Fluorescence Switchable Block Copolymer Particles with Doubly Alternate‐Layered Nanoparticle Arrays

Abstract

The precise self‐assembly of block copolymers (BCPs) and inorganic nanoparticles (NPs) under 3D confinement offers microparticles with programmable nanostructures and functionalities. Here, fluorescence‐switchable hybrid microspheres are developed by forming doubly alternating arrays of Au NPs and CdSe/ZnS quantum dots (QDs) within polystyrene‐block‐poly(4‐vinylpyridine) (PS‐b‐P4VP) BCP domains. These doubly alternating arrays afford controlled nonradiative energy transfer (NRET) between the QDs and Au NPs that is dependent on the layer‐to‐layer distance. Solvent‐selective swelling of the hybrid particles tunes the distance between layers, modulating their NRET behavior and affording switchable fluorescence. The particle fluorescence is “OFF” in water through strong NRET from the QDs to Au NPs, but is “ON” in alcohols due to the increased distance between the Au NP and QD arrays in the swollen P4VP domains. The experimentally observed NRET intensity as a function of interparticle distance shows larger quenching efficiencies than those theoretically predicted due to the enhanced quenching within a 3D‐confined system. Finally, the robust and reversible fluorescence switching of the hybrid particles in different solvents is demonstrated, highlighting their potentials for bioimaging, sensing, and diagnostic applications.

Poly(vinylpyridine)-containing block copolymers for smart, multicompartment particles

“…The NPs segregated to their respective PS or P4VP domain, and the resulting hybrid particles exhibited solvent-responsive, fluorescence-switchable properties. 156 Upon swelling of the P4VP domain, the fluorescence was turned on due to the increased interparticle distance between the Au NP and QD, which effectively prevented fluorescent quenching through nonradiative energy transfer (NRET). The reversible fluorescence activity in different solvent systems highlighted their potential for bioimaging and sensing applications.…”

Shaping Block Copolymer Microparticles by Positively Charged Polymeric Nanoparticles

“…[11][12][13][14][15] Generally, varying the property of surfactant at the oil-water interface can change the interfacial tension and interfacial selectivity, thereby inducing the DOI: 10.1002/marc.202200143 deformation of the soft emulsion droplets, leading to the morphological transformation of the BCP microparticles. [16][17][18][19][20][21][22] In addition to amphiphilic molecules, nanoparticles (NPs) can also be used as surfactants to regulate the interfacial interactions and thus the 3D confined assembly of BCPs. For example, inorganic NPs, such as CuPt nanorods, [23] gold NPs, [24] graphene quantum dots, [25] and others, [26,27] have been used to shape BCP microparticles into different structures, including footballlike, [28] onion-like, [29,30] Janus pupa-like particles, [26] and others.…”

Light-Active, Reversibly Shape-Shifting Block Copolymer Particles Using Photo-switchable Au Nanoparticle Surfactants

“…Developing photoswitchable inorganic nanoparticles (NPs) in combination with azobenzene can provide additional important benefits for producing shape-changing BCP particles. Importantly, the structural complexity of BCPs can be exploited to confine NPs into desired locations, enhancing or suppressing the expression of the distinct physical properties of inorganic NPs through spatially controlled interactions with other constituents. − As surfactants, NPs are very effective for engineering the morphology and nanostructure of BCP particles due to their strong adsorption energy onto the interfaces, which can be tailored by tuning the size and shape of the NPs. − In addition, azobenzene can be combined with another type of ligand to modify NP surfaces and tune the hydrophilic–lipophilic balance (HLB) required to form stable oil-in-water emulsions. − Therefore, complicated synthetic procedures for preparing new azobenzene-based surfactants can be avoided simply by changing the ratio of the ligands on the NP surface. Furthermore, unlike organic surfactants, the NP distributions can be easily imaged using electron microscopy, which is advantageous to elucidate the mechanism of BCP particle formation and morphological transitions. , Therefore, the rational design of azobenzene-coated NP surfactants enables the development of reversible light-responsive BCP particles with wavelength-selective shapes and properties.…”