Constant Potential Amperometry Research Articles

A Storage-Dependent Platinum Functionalization with a Commercial Pre-Polymer Useful for Hydrogen Peroxide and Ascorbic Acid Detection.

A preliminary assessment of properties of the commercial product Chemiplus 2DS HB (BI-QEM Specialties SpA) is proposed. Cyclic voltammetry of this oligomer containing sulfate/sulfone groups shows a single oxidative peak at +0.866 V vs. Ag/AgCl, and its passivating process on Pt electrode suggests the formation of a non-conductive layer. Electrode modification was achieved by exploiting the constant potential amperometry setting potential at +0.900 V vs. Ag/AgCl. A substantial change in the oxidative currents from electroactive species H2O2 and ascorbic acid (AA) were observed on Pt/Chemiplus 2DS HB sensors compared to unmodified Pt. Furthermore, the influence of different storage conditions on modified sensors was examined. A storage solution containing AA concentration from 0.1 until 10 mM maintained effective AA rejection of Pt/Chemiplus 2DS HB after 7 days from construction; H2O2 oxidation capability was also retained. Sulfone and sulfonate groups of Chemiplus 2DS HB are likely responsible for the dimensionality of the film and the electrostatic interaction leading to a self-blocking/self-rejection of AA. The way Pt/Chemiplus can reveal the AA presence depends on the maintaining of AA rejection, and this peculiarity can distinguish it from other sensors or biosensors.

Rosa damascena waste mediated synthesis of silver nanoparticles: Characteristics and application for an electrochemical sensing of hydrogen peroxide and vanillin

Silver nanoparticles (AgNPs) were synthesized by reduction of Ag+ with four extracts of Rosa damascena waste: post-distillation water (PW), water extract (WE), 30% (30 EE) and 70% (70 EE) ethanol extracts. The ethanolic extracts were rich in polyphenols and particularly catechin and epicatechin (1388.01 ± 2.27 and 677.47 ± 2.03 μgmL−1, respectively) while the water extracts were rich in reducing sugars, proteins and pectic substances (for WE 254.21 ± 1.26, 296.89 ± 2.01 and 242.14 ± 1.38 μgmL−1, and for PW 185.72 ± 1.47, 298.30 ± 1.57 and 181.78 ± 1.39 μgmL−1, respectively). The morphology of AgNPs was characterized by transmission electron microscopy and the calculated average size of the AgNPs synthesized using WE and PW was 25.8 ± 11.5 nm and 11.5 ± 8.4 nm, respectively. The X-ray diffraction analysis suggested presence of silver phase which crystallized in a face centered cubic space group Fm-3m with unit cell parameter 4.085 (2) Å and mean coherent domain size 10.9 (3)nm. Biosynthesized AgNPs were deposited onto a spectroscopic graphite electrode (GE), applying two different procedures, and stabilized using chitosan to build modified electrodes-catalysts. The electrochemical performances of the modified electrodes AgNPs/GE and AgNPs/CS/GE were studied by means of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry at pH 7.0 and their applicability for amperometric detection of H2O2 and vanillin was investigated. The developed electrodes exhibited a sensitive and reproducible response for quantitative determination of H2O2 at applied potentials of −0.2, −0.25 and −0.3 V (vs. Ag/AgCl, 3 M KCl). Constant potential amperometry studies with AgNPs/CS/GE showed sensitive response to H2O2 (115.2 μA mM−1 cm−2) up to 6.6 mM at −0.3 V, and to vanillin (56.8 μA μM−1 cm−2) up to 0.5 mM with detection limit of 8.4 μM at 0.58 V. The results obtained from the quantitative electrochemical measurements of H2O2 and vanillin offer potential applications of the graphite electrodes modified with the biosynthesized AgNPs in electrochemical sensor devices for monitoring of these analytes.

In situ electrodeposition of cholesterol oxidase-modified polydopamine thin film on nanostructured screen printed electrodes for free cholesterol determination

The in situ electrodeposition of cholesterol oxidase (ChOx)-modified polydopamine (PDA) thin film on nanostructured-screen printed electrodes (SPEs) is described here. Prussian Blue (PB) and multi-wall carbon nanotubes (MWCNTs) were used for their outstanding properties in biosensing applications. Cyclic Voltammetry (CV), Constant Potential Amperometry (CPA) and Electrochemical Impedance Analysis (EIS) were used to confirm the correct electrodeposition of the enzyme-modified PDA thin film on the SPE. In addition, the assembly protocol was fully revised to optimize the biosensor response. The proposed cholesterol biosensor showed Michaelis-Menten behavior with KappM, Vmax and Hill parameter values of 1.97mM, 7.33μA and 1.06, respectively. Biosensor sensitivity, stability, reproducibility, repeatability and anti-interference properties were obtained and confirmed the feasibility of using this biosensor for cholesterol determination. In order to show the applicability of such an approach, the biosensor was incorporated in a Flow Injection Analysis (FIA) device and had a high sensitivity of 32.14mAM−1cm−2 (R2=0.999), a linear range over two orders of magnitude and a detection limit (S/N=3) of 1.5μM. The results confirmed the success of the biosensor for determining cholesterol in future applications in diagnostic laboratories.

An Electrochemical Sensing Platform Based on Iridium Oxide for Highly Sensitive and Selective Detection of Nitrite and Ascorbic Acid

Iridium oxide (IrOx) was electrodeposited onto glassy carbon electrode applying two-step potential cycling procedure. The electrocatalytic properties of the modified electrode IrOx/GC were evaluated with regards to electrochemical oxidation of nitrite and ascorbic acid (AA). The developed electrode-catalyst have been extensively studied by various electrochemical techniques. Differential pulse voltammetry (DPV) experiments indicated that the modified electrode possesses excellent electrocatalytic activity towards the oxidation of both nitrite and AA in neutral medium and offers simultaneous quantification of these substances. Constant potential amperometry studies also were performed - the IrOx/GC showed sensitive response to nitrite (159.7 μA mM-1 cm-2) with a wide linear range from 0.002 to 10 mM at 0.77 V (vs. Ag/AgCl, 3 M KCl), and to AA (96.2 µA mM-1cm-2) with a linear range from 0.01 to 3 mM at 0.025 V. The detection limit was 0.63 μM nitrite and 4 μM AA, respectively, and both of them had fast response within 5 s. Considering the simple and rapid electrodeposition procedure for preparation, IrOx/GC is a new electrode-catalyst for sensitive and selective quantitative detection of nitrite and AA. The wide linear range, good selectivity, reproducibility of the amperometric response and long-time stability of the IrOx/GC make it a promising sensing material for practical nonenzymatic quantitative detection of nitrite and AA.

Electrochemical detection of glucose at physiological pH using gold nanoparticles deposited on carbon nanotubes

There is currently considerable interest in the development of non–enzymatic glucose sensors and gold is one of the noble metals that enables the oxidation of glucose. Gold nanoparticles with a mean diameter of 7.5 nm were deposited onto the walls of functionalised carbon nanotubes to give a gold loading of 2.0% by weight. This composite was dispersed and cast onto glassy carbon and carbon screen printed electrodes. These electrodes were then used to detect glucose in a neutral phosphate buffer solution, corresponding to physiological pH. Using constant potential amperometry, a linear calibration curve was obtained with a sensitivity of 2.77 ± 0.14 μA/mM, a limit of detection, LOD, of 4.1 μM and a linear region extending to 25 mM. This sensor showed very good selectivity in the presence of ascorbic acid, galactose and fructose, but interference was observed in the presence of uric acid. This interference was eliminated by applying a Nafion® film to the composite electrodes. Due to a lower diffusion of glucose across the Nafion® barrier, the sensitivity of the Nafion® coated composite was reduced to 0.55 ± 0.03 μA/mM and the LOD was increased to 10.0 μM. However, a linear response between 0.1 mM and 25 mM was obtained, which covers the normal and elevated levels of glucose in blood. These sensors showed very good stability when stored in air and it was also possible to re–use the sensors.

Electrochemical detection of Cr(VI) with carbon nanotubes decorated with gold nanoparticles

A nanocomposite consisting of gold nanoparticles deposited on the side walls of functionalised multi-walled carbon nanotubes, Ox-MWCNT-Aunano, was prepared using a simple chemical reduction. The nanoparticles were well dispersed with a mean diameter of 7.5 nm and had a face-centred cubic structure and a gold loading between 2.0% and 2.6% by weight. These gold decorated nanotubes were cast onto a gold electrode to form a uniform and homogeneous sensor. Using cyclic voltammetry, the reduction of Cr(VI) was observed at a peak potential of 0.52 V versus SCE in an acidified H2SO4 solution, pH 2.0. A linear calibration curve with a sensitivity of 0.28 mA mM− 1 and a LOD of 7.2 × 10− 7 M was obtained using constant potential amperometry coupled with rotating disc voltammetry. The electrochemical detection of Cr(VI) was also observed at a MWCNT-modified gold substrate but with a higher LOD, illustrating the advantage of combining the gold nanoparticles with MWCNTs. The sensor showed good selectivity for the detection of Cr(VI) in the presence of Cu(II), chloride and nitrates and in a real water sample. This was attributed to the electropositive reduction potentials of Cr(VI), the acidic H2SO4 supporting electrolyte that provides a well-known cleaning effect at gold, and the size and good dispersion of the gold nanoparticles that minimise particle agglomeration.

Highly sensitive electrochemical detection of iodate based on glassy carbon electrode modified with iridium oxide

A glassy carbon electrode electrochemically modified with iridium oxide (IrOx) has been developed for amperometric quantitative detection of iodate. Two-step potential cycling was used to deposit layers of IrOx onto glassy carbon surface. A stable reversible redox couple was observed at the surface of modified electrode in both acidic and neutral solutions. The electrochemical behavior of the modified electrode IrOx/GC and the catalytic activity in electroreduction of iodate at pHs 1.0–4.0 were explored by means of cyclic voltammetry and constant potential amperometry over the potential range from 0.2 to − 0.2 V (vs. Ag/AgCl, 3 M KCl). As optimal operational parameters of IrOx/GC at pH 1.0 have been defined: working potential of − 0.2 V, sensitivity 739.7 µA mM−1 cm−2 (r2 = 0.982), linear dynamic range from 1.0 to 4.6 mM, detection limit of 0.5 µM and response time of 8 s. The modified electrode showed excellent analytical performance — high sensitivity, linearity, reproducibility (the precision for 5 replicate determinations of 0.1 mM iodate was 1.68% RSD), stability (92% of its initial response to iodate after 1 month), and remarkable anti-interference performance, defining it as a promising material for electrochemical sensor application.

Concurrent measurements of neurochemical and electrophysiological activity with microelectrode arrays: New perspectives for constant potential amperometry

Our current understanding of neurotransmission and neuromodulation stands to gain from concurrent electrochemical and electrophysiological measurements, which have been attempted since the introduction of in vivo electrochemical techniques. Dual in vivo recordings have evolved from parallel approaches using two distinct microelectrodes towards serial strategies encompassing “time-sharing” between two independent recording systems while using a single microelectrode. More recently, fast sampling amperometry has been demonstrated to allow concurrent measurement of rapid neurochemical and electrophysiological events using a single sensor and recording system. This is supported by the fact that the high-frequency component of an amperometric recording (>1 Hz) resembles the local field potential while the low frequency component (<1 Hz) reflects the electrochemical signal resulting from the oxidation or reduction of electroactive species present in the milieu. This opens new avenues for constant potential amperometry, widening the application of this seamless electrochemical technique.

A Bidirectional-Current CMOS Potentiostat for Fast-Scan Cyclic Voltammetry Detector Arrays.

A potentiostat circuit for the application of bipolar electrode voltages and detection of bidirectional currents using a microelectrode array is presented. The potentiostat operates as a regulated-cascode amplifier for positive input currents, and as an active-input regulated-cascode mirror for negative input currents. This topology enables constant-potential amperometry and fast-scan cyclic voltammetry (FSCV) at microelectrode arrays for parallel recording of quantal release events, electrode impedance characterization, and high-throughput drug screening. A 64-channel FSCV detector array, fabricated in a 0.5-$\mu$m, 5-V CMOS process, is also demonstrated. Each detector occupies an area of 45 $\mu$m $\times$ 30$\mu$m and consists of only 14 transistors and a 50-fF integrating capacitor. The system was validated using prerecorded input stimuli from actual FSCV measurements at a carbon-fiber microelectrode.

Use of β-cyclodextrin as enhancer of ascorbic acid rejection in permselective films for amperometric biosensor applications

Interference rejection in amperometric biosensors can be more effective introducing some modifiers during electro-deposition of permselective film. Addition of β-cyclodextrin (βCD), a cyclic oligosaccharide composed of seven glucose units, to the ortho-phenylendiamine (oPD) monomer were already demonstrated to provide an enhancement in ascorbic acid (AA) rejection. Here we evaluated the improvement in permselectivity of poly-eugenol and poly-magnolol films electro-polymerized in presence of different amounts of βCD or eugenol-βCD inclusion complex for amperometric biosensor application. Starting from Pt-Ir wire as transducer several microsensors were covered with polymeric films doped with βCD-based modifiers through constant potential amperometry. Characterization of modified polymers was achieved by scanning electron microscopy and permselectivity analysis. Poly-magnolol film in combination with βCD showed a worsening in permselectivity compared to poly-magnolol alone. In contrast, the introduction of βCD-based modifier enhanced the interference rejection toward the archetypal interferent AA, while slightly affecting permeability toward H2O2 compared to the poly-eugenol without modifier. The AA rejection seems to be influenced by the availability of βCD cavity as well as film performance due to concentration of βCD-Eugenol inclusion complex. A poly-eugenol film co-polymerized with 2 mM βCD-eugenol inclusion complex showed a permselectivity equal to poly-orthophenylendiamine film (PPD), with a lower permeability to AA, likely to be related with a self-blocking mechanism. Based on these results, a biosensor for glutamate was constructed with a poly-eugenol doped with βCD-eugenol as permselective layer and its permselectivity, stability and lifetime were determined.

Catalytic selectivity of metallophthalocyanines for electrochemical nitric oxide sensing

The catalytic properties of metallophthalocyanine (MPc) complexes have long been applied to electrochemical sensing of nitric oxide (NO) to amplify sensitivity and reduce the substantial overpotential required for NO oxidation. The latter point has significant ramifications for in situ amperometric detection, as large working potentials oxidize biological interferents (e.g., nitrite, l-ascorbate, and carbon monoxide). Herein, we sought to isolate and quantify, for the first time, the selectivity benefits of MPc modification of glassy carbon electrodes. A series of the most catalytically active MPc complexes towards NO, including Fe(II)Pc, Co(II)Pc, Ni(II)Pc, and Zn(II)Pc, was selected and probed for NO sensing ability under both differential pulse voltammetry (DPV) and constant potential amperometry (CPA). Data from DPV measurements provided information with respect to MPc signal sensitivity amplification (∼1.5×) and peak shifting (100–200 mV). Iron-Pc exerted the most specific catalytic activity towards NO over nitrite. Catalyst-enabled reduction of the working potential under CPA was found to improve selectivity for NO over high potential interferents, regardless of MPc. However, impaired selectivity against low potential interferents was also noted.

Direct Electrochemical Sensing of Hydrogen Sulfide without Sulfur Poisoning.

An electrochemical method capable of direct, real-time detection of hydrogen sulfide was developed using triple pulse amperometry (TPA) to mitigate sulfur poisoning and its related passivation of the working electrode surface. Through repeated cycles of discrete potential pulses, the electrooxidation of surface-adsorbed elemental sulfur to water-soluble sulfate ions was exploited to regenerate the glassy carbon electrode surface and maintain consistent sensor performance. Amperometric measurements and X-ray photoelectron spectroscopy surface analysis demonstrated that the TPA sensors provided enhanced analytical performance via decreased sulfur accumulation relative to low-potential (≤+0.7 V) constant potential amperometry. Sensors operated under optimized TPA parameters retained high sensitivity (57.4 ± 13.0 nA/μM), a wide linear dynamic range (150 nM-15 μM), fast response times (<10 s), and a submicromolar detection limit (<100 nM) upon consecutive calibration cycles. The sensitivity and response time achieved were comparable to or better than current electrochemical sensors. Moreover, the simplicity of the method eliminates the need for external redox mediators or semipermeable membranes.

Synthesis of Nitric Oxide Donors Derived from Piloty's Acid and Study of Their Effects on Dopamine Secretion from PC12 Cells.

This study investigated the mechanisms and kinetics of nitric oxide (NO) generation by derivatives of Piloty’s acid (NO-donors) under physiological conditions. In order to qualitatively and quantitatively measure NO release, electron paramagnetic resonance (EPR) was carried out with NO spin trapping. In addition, voltammetric techniques, including cyclic voltammetry and constant potential amperometry, were used to confirm NO release from Piloty’s acid and its derivatives. The resulting data showed that Piloty’s acid derivatives are able to release NO under physiological conditions. In particular, electron-withdrawing substituents favoured NO generation, while electron-donor groups reduced NO generation. In vitro microdialysis, performed on PC12 cell cultures, was used to evaluate the dynamical secretion of dopamine induced by the Piloty’s acid derivatives. Although all the studied molecules were able to induce DA secretion from PC12, only those with a slow release of NO have not determined an autoxidation of DA itself. These results confirm that the time-course of NO-donors decomposition and the amount of NO released play a key role in dopamine secretion and auto-oxidation. This information could drive the synthesis or the selection of compounds to use as potential drugs for the therapy of Parkinson’s disease (PD).

(Invited) Multimodal Microprobe for Combined Multiple Neurochemical Sensing and Optical Stimulation

Efforts to understand how neurons within networks interact to control behavior will be greatly facilitated by means with which to measure multiple neuroactive molecules in the brain simultaneously and in near-real time. We are developing an implantable microprobe capable of simultaneous rapid monitoring of three ubiquitous neurotransmitters/neuromodulators: dopamine (DA), glutamate (Glut), and acetylcholine. A detailed mathematical model is guiding electroenzymatic sensor optimization, and the use of a nanostructured Pt deposit has led to improved microsensors for choline and DA operated in constant potential amperometry mode. The creation of microsensor arrays for combined sensing of multiple neurochemicals is facilitated by the use of microcontact printing to deposit specific enzymes on selected microelectrode sites with fine control. Further, we are harnessing the power of optogenetics by incorporating an optical waveguide into our microprobes with microelectrode sensor arrays. This is achieved using an innovative silica-based microprobe design with embedded waveguides and a novel output grating coupler for directional illumination from the center of each neurochemical sensing site. The resultant microprobe enables local modulation of genetically isolated neuron terminals with measurement of transmitter release from those terminals. Our evaluation of probe performance in vivo has focused on the striatum and the basolateral amygdala (BLA). Optically evoked glutamate release has been observed successfully in the BLA of rats, but not in those genetically modified animals whose pre-synaptic activity is subjected to inhibition. Also, the improved DA sensors have enabled detection of electrical stimulation-evoked DA response in the rat dorsal striatum in the drug-naïve state. Further work to correlate multiple transmitter release events with behavioral actions will provide valuable information pertinent to the search for therapeutic interventions for multiple neurological and psychiatric disorders.

A DNA biosensor for molecular diagnosis of &amp;lt;i&amp;gt;Aeromonas hydrophila&amp;lt;/i&amp;gt; using zinc sulfide nanospheres

Abstract. Today, identification of pathogenic bacteria using modern and accurate methods is inevitable. Integration in electrochemical measurements with nanotechnology has led to the design of efficient and sensitive DNA biosensors against bacterial agents. Here, efforts were made to detect Aeromonas hydrophila using aptamers as probes and zinc sulfide (ZnS) nanospheres as signal enhancers and electron transfer facilitators. After modification of the working electrode area (in a screen-printed electrode) with ZnS nanospheres through electrodeposition, the coated surface of a modified electrode with ZnS nanospheres was investigated through scanning electron microscopy (SEM). The size of synthesized ZnS nanospheres was estimated at about 20–50 nm and their shape was in the form of porous plates in microscopic observations. All electrochemical measurements were performed using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and constant potential amperometry (CPA) techniques. The designed DNA biosensor was able to detect deoxyribonucleic acid (DNA) of Aeromonas hydrophila in the range 1.0 × 10−4 to 1.0 × 10−9 mol L−1; the limit of detection (LOD) in this study was 1 × 10−13 mol L−1. This DNA biosensor showed satisfactory thermal and pH stability. Reproducibility for this DNA biosensor was measured and the relative standard deviation (RSD) of the performance of this DNA biosensor was calculated as 5 % during 42 days.

Non-enzymatic hydrogen peroxide detection at NiO nanoporous thin film- electrodes prepared by physical vapor deposition at oblique angles

In this work we report a non-enzymatic sensor for hydrogen peroxide (H2O2) detection based on nanostructured nickel thin films prepared by physical vapor deposition at oblique angles. Porous thin films deposited on ITO substrates were characterized by X-ray diffraction analysis, scanning electron microcopy (SEMs), X-ray photoelectron spectroscopy (XPS) and electrochemical techniques such as Cyclic Voltammetry (CV) and Constant Potential Amperometry (CPA). The microstructure of the thin films consisted of inclined and separated Ni nanocolumns forming a porous thin layer of about 500nm thickness. Prior to their use, the films surface was electrochemically modified and the chemical state studied by CV and XPS analysis. These techniques also showed that Ni2+/Ni3+ species were involved in the electrochemical oxidation and detection of H2O2 in alkaline medium. Main analytical parameters such as sensitivity (807mAM−1cm−2), limit of detection (3.22μM) and linear range (0.011–2.4mM) were obtained under optimal operation conditions. Sensors depicted an outstanding selectivity and a high stability and they were successfully used to determine H2O2 concentration in commercial antiseptic solutions.

A Current-Integration-Based CMOS Amperometric Sensor with 1024 × 1024 Bacteria-Sized Microelectrode Array for High-Sensitivity Bacteria Counting

CMOS amperometric sensors with a microelectrode array offer great potential for counting bacteria because of their low cost, compact size, and ease of use. This paper presents a current-integration-based CMOS amperometric sensor for high-sensitivity bacteria counting. It has a current integrator for noise reduction and reportedly the most large-scale microelectrode array (1024 × 1024). This proposed sensor can count the number of bacteria ranging from a single cell to approximately a million cells. A prototype chip was fabricated using two-poly three-metal (2P3M) 0.6-µm standard CMOS technology. A 7.6 × 7.1-mm2 chip operates from a 5V supply at 1.9mA. In addition, by using the prototype chip, we performed electrochemical measurement and partial 2D imaging of silicone through constant potential amperometry. The measurement results indicate that the proposed sensor chip was able to accurately readout redox current from the 1024 × 1024 sensor array.

Nitric oxide permselectivity in electropolymerized films for sensing applications.

The presence of biological interferents in physiological media necessitates chemical modification of the working electrode to facilitate accurate electrochemical measurement of nitric oxide (NO). In this study, we evaluated a series of self-terminating electropolymerized films prepared from one of three isomers of phenylenediamine (PD), phenol, eugenol, or 5-amino-1-naphthol (5A1N) to improve the NO selectivity of a platinum working electrode. The electrodeposition procedure for each monomer was individually optimized using cyclic voltammetry (CV) or constant potential amperometry (CPA). Cyclic voltammetry deposition parameters favoring slower film formation generally yielded films with improved selectivity for NO over nitrite and l-ascorbate. Nitric oxide sensors were fabricated and compared using the optimized deposition procedure for each monomer. Sensors prepared using poly-phenol and poly-5A1N film-modified platinum working electrodes demonstrated the most ideal analytical performance, with the former demonstrating the best selectivity. In simulated wound fluid, platinum electrodes modified with poly-5A1N films proved superior with respect to the NO sensitivity and detection limit.

Rapid measurement of room temperature ionic liquid electrochemical gas sensor using transient double potential amperometry

Intense study on gas sensors has been conducted to implement fast gas sensing with high sensitivity, reliability and long lifetime. This paper presents a rapid amperometric method for gas sensing based on a room temperature ionic liquid electrochemical gas sensor. To implement a miniaturized sensor with a fast response time, a three electrode system with gold interdigitated electrodes was fabricated by photolithography on a porous polytetrafluoroethylene substrate that greatly enhances gas diffusion. Furthermore, based on the reversible reaction of oxygen, a new transient double potential amperometry (DPA) was explored for electrochemical analysis to decrease the measurement time and reverse reaction by-products that could cause current drift. Parameters in transient DPA including oxidation potential, oxidation period, reduction period and sample point were investigated to study their influence on the performance of the sensor. Oxygen measurement could be accomplished in 4s, and the sensor presented a sensitivity of 0.2863μA/[%O2] and a linearity of 0.9943 when tested in air samples with different oxygen concentrations. Repeatability and long-term stability were also investigated, and the sensor was shown to exhibit good reliability. In comparison to conventional constant potential amperometry, transient DPA was shown to reduce relative standard deviation by 63.2%. With transient DPA, the sensitivity, linearity, repeatability, measurement time and current drift characteristics demonstrated by the presented gas sensor are promising for acute exposure applications.

An improved glycerol biosensor with an Au-FeS-NAD-glycerol-dehydrogenase anode

An improved glycerol biosensor was developed via direct attachment of NAD+-glycerol dehydrogenase coenzyme-apoenzyme complex onto supporting gold electrodes, using novel inorganic iron (II) sulfide (FeS)-based single molecular wires. Sensing performance factors, i.e., sensitivity, a detection limit and response time of the FeS and conventional pyrroloquinoline quinone (PQQ)-based biosensor were evaluated by dynamic constant potential amperometry at 1.3V under non-buffered conditions. For glycerol concentrations ranging from 1 to 25mM, a 77% increase in sensitivity and a 53% decrease in detection limit were observed for the FeS-based biosensor when compared to the conventional PQQ-based counterpart. The electrochemical behavior of the FeS-based glycerol biosensor was analyzed at different concentrations of glycerol, accompanied by an investigation into the effects of applied potential and scan rate on the current response. Effects of enzyme stimulants ((NH4)2SO4 and MnCl2·4H2O) concentrations and buffers/pH (potassium phosphate buffer pH 6–8, Tris buffer pH 8–10) on the current responses generated by the FeS-based glycerol biosensor were also studied. The optimal detection conditions were 0.03M (NH4)2SO4 and 0.3µm MnCl2·4H2O in non-buffered aqueous electrolyte under stirring whereas under non-stirring, Tris buffer at pH 10 with 0.03M (NH4)2SO4 and 30µm MnCl2·4H2O were found to be optimal detection conditions. Interference by glucose, fructose, ethanol, and acetic acid in glycerol detection was studied. The observations indicated a promising enhancement in glycerol detection using the novel FeS-based glycerol sensing electrode compared to the conventional PQQ-based one. These findings support the premise that FeS-based bioanodes are capable of biosensing glycerol successfully and may be applicable for other enzymatic biosensors.