I am doing an aptamer-based sensing of heavy metals and I will be using gold nanoparticles (AuNPs) as the optical label. Part of the preparation of the aptamer-AuNP recognition label is that the stock AuNP solution should be purified. The purification procedure is based on the protocol reported by Alsager et al (2015) which involved the preparation of 1 part AuNP to 10 parts of water and then centrifugate at 12500 RPM for 15 minutes. To check the success of the purification step, zeta potential of the purified AuNP should be determined and compared to the zeta potential of stock AuNP. Based on the paper, zeta potential of the purified AuNPs should be lower than the stock AuNPs due to the reduction of citrate in the surface of the AuNPs. However, my results did not agreed to the results of he original paper. Instead of a lower zeta potential, the zeta potential of the purified AuNPs were higher than the stock.
Stock AuNPs= -47.7 mV
Purified AuNPs = -57.7 mV
We are currently troubleshooting the Malvern ZetaSizer Nano ZS instrument in our lab if the problem is on the instrument. But I am posting this question to get suggestions from the global experts. The original article is attached. Thank you for taking time to read this inquiry!
Zeta potential of nanoparticles is very dependent on the adsorption of water ions, other substances, the size of nanoparticles, compliance with the conditions of synthesis. To obtain the same potentials, all parameters must be matched. This is difficult to do in practice.
zeta potential is highly pH dependent.. check the pH and particle sizes.
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