How to functionalize silver nanoparticles with thiolated PEG? I found a couple of papers doing this, but when I mix the Ag nanoparticles with thiolated PEG, the silver particles seem to be dissolving since the LSPR disappear. Any suggestions is highly appreciated!
The loss of colour of AgNP could be, in general, due to agglomeration of NPs. However, thiol PEGs are supposed to bring two NPs close to each other. Please make sure that salt like NaCl is not present in your PEG solution.
It could be as simple as adding Thiolated PEG to the to the AgNP solution. However, molar ratio (AgNP to PEG)is important for complete coverage, which should be optimized by taking micro molar PEG solutions. The min conc of PEG required can be determined by monitoring the hydrodynamic diameter of AgNP or UV-vis spectral shift.
In our laboratory practice we calculate "surface of colloid" - first estimation is taken from size and concentration of silver nanoparticles. In our case colloids are relatively well monodisperse with round shape of nanoparticles what allow for reasonable surface estimation. From our experience 1-2 PEG-SH molecules on each nm2 is OK. Too high concentration of PEG-SH sometimes destabilise our colloids.
After modification hydrodynamic radius (measured by DLS) should be few nm bigger (it depends on size of PEG chain).
There is one more important point. In silver colloids is always small amount of free Ag+ kation in solution, which may react with -SH group and in the worst situation thiols will not react with silver. Is good to know what is concentration of silver cations in colloids.
I hope that some of this information will be useful for your laboratory work.
@ Celichowski Thanks very much for your suggestions! It is very helpful!
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