You could determine if the size of the four samples is the same, if it is not the same, it may be that depending on the size this displacement occurs.

Hi, Kamal. Thermodynamically your AgNPs tends to have a high surface area meaning high potential energy (small partical size). Potential energy likes to be as smallest as possible this phenomena calls Ostwald ripening: in this case small nanoparticals aggregate to bigger size reducing potential energy leading to thermodynamicaly stable particles (small surface area). Therefore your uvvis of AgNPs has shifted as different samples have different size of nano particles.

Dear Serhii I.Vasylevskyi :

I point out your mistakes>

“AgNPs tends to have a high surface area” - A large specific surface area

“ Potential energy” -surface energy of Gibbs

potential energy (small partical size)?

“small nanoparticals aggregate to bigger size reducing potential energy”- small nanoparticals aggregate to bigger size reducing surface energy of Gibbs

Read the glossary of terms and concepts on Colloid Chemistry in my profile

With best regards.

Yu. Mirgorod

Dear Kamal Mustafa,

I recommend the above mentioned answers. The shift in your study will be because of the different sizes of nanoparticles obtained. You can compare the size of the nanoparticles with the UV-vis spectrum and I am sure that you will get your answer.

Best of luck.