Rational Synthesis of Solid-State Ultraviolet B Emitting Carbon Dots via Acetic Acid-Promoted Fractions of sp(3) Bonding Strategy

Carbon dots (CDs) have received tremendous attention for their excellent photoluminescence (PL) properties. However, it remains a great challenge to obtain CDs with ultraviolet (UV, 200-400 nm) emission in solid state, which requires strict control of the CDs structure and overcoming the aggregation-caused quenching (ACQ). Herein, a new sp(3) compartmentalization strategy is developed to meet these requirements, by employing acetic acid to promote fractions of sp(3) bonding during the synthesis of CDs. It markedly decreases the size of sp(2) conjugating units in the CDs, and shifts PL emission to the ultraviolet B (UVB) region (lambda(max) = 308 nm). Moreover, sp(2) domains are well spatially compartmentalized by sp(3) domains and the ACQ effect is minimized, enabling the high quantum yield in solid state (20.2%, lambda(ex) = 265 nm) with a narrow bandwidth of 24 nm and environmental robustness. The solid-state UVB emissive CDs are highly desired for application in photonic devices. Hence, a demo of UVB light-emitting diodes is fabricated for plant lighting, leading to a 29% increase of ascorbic acid content in the basil. Overall, a rational and efficient way to construct solid UVB-CDs phosphors for wide applications is provided.