WO2015000769A1 - Capteurs électrochimiques à base de diamant dopé par du bore - Google Patents

Capteurs électrochimiques à base de diamant dopé par du bore Download PDF

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WO2015000769A1
WO2015000769A1 PCT/EP2014/063439 EP2014063439W WO2015000769A1 WO 2015000769 A1 WO2015000769 A1 WO 2015000769A1 EP 2014063439 W EP2014063439 W EP 2014063439W WO 2015000769 A1 WO2015000769 A1 WO 2015000769A1
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electrode
diamond
sensing electrode
changing
sensing
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PCT/EP2014/063439
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English (en)
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Julie Victoria Macpherson
Mark Edward NEWTON
Patrick Robert Unwin
Eleni Bitziou
Nicola Louise PALMER
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Element Six Technologies Limited
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/308—Electrodes, e.g. test electrodes; Half-cells at least partially made of carbon
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/28—Electrolytic cell components
    • G01N27/30—Electrodes, e.g. test electrodes; Half-cells
    • G01N27/302—Electrodes, e.g. test electrodes; Half-cells pH sensitive, e.g. quinhydron, antimony or hydrogen electrodes

Definitions

  • Certain embodiments of the present invention relate to a diamond based electrochemical sensor a method of detecting a target chemical species in a solution using a diamond based electrochemical sensor.
  • Electrochemical sensors are well known. It has also been proposed in the prior art to provide a diamond based electrochemical sensor. Diamond can be doped with boron to form semi-conductive or fully metallic conductive material for use as an electrode. Diamond is also hard, inert, and has a very wide potential window making it a very desirable material for use as a sensing electrode for an electrochemical cell, particularly in harsh chemical, physical, and/or thermal environments which would degrade standard metal based electrochemical sensors. In addition, it is known that the surface of a boron doped diamond electrode may be functionalized to sense certain species in a solution adjacent the electrode.
  • diamond material is inherently difficult to manufacture and form into suitable geometries for sophisticated electrochemical analysis.
  • diamond electrodes utilized as sensing electrodes in an electrochemical cell have tended to be reasonably simple in construction and mostly comprise the use of a single piece of boron doped diamond configured to sense one physical parameter or chemical species at any one time. More complex arrangements have involved introducing one or more channels into a piece of boron doped diamond through which a solution can flow for performing electrochemical analysis.
  • the present applicant is unaware of sophisticated diamond based electrochemical sensors which can perform multiple sensing functions at the same time, particularly configured for use in harsh environments. Due to the inherent difficulties involved in manufacturing and forming diamond into multi- structural components, even apparently relatively simple target structures can represent a significant technical challenge.
  • WO2005/012894 describes a microelectrode comprising a diamond layer formed from electrically non-conducting diamond and containing one or more pin-like projections of electrically conducting diamond extending at least partially through the layer of non-conducting diamond and presenting areas of electrically conducting diamond at a front sensing surface.
  • WO2007/107844 describes a microelectrode array comprising a body of diamond material including alternating layers of electrically conducting and electrically nonconducting diamond material and passages extending through the body of diamond material. In use, fluid flows through the passages and the electrically conducting layers present ring-shaped electrode surfaces within the passages in the body of diamond material.
  • WO2012/126802 describes a diamond based electrochemical band sensor comprising a plurality of boron doped diamond band electrodes disposed within a diamond body. Each boron doped diamond electrode has a length / width ratio of at least 10 at a front sensing surface of the sensor. It is described that it is advantageous from a functional perspective for certain sensing applications to provide band electrodes which have a high aspect ratio at the sensing surface such that a length of a band electrode across the sensing surface is very much larger than a width of the band electrode. WO2012/126802 also suggested that a larger number of electrodes can be provided within the diamond body to support a range of sensing capabilities.
  • a plurality of boron doped diamond band electrodes may be configured to sense one or more of the following properties of a solution adjacent the sensing surface: pH; conductivity; temperature; individual or total heavy metal concentration; and H 2 S.
  • the plurality of boron doped diamond band electrodes may be grouped into sets, each set comprising one or more boron doped diamond band electrodes, wherein each set is configured to sense a different parameter.
  • WO2012/126802 suggests that one of the bands may be configured to generate a proton gradient which flows over one or more of the other bands. This may be used to promote reactions which require a certain pH.
  • a diamond electrode material is advantageous in that a very high electrode potential can be applied to alter pH via proton or hydroxide generation.
  • digests are normally performed to free them so they are available for subsequent reduction.
  • One way to do this is to generate very strong acid (or base) conditions electrochemically.
  • generating very strong acid (or base) conditions can also be useful for cleaning the electrode.
  • WO2012/156203 also suggests that a diamond electrode material is advantageous in that a very high electrode potential can be applied to alter pH via proton or hydroxide generation.
  • WO2012/156203 specifically relates to an electrochemical sensor comprising a diamond reference electrode in addition to a diamond sensing electrode, i.e. a robust all-diamond sensor structure. Since the diamond reference electrode is not a standard reference electrode which is independent of solution type, an in-situ calibration system is provided for assigning peaks in voltammetry data to chemical species thereby allowing the type and concentration of chemical species in the solution to be determined.
  • Several different calibration systems are described including a system in which a calibration electrode is configured to change pH conditions in the solution by generating protons or hydroxide ions to promote a reaction over the diamond reference electrode to tune the reference electrode towards a known potential.
  • WO2012/156307 also suggests that a diamond electrode material is advantageous in that a very high electrode potential can be applied to alter pH via proton or hydroxide generation.
  • WO2012/156307 specifically relates to a combined electrochemical and spectroscopic methodology where a diamond electrode is used to electro-deposit a target species and then a spectroscopic analysis technique is applied to the electro- deposited chemical species. It is indicated that an in-situ pH change can improve the electro-deposition step and thus improve the sensitivity of the combined electro- deposition and spectroscopy analysis technique. Furthermore, it is suggested that an in-situ pH change can be used to aid cleaning of the diamond electro-deposition electrode.
  • a diamond electrochemical sensor comprising:
  • sensing electrode formed of boron-doped diamond material
  • a pH changing electrode formed of boron-doped diamond material
  • sensing electrode and the pH changing electrode are configured such that when placed in an aqueous solution of pH 7, the pH changing electrode can generate H + and OH " allowing a reversible pH change over the sensing electrode across a pH range of at least 3 to 9, more preferably at least 2 to 10, and most preferably at least 1 to 11.
  • a method of detecting a target chemical species in a solution using a diamond electrochemical sensor as defined above comprising: applying a first potential to the pH changing electrode to generating a local pH change over the sensing electrode;
  • a third potential to the sensing electrode to condition the sensing electrode prior to application of the second potential, wherein the third potential has an opposite polarity to the second potential and is larger in magnitude than said second potential.
  • Figure 1 shows stripping peaks from cyclic voltammograms (CVs) conducted on a boron doped diamond (BDD) ring disc electrode at 0.1 vs -1 in 1 mM Hg(N0 3 ) solutions at pH 2, pH 5 and pH 7 (inset shows the full CV for the pH 2 solution);
  • CVs cyclic voltammograms
  • BDD boron doped diamond
  • Figure 2(a) shows an optical microscope image of the ring disc electrode surface
  • Figure 2(b) shows a typical Open Circuit Potential (OCP) vs. pH calibration curve for an iridium oxide coated BDD disc (inset shows the behaviour of the iridium oxide film on a polycrystalline boron doped diamond (pBDD) disc in 1 M H 2 SO 4 );
  • OCP Open Circuit Potential
  • Figure 2(c) shows a radial slice of a model of the proton flux from the ring to the disc at 600s;
  • Figure 3 shows mercury stripping peaks at 0.1 Vs "1 in ImM Hg(N0 3 ) solutions;
  • Figure 4 summarizes in situ mercury detection using a ring disc electrode configuration;
  • Figure 5 shows characterisation of a ring disc electrode, CVs in Ru(NH 3 ) 6 2+/3+ for the disc (left) and ring (right) at a range of scan rates;
  • Figure 6(a) shows a schematic diagram of the simulation domain; an axisymmetric section of a water cylinder on top of a ring-disc electrode arrangement defined by points wi_3 and lengths h and WT;
  • Figure 6(b) shows an example of a radial slice of the [H + ] at 60 seconds for a i gen of 50 ⁇ (the electrode geometry is superimposed for clarity);
  • Figure 7(a) shows an FE-SEM (Field Emission - Scanning Electron Microscopy) image of an all-diamond dual band electrochemical sensor
  • Figure 7(b) shows a schematic illustration of the all-diamond dual band electrochemical sensor
  • Figure 7(c) shows the potentials applied and timescale of the cleaning step (-4 ⁇ pulse cleaning for 20 s) as well as the sensing step that follows at +1.2 V together with the basic pH generating electrode potential (can vary for -1.7 V to -2 V);
  • Figure 9(b) shows a plot summarising all the FIA-EC data as an average peak height versus electrode treatments and in-situ pH generation - the effect of a freshly cleaned electrodes can be clearly seen with a -30% increase in signal and a better signal reproducibility noted by the size of the error bars; a 25% increase in the signal was achieved at x g applied potential of -1.7 V and a further -20% increase when the x g applied a potential of -1.8 V;
  • Figure 9(c) illustrates the processes occurring at solution/electrode interfaces for solution containing dissolved hydrogen sulphide using the sensor technology as described herein;
  • Figure 9(d) shows a plot of the ratio of dissolved hydrogen sulphide vs. solution pH showing the relative amounts of each of the three soluble forms of sulphide at a given pH;
  • Figure 10(a) illustrates the application of increasing cathodic potentials applied at the upstream generator electrode for 60 s using a potent io static technique
  • Figure 10(b) illustrates the pH measured simultaneously on the downstream electrode
  • Figure 11(a) shows a series of 60 s constant current pulses applied to the upstream electrode using a galvanostatic technique
  • FIG. 11(b) shows the downstream pH electrode recording the local flux of Ff70H " downstream.
  • embodiments of this invention provide a diamond electrochemical sensor comprising: a sensing electrode formed of boron-doped diamond material; and
  • a pH changing electrode formed of boron-doped diamond material
  • sensing electrode and the pH changing electrode are configured such that when placed in an aqueous solution of pH 7, the pH changing electrode can generate H + and OH " allowing a reversible pH change over the sensing electrode across a pH range of at least 3 to 9, more preferably at least 2 to 10, and most preferably at least 1 to 11.
  • Such a broad and reversible pH change generated over a diamond sensing electrode in situ by an adjacent diamond electrode has been found to enable electrochemical sensing of important environmental target species such mercury and sulphur to extreme levels of sensitivity.
  • the senor is configured to generate the reversible pH change without any substantial gas bubble formation at the surface of the pH changing electrode.
  • Gas bubbles tend to form when electrodes are driven to the extreme potentials needed for large in situ pH changes and these gas bubbles interfere with electrochemical sensing measurements.
  • the present inventors have found that by careful selection of the boron-doped diamond material used for the pH changing electrode then gas bubble formation can be effectively eliminated.
  • the sensing electrode and the pH changing electrode can be formed of a boron-doped diamond material which has an sp2 carbon content sufficiently low as to not exhibit non-diamond carbon peaks in a Raman spectrum of the boron-doped diamond material.
  • Such high phase purity boron doped diamond material is capable of being driven to the extreme potentials required for generating large in situ pH changes without any substantial gas bubble formation. Accordingly, a pH change can be generated and maintained during an electrochemical sensing measurement without gas bubble formation interfering with the electrochemical sensing measurement.
  • a target pH can be generated over the sensing electrode by the pH changing electrode and held during electrochemical sensing of a target species using the sensing electrode.
  • the reversible pH change can be generated over extended time periods (e.g. at least 10 seconds, 30 seconds, 1 minute, 5 minutes, or 10 minutes) and/or multiple cycles without surface passivation of the pH changing electrode.
  • This allows a range of electrochemical sensing measurements to be performed while generating and maintaining a target pH value over the diamond sensing electrode and for such measurements to be repeatedly performed in a reliable and reproducible manner.
  • the use of high phase purity boron doped diamond electrodes is advantageous for achieving this functionality.
  • an oxygen-terminated synthetic diamond material which can be achieved by acid washing and then polishing the surface of the synthetic diamond material with alumina micro polish.
  • the boron-doped diamond sensing electrode and the boron-doped diamond pH changing electrode are both mounted within an intrinsic diamond support matrix.
  • This "all-diamond" solution is advantageous in terms of mechanical and chemical robustness and is also advantageous in terms of ability to clean and re-use without causing damage and without contamination of subsequent electrochemical measurements.
  • the sensing electrode is a disc electrode and the pH changing electrode is a ring electrode which surrounds the disc electrode. While such ring and disc electrode configurations are known, the large, stable, and reproducible pH changes as described herein can be achieved by combining this electrode configuration with the selection of phase-pure boron doped diamond electrode material, a suitable treatment to provide a stable surface termination, and a suitable electric contact to provide a good ohmic connection.
  • the sensing electrode can be a band electrode and the pH changing electrode is another band electrode positioned adjacent the sensing electrode.
  • the pH changing electrode should ideally have a larger surface area than the sensing electrode to provide large and stable pH changes over the sensing electrode as described herein.
  • such a configuration in which the pH changing electrode has a larger surface area than the sensing electrode is advantageous for other electrode configurations, such as the ring and disc configuration described previously, in order to ensure that a sufficiently large and consistent pH change is generated over the sensing electrode.
  • an outer peripheral edge of the pH changing electrode defines a larger area than the outer peripheral edge of the sensing electrode.
  • suitable electrode configurations may be combined with the use of phase-pure boron doped diamond electrode material, a suitable treatment to provide a stable surface termination, and a suitable electric contact to provide a good ohmic connection in order to achieve the large, stable, and reproducible pH changes over a sensing electrode as described herein.
  • the electrode configurations as described above may be disposed in a static electrochemical cell.
  • the sensing electrode and the pH changing electrode can be disposed in a flow cell with at least a portion of the pH changing electrode being disposed upstream of the sensing electrode whereby H + and OFT generated by the pH changing electrode flow over the sensing electrode in use.
  • the precise electrochemical cell configuration will depend on the end application.
  • the pH changing electrode can be configured to generate the reversible pH change using a galvanostatic generation methodology rather than a potentio static approach. It has been found that the galvanostatic generation methodology can result in more stable and reproducible pH responses when compared to the potentiostatic approach
  • the diamond electrochemical sensor can also be configured to apply a cleaning pulse to the sensing electrode to condition the sensing electrode prior to detection of a target species.
  • the diamond electrochemical sensor may be configured to apply the following pulses to the sensing electrode and the pH changing electrode: a cleaning pulse applied to the sensing electrode;
  • another aspect of the invention is a method of detecting a target chemical species in a solution using a diamond electrochemical sensor according to any preceding claim, the method comprising:
  • a third potential is applied to the sensing electrode to condition the sensing electrode prior to application of the second potential, wherein the third potential has an opposite polarity to the second potential and is larger in magnitude than said second potential.
  • the diamond electrochemical sensor can be configured such that a mercury stripping peak of at least 10 ⁇ is generated at the sensing electrode using a scan rate of 0.1 Vs "1 in a 1 mM Hg 2 2+ solution which has an intrinsic pH of 7 (i.e. a pH of 7 prior to application of an in situ pH change via the pH changing electrode).
  • H 2 S detection is most sensitive at high pH and embodiments of the present invention are capable of generating and maintaining a pH of 11 for detecting H 2 S.
  • the diamond electrochemical sensor can be configured such that a limit of detection for dissolved hydrogen sulphide is lower than 100 ppb, 50 ppb, 20 ppb, or 10 ppb in a solution having an intrinsic pH of between 6 and 7 (i.e. a pH between 6 and 7 prior to application of an in situ pH change via the pH changing electrode).
  • a limit of detection for dissolved hydrogen sulphide is lower than 100 ppb, 50 ppb, 20 ppb, or 10 ppb in a solution having an intrinsic pH of between 6 and 7 (i.e. a pH between 6 and 7 prior to application of an in situ pH change via the pH changing electrode).
  • Such functionality can be achieved through the selection of a suitable electrode geometry, diamond material quality, system configuration, and electrode driving methodology.
  • the senor may be calibrated using bulk pH buffered solutions over the working range of the sensor and an electrochemical system with a known response to pH changes, e.g. an iridium oxide film.
  • the sensor may be configured in the same manner as a sensor calibrated in such a manner. In either case, local pH changes over the sensing electrode are calibrated, directly or indirectly, versus an electrochemical response of an electrochemical system in bulk pH buffered solutions over a working pH range of the sensor.
  • the solvent window extends over a potential range of at least 4.1 V wherein end points of the potential range for the solvent window are defined when anodic and cathodic current density measured at the boron doped synthetic diamond material reaches 38 mA cm "2 ; and the solvent window extends over a potential range of at least 3.3 V wherein end points of the potential range for the solvent window are defined when anodic and cathodic current density measured at the boron doped synthetic diamond material reaches 0.4 mA cm "2 ;
  • a peak-to-peak separation ⁇ ⁇ for a macroelectrode
  • a quartile potential ⁇ 3 /4_ ⁇ / 4 for a microelectrode
  • Such synthetic diamond materials include both polycrystalline (pBDD) and single crystal (scBDD) boron doped synthetic diamond materials which have been optimized for their electrochemical sensing performance.
  • pBDD polycrystalline
  • scBDD single crystal
  • Such materials are ideal for implementing examples of the present invention as the boron-doped diamond materials can be driven to extreme potentials to change the in situ pH of a solution without substantial gas bubble formation and without causing adverse electrochemical reactions which interfere with an electrochemical sensing measurement.
  • a low boron dopant content can aid in providing a large solvent window, flat electrochemical response, and low capacitance as desired.
  • sp2 carbon content within the boron doped diamond material is undesirable as this also tends to shrink the solvent window, increase capacitance, and increase non-uniformities in the electrochemical response of the electrode material. If the boron dopant content becomes too high then it is more difficult to control the presence of non-diamond carbon, e.g. sp2 carbon, providing an additive detrimental effect on the performance of the electrode material in terms of providing a wide, flat baseline for species detection.
  • the present inventors have developed polycrystalline CVD synthetic diamond materials and single crystal CVD diamond materials which have optimized boron concentrations and substantially no sp2 carbon (as detectable via Raman spectroscopy).
  • the boron doped synthetic diamond materials have been defined above in terms of their functional electrochemical properties as this is the most convenient, clear, and concise way to characterize the materials. In practice, the present inventors have fabricated a number of different types of boron doped synthetic diamond materials which fulfill these functional electrochemical properties. The materials may be categorized into three main types:
  • bulk boron doped single crystal synthetic diamond materials which comprise a suitable boron dopant content and crystallographic quality to achieve the previously described functional electrochemical properties throughout a majority volume of the single crystal synthetic diamond materials;
  • capped boron doped single crystal synthetic diamond materials which comprise a capping layer having a suitable boron dopant content and crystallographic quality to achieve the previously described functional electrochemical properties and a support layer having a lower boron content;
  • boron doped polycrystalline synthetic diamond materials which comprise a plurality of boron doped synthetic diamond grains with a sufficient portion of the grains at an exposed surface of the material having a suitable boron dopant content, while maintaining phase purity (i.e. substantially no sp2 carbon content), to achieve the previously described functional electrochemical properties.
  • a boron doped synthetic diamond material in which at least a portion of an exposed surface layer comprises boron doped synthetic diamond material having a boron content in a range 1 x 10 20 boron atoms cm “3 to 7 x 10 21 boron atoms cm “3 .
  • at least 50%, 70%, 90%>, or 95% of the exposed surface layer comprises boron doped synthetic diamond material having a boron content in a range
  • boron doped synthetic diamond material can be fabricated with a boron content over 1 x 10 22 boron atoms cm “3 .
  • boron content can provide a low ⁇ ⁇ it possesses a relatively high capacitance (e.g. greater than 10 ⁇ cm "2 ).
  • the sp2 carbon content and crystallographic defects tend to increase which also detrimentally increases the capacitance of the material in addition to lowering the solvent window. Accordingly, it has been found that a suitable upper limit for boron concentration is 7 x 10 21 boron atoms cm "3 when taking all these factors into account.
  • Non-diamond carbon peaks include: 1580 cm "1 - graphite; 1350-1580 cm "1 - nanocrysallite graphite; and 1550 - 1500 cm "1 - amorphous carbon and graphitic phases. It has been found that if sp2 carbon is evident in a Raman spectrum of a material then the material will have a smaller solvent window, a higher capacitance, and surface oxidation/reduction features.
  • the sp2 carbon content is sufficiently low as to not exhibit non-diamond carbon peaks in a Raman spectrum of the material.
  • An sp2 carbon signature in Raman spectra has been correlated with higher capacitance, non-Faradaic surface processes, and a reduced solvent window.
  • Micro-Raman spectroscopy can be performed at room temperature with a Renishaw inVia Raman microscope using an excitation wavelength of 514.5 nm, an Ar + laser with a power of 10 mW, and a CCD detector.
  • Magnification for Raman spectroscopy can be x5, xlO, x20, x50 and xlOO objectives at visible and near infrared (NIR) frequencies and x5 and x20 at ultraviolet (UV) frequencies.
  • NIR visible and near infrared
  • UV ultraviolet
  • x50 magnification the xy-spot size (and hence resolution) is approximately 5x5 microns and with xlOO the xy-spot size is approximately 2x2 microns.
  • Typical values for magnification objectives in air thus range from x5 to xlOO.
  • an exposed surface of the single crystal boron doped synthetic diamond material may comprise no more than 5%, 3%, 1%, 0.5%, or 0.3% by area of crystallographic defects observable by visible microscopy at a magnification of up to xlOO.
  • a microwave plasma activated CVD diamond synthesis system typically comprises a plasma reactor vessel coupled both to a supply of source gases and to a microwave power source.
  • the plasma reactor vessel is configured to form a resonance cavity supporting a standing microwave, typical frequencies used for this heating application include 2.45 GHz and approximately 900 MHz depending on the RF spectrum allocation of each country.
  • Source gases including a carbon source and molecular hydrogen are fed into the plasma reactor vessel and can be activated by the standing microwave to form a plasma in high field regions.
  • a suitable substrate is provided in close proximity to the plasma, reactive carbon containing radicals can diffuse from the plasma to the substrate and be deposited thereon. Atomic hydrogen can also diffuse from the plasma to the substrate and selectively etch off non-diamond carbon from the substrate such that diamond growth can occur.
  • a source of boron such as diborane gas is introduced into the synthesis atmosphere then boron doped synthetic diamond material can be grown. Single crystal synthetic diamond materials are typically fabricated via homoepitaxial growth on single crystal diamond substrates. In contrast, polycrystalline synthetic diamond wafers can be grown on silicon or refractory metal substrates.
  • Important growth parameters include the microwave power density introduced into the plasma chamber (typically ranging from less than or equal to 1 kW to 5 kW or more for a substrate area ⁇ 20 cm 2 ), the pressure within the plasma chamber (typically ranging from less than or equal to 50 Torr (i.e. 6.67 kPa) to 350 Torr (i.e.
  • the gas flow velocity flowing through the plasma chamber typically ranging from a few 10s of seem (standard cm 3 per minute) up to hundreds or even thousands of seem
  • the temperature of the substrate typically ranging from 700 to 1200°C
  • the composition of the synthesis atmosphere typically comprising 1 to 20% by volume of carbon containing gas (usually methane) with the remainder of the synthesis atmosphere been made up of hydrogen.
  • the synthesis atmosphere will typically comprise a boron containing gas such as diborane at a concentration from equal to or less than 0.01% up to several % by volume.
  • the problem to be solved is what growth parameters to select in order to fabricate synthetic boron doped diamond materials with optimized electrochemical sensing properties. Suitable growth parameters for both single crystal and polycrystalline diamond materials are discussed below.
  • a boron dopant concentration in a range 1 x 10 20 boron atoms cm “3 to 7 x 10 21 boron atoms cm “3 has been found to be desirable to achieve high performance synthetic diamond material for electrochemical sensing applications.
  • electrochemical performance of single crystal boron doped diamond materials can be affected by the presence of crystallographic defect features which are observable by visible microscopy at a magnification of up to xlOO. It has been found that growing single crystal CVD synthetic diamond material at higher power and pressure (e.g. 250 Torr (i.e.
  • the pressure is controlled to lie in a range 120 Torr to 160 Torr (i.e. 16.00 kPa to 21.33 kPa), more preferably in a range 130 Torr to 150 Torr (i.e. 17.33 kPa to 20.00 kPa), and most preferably around 140 Torr (i.e. 18.67 kPa).
  • the power is controlled to lie in a range 3.1 kW to 3.9kW, more preferably in a range 3.3 kW to 3.8kW, and most preferably around 3.6 kW.
  • the temperature of the substrate may be controlled to lie in a range 750°C to 850°C.
  • boron incorporation has been found to be increased by manipulating the gas flow firstly by using a reactor configured with a co-axial gas injection system, for example comprising a nozzle positioned between 50 mm and 180 mm above the substrate to direct gas towards the substrate, and secondly by increasing the gas velocity via a combination of the total gas flow rate and the chamber gas injection nozzle diameter.
  • a reactor configured with a co-axial gas injection system, for example comprising a nozzle positioned between 50 mm and 180 mm above the substrate to direct gas towards the substrate, and secondly by increasing the gas velocity via a combination of the total gas flow rate and the chamber gas injection nozzle diameter.
  • the total gas flow rate may be at least 500 seem, more preferably at least 600 seem, and most preferably over 650 seem.
  • a hydrogen gas flow of between 500 and 700 seem may be utilized with a methane gas flow of between 25 and 40 seem and a diborane gas flow between 15 and 30 seem.
  • Argon gas may also be introduced into the synthesis atmosphere, for example at a flow rate in a range 20 to 30 seem.
  • the present invention will now be illustrated by way of two different examples: (i) in situ control of local pH using a boron doped diamond ring disc electrode configuration for detecting extremely low concentrations of mercury; and (ii) in situ control of local pH using boron doped diamond band electrodes in a channel flow system for detecting extremely low concentrations of hydrogen sulphide.
  • H ions, and therefore pH play a major role in promoting many different reactions, often by acting as a catalyst [Brett, A. M. O.Ghica, M.-E. Electroanalysis, 2003, 15, 1745-1750] or by simply retarding competing side reactions [Nematollahi, D.Golabi, S. M. Electroanalysis, 2001, 13, 1008-1015].
  • One particularly important area of research is the use of electroanalysis for heavy metal detection via electrodeposition and subsequent stripping [Zeng, A. ;Liu, E. ;Tan, S. N. ;Zhang, S.Gao, J. Electroanalysis, 2002, 14, 1294-1298].
  • GC electrodes come in various geometries, including dual bands [Fosset, B.; Amatore, C; Bartelt, J.; Wightman, R. M. Anal. Chem., 1991, 63, 1403-1408 and Fosset, B.; Amatore, C. A.; Bartelt, J. E.; Michael, A. C; Wightman, R. M. Anal. Chem., 1991, 63, 306-314], ring discs [Liljeroth, P.; Johans, C; Slevin, C.
  • GC electrodes can also offer high sensitivity, enabling trace level detection [Aoki, K. ;Morita, M. ;Niwa, O.Tabei, H. J. Electroanal Cham, 1988, 256, 269-282].
  • Hg Mercury
  • BDD boron-doped diamond
  • Hg electroanalysis is carried out under acidic conditions [Kumar Jena, B., Retna Raj, C. Anal. Chem., 2008, 80, 4836-4844 and Manivannan, A., Seehra, M. S., Tryk, D. A., Fujishima, A. Anal. Lett., 2002, 35, 355-368], in order to improve the voltammetric stripping response.
  • this prevents the use of electrodes directly at the source e.g. river and sea water.
  • a ring disc BDD electrode it is possible to optimise detection sensitivity for Hg 2 2+ in solutions where the bulk pH is close to neutral.
  • Hg solutions were prepared from Hg(N0 3 ) 2 H 2 0 (Merck), and pH adjusted where necessary with 1 M HNO 3 (70%, Fisher Chemical) and 1 M KOH (Fisher Chemical).
  • the iridium oxide solution used was prepared as described in the literature [Yamanaka, K. Jpn. J. App. Phys., 1989, 623 and Yamanaka, K. Jpn. J. App. Phys., 1991, 1285]; 4.45 mM iridium tetrachloride, 1 mL H 2 0 2 (30% w/w) and 39 mM oxalic acid dihydrate were added sequentially to 100 mL water and stirred for 30 min, 10 min, and 10 min intervals respectively. Anhydrous potassium carbonate was added until a pH of 10.5 was achieved resulting in a pale yellow-green solution. This was stirred for 48 h until the solution had stabilized and appeared blue in colour. The iridium oxide solution was refrigerated between uses
  • BDD electrode fabrication High quality (substantially sp2 free) conducting polycrystalline BDD [Patten, H. V.; Meadows, K. E.; Hutton, L. A.; Iacobini, J. G.; Battistel, D.; McKelvey, K.; Colburn, A. W.; Newton, M. E.; Macpherson, J. V.; Unwin, P. R. Angew. Chem., Int.
  • Ti/Au electrical contacts 10 nm and 200 nm thick respectively were sputtered onto the back of the disk and annealed at 500 °C for 4 h, whilst the backside of the ring was graphitized using the laser, which provides a convenient and sufficient ohmic contact [Geis, M.; Rothschild, M.; Kunz, R.; Aggarwal, R.; Wall, K.; Parker, C; Mcintosh, K.; Efremow, N.; Zayhowski, J.Ehrlich, D. Applied physics letters, 1989, 55, 2295-2297].
  • the pBDD ring was placed as centrally as possible around the pBDD column, in a Teflon mould and sealed in place with a thin layer of epoxy resin (Robnor Resins). Copper wires were connected via conductive silver epoxy (Circuitworks, ITW Chemtronics) to the Ti/Au contact on the disc and the graphitised region of the ring. Once the epoxy had set the electrodes were removed from the mould and polished back with silicon carbide pads (Buehler) of decreasing roughness until the surface of the ring disc was exposed. Finally an alumina polish (0.05 ⁇ micropolish Buehler) was applied to provide an optimum electrode surface.
  • alumina polish 0.05 ⁇ micropolish Buehler
  • macro electrodes were prepared from 1 mm diameter laser micromachined pBDD columns sealed in glass capillaries [Hutton, L. A.; Newton, M. E.; Unwin, P. R.; Macpherson, J. V. Anal. Chem., 2008, 81, 1023-1032].
  • a pH sensitive iridium oxide film was employed.
  • the film was electrodeposited on the pBDD disc using a three electrode system with a non-leak Ag
  • Deposition was carried out using a potentiostat (CHI730A, CH Instruments Inc.) connected to a desktop computer; a potential of 0.7 V was applied for a total of 900 s.
  • Cyclic voltammograms (CV) were run in iridium oxide solution and H 2 SO 4 before and after deposition to confirm film formation and elucidate deposition potential.
  • the pH response of the film is reliant on hydration [Bitziou, E.; O'Hare, D.; Patel, B. A. Anal. Chem., 2008, 80, 8733-8740], so electrodes were stored in pH 7 phosphate buffer solution and left to hydrate for two days before use.
  • the film's response to pH was characterised via calibration in known pH buffer solutions using a two electrode system.
  • the open circuit potential (OCP) was measured for 30 s in each buffer in order of decreasing acidity; this was reversed then repeated to obtain at least 3 measurements at each pH.
  • H + generation experiments on the ring electrode were conducted using an IVIUM bipotentiostat with a Peripheral Differential Amplifier (PDA) attachment which allows the simultaneous recording of the potential at the disc electrode.
  • PDA Peripheral Differential Amplifier
  • the generating current was applied using a Keithley Source Meter.
  • Comsol modelling A model of proton generation and diffusion was created using COMSOL Multiphysics 4.3a (COMSOL, SE) finite element analysis (FEA) software, as described later.
  • Figure 1 shows a comparison of the Hg stripping peaks recorded at a 1 mm diameter BDD disc electrode with the solution adjusted to differing pH values of 2, 5 and 7.
  • the solution contained 1 mM 3 ⁇ 4( ⁇ 0 3 ) 2 ⁇ 2 0 and the data shows only the oxidative part of the CV.
  • Full CVs were recorded at a scan rate of 0.1 V s "1 , as shown in Figure 1 inset, for a pH 2 solution, where Hg can be seen to electrodeposit on the electrode at around ⁇ 0 V versus Ag
  • E° describes the OCP at pH 0, which is dependent on film thickness [Terashima, C; Rao, T. N.; Sarada, B. V.; Spataru, N.Fujishima, A. J. Electroanal.
  • the OCP, and hence pH, at the iridium oxide modified disc was measured for different applied ring currents in the range 0 - 50 ⁇ (gal vano static) over 600 s, as shown in Figure 2(d) (solid lines), alongside the Finite Element Model (FEM) simulated data (dashed lines). This time period was employed to ensure local pH generation remained stable throughout typical electrodeposition times employed during heavy metal analysis. The data clearly shows that upon application of a positive current at the ring the measured pH on the disc decreases on a timescale of typically 120 - 60 s (10 - 50 ⁇ ), before reaching an approximate steady state plateau. This reflects the time taken for protons to transit from the ring and flood the disc, and also the response time of the iridium oxide film.
  • FEM Finite Element Model
  • the data shows clearly that for a ring disc electrode of the dimensions reported herein, it is possible to locally modify the proton concentration in the vicinity of the disc by up to five orders of magnitude, from pH 6.4 to pH 2 (at the highest applied current). Under these conditions the electrode is being driven at a high potential for very long periods of time, which for commonly used noble metal electrodes (Pt, Au) would cause the formation of metal oxides and passivate the surface. Due to its intrinsically inert nature, BDD provides a reproducible flux of protons over long time scales without the need for electrode activation [Chaston, J. C. Platinum Met. Rev., 1964, 8, 141-142]. The lower pH value generated is sufficient to produce the efficient electrodeposition and stripping seen in acidic bulk solution.
  • FIG. 4 summarizes the work described above.
  • Proton generation through the decomposition of water on the ring of a ring disc electrode allowed pH to be controlled locally at the electrode surface; this enables experiments to be conducted at the optimum pH for the analyte, without needing to manually acidify the solution.
  • the generated pH was found to remain stable over time after an initial equilibration period and showed good agreement with simulated data.
  • In situ Hg detection with no need for sample pre-treatment was made possible using a pBDD ring-disc electrode. It has been shown that using this method a localised pH can be generated in situ, eliminating the need to remove a sample from its source for analysis, the pH generated remains sufficiently stable long enough for analytical experiments to be conducted on the disc electrode.
  • a move to all diamond devices would improve the lifetime and durability of the electrodes, allowing them to be used in even the harshest environments without suffering corrosion or degradation. It would also improve the reproducibility of the fabrication procedure, ensuring co-planar electrodes and a centrally aligned disc. Use of this method in a flow system would both allow for detection of much lower analyte concentrations, and shorten the time required for electrodeposition and thus overall analysis.
  • Figure 5 shows characteristic CVs for a disc and ring electrode (left and right respectively) in 1 mM Ru(NH 3 ) 6 2+/3+ (0.1 M KN0 3 ) over the scan rate range 20 mVs "1 to 500 mVs "1 .
  • the peak to peak separations of both CVs are approximately 70 mV at 100 mVs "1 , showing close to reversible diffusion controlled behaviour for both the ring and the disc BDD electrodes.
  • FEM finite element model
  • the model was created using COMSOL Multiphysics 4.3a (COMSOL AB, Sweden) finite element analysis (FEA) software.
  • the model consisted of a 2D axisymmetric section, with coordinates r and z corresponding to a water cylinder on top of a ring disc arrangement of electrodes in an inert surface.
  • Figure 6 shows a schematic of the simulated domain.
  • the ring and disc were defined by subdividing this boundary into sub-boundaries la, lb and lc.
  • Boundary lb was defined as the remaining part of boundary 1.
  • the size of the box is chosen such that the diffusion of the generated protons does not reach the edge in the time scale of the simulation, la corresponds to the Iridium Oxide coated detector disc electrode and is functionally inert (ie no flux), lb corresponds to the material that the ring and disc are mounted in and is also functionally inert (ie no flux), lc corresponds to the generator ring electrode and an inward flux is defined across this electrode corresponding to the generation of protons by electrolysis of water. The flux is assumed to be proportional to the current passed through the electrode: l c A.F
  • n is the unit normal vector, is the total inward flux across boundary lc, i gen is the total current through the electrode, A is the area of the electrode and F is Faraday's constant.
  • Boundaries 3 and 4 were defined as having a fixed proton concentration of 10 "6'4 M, while boundary 2 was defined by an axisymmetric constraint.
  • the diffusion coefficient of the protons (D p ) was set to 9.31xl0 "9 m 2 s "1 and the initial concentration of protons c p was set to 10 "6'4 M, corresponding to the apparent starting pH of the experimental medium. Diffusion of protons from the generator electrode was modelled according to Fick's Second Law:
  • R p is the total inward flux of protons into the system. Migration due to electric field and natural convection were not considered.
  • a mesh was generated where a density of 500 elements per mm were specified for sub-boundaries la, lb and lc; corresponding to an element length of 2 ⁇ on these boundaries. The rest of the area was meshed using an advancing front to a maximum element size of 0.5 mm. The total mesh consisted of 461389 elements. The simulation was solved in a time-dependant manner for a total of 600 seconds using the PARDISO solver as implemented in COMSOL.
  • Table 1 Summary of boundary conditions used for the simulation of the pH during the ring generation experiment.
  • n represents the unit normal vector and N lc represents the total inward flux across the boundary lc, c represents the concentration of the electroactive species in the bulk solution.
  • the set of points wi, W2 and W3 were chosen to reflect the size of the experimental ring-disc system and were set to 0.46125 mm, 0.72225 mm and 0.87225 mm respectively.
  • Polycrystalline boron doped diamond is a robust electrode material that is known to possess an ultra-wide solvent window in aqueous media, low capacitive currents, and high resistance to fouling and corrosion processes. Most of the above attributes depend on the quality of the diamond electrode (sp 2 -sp 3 ratio) and its termination. In this invention we are using a high quality pBDD band structure overgrown on an intrinsic polycrystalline substrate with the aim to detect the dissociated sulphide in solution and optimise the electrode response.
  • the HS " ion can be oxidised at an electrode at relatively low overpotentials according to the following reaction,
  • This embodiment is based upon the fact that a second electrode can cause a shift in the local pH of the analysed solution in order to achieve an equilibrium shift towards a more favourable species to aid detection.
  • Laminar flow transports the pH gradient over the sensing electrode in a continuous manner therefore maintaining a relatively constant regional pH.
  • Constant potential (potent io static) and constant current (galvanostatic) approaches have been adopted and compared in order to recognize the best experimental approach.
  • Electrodes In this study a dual electrode pBDD band structure was employed for the detection of sulphide at different pH values.
  • the two BDD bands were fabricated by laser micromaching an intrinsic optically transparent diamond substrate to form two recessed band structures. Then pBDD was overgrown on top of the structures under controlled conditions using chemical vapour deposition (CVD) and the resulting composite was lapped flat to expose the conducting bands that formed the two electrode bands.
  • the latter electrode was used to oxidise the sulphide while the larger electrode was held a constant (-)ve potential or (-)ve current to induce the desirable pH shift.
  • the channel flow cell used herein consisted of a planar surface that contained the pBDD band structure and a one piece flow unit that was positioned on top (Fig. 7b).
  • the flow unit was fabricated using microstereolithography (MSL) and was especially designed to use for flow injection analysis (FIA) [Sansuk, S.; Bitziou, E.; Joseph, M. B.; Covington, J. A.; Boutelle, M. G.; Unwin, P. R.; Macpherson, J. V., Ultrasensitive Detection of Dopamine Using a Carbon Nanotube Network Microf uidic Flow Electrode. Anal. Chem.
  • an iridium oxide film was employed.
  • the film was electrodeposited on the pBDD band while confined in the MSL flow cell and under stationery conditions by applying a potential of 0.7 V (vs. Ag
  • the IrOx- pBDD band electrode was calibrated using different pH solutions by recording the open circuit potential (OCP) under flow condition (1 mL min "1 ) mimicking in that way the pH generating conditions.
  • Electrode cleaning Prior to sulphide detection it was necessary to apply a cleaning step to the sensing electrode because of the sulphur deposition that occurs during the oxidation of sulphide (Eq. 3).
  • Figure 7(c) shows the potentials applied and timescale of the cleaning step (-4 ⁇ pulse cleaning for 20 s) as well as the sensing step that follows at +1.2 V together with the basic pH generating electrode potential (can vary for -1.7 V to -2 V). This cleaning process was previously optimised (not shown) and repeated at each injection of the sulphide solution.
  • the mobile phase that was in continuous flow over the electrodes contained 0.1 M KNO3 at pH 3.8 or pH 6.1 or pH 10 (pH adjusted by 0.1 M HN0 3 or 0.1 M NaOH) depending on the experiment.
  • Stock solutions of 2 mM sodium sulphide (Na 2 S) were made in de-aerated solutions of 0.1 M KNO3 at pH 3.8 or pH 6.1 or pH 10.
  • the stock solution was used to make a diluted solution for the flow injection of sulphide.
  • the diluted solutions had the same composition as the mobile phase and stock (degassed 0.1 M KNO 3 with certain pH value) and contained 100 ⁇ sulphide added from the stock (for Figures 9 & 10) or various increasing concentrations (1 - 50 ⁇ H 2 S, Figure 8).
  • Figure 7(a) shows an FE-SEM image of a 90 ⁇ wide pBDD band which is part of the all-diamond device described in the experimental section.
  • the polycrystalline nature of the BDD is visible and a thorough electrochemical characterisation process indicated that the band electrodes are fully insulated by the intrinsic substrate without the presence of holes or defects.
  • the electrode microarray was characterised using microscopy, electrochemistry and Raman and showed that the electrode is completely insulated by intrinsic diamond and relates corresponds to high phase purity pBDD from Element Six Limited.
  • the double layer capacitance of the 90 ⁇ and 240 ⁇ bands are 3 ⁇ cm “2 and 5 ⁇ cm “2 , respectively, with very wide and featureless solvent window similar to results obtained for a metallic-like bulk material containing 3 x 10 20 boron atoms cm “3 .
  • Figure 7(c) shows the experimental settings for detection of sulphide for the two pBDD band electrodes.
  • the generator electrode x g is inactive during the x s cleaning step and a constant potential of -1.7 V or -1.8 V or -2.0 V is applied to x g during the sulphide sensing step.
  • the negative potential applied at the x g generates a flux of hydroxyl ions (HO ) that increases the pH of the solution in the vicinity of x g generating a pH gradient. Due to diffusion and convection caused by solution flow the pH at x s electrode is also affected causing the sulphide equilibrium to shift (eq. 1) and therefore increasing the signal we can obtain for the oxidation of the singly protonated HS " ion.
  • HO hydroxyl ions
  • Figure 8(b) shows the calibration graph constructed using the above data by averaging the peak heights vs. concentration of dissolved sulphide.
  • a plot summarising all the FIA-EC data as an average peak height versus electrode treatments and in-situ pH generation is shown in Figure 9(b).
  • Figure 9(d) shows a plot of the ratio of dissolved hydrogen sulphide vs. solution pH according to equations 1 & 2 showing the relative amounts of each of the three soluble forms of sulphide at a given pH.
  • the x s electrode was modified with a pH sensing film of iridium oxide in order to quantitatively measure the local pH in the vicinity of the electrode.
  • Increasing cathodic potentials were applied at the upstream generator electrode for 60 s as shown in figure 10(a) and the pH was measured simultaneously on the downstream electrode ( Figure 10(b)).
  • the upstream electrode was floating at an OCP therefore allowing the pH sensor downstream to equilibrate at the solution pH (pH 6, 0.1 M KNO3) under continuous flow.

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Abstract

L'invention concerne un capteur électrochimique de diamant comprenant : une électrode de détection formée de matière de diamant dopé par du bore; et une électrode de changement du pH formée de matière de diamant dopé par du bore; l'électrode de détection et l'électrode de changement du pH étant configurées de telle sorte que lorsqu'elles sont placées dans une solution aqueuse de pH 7, l'électrode de changement du pH peut générer H+ et OH- selon un changement de pH réversible sur l'électrode de détection sur une plage de pH d'au moins 3 à 9.
PCT/EP2014/063439 2013-07-05 2014-06-25 Capteurs électrochimiques à base de diamant dopé par du bore WO2015000769A1 (fr)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2017027477A1 (fr) * 2015-08-07 2017-02-16 Fraunhofer Usa, Inc. Appareil et procédé pour détecter des métaux à l'état de traces au moyen d'électrodes en diamant électroconductrices
WO2019092531A1 (fr) * 2017-11-09 2019-05-16 International Business Machines Corporation Contrôle du ph pour la détection d'analyte
US11249042B2 (en) * 2017-01-31 2022-02-15 Element Six Technologies Limited Diamond based electrochemical sensors
US20220196588A1 (en) * 2020-12-23 2022-06-23 Hach Company Isolating interferences in alkalinity measurement
CN115087862A (zh) * 2020-02-13 2022-09-20 哈希公司 具有硼掺杂金刚石区的pH电极
US11649182B2 (en) 2017-07-19 2023-05-16 Buckman Laboratories International, Inc. Method of regulating one or more component values in monochloramine production using real-time electrochemical sensing

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109313160B (zh) * 2016-06-23 2021-02-23 哈希公司 用于使用碱度传感器测定含水样品的碱度的方法
US10801990B2 (en) * 2018-04-17 2020-10-13 Hach Company Alkalinity measurement of an aqueous sample

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19842735A1 (de) * 1998-09-18 2000-03-23 Torsten Vos Elektrochemischer Sensor mit direkt elektrisch heizbaren Elektrodenflächen
GB2489106A (en) * 2011-03-18 2012-09-19 Element Six Ltd Diamond based electrochemical sensors
GB2491005A (en) * 2011-05-18 2012-11-21 Element Six Ltd Electrochemical sensor with diamond electrodes

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB201108342D0 (en) * 2011-05-18 2011-06-29 Element Six Ltd Electrochemical sensors
GB201214448D0 (en) * 2012-08-14 2012-09-26 Element Six Ltd Electrochemical deposition and x-ray fluorescence spectroscopy

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE19842735A1 (de) * 1998-09-18 2000-03-23 Torsten Vos Elektrochemischer Sensor mit direkt elektrisch heizbaren Elektrodenflächen
GB2489106A (en) * 2011-03-18 2012-09-19 Element Six Ltd Diamond based electrochemical sensors
GB2491005A (en) * 2011-05-18 2012-11-21 Element Six Ltd Electrochemical sensor with diamond electrodes

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
ABDOLLAH SALIMI ET AL: "Boron doped diamond electrode modified with iridium oxide for amperometic detection of ultra trace amounts of arsenic(iii)", THE ANALYST, vol. 129, no. 1, 5 December 2003 (2003-12-05), pages 9 - 14, XP055122044, ISSN: 0003-2654, DOI: 10.1039/b312285a *
SALIMI A ET AL: "Amperometric detection of ultra trace amounts of Hg(I) at the surface boron doped diamond electrode modified with iridium oxide", TALANTA, ELSEVIER, AMSTERDAM, NL, vol. 68, no. 5, 28 September 2005 (2005-09-28), pages 1610 - 1616, XP025000617, ISSN: 0039-9140, [retrieved on 20060228], DOI: 10.1016/J.TALANTA.2005.08.048 *
TANIA L. READ ET AL: "In Situ Control of Local pH Using a Boron Doped Diamond Ring Disk Electrode: Optimizing Heavy Metal (Mercury) Detection", ANALYTICAL CHEMISTRY, vol. 86, no. 1, 9 December 2013 (2013-12-09), pages 367 - 371, XP055140575, ISSN: 0003-2700, DOI: 10.1021/ac403519p *

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11073494B2 (en) 2015-08-07 2021-07-27 Fraunhofer Usa, Inc. Apparatus and method for detecting trace metals with electrically conductive diamond electrodes
WO2017027477A1 (fr) * 2015-08-07 2017-02-16 Fraunhofer Usa, Inc. Appareil et procédé pour détecter des métaux à l'état de traces au moyen d'électrodes en diamant électroconductrices
US11249042B2 (en) * 2017-01-31 2022-02-15 Element Six Technologies Limited Diamond based electrochemical sensors
US11649182B2 (en) 2017-07-19 2023-05-16 Buckman Laboratories International, Inc. Method of regulating one or more component values in monochloramine production using real-time electrochemical sensing
US11161114B2 (en) 2017-11-09 2021-11-02 International Business Machines Corporation Ph control for analyte detection
GB2582499B (en) * 2017-11-09 2021-08-11 Ibm PH control for analyte detection
GB2582499A (en) * 2017-11-09 2020-09-23 Ibm PH control for analyte detection
US11161115B2 (en) 2017-11-09 2021-11-02 International Business Machines Corporation PH control for analyte detection
US10532356B2 (en) 2017-11-09 2020-01-14 International Business Machines Corporation pH control for analyte detection
WO2019092531A1 (fr) * 2017-11-09 2019-05-16 International Business Machines Corporation Contrôle du ph pour la détection d'analyte
CN115087862A (zh) * 2020-02-13 2022-09-20 哈希公司 具有硼掺杂金刚石区的pH电极
US20220196588A1 (en) * 2020-12-23 2022-06-23 Hach Company Isolating interferences in alkalinity measurement
US11714059B2 (en) * 2020-12-23 2023-08-01 Hach Company Isolating interferences in alkalinity measurement

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