Arrays of Plasmonic Nanoparticles Assembled on Patterns of Polymer Brushes Fabricated by Soft Lithography

This work employed end-grafted poly ethylene glycol PEG and hydroxyl-terminated poly 2-vinylpyridine P2VP polymer chains for selective immobilization and patterning of plasmonic nanoparticles NPs . A soft lithographic method which called micromolding in capillaries MIMIC used in this study. The polymers are deposited the capillary flow by the channels which formed by an elastomeric mold and substrate. The localized coatings are referred as polymer brushes and show great promise in the assembly of NPs due to the tunable interaction between the polymer chains and particles. The results show that the width of patterns defined by the channels is smaller than 1.5 µm with a length of around 0.5 cm. Also, the heights of the patterns are ~3.5 nm for P2VP and ~10 nm for PEG. The fabricated structures exhibited high levels of plasmonic activity and surface enhanced Raman scattering due to the immobilized Au NPs. The patterning polymer brushes and plasmonic NPS over large areas by a low-cost process show great promise for a variety of applications that range from molecular sensors to biotechnolog

Assembly of Plasmonic Nanoparticles on Nanopatterns of Polymer Brushes Fabricated by Electrospin Nanolithography

This paper presents electrospin nanolithography (ESPNL) for versatile and low-cost fabrication of nanoscale patterns of polymer brushes to serve as templates for assembly of metallic nanoparticles. Here electrospun nanofibers placed on top of a substrate grafted with polymer brushes serve as masks. The oxygen plasma etching of the substrate followed by removal of the fibers leads to linear patterns of polymer brushes. The line-widths as small as ∼50 nm can be achieved by precise tuning of the diameter of fibers, etching condition, and fiber-substrate interaction. Highly aligned and spatially defined patterns can be fabricated by operating in the near-field electrospinning regime. Patterns of polymer brushes with two different chemistries effectively directed the assembly of gold nanoparticles and silver nanocubes. Nanopatterned brushes imparted strong confinement effects on the assembly of plasmonic nanoparticles and resulted in strong localization of electromagnetic fields leading to intense signals in surface-enhanced Raman spectroscopy. The scalability and simplicity of ESPNL hold great promise in patterning of a broad range of polymer thin films for different applications

Plasmonic assemblies of gold nanorods on nanoscale patterns of poly(ethylene glycol) : application in surface-enhanced Raman spectroscopy

Approaches are needed for the tailored assembly of plasmonic building blocks on the surface of substrates to synergistically enhance their properties. Here we demonstrate selective immobilization and assembly of gold nanorods (NRs) on substrates modified and patterned with end-grafted poly(ethylene glycol) (PEG) layers. The ligand exchange from the initial cetyltrimethylammonium bromide to sodium citrate was necessary for the immobilization of gold NRs onto PEG grafted substrates. Linear nanopatterns of PEG were fabricated using electrospun nanofibers as masks in oxygen plasma etching. The selective immobilization of citrate-stabilized gold NRs with a length of ∼50 nm and a width of 20 nm on the nanopatterned PEG layers led to linear and registered arrays of rods. The number of gold NRs per line depended on the width of the patterns and approached 1 when the width of the patterns was comparable to the length of the rods. The confinement of the binding regions led to a ∼3 fold increase in the number of gold NRs immobilized per unit area. The selective and dense immobilization of gold NRs on the nanoscale patterns of PEG resulted in spatially defined and strong surface-enhanced Raman scattering activity enabling detection of molecules at concentrations as low as 1 nM

Natural Wax-Stabilized Perovskite Nanocrystals as Pen-on-Paper Inks and Doughs

© 2022 American Chemical Society. All rights reserved.Perovskite nanocrystals (PNCs) are emerging luminescent materials for a wide range of technological applications. The broad adaptation of PNCs will be greatly improved by addressing their intrinsically low stability and developing processes for their assembly into 2D and 3D structures using facile approaches. Inspired by the mechanism of natural protection of leaves, this paper proposes natural carnauba wax (CW) as an encapsulation material for PNCs. The synthesis of PNCs is performed in the presence of CW, which is derived from the leaves of Copernicia prunifera palm. CW acts as a solvent and replaces the commonly used octadecene in the preparation of PNCs. The facile synthesis in CW results in PNCs with greatly improved thermal, water, and air stability. Furthermore, the thermal and mechanical properties make PNC-Wax a highly suitable solid ink for versatile processing of these materials into 2D and 3D architectures. PNC-Wax can be printed via a pen-on-paper approach by heating at modest temperatures. The rapid plasticization of PNC-Wax by mechanical agitation enables hand-shaping of the material in a manner similar to playdoughs, which would possibly enable the versatile use of this material for various applications