Electrode Contamination Research Articles

"Two-in-One" PtPdCu Trimetallic Multifunctional Nanoparticles-Mediated Dual-Signal-Integrated Aptasensor for Ultradetection of Enrofloxacin.

Balancing the accuracy and simplicity of aptasensors is a challenge in their construction. This study addresses this issue by leveraging the remarkable loading capacity and peroxidase-like catalytic activity of PtPdCu trimetallic nanoparticles, which reduces the reliance on precious metals. A dual-signal readout aptasensor for enrofloxacin (ENR) detection is designed, incorporating DNA dynamic network cascade reactions to further amplify the output signal. Exploiting the strong loading capacity of PtPdCu nanoparticles, they are self-assembled with thionine (Thi) to form a signal label capable of generating signals in two independent modes. The label exhibits excellent enzyme-like catalytic activity and enhances electron transfer capabilities. Differential pulse voltammetry (DPV) and square-wave voltammetry (SWV) are employed to independently read signals from the oxidation-reduction reaction of Thi and the catalytic oxidation of hydroquinone (HQ) to benzoquinone (BQ) by H2O2. The introduced DNA dynamic network cascade reaction modularizes sample processing and electrode surface signal generation, avoiding electrode contamination and efficiently increasing the output of the catalyzed hairpin assembly (CHA) cycle. Under optimized conditions, the developed aptasensor demonstrates detection limits of 0.112 (DPV mode) and 0.0203 pg/mL (SWV mode). Additionally, the sensor successfully detected enrofloxacin in real samples, expanding avenues for designing dual-mode signal amplification strategies.

Microporous Ag/AgCl on a Titanium Scaffold for Use in Capillary Reference Electrodes.

AgCl-coated silver fabricated with the thermal-electrolytic method can be used to prepare more reproducible reference electrodes than Ag/AgCl prepared with alternative methods such as electrolytic and chemical AgCl deposition or thermal fabrication. However, thermal-electrolytic fabrication requires a scaffold material upon which to build the layers upon. Platinum and rhodium have been used for this purpose as they are mechanically strong and chemically inert, but their cost is prohibitive for wider application. Herein, we report the stability of Ag/AgCl reference electrodes built atop a titanium scaffold using the thermal-electrolytic method and the use of these Ti/Ag/AgCl constructs in capillary-based reference electrodes. Electrochemical characterization shows that the probable presence of small amounts of oxygen at the Ti/Ag interface does not affect the reference electrode performance; in particular, over a wide pH range, the half-cell potential is pH independent. The electrical resistance of the Ti/Ag/AgCl/KCl system is dominated by the charge transfer resistance at the interface of the AgCl to KCl solution but is kept very small by the large AgCl surface area and a high solution concentration of chloride. The resulting high exchange current minimizes the effect of system impurities on the reference half-cell potential. Capillary-based reference electrodes comprising Ti/Ag/AgCl show exceptionally low potential drifts (as low as 0.03 ± 2.01 μV/h) and standard deviations of the potential at or below ±0.5 mV over a 60 h period. These capillary-based reference electrodes are suitable for very small sample volumes while still providing a free-flowing liquid junction that prevents reference electrode contamination.

Electrode Montage for Bilateral Cervical Vestibular Evoked Myogenic Potential (cVEMP) Testing.

Cervical vestibular evoked myogenic potentials (cVEMPs) are predominantly ipsilateral, myogenic responses originating from saccular activation. Some individuals have contralateral-crossed cVEMP responses with monaural air-conducted stimulation (ACS) which can contaminate cVEMP responses with bilateral stimulation. While the origin of the contralateral-crossed response is under debate, its presence has implications for cVEMP testing with midline bone conduction vibration (BCV). The purpose of this study was to determine the origin of the contralateral-crossed cVEMP response. It was hypothesized that the crossed response is due to electrode contamination and would disappear with a modified electrode montage. Cross-sectional research study. Fifteen healthy participants (30 ears; mean age: 27.4 19-39; 10 females). Participants completed cVEMP testing using three stimulation methods (monoaural ACS, binaural ACS, and midline BCV) and two electrode montages (sternum reference and Fp reference). In the monoaural ACS with sternum reference condition, 53.3% ears had contralateral-crossed cVEMP responses that were in-phase with the ipsilateral response for all but 3 ears. Whereas in the monoaural ACS with Fp reference condition, 3% had a contralateral-crossed cVEMP response. ACS and BCV cVEMP corrected amplitudes were significantly larger in the sternum reference conditions, which is attributed to artificial enhancement from the in-phase contralateral-crossed responses. The significant reduction of contralateral-crossed responses in the Fp reference condition suggests that the contralateral-crossed cVEMP response is due to reference electrode contamination and may be a more appropriate reference placement when completing cVEMPs with midline BCV. The purpose of this study was to determine the origin of the contralateral-crossed cVEMP response. It was hypothesized that the crossed response is due to electrode contamination and would disappear with a modified electrode montage. Cross-sectional research study. Fifteen healthy participants (30 ears; mean age: 27.4 19-39; 10 females). Participants completed cVEMP testing using three stimulation methods (monoaural ACS, binaural ACS, and midline BCV) and three electrode montages (sternum reference, Fp reference, and active on Fp). In the monoaural ACS with sternum reference condition, 53.3% ears had contralateral-crossed cVEMP responses that were in-phase with the ipsilateral response for all but 3 ears. Whereas in the monoaural ACS with Fp reference condition, 3% had a contralateral-crossed cVEMP response. No participants demonstrated responses using Fp for the active electrode suggesting this is a neutral site. ACS and BCV cVEMP corrected amplitudes were significantly larger in the sternum reference conditions, which is attributed to artificial enhancement from the in-phase contralateral-crossed responses. The significant reduction of contralateral-crossed responses in the Fp reference condition suggests that the contralateral-crossed cVEMP response is due to reference electrode contamination and may be a more appropriate reference placement when completing cVEMPs with midline BCV.

Sputter-cleaning modified interfacial energetic and molecular structure of DNTT thin film on ITO substrate

The effect of natural electrode contamination on interfacial energetic, structure and morphology of π-conjugated organic molecular layers were studied by depositing dinapthothienothiophene (DNTT) thin films of varying thickness on indium-tin-oxide (ITO) substrates and by using photoelectron spectroscopy, atomic force microscopy and X-ray reflectivity techniques. The DNTT thin film on unclean-ITO surface shows a smaller threshold ionization potential (by ∼0.4 eV) compared to the film on clean-ITO one. A molecule–substrate interaction, present in the DNTT/clean-ITO system, gives rise to an interfacial dipole and charge transfer, presumably through flat-lying seed-layer at the interface. On further deposition, the interfacial coverage increases, while the molecules on top of the seed-layer take different orientation (mostly edge-on) to form highly-dewetted fibrous-islands of very high-thickness but very low-coverage. Overall, the growth of DNTT film on clean-ITO surface is layer-plus-island-like or Stranski–Krastanov-type. On the other hand, the contamination layer at the DNTT/unclean-ITO interface is found to act as a spacer layer, which reduces the intimate molecule–substrate interaction and also the roughness to give rise an edge-on ordered island-like or Volmer–Weber-type film-growth with reduced hole injection barrier (by ∼0.2 eV) and better (almost double) film-coverage to make it a more efficient hole injector compared to the clean interface one.

PCB-C4D coupled with paper-based microfluidic sampling for the rapid detection of liquid conductivity.

The detection of liquid electrical conductivity has board applications in food safety testing, water quality monitoring, and agricultural soil analysis. Electrodes used in traditional liquid electrical conductivity detection come into direct contact with liquid, leading to electrode contamination and affecting the accuracy of the detection results. The capacitively coupled contactless conductivity detection (C4D) method effectively addresses this issue. However, impurity particles present in the solution can compromise the consistency and repeatability of detection results. This study combines paper-based microfluidic technology with printed circuit board-capacitively coupled contactless conductivity detection (PCB-C4D) to address this issue. Prior to sample detection, in situ rapid filtration is employed to remove impurity particles from the raw solution sample, significantly enhancing detection consistency and reliability. Simultaneously, Optimization of PCB-C4D parameters, channel size, filtration time, and solution drop rate ensures optimal detection conditions. A compact kit design facilitates reliable assembly of the PCB-C4D electrodes and paper-based channel, enhancing practicality. Practical measurements on the conductivity of orange juice, cucumber, and soil solution further validate the method's accuracy, rapidity, and effectiveness in in situ conductivity detection. This work advances the practical application of PCB-C4D technology.

Three-compartment membrane electrolyzer combining simultaneous desalination and oxidative degradation in treating nanofiltration concentrate

The complex organic and inorganic solutes present in nanofiltration's purification by-product (NF concentrate, NFC) pose challenges to the water processing procedure. To address this, a three-compartment membrane electrolyzer was proposed that facilitates electro-driven ion migration for crystallization alongside synchronous anodic oxidation for organic degradation. With a hydraulic retention time (HRT) of 5 min and a current exceeding 50 mA, the system effectively separated over 25 % of inorganic salts and accomplished reclamation through crystallization in the concentration compartment. Simultaneously, it achieved oxidation of pollutants by more than 35 % based on the total nitrogen index and removed upwards of 15 % of organic carbon. Notably, the efficiency of pollutant removal correlated strongly with the intensity of the current. Furthermore, this study uncovered two issues encountered during the electrochemical process: membrane fouling and electrode fouling. During concentration, metal cations readily formed organic pollution by complexing with organic pollutants, while the crystallization of inorganics on the surface of anion exchange membranes emerged as a pivotal factor hindering current enhancement, similar to the formation of deposited salt in a solution. Long HRT can lead to electrode contamination and corrosion which subsequently affect current efficiency. Energy consumption verified the feasibility of the electrolyzer for NFC processing. Based on our findings, a current intensity of 100 mA (equivalent to a density of 8 mA/cm2) was deemed optimal, striking a balance between pollutant removal and various limiting factors associated with each pollutant. Consequently, this innovative advancement in membrane electrolyzers helps in overcoming limitations in synergistic desalination, ion recovery, and organic removal, establishing a fundamental component of the abbreviated flow process for future NFC treatment.

Enabling unassisted solar water splitting with concurrent high efficiency and stability by robust earth-abundant bifunctional electrocatalysts

Hydrogen production from solar water splitting, especially via photovoltaic-electrocatalysis, has been regarded as a promising approach for the conversion of abundant but intermittent solar energy into storable chemical fuels. Despite much progress, conventional combined photoelectrochemical devices usually suffer from severe instability issues, which largely inhibit them for practical applications and may also lead to the uncertain efficiency value for true overall water splitting. Here, we report an unassisted solar water splitting device with concurrent high efficiency and stability, which is constructed by spatial coupling of tandem III-V-based GaInP/GaAs/Ge light absorber and robust earth-abundant Ni foil-based MoNi4/MoO2 bifunctional electrocatalysts. Remarkably, apart from the outstanding hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) performance, bifunctional MoNi4/MoO2 electrocatalysts also largely avoid electrode contamination issues, while the robust Ni substrate protects III-Vs from conventional corrosion problems. Consequently, this integrated photovoltaic-electrolysis system device exhibits a high solar-to-hydrogen (STH) conversion efficiency of 17.6 % in alkaline electrolytes with long-term stability of up to 845 h. Further construction into a wireless unassisted monolithic device could lead to an artificial leaf with an STH efficiency of 4.28 %, holding great promise in future solar fuel production with concurrent high efficiency, good stability as well as low cost.

Effectiveness of a dual surface modification of metallic interconnects for application in energy conversion devices

A dual surface modification of an SOFC metallic interconnect with a Gd2O3 layer and an MnCo2O4 coating was evaluated. The tested samples were oxidized for 7000 h in air at 1073 K. Oxidation products were characterized using XRD, SEM-EDS, and confocal Raman imaging, and ASR was measured. The effect of gadolinium segregation at grain boundaries in Cr2O3 was evaluated using S/TEM-EDS. Area specific-resistance was measured and fuel cell tests investigating electrochemical performance and Cr contamination of electrodes were also performed. The results show that the proposed dual modification was more advantageous than either modification applied separately. The fuel cell tests performed after aging in humidified hydrogen at 1073 K and involving an actual interconnect made of this dual-modified material showed that after 250 h of aging its electrochemical parameters were nearly identical to those of the non-aged reference electrode. Moreover, the modification protected the electrodes from Cr poisoning.

Sensitivity Analysis of a Portable Wireless PCB-MEMS Permittivity Sensor Node for Non-Invasive Liquid Recognition.

Dielectric characteristics are useful to determine crucial properties of liquids and to differentiate between liquid samples with similar physical characteristics. Liquid recognition has found applications in a broad variety of fields, including healthcare, food science, and quality inspection, among others. This work demonstrates the fabrication, instrumentation, and functionality of a portable wireless sensor node for the permittivity measurement of liquids that require characterization and differentiation. The node incorporates an interdigitated microelectrode array as a transducer and a microcontroller unit with radio communication electronics for data processing and transmission, which enable a wide variety of stand-alone applications. A laser-ablation-based microfabrication technique is applied to fabricate the microelectromechanical systems (MEMS) transducer on a printed circuit board (PCB) substrate. The surface of the transducer is covered with a thin layer of SU-8 polymer by spin coating, which prevents it from direct contact with the Cu electrodes and the liquid sample. This helps to enhance durability, avoid electrode corrosion and contamination of the liquid sample, and to prevent undesirable electrochemical reactions to arise. The transducer’s impedance was modeled as a Randles cell, having resistive and reactive components determined analytically using a square wave as stimuli, and a resistor as a current-to-voltage converter. To characterize the node sensitivity under different conditions, three different transducer designs were fabricated and tested for four different fluids, i.e., air, isopropanol, glycerin, and distilled water—achieving a sensitivity of 1.6965 +/− 0.2028 εr/pF. The use of laser ablation allowed the reduction of the transducer footprint while maintaining its sensitivity within an adequate value for the targeted applications.

Electrode contamination caused by metal vapour transport during tungsten inert gas welding

Tungsten electrode contamination caused by metal vapour from a base metal during a tungsten inert gas welding was investigated. The metal ions transported from the weld pool surface were deposited on the tungsten electrode surface during welding. The tungsten fraction of the electrode surface layer was decreased because the deposited metal vapour diffused inside the tungsten electrode. The melting point of the electrode surface layer was lowered, decreasing to the electrode operating temperature. Results show that the electrode melted and deformed. This electrode contamination was promoted when a larger amount of metal ions was transported to the electrode surface.

Liquid-like Polymer Coating as a Promising Candidate for Reducing Electrode Contamination and Noise in Complex Biofluids.

Biosensors that can automatically and continuously track fluctuations in biomarker levels over time are essential for real-time sensing in biomedical and environmental applications. Although many electrochemical sensors have been developed to quickly and sensitively monitor biomarkers, their sensing stability in complex biofluids is disturbed by unavoidable nonspecific adhesion of proteins or bacteria. Recently, various substrate surface modification techniques have been developed to resist biofouling, yet functionalization of electrodes in sensors to be anti-biofouling is rarely achieved. Here, we report an integrated three-electrode system (ITES) modified with a "liquid-like" polydimethylsiloxane (PDMS) brush that can continuously and stably monitor reactive oxygen species (ROS) in complex fluids. Based on the slippery "liquid-like" coating, the modified ITES surface could prevent the adhesion of various liquids as well as the adhesion of proteins and bacteria. The "liquid-like" coating does not significantly affect the sensitivity of the electrode in detecting ROS, while the sensing performance could remain stable and free of bacterial attack even after 3 days of incubation with bacteria. In addition, the PDMS brush-modified ITES (PMITES) could continuously record ROS levels in bacterial-rich fluids with excellent stability over 24 h due to the reduced bacterial contamination on the electrode surface. This technique offers new opportunities for continuous and real-time monitoring of biomarkers that will facilitate the development of advanced sensors for biomedical and environmental applications.

Particulate matter emission control from small residential boilers after biomass combustion. A review

In this paper, lab and commercial constructions of electrostatic precipitators used for the removal of fly ash particles from small residential boilers have been reviewed. The presented solutions were evaluated in terms of removal efficiency, exploitation conditions or expected maintenance costs. Boilers used for household heating are the main sources of air contamination by particulate matter during winter seasons in many countries. The collection efficiency of such devices should be higher than 95% to comply with the ECODESIGN emission limit, and the emission level for biomass <20 mg/m3. It was shown that the collection efficiency of the lab-constructed and market-available electrostatic precipitators is too low to comply with these regulations. The difficulty with flue gas cleaning from residential boilers results from limited space in house, which determines the size of electrostatic precipitator. As a result, the available residence time of flue gases in the precipitation zone, which is one to two orders of magnitude shorter than in industrial precipitators, is too short to obtain the required emission level. Another important problem met in all of those constructions and not satisfactorily solved is the contamination of electrodes and their cleaning from tar deposit. There is an urgent need for the development of small electrostatic devices designed for exhaust gas cleaning from particles generated by small residential boilers, which could be integrated with such a boiler. The novelty of this review is a detailed analysis and comparison of parameters and performances of small electrostatic precipitators for cleaning exhaust gases from small residential boilers based on the data published in scientific research papers. An indication on the future research in this field was also provided in conclusion.

Electrochemical Conversion of Magnetic Nanoparticles Using Disposable Working Electrode in a 3D‐Printed Electrochemical Cell

AbstractExploration of new property/function of nanomaterials is always a strong impetus in the nanoscience field. Here, a new method of electrochemical conversion (ECC) of magnetic nanoparticles (MNPs) is proposed to endow MNPs with signal generation ability for sensing. Briefly, high potential was applied to split H2O to generate acid, while Fe3O4 MNPs reacted with H+ and produce ferric/ferrous ions, which further reacted with K4Fe(CN)6 to yield Prussian blue (PB) through potential cycling. The ECC method worked well on both home‐made and commercial MNPs with different sizes. The generated PB possessed strong electrochemical activity for further applications. Interestingly, an uneven deposition of PB on working electrode and undesired contamination of the reference and counter electrodes were found when using commercial integrated three‐electrode chip. A 3D‐printed electrochemical cell was designed to facilitate the ECC and avoid drawbacks of commercial integrated electrode. The 3D‐printed electrochemical cell was proven to solve the problem above through spatial separation of electrodes and thus facilitated the ECC process. An electrochemical sensor for H2O2 detection based on the catalysis ability of ECC‐based PB exhibited a linear response from 5 μM to 1 mM, a high sensitivity of 269 μA mM−1 cm−2 and a low detection limit of 0.16 μM (S/N=3), which suggests its promising application prospect in electrochemistry‐related analysis.

Alumina contamination through polishing and its effect on hydrogen evolution on gold electrodes

In this work we show how the contamination of gold electrodes with alumina particles by electrode polishing leads to an enhancement in activity for hydrogen evolution (HER). Polishing is one of the most used electrode treatments, however, we show that particles from the polishing media cannot be easily removed from the electrode surface by standard cleaning procedures. Comparing the HER activity of gold disc electrodes polished with either diamond suspension or alumina paste, we show that the latter leads to higher current densities, specifically for the water reduction to hydrogen. A similar enhancement in HER activity was observed by the addition of Al3+ cations to the electrolyte, demonstrating that the particles are not catalytically active, but that the Al3+ species released in solution due to corrosion promote the water reduction reaction. Due to an increase in the local OH− concentration during HER, the contaminating Al3+ cations precipitate and may deposit at the electrode surface as Al(OH)3. In the presence of a high enough Al3+ concentration, layered Al(OH)3 plates cover the whole electrode surface. The plates are composed of Al(OH)3 sheets intercalated by sulphate anions. Surprisingly, the Al(OH)3 sheets do not affect the gold blank voltammetry, and therefore remain undetected by simple electrochemical characterization methods.

Conductivity Measurement Using Non-Contact Potential Electrodes and a Guard Ring

This paper presents an improved method for the measurement of the conductivity of a liquid. In the proffered technique, the contact-type potential terminals of a traditional four lead conductivity probe are replaced with non-contacting terminals thus preventing electrode corrosion and contamination affecting the conductivity measurement. An additional guard electrode introduced in the present design ensures that the current through the external/surrounding medium becomes negligible thus reducing the error due to current flow, external to the probe. A self-balancing signal conditioning circuit, specially designed to suit the probe, alleviates the new problems of the modified probe. Simulation results and the results obtained from a prototype built and tested establish the efficacy of the proposed technique. The worst case error was found to be ± 0.78% with the prototype probe.

A Capacitive-Coupled Noncontact Probe for the Measurement of Conductivity of Liquids

A noncontact (capacitive-coupled) probe for the measurement of the conductivity of liquids is presented. Insulation introduced between the measurement electrodes and the liquid intrudes a couple of coupling capacitances. Though the capacitive coupling overcomes the problems of electrode polarization and contamination associated with contacting electrodes, the large reactances of the coupling capacitors pose a problem in the measurement of comparatively very small resistance of the liquid. An auto-balancing signal conditioning scheme presented here overcomes the problem posed by the large capacitive reactances and provides directly a measurable output proportional only to the conductance of the liquid. Error analysis of the probe presented herein helps the optimal design of the probe. A worst case error of ± 0.9% was obtained from a prototype noncontact conductivity probe, developed and tested.

Effect of dynamic wire in the GTAW process

Experimental tests were carried out to evaluate and compare metallic transfer aspects and welding process behavior, in GTAW with dynamic wire feeding in relation to conventional mode (wire insertion in a continuous way with constant speed / steady state). Inconel 625 cladded steel plates were laid out at four main welding positions (overhead, vertical up, vertical down and flat). The metallic transfer analysis was based on wire’s tip monitoring, by means of high speed videography and monitoring of the difference of electric potential between tungsten electrode, wire and plate. Continuous wire feeding resulted in rupture of the contact between wire and puddle, which generated large droplets on the wire’s tip, which transferred in irregular intervals. This fact is a common occurrence mainly out of flat position and incurs in irregularity of metal transfer and of oscillographic behavior. For dynamic wire feeding the amount of molten metal in the wire’ tip (droplet) was minimized and the transfer frequency became regular, rendering a more stable and robust process. Also, the risk of electrode contamination was reduced. The benefits of dynamic feeding were observed for both constant and pulsed current.

Contributions of the High Frequency Dynamic Wire Feeding in the GTAW Process for Increased Robustness

Abstract: The GTAW process is recognized as a process of high metallurgical quality, being widely used in the pipelines welding, mainly in the root pass. The relative independence between the heat delivered to the melting pool and the amount of material added helps to control the melting of the material and to avoid the appearance of welding discontinuities such as lack of fusion and lack ok penetration. When orbital welding is carried out, mainly in the overhead position, there is a tendency of electrode contamination by the melted wire, reducing process productivity and quality. In this scenario, there are some strands of the GTAW process that aim for increased productivity, reconciled with the already present high metallurgical quality. These includes low and high frequency dynamic wire feeding, preheating wire and tangential wire insertion. The present work deals with the contribution of the high frequency dynamic wire feeding for the increase of robustness in the GTAW process, evidencing through voltage monitoring and high speed filming the formation of regular and uniform drops for the process stability.

Nanomaterial Labels for Signal Amplification in Electrochemical Immunosensors

Electrochemical immunosensors function by measuring the changes in the electrical properties such as current, potential, conductance, capacitance, and impedance during an immunochemical reaction between antigen (target molecule) and the antibody [2,4]. Although capacitive and impedimetric immunosensors can be directly utilized to investigate the antibody-antigen interaction without the need of other reagents and separation steps, their analytical sensitivity is limited in clinical applications. Amperometric immunosensors based on the measurement of currents resulting from the electrochemical oxidation or reduction of electroactive species has attracted more interests for high sensitivity and low complexity instrumentation [4]. However, amperometric immunosensors requires labelling of either antigen or antibody, since both the reaction partners are electrochemically inert. Labelling is a time-consuming process, costly and denatures the biomolecules. Amperometric immunosensors that utilizes electrolyte solution containing reversible redox species, have been widely used as mediator probes instead of labelling antibodies/antigens; however, this causes electrode contamination, reagent-consumption and operation inconvenience. To solve these problems, immobilization of signal generating probe on electrode surfaces to construct label-free amperometric immunosensors has been proposed.

Nanomaterial Labels for Signal Amplification in Electrochemical Immunosensors

Electrochemical immunosensors are functions by measuring the changes in the electrical properties such as current, potential, conductance, capacitance, and impedance during an immunochemical reaction between antigen (target molecule) and the antibody(Pandiaraj et al., 2014; Vasudev et al., 2013). Although capacitive and impedimetric immunosensors can directly be utilized to investigate the antibody-antigen interaction without the need of other reagents and separation steps, their analytical sensitivity is limited in clinical applications. Amperometric immunosensors are based on the measurement of currents resulting from the electrochemical oxidation or reduction of electroactive species had attracted more interests recently for a higher sensitivity and less complicated instrumentation (Rusling et al., 2010). However, amperometric immunosensors requires labelling of either antigen or antibody, since both the reaction partners are electrochemically inert. Labelling is a time consuming process, costly and denatures the biomolecules. Amperometric immunosensors that utilizes electrolyte solution containing reversible redox species, such as ferrocene and its derivatives, dyes, hydroquinone, hexacyanoferrates etc. have been widely used as mediators or signal generating probes instead of labelling antibodies/antigens; however this would cause electrode contamination, reagent-consumption and operation inconvenience. To solve these problems, it should be preferable to immobilize the signal generating probe on electrode surfaces to construct label-free amperometric immunosensors. The use of nanomaterials as signal generating probes for electrochemical detection of biomarkers have been reviewed earlier (Liu and Lin, 2007). However, the selection of signal generating probe is very important for electrochemical immunosensor, especially for label-free electrochemical immunosensor, since it is responsible for three major tasks: (i) being redox active and produce electrochemical signals for corresponding immunocomplex formation, (ii) increasing specific surface area of electrode to immobilize more antibodies and improving conductivity for sensitive detection of antigen. For electrochemical devices, nanoparticles, carbon nanotubes and graphene have been used to catalyze electrochemical reactions and to improve electron transfer. Nanoparticles, especially have also been used as labels to generate intense signal in comparison with electroactive molecules or organometallic complexes like ferrocene. Indeed, due to their high number of atoms, huge number of electron can be exchanged through oxidation or reduction. Group 11 metals (Cu, Ag, and Au), which are very weak chemisorbers, often display marked catalytic and electrocatalytic properties. Some types of copper electrodes showed an excellent electrocatalytic activity for DNA detection without observable self-poisoning. Copper electrodes undergo oxidation at unexpectedly low potentials, typically within the so-called double layer region, to form surface-bonded copper(I) hydrous oxide species. A reagentless, label-free voltammetric immunosensing strategy was demonstrated by employing nanomaterial integrated electrode as a signal generating probe. Copper/copper oxide (Cu/CuxO) nanoparticles integrated screen printed carbon electrodes (SPCE) were used to construct the immunosensing platform. The stress biomarker, cortisol was employed as a model analyte. Cortisol specific monoclonal antibodies (C-Mab) were covalently immobilized on the surface of the Cu/CuxO-SPCE functionalized with dithiobis(succinimidyl propionate) (DTSP) self-assembled monolayer (SAM). The formation of Cu/CuxO nanoparticles on the surface of SPCE was characterized by scanning electron microscopy (SEM), and X-ray diffraction (XDR) analysis. The redox signal of the Cu/CuxO nanoparticles could be detected directly through cyclic voltammetry and used as signal generation probe for the direct detection of cortisol. The formation of immunocomplexes leads to a decrease in the electrochemical redox signal of Cu/CuxO nanoparticles owing to increased spatial blocking of the electrode surface. The proposed immunosensing strategy allows a rapid and sensitive means of cortisol analysis with a limit of detection of about 1 pg/mL. The Cu/CuxO platform can be further applied for designing other label-free immunoassays.