Electrooxidation Of Hydrogen Peroxide Research Articles

The enhanced TiO2-supported CdTe photocatalysts for photocatalytic hydrogen peroxide electrooxidation

At present, titanium dioxide (TiO2)-supported CdTe photocatalysts were prepared by wet impregnation method for photocatalytic hydrogen peroxide (H2O2) electrooxidation. The structural and morphology surface analyses of these photocatalysts were characterized by X-Ray diffraction (XRD), scanning electron microscopy-energy dispersive X-Ray (SEM-EDX) and mapping analysis, high-resolution transmission electron microscopy (HR-TEM), ultraviolet–visible (UV–VIS) spectroscopy, X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS). In addition, the photocatalytic activity of the photocatalysts was examined by cyclic voltammetry (CV). The CdTe(70–30)/TiO2 photocatalyst exhibited the best photocatalytic activity under UV illumination with a specific activity of 17.28 mA/cm2 both in the dark (7.86 mA/cm2) and compared to other photocatalysts. Furthermore, it was observed that it exhibited the best stability and resistance by chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS) analyses. It could be a promising photoanode catalyst for photocatalytic fuel cells.

L-Glutamate Biosensor for In Vitro Investigations: Application in Brain Extracts

Investigations of L-glutamate release in living organisms can help to identify novel L-glutamate-related pathophysiological pathways, since abnormal transmission of L-glutamate can cause many neurological diseases. For the first time, a nitrogen-modified graphene oxide (GO) sample (RGO) is prepared through a simple and facile one-pot hydrothermal reduction of GO in the presence of 20 wt.% of the dye malachite green and is used for amperometric biosensing. The biosensor demonstrates adequate stability and is easy to prepare and calibrate. The biosensor detects the current generated during the electrooxidation of hydrogen peroxide released in the L-glutamate that is converted to the alpha-ketoglutarate catalyzed by L-glutamate oxidase. The biosensor consists of a semipermeable membrane, with L-glutamate oxidase (EC 1.4.3.11) immobilized in albumin and RGO and the working Pt electrode. First, the basic version of the L-glutamate biosensor is examined in PBS to investigate its sensitivity, reliability, and stability. To demonstrate the applicability of the L-glutamate biosensor in the analysis of complex real samples, quantification of L-glutamate in bovine brain extract is performed and the accuracy of the biosensor is confirmed by alternative methods. The enhanced version of the L-glutamate biosensor is applied for L-glutamate release investigations in a newly developed strain of rats (DAT-knockout, DAT-KO).

Boron-Intercalation-Induced Phase Evolution of Rh Metallene for Energy-Saving H2 Production by H2 O2 Oxidation Coupled with Water Electrolysis.

Tailoring the morphology and crystal structure of metallene is critical to improve its electrocatalytic performance. In this work, hetero-phase RhB metallene (h-RhB metallene) with amorphous/crystalline structure is readily prepared by a two-step method. The h-RhB metallene is very unique in its non-metallic heteroatom doping and amorphous/crystalline structure. Benefiting from the unique metallene structure and the optimized electronic states induced by the incorporation of B atoms, the h-RhB metallene exhibits superior performance for hydrogen evolution reaction and hydrogen peroxide electro-oxidation reaction (HPOR). When coupled with HPOR, the h-RhB metallene||h-RhB metallene water electrolysis two-electrode system exhibits a lower cell voltage of 0.379V (@ 10mA cm-2 ) compared with the overall water splitting (1.35V). The presented synthetic method provides a powerful strategy to design metallene with hetero-phase for energy-saving H2 production.

A novel graphite modified paper based cobalt-cobalt oxalate-nickel electrode for the electrooxidation of hydrogen peroxide

The use of fossil energy has caused a serious burden on the environment, so it is urgent to find new and developable energy sources. H2O2 as a new type of clean fuel for fuel cell has received widespread attention. In this paper, a novel graphite modified paper based cobalt-cobalt oxalate-nickel ([email protected]–CoC2O4–Ni) electrode is fabricated by the simple “pencil depicting-electrodeposition-oxalic acid etching-electrodeposition” process for the electrooxidation of H2O2 in alkaline environment. The as-prepared [email protected]–CoC2O4–Ni electrode owns a novel and special three-dimensional (3D) porous structure, which can greatly increase the diffusion of reactants (NaOH and H2O2) during the electrochemical reaction process and lead a high catalytic activity for the electrooxidation of H2O2. More importantly, three main nanomaterial (Co, CoC2O4 and Ni) and some new generated substances during the CV test in NaOH solution (e.g. Ni(OH)2, NiOOH, Co(OH)2, CoOOH, Co3O4 and Co2O3 etc.) are on the surface of paper, which will enhance the electrocatalytic activity of the [email protected]–CoC2O4–Ni electrode to a great extent due to their synergistic effect. When the reaction solution contains 1.0 mol dm−3 NaOH and 0.2 mol dm−3 H2O2, the [email protected]–CoC2O4–Ni electrode exhibits a much higher oxidation current density (270.6 mA cm−2) than the FG, [email protected], [email protected], [email protected]–Ni and [email protected]–CoC2O4 electrodes. Besides, the whole preparation process for the [email protected]–CoC2O4–Ni electrode doesn't use any organic binder, ensuring the electrode owns good conductivity and stability for the electrochemical reaction. At last, the electrocatalytic mechanism for the electrooxidation of H2O2 is discussed. The Ni compounds and Co compounds are believed as the main catalytic substances, and the metallic Co core provides a fast route for the transfer of electrons. The super catalytic activity makes the prepared electrode in this study to be a promising material for the electrooxidation of H2O2 and the novel design idea gives some guidance for the fabrication of electrode materials in the field of fuel cell.

Sulfonated graphene-modified electrodes for enhanced capacitive performance and improved electro-oxidation of hydrogen peroxide

Electrochemical studies of graphene oxide (GO) containing sulfur-oxygen functional group (sulfonated graphene) and its application as electrode material for supercapacitor and electrocatalytic oxidation of H2O2 are demonstrated in this report. The sulfonated graphene (SGO) was synthesized using uniform heating of a homogeneous mixture of GO and ammonium sulfate at an elevated temperature ∼245 °C and characterized using FTIR, UV–Vis spectroscopy, and transmission electron microscopy. The electrochemical characterizations showed that the SGO exhibit the capacitance value as high as 248 F/g at current density 0.15 A/g along with superior cyclic stability (∼80% retention of cyclic stability after 8000 cycles). Also, SGO showed excellent electrocatalytic activity towards H2O2 oxidation and further, an electrochemical sensor for H2O2 detection was fabricated in an aqueous medium with ultra-low detection limit and high sensitivity. The oxidation current was found to be increased linearly with H2O2 concentration in the range of 10–100 μM and 0.1–1 mM with a detection limit of 10.44 μM and 0.038 mM respectively. The detailed kinetic study, including evaluation of kinetic parameters of the electro-oxidation process was also performed from the cyclic voltammetry study. We believe that this work will pave pathways towards diverse functional applications including electrocatalysis, non-enzymatic sensing in medical devices, energy harvesting and storage.

Enhanced Electrocatalytic Behaviour of Poy(aniline-co-2-hydroxyaniline) Coated Electrodes for Hydrogen Peroxide Electrooxidation

Polymer-coated electrodes are widely used for the detection and oxidation of hydrogen peroxide (H2O2). Conducting polyaniline (PANI), poly (2-hydroxyanilne) (PHA), and their copolymer poly(aniline-co-2-hydroxyaniline) (PACHA) were electrochemically synthesized on a gold substrate for H2O2 detection and analysis. Cyclic voltammetry (CV), square wave voltammetry (SWV), and differential pulse voltammetry (DPV) techniques were used for electroanalysis. Both PACHA and PANI greatly reduced the gold overpotential for H2O2 oxidation with enhanced current densities. The PACHA- and PANI-coated electrodes showed oxidative peaks at 0.30 and 0.50 V, respectively, in the presence of 1.4 × 10−6 M H2O2, while PHA-coated electrodes exhibited no response. The fabricated electrodes displayed a linear response towards H2O2 in range of 2 × 10−7 to 1.4 × 10−6 M, with very low detection limits (LODs) of 1 × 10−7 M (for PACHA) and 1.15 × 10−7 M (for PANI) evaluated from CV data. In case of SWV and DPV, the LODs were found to be 1.78 × 10−7 M (for PACHA) and 1 × 10−7 M (for PANI), respectively. The materials exhibit high sensitivity of 650 A/Mcm2 and show good stability. The PACHA-coated electrode shows better capacitance (1.84 × 10−3 F) than PHA- (2.52 × 10−4 F) and PANI-coated (1.17 × 10−3 F) electrodes.

Ni–SiO2 nanoporous composite as an efficient electrocatalyst for the electrooxidation of hydrogen peroxide

Nickel has attracted much attention as a cheap and readily available electrocatalyst towards the electrooxidation of hydrogen peroxide (H2O2). For the electrocatalytic reaction, the larger the surface area of the electrode, the more active sites can be provided, and the better the catalytic performance of the electrode can be achieved. In this paper, a three-dimensional (3D) porous electrode was successfully prepared by a simple two-step method. Firstly, the Ni–SiO2 composite was uniformly deposited on the carbon paper (CP) by electrodeposition, and then the SiO2 component in the Ni–SiO2 composite was removed by after dealloying (AD) to form a Ni–SiO2/CP (AD) electrode with a 3D porous structure, which has high catalytic activity area and good gas–liquid mass transfer property. The prepared Ni–SiO2/CP (AD) exhibits superior catalytic activity for H2O2 electrooxidation. At normal temperature, Ni–SiO2/CP (AD) in 1.0 mol dm−3 NaOH + 0.2 mol dm−3 H2O2 electrolyte solution, the oxidation current density reached 355 mA cm−2, which is 1.85 times the Ni/CP current density under the same conditions. This study provides a new idea for preparation of high catalytic activity of Ni catalyst for the electrooxidation of H2O2.

High‐Temperature Atomic Mixing toward Well‐Dispersed Bimetallic Electrocatalysts

AbstractSupported bimetallic alloy nanoparticles are of great interest in various catalytic applications due to the synergistic effects between different metals for improved catalytic performance. However, it still remains a challenge to efficiently synthesize atomically mixed alloy nanoparticles with uniform dispersion onto a desired substrate. Here, in situ, rapid synthesis of atomically mixed bimetallic nanoparticles well‐dispersed on a conductive carbon network via a 1 s high‐temperature pulse (HTP, ≈1550 K, duration 1 s, the rate of 104 K s−1) is reported. The high temperature facilitates the total (atomic) mixing of different metals, while the rapid quenching ensures the uniform dispersion of nanoparticles with fine features such as twin boundaries and stacking faults, which are potentially beneficial to their catalytic performance. By varying the ratio of the precursor salts and parameters in the HTP process, the composition, size, and morphology of the resultant nanoparticles can easily be tuned. Moreover, the synthesized bimetallic (PdNi) nanoparticles demonstrate excellent electrocatalytic performance for the hydrogen evolution reaction and hydrogen peroxide electrooxidation. This work provides a general strategy for a facile and rapid synthesis of bimetallic nanoparticles directly from their salts for a range of emerging applications.

Carbon- and Binder-Free Core-Shell Nanowire Arrays for Efficient Ethanol Electro-Oxidation in Alkaline Medium.

To achieve high electrochemical surface area (ECSA) and avoid carbon support and binder in the anode catalyst of direct ethanol fuel cell, herein, we design freestanding core-shell nickel@palladium-nickel nanowire arrays (Ni@Pd-Ni NAs) without carbon support and binder for high-efficiency ethanol electro-oxidation. Bare Ni nanowire arrays (Ni NAs) are first prepared using the facile template-assistant electrodeposition method. Subsequently, the Ni@Pd-Ni NAs are formed using one-step solution-based alloying reaction. The optimized Ni@Pd-Ni NA electrode with a high ECSA of 64.4 m2 g-1Pd exhibits excellent electrochemical performance (peak current density: 622 A g-1Pd) and cycling stability for ethanol electro-oxidation. The facilely obtained yet high-efficiency core-shell Ni@Pd-Ni NA electrode is a promising electrocatalyst, which can be utilized for oxygen reduction reaction, urea, hydrazine hydrate, and hydrogen peroxide electro-oxidation, not limited to the ethanol electro-oxidation.

Electrochemical sensing of hydrogen peroxide using brominated graphene as mimetic catalase

Recently we have reported the peroxidase mimicking ability of metal free brominated graphene (GBR) (Analytical Chemistry, 89, 783–791, 2017) at a pH less than 7.2. Here we report the novel catalase mimicking ability of GBR via electrochemical (electro-oxidation) detection of hydrogen peroxide (H2O2) at pH ≥ 7.2. We have fabricated successfully a low cost electrochemical sensor using GBR coated glassy carbon electrode (GCE) [(GBR-GCE)-working electrode] and showed its excellent cyclic voltametry (CV) response towards electro-oxidation of hydrogen peroxide (H2O2), which is so far shown by electrodes made of platinum-group metals like Pt, Ir, Ru etc. Thus, GBR has exhibited the dual mimicking ability as peroxidase and also as catalase under different conditions. A plausible mechanism of sensing of hydrogen peroxide has been proposed involving the formation of perhydroxyl radical (HO2˙) facilitated by GBR-GCE as the electrode. Calibration curves for H2O2 detection using both CV and differential pulse voltametry (DPV) techniques have been constructed over 0.1–10 mM linearity range with the limits of detection of 0.048 and 0.063 mM, respectively. This fabricated electrochemical sensor is highly selective, specific and its response current is least affected by the presence of interfering analytes. The results are found highly reproducible and the use of GBR has also minimized the problem and specificity associated with natural enzymes, as it can easily be stored at room temperature. Real samples have also been successfully analyzed using our fabricated sensor.

Electrochemical Generation of Individual O2 Nanobubbles via H2O2 Oxidation.

Herein, we use Pt nanodisk electrodes (apparent radii from 4 to 80 nm) to investigate the nucleation of individual O2 nanobubbles generated by electrooxidation of hydrogen peroxide (H2O2). A single bubble reproducibly nucleates when the dissolved O2 concentration reaches ∼0.17 M at the Pt electrode surface. This nucleation concentration is ∼130 times higher than the equilibrium saturation concentration of O2 and is independent of electrode size. Moreover, in acidic H2O2 solutions (1 M HClO4), in addition to producing an O2 nanobubble through H2O2 oxidation at positive potentials, individual H2 nanobubbles can also be generated at negative potentials. Alternating generation of single O2 and H2 bubbles within the same experiment allows direct comparison of the critical concentrations for nucleation of each nanobubble without knowing the precise size/geometry of the electrode or the exact viscosity/temperature of the solution.

Immobilization of glucose oxidase onto a novel platform based on modified TiO2 and graphene oxide, direct electrochemistry, catalytic and photocatalytic activity

In this work a new organic–inorganic nanocomposite has been introduced for enzyme immobilization. The composite consisting of graphene oxide (GO) and titanium oxide nanoparticles (TiO2) modified with 2, 2′-dithioxo-3, 3′-bis (3-(triethoxysilyl) propyl)-2H, 2′H-[5, 5′-bithiazolylidene]-4, 4′(3H, 3′H)-dione as Organic-Inorganic Supporting Ligand (OISL). The OISL was covalently attached to TiO2 nanoparticles and employed for obtaining a suitable solid surface to enzyme attachment. The glucose oxidase (GOD) was irreversibly loaded on the GC/GO/TiO2-OISL using consecutive cyclic voltammetry. The enzyme immobilization and the enzymatic activity were determined by electrochemical methods. The cyclic voltammogram displayed a pair of well-defined and nearly symmetric redox peaks with a formal potential of −0.465V and an apparent electron transfer rate constant of 1.74s−1. The GO/TiO2-OISL can catalyze the electroreduction and electrooxidation of hydrogen peroxide. The GC/GO/TiO2-OISL/GOD electrode was used in the hydrogen peroxide determination. The fabricated nanobiocomposite shows dramatic photoelectrocatalytic activity which evaluated by studying the electrocatalytic activity of the fabricated electrode toward hydrogen peroxide in darkness and in the presences of light.

Nickel-Zeolite modified carbon paste electrode as electrochemical sensor for hydrogen peroxide

In the present work, nickel-zeolite modified carbon paste electrode (Ni-ZMCPE) was prepared. The electrochemical behaviour of hydrogen peroxide at the surface of modified electrode was investigated by cyclic voltammetry and chronoamperometry in 0.1 M NaOH supporting electrolyte. The electrochemical characterization of Ni-ZMCPE exhibits redox behavior of Ni(III)/Ni(II) couple in alkaline medium. It has been shown that Ni-ZMCPE improves efficiency of the modified electrode toward hydrogen peroxide electrooxidation (It wasn’t remarkable different on ZMCPE and CPE in the presence and absence of hydrogen peroxide). Moreover, the effects of various parameters such as effect of different percents of Ni-Z to graphite, effect of pH and hydrogen peroxide concentration on the electrooxidation of hydrogen peroxide as well as stability of the Ni-ZMCPE have also been investigated. Under the selected conditions, the anodic peak current was linearly dependent on the concentration of hydrogen peroxide in the range 0.03–0.1 and 0.3–6 mM with amperometric method. The detection limit (S/N = 3) was also estimated to be 1 μM.

Synthesis of hexagonal CoAl-layered double hydroxide nanoshales/carbon nanotubes composite for the non-enzymatic detection of hydrogen peroxide

A nanocomposite comprising hexagonal CoAl-layered double hydroxide nanoshales with multiwall carbon nanotubes (MWCNTs) was synthesized by reflux heating. The nanocomposite was then applied to modify a carbon paste electrode. The modified electrode was then applied to fabricate a non-enzymatic hydrogen peroxide sensor. Hydrogen peroxide was electrocatalytically oxidized on the modified electrode surface, while its electroreduction was performed by an enhanced direct electron transfer to the electrode surface. The catalytic rate constants of the hydrogen peroxide electrooxidation were processed by an active cobalt species, and the diffusion coefficient of hydrogen peroxide was reported. An amperometric method was developed for determination of hydrogen peroxide based on its electrocatalytic oxidation with a sensitivity of 118.0mAdm3mol−1cm−2 and a limit of detection of 10μmoldm−3. In addition, amperometric method based on hydrogen peroxide electroreduction had a sensitivity of 42.0mAdm3mol−1cm−2 and a limit of detection of 40μmoldm−3. The sensor had the advantages of high activity and sensitivity, with a simple fabrication method without complications of immobilization steps and using any enzyme or reagent.

Low Potential and Non-Enzymatic Hydrogen Peroxide Sensor Based on Copper Oxide Nanoparticle on Activated Pencil Graphite Electrode

An electrochemical sensor for H2O2 determination was prepared by electrodepositing copper oxide nanoparticles on the activated pencil graphite electrodes. At first, a study has been made of the optimum conditions for chemical activation of the pencil graphite electrodes (APGE) and then the activated pencil graphite electrode was modified with copper oxide nanoparticles (CuO/APGE) and used as a non-enzymatic hydrogen peroxide sensor. The morphology of the modified electrode surface was investigated by scanning electron microscopy (SEM). Upon the addition of H2O2, the modified electrode (CuO/APGE) exhibits significant oxidation of H2O2 with starting potential around +0.05 V (vs. Ag/AgCl) which dramatically decreases the overpotential of H2O2 oxidation. Under the optimal experiment conditions, the electrocatalytic response current of this sensor was proportional to the H2O2 concentration in the range of 5.0 × 10-6 to 1.6 × 10-3 mol L-1 with a detection limit down to 0.21 µmol L-1 (signal/noise = 3). The sensitivity was calculated to be 4.75 µAL mmol-1. The electrochemical active surface area and the catalytic rate constant of hydrogen peroxide electro-oxidation were calculated. The H2O2 sensor exhibited a low detection limit, a good signal reproducibility (relative standard deviation (RSD), n = 4) 2.36% and the accurate measurements in milk as the real sample.

Nickel nanowire arrays electrode as an efficient catalyst for urea peroxide electro-oxidation in alkaline media

Urea peroxide as a solid-state fuel instead of liquid hydrogen peroxide is electro-catalytic oxidized by nickel nanowire arrays (NWAs) electrode. Nickel NWAs electrode is prepared by galvanostatically electrodepositing nickel into the pores and over-plating on the surface of polycarbonate template (PCT) from nickel bath solution. The NWAs are obtained after dissolving PCT in methylene chloride. Results show that urea peroxide decomposes into hydrogen peroxide and urea in aqueous solutions, then is electro-oxidized via two processes: i, hydrogen peroxide electro-oxidation at lower potential region; ii, both hydrogen peroxide and urea electro-oxidation at higher potential region. The onset oxidation potential and current density of urea peroxide electro-oxidation in 6.0molL−1 KOH and 1.0molL−1 urea peroxide are ca. -0.2V and 700mAcm−2 at 0.6V, respectively. The nickel NWAs electrode demonstrates excellent stability for urea peroxide electro-oxidation under different polarization potentials.

Functionalization of bamboo-like carbon nanotubes with 3-mercaptophenylboronic acid-modified gold nanoparticles for the development of a hybrid glucose enzyme electrochemical biosensor

We report for the first time a sensitive and selective glucose biosensor based on the immobilization at glassy carbon electrodes (GCE) of a new hybrid nanomaterial consisting of gold nanoparticles functionalized with 3-mercaptophenyl boronic acid (AuNPs-B(OH)2) and bamboo-like multiwall carbon nanotubes (bMWCNT) dispersed in hyperbranched polyethyleneimine (PEI). The presence of boronic acid residues allowed the supramolecular immobilization of glucose oxidase (GOx) as a model glycoenzyme while the hybrid nanomaterial Au(NP)-bMWCNT produces a synergistic effect on the catalytic detection of the enzymatically generated hydrogen peroxide. The resulting functionalized nanomaterials were characterized by TEM, FT-IR and electrochemical techniques. The sensitivity at 0.700V was (3.26±0.03)mAM−1 (28.6mAM−1cm−2), with a linear range between 2.50×10−4M and 5.00×10−3M, a detection limit of 0.8μM and a quantification limit of 2.4μM. The biocatalytic layer demonstrated to be highly reproducible with R.S.D. values of 8.6% for 10 successive amperometric calibrations using the same surface, and 4.5% for ten different bioelectrodes. The sensitivity of the biosensor after 14 days of storage at 4°C remained at 86.1% of its original value. The combination of the excellent dispersing properties of PEI, the stability of the bMWCNT-PEI dispersion, the synergistic effect of AuNPs-B(OH)2 and bMWCNT towards the electrooxidation of hydrogen peroxide, and the robust immobilization of GOx at AuNP-B(OH)2 allowed building a sensitive, reproducible and stable amperometric biosensor for the quantification of glucose in beverages and milk samples.

Single step synthesis of a ‘silver–polymer hybrid material’ and its catalytic application

Silver nanoparticle catalysed electro-oxidation of hydrogen peroxide.

Cobalt nano-sheet supported on graphite modified paper as a binder free electrode for peroxide electrooxidation

A novel and binder free Co@graphite/paper electrode is prepared by electrodeposition Co nano-sheet on the surface of a graphite layer modified paper substrate. The morphology and phase structure of the Co@graphite/paper electrode are characterized by scanning electron microscopy equipped with energy dispersive X-ray spectrometer, transmission electron microscope and X-ray diffractometer. The catalytic activity of the Co@graphite/paper electrode for H2O2 electrooxidation is investigated by means of cyclic voltammetry and chronoamperometry. The catalyst combines tightly with the paper and exhibits a good stability. The oxidation current density reaches to 580mAcm−2 in 2mol dm−3 NaOH and 0.5mol dm−3 H2O2 at 0.5V. Besides, we illustrate the reaction mechanization of the H2O2 electrooxidation on the Co film.

Glutamate biosensors based on diamond and graphene platforms.

l-Glutamate is one of the most important neurotransmitters in the mammalian central nervous system, playing a vital role in many physiological processes and implicated in several neurological disorders, for which monitoring of dynamic levels of extracellular glutamate in the living brain tissues may contribute to medical understanding and treatments. Electrochemical sensing of glutamate has been developed recently mainly using platinum, carbon fibre and carbon nanotube electrodes. In the present work, we explore the fabrication and properties of electrochemical glutamate sensors fabricated on doped chemical vapour deposition diamond electrodes and graphene nanoplatelet structures. The sensors incorporate platinum nanoparticles to catalyse the electrooxidation of hydrogen peroxide, glutamate oxidase to oxidise glutamate, and a layer of poly-phenylenediamine to impart selectivity. The performance of the devices was compared to a similar sensor fabricated on glassy carbon. Both the diamond and the graphene sensor showed very competitive performance compared to the majority of existing electrochemical sensors. The graphene based sensor showed the best performance of the three investigated in terms of sensitivity, linear dynamic range and long term stability, whereas it was found that the diamond device showed the best limit of detection.