Colourimetric Detection of Tebuconazole in Aqueous Solution Based on an Unmodified Aptamer and the Aggregation of Gold Nanoparticles

This paper illustrates the establishment of a colourimetric method for detection of the fungicide tebuconazole (TEB) in aqueous samples based on an unmodified TEB-specific aptamer and gold nanoparticles (AuNPs). In the absence of TEB, the AuNPs are coated with a TEB-specific aptamer and then stably dispersed a NaCl solution of high concentration, leading to a red solution and producing a maximum UV absorption peak at 520 nm. In the presence of TEB, due to the specific high affinity between TEB and the TEB-specific aptamer, the aptamer combines with TEB to form stable compounds, causing the AuNPs to be exposed in the solution and aggregate. The aggregated AuNPs turn the solution from red to blue, presenting a maximum UV absorption peak at 650 nm. Therefore, the concentration of TEB in the system can be quantitatively detected through the changes in absorbance. This TEB selective colourimetric biosensor detects TEB over a linear concentration range of 20 to 400 nM (R = 0.99385) and has a limit of detection (LOD) of 4.13 nM. The average recovery of TEB is 94.9–104.8 % in the application of actual water samples with the relative standard deviations (RSD) ranging from 1.01 to 5.34 %. With considerable sensitivity and selectivity, this aptasensor indicates great potential for TEB detection in aqueous samples.