A solventless thermolysis route to large-scale production of ultra-small hydrophilic and biocompatible magnetic ferrite nanocrystals and their application for efficient protein enrichment†
A green and one-step solventless thermolysis approach is developed for large-scale production of ultra-small magnetic ferrite nanocrystals with size down to 3.5 nm. By simply heating a mixed solid powder containing metal acetylacetonate and sodium citrate, a series of metal ferrite nanocrystals including Fe3O4, MnFe2O4, NiFe2O4 and CoFe2O4 are prepared. The nanocrystals exhibit both high hydrophilicity and good biocompatibility with uniform sizes that can be controlled by varying the ratio of metal acetylacetonate to sodium citrate, a green agent that is widely used as a food additive, a buffering regulator and an anticoagulant in blood transfusions. Thanks to the high hydrophilicity, the nanocrystals are demonstrated to be efficient draw solutes for protein enrichment with retained conformational structure based on an osmotically driven process. The green and one-step solventless thermolysis approach with advantages of minimal use of organic solvents and simplicity may be extended to fabrication of other ultra-small and hydrophilic nanoparticles with biocompatibility for a variety of applications.