Glen D. O'Neil
- Courses4
- Reviews22
- School: Montclair State University
- Campus:
- Department: Chemistry
- Email address: Join to see
- Phone: Join to see
-
Location:
1 Normal Ave
Montclair, NJ - 07043 - Dates at Montclair State University: November 2016 - June 2020
- Office Hours: Join to see
N/A
Would take again: Yes
For Credit: Yes
0
0
Not Mandatory
Awesome
Prof. Glen is amazing! He really cares about his students and he wants everyone to succeed. He's very willing to help. As long as you keep up with all the work, you'll do fine. He doesn't complicate things at all. He's very approachable and flexible!
N/A
Would take again: No
For Credit: Yes
0
0
Mandatory
Awful
Professor O'Neil was cool and nice. However, his lectures were not helpful at all. He always used examples that were nothing compared to the questions he'd put on the tests. The tests were very hard and it's hard to pass. After you do the tests, you just want to cry all day, because of how hard it is. He thinks that all students are smart students in his class.
N/A
Would take again: No
For Credit: Yes
0
0
Mandatory
Average
Yeah, chemistry would be difficult no matter what, but it doesn't help that Professor O'Neil makes tests more difficult in order to make you think more. He claims that it aids learning and can aid students, but it only served to depress me because of the grades I was receiving and how I felt like I didn't know anything until I saw the exam even though I actually understood the homework.
N/A
Would take again: Yes
For Credit: Yes
0
0
Awesome
Professor O'Neil was very understanding, especially during this pandemic. However, you have to work for your grade. He'll give more difficult exams than other professors, but this will prepare you for the final. If given a chance, I'll absolutely take his class again.
N/A
Would take again: No
For Credit: Yes
0
0
Mandatory
Average
Professor O'Neil was just fine. Compared to other chemistry teachers, he's very organized, but still challenging. He calls on students randomly to answer questions during every lecture. Also, his exams were very difficult. He always spent time during the lectures and had no consideration for the students who fought during pandemic. If you're going to take him, you have to work.
Biography
Montclair State University - Chemistry
Experience
University of Warwick
Postdoctoral Research Associate
Glen worked at University of Warwick as a Postdoctoral Research Associate
Columbia University in the City of New York
Postdoctoral Research Associate
Glen worked at Columbia University in the City of New York as a Postdoctoral Research Associate
Tufts University
Graduate Research Assistant
Glen worked at Tufts University as a Graduate Research Assistant
Montclair State University
Assistant Professor
Glen worked at Montclair State University as a Assistant Professor
Education
Tufts University
Doctor of Philosophy (PhD)
Analytical Chemistry
Tufts University
Graduate Research Assistant
University of Delaware
Bachelor of Science (B.S.)
Chemistry
Publications
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Electrochemistry of Aqueous Colloidal Graphene Oxide on Pt Electrodes
Langmuir
The electrochemical behavior of colloidal solutions of graphene oxide (GO) is described here in detail. The GO reduction is shown to exhibit near-reversible electron transfer on Pt electrodes, based on E1/2 and ΔEp values. The observed peak current is found to depend linearly on the concentration of the GO and the square root of the scan rate, suggesting that the response is diffusion-limited. The difference between the experimental and diffusion-only limited theoretical current values suggests that migration may be hindering mass transport to the electrode surface. Varying the type and concentration of the supporting electrolyte showed that mass transport is weakly influenced by the presence of negative charges on the graphene particles. The effect of pH on GO was also investigated, and it was found that the reduction peak heights were directly related to proton concentration in acidic solutions. On the basis of the results presented here, we propose that the observed response of GO on Pt electrodes is a result of the reduction of protons from the colloidal double layer. This difference is observed only because the Pt electrode surface can efficiently catalyze proton reduction.
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Electrochemistry of Aqueous Colloidal Graphene Oxide on Pt Electrodes
Langmuir
The electrochemical behavior of colloidal solutions of graphene oxide (GO) is described here in detail. The GO reduction is shown to exhibit near-reversible electron transfer on Pt electrodes, based on E1/2 and ΔEp values. The observed peak current is found to depend linearly on the concentration of the GO and the square root of the scan rate, suggesting that the response is diffusion-limited. The difference between the experimental and diffusion-only limited theoretical current values suggests that migration may be hindering mass transport to the electrode surface. Varying the type and concentration of the supporting electrolyte showed that mass transport is weakly influenced by the presence of negative charges on the graphene particles. The effect of pH on GO was also investigated, and it was found that the reduction peak heights were directly related to proton concentration in acidic solutions. On the basis of the results presented here, we propose that the observed response of GO on Pt electrodes is a result of the reduction of protons from the colloidal double layer. This difference is observed only because the Pt electrode surface can efficiently catalyze proton reduction.
Scalable Hydrogen Production with a 3D-printed Membrane-less Water Electrolyzer
J. Electrochem. Soc.
Ion-conducting membranes are essential components in many electrochemical devices, but they often add substantial cost, limit performance, and are susceptible to degradation. This work investigates membraneless electrochemical flow cells for hydrogen production from water electrolysis that are based on angled mesh flow-through electrodes. These devices can be fabricated with as few as three parts (anode, cathode, and cell body), reflecting their simplicity and potential for low-cost manufacture. 3D printing was used to fabricate prototype electrolyzers that were demonstrated to be electrolyte agnostic, modular, and capable of operating with minimal product crossover. Prototype electrolyzers operating in acidic and alkaline solutions achieved electrolysis efficiencies of 61.9% and 72.5%, respectively, (based on the higher heating value of H2) when operated at 100 mA cm−2. Product crossover was investigated using in situ electrochemical sensors, in situ imaging, and by gas chromatography (GC). GC analysis found that 2.8% of the H2 crossed over from the cathode to the anode stream under electrolysis at 100 mA cm−2 and fluid velocity of 26.5 cm s−1. Additionally, modularity was demonstrated with a three-cell stack, and high-speed video measurements tracking bubble evolution from electrode surfaces provide valuable insight for the further optimization of electrolyzer design and performance.
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Electrochemistry of Aqueous Colloidal Graphene Oxide on Pt Electrodes
Langmuir
The electrochemical behavior of colloidal solutions of graphene oxide (GO) is described here in detail. The GO reduction is shown to exhibit near-reversible electron transfer on Pt electrodes, based on E1/2 and ΔEp values. The observed peak current is found to depend linearly on the concentration of the GO and the square root of the scan rate, suggesting that the response is diffusion-limited. The difference between the experimental and diffusion-only limited theoretical current values suggests that migration may be hindering mass transport to the electrode surface. Varying the type and concentration of the supporting electrolyte showed that mass transport is weakly influenced by the presence of negative charges on the graphene particles. The effect of pH on GO was also investigated, and it was found that the reduction peak heights were directly related to proton concentration in acidic solutions. On the basis of the results presented here, we propose that the observed response of GO on Pt electrodes is a result of the reduction of protons from the colloidal double layer. This difference is observed only because the Pt electrode surface can efficiently catalyze proton reduction.
Scalable Hydrogen Production with a 3D-printed Membrane-less Water Electrolyzer
J. Electrochem. Soc.
Ion-conducting membranes are essential components in many electrochemical devices, but they often add substantial cost, limit performance, and are susceptible to degradation. This work investigates membraneless electrochemical flow cells for hydrogen production from water electrolysis that are based on angled mesh flow-through electrodes. These devices can be fabricated with as few as three parts (anode, cathode, and cell body), reflecting their simplicity and potential for low-cost manufacture. 3D printing was used to fabricate prototype electrolyzers that were demonstrated to be electrolyte agnostic, modular, and capable of operating with minimal product crossover. Prototype electrolyzers operating in acidic and alkaline solutions achieved electrolysis efficiencies of 61.9% and 72.5%, respectively, (based on the higher heating value of H2) when operated at 100 mA cm−2. Product crossover was investigated using in situ electrochemical sensors, in situ imaging, and by gas chromatography (GC). GC analysis found that 2.8% of the H2 crossed over from the cathode to the anode stream under electrolysis at 100 mA cm−2 and fluid velocity of 26.5 cm s−1. Additionally, modularity was demonstrated with a three-cell stack, and high-speed video measurements tracking bubble evolution from electrode surfaces provide valuable insight for the further optimization of electrolyzer design and performance.
The use of graphene oxide as a fixed charge carrier in ion-selective electrodes
Electrochemistry Communications
Here we present for the first time the use of graphene oxide nanoparticles as fixed-charge carriers for the development of membrane-based cation selective ion-selective electrodes (ISEs). The GO nanoparticles are dispersed into tetrahydrofuran, and thus easily incorporated into the ISE membrane. The effect of GO concentration on bulk membrane resistance (Rb) is measured using electrochemical impedance spectroscopy, and a significant decrease in Rb is observed with increasing [GO]. The permselectivity of these membranes was investigated using conventional potentiometry, and the results suggest that GO is able to decrease membrane resistance through electrostatic interactions between the negatively charged particles and the positively charged cations. The use of these nanostructures in the pH-sensitive ISE based on ETH-1907 ionophore paves the way to a new method of constructing potentiometric sensors. ISEs with increased lifetimes and stabile potentials could be developed based on these materials, allowing ionophore and charge carrier to be combined in a way that promotes miniaturization of ISEs with more optimal analytical characteristics.
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Electrochemistry of Aqueous Colloidal Graphene Oxide on Pt Electrodes
Langmuir
The electrochemical behavior of colloidal solutions of graphene oxide (GO) is described here in detail. The GO reduction is shown to exhibit near-reversible electron transfer on Pt electrodes, based on E1/2 and ΔEp values. The observed peak current is found to depend linearly on the concentration of the GO and the square root of the scan rate, suggesting that the response is diffusion-limited. The difference between the experimental and diffusion-only limited theoretical current values suggests that migration may be hindering mass transport to the electrode surface. Varying the type and concentration of the supporting electrolyte showed that mass transport is weakly influenced by the presence of negative charges on the graphene particles. The effect of pH on GO was also investigated, and it was found that the reduction peak heights were directly related to proton concentration in acidic solutions. On the basis of the results presented here, we propose that the observed response of GO on Pt electrodes is a result of the reduction of protons from the colloidal double layer. This difference is observed only because the Pt electrode surface can efficiently catalyze proton reduction.
Scalable Hydrogen Production with a 3D-printed Membrane-less Water Electrolyzer
J. Electrochem. Soc.
Ion-conducting membranes are essential components in many electrochemical devices, but they often add substantial cost, limit performance, and are susceptible to degradation. This work investigates membraneless electrochemical flow cells for hydrogen production from water electrolysis that are based on angled mesh flow-through electrodes. These devices can be fabricated with as few as three parts (anode, cathode, and cell body), reflecting their simplicity and potential for low-cost manufacture. 3D printing was used to fabricate prototype electrolyzers that were demonstrated to be electrolyte agnostic, modular, and capable of operating with minimal product crossover. Prototype electrolyzers operating in acidic and alkaline solutions achieved electrolysis efficiencies of 61.9% and 72.5%, respectively, (based on the higher heating value of H2) when operated at 100 mA cm−2. Product crossover was investigated using in situ electrochemical sensors, in situ imaging, and by gas chromatography (GC). GC analysis found that 2.8% of the H2 crossed over from the cathode to the anode stream under electrolysis at 100 mA cm−2 and fluid velocity of 26.5 cm s−1. Additionally, modularity was demonstrated with a three-cell stack, and high-speed video measurements tracking bubble evolution from electrode surfaces provide valuable insight for the further optimization of electrolyzer design and performance.
The use of graphene oxide as a fixed charge carrier in ion-selective electrodes
Electrochemistry Communications
Here we present for the first time the use of graphene oxide nanoparticles as fixed-charge carriers for the development of membrane-based cation selective ion-selective electrodes (ISEs). The GO nanoparticles are dispersed into tetrahydrofuran, and thus easily incorporated into the ISE membrane. The effect of GO concentration on bulk membrane resistance (Rb) is measured using electrochemical impedance spectroscopy, and a significant decrease in Rb is observed with increasing [GO]. The permselectivity of these membranes was investigated using conventional potentiometry, and the results suggest that GO is able to decrease membrane resistance through electrostatic interactions between the negatively charged particles and the positively charged cations. The use of these nanostructures in the pH-sensitive ISE based on ETH-1907 ionophore paves the way to a new method of constructing potentiometric sensors. ISEs with increased lifetimes and stabile potentials could be developed based on these materials, allowing ionophore and charge carrier to be combined in a way that promotes miniaturization of ISEs with more optimal analytical characteristics.
Single-step fabrication of electrochemical flow cells utilizing multi-material 3D printing
Electrochemistry Communications
Here we present methodology for fabricating electrochemical flow cells with embedded carbon-composite electrodes in a single step using simultaneous 3D printing of insulating poly(lactic acid) (PLA) and a commercially available graphene–PLA composite. This work is significant because it is the first demonstration that devices capable of fluid handling and electrochemical sensing can be produced in a single fabrication step using inexpensive equipment. We demonstrate the broad utility of this approach using a channel-flow configuration as an exemplary system for hydrodynamic electrochemistry. Unmodified devices were characterized using hydrodynamic electrochemistry, and behave according to the well-established Levich equation. We also characterized the fabrication reproducibility and found that the devices were within 3% RSD. The 3D-printed sensors we employed were subsequently modified by electroplating Au and used under flowing conditions to detect catechol, whose oxidation requires two electrons and two protons and is thus more challenging to analyze than the outer-sphere FcCH2OH. We envision these results will pave the way for the development of highly customized micro-total analysis systems that include embedded electrochemical sensors for a variety of redox-active analytes.
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Electrochemistry of Aqueous Colloidal Graphene Oxide on Pt Electrodes
Langmuir
The electrochemical behavior of colloidal solutions of graphene oxide (GO) is described here in detail. The GO reduction is shown to exhibit near-reversible electron transfer on Pt electrodes, based on E1/2 and ΔEp values. The observed peak current is found to depend linearly on the concentration of the GO and the square root of the scan rate, suggesting that the response is diffusion-limited. The difference between the experimental and diffusion-only limited theoretical current values suggests that migration may be hindering mass transport to the electrode surface. Varying the type and concentration of the supporting electrolyte showed that mass transport is weakly influenced by the presence of negative charges on the graphene particles. The effect of pH on GO was also investigated, and it was found that the reduction peak heights were directly related to proton concentration in acidic solutions. On the basis of the results presented here, we propose that the observed response of GO on Pt electrodes is a result of the reduction of protons from the colloidal double layer. This difference is observed only because the Pt electrode surface can efficiently catalyze proton reduction.
Scalable Hydrogen Production with a 3D-printed Membrane-less Water Electrolyzer
J. Electrochem. Soc.
Ion-conducting membranes are essential components in many electrochemical devices, but they often add substantial cost, limit performance, and are susceptible to degradation. This work investigates membraneless electrochemical flow cells for hydrogen production from water electrolysis that are based on angled mesh flow-through electrodes. These devices can be fabricated with as few as three parts (anode, cathode, and cell body), reflecting their simplicity and potential for low-cost manufacture. 3D printing was used to fabricate prototype electrolyzers that were demonstrated to be electrolyte agnostic, modular, and capable of operating with minimal product crossover. Prototype electrolyzers operating in acidic and alkaline solutions achieved electrolysis efficiencies of 61.9% and 72.5%, respectively, (based on the higher heating value of H2) when operated at 100 mA cm−2. Product crossover was investigated using in situ electrochemical sensors, in situ imaging, and by gas chromatography (GC). GC analysis found that 2.8% of the H2 crossed over from the cathode to the anode stream under electrolysis at 100 mA cm−2 and fluid velocity of 26.5 cm s−1. Additionally, modularity was demonstrated with a three-cell stack, and high-speed video measurements tracking bubble evolution from electrode surfaces provide valuable insight for the further optimization of electrolyzer design and performance.
The use of graphene oxide as a fixed charge carrier in ion-selective electrodes
Electrochemistry Communications
Here we present for the first time the use of graphene oxide nanoparticles as fixed-charge carriers for the development of membrane-based cation selective ion-selective electrodes (ISEs). The GO nanoparticles are dispersed into tetrahydrofuran, and thus easily incorporated into the ISE membrane. The effect of GO concentration on bulk membrane resistance (Rb) is measured using electrochemical impedance spectroscopy, and a significant decrease in Rb is observed with increasing [GO]. The permselectivity of these membranes was investigated using conventional potentiometry, and the results suggest that GO is able to decrease membrane resistance through electrostatic interactions between the negatively charged particles and the positively charged cations. The use of these nanostructures in the pH-sensitive ISE based on ETH-1907 ionophore paves the way to a new method of constructing potentiometric sensors. ISEs with increased lifetimes and stabile potentials could be developed based on these materials, allowing ionophore and charge carrier to be combined in a way that promotes miniaturization of ISEs with more optimal analytical characteristics.
Single-step fabrication of electrochemical flow cells utilizing multi-material 3D printing
Electrochemistry Communications
Here we present methodology for fabricating electrochemical flow cells with embedded carbon-composite electrodes in a single step using simultaneous 3D printing of insulating poly(lactic acid) (PLA) and a commercially available graphene–PLA composite. This work is significant because it is the first demonstration that devices capable of fluid handling and electrochemical sensing can be produced in a single fabrication step using inexpensive equipment. We demonstrate the broad utility of this approach using a channel-flow configuration as an exemplary system for hydrodynamic electrochemistry. Unmodified devices were characterized using hydrodynamic electrochemistry, and behave according to the well-established Levich equation. We also characterized the fabrication reproducibility and found that the devices were within 3% RSD. The 3D-printed sensors we employed were subsequently modified by electroplating Au and used under flowing conditions to detect catechol, whose oxidation requires two electrons and two protons and is thus more challenging to analyze than the outer-sphere FcCH2OH. We envision these results will pave the way for the development of highly customized micro-total analysis systems that include embedded electrochemical sensors for a variety of redox-active analytes.
Methods of Photoelectrode Characterization with High Spatial and Temporal Resolution
Energy Environ. Sci.
Materials and photoelectrode architectures that are highly efficient, extremely stable, and made from low cost materials are required for commercially viable photoelectrochemical (PEC) water-splitting technology. A key challenge is the heterogeneous nature of real-world materials, which often possess spatial variation in their crystal structure, morphology, and/or composition at the nano-, micro-, or macro-scale. Different structures and compositions can have vastly different properties and can therefore strongly influence the overall performance of the photoelectrode through complex structure-property relationships. A complete understanding of photoelectrode materials would also involve elucidation of processes such as carrier collection and electrochemical charge transfer that occur at very fast time scales. We present herein an overview of a broad suite of experimental and computational tools that can be used to define the structure-property relationships of photoelectrode materials at small dimensions and on fast time scales. A major focus is on in situ scanning-probe measurement (SPM) techniques that possess the ability to measure differences in optical, electronic, catalytic, and physical properties with nano- or micro-scale spatial resolution. In situ ultrafast spectroscopic techniques, used to probe carrier dynamics involved with processes such as carrier generation, recombination, and interfacial charge transport, are also discussed. Complementing all of these experimental techniques are computational atomistic modeling tools, which can be invaluable for interpreting experimental results, aiding in materials discovery, and interrogating PEC processes at length and time scales not currently accessible by experiment. In addition to reviewing the basic capabilities of these experimental and computational techniques, we highlight key opportunities and limitations of applying these tools for the development of PEC materials.
Scanning Line Probe Microscopy: Beyond the Point Probe
Analytical Chemistry
Scanning probe microscopy (SPM) techniques have become indispensable tools for studying nano- and microscale materials and processes but suffer from a trade-off between resolution and areal scan rate that limits their utility for a number of applications and sample types. Here, we present a novel approach to SPM imaging based on combining nonlocal scanning line probes with compressed sensing (CS) signal analysis methods. Using scanning electrochemical microscopy (SECM) as an exemplar SPM technique, we demonstrate this approach using continuous microband electrodes, or line probes, which are used to perform chemical imaging of electrocatalytic Pt discs deposited on an inert substrate. These results demonstrate the potential to achieve high areal SPM imaging rates using nonlocal scanning probes and CS image reconstruction.
Solid Contact Ion Selective Electrodes for In Situ Measurements at High Pressure
Analytical Chemistry
Solid contact polymeric ion-selective electrodes (SC-ISEs) have been fabricated using microporous carbon (μPC) as the ion-to-electron transducer, loaded with a liquid membrane cocktail containing both ionophore and additive dissolved in plasticizer. These SC-ISEs were characterized and shown to be suitable for analysis in aqueous environments at pressures of 100 bar. Potassium ISEs, prepared in this manner, showed excellent performance at both atmospheric and elevated pressures, as evaluated by their response slopes and potential stability. These novel SC-ISEs were shown to be capable of measuring K+ at pressures under which traditional liquid-filled ISEs fail. Furthermore, the effect of pressure on the response of these sensors had little or no effect on potential, sensitivity, or limit of detection. High pressure sensor calibrations were performed in standard solutions as well as simulated seawater samples to demonstrate their usefulness as sensors in a deep-sea environment. These novel SC-ISE sensors show promise of providing the ability to make in situ real-time measurements of ion-fluxes near deep-ocean geothermal vents.
Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X-ray Fluorescence
Analytical Chemistry
The development and application of a new methodology, in situ electrochemical X-ray fluorescence (EC-XRF), is described that enables direct identification and quantification of heavy metals in solution. A freestanding film of boron-doped diamond serves as both an X-ray window and the electrode material. The electrode is biased at a suitable driving potential to electroplate metals from solution onto the electrode surface. Simultaneously, X-rays that pass through the back side of the electrode interrogate the time-dependent electrodeposition process by virtue of the XRF signals, which are unique to each metal. In this way it is possible to unambiguously identify which metals are in solution and relate the XRF signal intensity to a concentration of metal species in solution. To increase detection sensitivity and reduce detection times, solution is flown over the electrode surface by use of a wall-jet configuration. Initial studies focused on the in situ detection of Pb2+, where concentration detection limits of 99 nM were established in this proof-of-concept study (although significantly lower values are anticipated with system refinement). This is more than 3 orders of magnitude lower than that achievable by XRF alone in a flowing solution (0.68 mM). In situ EC-XRF measurements were also carried out on a multimetal solution containing Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+ (all at 10 μM concentration). Identification of five of these metals was possible in one simple measurement. Time-dependent EC-XRF nucleation data for the five metals, recorded simultaneously, demonstrated similar deposition rates. Studies are now underway to lower detection limits and provide a quantitative understanding of EC-XRF responses in real, multimetal solutions. Finally, the production of custom-designed portable in situ EC-XRF instrumentation will make heavy metal analysis at the source a very realistic possibility.
Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude
Analytical Chemistry
The development of a novel analytical technique, electrochemical X-ray fluorescence (EC-XRF), is described and applied to the quantitative detection of heavy metals in solution, achieving sub-ppb limits of detection (LOD). In EC-XRF, electrochemical preconcentration of a species of interest onto the target electrode is achieved here by cathodic electrodeposition. Unambiguous elemental identification and quantification of metal concentration is then made using XRF. This simple electrochemical preconcentration step improves the LOD of energy dispersive XRF by over 4 orders of magnitude (for similar sample preparation time scales).
Electrochemistry of Aqueous Colloidal Graphene Oxide on Pt Electrodes
Langmuir
The electrochemical behavior of colloidal solutions of graphene oxide (GO) is described here in detail. The GO reduction is shown to exhibit near-reversible electron transfer on Pt electrodes, based on E1/2 and ΔEp values. The observed peak current is found to depend linearly on the concentration of the GO and the square root of the scan rate, suggesting that the response is diffusion-limited. The difference between the experimental and diffusion-only limited theoretical current values suggests that migration may be hindering mass transport to the electrode surface. Varying the type and concentration of the supporting electrolyte showed that mass transport is weakly influenced by the presence of negative charges on the graphene particles. The effect of pH on GO was also investigated, and it was found that the reduction peak heights were directly related to proton concentration in acidic solutions. On the basis of the results presented here, we propose that the observed response of GO on Pt electrodes is a result of the reduction of protons from the colloidal double layer. This difference is observed only because the Pt electrode surface can efficiently catalyze proton reduction.
Scalable Hydrogen Production with a 3D-printed Membrane-less Water Electrolyzer
J. Electrochem. Soc.
Ion-conducting membranes are essential components in many electrochemical devices, but they often add substantial cost, limit performance, and are susceptible to degradation. This work investigates membraneless electrochemical flow cells for hydrogen production from water electrolysis that are based on angled mesh flow-through electrodes. These devices can be fabricated with as few as three parts (anode, cathode, and cell body), reflecting their simplicity and potential for low-cost manufacture. 3D printing was used to fabricate prototype electrolyzers that were demonstrated to be electrolyte agnostic, modular, and capable of operating with minimal product crossover. Prototype electrolyzers operating in acidic and alkaline solutions achieved electrolysis efficiencies of 61.9% and 72.5%, respectively, (based on the higher heating value of H2) when operated at 100 mA cm−2. Product crossover was investigated using in situ electrochemical sensors, in situ imaging, and by gas chromatography (GC). GC analysis found that 2.8% of the H2 crossed over from the cathode to the anode stream under electrolysis at 100 mA cm−2 and fluid velocity of 26.5 cm s−1. Additionally, modularity was demonstrated with a three-cell stack, and high-speed video measurements tracking bubble evolution from electrode surfaces provide valuable insight for the further optimization of electrolyzer design and performance.
The use of graphene oxide as a fixed charge carrier in ion-selective electrodes
Electrochemistry Communications
Here we present for the first time the use of graphene oxide nanoparticles as fixed-charge carriers for the development of membrane-based cation selective ion-selective electrodes (ISEs). The GO nanoparticles are dispersed into tetrahydrofuran, and thus easily incorporated into the ISE membrane. The effect of GO concentration on bulk membrane resistance (Rb) is measured using electrochemical impedance spectroscopy, and a significant decrease in Rb is observed with increasing [GO]. The permselectivity of these membranes was investigated using conventional potentiometry, and the results suggest that GO is able to decrease membrane resistance through electrostatic interactions between the negatively charged particles and the positively charged cations. The use of these nanostructures in the pH-sensitive ISE based on ETH-1907 ionophore paves the way to a new method of constructing potentiometric sensors. ISEs with increased lifetimes and stabile potentials could be developed based on these materials, allowing ionophore and charge carrier to be combined in a way that promotes miniaturization of ISEs with more optimal analytical characteristics.
Single-step fabrication of electrochemical flow cells utilizing multi-material 3D printing
Electrochemistry Communications
Here we present methodology for fabricating electrochemical flow cells with embedded carbon-composite electrodes in a single step using simultaneous 3D printing of insulating poly(lactic acid) (PLA) and a commercially available graphene–PLA composite. This work is significant because it is the first demonstration that devices capable of fluid handling and electrochemical sensing can be produced in a single fabrication step using inexpensive equipment. We demonstrate the broad utility of this approach using a channel-flow configuration as an exemplary system for hydrodynamic electrochemistry. Unmodified devices were characterized using hydrodynamic electrochemistry, and behave according to the well-established Levich equation. We also characterized the fabrication reproducibility and found that the devices were within 3% RSD. The 3D-printed sensors we employed were subsequently modified by electroplating Au and used under flowing conditions to detect catechol, whose oxidation requires two electrons and two protons and is thus more challenging to analyze than the outer-sphere FcCH2OH. We envision these results will pave the way for the development of highly customized micro-total analysis systems that include embedded electrochemical sensors for a variety of redox-active analytes.
Methods of Photoelectrode Characterization with High Spatial and Temporal Resolution
Energy Environ. Sci.
Materials and photoelectrode architectures that are highly efficient, extremely stable, and made from low cost materials are required for commercially viable photoelectrochemical (PEC) water-splitting technology. A key challenge is the heterogeneous nature of real-world materials, which often possess spatial variation in their crystal structure, morphology, and/or composition at the nano-, micro-, or macro-scale. Different structures and compositions can have vastly different properties and can therefore strongly influence the overall performance of the photoelectrode through complex structure-property relationships. A complete understanding of photoelectrode materials would also involve elucidation of processes such as carrier collection and electrochemical charge transfer that occur at very fast time scales. We present herein an overview of a broad suite of experimental and computational tools that can be used to define the structure-property relationships of photoelectrode materials at small dimensions and on fast time scales. A major focus is on in situ scanning-probe measurement (SPM) techniques that possess the ability to measure differences in optical, electronic, catalytic, and physical properties with nano- or micro-scale spatial resolution. In situ ultrafast spectroscopic techniques, used to probe carrier dynamics involved with processes such as carrier generation, recombination, and interfacial charge transport, are also discussed. Complementing all of these experimental techniques are computational atomistic modeling tools, which can be invaluable for interpreting experimental results, aiding in materials discovery, and interrogating PEC processes at length and time scales not currently accessible by experiment. In addition to reviewing the basic capabilities of these experimental and computational techniques, we highlight key opportunities and limitations of applying these tools for the development of PEC materials.
Membraneless Electrolyzers for the Simultaneous Production of Acid, Base, Oxygen, and Hydrogen
Chemical Communications
This study investigates the use of membraneless electrolyzers based on angled mesh flow-through electrodes for the simultaneous production of acid and base (lye) from aqueous brine solutions. These electrolyte-agnostic flow cells are capable of producing a wide variety of acids and bases with precisely controlled pH using a simple cell design.
