Fig. 5From: Investigation of hollow mesoporous NiFe2O4 nanospheres fabricated via a template-free solvothermal route as pH-responsive drug delivery system for potential anticancer applicationXPS survey spectrum (a) and high-resolution XPS spectra of Fe 2p (b), Ni 2p (c), O 1Â s (d) of hollow mesoporous NiFe2O4 nanospheresBack to article page