Band-Selective Coupling-Induced Enhancement of Two-Photon Photoluminescence in Gold Nanocubes and Its Application as Turn-on Fluorescent Probes for Cysteine and Glutathione

We have demonstrated that cysteine and glutathione induced edge-to-edge coupling of gold nanocubes (Au NCs) caused a band-selective enhancement of two-photon photoluminescence (TPPL). The photoluminescence intensity of the X-band of Au NCs was found to be enhanced up to 60-fold and 46-fold upon addition of cysteine and glutathione, respectively, while the intensity of L-band remained almost unchanged. This band-selective enhancement behavior is totally different from the previously observed aggregation enhanced TPPL of spherical metal nanoparticles (NPs). The band-selective enhancement was ascribed to preferential enhancement of the X-band emission through resonant coupling with longitudinal surface plasmon resonance (SPR) band of the Au NCs assembly. This phenomenon was utilized to develop a new two-photon fluorescence turn-on sensing platform for detection of cysteine and glutathione. This method displayed high sensitivity and excellent selectivity over the other 19 amino acids. Together with the advant...