I am working on synthesis of silver nanoparticles (AgNPs) using the condition below. I would like to use this AgNPs for further application; however, the leftover silver nitrate (AgNO3) in the solution is not ideal for the application. When I measured the silver ion concentration the next day from the reaction using a silver ion probe after calibration (99% linearity based on the calibration), the remaining AgNO3 concentration was 30 - 40 uM, which seemed to be quite high. I've re-worked on the synthesis using higher concentration of sodium borohydride (37.5 and 50 uM), but this resulted in fading of bright yellow color to almost colorless after 1-2 hrs. It seems like excess borohydride promoted dissolution of AgNPs.
Is there anyway to modify the scheme so the AgNO3 will be consumed more ? Does the rate of dropwise addition of sodium borohydride have effect on consumption of AgNO3 ?
(1) DI water (volume needed to make up 15 mL was added)
(2) 100 uM Trisodium citrate
(3) 100 uM Silver Nitrate
(4) 25 uM Sodium borohydride (always freshly prepared)
*These reagents were added in the order of 1 to 4.
**These concentrations are final concentrations after all the reagents are added.
From my experience, you can rise temperature above 170C and hold forever 1hr ,again addition of AgNO3 should be drop wise titrated manner near about 1/2 hour, then I think you're able to get completely AgNP.
Dear Nobuyuki ..
Based on my experience on preparing silver nano particles from silver nitrate, the longer of the reaction period,.... the more silver nitrate consumption will be and the nano particles will be more .... I hope I have been given useful information .. with wishes for success
Mr. Mishra,
Did you mean 170F instead? I could try thermally grown AgNP synthesis. Thank you.
Dr. Jasim,
Thank you for your answer. In fact, leaving the AgNP solution for 1 week did not have significant difference in the UV-Vis absorbance or the peak-width.
Dr. Rawle,
Thank you for your input. I actually used more NaBH4 as it was shown in the description of my question. I think these papers below explained me what was happening in my system. The unreacted NaBH4 was affecting the AgNPs.
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