Functionalized Copper Nanoparticles Research Articles

Dual functionalized copper nanoparticles for thermoplastics with improved processing and mechanical properties and superior antibacterial performance.

The utilization of metal nanoparticles for antibacterial thermoplastic composites has the potential to enhance the safety of human and animal life by mitigating the spread and transmission of foodborne pathogenic bacteria. The dispersion, antioxidant and antimicrobial activities of metal nanoparticles directly affect the application performance of the composites. This study focused on achieving amine-carboxyl co-modified copper nanoparticles (Cu-AC) with excellent antioxidant properties and monodispersity through in situ grafting of amine and carboxyl groups onto the surface of copper nanoparticles via ligand interaction. Polyacrylic acid's extended carbon chain structure was utilized to improve its dispersion and antioxidant properties, and its antibacterial properties were synergistically enhanced using secondary amines. It was found that Cu-AC possesses high antibacterial properties, with a minimum inhibition concentration of 0.156 mg mL-1. Antibacterial masterbatches and their composites (polypropylene/Cu) manufactured by melt blending of polypropylene and Cu-AC exhibited excellent antibacterial rates of up to 90% and 99% at 300 ppm and 700 ppm Cu-AC, respectively. Additionally, Cu-AC bolstered the thermal degradation, processing and mechanical properties of polypropylene. The successful implementation of this product substantiates the potential applications of polypropylene/Cu composite materials across diverse industries.

Functionalized Copper Nanoparticles with Gold Nanoclusters: Part I. Highly Selective Electrosynthesis of Hydrogen Peroxide.

Copper nanoparticles (CuNPs) and gold nanoclusters (AuNCs) show a high catalytic performance in generating hydrogen peroxide (H2O2), a property that can be exploited to kill disease-causing microbes and to carry carbon-free energy. Some combinations of NPs/NCs can generate synergistic effects to produce stronger antiseptics, such as H2O2 or other reactive oxygen species (ROS). Herein, we demonstrate a novel facile AuNC surface decoration method on the surfaces of CuNPs using galvanic displacement. The Cu-Au bimetallic NPs presented a high selective production of H2O2 via a two-electron (2e-) oxygen reduction reaction (ORR). Their physicochemical analyses were conducted by scanning electron microscopy (SEM), transmitting electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). With the optimized Cu-Au1.5NPs showing their particle sizes averaged in 53.8 nm, their electrochemical analysis indicated that the pristine AuNC structure exhibited the highest 2e- selectivity in ORR, the CuNPs presented the weakest 2e- selectivity, and the optimized Cu-Au1.5NPs exhibited a high 2e- selectivity of 95% for H2O2 production, along with excellent catalytic activity and durability. The optimized Cu-Au1.5NPs demonstrated a novel pathway to balance the cost and catalytic performance through the appropriate combination of metal NPs/NCs.

2-Mercaptobenzimidazole Functionalized Copper Nanoparticles Fluorescence Probe for Sensitivity and Selectivity Detection of Cys in Serum.

In this paper, a 2-mercaptobenzimidazole-copper nanoparticles (MBI-CuNPs) fluorescent probe with high performance based on 2-mercaptobenzimidazole functionalized copper nanoparticles was synthesized by a hydrothermal method and used for cysteine (Cys) detection in serum. The MBI-CuNPs probe exhibits strong fluorescence emission at 415 nm under the excitation at 200 nm, which is attributed to the metal-ligand charge transfer (MLCT) transition through the coordination of an MBI ligand and monovalent copper. Furthermore, the MBI-CuNPs probe has a high quenching fluorescence response to Cys, and shows a good linearity relationship with Cys in 0.05-65 µM, with a detection limit of 52 nM. Moreover, the MBI-CuNPs probe could eliminate the interference of biological mercaptan Hcy and GSH with a similar structure and reaction properties, due to the strong electron-donating ability of Cys, which can quench the fluorescence of the MBI-CuNPs probe. The MBI-CuNPs probe was applied to the analysis of Cys in real serum, and the absolute recovery rate was as high as 90.23-97.00%. Such a fluorescent probe with high sensitivity and selectivity has potential applications for the early prevention of various diseases caused by abnormal Cys levels.

Design and development of an electroanalytical genosensor based on Cu-PTCA/rGO nanocomposites for the detection of cervical cancer

Cervical cancer is one of the most ordinary fatalities that occurs between middle-aged and older women. When left undiagnosed and untreated, this disease leads to life-threatening events among the female populace and has been placing a huge burden on available healthcare resources. Considering numerous limitations (high cost, time consuming, bulky equipment etc.) of conventional techniques for diagnosing this highly malignant cancer, it becomes imperative to develop miniaturized bio sensing platforms which can aid in early detection of cervical cancer for enhanced patient outcomes. We made our way on the design and development of an electrochemical biosensor based on the novel Nano-composites of Perylene Tetra carboxylic acid functionalized copper nanoparticles and reduced graphene oxide (Cu-PTCA/rGO) for DNA-based detection of Human Papilloma Virus 16 (HPV 16) – the key biomarker for cervical cancer. Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS) were used to classify the developed sensor, with the latter providing insights into the electrode kinetics. The sensor optimizations and analytical performance were assessed using Square Wave Voltammetry (SWV), eventually exhibiting sensitivity and limit of detection of 0.052 μA/μM/mm2 and 2.15 fM respectively. The genosensor was found to be selective solely to HPV 16 target DNA and exhibited a shelf life of 35 days. The developed sensor response was also evaluated in serum samples, and it was found to exhibit high percentage recoveries, validating its application in future point-of-care scenario.

Copper nanoparticles interlocked phase-change microcapsules for thermal buffering in packaging application

A novel kind of functionalized copper nanoparticles (CuNPs) interlocked polydivinylbenzene (PDVB) microcapsules containing hexadecane as phase change material (PCM) was synthesized targeting thermal buffering application in food packaging. Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) characterizations confirmed the successful functionalization of CuNPs and their existence in the PDVB shell. Scanning electron microscopy (SEM) results indicated that produced microcapsules exhibited well-defined core–shell microstructure with spherical morphology, and their compositions and chemical structures were confirmed by a series of spectroscopic characterizations. Atomic force microscopy (AFM) results showed that average and mean square roughness is higher in CuNPs/microPCMs than bare microcapsules. Differential scanning calorimetry (DSC) analysis confirmed that microPCM with 1.0% CuNPs achieved a maximum melting enthalpy of 132 J/g with an encapsulation ratio of 60.5% and could maintain it even after 100 melting-freezing cycles. The thermal conductivity was significantly increased by 319.5% as compared with that of bare microcapsules. Most importantly, optimized microcapsules provided an excellent thermal buffering effect of more than 6.5 h for the 240 g of chocolate to raise its temperature from 5 °C to 35 °C, confirming great potential in food packaging application.

Antimicrobial Property of Polypropylene Composites and Functionalized Copper Nanoparticles.

Copper nanoparticles (CuNPs) functionalized with polyethyleneimine (PEI) and 4-aminobutyric acid (GABA) were used to obtain composites with isotactic polypropylene (iPP). The iPP/CuNPs composites were prepared at copper concentrations of 0.25–5.0 wt % by melt mixing, no evidence of oxidation of the CuNP was observed. Furthermore, the release of copper ions from iPP/CuNPs composites in an aqueous medium was studied. The release of cupric ions was higher in the composites with 2.5 and 5.0 wt %. These composites showed excellent antibacterial activity (AA) toward Pseudomona aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus). The incorporation of CuNP into the iPP polymeric matrix slightly decreased the thermal stability of the composite material but improved the crystallinity and the storage modulus. This evidence suggests that CuNPs could work as nucleating agents in the iPP crystallization process. The iPP/CuNPs composites presented better AA properties compared to similar composites reported previously. This behavior indicates that the new materials have great potential to be used in various applications that can be explored in the future.

A highly discerning p-tetranitrocalix[4]arene (p-TNC4) functionalized copper nanoparticles: A smart electrochemical sensor for the selective determination of Diphenhydramine drug

In this work, we develop an exceptional and discerning electrocatalyst for selective and sensitive detection of Diphenhydramine (DPH). For the first time, successful fabrication of copper metal nanoparticles (CuNPs) was carried out by utilizing p-tetranitrocalix[4]arene (p-TNC4) as an effective capping and stabilizing agent. After the efficacious synthesis of p-TNC4 derivative functionalized CuNPs were exploited for various characterization tools such as UV–Visible, FTIR, XRD, and SEM which confirmed the successful preparation of CuNPs with nanoflakes morphology, face-centered cubic structure, and average size around 18 nm respectively. For the investigation of catalytic capabilities of synthesized material, the prepared CuNPs were used as electrochemical sensing probe for the sensitive detection of Diphenhydramine drug-using Differential Pulse Voltammetry (DPV) as detection mode. Under the optimized conditions such as supporting electrolyte, pH study, and potential range, the developed CuNPs/GCE manifested outstanding results for detection of Diphenhydramine at 0.67 V within the range of 0.0 to 1.2 V) in borate supporting electrolyte at pH 8. The linear dynamic range of the developed sensor was utilized from 0.0001 to 0.40 µM with a very low limit of detection and limit of quantification calculated to be 0.116 nM and 1.167 nM respectively. The modified sensor was tested in real applications of urine and serum samples.

Preparation and characterization of curcumin functionalized copper nanoparticles and their application enhances disease resistance in chickpea against wilt pathogen

Abstract For effective use of curcumin in plant disease management, it is imperative to increase its solubility. Decreasing the particle size can increase the surface area and enhance solubility. Therefore, the present study aims to prepare curcumin copper nanoparticles (Cur-CuNPs) to improve its aqueous solubility to use as an antifungal agent and to protect chickpea plants from the devastating pathogen, Fusarium oxysporum f. sp. ciceri (FOC). The Cur-CuNPs were analyzed by 1H NMR, 13C NMR spectroscopy. The structure, size, morphology was characterized through FTIR, SEM, TEM and XRD analyses. The Cur-CuNPs synthesized in this study was found to be freely dispersible in water and inhibits the growth of FOC under in vitro condition, protects the chickpea plant from wilt disease. Application of Cur-CuNPs to chickpea seed influenced the growth parameters such as root, shoot length, number of leaves and dry weight. These results indicate that Cur-CuNPs can be integrated in disease management strategies as fungicide and as nanofertilizer to enhance chickpea plant health.

Selective and sensitive determination of dihydroxybenzene isomers in water samples using functionalized copper nanoparticles modified graphite electrode

A highly selective and sensitive electrochemical sensor for the determination of environmentally hazardous dihydroxybenzene isomers such as hydroquinone (HQ), catechol (CC) and resorcinol (RS) was fabricated by electrodeposition of Cu nanoparticles on polycysteine film deposited graphite electrode in room temperature ionic liquid medium as electrolyte. The electrochemical characteristics of the polycysteine functionalized copper nanoparticles (PCFCuNP) modified electrode was studied using cyclic voltammetry. The voltammetric response of dihydroxybenzene isomers at the modified electrode showed the current densities remarkably higher than the bare graphite electrode and occurred at a reduced overvoltage. For HQ, CC, RS the oxidation peak currents are linear to the concentrations at the range of 3.3 × 10-6 − 1.3 × 10-3 M, 1.6 × 10-6 −1.3 × 10-3 M and 3.3 × 10-6 − 9.0 × 10-3 M with the detection limits of 1.1 × 10-6 M, 5.3 × 10-7 M and 1.1 × 10-6 M, respectively (S/N = 3). The stable and fast response during amperometric method shows the potential application of the PCFCuNP modified electrode for flow system analysis. The method was successfully examined for two different water samples with high selectivity and sensitivity.

Dual nature solution of water functionalized copper nanoparticles along a permeable shrinking cylinder: FDM approach

Present framework is established to deal the characteristics of axisymmetric mixed convection flow with heat transfer of water based copper (Cu-water) nanofluid along a porous shrinking cylinder with slip effects. The physical problem is modeled in the form of set of partial differential equations (PDEs) including conservation of mass, momentum and energy equations along with defined boundary conditions. Such PDEs are adapted to ordinary differential equations (ODEs) by utilizing similarity transformation technique. System of equations is emerged with the expressions of nanoparticle and based fluid. Numerical solution of governing ODEs is sought by using Finite Difference Method (FDM) against the range of several pertinent physical parameters. Base fluid (water) is analyzed in the presence of nanoparticles. The model encounters buoyancy opposing and assisting flow regions. Present study reveals that the solution in the assisting flow region is unique whereas multiple solutions exist in the opposing flow region. The results also indicate the existence of multiple solutions for certain amount of mass suction parameter. Moreover, increase in slip parameters and nanoparticle volume fraction enhances the range of suction parameter where the similarity solutions exist. It is further found that due to increase of nanoparticle volume fraction the skin friction increases whereas heat transfer rate decreases.

Electrochemical Assay of the Alpha Fetoprotein-L3 Isoform Ratio To Improve the Diagnostic Accuracy of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is now the major malignant disease with high morbidity and mortality, which seriously endangers human lives and health. Alpha fetoprotein (AFP) assay is a commonly used serological biomarker for clinical diagnosis of HCC, but it lacks specificity. Analysis of its isoform AFP-L3, especially the AFP-L3 ratio in total AFP (AFP-L3%), can significantly improve the specificity for HCC identification. Herein, an electrochemical approach has been first proposed for simple, accurate, and fast determination of AFP-L3% in clinical samples. On the basis of two independent electrochemical signals generated from the synthesized nanoparticles, 4-mercaptophenylboronic acid (MPA)-functionalized copper nanoparticles (MPA-CuNPs) and the Lens culinaris agglutinin (LCA)-functionalized silver nanoparticles (LCA-AgNPs), simultaneous quantification of the AFP-L3 and total AFP in serum sample has been achieved, thus achieving directly the electrochemical assay of AFP-L3%. To be noted, both the assay time and the assay procedure have been significantly compressed when compared to that of available techniques in clinical use. Therefore, with the integration of electrochemical techniques, this new approach for AFP-L3% analysis would be promising for the accurate diagnosis of HCC.

Environmentally relevant concentrations of amine-functionalized copper nanoparticles exhibit different mechanisms of bioactivity in Fundulus Heteroclitus in fresh and brackish water

The bioavailability of engineered nanomaterials should be limited in marine environments, but uptake and toxicity has been noted in marine fish and invertebrates, albeit at exposure doses far exceeding predicted environmental levels. We examined the bioactivity of amine functionalized copper nanoparticles (nCu; 5–10 nm core diameter) to the euryhaline killifish, Fundulus heteroclitus, in fresh (FW) and brackish water (BW). Free copper dissolution was undetectable in either water type and nCu remained relatively well dispersed in BW, despite the high ionic strength. Exposure to an environmentally relevant concentration of nCu (10 µg L−1) for 48 h significantly increased the maximum rate of oxygen consumption and aerobic scope in BW killifish. This effect was associated with gill remodeling which likely increased surface area and scope for oxygen uptake. In contrast, nCu exposure had no effect on oxygen consumption in FW killifish, but gill Na+/K+-ATPase activity was reduced by >40%, an effect not seen in BW. Osmotic and ionic homeostasis were protected and no indications of physiological or oxidative stress were observed in either FW and BW exposure groups. The results show that functionalized nCu formulations can exhibit bioactivity in both FW and BW and that the underlying mechanisms are different between water types.

Facile and green synthesis of highly stable l-cysteine functionalized copper nanoparticles

A simple eco-friendly method for l-cysteine capped copper nanoparticles (CCNPs) synthesis in aqueous solution has been developed. Glucose and l-cysteine were used as reducing agent and capping/functionalizing agent, respectively. Different parameters such as capping agent concentration, pH, reaction temperature, and reducing agent concentration were optimized during the synthesis. The l-cysteine capped copper nanoparticle were characterized by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, Particle size and zeta potential analyser, and high resolution transmission electron microscopy. Spherical shaped cysteine functionalized/capped copper nanoparticles with an average size of 40nm were found to be highly stable at room temperature (RT) for a period of 1 month

Effects of surface grafting of copper nanoparticles on the tensile and bonding properties of flax fibers

Abstract In the present work, functionalized copper nanoparticles (FCuNPs) were grafted onto flax fibers, and the effects on the tensile properties, bonding strength to an epoxy resin, as well as the properties of the flax fiber-epoxy model composites were investigated. The copper nanoparticles were synthesized at ambient temperature by a chemical reduction method. The reduction of solution of copper chloride salt in the polyvinylalcohol medium was done by using sodium borohydrate. Ultraviolet-visible spectroscopy, transmission electron microscopy, and X-ray diffraction studies were used to characterize the size of the synthesized particles. The synthesized copper nanoparticles were applied to saturate the unidirectional flax natural fibers, whose surfaces were previously tailored with the cationic agent triethylammonium chloride. A remarkable improvement in the tensile strength by 75% and modulus by 50% for FCuNPs grafted flax fibers was found. Thermo-mechanical properties of the flax fiber reinforced epoxy composites were studied using DMTA. Finally, the anti-microbial analysis for composites was also conducted against Aspergillus niger spores, and enhanced anti-microbial performance was observed for treated fiber-based composites.

Facile and rapid detection of respiratory syncytial virus using metallic nanoparticles.

BackgroundRespiratory syncytial virus (RSV) causes severe respiratory infection in infants, children and elderly. Currently, there is no effective vaccine or RSV specific drug for the treatment. However, an antiviral drug ribavirin and palivizumab is prescribed along with symptomatic treatment. RSV detection is important to ensure appropriate treatment of children. Most commonly used detection methods for RSV are DFA, ELISA and Real-time PCR which are expensive and time consuming. Newer approach of plasmonic detection techniques like localized surface plasmon resonance (LSPR) spectroscopy using metallic nanomaterials has gained interest recently. The LSPR spectroscopy is simple and easy than the current biophysical detection techniques like surface-enhanced Raman scattering (SERS) and mass-spectroscopy.ResultsIn this study, we utilized LSPR shifting as an RSV detection method by using an anti-RSV polyclonal antibody conjugated to metallic nanoparticles (Cu, Ag and Au). Nanoparticles were synthesized using alginate as a reducing and stabilizing agent. RSV dose and time dependent LSPR shifting was measured for all three metallic nanoparticles (non-functionalized and functionalized). Specificity of the functionalized nanoparticles for RSV was evaluated in the presence Pseudomonas aeruginosa and adenovirus. We found that functionalized copper nanoparticles were efficient in RSV detection. Functionalized copper and silver nanoparticles were specific for RSV, when tested in the presence of adenovirus and P. aeruginosa, respectively. Limit of detection and limit of quantification values reveal that functionalized copper nanoparticles are superior in comparison with silver and gold nanoparticles.ConclusionsThe study demonstrates successful application of LSPR for RSV detection, and it provides an easy and inexpensive alternative method for the potential development of LSPR-based detection devices.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-016-0167-z) contains supplementary material, which is available to authorized users.

L-cysteine protected copper nanoparticles as colorimetric sensor for mercuric ions

This report demonstrates a novel, simple and efficient protocol for the synthesis of copper nanoparticles in aqueous solution using l-cysteine as capping or protecting agent. UV–visible (UV–vis) spectroscopy was employed to monitor the LSPR band of l-cysteine functionalized copper nanoparticles (Cyst-Cu NPs) based on optimizing various reaction parameters. Fourier Transform Infrared (FTIR) spectroscopy provided information about the surface interaction between l-cysteine and Cu NPs. Transmission Electron Microscopy (TEM) confirmed the formation of fine spherical, uniformly distributed Cyst-Cu NPs with average size of 34±2.1nm. X-ray diffractometry (XRD) illustrated the formation of pure metallic phase crystalline Cyst-Cu NPs. As prepared Cyst-Cu NPs were tested as colorimetric sensor for determining mercuric (Hg2+) ions in an aqueous system. Cyst-Cu NPs demonstrated very sensitive and selective colorimetric detection of Hg2+ ions in the range of 0.5×10−6–3.5×10−6molL−1 based on decrease in LSPR intensity as monitored by a UV–vis spectrophotometer. The developed sensor is simple, economic compared to those based on precious metal nanoparticles and sensitive to detect Hg2+ ions with detection limit down to 4.3×10−8molL−1. The sensor developed in this work has a high potential for rapid and on-site detection of Hg2+ ions. The sensor was successfully applied for assessment of Hg2+ ions in real water samples collected from various locations of the Sindh River.

Development of Cu Nanoparticle Loaded Oil Palm Fibre Reinforced Nanocomposite

Functionalized copper nanoparticles (FCuNPs) have been synthesized by chemical reduction method and polyvinyl alcohol (PVA) performed as a stabilizer in that medium. Analysis observed that the average size of the synthesized FCuNPs was 3.5 nm. The obtained FCuNPs were loaded in the oil palm empty fruit bunch (EFB) natural fibre. Before the loading of FCuNPs in EFB fibres, the surface of the fibres is tailored by the cationic agent CHPTAC since they have a natural tendency to exhibit negatively charged surface owing to the presence of large amount of hydroxyl groups. Thereafter, different types of composite were developed and their properties were studied. The composites were developed by using the untreated empty fruit bunch (UEFB) fibres and FCuNPs loaded EFB (NP-CAEFB) fibres with commercially available unsaturated polyester resin (UPER). The synthesized composites were characterized through FTIR, FESEM, XRD, DSC, tensile strength tests, etc. The obtained biodegradation results indicated that significant weight loss was not observed for neat PER and PER/FNP-CAEFB nanocomposite, whereas, the UEFB/VUPER composite showed ca. 21.4% weight loss at 90 days, which was considered rationally due to the preferential degradation of the fibre.

Glucosamine functionalized copper nanoparticles: Preparation, characterization and enhancement of anti-bacterial activity by ultraviolet irradiation

Glucosamine functionalized copper nanoparticles (GlcN-Cu NPs) were synthesized for anti-bacterial function. Electron microscopic characterization revealed the hybrid morphology, selected-area electron diffraction pattern and elemental mapping of GlcN-Cu NPs. Average particle size distribution was 93±8nm. GlcN functionalization allowed significant shift in the ultraviolet (UV)-visible absorbance at 525nm and fluorescent emission wavelength at approximately 353nm for Cu NPs. Stretching and bending vibrations from Fourier transform-infrared and Raman analysis ensured GlcN functionalization on Cu NPs. We demonstrated the enhanced anti-bacterial property of GlcN-Cu NPs against two Gram-negative and Gram-positive bacterial strains by UV irradiation of prepared materials for 10 and 20min. Minimum inhibitory concentration (MIC) determinations revealed that UV irradiated GlcN-Cu NPs possessed enhanced anti-bacterial activity than simple Cu NPs, Cu metal salt and standard anti-biotic kanamycin. MIC for GlcN-Cu NPs was 4μg/mL for Escherichia coli and 8μg/mL for Salmonella typhimurium, Enterococcus faecalis and Bacillus subtilis, confirming its potential as an anti-infective agent for the protection of medical instruments, water treatment and in food processing.

Synthesis, Characterization, and Antifouling Potential of Functionalized Copper Nanoparticles

The synthesis, characterization, and antimicrobial properties of functionalized copper nanoparticle/polymer composites are reported. Copper nanoparticles (Cu NPs) are stabilized by surface attachment of the acrylic functionality that can be copolymerized with other acrylic monomers, thus, becoming an integral part of the polymer backbone. Biological experiments show that Cu NP/polymer composites exhibit antimicrobial activity similar to that of conventional copper-based biocides. Atomic absorption spectroscopy shows the smallest amount of copper ions leaching from chemically bound acrylated Cu NPs compared to the nonfunctionalized biocides. These composites have a strong potential for use in antibacterial or marine antifouling coatings.

Preparation of functionalized copper nanoparticles and fabrication of a glucose sensor

Dimethylglycoxime (DMG) functionalized copper nanoparticles (DMG-CuNPs) were prepared by a microwave heating method and characterized by TEM, FTIR, and XRD. The as-prepared nanoparticles were used to construct a new glucose sensor. Experimental results showed that DMG could be used to encapsulate the copper nanoparticles to control their growth during the preparation process and could chelate copper ions which were produced during the positive scan in the electrochemical experiments. The sensor showed good selectivity and sensitivity. A wide linearity range and a low detection limit have been assessed for it. A linear response to glucose in the concentration range between 1.0 × 10 −6 and 5.0 × 10 −3 M and a detection limit of 5.0 × 10 −7 M were observed. Most important of all, the common drawback of copper electrode fouling was overcome in this sensor.