*2.1. Materials*

*N*-(3-dimethylaminopropyl)-*N*'-ethylcarbodiimide hydrochloride (EDC), chitosan, and divinylbenzene (DVB) were purchased from Sigma-Aldrich (Shanghai, China). *<sup>N</sup>*,*<sup>N</sup>*-dimethylacetamide (DMAC), triethylamine, NaBH4, sodium dodecyl sulphate (SDS), and potassium tellurite (K2TeO3) were purchased from Sinopharm Chemical Reagent Co., Ltd. (Tianjin, China). Trimethylolpropane trimethacrylate (TRIM), *<sup>N</sup>*,*<sup>N</sup>*-dimethylaniline (DMA), and benzoyl peroxide (BPO) were purchased from Aladdin Industrial Co., Ltd. (Shanghai, China). Thioglycolic acid (TGA) and acryloyl chloride were purchased from Alfa Aesar (Tianjin, China), and Cd(CH3COO)2·2H2O was purchased from TianJin Kemel Chemical Reagent Co., Ltd. (Tianjin, China). Before use, the DVB was passed through an aluminum oxide column to remove the stabilizer.
