2.1. Reagents and materials
HAuCl4·4H2O, H2PtCl4, H2PdCl4, N-hydroxysuccinimide (NHS), N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (EDC), N,N-Dimethylformamide (DMF), ascorbic BMY 7378 (C6H8O6, AA, reagent grade), propargyl amine (95%), folic acid (≥97%), CuSO4·5H2O, thionine (TH), H2O2, and 1-octanethiol were all purchased from Aladdin Industrial Corporation. 1-Azidoundecan-11-thiol (N3C11H22SH) was obtained from Sigma-Aldrich. All the chemicals were used as received without further purification. All solutions were prepared using Milli-Q water (≥18 M ohm cm in resistivity, Milli-Q, Millipore, Billerica, MA) as solvent. K-562 cell line was obtained from the Committee on Type Culture Collection of the Chinese Academy of Sciences.
Transmission electron microscopy (TEM) images were recorded on JEOL 2010 transmission electron microscope operating at an accelerating voltage of 120 kV. Scanning electron microscope (SEM) images were obtained using a QUANTA FEG 250 thermal field emission SEM (FEI Co., USA). X-ray photoelectron spectra (XPS) were measured by Thermofisher ESCALB 250 X-ray photoelectron spectrometer. The phase characterization was performed by X-ray diffraction(XRD) using D8 advance diffractometer system equipped with Cu Kα radiation (BrukerCo., Germany). Electrochemical impedance spectroscopy (EIS) was carried out on IM6x electrochemical station (Zahner, Germany). Electrochemical measurements were performed with CHI 760 (Shanghai CH Instruments, China) system. The electrodes consisted of a screen-printed Ag/AgCl reference electrode, a carbon counter electrode on the paper auxiliary zone and a screen-printed carbon working electrode on the paper sample zones.