Electrochemical measurements were carried out on a CHI 660D
electrochemical workstation (CH Instruments, Chenhua Corp.,
Shanghai, China). The electrochemical cell contained a threeelectrode
system where the bare or modified glassy carbon
electrode was used as a working electrode, platinum wire as an
auxiliary electrode, and a saturated calomel electrode (SCE) as reference
electrode. All potentials were measured and reported versus
the SCE. The test solutions were 5 mL PBS. Transmission electronmicroscopy
(TEM) was carried out on a TECNAI 10 (PHILIPS FEI
Co., Holland). A scanning transmission electron microscope (STEM)
equipped with an energy dispersive X-ray (EDX) detector was