I am synthesizing silver nanoparticles for biosensing of pathogenic bacteria. I am looking for an easy way to calculate the concentration of these particles for further further bioconjugation.
yes you can but for that you have to draw the linearity plot then and then only you can because there is many metthods to synthesize AgNp and in diff conc. So as you change the method of synthesis/conc. of Ag metal you have to again plot the graph than and only than you can calculate....
If understanding correctly your question, I suggest to use the absorption coefficient for colloidal quantum dots (QDs) from which one can extract concentration of QDs. The method is described in http://www.sciencedirect.com/science/article/pii/S0009261414006678 (http://arxiv.org/abs/1408.4972) for semiconductor QDs (see Eqs.(5, 7, 8), and Eq.(S30)). For metallic QDs within a similar treatment, it would be necessary to obtain the intrinsic absorption coefficient of metallic QDs. For this issue I suggest: http://fy.chalmers.se/~hellsing/publications/cm5_13_004.pdf
Better to check the concentration of AgNPs by ICP-OES/AAS.
Otherway, you need to prepare a standard curve with known concentration of silver nanoparticles using UV-visible spectra. Then consequently you can determine the silver concentration of your unknown sample.
As suggested in the previous answer, it is better to use ICP or you could go for atomic absorption spectroscopy (AAS). To use the UV-Vis method for calculating the concentration of Ag NPs, you have to be absolutely sure that they are of the same size. Or else the spectrum would show plasmon resonance peaks at different wavelengths and you would not be able calculate accurately.
I recently measured the Ag concentration using ICP-AES after synthesis of AgNP using microalgae. I used NaCl solution to precipitate unreacted Ag+ as AgCl and then measured the stable AgNP in the supernatant. Here is the article (it has detailed method). ICP-MS would give you more accurate results though.
https://www.mdpi.com/1420-3049/24/1/98
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