One-step-process composite colloidal monolayers and further processing aiming at porous membranes

Nanosphere lithography: the effect of chemical etching and annealing sequence on the shape and spectrum of nano-metal arrays

In this paper, it is shown that the sequence of chemical etching of the template and annealing has a significant effect on the shape and spectrum of the nano-metal arrays fabricated by nanosphere lithography (NSL). Higher nanoparticles with sharp edges are fabricated as a consequence of annealing the metal coated template, which is a 2d colloidal crystal, before chemical etching. Consequently, the absorption spectra of the fabricated sample become much sharper, in comparison with the one that is fabricated with the reversed order and also a shift is observed in the peak wavelength. The achieved result has practical importance for the applications of these nano-metal arrays in localized surface plasmon resonance (LSPR) based sensors.

Crosslinking of floating colloidal monolayers

Abstract

Crosslinked colloidal monolayers are promising as templates, lithographic masks, filtration membranes, or membranes for controlled release rates in drug delivery. We demonstrate assembly of monodisperse micron-sized polystyrene (PS) beads at an air/water interface, which are transformed into crystalline monolayers using addition of surface-active agents. Vapor annealing methods with solvents (toluene and xylene) and crosslinking agents (divinylbenzene) were investigated regarding their ability to crosslink these floating monolayers directly at the interface, generating crosslinked membranes with crystal size up to 44 cm², domain size up to 1.9 mm², and nano-sized pores (100–300 nm). The demonstrated fabrication method emphasizes short fabrication time using a simple setup.

Graphical abstract

Electronic supplementary material

The online version of this article (doi:10.1007/s00706-017-1997-6) contains supplementary material, which is available to authorized users.

2D-ordered dielectric sub-micron bowls on a metal surface: a useful hybrid plasmonic-photonic structure

Recently, it has been demonstrated that the combination of periodic dielectric structures with metallic structures provides an efficient means to yield a synergetic optical response or functionality in the resultant hybrid plasmonic-photonic systems. In this work, a new hybrid plasmonic-photonic structure of 2D-ordered dielectric sub-micron bowls on a flat gold surface was proposed, prepared, and theoretically and experimentally characterized. This hybrid structure supports two types of modes: surface plasmon polaritons bound at the metallic surface and waveguided mode of light confined in the cavity of bowls. Optical responses of this hybrid structure as well as the spatial electric field distribution of each mode are found to be strongly dependent on the structural parameters of this system, and thus could be widely modified on demand. Importantly, compared to the widely studied hybrid systems, namely the flat metallic surface coated with a monolayer array of latex spheres, the waveguided mode with strong field enhancement appearing in the cavities of bowls is more facilely accessible and thus suitable for practical use. For demonstration, a 2D-ordered silica sub-micron bowl array deposited on a flat gold surface was fabricated and used as a regenerable platform for fluorescence enhancement by simply accommodating emitters in bowls. All the simulation and experiment results indicate that the 2D-ordered dielectric sub-micron bowls on a metal surface should be a useful hybrid plasmonic-photonic system with great potential for applications such as sensors or tunable emitting devices if appropriate periods and materials are employed.