Development of a highly sensitive immuno-type fluorescence sensor utilising rare earth element-doped upconversion nanomaterials and graphene oxide for the detection of fenitrothion residues in food

• An immune-fluorescence sensor using UCNPs and GO detected fenitrothion. • Core-shell NaYF 4 :Yb,Er@NaYF 4 were employed to enhance sensor sensitivity. • The sensor has excellent specificity and anti-interference performance. • The sensor quantitatively detects fenitrothion in real agricultural samples. Fenitrothion is an organophosphorus insecticide, and its residues in agricultural goods pose significant risks to human health. Therefore, prompt and precise identification of fenitrothion residues in agricultural commodities is of significant importance. This study employed rare earth element-doped upconversion nanomaterials (REEs-UCNPs) and graphene oxide (GO) to develop an immune-based fluorescence sensor for fenitrothion detection. The nanomaterials NaYF 4 :Yb,Er@NaYF 4 were synthesised via the solvothermal method, with polyacrylic acid modified on their surface through ligand exchange. NaYF 4 :Yb,Er@NaYF 4 was conjugated with a monoclonal antibody using a glutaraldehyde cross-linking method, while GO was conjugated with the fenitrothion antigen. The precise interaction between the antigen and the antibody resulted in the binding of NaYF 4 :Yb,Er@NaYF 4 to GO. When exposed to an excitation wavelength of 980 nm, GO could absorb the fluorescence emitted by NaYF 4 :Yb,Er@NaYF 4 at 542 nm through the fluorescence resonance energy transfer mechanism. The fenitrothion pesticide could competitively bind to the monoclonal antibody with the antigen, thereby restoring the system’s fluorescence. Under ideal conditions, the sensor’s detection limit for fenitrothion was 0.081 ng/mL, with a linear range of 0.1–100 ng/mL. The spiking recoveries of fenitrothion in seven real samples varied from 91.79 % to 105.43 %, with relative standard deviations of 1.81–10.63 %. This study effectively developed a sensitive, accurate and specific immuno-type fluorescence sensor for the efficient and precise quantitative detection of fenitrothion in agricultural materials.