Reagents Tellurium powder Te was obtained from Alfa

2.1. Reagents
Tellurium powder (Te, 99.999%) was obtained from Alfa Aesar Chemical Reagent Co. Ltd. Sodium hydroxide (NaOH), sodium borohydride (NaBH4) and mercaptopropionic ha peptide (MPA) were obtained from Sinopharm Chemical Reagent Co. Ltd. Thiolated β-cyclodextrin (β-CD) was purchased from ZhiYuan Biotechnology Co., Ltd. Benzo[a]pyrene (BaP) was obtained from J&k Scientific Ltd. All other chemicals were of analytical reagent grade and used as received. Doubly distilled water was used in all experiments.
2.2. Apparatus
The ECL signal was detected and recorded by IFFM-E flow injection chemiluminescence analyzer (Xi'an Remax, China). Unless noted otherwise, the voltage of the PMT was biased at 800 V. Electrochemical measurements were carried out with a Resource partitioning CHI 760C electrochemical workstation (Chenhua, Shanghai) using three-electrode system with indium tin oxide glass (ITO, area: 0.4 cm2) as the working electrode, a Pt wire as the counter electrode and an Ag/AgCl (saturated KCl) as the reference electrode. The UV–vis spectra and photoluminescence (PL) spectra were measured on U-3010 UV–vis spectrophotometer (Hitachi, Japan) and F-4500 spectrofluorometer (Hitachi, Japan), respectively. The dynamic light scattering (DLS) data of the β-CD-MPA-CdTe QDs with and without BaP were obtained on Malvern Zetasizer Nano instrument.