Luminescent Gold Nanocluster-Decorated Polymeric Hybrid Particles with Assembly-Induced Emission

Abstract

Ultrasmall gold atom clusters (<2 nm in diameter) or gold nanoclusters exhibit emergent photonic properties (near-infrared absorption and emission) compared to larger plasmonic gold particles because of the significant quantization of their conduction band. Although single gold nanocluster properties and applications are being increasingly investigated, little is still known about their behavior and properties when assembled into suprastructures, and even fewer studies are investigating their use for biomedical applications. Here, a simple synthetic pathway combines gold nanoclusters with thermosensitive diblock copolymers of poly(ethylene glycol) (PEG) and poly(N-isopropylacrylamide) (PNIPAm) to form a new class of gold-polymer, micelle-forming, hybrid nanoparticle. The nanohybrids’ design is uniquely centered on enabling the temperature-dependent self-assembly of gold nanoclusters into the hydrophobic cores of micelles. This nonbulk assembly not only preserves but also enhances the attractive near-infrared photonics of the gold nanoclusters by significantly increasing their native fluorescent signal. In parallel to the fundamental insights into gold nanocluster ordering and assembly, the gold-polymer nanohybrids also demonstrated great potential as fluorescent live-imaging probes in vitro. This innovative material design based on the temperature-dependent, self-assembly of gold nanoclusters within a polymeric micelle’s core shows great promise toward bioassays, nanosensors, and nanomedicine.

The synthesis of switch-off fluorescent water-stable copper nanocluster Hg2+ sensors via a simple one-pot approach by an in situ metal reduction strategy in the presence of a thiolated polymer ligand template

“…The reduction in the spacing between the emitting cores hampers and even reverses the natural decrease in the fluorescence intensity that arises from heating. 50 The same fluorescence emission responses to the temperature and pH of the medium were observed for all synthesized hybrids and are in full agreement with our previous research relating to the functionalization of other types of fluorescent NPs with these kinds of multithiolated polymers. 27,53 For practical applications it is important to study the photo-/chemical stabilities of the new hybrid CuNCs to assess the degree of protection provided to the CuNCs by the polymeric coverage.…”

Luminescent gold nanoclusters for bioimaging applications

“…The AIE phenomenon has been observed in several organic compounds of low molecular weight and in polymers [73]. The aggregation-induced luminescence of NCs has been achieved either using solvent-induced aggregation or addition of additives such as ionic polymers, proteins or peptides [74][75][76]. Recently, Dichiarante et al reported NIR-luminescent AuNCs bearing superfluorinated (SF) ligands with strong emission at 1050 nm with a quantum yield of 12% [77].…”

Thermo-Sensitive Nanomaterials: Recent Advance in Synthesis and Biomedical Applications

“…Zhang et al reported the preparation of Au nanorods (Au NR) and PNIPAm composites with fast thermal/optical response and high heating rate by a traditional electrospinning technique presenting potential applications in smart sensors [ 97 ]. Hembury and collaborators showed a synthetic pathway that combined gold nanoclusters with thermo-sensitive diblock copolymers of poly(ethylene glycol) (PEG) and PNIPAm to form a new class of gold-polymer, micelle-forming, hybrid NP [ 98 ]. The thermo-sensitive polymers enhanced the native fluorescent signal of Au NPs.…”

“…( d ) Schematic representation and TEM image of Au-thermosensitive polymer (PEG-PNIPAm) nanohybrids. Reproduced with permission from [ 94 , 95 , 97 , 98 ]. Copyright American Chemical Society, 2015, 2014, 2017, 2018.…”