First dissolve PEG in deionized water ,then add your NP in the solution at a weight% of 1:100. Stirring for 24 hrs will do the job.

Thanks Sir. we are using iron oxide nanoparticles in toluene due to their cheaper cost than nanoparticles in water. Then please tell me how to proceed because I am not getting satisfactory materials for reference. If you have any then please share.

Toluene (200 mL), methanol (5 mL), (3-aminopropyl)trimethoxy silane (APTMS) (1.5 mL, 8 mmol), and SPIO (300 mM Fe, 25 mL in toluene) were mixed rigorously for 6 h under N2. The different temperature, room temperature and 808C, were used to investigate the influence on magnetization. PEG(400)- OTs (6 g, 8 mmol) or PEG(2000)-OTs (18 g, 8 mmol) in toluene (50 mL) was added and stirred for 12 h, then added NH4OH (28%, 4 mL) to maintain pH value 9. The precipitate formed was isolated by centrifugation at 3500 rpm, and supernatant was removed from the precipitate by decantation. This procedure was repeated three times to remove excess APTMS, PEG(400)-OTs, or PEG(2000)-OTs in the suspension

Thanks Mam... If I have to bring final solution of PEG conjugated nanoparticles from toluene to into water, then what procedures should I follow or which organic solvent I have to use in making the solution free of toluene. Please tell the exact procedure in detail.

Further I have to conjugate the pegylated nanoparticles to antibodies. Whether the toluene will affect the procedure of EDC NHS chemistry or not and also its harmful residual effects in living system.

centrifugation with water to remove the toluene

Thanks Mam