I am preparing gas sensors with NiO coral like nano structures (in the form of thin films/drop casted on IDE). I am getting good sensitivity for NO gas but the response is poor (around 41%) and the recovery time is also poor. The recovery rate is very slow. Please suggest me the possible modifications that I can do to improve the response and reduce the recovery time of the sensor. Please suggest me if doping is required to reduce the bandgap (3.4 eV for NiO) or formation of some p-n junctions is necessary. Please suggest the synthesis steps for the same.
Hi Sayan Dey,
If you want to enhance the sensing properties of NiO then make a composite of NiO with organic/inorganic maerials. Composites are reduces the individual drawbacks of single counterparts.
Doping is also a one more option. But, composites are better than doping. It is well known that , resistive kind of materials are more sutible for gas sensing application.
Doping is an option. But, composites are better than doping. make a composite of NiO with organic/inorganic materials.
Before giving a reasonable answer, I would like to ask a few questions: What is the NO concentration that you want to sense? What is your background gas (Air or Argon or any other)? What is your operating temperature? What do you mean by "sensitivity is good but response is poor"? What is the thickness of your NiO layer? How many IDEs electrodes do you have (mean how many fingers)? Are these electrodes on the top or bottom of sensing layer ? What is the electrode gap size between two consecutive electrodes?
I would suggest some options, but before that one has to know about all those answers.
Regards
i) Minimum concentration of NO: 1 ppm
ii) Background Gas: Air
iii) Operating temperature: Temperature can be increased from room temperature to 450 degrees centigrade.
iv) Thickness of NiO layer is roughly around 50 nm
v) It can detect the gas but Rg/Ra is not very high. It is around 0.41. By response, I meant this.
vi) My IDE has 2 electrodes at the bottom of the sensing layer.
vii) The distance between two electrodes is around 1.41 mm.
You may find your answer in:
Y. Chen, F. Xia, J. Z. Xiao, "Effects of ZnO Addition on Response of Nio Sensing Electrode for Mixed-Potential-Type Zirconia-Based NOx Sensor", Advanced Materials Research, Vol. 873, pp. 311-315, Dec. 2013
Hi Sayan,
Your sensing system seems to be OK.
My suggestion is to reduce the IDE gap size from 1.41 mm (1400 um) to 50-100 um, if you want to use the same material. Also, increase the number of fingers, e.g. 10 fingers (five each side). This will definitely increase sensor response along with reaction times.
In case, if you do not have such facility to decrease electrode gap size, then I would suggest to use some dopant as suggested by other members. Did you try to change the flow rate?
But I am sure by decreasing the gap size the gas sensing properties will definitely improve.
Regards,
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