Editing Magnetic beads Preparation Methods (section)

== Fe3O4/PMG/IDA−Ni2+ Nanoparticles ==

[https://www.nature.com/articles/srep41741 https://www.nature.com/articles/srep41741]

γ-Methacryloxypropyltrimethoxy-silane (MPS)

Glycidyl methacrylate (GMA)

2, 2′-Azobis (2-methylpropionitrile) (AIBN)

The Fe3O4 particles with a core size around 200 nm were synthesized through a modified solvothermal reaction. Typically, FeCl3·6H2O (1.350 g), NH4Ac (3.854 g) and trisodium citrate dihydrate (0.400 g) were dissolved in ethylene glycol (70 mL). The mixture was stirred vigorously for 1 h at 160 °C to form a homogeneous black solution, and then transferred into a Teflon-lined stainless-steel autoclave (100 mL capacity). The autoclave was heated at 200 °C and maintained for 16 h, and then it was cooled to room temperature. The black product was washed with ethanol and separated from the solvent by using a magnet. The cycle of washing and magnetic separation was repeated for several times. The final product was dispersed in ethanol for further use.

Modification of the Fe3O4 with MPS<br/>The modification of Fe3O4 with MPS was achieved by adding 40 mL of ethanol, 10 mL of deionized water, 1.5 mL of NH3·H2O, and 0.6 g of MPS into the Fe3O4 particles ethanol suspension and vigorously stirring the mixture for 24 h at 70 °C. The obtained product was separated by using a magnet and washed with ethanol to remove excess MPS. The resultant Fe3O4-MPS nanoparticles were dried in a vacuum oven at 40 °C until they reached a constant weight.

Synthesis of Fe3O4/PMG Core/Shell Nanoparticles<br/>Coating a PMG layer onto Fe3O4-MPS nanoparticles was executed by the distillation-precipitation polymerization (DPP) of GMA, with MBA as the cross-linker and AIBN as the initiator, in acetonitrile. Typically, Fe3O4-MPS seed nanoparticles (50 mg) were dispersed in acetonitrile (40 mL) in a dried single-necked flask (100 mL capacity) under ultrasonic condition for 3 min. Then a mixture of GMA (150 mg), MBA (150 mg), and AIBN (6 mg) was added to the flask to initiate the polymerization. The flask, submerged in a heating oil bath, was attached to a fractionating column, Liebig condenser, and a receiver. The reaction mixture was heated from room temperature to the boiling state within 30 min and the reaction was ended after acetonitrile (20 mL) was distilled from the reaction mixture within 1 h. The obtained Fe3O4/PMG nanoparticles were collected by magnetic separation and washed with ethanol and water repeatedly.

Preparation of Fe3O4/PMG/IDA-Ni2+ Nanoparticles<br/>IDA (0.33 g) and NaOH (0.2 g) were dissolved in 20 mL of deionized water under stirring. 2 M NaOH solutions were used to adjust the pH of the solution. Then Fe3O4/PMG nanoparticles (50 mg) were added to the solution, and the mixture was stirred vigorously for 12 h at 80 °C. The obtained Fe3O4/PMG/IDA nanoparticles were separated by a magnet and washed by ethanol and water for several times. Subsequently, 50 mg of Fe3O4/PMG/IDA nanoparticles was added to a 10 mL of 0.1 M NiCl2 solution and stirred for 2 h at room temperature. The product was separated by a magnet from the solution and washed several times with water. The resultant Fe3O4/PMG/IDA-Ni2+ nanoparticles were dried in a vacuum oven at 40 °C.