Electrochemical detection of sulfanilamide using tannic acid exfoliated MoS2 nanosheets combined with reduced graphene oxide/graphite.

Sulfonamides are a family of synthetic drugs with a broad-spectrum of antimicrobial activity. Like other antimicrobials, they have been found in aquatic environments, making their detection important. Herein, an electrochemical sensor was designed using tannic acid exfoliated few-layered MoS2 sheets, which were combined with a mixture of reduced graphene oxide (rGO) and graphite flakes (G). The rGO/G was formed using electrodeposition, by cycling from -0.5 to -1.5 V in an acidified sulfate solution with well dispersed GO and G. The exfoliated MoS2 sheets were drop cast over the wrinkled rGO/G surface to form the final sensor, GCE/rGO/G/ta-MoS2. The mixture of rGO/G was superior to pure rGO in formulating the sensor. The fabricated sensor exhibited an extended linear range from 0.1 to 566 µM, with a LOD of 86 nM, with good selectivity in the presence of various salts found in water and structurally related drugs from the sulfonamide family. The sensor showed very good reproducibility with the RSD at 0.48 %, repeatability and acceptable long term stability over a 10-day period. Good recovery from both tap and river water was achieved, with recovery ranging from 90.4 to 98.9 % for tap water and from 83.5 to 94.4 % for real river water samples.

Development of an Amorphous Nickel Boride/Manganese Molybdate Heterostructure as an Efficient Electrode Material for a High-Performance Asymmetric Supercapacitor.

The exploration of heterostructure materials with unique electronic properties is considered a desirable platform for fabricating electrode/surface interface relationships for constructing asymmetric supercapacitors (ASCs) with high energy density. In this work, a heterostructure based on amorphous nickel boride (NiXB) and crystalline square bar-like manganese molybdate (MnMoO4) was prepared by a simple synthesis strategy. The formation of the NiXB/MnMoO4 hybrid was confirmed by powder X-ray diffraction (p-XRD), field emission scanning electron microscopy (FE-SEM), field-emission transmission electron microscopy (FE-TEM), Brunauer-Emmett-Teller (BET), Raman, and X-ray photoelectron spectroscopy (XPS). In this hybrid system (NiXB/MnMoO4), the intact combination of NiXB and MnMoO4 leads to a large surface area with open porous channels and abundant crystalline/amorphous interfaces with a tunable electronic structure. This NiXB/MnMoO4 hybrid shows high specific capacitance (587.4 F g-1) at 1 A g-1, and it even retains a capacitance of 442.2 F g-1 at 10 A g-1, indicating superior electrochemical performance. The fabricated NiXB/MnMoO4 hybrid electrode also exhibited an excellent capacity retention of 124.4% (10000 cycles) and a Coulombic efficiency of 99.8% at a current density of 10 A g-1. In addition, the ASC device (NiXB/MnMoO4//activated carbon) achieved a specific capacitance of 104 F g-1 at 1 A g-1 and delivered a high energy density of 32.5 Wh.kg-1 with a power density of 750 W·kg-1. This exceptional electrochemical behavior is due to the ordered porous architecture and the strong synergistic effect of NiXB and MnMoO4, which enhances the accessibility and adsorption of OH- ions that improve electron transport. Moreover, the NiXB/MnMoO4//AC device exhibits excellent cyclic stability with a retention of 83.4% of the original capacitance after 10000 cycles, which is due to the heterojunction layer between NiXB and MnMoO4 that can improve the surface wettability without causing structural changes. Our results show that the metal boride/molybdate-based heterostructure is a new category of high-performance and promising material for the growth of advanced energy storage devices.

Design and synthesis of nickel-doped cobalt molybdate microrods: An effective electrocatalyst for the determination of antibiotic drug ronidazole.

Ronidazole (RDZ) is a veterinary antibiotic drug that has been used in animal husbandry as feed. However, improper disposal and illegal use of pharmaceuticals have severely polluted water resources. Doping/substitution of metal ions is an effective strategy to change the material's crystal phase, morphology, and electrocatalytic activity. In this work, nickel (Ni2+)-doped cobalt molybdate microrods (NCMO MRs) were prepared for the electrochemical detection of RDZ. The catalyst was prepared by reflux method followed by calcination at 500 °C. The prepared catalyst was confirmed by various spectroscopic and microscopic analyses. XRD and Raman spectroscopy demonstrated that the phase transition from ß-CoMoO4 to α-CoMoO4 was achieved by Ni2+ doping. The SEM analysis showed that cobalt molybdate (CMO) microrods were self-assembled during Ni2+ doping and formed an urchin-like structure, and the average diameter of the MRs was ±50 nm. The electrocatalytic activity of the catalysts was analyzed using the CV technique. The NCMO MRs/GCE exhibited the higher current response than the pristine CMO. The electron transfer coefficient (α = 0.56) and heterogeneous rate constant (ks = 0.32 s-1) of NCMO MRs/GCE were evaluated by kinetic studies. In addition, the diffusion coefficient of RDZ was determined to be 2.32 × 10-5 cm2/s. Moreover, NCMO MRs/GCE exhibits a low detection limit for RDZ (15 nM) as well as a higher sensitivity (1.57 µA µM-1 cm-2). The fabricated RDZ sensor was successfully applied to analysis of lake and tap water samples. Based on the results, we believe that the as-prepared NCMO MRs/GCE is a viable electrode material for RDZ sensors in environmental monitoring.

Effect of bismuth doping on zircon-type gadolinium vanadate: Effective electrocatalyst for determination of hazardous herbicide mesotrione.

Pesticides are used to promote the growth of plants and crops by killing weeds and other pests. On the other hand, overused and unused pesticides can leach into groundwater and agricultural lands, easily contaminating water, air, and soil resources. Doping with metal ions is an effective method to improve the catalytic activity of potential electrode materials. In the present study, an electrochemical sensor based on Bi3+-doped gadolinium vanadate nanoparticles (GVB NPs) was fabricated for sensitive and selective detection of harmful pesticide mesotrione (MST). The crystalline nature, functional groups, and elemental composition of the prepared electrocatalysts were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. Field-emission scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HR-TEM) showed that the undoped gadolinium vanadate had a rice-like nanostructure and was designated as GV NRs, while GVB had the morphology of nanoparticles. The fabricated electrode exhibited a well-resolved MST reduction peak in cyclic voltammetry and linear sweep voltammetry (LSV). Bismuth doping effectively enhanced the MST reduction and produced a stronger cathodic current response than bare and GV NRs-modified GCE. Moreover, GVB NPs/GCE show a nanomolar detection limit of 45 nM with a sensitivity of 0.43 µA µM-1 cm-2. The proposed sensor showed good repeatability, reproducibility, and stability in LSV analysis. The fabricated MST sensor was successfully applied to the analysis of real samples (river water and corn) with good recovery results.

Raspberry-like CuWO4 hollow spheres anchored on sulfur-doped g-C3N4 composite: An efficient electrocatalyst for selective electrochemical detection of antibiotic drug nitrofurazone.

We report a highly selective and sensitive electrochemical sensor for the determination of nitrofurazone (NZ) based on sulfur-doped graphitic carbon nitride with copper tungstate hollow spheres (Sg-C3N4/CuWO4). Here, a Sg-C3N4/CuWO4 composite was synthesized by a facile ultrasonic method. The physicochemical properties of the composite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). Then, the surface morphology of the composite material was investigated by field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM). Moreover, the electrochemical activity of the as-synthesized composite material was initially tested using electrochemical impedance spectroscopy (EIS). The electroanalytical techniques namely cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were carried out for the electrochemical studies. The proposed sensor exhibits lower LOD and good sensitivity of about 3 nM and 1.24 µAµM-1 cm-2 to NZ detection. In addition, the Sg-C3N4/CuWO4 modified electrode showed excellent repeatability, reproducibility, long-term storage stability and excellent selectivity. The developed sensor was successfully applied for the determination of NZ in human urine and serum samples and achieved good recovery results.

Synthesis and Characterization of Pyrochlore-Type Praseodymium Stannate Nanoparticles: An Effective Electrocatalyst for Detection of Nitrofurazone Drug in Biological Samples.

Apart from perovskites, the development of different types of pyrochlore oxides is highly focused on various electrochemical applications in recent times. Based on this, we have synthesized pyrochlore-type praseodymium stannate nanoparticles (Pr2Sn2O7 NPs) by using a coprecipitation method and further investigated by different analytical and spectroscopic techniques such as X-ray diffraction, Raman spectroscopy, field emission-scanning electron microscopy, high resolution-transmission electron microscopy, and X-ray photoelectron spectroscopy analysis. Followed by this, we have designed a unique and novel electrochemical sensor for nitrofurazone detection, by modifying the glassy carbon electrode (GCE) with the prepared Pr2Sn2O7 NPs. For that, the electrochemical experiments were performed by using cyclic voltammetry and differential pulse voltammetry techniques. The Pr2Sn2O7 NPs modified GCE exhibits high sensitivity (2.11 µA µM-1 cm-2), selectivity, dynamic linear ranges (0.01-24 µM and 32-332 µM), and lower detection limit (4 nM). Furthermore, the Pr2Sn2O7 NPs demonstrated promising real sample analysis with good recovery results in biological samples (human urine and blood serum) which showed better results than the noble metal catalysts. Based on these results, the present work gives clear evidence that the pyrochlore oxides are highly suitable electrode materials for performing outstanding catalytic activity toward electrochemical sensors.

Ultrasound treated cerium oxide/tin oxide (CeO2/SnO2) nanocatalyst: A feasible approach and enhanced electrode material for sensing of anti-inflammatory drug 5-aminosalicylic acid in biological samples.

In this work, we developed cerium oxide/tin oxide (CeO2/SnO2) nanocatalyst with the assistance of urea by a simple sonochemical method and utilized as an efficient electrode material for electrochemical sensing of anti-inflammatory drug 5-aminosalicylic acid (Mesalamine, MES). The CeO2/SnO2 nanoparticles (NPs) were systematically characterized in terms of their crystal structure, morphologies, and physicochemical properties using XRD, Raman, FESEM, HR-TEM, EDX, mapping, and XPS analysis. The characterization results clearly confirmed that the prepared NPs was formed in the phase of CeO2/SnO2 without any other impurities. The electrochemical properties of CeO2/SnO2 NPs were investigated by EIS, CV, and DPV techniques. The CeO2/SnO2 NPs (9.6 µA) modified GCE demonstrated an excellent and improved electrocatalytic activity in terms of higher anodic peak current and lower peak potential when compared to bare GCE (6.7 µA) and CeO2 NPs/GCE (8.2 µA) for the sensing of MES. The CeO2/SnO2 NPs/GCE shows broader linear response range and lower detection limit of 0.02-1572 µM and 0.006 µM, respectively. Moreover, other potentially interfering compounds such as a similar functional group containing biological substances and inorganic species have no interference effect towards MES sensing. In addition, the practicability of the CeO2/SnO2 NPs/GCE was tested by real sample analysis in commercial MES tablet, human urine, and serum samples with the appreciable recovery results.

Structural Insights on 2D Gadolinium Tungstate Nanoflake: A Promising Electrocatalyst for Sensor and Photocatalyst for the Degradation of Postharvest Fungicide (Carbendazim).

Gadolinium tungstate (Gd2(WO4)3) has acquired much attention owing to its exclusive transport properties and excellent thermal and chemical stability. In this work, we demonstrate that two-dimensional (2D) gadolinium tungstate nanoflakes (GW Nfs) are synthesized by a coprecipitation method and represent novel architectures for efficient catalysis, which could be used in electrochemical sensing and photocatalytic degradation of the postharvest fungicide carbendazim (CBZ). The physicochemical properties of GW Nfs were studied by using XRD, Raman, TEM, EDX, and XPS, which show the formation of GW as a nanoflake-like structure with a well crystallized nature. The as-prepared GW Nfs revealed an admirable electrochemical response for CBZ detection with an LOD of 0.005 µM, a wide-ranging linear response of 0.02 to 40 µM, and a notable sensitivity of 0.39 µA µM-1 cm-2. Furthermore, the GW-Nf-modified electrode has a good recovery for CBZ in the study of real samples such as rice and soil washed water samples. Moreover, GW Nfs have a promising photocatalytic activity for CBZ degradation. The GW Nfs could degrade CBZ at greater than 98% efficiency and mineralize above 74% of the CBZ molecules in the presence of visible light irradiation with superior stability even after many cycles. Subsequently, the electrochemical and photocatalytic mechanisms were provided in detail.

In Situ Synthesis, Characterization, and Catalytic Performance of Polypyrrole Polymer-Incorporated Ag2MoO4 Nanocomposite for Detection and Degradation of Environmental Pollutants and Pharmaceutical Drugs.

Material combinations of semiconductor with conducting polymer are gaining growing interest due to their enhanced activities in photocatalysis as well as electrochemical sensing. In this present work, we report a facile in situ synthesis of polypyrrole (PPy) polymer-incorporated silver molybdate (Ag2MoO4) nanocomposite that is utilized as a photocatalyst and electrocatalyst for the degradation of pollutant heavy metals, namely, methylene blue (MB) and heavy metal (Cr(VI)), and ciprofloxacin (CIP) and for detection of the drug, azomycin. The synthesized nanocomposite was characterized by various theoretical, spectral, and microscopic studies. Matching of the powder X-ray diffraction pattern with JCPDS no. 76-1747 confirmed the formation of α-Ag2MoO4/PPy. The surface topography and spherical morphology of the nanocomposite were studied using field emission-scanning electron microscopy and transmission electron microscopy. Fourier transform infrared spectral detail expounds the smooth incorporation of PPy to Ag2MoO4. The as-synthesized nanocomposite performs as an efficient photocatalyst in the degradation of MB (99.9%), Cr(VI) (99%), and CIP drug (99.8%) within 10 min. In addition to this, the Ag2MoO4/PPy-modified glassy carbon electrode (GCE) demonstrated excellent electrocatalytic activity in terms of a higher cathodic peak current and lower peak potential when compared with other modified and unmodified GCEs for the detection of azomycin. The Ag2MoO4/PPy/GCE displayed a broader linear response range and lower detection limit of 0.5-499 µM and 65 nM, respectively. Moreover, other potentially co-interfering compounds, such as a similar functional group-containing biological substances and inorganic species, have no interference effect toward azomycin sensing.

Synthesis, characterization and catalytic performance of nanostructured dysprosium molybdate catalyst for selective biomolecule detection in biological and pharmaceutical samples.

The current study reports a new, simple and fast method using a flake-like dysprosium molybdate (Dy2MoO6; FL-DyM) nanostructured material to detect the antibiotic drug metronidazole (METZ). This nanocomposite material was employed on the surface of a glassy carbon electrode (GCE) to develop the electrode (FL-DyM/GCE). Further, the synthesized FL-DyM was systematically characterized by powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray diffraction (EDS), elemental mapping, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) analyses. Cyclic (CV) and differential pulse voltammetry (DPV) techniques were used to study the electrochemical properties. The FL-DyM/GCE-based sensor demonstrated excellent selectivity and sensitivity for the detection of the drug METZ, which could be attributed to the strong affinity of FL-DyM towards the -NO2 group in METZ, and the good electrocatalytic activity and conductivity of FL-DyM. The fabrication and optimization of the working electrode were accomplished with CV and DPV obtained by scan rate and pH studies. Compared to the bare GCE and other rare-earth metal molybdates, the FL-DyM/GCE sensor displayed a superior electrocatalytic activity response for METZ detection. The sensor demonstrated a good linear relationship over the concentration range of 0.01-2363 µM. The quantification and detection limits were found to be 0.010 µM and 0.0030 µM, respectively. The FL-DyM/GCE sensor displayed excellent selectivity, repeatability, reproducibility, and stability for the detection of METZ in human urine and commercial METZ tablet samples, which validates the new technique for efficient drug sensing in practical applications.

A cerium vanadate interconnected with a carbon nanofiber heterostructure for electrochemical determination of the prostate cancer drug nilutamide.

Cerium vanadate resembling the shape of a hedgehog were interconnected with carbon nanofibers to give a heterostructure (referred to as CeV/CNF) that exhibits efficient catalytic activity for the electrochemical detection of the drug nilutamide (NLT). The heterostructure material and its modification were characterized by XRD, Raman spectra, XPS, FESEM, TEM, SAED, and EDX. A glassy carbon electrode was modified with the CeV/CNF nanocomposite. Best operated at -0.52 V (vs. Ag/AgCl), it exhibits a very low detection limit (2.0 nM), wide linear range (0.01-540 µM), high sensitivity (1.36 µA µM-1 cm-2) and rapid response towards NLT. It was applied to the determination of NLT in spiked human urine. Graphical abstractSchematic presentation of cerium vanadate interconnected with carbon nanofiber heterostructure for electrochemical determination of prostate cancer drug nilutamide in biological samples.

Ultrasonication-assisted synthesis of sphere-like strontium cerate nanoparticles (SrCeO3 NPs) for the selective electrochemical detection of calcium channel antagonists nifedipine.

In this work, strontium cerate nanoparticles (SrCeO3 NPs, SC NPs) were developed through facile synthetic techniques (Ultrasound-Assisted (UA) and Stirring-Assisted (SA) synthesis) and utilized as an electrocatalyst for the selective and sensitive electrochemical detection of calcium channel blocker nifedipine (NDF). The as-prepared UASC NPs and SASC NPs were characterized using XRD, Raman, TEM, EDS, mapping, XPS and BET analysis which exposed the formation of SC NPs in the form of spherical in shape and well crystalline in nature. BET studies reveal that UASC NPs have maximum surface area than that of SASC NPs. Further, the use of the as-developed UASC NPs and SASC NPs as an electrocatalyst for the detection of NDF. Interestingly, the UASC NPs modified screen printed carbon electrode (UASC NPs/SPCE) exhibited an excellent electrocatalytic activity in terms of lower reduction potential and enhanced reduction peak current when compared to SASC NPs and unmodified SPCE. Moreover, as-prepared UASC NPs/SPCE displayed wide linear response range (LR, 0.02-174 µM), lower detection limit (LOD, 5 nM) and good sensitivity (1.31 µA µM-1 cm-2) than that of SASC NPs (LR = 0.02-157 µM, LOD = 6.4 nM, sensitivity - 1.27 µA µM-1cm-2). Furthermore, UASC NPs/SPCE showed an excellent selectivity even in the existence of potentially co-interfering compounds such as similar functional group containing drugs, pollutants, biological substances and some common cations/anions. The developed sensor was successfully employed for the determination of NDF in real lake water, commercial NDF tablet and urine samples with acceptable recovery.

One-step sonochemical synthesis of 1D ß-stannous tungstate nanorods: An efficient and excellent electrocatalyst for the selective electrochemical detection of antipsychotic drug chlorpromazine.

In the modern world, the contamination of ecosystem by human and veterinary pharmaceutical drugs through the metabolic excretion, improper disposal/industrial waste has been subjected to a hot issue. Therefore, exploitation of exclusive structured material and reliable technique is a necessary task to the precise detection of drugs. With this regards, we made an effort for the fabrication of novel one-dimensional (1D) stannous tungstate nanorods (ß-SnW NRs) via simple sonochemical approach and used as an electrochemical sensor for the detection of antipsychotic drug chlorpromazine (CPZ) for the first time. The crystallographic structure, surface topology, elemental compositions and their distributions and ionic states were enquired by different spectroscopic techniques such as XRD, FTIR, SEM, EDS, elemental mapping and XPS analysis. The developed ß-SnW NRs/GCE sensor exhibits a rapid and sensitive electrochemical response towards CPZ sensing with wide linear response range (0.01-457 µM), high sensitivity (2.487 µA µM-1 cm-2), low detection limit (0.003 µM) and excellent selectivity. Besides, the as-proposed electrochemical sensor was successfully applied to real sample analysis in commercial CPZ drug and biological fluids and the acquired recovery results are quite satisfactory. The proposed sonochemical method for the preparation of ß-SnW NRs is low cost, very simple, fast and efficient for sensor applications.

3D Flower-Like Gadolinium Molybdate Catalyst for Efficient Detection and Degradation of Organophosphate Pesticide (Fenitrothion).

Three-dimensional (3D) nanostructured materials have received enormous attention in energy and environment remediation applications. Herein, we developed a novel 3D flower-like gadolinium molybdate (Gd2MoO6; GdM) and used as a bifunctional catalyst for the electrochemical detection and photocatalytic degradation of organophosphate pesticide fenitrothion (FNT). The flower-like GdM catalyst was prepared via a simple sol-gel technique with the assistance of urea and ethylene glycol. The properties of GdM were confirmed by various spectroscopic and analytical techniques. The GdM catalyst played a significant role in electrochemical reduction of FNT and results in a very low detection limit (5 nM), wide linear ranges (0.02-123; 173-1823 µM), and good sensitivity (1.36 µA µM-1 cm-2). Interestingly, the GdM electrocatalyst had good recoveries to FNT in soil and water sample analysis. In addition to trace level detection, the flower-like GdM was used as the photocatalyst which portrayed an excellent photocatalytic degradation behavior to eliminate the FNT in the aqueous system. The GdM photocatalyst could degrade above 99% of FNT under UV light irradiation with good stability even after five cycles.

Mobile phone based ELISA (MELISA).

Enzyme-linked immunosorbent assay (ELISA) is one of the most important technologies for biochemical analysis critical for diagnosis and monitoring of many diseases. Traditional systems for ELISA incubation and reading are expensive and bulky, thus cannot be used at point-of-care or in the field. Here, we propose and demonstrate a new miniature mobile phone based system for ELISA (MELISA). This system can be used to complete all steps of the assay, including incubation and reading. It weighs just 1 pound, can be fabricated at low cost, portable, and can transfer test results via mobile phone. We successfully demonstrated how MELISA can be calibrated for accurate measurements of progesterone and demonstrated successful measurements with the calibrated system.

Investigation on the Electrocatalytic Determination and Photocatalytic Degradation of Neurotoxicity Drug Clioquinol by Sn(MoO4)2 Nanoplates.

Transition-metal molybdates have concerned enormous curiosity as supercapacitors, photocatalysts, and electrocatalysts. These materials are the best alternatives to noble-metal-based catalysts, which are generally show a limited photocatalytic and electrocatalytic activity. In addition, the antiprotozoal drug can usually pollute the environment through improper disposable and incomplete metabolism, and it is very dangerous to humans as well as aquatic animals. Therefore, here, we have studied the electrochemical determination and photodegradation of neurotoxicity clioquinol (CQL) by nanoplate-like tin molybdate (Sn(MoO4)2, denoted as SnM), which is used as both an electro- and a photocatalyst. The as-prepared catalyst delivered a highly efficient activity toward the detection and degradation of CQL. The proposed nanoplate-like SnM was prepared through a simple wet-chemical route, and its physicochemical properties were characterized by various spectroscopic and analytical techniques. As an electrochemical sensor, the SnM electrocatalyst exhibited tremendous activity for the detection of CQL in terms of lower potential and enhanced anodic peak current. In addition, it showed high selectivity, a wide linear concentration range, a lower detection limit, and good sensitivity. From the UV-vis spectroscopy study, the SnM photocatalyst delivered an excellent photocatalytic activity toward the degradation of CQL in terms of increasing contact time and reducing CQL concentration, resulting in the increasing of the degradation efficiency about 98% within 70 min under visible light irradiation and showing an appreciable stability by observation of the reusability of the catalyst.

Sonochemical Synthesis of Sulfur Doped Reduced Graphene Oxide Supported CuS Nanoparticles for the Non-Enzymatic Glucose Sensor Applications.

Over the present material synthesis routes, the sonochemical route is highly efficient and comfortable way to produce nanostructured materials. In this way, the copper sulfide (CuS-covellite) and sulfur doped reduced graphene oxide (S-rGO) nanocomposite was prepared by sonochemical method. Interestingly, the structure of the as-prepared S-rGO/CuS was changed from the covellite to digenite phase. Herein, the S-rGO was act as a mild oxidizer and liable for the structural transformations. These structural changes are sequentially studied by various physicochemical characterizations such as Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Transmission electron microscopy (TEM). After scrupulous structural evaluations, the transformation of CuS phase was identified and documented. This oxidized CuS has an excellent electrocatalytic activity when compare to the bulk CuS. This S-rGO/CuS was further used for the determination of glucose and acquired good electrocatalytic performances. This S-rGO/CuS was exhibited a wide linear concentration range, 0.0001-3.88 mM and 3.88-20.17 mM, and a low-level detection limit of 32 nM. Moreover, we have validated the practicability of our developed glucose sensor in real biological samples.

A voltammetric determination of caffeic acid in red wines based on the nitrogen doped carbon modified glassy carbon electrode.

We reported an electrochemical determination of caffeic acid (CA) based on the nitrogen doped carbon (NDC). The described sensor material was prepared by the flame synthesis method, which gave an excellent platform for the synthesis of carbon nanomaterials with the hetero atom dopant. The synthesized material was confirmed by various physical characterizations and it was further characterized by different electrochemical experiments. The NDC modified glassy carbon electrode (NDC/GCE) shows the superior electrocatalytic performance towards the determination of CA with the wide linear concentration range from 0.01 to 350 µM. It achieves the lowest detection limit of 0.0024 µM and the limit of quantification of 0.004 µM. The NDC/GCE-CA sensor reveals the good selectivity, stability, sensitivity and reproducibility which endorsed that the NDC is promising electrode for the determination of CA. In addition, NDC modified electrode is applied to the determination of CA in red wines and acquired good results.

Measurement of thickness of highly inhomogeneous crude oil slicks.

As part of the Deepwater Horizon toxicity testing program, a number of laboratories generated oil slicks in the laboratory to study potential toxic effects of these oil slicks on aquatic organisms. Understanding the details of how these slicks affect aquatic organisms requires careful correlation between slick thickness and the observed detrimental effects. Estimating oil film thickness on water can be challenging since the traditional color-based technique used in the field is very imprecise. Also, as we demonstrate here, the films formed on the water surface are highly nonuniform on a microscale level, and thus uniform thin film thickness measurement techniques based on optical interference do not work. In this paper, we present a method that estimates the local thickness of weathered oil slicks formed on artificial seawater using light transmission and Beer-Lambert's law. Here, we demonstrate results of careful calibration together with the actual thickness estimation. Due to the heterogeneity of the slicks formed, we present slick thickness as a range of thicknesses collected from multiple points within the oil slick. In all the experiments we used oil samples provided by the Natural Resource Damage Assessment toxicity testing program for the Deepwater Horizon oil spill. Therefore, this study has an important practical value and successfully addresses unique challenges related to measurements involving complex, viscous, paste-like heterogeneous substances such as weathered crude oil.

Rapid synthesis of ethyl cellulose supported platinum nanoparticles for the non-enzymatic determination of H2O2.

Cellulose derivatives are one of the carbohydrate polymers which received a great interest in the construction of nanostructured materials. Particularly, the ethyl cellulose provides an enormous support to the metal nanoparticles. To the best of our knowledge, this is the first time report for the simple and rapid synthesis of ethyl cellulose (EC) supported platinum nanoparticles (PtNPs) for the determination of non-enzymatic hydrogen peroxide (H2O2). The PtNPs/EC composite was confirmed by various characterizations such as fourier transform infra-red spectra, energy dispersive X-ray spectra, field emission scanning electron microscope and cyclic voltammetry. Further, the PtNPs/EC composite modified glassy carbon electrode (GCE) was successfully determined the H2O2 with the linear concentration range from 0.05µM to 2.22mM and the lowest detection limit of 0.01µM. Moreover, the PtNPs/EC/GCE sensor electrode manifested an acceptable sensitivity, selectivity and reproducibility. In addition, we have determined the H2O2 in contact lens solution and human blood serum samples.