Dual-emission carbon dots: Synthesis, applications, advances and challenges

Dual emission carbon dots (DE-CDs) have emerged as a transformative class of nanomaterials, offering distinct advantages over single-emission carbon dots (SE-CDs), including superior anti-interference capabilities, built-in self-calibration and broader full-width at half maximum (FWHM) emission spectra. This review comprehensively explores recent advancements in the synthesis of DE-CDs, detailing their physicochemical characteristics and elucidating key hypotheses underlying the formation of dual-emission peaks, such as the roles of core states, surface states, and quantum confinement effects. The diverse applications of DE-CDs are systematically analyzed, emphasizing their use in ratiometric sensing, bioimaging, biosensing, pH monitoring, moisture and water detection, and white light-emitting diodes (WLEDs). A comparative evaluation highlights their advantages and limitations relative to traditional fluorescence materials. Furthermore, recent progress in integrating DE-CDs into dye-sensitized solar cells (DSCs) and solar steam generation (SSG) devices is presented, underscoring their potential in renewable energy technologies. Finally, this review discusses the challenges and prospects for developing DE-CDs, including the need for scalable synthesis techniques, optimization of quantum yields for lighting applications, and enhanced understanding of dual-emission behavior mechanisms. Despite these challenges, DE-CDs hold immense promise for advancing technologies in sensing, bioimaging, lighting, and sustainable energy systems.