Photoassisted photoluminescence fine-tuning of gold nanodots through free radical-mediated ligand-assembly

Abstract

In this study, we have developed a simple photoassisted ligand assembly to fine-tune the photoluminescence (PL) of (11-mercaptoundecyl)-N,N,N-trimethylammonium bromide-capped gold nanodots (11-MUTAB-Au NDs). The 11-MUTAB-Au NDs (size: ca. 1.8 nm), obtained from the reaction of gold nanoparticles (ca. 3 nm) and 11-MUTAB, exhibited weak, near-infrared (NIR) PL at 700 nm with a quantum yield (QY) of 0.37% upon excitation at 365 nm. The PL QY of the Au NDs increased to 11.43% after reaction with 11-mercaptoundecanoic acid (11-MUA) for 30 min under ultraviolet (UV) light, which was accompanied by a PL wavelength shift to the green region (∼520 nm). UV-light irradiation accelerates 11-MUA assembly on the 11-MUTABAu NDs (11-MUA/11-MUTAB-Au NDs) through a radical-mediated reaction. Furthermore, the PL wavelength of the 11-MUA/11-MUTAB-Au NDs can be switched to 640 nm via cysteamine under UV-light irradiation. We propose that the PL of the Au NDs with NIR and visible emissions was originally from the surface thiol-Au complexes and the Au core, respectively. These dramatically different optical properties of the Au NDs were due to variation in the surface ligands, as well as the densities and surface oxidant states of the surface Au atoms/ions. These effects can be controlled by assembling surface thiol ligands and accelerated by UV irradiation.

Self-Assembled Chiral Gold Supramolecules with Efficient Laser Absorption for Enantiospecific Recognition of Carnitine

“…Recently, some studies have revealed the charge, density, and rigidity of the Au­(I)–thiolate shell plays a crucial role in determining the QY of Au–thiolate NCs. Those Au–thiolate NCs having highly dense thiolated ligands and QY > 10% mostly are emitted at 600–700 nm, ,,, consistent with our Au NCs/–[Cys–Au­(I)] n – supramolecules (630 nm). Compared to the employed organic solvent, mixed ligands, ligand exchange, host–guest recognition, ultrasound- or light irradiation-treatment to obtain dense thiolated ligands on Au NCs for boosting the QY of Au NCs, ,,, our one-pot synthesis of highly photoluminescent Au NCs/–[Cys–Au­(I)] n – supramolecules is relatively simple and straightforward.…”

“…Those Au–thiolate NCs having highly dense thiolated ligands and QY > 10% mostly are emitted at 600–700 nm, ,,, consistent with our Au NCs/–[Cys–Au­(I)] n – supramolecules (630 nm). Compared to the employed organic solvent, mixed ligands, ligand exchange, host–guest recognition, ultrasound- or light irradiation-treatment to obtain dense thiolated ligands on Au NCs for boosting the QY of Au NCs, ,,, our one-pot synthesis of highly photoluminescent Au NCs/–[Cys–Au­(I)] n – supramolecules is relatively simple and straightforward. In addition, good batch-to-batch reproducibility (relative standard deviations (RSD) < 5% from 5 batches) was obtained on the preparation of highly photoluminescent Au NCs/–[Cys–Au­(I)] n – supramolecules on the basis of their PL intensity.…”

“…Those Au−thiolate NCs having highly dense thiolated ligands and QY > 10% mostly are emitted at 600−700 nm, 22,50,57,58 consistent with our Au NCs/−[Cys−Au(I)] n − supramolecules (630 nm). Compared to the employed organic solvent, mixed ligands, ligand exchange, host−guest recognition, ultrasoundor light irradiation-treatment to obtain dense thiolated ligands on Au NCs for boosting the QY of Au NCs, 22,50,57,58 S11A). It has been reported that D-carnitine and L-carnitine form a more favorable configuration with L-Cys and D-Cys, respectively, through hydrogen bonding and a stronger electrostatic interaction compared to that of D-carnitine/D-Cys and L-carnitine/L-Cys.…”

A pH‐Triggered Synthesis of Blue‐Emitting Au Nanoclusters and Their Luminescence Enhancement in a Metallohydrogel: Selective Detection of Pb2+ through Luminescence Quenching

“…1 were used to evaluate the radiative lifetime (τ rad ) which explains the lifetime component in the absence of nonradiative decay pathway. Technically, B ‐NCs and B ‐gel should yield similar τ rad if the QY enhancement is solely exclusive of collision quenchers ,. In our case, we observed a significant difference in the τ rad value (Table ).…”

Isomerization-induced enhancement of luminescence in Au28(SR)20 nanoclusters

“…[1][2][3][4][5][6][7][8][9][10][11][12] Luminescent metal nanoclusters are of particular interest owing to their unique properties, including their high stability, low toxicity, large Stokes shi, and long luminescence lifetime, and thus such nanoclusters have attracted signicant research interest in recent years. [13][14][15][16][17][18][19][20][21][22][23][24] A major effort in current research on luminescent nanoclusters protected by thiolates is focused on the development of effective strategies to enhance their luminescence. To improve the quantum yield of photoluminescence (PL), it is of paramount importance to understand the PL mechanism and, in particular, the structural basis.…”