Superior thermal cycling stability of a carbon dots@NaBiF 4 nanocomposite: facile synthesis and surface configurations.

Carbon dots (CDs), emerging as promising materials for optoelectronic and biomedical applications, are widely investigated due to their distinct merits of facile preparation, biocompatibility, and environment-friendliness. Here, a unique strategy based on surface engineering is proposed to modulate the photoluminescence (PL) of CDs in both aqueous solution and the solid state with good thermal cycling stability. For the typical blue emissive CD solution derived from citric acid and ethylenediamine, an intense green emission can be induced by adding Bi 3+ due to the strong coordination ability of Bi 3+ ions with carboxyl groups on the surface of CDs. A super facile synthesis approach (ultrafast at room-temperature) has been developed to fabricate the CDs@NaBiF 4 nanocomposite, whose chemical structure and composition have been investigated in detail. For the solid nanocomposite, it not only preserves the strong blue emission from the intrinsic core state of CDs, but exhibits a new green emission from the surface state. The solid-state CDs@NaBiF 4 nanocomposite exhibits good thermal stability and high resistance to thermal degradation under blue light excitation. The strategy via metal ion-mediated PL of CDs represents a new approach to control the optical properties of CDs, and provides more opportunities in solid-state lighting and biomedical applications.