WO2016196702A1 - Electrode - Google Patents

Electrode Download PDF

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Publication number
WO2016196702A1
WO2016196702A1 PCT/US2016/035369 US2016035369W WO2016196702A1 WO 2016196702 A1 WO2016196702 A1 WO 2016196702A1 US 2016035369 W US2016035369 W US 2016035369W WO 2016196702 A1 WO2016196702 A1 WO 2016196702A1
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WO
WIPO (PCT)
Prior art keywords
glass tube
glass
frit
electrode
liquid
Prior art date
Application number
PCT/US2016/035369
Other languages
French (fr)
Inventor
David R. Whitcomb
Original Assignee
Carestream Health, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carestream Health, Inc. filed Critical Carestream Health, Inc.
Publication of WO2016196702A1 publication Critical patent/WO2016196702A1/en

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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
    • G01N27/401—Salt-bridge leaks; Liquid junctions

Definitions

  • Silver may be reduced to silver nanostructures and, under certain circumstances, specifically to silver nanowires. See, e.g., S. E. Skrabalak; Wiley, BJ; Kim, M; Formo, EV; Xia, Y; Nano Letters 2008 8(7) 2077-81, P-Y Silvert et al., J Mater. Chem. 1997 7293-9, and P-Y Silvert et al., J. Mater. Chem. 1996 6 573-7.
  • Ion selective electrodes are known that operate in mainly in aqueous environments, occasionally in organic media, and generally near room temperature. See, e.g., D. T. Sawyer, A. Sobkowiak, J. L. Roberts, Jr.,
  • a novel silver ion selective electrode has been designed to operate under high temperatures and in organic solvents to solve this problem.
  • the ion selective electrode may be used to determine the ion concentration at any point during the reaction, enabling the ability to study the chemical details of the reaction process, but in addition may be used in a feedback loop to control the concentration of ions, or the addition point of other components, during the course of the synthesis reaction in order to affect the final properties of the products.
  • Applicants disclose an ion selective electrode capable of in situ long-term monitoring of silver ion concentration at elevated temperatures and pressures in organic media. Such an electrode is useful for monitoring and controlling silver ion concentration during silver nanowire synthesis.
  • a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the second glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and an interface that continuously connects gases above the liquid in the second glass tube to the gases above the liquid in the reaction vessel for the purpose of equilibrating the pressure above the liquids.
  • the first glass tube of the electrode has an outside diameter of about 4 mm and in some embodiments the first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or, in other embodiments, the first glass frit of the said electrode is fused directly to the glass tube.
  • the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3.
  • the second glass tube of the said electrode has an outside diameter of about 10 mm.
  • the second glass tube and the second glass frit of the said electrode are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or, in some embodiments, the second glass tube and the second glass frit is fused directly to the glass tube.
  • the second glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3
  • the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates
  • the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged.
  • the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates
  • the solution in the second glass tube is a saturated solution of KN0 3 salt in propylene glycol.
  • the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a concentrically connected fire-polished glass tubing adaptor, whereas in some embodiments, a piece of tubing connects the fire-polished end of the second glass tube to the reaction vessel for the purpose of equalizing pressure between the said reaction vessel and the concentrically connected fire-polished glass tubing adaptor of the said electrode.
  • a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and a means for modifying the surface tension of the liquid in the second tube and the inner surface of the second tube.
  • first glass tube of the said electrode has an outside diameter of about 4 mm
  • first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; whereas in some embodiments the first glass tube and the first glass frit is fused directly to the glass tube whereas in yet other embodiments the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3.
  • the second glass tube has an outside diameter of about 10 mm, whereas in other embodiments the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or, in other embodiments, second glass tube and the second glass frit is fused directly to the glass tube.
  • the second glass frit is a VitraPOR frit fabricated from borosilicate glass 3.3, and in some embodiments, the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
  • the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged.
  • the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature and pressure at which the electrode operates, whereas in some embodiments, the solution in the second glass tube is a saturated solution of KN0 3 salt in propylene glycol.
  • the inner surface of the second glass tube comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups or other suitable chemical modifiers used to alter the surface tension between the inner glass surface of the second glass tube and the liquid in the second glass tube.
  • the inner surface of the second tube comprises a nanotextured (super-hydrophobic or super-omniphobic) surface applied to minimize the surface tension between the inner walls of the second s glass tube and the liquid in the second glass tube.
  • a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and a means for modifying the surface tension of the liquid in the second tube and the inner surface of the second tube; and an interface that continuously connects gases above the liquid in the second glass tube to the gases above the liquid in the reaction vessel for the purpose of equilibrating the pressure
  • the said electrode comprises a first glass tube has an outside diameter of about 4 mm, whereas in some embodiments, the first glass tube and the first glass frit of the said electrodes are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or, in some embodiments, first glass tube and the first glass frit of the said electrode is fused directly to the glass tube.
  • the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3.
  • the second glass tube has an outside diameter of about 10 mm.
  • the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or, in some embodiments, the second glass tube and the second glass frit is fused directly to the glass tube.
  • the second glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3.
  • the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
  • the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged.
  • the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the
  • the solution in the second glass tube is a saturated solution of KN0 3 salt in propylene glycol.
  • the inner surface of the second glass tube of the said electrode comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups, or other suitable chemical modifiers to modify the surface tension between the inner glass surface of the second glass tube and the liquid comprised in the second glass tube, whereas in some embodiments, the inner surface of the second tube comprises at least one nanotextured (super- hydrophobic or super-omniphobic) surface applied to minimize the surface tension between the inner walls of the second glass tube and the liquid in the second glass tube.
  • the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a concentrically connected fire-polished glass tubing adaptor, and in some embodiments a piece of tubing connects the fire-polished end of the second glass tube to the reaction vessel for the purpose of equalizing pressure between the said reaction vessel and the concentrically connected fire-polished glass tubing adaptor.
  • a double junction reference electrode comprising a first glass tube capped by a first frit and having a first base opposite the first frit; an electrically conductive first liquid within the first glass tube defining a first vapor headspace between the first liquid and the first frit; a silver chloride silver wire passing through the first base and defining a first portion of the silver chloride silver wire being external to the first glass tube and a second portion of the silver chloride silver wire being internal to the first glass tube, the second portion of the silver chloride silver wire also being in contact with the first liquid; a second glass tube capped by a second frit, having a second base opposite the second frit, and having an inner surface, the first glass tube passing through the second base and defining a first portion of the first glass tube being external to the second glass tube and a second portion of the first glass tube being internal to the second glass tube, the first and second portions of the first glass tube being in fluid
  • the electrically conductive first liquid is a saturated solution of AgCl and KC1 in ethylene glycol.
  • the electrically conductive second liquid is a saturated solution of KN0 3 in propylene glycol.
  • the first glass frit is fabricated from borosilicate glass 3.3.
  • the second glass frit is fabricated from borosilicate glass 3.3.
  • the inner surface of the second glass tube comprises at least one surface tension modifying compound comprising silyl groups or organo-fluorine groups.
  • the inner surface of the second glass tube is nanotextured, such as, for example, a superhydrophobic or omniphobic surface.
  • a system comprising the double junction reference electrode according to any of the above embodiments and a reaction vessel, the reaction vessel containing a reaction mixture defining a third vapor headspace above the reaction mixture, where the third vapor headspace is in vapor communication with first vapor headspace and the second vapor headspace of the double junction reference electrode.
  • a reaction mixture comprises a liquid and may also comprise solids, such as, for example, silver nanowires.
  • the third vapor headspace is in vapor communication with the adapter of the double junction reference electrode.
  • FIG. 1 depicts the double junction reference electrode of
  • FIG. 2 depicts the voltage (mV) between a working electrode and the double junction reference electrode of FIG. 1, as a function of time (min), according to the procedure of Example 1.
  • FIG. 3 depicts the double junction reference electrode of
  • Example 2 including bridge solution glass tube portion (200-203), pressure equalizing adaptor (204), and adaptor (205) for the bridge solution tube.
  • FIG. 4 depicts the double junction reference electrode of FIG. 3 and pressure relief system, incorporated with reaction vessel.
  • FIG. 5 depicts the voltage (mV) between a working electrode and the double junction reference electrode of FIG. 4, as a function of time (min), according to the procedure of Example 2.
  • a or “an” component refers to “at least one” or “one or more” of that component.
  • the Lab VIEW® programming environment is available from National Instruments, 11500 Mopac Expwy, Austin Texas, 78759-3504, USA.
  • the ACCUMET® AP61 portable voltmeter is available from Fisher Scientific 81 Wyman Street Waltham, MA 02451 Phone Number: (781) 622-1000.
  • the SCOTCH-BRITE brand scouring pad is available from 3M Corporation, 3M Center, St. Paul, MN 55144-1000.
  • TEFLON® brand polytetrafluoroethylene (PTFE) is available from DuPont Co, 1007 North Market Street Wilmington DE 19898.
  • KC1 is potassium chloride
  • AgCl is silver chloride.
  • VYCOR® brand high silica, high temperature glass is available from Corning, Inc, Dow Corning Corporation, Corporate Center, PO Box 994 Midland, Michigan 48686-0994 USA.
  • PG is propylene glycol
  • AgN0 3 is silver nitrate.
  • FIN0 3 is nitric acid.
  • CHEMGLASS® 24/40 adapter has a serrated hose connection for vacuum or for the introduction of gases.
  • the #7 CHEM-THREAD at the top is for a vacuum tight seal of plain stem thermometers or any other tube having an O.D. between 4 and 7mm.
  • Serrated hose connection has an O.D. of 10mm at the largest serration. It is supplied complete with a compression cap and VITON o- ring. It is available from Chemglass Life Sciences, 3800 N. Mill Road, Vineland, NJ 08360.
  • Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Usually it comprises at least 5% boric oxide. The boric oxide makes the glass resistant to extreme temperatures, and also improves its resistance to chemical corrosion.
  • Borosilicate 3.3 glass has coefficient of mean linear thermal expansion a (20 °C; 300 °C) of 3.3 x 10 "6 K "1 according to DIN ISO 7991. Borosilicate glass is sold under such trade names as SIMAX®, BORCAM®, BOROSIL®, SUPRAX, KIMAX®, HEATEX®, PYREX®, ENDURAL®, SCHOTT®, and REFMEX.
  • Superhydrophobic and omniphobic surfaces are surfaces engineered to repel both polar and nopolar liquids simultaneously. These surfaces ideally display water contact angles greater than 150°, and in addition display low contact angle hysteresis which allows for fully-equilibrated, composite interfaces with drops of liquids such as alkanes or alcohols that possess significantly lower surface tension than water. These surfaces have been known to repel, for example, pentane which has a surface tension of 15.7 mN/m.
  • a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit;
  • a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the second glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit;
  • the electrode of embodiment A wherein the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
  • the electrode of embodiment H wherein the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged.
  • K. The electrode of embodiment A wherein the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
  • the electrode of embodiment A wherein the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a concentrically connected fire-polished glass tubing adaptor.
  • a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit;
  • a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit;
  • the electrode of embodiment P wherein the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates
  • the electrode of embodiment P wherein the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature and pressure at which the electrode operates.
  • the electrode of embodiment P wherein the inner surface of the second glass tube comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups or other suitable chemical modifiers used to alter the surface tension between the inner glass surface of the second glass tube and the liquid in the second glass tube
  • the electrode of embodiment Q wherein the inner surface of the second tube comprises a nanotextured (super-hydrophobic or super-omniphobic) surface applied to minimize the surface tension between the inner walls of the second glass tube and the liquid in the second glass tube.
  • a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit;
  • a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit;
  • the electrode of embodiment AC wherein the first glass frit is a VitraPOR frit fabricated from borosilicate glass 3.3.
  • AK The electrode of embodiment AC wherein the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates
  • the electrode of embodiment AC wherein the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
  • the electrode of embodiment AC wherein the inner surface of the second glass tube comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups other suitable chemical modifier to modify the surface tension between the inner glass surface of the second glass tube and the liquid comprised in the second glass tube.
  • the electrode of embodiment AC wherein the inner surface of the second tube comprises at least one nanotextured (super-hydrophobic or super- omniphobic) surface applied to minimize the surface tension between the inner walls of the second second glass tube and the liquid in the second glass tube.
  • the electrode of embodiment AC wherein the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a
  • Ion concentrations in reactions run at atmospheric and above atmospheric pressure can be monitored using an ion selective electrode that incorporates either or both a pressure equalizing tube and a surface tension modifier.
  • an Ag + ion sensitive electrode system capable of operating without error at atmospheric pressure is described.
  • Example 2 a modification to electrode which allows the electrode to function at reaction pressures above atmospheric pressure is described.
  • Example 3 a surface tension modifier is described which assists with the disposal of any gas bubble forming within the electrode at temperatures above room temperature and pressures above atmospheric pressure.
  • a working electrode was constructed by cleaning a 7.0 mm diameter 99.99% pure solid silver rod with a mild SCOTCH-BRITE pad prior to each use.
  • a double junction reference electrode (100) was constructed as shown in Fig. 1. The reference electrode employed a silver chloride coated wire (101 ) immersed in a KCl sa t ura ted-AgCl sa t U rated/Ag/AgCl ethylene glycol solution (106) enclosed in a 4 mm glass tube (102) capped with a 4 mm VYCOR® porous glass frit (103) (G0300, Princeton Applied Research), heat sealed with a
  • TEFLON® sleeve which was inserted into a saturated KN0 3 propylene glycol bridge solution (107) in a 10 mm outside diameter glass tube (104) fused to a 4 mm glass tube capped (105) with a 4 mm VYCOR® porous glass frit sealed with a TEFLON® sleeve.
  • the working electrode and the glass frit end of the double junction reference electrode were immersed in a flask containing 400 mL of propylene glycol which was heated to 150 °C.
  • To the propylene glycol was added 0.57 mL of a 1.0 M solution of AgN0 3 in propylene glycol.
  • the voltage between the working electrode and the double junction reference electrode were monitored as a function of time.
  • Fig. 2 shows the decrease in voltage measured over time. The voltage measured is a function of the silver ion concentration, which decreased as Ag + ions were reduced to silver metal.
  • an additional 0.57 mL of the 1.0 M solution in propylene glycol was injected into the flask to assess reproducibility. As shown in Fig. 2, the voltage measured increased shortly after the injection, then again decayed with time, as the added Ag + ions were reduced to silver metal.
  • This example illustrates an improvement to the electrode described in Example 1 that allows the electrode to function under reaction conditions in which the pressure is greater than atmospheric pressure.
  • the improvement involves refinement of the double junction electrode (100) with an improved design (200), shown in Fig. 3, in which the fundamental modification was the replacement of the outer glass tube (104) which holds the bridge solution with a new design (202) that maintains equal pressure between the reaction vessel and the bridge solution within the tube.
  • the fundamental modification was the replacement of the outer glass tube (104) which holds the bridge solution with a new design (202) that maintains equal pressure between the reaction vessel and the bridge solution within the tube.
  • the pressure equalizing system With the addition of the pressure equalizing system, the buildup of bubbles in the propylene glycol bridge solution (107) was minimal or non-existent.
  • the improved double junction electrode (200) was incorporated into the reaction vessel as shown in Fig. 4.
  • the outer glass tube (202) was inserted into the reaction vessel through the pressure equalizing adaptor for the bridge solution (205) and sealed with a CHEMGLASS® fitting (204).
  • the 4 mm glass tube (102) that comprises the reference electrode was placed through the outer glass tube and sealed with a threaded fitting (203).
  • Tubing (206) connected the reaction vessel (207) to the outer glass tube (202).
  • Example 1 The electrode defined in Example 1 and modified as described in this example was used to monitor the Ag + ion concentration at 150° C in propylene glycol in the following experiment: at 0.25 mL/min, 1.0 M AgN0 3 and 0.25 M NaN0 2 in propylene glycol are added to a mixture of
  • the Ag + ion concentration was monitored using the Ag + selective electrode.
  • the voltage on the electrode is a function of the silver ion concentration.
  • Voltage (mV) is plotted as a function of time (min) in Fig. 5.
  • the black dashed line and the solid black line comprise the electrode response from comparison examples.
  • the solid portion shows the effect of a gas bubble that electrically disconnects the electrode response and the dashed is the actual response when there is no gas bubble disconnection.
  • the dotted black line is the response from the invention electrode showing no bubble induced disconnects.
  • the output of this combination is a voltage reading that is functionally related to the free silver ion concentration by the Nernst equation adjusted for the temperature at which readings are taken.
  • Direct voltage readings are taken from a standard meter such as an ACCUMET® AP61, or fed into automated data collection software such as LabView®.
  • a surface tension modifier applied to the inner surface of the bridge solution tube which allows more facile release of any gas bubble that is forming, can be applied to the device described in Example 1 or Example 2.
  • the surface tension modifier can be chemical, such as from treatment to add silyl groups, organo-fluorine groups, or other suitable chemical modifiers, to the glass surface, or a mechanical modification of the glass surface, such as providing nanotextured (super-hydrophobic or super-omniphobic) surfaces.
  • organic solvents may be used in this construction, the main requirements are that the solvents dissolve a suitable salt for conductivity and having a boiling point at or above the temperature at which the electrode is desired to operate.
  • the output of this combination is a voltage reading that is functionally related to the free silver ion concentration by the Nernst equation adjusted for the temperature at which readings are taken.
  • Direct voltage readings are taken from a standard meter such as an ACCUMET® AP61, or fed into an automated data collection software such as LabView®.
  • the bridge solution glass tube (this example uses the pressure equalizing version shown above) was cleaned in 35% HN0 3 , thoroughly rinsed and dried. Next, the tube was inserted into a 5% solution of diethyldichlorosilane in hexane for about 10 minutes, drained and allowed to air dry. The exterior of the tube to be connected to the frit via thermally shrinking a TEFLON® tube was cleaned of the silane with 600 grit sandpaper. The ion specific reference electrode was then constructed as described in Examples 1 and 2.

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Abstract

An electrode comprising a first glass tube; an electrically conductive first liquid within the first glass tube defining a first vapor headspace; a silver chloride silver wire passing through the base of the first tube and also being in contact with the first liquid; a second glass tube, the first glass tube passing through the base of the second tube; an electrically conductive second liquid within the second glass tube defining a second vapor headspace; and an interface connecting and providing vapor communication between the first vapor headspace and the second vapor headspace.

Description

ELECTRODE
BACKGROUND
Silver may be reduced to silver nanostructures and, under certain circumstances, specifically to silver nanowires. See, e.g., S. E. Skrabalak; Wiley, BJ; Kim, M; Formo, EV; Xia, Y; Nano Letters 2008 8(7) 2077-81, P-Y Silvert et al., J Mater. Chem. 1997 7293-9, and P-Y Silvert et al., J. Mater. Chem. 1996 6 573-7.
Ion selective electrodes are known that operate in mainly in aqueous environments, occasionally in organic media, and generally near room temperature. See, e.g., D. T. Sawyer, A. Sobkowiak, J. L. Roberts, Jr.,
Electrochemistry for Chemists, 2nd Ed., J. Wiley & Sons, New York, 1995.
Double junction reference electrodes have been disclosed in US Patent
No. 4,401,548.
Very little is known about the Ag+ reduction process or how to control the reaction conditions to optimize a particular morphology: a novel silver ion selective electrode has been designed to operate under high temperatures and in organic solvents to solve this problem. The ion selective electrode may be used to determine the ion concentration at any point during the reaction, enabling the ability to study the chemical details of the reaction process, but in addition may be used in a feedback loop to control the concentration of ions, or the addition point of other components, during the course of the synthesis reaction in order to affect the final properties of the products.
One problem recently discovered with this type of electrode is that at higher temperatures, gases are formed during the reaction that may nucleate to form bubbles in the fine frit separating the bridge solution from the reaction medium, especially if the reaction is run at higher than atmospheric pressure. The bubble disconnects the conductive path and the electrode fails. This invention solves both the atmospheric and above atmospheric gas bubble induced electrical disconnect problems. SUMMARY
Applicants disclose an ion selective electrode capable of in situ long-term monitoring of silver ion concentration at elevated temperatures and pressures in organic media. Such an electrode is useful for monitoring and controlling silver ion concentration during silver nanowire synthesis.
Disclosed is a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the second glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and an interface that continuously connects gases above the liquid in the second glass tube to the gases above the liquid in the reaction vessel for the purpose of equilibrating the pressure above the liquids. In some embodiments the first glass tube of the electrode has an outside diameter of about 4 mm and in some embodiments the first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or, in other embodiments, the first glass frit of the said electrode is fused directly to the glass tube. In some embodiments the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3. In some embodiments the second glass tube of the said electrode has an outside diameter of about 10 mm. In other embodiments the second glass tube and the second glass frit of the said electrode are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or, in some embodiments, the second glass tube and the second glass frit is fused directly to the glass tube. In some embodiments the second glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3, and in some embodiments the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates, whereas in some embodiments the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged. In some embodiments the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates, whereas in some embodiments, the solution in the second glass tube is a saturated solution of KN03 salt in propylene glycol. In some embodiments, the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a concentrically connected fire-polished glass tubing adaptor, whereas in some embodiments, a piece of tubing connects the fire-polished end of the second glass tube to the reaction vessel for the purpose of equalizing pressure between the said reaction vessel and the concentrically connected fire-polished glass tubing adaptor of the said electrode.
Disclosed is a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and a means for modifying the surface tension of the liquid in the second tube and the inner surface of the second tube. In some embodiments first glass tube of the said electrode has an outside diameter of about 4 mm, whereas in some embodiments, the first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; whereas in some embodiments the first glass tube and the first glass frit is fused directly to the glass tube whereas in yet other embodiments the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3. In some embodiments the second glass tube has an outside diameter of about 10 mm, whereas in other embodiments the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or, in other embodiments, second glass tube and the second glass frit is fused directly to the glass tube. In some embodiments the second glass frit is a VitraPOR frit fabricated from borosilicate glass 3.3, and in some embodiments, the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates. In some embodiments the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged. In some embodiments the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature and pressure at which the electrode operates, whereas in some embodiments, the solution in the second glass tube is a saturated solution of KN03 salt in propylene glycol. In some embodiments, the inner surface of the second glass tube comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups or other suitable chemical modifiers used to alter the surface tension between the inner glass surface of the second glass tube and the liquid in the second glass tube. In some embodiments, the inner surface of the second tube comprises a nanotextured (super-hydrophobic or super-omniphobic) surface applied to minimize the surface tension between the inner walls of the second s glass tube and the liquid in the second glass tube.
Disclosed is a double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and a means for modifying the surface tension of the liquid in the second tube and the inner surface of the second tube; and an interface that continuously connects gases above the liquid in the second glass tube to the gases above the liquid in the reaction vessel for the purpose of equilibrating the pressure above the liquids. In some embodiments the said electrode comprises a first glass tube has an outside diameter of about 4 mm, whereas in some embodiments, the first glass tube and the first glass frit of the said electrodes are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or, in some embodiments, first glass tube and the first glass frit of the said electrode is fused directly to the glass tube. In some embodiments, the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3. In some embodiments the second glass tube has an outside diameter of about 10 mm. In some embodiments, the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or, in some embodiments, the second glass tube and the second glass frit is fused directly to the glass tube. In some embodiments, the second glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3. In some embodiments, the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates. In some embodiments, the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged. In some embodiments, the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the
temperature at which the electrode operates, and in some embodiments the solution in the second glass tube is a saturated solution of KN03 salt in propylene glycol. In some embodiments, the inner surface of the second glass tube of the said electrode comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups, or other suitable chemical modifiers to modify the surface tension between the inner glass surface of the second glass tube and the liquid comprised in the second glass tube, whereas in some embodiments, the inner surface of the second tube comprises at least one nanotextured (super- hydrophobic or super-omniphobic) surface applied to minimize the surface tension between the inner walls of the second glass tube and the liquid in the second glass tube. In some embodiments, the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a concentrically connected fire-polished glass tubing adaptor, and in some embodiments a piece of tubing connects the fire-polished end of the second glass tube to the reaction vessel for the purpose of equalizing pressure between the said reaction vessel and the concentrically connected fire-polished glass tubing adaptor.
Disclosed is a double junction reference electrode comprising a first glass tube capped by a first frit and having a first base opposite the first frit; an electrically conductive first liquid within the first glass tube defining a first vapor headspace between the first liquid and the first frit; a silver chloride silver wire passing through the first base and defining a first portion of the silver chloride silver wire being external to the first glass tube and a second portion of the silver chloride silver wire being internal to the first glass tube, the second portion of the silver chloride silver wire also being in contact with the first liquid; a second glass tube capped by a second frit, having a second base opposite the second frit, and having an inner surface, the first glass tube passing through the second base and defining a first portion of the first glass tube being external to the second glass tube and a second portion of the first glass tube being internal to the second glass tube, the first and second portions of the first glass tube being in fluid
communication with each other; an electrically conductive second liquid within the second glass tube defining a second vapor headspace between the second liquid and the second frit; and an interface connecting and providing vapor communication between the first vapor headspace and the second vapor headspace. In some such embodiments, the electrically conductive first liquid is a saturated solution of AgCl and KC1 in ethylene glycol. In some of the above embodiments, the electrically conductive second liquid is a saturated solution of KN03 in propylene glycol. In some of the above embodiments, the first glass frit is fabricated from borosilicate glass 3.3. In some of the above embodiments, the second glass frit is fabricated from borosilicate glass 3.3. In some of the above embodiments, the inner surface of the second glass tube comprises at least one surface tension modifying compound comprising silyl groups or organo-fluorine groups. In some of the above embodiments, the inner surface of the second glass tube is nanotextured, such as, for example, a superhydrophobic or omniphobic surface.
Disclosed is a system comprising the double junction reference electrode according to any of the above embodiments and a reaction vessel, the reaction vessel containing a reaction mixture defining a third vapor headspace above the reaction mixture, where the third vapor headspace is in vapor communication with first vapor headspace and the second vapor headspace of the double junction reference electrode. Such a reaction mixture comprises a liquid and may also comprise solids, such as, for example, silver nanowires. In some such systems, the third vapor headspace is in vapor communication with the adapter of the double junction reference electrode. DESCRIPTION OF FIGURES
FIG. 1 depicts the double junction reference electrode of
Example 1.
FIG. 2 depicts the voltage (mV) between a working electrode and the double junction reference electrode of FIG. 1, as a function of time (min), according to the procedure of Example 1.
FIG. 3 depicts the double junction reference electrode of
Example 2, including bridge solution glass tube portion (200-203), pressure equalizing adaptor (204), and adaptor (205) for the bridge solution tube.
FIG. 4 depicts the double junction reference electrode of FIG. 3 and pressure relief system, incorporated with reaction vessel.
FIG. 5 depicts the voltage (mV) between a working electrode and the double junction reference electrode of FIG. 4, as a function of time (min), according to the procedure of Example 2.
DESCRIPTION
All publications, patents, and patent documents referred to in this document are incorporated by reference herein in their entirety, as though individually incorporated by reference.
U.S. Provisional Patent Application No. 62/170,164, entitled "ELECTRODE," filed on June 3, 2015, is incorporated by reference in its entirety.
As used herein, "a" or "an" component refers to "at least one" or "one or more" of that component.
Materials and Equipment
The Lab VIEW® programming environment is available from National Instruments, 11500 Mopac Expwy, Austin Texas, 78759-3504, USA.
The ACCUMET® AP61 portable voltmeter is available from Fisher Scientific 81 Wyman Street Waltham, MA 02451 Phone Number: (781) 622-1000.
The SCOTCH-BRITE brand scouring pad is available from 3M Corporation, 3M Center, St. Paul, MN 55144-1000.
TEFLON® brand polytetrafluoroethylene (PTFE) is available from DuPont Co, 1007 North Market Street Wilmington DE 19898.
KC1 is potassium chloride.
AgCl is silver chloride.
VYCOR® brand high silica, high temperature glass is available from Corning, Inc, Dow Corning Corporation, Corporate Center, PO Box 994 Midland, Michigan 48686-0994 USA.
PG is propylene glycol.
AgN03 is silver nitrate.
FIN03 is nitric acid.
CHEMGLASS® 24/40 adapter has a serrated hose connection for vacuum or for the introduction of gases. The #7 CHEM-THREAD at the top is for a vacuum tight seal of plain stem thermometers or any other tube having an O.D. between 4 and 7mm. Serrated hose connection has an O.D. of 10mm at the largest serration. It is supplied complete with a compression cap and VITON o- ring. It is available from Chemglass Life Sciences, 3800 N. Mill Road, Vineland, NJ 08360.
Borosilicate glass is a type of glass with silica and boron trioxide as the main glass-forming constituents. Usually it comprises at least 5% boric oxide. The boric oxide makes the glass resistant to extreme temperatures, and also improves its resistance to chemical corrosion. Borosilicate 3.3 glass has coefficient of mean linear thermal expansion a (20 °C; 300 °C) of 3.3 x 10"6 K"1 according to DIN ISO 7991. Borosilicate glass is sold under such trade names as SIMAX®, BORCAM®, BOROSIL®, SUPRAX, KIMAX®, HEATEX®, PYREX®, ENDURAL®, SCHOTT®, and REFMEX.
Superhydrophobic and omniphobic surfaces are surfaces engineered to repel both polar and nopolar liquids simultaneously. These surfaces ideally display water contact angles greater than 150°, and in addition display low contact angle hysteresis which allows for fully-equilibrated, composite interfaces with drops of liquids such as alkanes or alcohols that possess significantly lower surface tension than water. These surfaces have been known to repel, for example, pentane which has a surface tension of 15.7 mN/m.
EXEMPLARY EMBODIMENTS
U.S. Provisional Patent Application No. 62/170,164, entitled "ELECTRODE," filed on June 3, 2015, which is incorporated by reference in its entirety, disclosed the following 41 exemplary non-limiting embodiments:
A. A double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and
a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the second glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and
an interface that continuously connects gases above the liquid in the second glass tube to the gases above the liquid in the reaction vessel for the purpose of equilibrating the pressure above the liquids.
B. The electrode of embodiment A wherein the first glass tube has an outside diameter of about 4 mm
C. The electrode of embodiment A wherein the first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or,
the electrode of embodiment A wherein the first glass tube and the first glass frit is fused directly to the glass tube.
D. The electrode of embodiment A wherein the first glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3.
E. The electrode of embodiment A wherein the second glass tube has an outside diameter of about 10 mm.
F. The electrode of embodiment A wherein the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or,
the electrode of embodiment A wherein the second glass tube and the second glass frit is fused directly to the glass tube.
G. The electrode of embodiment A wherein the second glass frit is a VitraPOR® frit fabricated from borosilicate glass 3.3.
H. The electrode of embodiment A wherein the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
J. The electrode of embodiment H wherein the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged. K. The electrode of embodiment A wherein the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
L. The electrode of embodiment K wherein the solution in the second glass tube is a saturated solution of KN03 salt in propylene glycol
M. The electrode of embodiment A wherein the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a concentrically connected fire-polished glass tubing adaptor.
N. The electrode of embodiment M wherein a piece of tubing connects the fire- polished end of the second glass tube to the reaction vessel for the purpose of equalizing pressure between the said reaction vessel and the concentrically connected fire-polished glass tubing adaptor.
P. A double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and
a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and
a means for modifying the surface tension of the liquid in the second tube and the inner surface of the second tube.
Q. The electrode of embodiment P wherein the first glass tube has an outside diameter of about 4 mm.
R. The electrode of embodiment P wherein the first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or,
the electrode of embodiment P wherein the first glass tube 102 and the first glass frit is fused directly to the glass tube.
S. The electrode of embodiment P wherein the first glass frit is a VitraPOR frit fabricated from borosilicate glass 3.3.
T. The electrode of embodiment P wherein the second glass tube has an outside diameter of about 10 mm.
U. The electrode of embodiment P wherein the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or,
the electrode of embodiment P wherein the second glass tube and the second glass frit is fused directly to the glass tube.
V. The electrode of embodiment P wherein the second glass frit is a VitraPOR frit fabricated from borosilicate glass 3.3.
W. The electrode of embodiment P wherein the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates
X. The electrode of embodiment W wherein the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged
Y. The electrode of embodiment P wherein the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature and pressure at which the electrode operates.
Z. The electrode of embodiment Y wherein the solution in the second glass tube is a saturated solution of KN03 salt in propylene glycol.
AA. The electrode of embodiment P wherein the inner surface of the second glass tube comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups or other suitable chemical modifiers used to alter the surface tension between the inner glass surface of the second glass tube and the liquid in the second glass tube
AB. The electrode of embodiment Q wherein the inner surface of the second tube comprises a nanotextured (super-hydrophobic or super-omniphobic) surface applied to minimize the surface tension between the inner walls of the second glass tube and the liquid in the second glass tube.
AC. A double junction reference electrode comprising a silver chloride coated silver wire and a liquid filled first glass tube capped by a first frit wherein a first portion of the silver chloride coated silver wire is external to the first glass tube and the internal and external portions of the silver chloride coated silver wire are connected by a portion of silver coated silver wire that passes through the base of the first glass tube opposite the first glass frit; and
a liquid filled second glass tube capped by a second frit wherein a first portion of the first glass tube is external to a second glass tube and the second portion of the first glass tube is internal to the glass tube and the internal and external portions of the first glass tube are connected by a portion of the first glass tube that passes through the base of the second glass tube on the end opposite of the glass frit; and
a means for modifying the surface tension of the liquid in the second tube and the inner surface of the second tube; and
an interface that continuously connects gases above the liquid in the second glass tube to the gases above the liquid in the reaction vessel for the purpose of equilibrating the pressure above the liquids.
AD. The electrode of embodiment AC wherein the first glass tube has an outside diameter of about 4 mm.
AE. The electrode of embodiment AC wherein the first glass tube and the first glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the first glass tube and outside the first frit; or, the electrode of embodiment AC wherein the first glass tube and the first glass frit is fused directly to the glass tube.
AF. The electrode of embodiment AC wherein the first glass frit is a VitraPOR frit fabricated from borosilicate glass 3.3.
AG. The electrode of embodiment AC wherein the second glass tube has an outside diameter of about 10 mm.
AH. The electrode of embodiment AC wherein the second glass tube and the second glass frit are heat sealed to each other via use of a heat treated intermediate TEFLON® tube fitted outside of the second glass tube and outside the second frit; or,
the electrode of embodiment AC wherein the second glass tube and the second glass frit is fused directly to the glass tube.
AJ. The electrode of embodiment AC wherein the second glass frit is a
VitraPOR® frit fabricated from borosilicate glass 3.3.
AK. The electrode of embodiment AC wherein the liquid in the first glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates
AL. The electrode of embodiment AK wherein the solution in the first glass tube is a saturated solution of AgCl and KC1 in ethylene glycol into which the silver chloride coated silver wire is at least partially submerged.
AM. The electrode of embodiment AC wherein the liquid in the second glass tube is a solvent and salt combination capable of providing electrical conductivity at the temperature at which the electrode operates.
AN. The electrode of embodiment AM wherein the solution in the second glass tube is a saturated solution of KNO3 salt in propylene glycol.
AP. The electrode of embodiment AC wherein the inner surface of the second glass tube comprises at least one surface tension modifier in the form of silyl groups, organo-fluorine groups other suitable chemical modifier to modify the surface tension between the inner glass surface of the second glass tube and the liquid comprised in the second glass tube.
AQ. The electrode of embodiment AC wherein the inner surface of the second tube comprises at least one nanotextured (super-hydrophobic or super- omniphobic) surface applied to minimize the surface tension between the inner walls of the second second glass tube and the liquid in the second glass tube. AR. The electrode of embodiment AC wherein the interface connecting the second glass tube to the first comprises a hole in the glass tubing and a
concentrically connected fire-polished glass tubing adaptor.
AS. The electrode of embodiment AR wherein a piece of tubing connects the fire- polished end of the second glass tube to the reaction vessel for the purpose of equalizing pressure between the said reaction vessel and the concentrically connected fire-polished glass tubing adaptor. EXAMPLES
Ion concentrations in reactions run at atmospheric and above atmospheric pressure can be monitored using an ion selective electrode that incorporates either or both a pressure equalizing tube and a surface tension modifier. In Example 1 , an Ag+ ion sensitive electrode system capable of operating without error at atmospheric pressure is described. In Example 2, a modification to electrode which allows the electrode to function at reaction pressures above atmospheric pressure is described. In Example 3, a surface tension modifier is described which assists with the disposal of any gas bubble forming within the electrode at temperatures above room temperature and pressures above atmospheric pressure.
Example 1
A working electrode was constructed by cleaning a 7.0 mm diameter 99.99% pure solid silver rod with a mild SCOTCH-BRITE pad prior to each use. A double junction reference electrode (100) was constructed as shown in Fig. 1. The reference electrode employed a silver chloride coated wire (101 ) immersed in a KClsaturated-AgClsatUrated/Ag/AgCl ethylene glycol solution (106) enclosed in a 4 mm glass tube (102) capped with a 4 mm VYCOR® porous glass frit (103) (G0300, Princeton Applied Research), heat sealed with a
TEFLON® sleeve, which was inserted into a saturated KN03 propylene glycol bridge solution (107) in a 10 mm outside diameter glass tube (104) fused to a 4 mm glass tube capped (105) with a 4 mm VYCOR® porous glass frit sealed with a TEFLON® sleeve.
The working electrode and the glass frit end of the double junction reference electrode were immersed in a flask containing 400 mL of propylene glycol which was heated to 150 °C. To the propylene glycol was added 0.57 mL of a 1.0 M solution of AgN03 in propylene glycol. The voltage between the working electrode and the double junction reference electrode were monitored as a function of time. Fig. 2 shows the decrease in voltage measured over time. The voltage measured is a function of the silver ion concentration, which decreased as Ag+ ions were reduced to silver metal. Once the voltage readings stabilized, an additional 0.57 mL of the 1.0 M solution in propylene glycol was injected into the flask to assess reproducibility. As shown in Fig. 2, the voltage measured increased shortly after the injection, then again decayed with time, as the added Ag+ ions were reduced to silver metal.
Example 2
This example illustrates an improvement to the electrode described in Example 1 that allows the electrode to function under reaction conditions in which the pressure is greater than atmospheric pressure. The improvement involves refinement of the double junction electrode (100) with an improved design (200), shown in Fig. 3, in which the fundamental modification was the replacement of the outer glass tube (104) which holds the bridge solution with a new design (202) that maintains equal pressure between the reaction vessel and the bridge solution within the tube. With the addition of the pressure equalizing system, the buildup of bubbles in the propylene glycol bridge solution (107) was minimal or non-existent.
The improved double junction electrode (200) was incorporated into the reaction vessel as shown in Fig. 4. The outer glass tube (202) was inserted into the reaction vessel through the pressure equalizing adaptor for the bridge solution (205) and sealed with a CHEMGLASS® fitting (204). The 4 mm glass tube (102) that comprises the reference electrode was placed through the outer glass tube and sealed with a threaded fitting (203). Tubing (206) connected the reaction vessel (207) to the outer glass tube (202).
The electrode defined in Example 1 and modified as described in this example was used to monitor the Ag+ ion concentration at 150° C in propylene glycol in the following experiment: at 0.25 mL/min, 1.0 M AgN03 and 0.25 M NaN02 in propylene glycol are added to a mixture of
polyvinylpyrrolidone, NH4C1, and NH4Br in propylene glycol at 150°C. The Ag+ ion concentration was monitored using the Ag+ selective electrode. The voltage on the electrode is a function of the silver ion concentration. Voltage (mV) is plotted as a function of time (min) in Fig. 5. The black dashed line and the solid black line comprise the electrode response from comparison examples. The solid portion shows the effect of a gas bubble that electrically disconnects the electrode response and the dashed is the actual response when there is no gas bubble disconnection. The dotted black line is the response from the invention electrode showing no bubble induced disconnects.
The output of this combination is a voltage reading that is functionally related to the free silver ion concentration by the Nernst equation adjusted for the temperature at which readings are taken. Direct voltage readings are taken from a standard meter such as an ACCUMET® AP61, or fed into automated data collection software such as LabView®.
Example 3
A surface tension modifier applied to the inner surface of the bridge solution tube, which allows more facile release of any gas bubble that is forming, can be applied to the device described in Example 1 or Example 2. The surface tension modifier can be chemical, such as from treatment to add silyl groups, organo-fluorine groups, or other suitable chemical modifiers, to the glass surface, or a mechanical modification of the glass surface, such as providing nanotextured (super-hydrophobic or super-omniphobic) surfaces.
Many organic solvents may be used in this construction, the main requirements are that the solvents dissolve a suitable salt for conductivity and having a boiling point at or above the temperature at which the electrode is desired to operate.
The output of this combination is a voltage reading that is functionally related to the free silver ion concentration by the Nernst equation adjusted for the temperature at which readings are taken. Direct voltage readings are taken from a standard meter such as an ACCUMET® AP61, or fed into an automated data collection software such as LabView®.
Surface tension modification by silylation: the bridge solution glass tube (this example uses the pressure equalizing version shown above) was cleaned in 35% HN03, thoroughly rinsed and dried. Next, the tube was inserted into a 5% solution of diethyldichlorosilane in hexane for about 10 minutes, drained and allowed to air dry. The exterior of the tube to be connected to the frit via thermally shrinking a TEFLON® tube was cleaned of the silane with 600 grit sandpaper. The ion specific reference electrode was then constructed as described in Examples 1 and 2.
The invention has been described in detail with reference to specific embodiments, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the attached claims, and all changes that come within the meaning and range of equivalents thereof are intended to be embraced therein.

Claims

CLAIMS:
1. A double junction reference electrode comprising:
a first glass tube capped by a first frit and having a first base opposite the first frit;
an electrically conductive first liquid within the first glass tube defining a first vapor headspace between the first liquid and the first frit;
a silver chloride silver wire passing through the first base and defining a first portion of the silver chloride silver wire being external to the first glass tube and a second portion of the silver chloride silver wire being internal to the first glass tube, the second portion of the silver chloride silver wire also being in contact with the first liquid;
a second glass tube capped by a second frit, having a second base opposite the second frit, and having an inner surface, the first glass tube passing through the second base and defining a first portion of the first glass tube being external to the second glass tube and a second portion of the first glass tube being internal to the second glass tube, the first and second portions of the first glass tube being in fluid communication with each other;
an electrically conductive second liquid within the second glass tube defining a second vapor headspace between the second liquid and the second frit; and
an interface connecting and providing vapor communication between the first vapor headspace and the second vapor headspace.
2. The double junction reference electrode according to claim 1, wherein the electrically conductive first liquid is a saturated solution of AgCl and KC1 in ethylene glycol.
3. The double junction reference electrode according to either of claims 1 or 2, wherein the electrically conductive second liquid is a saturated solution of KN03 in propylene glycol.
4. The double junction reference electrode according to any of claims 1-3, wherein the first glass frit is fabricated from borosilicate glass 3.3.
5. The double junction reference electrode according to any of claims 1-4, wherein the second glass frit is fabricated from borosilicate glass 3.3.
6. The double junction reference electrode according to any of claims 1-5, wherein the inner surface of the second glass tube comprises at least one surface tension modifying compound comprising silyl groups or organo-fluorine groups.
7. The double junction reference electrode according to any of claims 1-6, wherein the inner surface of the second glass tube is nanotextured.
8. A system comprising the double junction reference electrode according to any of claims 1-7 and a reaction vessel,
the reaction vessel containing a reaction mixture defining a third vapor headspace above the reaction mixture,
wherein the third vapor headspace is in vapor communication with first vapor headspace and the second vapor headspace.
9. The system according to claim 8, wherein the third vapor headspace is in vapor communication with the adapter.
PCT/US2016/035369 2015-06-03 2016-06-02 Electrode WO2016196702A1 (en)

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