Light-enabled reversible self-assembly and tunable optical properties of stable hairy nanoparticles

Abstract

The ability to dynamically organize functional nanoparticles (NPs) via the use of environmental triggers (temperature, pH, light, or solvent polarity) opens up important perspectives for rapid and convenient construction of a rich variety of complex assemblies and materials with new structures and functionalities. Here, we report an unconventional strategy for crafting stable hairy NPs with light-enabled reversible and reliable self-assembly and tunable optical properties. Central to our strategy is to judiciously design amphiphilic star-like diblock copolymers comprising inner hydrophilic blocks and outer hydrophobic photoresponsive blocks as nanoreactors to direct the synthesis of monodisperse plasmonic NPs intimately and permanently capped with photoresponsive polymers. The size and shape of hairy NPs can be precisely tailored by modulating the length of inner hydrophilic block of star-like diblock copolymers. The perpetual anchoring of photoresponsive polymers on the NP surface renders the attractive feature of self-assembly and disassembly of NPs on demand using light of different wavelengths, as revealed by tunable surface plasmon resonance absorption of NPs and the reversible transformation of NPs between their dispersed and aggregated states. The dye encapsulation/release studies manifested that such photoresponsive NPs may be exploited as smart guest molecule nanocarriers. By extension, the star-like block copolymer strategy enables the crafting of a family of stable stimuli-responsive NPs (e.g., temperature- or pH-sensitive polymer-capped magnetic, ferroelectric, upconversion, or semiconducting NPs) and their assemblies for fundamental research in self-assembly and crystallization kinetics of NPs as well as potential applications in optics, optoelectronics, magnetic technologies, sensory materials and devices, catalysis, nanotechnology, and biotechnology.

Silver Metallic Cyclodextrin‐Core Star mPEG

“…From the viewpoint of molecular aggregation states, they may be unimolecular micelles, or multi‐molecular self‐assemblies (even ones with novel morphology) . Therefore, star polymers have found wide applications in some fields such as drug delivery, catalytic systems, and nanoreactors . With respect to construction of star polymers, β‐cyclodextrin (β‐CD) is widely used as the core, due to its 21 hydroxy groups for reactive sites.…”

Resolving Optical and Catalytic Activities in Thermoresponsive Nanoparticles by Permanent Ligation with Temperature‐Sensitive Polymers

“…TheSPR peak position red-shifted by 15 nm from 522 to 537 nm accompanied by ad ecrease in peak intensity and ab roadening in full-width-at-half-maximum (FWHM) upon heating, yet reversible upon cooling (see Figure S17b). [8,[30][31][32] Notably,t he deliberately introduced free linear PNIPAM chains can be readily removed completely by ultracentrifugation because of its much lower density than PNIPAM-capped Au NPs,a nd the precipitated PNIPAMcapped Au NPs can be re-dissolved in water with no visible change in the solution color and transparency,comparable to the original linear PNIPAM-free solution (see Figure S25b to S25a). [8,[30][31][32] Moreover,o wing to the screening of Au NPs embedded within the aggregate,their full illumination is restricted, resulting in ar educed SPR peak intensity.…”

“…Figure 3d presents the thermoresponsive optical properties of the PNIPAM-capped Au NP aqueous solution with as mall amount of free linear PNIPAM chains added (i.e., 0.081 mm). [8,[30][31][32] Moreover,o wing to the screening of Au NPs embedded within the aggregate,their full illumination is restricted, resulting in ar educed SPR peak intensity. Ther ed-shift and the peak broadening with temperature are due to the collective electromagnetic response of aggregated Au NPs to the incident light.…”

“…Among various systems, thermoresponsive NPs composed of thermally responsive polymers capped on the surface of functional NPs stand out as ap articularly interesting class of organic-inorganic hybrid nanomaterials.T hey render convenient tailoring of the plasmonic,m agnetic, semiconducting,a nd catalytic proper-ties by simply regulating temperature for use in controlled delivery,c atalysis,m olecule detection, and biological science. [4][5][6][7] However,t his approach requires ah igh selectivity between the inorganic NP core and the functional end-groups in grafted molecules, [8,9] leading to tedious synthetic procedures. [3] Among the several impressive routes to PNIPAM-capped NPs (e.g., Au, Ag and Fe 3 O 4 ), grafting-from/grafting-to approach represents the most commonly used technique.…”

Light-controllable viscoelastic properties of a photolabile carboxybetaine ester-based polymer with mucus and cellulose sulfate

“…The character of the interactions of these smart materials can be tuned by applying external stimuli such as pH, temperature, light, ionic strength, or electrical or magnetic field. Application of light as a noninvasive trigger has been increasingly utilized since it can be initiated in a timely and spatially located manner and is compatible highly delicate bioactive species [2][3][4].…”