Figure 3: Absorption and PL spectra of SNPs, GQDs, and SNPs/GQDs hybrid.

(a) Absorption spectra of SNPs, GQDs, and SNPs/GQDs hybrid. The inset shows photographs of the three samples emitting light with different colors under ambient condition. (b) PL spectra of SNPs, GQDs, and SNPs/GQDs hybrid, excited at 325 nm. The inset describes the FRET effect responsible for the PL of SNPs/GQDs hybrid. (c) Excitation-wavelength-dependent PL spectra of GQDs, measured at 414 nm. (d) Excitation-wavelength-dependent PL peak shifts of GQDs and SNPs/GQDs hybrid. No energy transfer occurs from SNPs to GQDs at λ > 380 nm, but for ≤380 nm, the peak wavelength of SNPs/GQDs hybrid increases with decreasing λ, indicating the energy transfer from SNPs to GQDs.