I treated the silver nanoparticle with acetylcholinestrase. data showed after 3 hours the maximum absorbance peak for nanoparticle-protein increased than blank one. in blank sample there is just nanoparticle.
Did the shape of the spectrum change ? Is the absorption maximum wavelength retained ?
If the acetylcholinesterase can complex silver (or interact with it), the molar extinction coefficient of species produced through this interaction might be significantly different than that of the pristine nanoparticles.
The increase in absorbance indicates that such a phenomenon took place and that this interaction actually promotes photon absorption by the system. Should a complex be formed, You can actually study its formation/dissociation constant using UV-Vis spectroscopy, as presented in the enclosed paper.
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thank all of you
we observed the maximum peak of treated sample just same as blank one. but there is a light peak in other wavelength. for example we had the maximum peak around 420nm and a light peak around 600nm. this light peak did not exist in blank one.
The second peak is probably from dimerization or polymerization of your particles. If two silver nanoparticles get bound together, that could explain the 600nm peak. If your signal broadens into a contiuum, you probably are getting nanoparticle aggregation, indicating your protein has sufficiently lowered the zeta potential of the nanoparticles as to induce aggregations.
thank you Adam. have you any reference? i need to prove this topic.
Whether the phenomenon at hand is aggregation or the formation of a complex, investigation of the behaviour (in this case, expressed by the UV-Vis absorbtion spectra) of your system at different concentrations (and concentration ratios) of the nanoparticles and acetylcholinesterase can be used to verify the hypothesis.
thank you Dr. Jarosz
you mean the intensity absorbance is because of more aggregation whether by nanoparticle aggregation or by nanoparticle-protein complex?
When discussing the increase of absorbance at 420nm, I would be leaning to the nanoparticle-protein complex hypothesis, however, such an effect can also occur as a result of aggregation and the formation of larger particles.
If we take the wavelengths of the two peaks into account, we get peak energies of 2.95 eV and 2.07 eV, respectively for the 420 nm and 600 nm peaks. The magnitude of this shift is similar to what is seen in case of aggregation (please see Fig.3 of the enclosed work), however, the question is, did the shape of the two peaks differ ? Does the shape of your spectra resemble the spectra presented in the paper ?
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i am appreciating you Dr. Jarosz
i attached an excel file that shows two nanoparticle-protein treatments
There are only 2 basic reasons for this.
(1) due to aggregation
(2) due to confinement of free electrons makes the silver NP an efficient sensing methods. That is why when you added protein to NP you observed the change in peak.
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