Nanopatterned Self-Assembled Monolayers by Using Diblock Copolymer Micelles as Nanometer-Scale Adsorption and Etch Masks

Nanopatterned self-assembled monolayers (SAMs) are obtained from a simple, straight-forward procedure by using masks derived from monolayers of block copolymer micelles. The nanopatterned SAMs consist of regularly spaced circular hydrophilic areas with diams. of approx. 60 nm on a continuous hydrophopic background or vice versa. The surfaces are shown to be excellent tools for the prepn. of arrays of nanocrystal

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Gold nanoring arrays from responsive block copolymer templates

We report a pH-mediated synthetic route for the production of ordered and size-tuneable arrays of gold nanorings using responsive block copolymer micelles as templates

Mimerbladet September 2014

The controlled tuning of the characteristic dimensions of two-dimensional arrays of block-copolymer reverse micelles deposited on silicon surfaces is demonstrated. The polymer used is polystyrene-block-poly(2-vinylpyridine) (91 500-b-105 000 g mol-1). Reverse micelles of this polymer with different aggregation numbers have been obtained from different solvents. The periodicity of the micellar array can be systematically varied by changing copolymer concentration, spin-coating speeds, and by using solvent mixtures. The profound influence of humidity on the micellar film structure and the tuning of the film topography through control of humidity are presented. Light scattering, at. force microscopy, SEM, transmission electron microscopy, and XPS were used for characterization. As possible applications, replication of micellar array topography with polydimethylsiloxane and post-loading of the micelles to form iron oxide nanoparticle arrays are presented

Hierarchical positioning of gold nanoparticles into periodic arrays using block copolymer nanoring templates

We report a simple and versatile self-assembly method for controlling the placement of functional gold nanoparticles on silicon substrates using micellar templates. The hierarchical positioning of gold nanoparticles is achieved in one-step during the spontaneous phase inversion of spherical poly(styrene)block-poly(2-vinylpyridine) copolymer micelles into nanoring structures. The placement is mainly driven by the establishment of electrostatic interactions between the nanoparticle ligands and the pyridine groups exposed at the interface. In particular, we show the formation of ordered arrangements of single gold nanoparticles or nanoparticle clusters and demonstrate that their morphologies, densities and periodicities can be tuned by simply varying the initial block copolymer molecular weight or the deposition conditions. Besides gold nanoparticles, the method can be used for controlling the assembly of a large variety of nanoscale building blocks, thus opening an attractive pathway for generating functional hybrid surfaces with periodic nanopatterns. (C) 2011 Elsevier Inc. All rights reserved

Micrometer-long gold nanowires fabricated using block copolymer templates

Micrometer-long gold nanowires were fabricated via self-assembly. Diblock copolymer films served as templates for the selective adsorption of 10 nm gold nanoparticles from solution to form well-defined nanostructures. An oxygen plasma treatment induced aggregation of the nanoparticles and the formation of continuous gold nanostructures. The electrical continuity of the nanostructures was observed using scanning electron microscopy

Controlling Mesopore Size and Processability of Transparent Enzyme-Loaded Silica Films for Biosensing Applications

Silica-based nanoporous thin films including large mesopores are relevant as enzyme supports for applications in biosensing. The diffusion and immobilization of large biomolecules such as enzymes in such porous films require the presence of large mesopores. Creating such morphologies based on a bottom-up synthesis using colloidal templates is a challenge in view of the combination of desired material properties and the robustness of the casting process for the fabrication of thin films. Here a strategy to reproducibly synthesize transparent porous silica thin films with submicrometer thickness and homogeneously distributed porosity is presented. For this purpose, polystyrene-poly-2-vinylpyridine (PS-P2VP) amphiphilic block copolymers are used as porogenic templates. Low-chain alcohols are employed as both selective solvents for the P2VP blocks and reaction media for silica synthesis. Rheology measurements reveal a strong influence of the block copolymer length on the behavior of PS-P2VP micelles in suspension. The pore distribution and accessibility into the film are controlled by adjusting the silica to block copolymer weight ratio. The solvent choice is shown to control not only the micelle size and the generated pore morphology but also the structural homogeneity of the films. Finally, the suitability of the synthesized films as supports for enzymes is tested using a model enzyme, horseradish peroxidase EC 1.11.1.7. Our approach is innovative, robust, and reproducible and provides a convenient alternative to synthesize large mesopores up to small macropores (20100 nm) in nanostructured thin films with applications in biosensing and functional coatings

Transparent and Robust Silica Coatings with Dual Range Porosity for Enzyme-Based Optical Biosensing

Hierarchically porous transparent silica coatings combine large specific surface area with enhanced pore accessibility for optical biosensing. This paper describes a versatile approach to fabricate optically transparent silica coatings with multiscale porosity. Thin films (around 1 mu m in thickness) of an aqueous suspension of primary silica aggregates form a mesoporous, interconnected matrix, and sacrificial polymer particles template well-defined, discrete macropores with high structural integrity. The total surface area achieved is around 200 m(2) g(-1) with mesopore sizes of 20-40 nm and macropores of 250 nm, with a total porosity of 84%. The macro/meso dual range of porosity allows enhanced biocatalyst loadings of l-lactate dehydrogenase for detection of lactate. The functionalized films showed a linear response within the range of interest of 1-20 x 10(-3) m of lactate. These biosensing coatings therefore strongly enhance sensitivity, speed and reliability of optically based lactate detection as compared to classical thin films with monomodal mesopore structure. Particle-based simulations and experiments reveal that both the location and connectivity of the macropores control the biosensing performance. The coatings and procedure presented here are versatile, scalable, inexpensive, and are therefore compatible with a wide range of deposition techniques suitable for industrial and health care applications

The influence of nanoparticle fillers on the morphology of a spin-cast thin film polymer blend

Polymer/nanoparticle composite films are receiving growing attention thanks to their potential for application in ultra-thin electronic and optical devices. Polymer blend demixing has been shown to be a suitable technique for the structuring of polymer thin films and the patterning of nanoparticles (NP) within them. In this work we show that the morphology of thin polymer films made by spin-casting a polymer blend solution containing NP fillers on a surface depends strongly on the concentration of NP fillers. More specifically, polystyrene/polymethylmethacrylate (PS/PMMA) films formed from a toluene solution, and which demix following a nucleation and growth mechanism, were studied. It was found that both the height and the surface density of PMMA domains increased as the concentration of CoPt:Cu NPs in the film was increased. We find that similar effects are induced in a NP-free PS/PMMA demixed film upon increasing the molecular weight of the PS molecules. This suggests that under certain conditions the NPs and the polymer molecules in the blend do not behave as separate species but form aggregates

Fabrication of nanopore arrays and ultrathin silicon nitride membranes by block-copolymer-assisted lithography

Here we show a method for patterning a thin metal film using self-assembled block-copolymer micelles monolayers as a template. The obtained metallic mask is transferred by reactive ion etching in silicon oxide, silicon and silicon nitride substrates, thus fabricating arrays of hexagonally packed nanopores with tunable diameters, interspacing and aspect ratios. This technology is compatible with integration into a standard microtechnology sequence for wafer-scale fabrication of ultrathin silicon nitride nanoporous membranes with 80 nm mean pore diameter