Dear Vishnu-Sankar,

your coating of the nano (insulator) material should include some

1) corrosion (nano)materials in PBS solution,

and/or might have, also,

2) pin-holes (or scratches).

A hint: Select a manual-current mode (instead of the common auto-current mode) for this CV.

Vishnu Sankar

You can make some software fixing by increasing step potential. to reduce points and see the behaviour. You can also assure your connections to look for mis-connection

I have checked the connections multiple times and they were correct.. but even after making fresh electrolyte also this is showing noise

Try to measure

1) a Time series[1] of the (WE) Potential, and

2) get some hints for noise reduction[2], and/or

3) try, if possible, to measure the impedance[3] (EIS[4]), before, and after different nanomaterials' coatings.

1. See, figures 5C (and fig. 5D, 5E), in: 'Electrochemical current noise method to monitor carbon steel corrosion under mineral wool insulation' https://www.nature.com/articles/s41529-020-00144-3.pdf

2. See, figures 3,6 in: 'Transparent and flexible low noise graphene electrodes for simultaneous electrophysiology and neuroimaging' https://www.nature.com/articles/ncomms6259.pdf

3. See, figure 3, in: 'Degenerate Si as an Electrode Material for Electrochemical Biosensors' https://mtc.siu.edu/_common/documents/mtc/degenerate-si.pdf

4. 'EIS: Corrosion & Coatings' https://www.gamry.com/assets/Uploads/EISCorrosionCoatings.pdf

In electrohemistry, noise ideally needs to be removed t source since electrochemical devices are typically non-linear for most of the i-V characteristics and noise will be rectified leading to current offsets. It is possible that it is simply a coincidence that the nanoparticle modification happened before the noise increased. Do a quick Fourier transform and see what the dominant frequencies are- this could let you know if it is pick-up from the power supply- as this will be 50 Hz (UK and Europe, or 60 Hz US) and probably the odd harmonics, but make sure that the sampling frequency is as high as possible, but at least >100 Hz. Did you change the sampling frequency after the treatment? Your noise might previously have been aliased to very low frequencies and not seen. Also, what reference electrode are you using? If this is the one on the screen printed electrode, these are pretty terrible at the best of times, but some alteration in the surface chemistry could lead to increase Ref-solution impedance. Changes in contact resistance after the treatment is another possibility.There are some useful tips on noise in our paper "Lifting the lid on the potentiostat" and the electronic supplementary information shows real world examples: Physical Chemistry Chemical Physics (2021) 23 8300.