Figure 16.

The influence of solvent and concentration on the red shift of CDs. (A) The solvent-dependent photoluminescence is regarded as a dipole-induced surface electronic state change. As the solvent polarity increases, the dipole moment affects the surface electronic structure and reduces the energy gap, resulting in the red shift of the fluorescence emission wavelength. Adapted with permission from ²⁶⁶. Copyright 2017, Royal Society of Chemistry. (B) Mechanism of PL emission tuning with concentrations. Concentration-induced morphological changes influence energy traps associated with surface states, which was a mechanism of CDs with excitation-dependent PL properties and red shift. Adapted with permission from ²⁶⁸. Copyright 2017, Royal Society of Chemistry. (C) Schematic illustration of Si-CDs dispersed in an ionogel at high concentrations. Adapted with permission from ²⁶⁹. Copyright 2014, American Chemical Society. (D) CDs with an emission color ranging from blue to red, which is measured by the thickness of the down-conversion layers and CDs doping concentration. Adapted with permission from ²⁷⁰. Copyright 2015, Royal Society of Chemistry.