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Can you troubleshoot my procedure for SECM approach curves?
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Minhsan Nguyen
Can you troubleshoot my procedure for SECM approach curves?
Hi, I have consult with the person who installed the micro-positioning software and we have discussed on the codes that would stop the SECM tip on command and 5 micrometre above the substrate. but I did not go to 5 micrometre but set it to go to 10 micrometre above the substrate. But I would stop the SECM tip when I got 75% more current than the current at the bulk. Now, Everytime I do a CV in the solution prior to doing the approach curve, I would get a quasi-perfect 's'-shape CV which means that the tip is not damaged. But now the only thing that I need to resolve is that my electrode seems to pick up extra current even before polarising the tip. I will not get OCP. But I will try to resolve it. Thank you for your support and advice Luca and Nilotpal.
Hi, I have consult with the person who installed the micro-positioning software and we have discussed on the codes that would stop the SECM tip on command and 5 micrometre above the substrate. but I did not go to 5 micrometre but set it to go to 10 micrometre above the substrate. But I would stop the SECM tip when I got 75% more current than the current at the bulk. Now, Everytime I do a CV in the solution prior to doing the approach curve, I would get a quasi-perfect 's'-shape CV which means that the tip is not damaged. But now the only thing that I need to resolve is that my electrode seems to pick up extra current even before polarising the tip. I will not get OCP. But I will try to resolve it. Thank you for your support and advice Luca and Nilotpal.
I'm sorry for answering you late. I normally seek help from core experimentalist for getting the data. The only means that I can suggest is that go for a Non contact device where you won't come across such problem, but it depends on the availability of the machine and expertise. Keep updating your problem and I'll return back to you after asking some experts here.
I'm sorry for answering you late. I normally seek help from core experimentalist for getting the data. The only means that I can suggest is that go for a Non contact device where you won't come across such problem, but it depends on the availability of the machine and expertise. Keep updating your problem and I'll return back to you after asking some experts here.
First of all, I would like to say thank you for your replies. The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system. The micropositioner that I am using right now does not receive commands from the electroanalytical software that I am using. It also does not respond to stop command which had made it more difficult to run the experiment. But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish). The micropositioner that I am using is a homemade micropositioner from Physik instrument run by a software called PI Mikromove and the electroanalytical software that I am using is NOVA. I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks. Two sides of the sample was clamped by means of a rubber pad in order to hold it in place but this does not guarantee that the sample is laid flat at the bottom of the cell. But the tilt might have been just a small order of magnitude.
First of all, I would like to say thank you for your replies. The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system. The micropositioner that I am using right now does not receive commands from the electroanalytical software that I am using. It also does not respond to stop command which had made it more difficult to run the experiment. But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish). The micropositioner that I am using is a homemade micropositioner from Physik instrument run by a software called PI Mikromove and the electroanalytical software that I am using is NOVA. I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks. Two sides of the sample was clamped by means of a rubber pad in order to hold it in place but this does not guarantee that the sample is laid flat at the bottom of the cell. But the tilt might have been just a small order of magnitude.
But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish) yes. I took a look at the site of Pi mikromove. It is not convenient since it is not interfaced with the analytical software, but it looks like it has everything you need to start/stop it at will. As I outlined above, you can do that manually based on the current you read from NOVA. keep the approach speed sufficiently low. also, if your electrode (active region) is > 2micrometers, that distance from the surface is quite low. The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system. I am not familiar with iridate. what i can tell you is that besides being stable it should also be fast. Where fast includes both the electrode/mediator and substrate/mediator reactions if you are looking for positive feedback. Generally speaking, particularly with a semiconductor, you can use positive or negative feedback by varying substrate bias. Depending on the sloppiness of the mediator/subtrate reaction, this could help get better approach curves. I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks. I d be satisfied with your RG.. you can control the integrity of the tip by cyclic voltammetry. deviations from the ideal sigmoid shape you should obtain with a microelectrode are easy to spot. if you are unsure about tilt, do approach curves at opposite ends of the substrate, fit them and compare the distance you get. Remember to use the appropriate function for the fitting. Once you are able to quantify the tilt you might be able to understand whether you can used it like that or whether you have to modify the sample holder. try to get a hold of this book: Scanning Electrochemical Microscopy, Second Edition Published: April 16, 2012 by CRC Press || Editor(s):Allen J. Bard, Michael V. Mirkin it might help clarify some of your doubts.
But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish) yes. I took a look at the site of Pi mikromove. It is not convenient since it is not interfaced with the analytical software, but it looks like it has everything you need to start/stop it at will. As I outlined above, you can do that manually based on the current you read from NOVA. keep the approach speed sufficiently low. also, if your electrode (active region) is > 2micrometers, that distance from the surface is quite low. The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system. I am not familiar with iridate. what i can tell you is that besides being stable it should also be fast. Where fast includes both the electrode/mediator and substrate/mediator reactions if you are looking for positive feedback. Generally speaking, particularly with a semiconductor, you can use positive or negative feedback by varying substrate bias. Depending on the sloppiness of the mediator/subtrate reaction, this could help get better approach curves. I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks. I d be satisfied with your RG.. you can control the integrity of the tip by cyclic voltammetry. deviations from the ideal sigmoid shape you should obtain with a microelectrode are easy to spot. if you are unsure about tilt, do approach curves at opposite ends of the substrate, fit them and compare the distance you get. Remember to use the appropriate function for the fitting. Once you are able to quantify the tilt you might be able to understand whether you can used it like that or whether you have to modify the sample holder. try to get a hold of this book: Scanning Electrochemical Microscopy, Second Edition Published: April 16, 2012 by CRC Press || Editor(s):Allen J. Bard, Michael V. Mirkin it might help clarify some of your doubts.
you sort of partly answered your question. you should make sure your electrode has no cracks (it can give you large and unstable current, especially if used as a pick-axe) and is flat and clean. you can do that with a cyclic voltammetry in the bulk and by examining the electrode before each experiment under a suitable microscope depending on electrode size. also you should make sure your substrate is not titled. If you know your substrate is tilted, then you should not do any experiments before you resolve the issue; or if the substrate is tilted by design you should use particularly slow scan rates and constant current mode. ---generally you have two ways to approach the substrate. the software of your instrument should allow you to set a threshold for the current when you do an approach curve i.e. it should allow you to say "stop when the current reaches 75%" of the bulk value. The instrument should automatically shift to the piezo motor and reduce approach speed as the current starts to vary. in this way you do not know how far you are until you fit the approach curve. if for some reason the software for your instrument does not allow you to do that you can do it manually. 1. write down bulk current 2. calculate desired percentage 3. stop electrode manually at desired current. p.s. approach the surface slowly. in specific circumstances you can put the electrode in contact with the surface and then move it up as much as you wish. whether you can do it or not depends on the nature of the substrate and electrode as well as electrode size and requires that the substrate and electrode are absolutely not tilted. last but not least you can vary the feedback by applying a bias to the substrate, especially since you are dealing with a semiconductor. how much and whether you can do it depends on the specific experiment you are trying to run. all of this assuming that you are using a suitable mediator and mediator concentration.
you sort of partly answered your question. you should make sure your electrode has no cracks (it can give you large and unstable current, especially if used as a pick-axe) and is flat and clean. you can do that with a cyclic voltammetry in the bulk and by examining the electrode before each experiment under a suitable microscope depending on electrode size. also you should make sure your substrate is not titled. If you know your substrate is tilted, then you should not do any experiments before you resolve the issue; or if the substrate is tilted by design you should use particularly slow scan rates and constant current mode. ---generally you have two ways to approach the substrate. the software of your instrument should allow you to set a threshold for the current when you do an approach curve i.e. it should allow you to say "stop when the current reaches 75%" of the bulk value. The instrument should automatically shift to the piezo motor and reduce approach speed as the current starts to vary. in this way you do not know how far you are until you fit the approach curve. if for some reason the software for your instrument does not allow you to do that you can do it manually. 1. write down bulk current 2. calculate desired percentage 3. stop electrode manually at desired current. p.s. approach the surface slowly. in specific circumstances you can put the electrode in contact with the surface and then move it up as much as you wish. whether you can do it or not depends on the nature of the substrate and electrode as well as electrode size and requires that the substrate and electrode are absolutely not tilted. last but not least you can vary the feedback by applying a bias to the substrate, especially since you are dealing with a semiconductor. how much and whether you can do it depends on the specific experiment you are trying to run. all of this assuming that you are using a suitable mediator and mediator concentration.
Hi,
I have consult with the person who installed the micro-positioning software and we have discussed on the codes that would stop the SECM tip on command and 5 micrometre above the substrate. but I did not go to 5 micrometre but set it to go to 10 micrometre above the substrate. But I would stop the SECM tip when I got 75% more current than the current at the bulk. Now, Everytime I do a CV in the solution prior to doing the approach curve, I would get a quasi-perfect 's'-shape CV which means that the tip is not damaged.
But now the only thing that I need to resolve is that my electrode seems to pick up extra current even before polarising the tip. I will not get OCP. But I will try to resolve it.
Thank you for your support and advice Luca and Nilotpal.
Hi,
I have consult with the person who installed the micro-positioning software and we have discussed on the codes that would stop the SECM tip on command and 5 micrometre above the substrate. but I did not go to 5 micrometre but set it to go to 10 micrometre above the substrate. But I would stop the SECM tip when I got 75% more current than the current at the bulk. Now, Everytime I do a CV in the solution prior to doing the approach curve, I would get a quasi-perfect 's'-shape CV which means that the tip is not damaged.
But now the only thing that I need to resolve is that my electrode seems to pick up extra current even before polarising the tip. I will not get OCP. But I will try to resolve it.
Thank you for your support and advice Luca and Nilotpal.
More
VOTE
I'm sorry for answering you late. I normally seek help from core experimentalist for getting the data. The only means that I can suggest is that go for a Non contact device where you won't come across such problem, but it depends on the availability of the machine and expertise. Keep updating your problem and I'll return back to you after asking some experts here.
I'm sorry for answering you late. I normally seek help from core experimentalist for getting the data. The only means that I can suggest is that go for a Non contact device where you won't come across such problem, but it depends on the availability of the machine and expertise. Keep updating your problem and I'll return back to you after asking some experts here.
More
VOTE
First of all, I would like to say thank you for your replies.
The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system.
The micropositioner that I am using right now does not receive commands from the electroanalytical software that I am using. It also does not respond to stop command which had made it more difficult to run the experiment. But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish). The micropositioner that I am using is a homemade micropositioner from Physik instrument run by a software called PI Mikromove and the electroanalytical software that I am using is NOVA.
I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks.
Two sides of the sample was clamped by means of a rubber pad in order to hold it in place but this does not guarantee that the sample is laid flat at the bottom of the cell. But the tilt might have been just a small order of magnitude.
First of all, I would like to say thank you for your replies.
The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system.
The micropositioner that I am using right now does not receive commands from the electroanalytical software that I am using. It also does not respond to stop command which had made it more difficult to run the experiment. But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish). The micropositioner that I am using is a homemade micropositioner from Physik instrument run by a software called PI Mikromove and the electroanalytical software that I am using is NOVA.
I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks.
Two sides of the sample was clamped by means of a rubber pad in order to hold it in place but this does not guarantee that the sample is laid flat at the bottom of the cell. But the tilt might have been just a small order of magnitude.
More
VOTE
But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish)
yes. I took a look at the site of Pi mikromove. It is not convenient since it is not interfaced with the analytical software, but it looks like it has everything you need to start/stop it at will. As I outlined above, you can do that manually based on the current you read from NOVA. keep the approach speed sufficiently low.
also, if your electrode (active region) is > 2micrometers, that distance from the surface is quite low.
The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system.
I am not familiar with iridate. what i can tell you is that besides being stable it should also be fast. Where fast includes both the electrode/mediator and substrate/mediator reactions if you are looking for positive feedback. Generally speaking, particularly with a semiconductor, you can use positive or negative feedback by varying substrate bias. Depending on the sloppiness of the mediator/subtrate reaction, this could help get better approach curves.
I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks.
I d be satisfied with your RG.. you can control the integrity of the tip by cyclic voltammetry. deviations from the ideal sigmoid shape you should obtain with a microelectrode are easy to spot.
if you are unsure about tilt, do approach curves at opposite ends of the substrate, fit them and compare the distance you get. Remember to use the appropriate function for the fitting. Once you are able to quantify the tilt you might be able to understand whether you can used it like that or whether you have to modify the sample holder.
try to get a hold of this book:
Scanning Electrochemical Microscopy, Second Edition
Published: April 16, 2012 by CRC Press || Editor(s):Allen J. Bard, Michael V. Mirkin
it might help clarify some of your doubts.
But I could give command the micropositioner to stop before it touches the surface of the sample (2 micrometer-ish)
yes. I took a look at the site of Pi mikromove. It is not convenient since it is not interfaced with the analytical software, but it looks like it has everything you need to start/stop it at will. As I outlined above, you can do that manually based on the current you read from NOVA. keep the approach speed sufficiently low.
also, if your electrode (active region) is > 2micrometers, that distance from the surface is quite low.
The mediator that I am using is 1 mM potassium hexachloroiridate (III) with 0.5 M KCl considering that it is a very stable and an outer-sphere redox system.
I am not familiar with iridate. what i can tell you is that besides being stable it should also be fast. Where fast includes both the electrode/mediator and substrate/mediator reactions if you are looking for positive feedback. Generally speaking, particularly with a semiconductor, you can use positive or negative feedback by varying substrate bias. Depending on the sloppiness of the mediator/subtrate reaction, this could help get better approach curves.
I managed to make my SECM tip to be really small with the RG of about 3. would it be helpful if I make it bigger but not more than RG 10? so that I can still fit the data with the theoretical current. because having a really small RG made it hard to tell if the surface of the tip is really flat and has no cracks.
I d be satisfied with your RG.. you can control the integrity of the tip by cyclic voltammetry. deviations from the ideal sigmoid shape you should obtain with a microelectrode are easy to spot.
if you are unsure about tilt, do approach curves at opposite ends of the substrate, fit them and compare the distance you get. Remember to use the appropriate function for the fitting. Once you are able to quantify the tilt you might be able to understand whether you can used it like that or whether you have to modify the sample holder.
try to get a hold of this book:
Scanning Electrochemical Microscopy, Second Edition
Published: April 16, 2012 by CRC Press || Editor(s):Allen J. Bard, Michael V. Mirkin
it might help clarify some of your doubts.
More
VOTE
you sort of partly answered your question.
you should make sure your electrode has no cracks (it can give you large and unstable current, especially if used as a pick-axe) and is flat and clean. you can do that with a cyclic voltammetry in the bulk and by examining the electrode before each experiment under a suitable microscope depending on electrode size.
also you should make sure your substrate is not titled. If you know your substrate is tilted, then you should not do any experiments before you resolve the issue; or if the substrate is tilted by design you should use particularly slow scan rates and constant current mode.
---generally you have two ways to approach the substrate. the software of your instrument should allow you to set a threshold for the current when you do an approach curve i.e. it should allow you to say "stop when the current reaches 75%" of the bulk value. The instrument should automatically shift to the piezo motor and reduce approach speed as the current starts to vary. in this way you do not know how far you are until you fit the approach curve. if for some reason the software for your instrument does not allow you to do that you can do it manually.
1. write down bulk current 2. calculate desired percentage 3. stop electrode manually at desired current. p.s. approach the surface slowly.
in specific circumstances you can put the electrode in contact with the surface and then move it up as much as you wish. whether you can do it or not depends on the nature of the substrate and electrode as well as electrode size and requires that the substrate and electrode are absolutely not tilted.
last but not least you can vary the feedback by applying a bias to the substrate, especially since you are dealing with a semiconductor. how much and whether you can do it depends on the specific experiment you are trying to run.
all of this assuming that you are using a suitable mediator and mediator concentration.
you sort of partly answered your question.
you should make sure your electrode has no cracks (it can give you large and unstable current, especially if used as a pick-axe) and is flat and clean. you can do that with a cyclic voltammetry in the bulk and by examining the electrode before each experiment under a suitable microscope depending on electrode size.
also you should make sure your substrate is not titled. If you know your substrate is tilted, then you should not do any experiments before you resolve the issue; or if the substrate is tilted by design you should use particularly slow scan rates and constant current mode.
---generally you have two ways to approach the substrate. the software of your instrument should allow you to set a threshold for the current when you do an approach curve i.e. it should allow you to say "stop when the current reaches 75%" of the bulk value. The instrument should automatically shift to the piezo motor and reduce approach speed as the current starts to vary. in this way you do not know how far you are until you fit the approach curve. if for some reason the software for your instrument does not allow you to do that you can do it manually.
1. write down bulk current 2. calculate desired percentage 3. stop electrode manually at desired current. p.s. approach the surface slowly.
in specific circumstances you can put the electrode in contact with the surface and then move it up as much as you wish. whether you can do it or not depends on the nature of the substrate and electrode as well as electrode size and requires that the substrate and electrode are absolutely not tilted.
last but not least you can vary the feedback by applying a bias to the substrate, especially since you are dealing with a semiconductor. how much and whether you can do it depends on the specific experiment you are trying to run.
all of this assuming that you are using a suitable mediator and mediator concentration.
More
VOTE
Dear Saiful ,
I as such could not help you that much but Luca indeed helped. Keep Updating as it helps the research work.
All the best
Dear Saiful ,
I as such could not help you that much but Luca indeed helped. Keep Updating as it helps the research work.
All the best
More
VOTE
Alright. Thank you so much. I will try the method that you have suggested first and get back to you guys. Hopefully the issues will be resolved soon.
Alright. Thank you so much. I will try the method that you have suggested first and get back to you guys. Hopefully the issues will be resolved soon.
More
VOTE