Surface Regulation Towards Stimuli‐Responsive Luminescence of Ultrasmall Thiolated Gold Nanoparticles for Ratiometric Imaging

Abstract

The surface chemistry of the ultrasmall thiolated gold nanoparticles (AuNPs, < 3.0 nm) plays key roles in both governing the intrinsic emission and establishing interfaces surrounded by various amine‐containing biomolecules in the biomedical applications such as imaging, targeting, and diagnostics. However, a fundamental understanding of the surface ligand's role in the stimuli‐responsive emissions of AuNPs toward the amine molecules is currently lacking. Here, through investigation of the thiolate surface and exotic amine structures, it is discovered that the nucleophilic amines tend to closely bind the electrophilic gold surface, generating a high‐energy stimuli‐responsive emission from the low‐energy intrinsically emitting AuNPs. Both the intrinsic and stimuli‐responsive emissions show a unique amine concentration‐dependent ratiometric pattern for quantitative assessments of important biogenic amines in the biological samples. This discovery opens a new pathway to the design of stimuli‐responsive AuNPs, and would promote more experimental and theoretical research on the application‐driven surface engineering for advanced biological applications.

Atomic Force Microscopy and Molecular Dynamics Simulations for Study of Lignin Solution Self‐Assembly Mechanisms in Organic–Aqueous Solvent Mixtures

“…Generally,s uccessful solvation makes EHL well-dissolved in solvent SI because contact of EHL molecules is prevented by the solvation layer.Conversely,once the solvation effect disappears or weakens, aggregation of lignin takes place, owing to attractive forces includingh ydrogen-bonding, p-p interaction, and hydrophobic forces. [32][33][34][35] To better understand dissolutiona nd aggregation processes, AFM was employedt oq uantitatively measuret he interactions betweenE HL molecules in different solvents.…”

Gold Nanoclusters for Bacterial Detection and Infection Therapy

“…For example, Au NCs do not possess surface plasmon resonance (SPR) absorption in the visible region but exhibit apparent fluorescence emission in the near-infrared (NIR) to visible region (Zheng Y. et al, 2017). In addition to ultrasmall size, many studies have also revealed that the optical properties of Au NCs highly depend on their structures, oxidation states, and surface ligands as well as environmental parameters such as temperature, pH, and ionic strength (Zheng Y. et al, 2017;Chen et al, 2019). As a bridge between single Au atom and plasmonic NPs, Au NCs have received increasing attention in many fields, including bacterial detection described in the following sections.…”

“…As a bridge between single Au atom and plasmonic NPs, Au NCs have received increasing attention in many fields, including bacterial detection described in the following sections. Up to now, several reviews have been dedicated to the ultrasmall Au NCs (Luo et al, 2014;Jin et al, 2016;Zheng Y. et al, 2017;Chen et al, 2019).…”

“…Gold-based NCs have intrinsic advantages such as facile syntheses, extremely large surface area, excellent biocompatibility, strong photoluminescence, high photostability, and easy functionalization with other biomolecules. Benefits from these excellent physicochemical properties, Au NCs have great promise in biomedical applications, such as sensing, imaging, and diseases treatment (Chen L. Y. et al, 2015;Zheng Y. et al, 2017;Hu et al, 2018;Chen et al, 2019). The antibacterial activity of Au NCs has been also innovatively explored over the past few years (Zheng K. et al, 2017;Zheng et al, 2018a,c;Xie et al, 2018).…”

Molecular reactivity of thiolate-protected noble metal nanoclusters: synthesis, self-assembly, and applications

“…explorations have shown that the adsorption and subsequent activation of O 2 on the surface of metal NCs is crucial in the aerobic oxidation reaction catalysed by metal NCs, 40,43 and the development of sensors is highly dependent on chemical adsorption or reaction of analytes with metal NCs. [44][45][46][47] Recent mechanistic discoveries also suggest that the growth and functionalization of metal NCs depends on their molecular interactions/reactions with reactive molecular species, including reducing agents, [48][49][50][51] metal salts, 52,53 SR ligands, [54][55][56][57] M(I)-SR/M(II)-SR complexes, [58][59][60][61][62] and metal NCs. 63,64 Moreover, continuous developments in mass spectrometry, X-ray crystallography, X-ray absorption ne structure (XAFS) analysis, and theoretical simulations of noble metal NCs have enabled researchers to understand the pathways and dynamics of the above-mentioned reactions/interactions at the unprecedented molecular and atomic levels.…”