Selective and sensitive colorimetric determination of thebaine using modified gold nanoparticles

Gold nanoparticles (AuNPs) are considered highly stable metal nanoparticles flaunting several outstanding features including facile synthesis and surface modification, excellent biocompatibility and strong Surface Plasmon Resonance (SPR) in the visible region of the spectrum which make them the ideal candidate for naked-eye detection of analytes [1,2].Drug abuse is a major issue associated with a myriad of medical, social, and legal problems. To date, most of the analytical techniques employed for the determination of opioids and their metabolites in biological samples have involved the application of sophisticated and costly equipments such as GC–MS, HPLC, capillary electrophoresis (CE), and electrochemical analysis [3-5]. Herein, a simple and rapid colorimetric Thebaine (THE) sensor based on 2-amino-5-mercapto-1, 3, 4-thiadiazol (AMTD) functionalized gold nanoparticles (AuNPs-AMTD) was presented. This assay relied upon the distance-dependent optical properties of AuNPs, and the aggregation of AuNPs which was induced by the strong hydrogen bonding between AMTD and THE. The absorption peak is shifted from 520 to 630 nm which was accompanied by the color change from wine red to purple/blue. Under the optimized conditions, the colorimetric sensor exhibited linear response in the concentration range of 1.11 to 11.11 μmol L-1 THE with a low detection limit of 0.4 μmol L-1. Furthermore, we demonstrated the application of the present approach in human urine sample, which suggested its great potential for diagnostic and forensic purposes.