Structural Evolution of Nanophase Separated Block Copolymer Patterns in Supercritical CO2

Nanopatterns can readily be formed by annealing block copolymers (BCPs) in organic solvents at moderate or high temperatures. However, this approach can be challenging from an environmental and industrial point of view. Herein, we describe a simple and environmentally friendly alternative to achieve periodically ordered nanoscale phase separated BCP structures. Asymmetric polystyrene-b-poly(ethylene oxide) (PS-b-PEO) thin film patterns of different molecular weight were achieved by annealing in supercritical carbon dioxide (sc-CO2). Microphase separation of PS-b-PEO (16,000–5000) film patterns were achieved by annealing in scCO2 at a relatively low temperature was previously reported by our group. The effects of annealing temperature, time and depressurisation rates for the polymer system were also discussed. In this article, we have expanded this study to create new knowledge on the structural and dimensional evolution of nanohole and line/space surface periodicity of four other different molecular weights PS-b-PEO systems. Periodic, well defined, hexagonally ordered films of line and hole patterns were obtained at low CO2 temperatures (35–40 °C) and pressures (1200–1300 psi). Further, the changes in morphology, ordering and feature sizes for a new PS-b-PEO system (42,000–11,500) are discussed in detail upon changing the scCO2 annealing parameters (temperature, film thickness, depressurization rates, etc.). In relation to our previous reports, the broad annealing temperature and depressurisation rate were explored together for different film thicknesses. In addition, the effects of SCF annealing for three other BCP systems (PEO-b-PS, PS-b-PDMS, PS-b-PLA) is also investigated with similar processing conditions. The patterns were also generated on a graphoepitaxial substrate for device application.

Manufacture Porous Materials by Dabco-Based Lonic Liquid

The long-chain ionic liquid (IL) hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide was used as a template to prepare the hexagonally ordered siliceous mesoporous molecular sieve MCM-41 as well as the disordered mesoporous molecular sieve designated as KIT-1. The synthesized products were studied via X-ray diffraction (XRD), Fourier transform infrared (FTIR) and N2 adsorption-desorption analysis. The surface area (BET), pore volume, and pore diameter (BJH) are determined. These kind of ILs that have DABCO (1,4-diazabicyclo[2.2.2]octane) in their structures, were prepared with an easy method. When the two templates, cetyltrimethylammonium bromide (CTAB) and IL, have the similar structures, MCM-41 mesoporous molecular sieve produced with more ordered, uniform mesoporous channel and high surface area in comparison to without IL. When just IL used instead of CTAB, the KIT-1 with non-uniform mesoporous was obtained. Here we prepared the KIT-1 mesoporous molecular sieve with IL without CTAB but it seems, using dual template with changing IL structures in fabricated of molecular sieve provide new opportunity to design targeted adsorbents and catalysis.

A nanomesh electrode for self-driven perovskite photodetectors with tunable asymmetric Schottky junctions

We report a new device architecture for self-driven photodetectors with tunable asymmetric Schottky junctions based on a nanomesh electrode. It is composed of a hexagonally ordered nanoelectrode array fabricated via the nanosphere lithography technique.

Parametric scheme for rapid nanopattern replication via electrohydrodynamic instability

1/τm-dependent electrohydrodynamic replication of a hexagonally ordered hole array nanopattern by adjusting the filling ratio. As the 1/τm increases, the morphology evolves into the perfectly replicated hole features with increasing filling ratio.

Mesoporous Silica as a Drug Delivery System for Naproxen: Influence of Surface Functionalization

In this work we describe the relationship between surface modification of hexagonally ordered mesoporous silica SBA-15 and loading/release characteristics of nonsteroidal anti-inflammatory drug (NSAID) naproxen. Mesoporous silica (MPS) was modified with 3-aminopropyl, phenyl and cyclohexyl groups by grafting method. Naproxen was adsorbed into pores of the prepared MPS from ethanol solution using a solvent evaporation method. The release of the drug was performed in buffer medium at pH 2 and physiological solution at pH 7.4. Parent MPSs as well as naproxen loaded MPSs were characterized using physicochemical techniques such as nitrogen adsorption/desorption, thermogravimetric analysis (TG), Zeta potential analysis, Fourier transform infrared spectroscopy (FT-IR), and elemental analysis. The amount of naproxen released from the MPSs into the medium was determined by high-performance liquid chromatography (HPLC). It was shown that the adsorption and desorption characteristics of naproxen are dependent on the pH of the solution and the surface functionalization of the host.

Solvent-Free Environmentally Benign Approach for the Selective Olefin Epoxidation Catalyzed by Mn(III)-Immobilized Mesoporous Nanoarchitectonics

Immobilization of transition metal complexes at the surface of 2D-hexagonal functionalized SBA-15 material is one of the promising strategies in designing an efficient catalytic system for the olefin epoxidation reaction. Here we have immobilized Mn(III) on the Schiff-base anchore 2D-hexagonally ordered functionalised mesoporous SBA-15 material. Powder X-ray diffraction (PXRD), N2-sorption and high resolution transmission electron microscopic (HRTEM) studies of the resulting SBA-15-SB-Mn material suggested 2D-hexagonally ordered porous nanostructure and X-ray photoelectron spectroscopy (XPS) analysis suggested the presence of surface bound Mn(III) species in this nanomaterial. This mesoporous material showed excellent performance in the selective catalytic oxidation of various alkenes to the corresponding epoxides in the presence of tert-butyl hydroperoxide (TBHP, 70% aqueous solution) as oxidant under solvent-free mild reaction conditions together with high recycling efficiency.

Cooperative particle rearrangements facilitate the self-organized growth of colloidal crystal arrays on strain-relief patterns

Strain-relief pattern formation in heteroepitaxy is well understood for particles with long-range attraction and is a routinely exploited organizational principle for atoms and molecules. However, for particles with short-range attraction such as colloids and nanoparticles, which form brittle assemblies, the mechanism(s) of strain-relief is not known. Here, we found that for colloids with short-range attraction, monolayer films on substrates with square symmetry could accommodate large compressive misfit strains through locally dewetted hexagonally ordered stripes. Unexpectedly, over a window of compressive strains, cooperative particle rearrangements first resulted in a periodic strain-relief pattern, which then guided the growth of laterally ordered defect-free colloidal crystals. Particle-resolved imaging of monomer dynamics on strained substrates also helped uncover cooperative kinetic pathways for surface transport. These processes, which substantially influenced the film morphology, have remained unobserved in atomic heteroepitaxy studies hitherto. Leaning on our findings, we developed a heteroepitaxy approach for fabricating hierarchically ordered surface structures.