Luminescence Enhancement of a Gold Nanocluster Hydrogel Facilitated by Water for Erasable Water Writing and Visual Solvent Differentiation

Abstract

Gold nanoclusters (AuNCs) with an ultrasmall size have attracted enormous interest due to their unique luminescence properties. However, manipulating/improving the luminescence of AuNCs through a convenient method is still challenging. Herein, effective enhancement of emission by simply using water is reported for the AuNCs stabilized by 4,6-diamino-2-pyrimidinethiol (DPT). The DPT-AuNCs could aggregate into a hydrogel in aqueous systems, accompanied with luminescence enhancement (the quantum yield increased from 0.36 to 3.07%). However, the xerogel obtained by freeze-drying was non-luminescent. Addition of water to the xerogel could trigger the emission again. Differential scanning calorimetry, X-ray diffraction, and theoretical calculations reveal that water-bridged hydrogen bonds play crucial roles in the emission of DPT-AuNCs. Furthermore, the water-sensitive luminescence of DPT-AuNCs was applied for developing erasable water writing materials and for visual differentiation of solvents (e.g., protonic organic solvents, non-protonic organic solvents, and water). This study offers a green, cost-effective, and convenient strategy for enhancing the luminescence properties of AuNCs, reveals the crucial role of water molecules in the emission of AuNCs, and presents an application in optoelectronic functional materials.

Temperature-Responsive Ratiometric Au Nanoclusters (NCs) Fabricated through α-Cyclodextrin-Protected Au NCs and Au@GSH NCs

“…The abundant hydrogen bonds formed by water molecules and the hydroxyl group of Au@α-CD NCs enhanced their luminescence. 44,45 The sensitivities of the luminescence intensities of Au@α-CD NCs to oxygen (O 2 ) and argon (Ar) are measured in Figure S4. Their luminescence intensities were basically unaffected by Ar and O 2 , combined with their short nanosecond luminescence lifetime, demonstrating that the blue-emissive Au@α-CD NCs belonged to fluorescent Au NCs.…”

“…The Au@α-CD NC solid powder basically did not emit light, and their luminescence gradually enhanced with the addition of solvent molecules (H 2 O) and decreased with increasing concentration of Au@α-CD NCs, which might be caused by the solvent effect. The abundant hydrogen bonds formed by water molecules and the hydroxyl group of Au@α-CD NCs enhanced their luminescence. , The sensitivities of the luminescence intensities of Au@α-CD NCs to oxygen (O 2 ) and argon (Ar) are measured in Figure S4. Their luminescence intensities were basically unaffected by Ar and O 2 , combined with their short nanosecond luminescence lifetime, demonstrating that the blue-emissive Au@α-CD NCs belonged to fluorescent Au NCs.…”

Polymer-Enabled Assembly of Au Nanoclusters with Luminescence Enhancement and Macroscopic Chirality

“…DPT-AuNCs were prepared according to our published literature. , In a typical process, an equal volume of aqueous solution of HAuCl 4 (1 mL of 10 mg/mL) was added to the prepared DPT (1 mL of 70 mM) in a clean glass vial. The mixed solution was vortexed at room temperature for 3 min until it turned light yellow, and then incubated at 20 °C for 24 h. The obtained DPT-AuNCs were diluted with ultrapure water to one fifth of its concentration for the following experiments.…”