Photoswitchable NIR‐Emitting Gold Nanoparticles

Abstract

Photo-switching of the NIR emission of gold nanoparticles (GNP) upon photo-isomerization of azobenzenel igands,b ound to the surface,i sd emonstrated. Photophysical results confirm the occurrence of an excitation energy transfer process from the ligands to the GNP that produces sensitized NIR emission. Because of this process,the excitation efficiency of the gold core,u pon excitation of the ligands,i s muchh igher for the trans form than for the cis one,a nd t!c photo-isomerization causes ar elevant decrease of the GNP NIR emission. As ac onsequence,p hoto-isomerization can be monitored by ratiometric detection of the NIR emission upon dual excitation. The photo-isomerization process was followed in real-time through the simultaneous detection of absorbance and luminescence changes using ad edicated setup.S urprisingly,the photo-isomerization rate of the ligands,bound to the GNP surface,was the same as measured for the chromophores in solution. This outcome demonstrated that excitation energy transfer to gold assists photo-isomerization, rather than competing with it. These results pave the road to the development of new,NIR-emitting,stimuli-responsive nanomaterials for theranostics.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under http://dx.

Towards Ultra‐Bright Gold Nanoclusters

“…More recently, we proposed a different strategy to turn on/off the PL of Au 144 NCs using as organic sensitizer a photo‐switchable azobenzene derivative (Figure ) . The conversion of the trans form of the ligand into the cis one took place almost quantitatively (> 95 %) with a quantum yield identical to the one measured for the same molecule free in solution (upon irradiation at 360 nm).…”

“…In order to improve this feature, our and other groups proposed the design of hybrid structures that combine the PL properties of Au NCs with the optical properties of organic dyes in order to enhance the brightness of the inorganic emitters. A considerable improvement of brightness can in fact be achieved by introducing ligands able to efficiently adsorb light (chromophores) and to transfer the excitation energy to the emitting gold core , …”

“…Such contributions, owing to sensitization, are lost upon PI in cA covered NPs (right, cA‐GNP, OFF state). Reprinted from ref …”

pH-Driven Reversible Assembly and Disassembly of Colloidal Gold Nanoparticles

“…Low-dimensional plasmonic nanoparticle assemblies with new optical properties have recently attracted considerable attention because of the near-field coupling between adjacent particles (Liu D. et al, 2018 ; Li and Yin, 2019 ; Li et al, 2020a ). The ideal way is the reversible assembly of such plasmonic nanostructures, which could enable dynamic tuning of the surface plasmon coupling by responding the external stimuli, and therefore by taking advantage of the ultrasensitive gap-dependent properties of plasmonic coupling, they have great promises for applications such as colorimetric sensors, bio- and chemical detection, and therapeutics (Bonacchi et al, 2016 ; Pillai et al, 2016 ; Liu L. et al, 2018 ; Zhou et al, 2021 ). Recent studies have demonstrated the reversible assembly by controlling the nanoparticle separation via various methods, for example, by modulating solvent composition to change the ionic strength of the solution, adding moisture, thermo-, photo-, magnetical-, and pH-responsive ligands, or reversible linking molecules (such as DNA) (Liu et al, 2012 ; Liu L. et al, 2019 ; Ding et al, 2016 ; Fan et al, 2016 ; He et al, 2016 , 2019 ; Grzelczak et al, 2019 ; Li et al, 2020b ; Severoni et al, 2020 ).…”

Synthesis, Purification, and Characterization of Negatively Charged Gold Nanoparticles for Cation Sensing

“…Over the years, PGNPs covered with the most diverse functional groups have been synthesized and studied. 2 For example, crown ethers, 3 mono-and polysaccharides, 4 nucleic acids, 5,6 peptides, 7,8 chromophores, 9 catalysts, 10,11 and charged headgroups have been used 12−15 (Figure 1). One of the reasons that prompted the realization of such a diverse variety of structures is the observation that the coating layer has a micelle-like structure (Figure 2).…”