FIGURE 2.

The application of graphene and its derivatives in fluorescence sensing. (A) Fluorescence spectra corresponding to GO and GO treated with KOH and HNO₃; inset: the different electronic transitions (Li et al., 2012). (B) The pH-dependent photoluminescence of GO. (C) The intensities of photoluminescence at different wavelengths (λ = 683, 506, and 479 nm) and its corresponding pH value (Galande et al., 2011). (D) Fluorescence mechanism of GO (Cushing et al., 2014). (E) Tunable excitation-wavelength-dependent two-photon imaging. (F) Two-photon fluorescence imaging technique based on aptamer-modified GO and its application (Pramanik et al., 2014b). (G) High-sensitivity detection of dopamine by using GO as a fluorescence quencher (Chen et al., 2011). (H) MicroRNA (miRNA) detection based on GO and peptide nucleic acid (PNA) (Ryoo et al., 2013).