One-step synthesis of sulfur quantum dots in the presence of primary, secondary, and tertiary amines

Quantum dots synthesized on the metal basis and the materials covering them can be immunogenic, which can lead to dangerous consequences for the research objects. It is possible to avoid these limitations by using metal-free quantum dots. Among the known non-metallic nanomaterials, sulfur quantum dots are of particular interest. Now the use of sulfur quantum dots as sensor systems is limited due to the absence of receptor groups in their structure. This problem can be solved by using compounds containing polyfunctional fragments as a passivation agent or base in the synthesis of quantum dots. In this study, we developed a method for obtaining sulfur quantum dots using primary and secondary amines. Using fluorescence spectroscopy, it was shown that the fluorescence intensity changes depending on the reaction time. Thus, in the case of a reaction time of 125 h, the maximum fluorescence values are observed for all the studied samples. The highest intensity among all the samples is characteristic of sulfur quantum dots based on pyrrolidine, which acts as a base. In this case, the lowest sizes of sulfur quantum dots were recorded (3 nm, polydispersity index = 0.28). The feasibility of using pyrrolidine as the main reagent for the synthesis of sulfur quantum dots has been revealed.