoS 2 ) coated on functionalized multiwalled carbon nanotubes ( f -MWCNTs) for sensitive and selective determination of chloramphenicol (CAP). The MoS 2 / f -MWCNTs nanocomposite was successfully prepared through a hydrothermal process and its structure was characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The MoS 2 / f -MWCNTs nanocomposite holds excellent electrochemical properties and it displays excellent electrocatalytic ability to CAP. Under optimized working conditions, the nanocomposite film modified electrode responds linearly to CAP in the concentration range of 0.08–1392 μM. The detection limit was obtained as 0.015 μM (±0.003). The electrode has high level of selectivity in presence of large excess concentrations of interfering species. In addition, the modified electrode offers satisfactory repeatability, reproducibility and stability. The practical applicability of the electrode was demonstrated in food samples such as, milk, powdered milk and honey samples and the recoveries are agreeable which clearly revealed its practical feasibility in food analysis.

A simple and rapid green synthesis using Bischofia javanica Blume leaves as reducing agent was developed for the preparation of gold nanoparticles (AuNPs). AuNPs decorated graphene oxide (AuNPs/GO) was prepared and employed for the sensitive amperometric determination of chloramphenicol. The green biosynthesis requires less than 40s to reduce gold salts to AuNPs. The formations of AuNPs and AuNPs/GO were evaluated by scanning electron and atomic force microscopies, UV-Visible and energy dispersive X-ray spectroscopies, X-ray diffraction studies, and electrochemical methods. AuNPs/GO composite film modified electrode was fabricated and shown excellent electrocatalytic ability towards chloramphenicol. Under optimal conditions, the amperometric sensing platform has delivered wide linear range of 1.5-2.95μM, low detection limit of 0.25μM and high sensitivity of 3.81μAμM(-1)cm(-2). The developed sensor exhibited good repeatability and reproducibility, anti-interference ability and long-term storage stability. Practical feasibility of the sensor has been demonstrated in food samples (milk, powdered milk and honey) and pharmaceutical sample (eye drops). The green synthesized AuNPs/GO composite has great potential for analysis of food samples in food safety measures.

Copper nanoparticles with the diameter of 50 &plusmn, 20 nm decorated nitrogen doped graphite oxide (NGO) have been prepared through a simple single step carbonization method using copper metal-organic framework (MOF), [Cu2(BDC)2(DABCO)] (where BDC is 1,4-benzenedicarboxylate, and DABCO is 1,4-Diazabicyclo[2.2.2]octane) as precursor. The surface morphology, porosity, surface area and elemental composition of CuNPs/NGO were characterized by various techniques. The as-synthesized CuNPs/NGO nanomaterials were coated on commercially available disposable screen-printed carbon electrode for the sensitive determination of glucose. We find that the modified electrode can detect glucose between 1 &mu, M and 1803 &mu, M (linear range) with good sensitivity (2500 &mu, A mM&minus, 1 cm&minus, 2). Our glucose sensor also possesses low limits of detection (0.44 &mu, M) towards glucose determination. The highly selective nature of the fabricated electrode was clearly visible from the selectivity studies. The practicability of CuNPs/NGO modified electrode has been validated in the human serum samples. The storage stability along with better repeatability and reproducibility results additionally substantiate the superior electrocatalytic activity of our constructed sensor towards glucose.

Biopolymer pectin stabilized gold nanoparticles were prepared at graphene and multiwalled carbon nanotubes (GR-MWNTs/AuNPs) and employed for the determination of glucose. The formation of GR-MWNTs/AuNPs was confirmed by scanning electron microscopy, X-ray diffraction, UV–vis and FTIR spectroscopy methods. Glucose oxidase (GOx) was successfully immobilized on GR-MWNTs/AuNPs film and direct electron transfer of GOx was investigated. GOx exhibits highly enhanced redox peaks with formal potential of −0.40 V (vs. Ag/AgCl). The amount of electroactive GOx and electron transfer rate constant were found to be 10.5 × 10−10 mol cm−2 and 3.36 s−1, respectively, which were significantly larger than the previous reports. The fabricated amperometric glucose biosensor sensitively detects glucose and showed two linear ranges: (1) 10 μM – 2 mM with LOD of 4.1 μM, (2) 2 mM – 5.2 mM with LOD of 0.95 mM. The comparison of the biosensor performance with reported sensors reveals the significant improvement in overall sensor performance. Moreover, the biosensor exhibited appreciable stability, repeatability, reproducibility and practicality. The other advantages of the fabricated biosensor are simple and green fabrication approach, roughed and stable electrode surface, fast in sensing and highly reproducible.

We described a simple and facile chemical reduction strategy for the preparation of graphene (GR)-cobalt phthalocyanine (CoPc) composite and explored it for the enzymatic determination of glucose. CoPc is an active mediator and electrocatalysts for the immobilization of GOx and determination of glucose. However, it is not stable on the electrode surface and also suffers from lack of conductivity. Here, we have employed GR as the suitable support to stabilize CoPc through simple chemical reduction method and the resulting composite has been used for the glucose biosensor application. Scanning electron microscopy, X-ray diffraction and Energy-dispersive X-ray spectroscopy studies confirmed the successful formation of composite. Direct electron transfer of glucose oxidase (GOx) was observed with well defined redox peaks at the formal potential of -0.44 V. The amount of electroactive GOx (Г) and electron transfer rate constant (ks) were calculated to be 3.77×10(-10) mol cm(-2) and 3.57 s(-1), respectively. The fabricated amperometric biosensor detects glucose in wide linear concentration range from 10 μM to 14.8 mM with high sensitivity of 5.0 9μA mM(-1) cm(-2). The sensor offered very low detection limit (LOD) of 1.6 μM. In addition, practical feasibility of the sensor has been explored in screen printing carbon electrode with accurate determination of glucose present in human blood serum and urine samples. Furthermore, the sensor exhibited appreciable stability, repeatability and reproducibility results.