In Situ Synthesis of Gold Nanoclusters in Covalent Organic Frameworks with Enhanced Photodynamic Properties and Antibacterial Performance

Abstract

In this work, ultrasmall gold nanoclusters (AuNCs) have been in situ synthesized in nanopores of covalent organic framework (COF) nanoparticles, which exhibited enhanced fluorescence, improved photosensitizing capabilities, and promising antibacterial performance. A small organic molecule, 1-vinylimidazole (Vim), was diffused into the nanopores of imine-based COFs and served as a reducing agent and capping ligand for the in situ synthesis of ultrasmall AuNCs. The as-obtained AuNCs were homogeneously distributed throughout the COF nanoparticles whose fluorescence intensity was enhanced remarkably. Due to the efficient electron transfer between AuNCs and COFs and increased separation of photogenerated electron−hole pairs, the light-triggered reactive oxygen species (ROS) production of COFs was prominently enhanced by AuNCs. Moreover, the obtained nanocomposites exhibited an efficient photodynamic killing behavior on Escherichia coli under visible light exposure. Thus, we provide a facile strategy to prepare COF/AuNC nanocomposites for ROS-related applications.

In situ synthesis of chiral AuNCs with aggregation-induced emission using glutathione and ceria precursor nanosheets for glutathione biosensing

“…S2† reveals the good crystallinity of the AuNCs that were in situ -prepared from the oligomeric gold thiolated complexes. The crystalline structure of the AuNCs clearly shows a lattice fringe spacing of 0.23 nm, which is consistent with the face-centred cubic structure (fcc) of gold nanomaterials, 16,35 as shown in the HRTEM images (Fig. 3).…”

Covalent Organic Frameworks as Efficient Photoinitiators and Cross-Linkers To Fabricate Highly Stretchable Hydrogels

“…The synthetic routes and chemical structures of the two imine-linked COF nanoparticles are shown in Scheme . Schiff-base condensation between 1,3,5-tris­(4-aminophenyl)-benzene (TAPB) and 2,5-dimethoxyterephthaldehyde (DMTA) or 2,5-divinylterephthalaldehyde (DVTA) were carried out in acetonitrile at room temperature. , Driven by strong π–π stacking interactions, the formed 2D COF layers grew into rod-like crystallites and further self-assembled into a 3D structure . In order to acquire nanoscale COFs with uniform size, polyvinylpyrrolidone (PVP) was introduced into the reactions to regulate and stabilize the COF nanoparticles.…”

“…We assumed the photoinitiating mechanism of COFs involved the photogenerated charge pairs and radicals such as hydroxyl radicals ( · OH), as reported previously. , In order to visualize the charge separation and transfer, electron paramagnetic resonance (EPR) spectra of COFs were recorded in the dark and upon exposure to visible light with a 420 nm high-pass filter. The aqueous dispersions of the COF nanoparticles were thoroughly deoxygenated by Ar to avoid the possible sensitization route toward oxygen molecules . As shown in Figure a,b, both COF-OMe and COF-V displayed a narrow isotropic singlet with Lorentzian line shape at g = 2.004 under dark.…”

“…The COF nanoparticles were synthesized using the reported method in the literature. , Typically, TAPB (246 mg, 0.7 mmol), DMTA (213.5 mg, 1.1 mmol) or DVTA (205 mg, 1.1 mmol), and PVP (250 mg) were dissolved in 250 mL of acetonitrile, followed by the addition of acetic acid (1.25 mL). The mixture was magnetically stirred at 25 °C for 12 h, and the nanoparticles were collected by centrifugation and washed with acetonitrile three times.…”

“…The aqueous dispersions of the COF nanoparticles were thoroughly deoxygenated by Ar to avoid the possible sensitization route toward oxygen molecules. 30 As shown in Figure 4a,b, both COF-OMe and COF-V displayed a narrow isotropic singlet with Lorentzian line shape at g = 2.004 under dark. Upon irradiation by light for 8 min, the signals increased significantly, indicating that more electrons were excited from the valence band (VB) to the conduction band (CB).…”