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Harnessing polymer grafting to control the shape of plasmonic nanoparticles
摘要： Matrix-free polymer grafted nanoparticles (NPs) are single component polymer nanocomposites (PNCs) for which the often reported severe aggregation of the conventional PNCs can be suppressed. For a given particle core, the size and shape of the polymer grafted nanoparticles can be controlled by the molecular weight of the polymer and its grafting density. However, the degree of homogeneity of one-component PNCs depends on the grafted chain molecular weight and grafting density, as well as on the shape of grafted NPs. Surface plasmon resonance enhanced dynamic light scattering from very dilute solutions, yielding both translational and rotational transport coefficients, complemented by UV–Vis extinction spectra, can detect deviations from spheres. Here, we report that poly(isobutylene)-grafted Ag NPs strongly deviate from the spherical shape and are modeled as prolate spheroids. This NP asphericity, due to inhomogeneous grafting, can impact the structure and properties of plasmonic PNCs in the solid state. Thus, characterizing this behavior is a crucial step prior to the formation of one-component PNCs.
关键词： shape control,polymer grafting,dynamic light scattering,UV–Vis extinction spectra,plasmonic nanoparticles
更新于2025-09-23 15:21:01
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Controlled Gold Nanoparticle Placement into Patterned Polydimethylsiloxane Thin Films via Directed Self-Assembly
摘要： An economically scalable and reproducible method to assemble nanoparticles (NPs) into ordered arrays with high fidelity remains a fundamental roadblock. Methods like directed self-assembly have shown the highest promise resulting in >85% density of NP-filled prepatterned polymer cavities. This work refines directed self-assembly by controlling the evaporation rate, substrate velocity (deposition rate), and NP diameter resulting in reproducible fabrication of ordered arrays with areas >2 mm × 2 mm and ~100% density of filled cavities. Measured optical spectra showed a blueshift in the localized surface plasmon resonance (LSPR) and surface lattice resonance (SLR) peaks with increasing NP density for both 100 and 150 nm gold (Au) NPs. Discrete dipole approximation (DDA), coupled dipole approximation (CDA), rapid semi-analytical CDA (rsa-CDA), and Mie theory simulations closely matched extinction per nanoparticle (extinction/NP) calculations for measured extinction spectra. An ordered array containing 150 nm AuNPs was used for comparison with rsa-CDA estimates using both polydimethylsiloxane (PDMS) and glass refractive indices (RI) resulting in peak location estimates within 1.7% and comparable relative increases in peak heights. Both the measured and simulated SLR peak heights were shown to significantly increase when the array was on glass as opposed to within PDMS.
关键词： directed self-assembly,extinction spectra,gold nanoparticles,surface lattice resonance,localized surface plasmon resonance
更新于2025-09-12 10:27:22