Concentrated solar irradiation protocols for the efficient synthesis of tri-color emissive carbon dots and photophysical studies

In contrast to conventional nanomaterials or organic dyes, carbon dots possess a variety of appealing properties including chemical inertness and easy manipulation and they can be dispersed in water. Herein, the use of a concentrated solar irradiation sintering strategy for the rapid and efficient assembly of carbon dots (CDs) has been reported for the first time. This novel alternative pathway effectively uses a renewable source and the process is feasible and environmentally sustainable. Three kinds of CDs were obtained, which demonstrate blue, green and red luminescence. Highly efficient blue-emitting CDs with quantum yield as high as 81% have been realized. The blue and red carbon dots give rise to excitation-independent emission peaks at 443 and 592 nm, respectively; however, the green CDs feature a continuous shift and the evolution of emission curves varies from 480 to 538 nm. By regulating the composition and ratios of these tri-color carbon dots, the emission band generates peaks from blue to red light, which cover almost the entire visible light range. Upon a single ultra-violet excitation at 365 nm, a white-light emission with CIE coordinates of (0.28, 0.33) was detected and the signal was very close to pure white light (0.33, 0.33). This study introduces a new method for fabricating low-cost nanoparticles as potential phosphors for light-emitting uses.