Upconversion Nanoparticle-Based Luminescent Aptasensor on a Porous Silicon Substrate for Isocarbophos Detection.

Rare earth-doped upconversion nanoparticles (UCNPs) can emit upconversion luminescence under infrared light excitation and have been widely applied in the field of biosensing. In this study, upconversion nanoparticles were loaded onto porous silicon (PSi), and the detection of isocarbophos concentration was realized by virtue of nucleic acid aptamers. Firstly, the PSi was prepared by electrochemical etching and further functionalized. Nucleic acid aptamers were immobilized on the inner wall of PSi. Subsequently, the aptamer complementary strands labeled with UCNPs hybridized with the immobilized nucleic acid aptamers, enabling the indirect attachment of UCNPs to the inner wall of PSi. Then, isocarbophos solutions with different concentrations were added. The upconversion fluorescence images of samples before and after biological reaction were collected by an image acquisition device. The variation in average gray value of the images was obtained by image processing software, thereby achieving the quantitative detection of isocarbophos concentration. The limit of detection of this method for isocarbophos is 0.73 µg/L, which indicates that the proposed method can realize low-cost, high-sensitivity, and convenient biological detection of isocarbophos, with a fast and equipment-free signal readout.