Mn²⁺-doped NaYF₄:Yb/Er upconversion nanoparticles with amplified electrogenerated chemiluminescence for tumor biomarker detection

Chemiluminescence was used as an excitation light source to construct a universal photoelectrochemical platform based on Mn²⁺-doped NaYF₄:Yb/Er upconversion nanoparticles, which greatly improves the electrochemiluminescence intensity and offers more stable cathodic signals compared to pure NaYF₄:Yb/Er NPs. Here, we report for the first time the ECL behaviors of Mn²⁺-doped NaYF₄:Yb/Er NPs, which were synthesized via a facile strategy. Mn²⁺doping resulted in a 4-fold ECL intensity enhancement of NaYF₄:Yb/Er. The characteristics of Mn²⁺-doped NaYF₄:Yb/Er nanocomposites were obtained using transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDS), and fluorescence spectra. After all the results had indicated that NaYF₄:Yb/Er upconversion nanoparticles were successfully doped with Mn²⁺, the electrochemiluminescence platform was built. The as-prepared NaYF₄:Yb/Er NPs were rendered water-soluble and then employed as ECL emitters for carcinoembryonic antigen (CEA) determination. The results indicated that the modified electrode can be used to determine CEA without interference from non-specific proteins, with a low detection limit of 5.2 pg mL^-1. The biosensor can also be used for quantification of the CEA concentration in real samples.