Fungal in Situ Assembly Gives Novel Properties to CdS_xSe_{1- x} Quantum Dots for Sensitive Label-Free Detection of Chloramphenicol

Quantum dots (QDs) are attracting significant attention for the development of sensitive detection methods because of their unique optical properties. Biosynthetic QDs using organisms is a promising alternative route to chemical synthesis because it is a simple and eco-friendly process. Herein, we developed a straightforward and green system for the biological assembly of CdS_xSe_1-x QDs by Phomopsis sp. XP-8 within 6 h, a more efficient approach than those reported in other organisms. The QDs were shown to have a CdS_0.75Se_0.25@oligopeptide transporter structure, and the production process was shown to be strongly influenced by intracellular glutathione content. The QDs were monodispersed with a uniform spherical shape of 3.22 ± 0.07 nm in diameter. They exhibited good water solubility and excellent fluorescence properties. The QDs could be extracted and used directly as a sensitive chloramphenicol (CAP) probe via static fluorescence quenching in the linear range from 3.13 to 500 μg/L with a detection limit of 0.89 μg/L. The detection method was highly selective for CAP with minimal interference from other antibiotics and was used to successfully detect CAP in milk samples. Overall, this work has great significance for the development of a fast and simple QD synthesis system via biological assembly.