Covalent Functionalization of FeCo/Graphitic Shell Nanocrystals via 1,3‐Dipolar Cycloaddition

Abstract Covalently functionalized water‐soluble FeCo/graphitic shell nanocrystals (f−FeCo/GC NCs) were synthesized via 1,3‐dipolar cycloaddition of azomethine ylides generated in situ from sarcosine and glucose. The FeCo core has superparamagnetic properties at room temperature, and the graphitic shell exhibits near‐infrared optical absorbance. Acetylation of the hydroxyl groups on the f−FeCo/GC NCs gives doubly functionalized FeCo/GC (ff−FeCo/GC) NCs that are soluble only in organic solvents such as ethyl acetate. The f−FeCo/GC NCs were shown to be excellent T₁ or T₂ MRI contrast agents. Especially, due to the hydrophilic and compact surface functionalization, f−FeCo/GC NCs exhibit a doubled r₁ relaxivity and half r₂/r₁ ratio compared to those of the non‐covalently PL‐PEG‐functionalized FeCo/GC NCs. This work shows not only the first synthesis of covalently functionalized highly water‐soluble metal NCs coated with a single‐layered graphitic shell, but also for the first time the MR enhancing properties of the covalently functionalized magnetic NCs.