Mechanistic Insights and Controlled Synthesis of Radioluminescent ZnSe Quantum Dots Using a Microfluidic Reactor

We describe the controlled colloidal synthesis and characterization of ZnSe quantum dots using a continuous-flow microfluidic reactor. A systematic investigation of the synthetic route reveals a possible two-stage pathway for ZnSe nanocrystal formation. The first stage corresponds to the formation of zinc selenide nuclei at low temperatures (160 degrees C), followed by the growth of ZnSe nanocrystals at higher temperatures (340 degrees C). The quantum dots exhibit sharp exciton absorption, with tunable emission spectra between 370 and 430 nm. The photoluminescence of ZnSe nanocrystals is characterized by narrow emission linewidths of 14-21 nm. For the first time, we report luminescent emission from ZnSe nanocrystals upon X-ray excitation, revealing that radioluminescence emission is associated to confined excitons, and that the radioluminescence intensity is a linear function of the fluence/dose rate of X-rays. The precise control of the synthesis of particles with uniform sizes and excellent optical properties associated with the microfluidic synthesis opens a new avenue for the controlled production of heavy-metal-free luminescent and radioluminescent nanocrystals in flow.