The construction of nano-sized, two-dimensionally ordered nanoparticle (NP) superstructures is important for various advanced applications such as photonics, sensing, catalysis, or nano-circuitry. Currently, such structures are fabricated using the templated organization approach, in which the templates are mainly created by photo-lithography or laser-lithography and other invasive top-down etching procedures. In this work, we present an alternative bottom-up preparation method for the controlled deposition of NPs into hierarchical structures. Lamellar polystyrene-block-poly(2-vinylpyridinium) thin films featuring alternating stripes of neutral PS and positively charged P2VP domains serve as templates, allowing for the selective adsorption of negatively charged gold NPs. Dense NP assembly is achieved by a simple immersion process, whereas two-dimensionally ordered arrays of NPs are realized by microcontact printing (μCP), utilizing periodic polydimethylsiloxane wrinkle grooves loaded with gold NPs. This approach enables the facile construction of hierarchical NP arrays with variable geometries
Electrostatic attraction between charged nanoparticles and oppositely charged nanopatterned polymeric films enables tailored structuring of functional nanoscopic surfaces. The bottom-up fabrication of organic/inorganic composites for example bears promising potential toward cheap fabrication of catalysts, optical sensors, and the manufacture of miniaturized electric circuitry. However, only little is known about the time-dependent adsorption behavior and the electronic or ionic charge transfer in the film bulk and at interfaces during nanoparticle assembly via electrostatic interactions. In situ electrochemical impedance spectroscopy (EIS) in combination with a microfluidic system for fast and reproducible liquid delivery was thus applied to monitor the selective deposition of negatively charged gold nanoparticles on top of positively charged poly(2-vinylpyridinium) (qP2VP) domains of phase separated lamellar poly(styrene)-block-poly(2-vinylpyridinium) (PS-b-qP2VP) diblock copolymer thin films
A one-step soft lithography based pathway to manufacture aligned gold nanorod@poly-(N-isopropylacrylamide) (GNR@pNIPAM) hybrid chains with hexagonal arrangement of the nanorods and with an anisotropic optical response is presented. After demonstration of an efficient synthesis protocol, yielding uniform composite microgels in high concentration, a micromolding procedure using wrinkled polydimethylsiloxane (PDMS) templates to fabricate aligned hybrid chains is introduced. It is found that the self-assembled GNR@pNIPAM microgels inside the PDMS wrinkle grooves can be transferred onto solid substrates, on which they exhibit a hexagonal order, as confirmed by small-angle X-ray scattering. Further, it is shown that the application of minimized PDMS wrinkle dimensions aligns GNRs inside the pNIPAM microgels, and that the optical response of such molded assemblies is anisotropic.
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