A SPR aptamer sensor for mercury based on AuNPs@NaYF₄:Yb,Tm,Gd upconversion luminescent nanoparticles

A new aptamer-based surface plasmon resonance (SPR) system has been designed to detect Hg²⁺ that utilizes near-infrared (NIR)-to-NIR gold nanoparticle coated NaYF₄:Yb,Tm,Gd up-conversion nanoparticles (AuNPs@NaYF₄:Yb,Tm,Gd UCNPs) as probes. The AuNPs@NaYF₄:Yb,Tm,Gd UCNPs were prepared and excited by near-infrared light (980 nm) which emitted at a near-infrared wavelength (808 nm) using an inexpensive infrared continuous wave laser diode. The AuNPs@NaYF₄:Yb,Tm,Gd UCNPs were conjugated with Hg²⁺ aptamers. In the presence of Hg²⁺, the AuNPs@NaYF₄:Yb,Tm,Gd UCNPs were brought into close proximity because of the formation of T-Hg²⁺-T base pairs. Then the luminescence enhanced because of the plasmon resonance effects. Based on this, a new SPR system was developed for the detection of Hg²⁺ that had high sensitivity and selectivity in the NIR region. This method was successfully applied to detect Hg²⁺ concentration in real samples.