Ultrasensitive colorimetric detection of tetracyclines based on in-situ growth of gold nanoflowers.

A colorimetric method based on in-situ generation of gold nanoflowers for the detection of tetracyclines (TCs) was proposed. We found that gold nanoflowers could be formed in the HAuCl4-NH2OH redox reaction directly without the addition of small-sized gold nanoparticles (Au NPs) as seeds when an alkaline borax buffer solution was employed as the reaction medium. Interestingly, the shape and size of the generated gold nanoflowers were regulated with TC. Briefly, large flower-like gold nanoparticles were formed with a low concentration of TC while small spherical gold nanoparticles were generated with a high concentration of TC. The generated gold nanoflowers exhibited different surface plasmon absorption (SPR) properties. Thus, a simple and rapid colorimetric method was established for the detection of TC antibiotics. This method exhibited high sensitivity for the detection of TC, oxytetracycline (OTC), and doxycycline (DC) with detection limits of 2.23 nM, 1.19 nM, and 5.81 nM, respectively. The proposed colorimetric method was applied to the determination of TC in both milk samples and water samples.