“…Due to abundant surface properties of magnetic materials, it is readily to introduce/modify other components onto the surface of magnetic core and form functional shell(s) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. The exposed shell makes itself sensitive and reactive to the surroundings, thus realizes applications such as sensing [6,7,10,11,16], adsorption [12,13], catalysis [14,15], therapy [9], and so on. On the other hand, the shell cooperates with the magnetic core, even generates synergistic effect [9,12,13].…”