Antireflective Coatings for Glass and Transparent Polymers.

Antireflective coatings (ARCs) are applied to reduce surface reflections. We review coatings that reduce the reflection of the surface of the transparent substrates float glass, polyethylene terephthalate, poly(methyl methacrylate), and polycarbonate. Three main coating concepts exist to lower the reflection at the interface of a transparent substrate and air: multilayer interference coatings, graded index coatings, and quarter-wave coatings.

A study on the optics of copper indium gallium (di)selenide (CIGS) solar cells with ultra-thin absorber layers.

We present a systematic study of the effect of variation of the zinc oxide (ZnO) and copper indium gallium (di)selenide (CIGS) layer thickness on the absorption characteristics of CIGS solar cells using a simulation program based on finite element method (FEM). We show that the absorption in the CIGS layer does not decrease monotonically with its layer thickness due to interference effects. Ergo, high precision is required in the CIGS production process, especially when using ultra-thin absorber layers, to accurately realize the required thickness of the ZnO, cadmium sulfide (CdS) and CIGS layer.

Electric birefringence of dispersions of platelets.

This paper describes the electro-optic response of a suspension of disk-like colloids. We have considered aqueous suspensions of Gibbsite platelets and measured the electrically induced birefringence in the broad frequency range 10(2)-10(8) Hz. When simply dispersed in an electrolyte solution, these particles orient with their major axis parallel to the electric field at all frequencies.

Lyotropic hexagonal columnar liquid crystals of large colloidal gibbsite platelets.

We report the formation of hexagonal columnar liquid crystal phases in suspensions of large (570 nm diameter), sterically stabilized, colloidal gibbsite platelets in organic solvent. In thin cells these systems display strong iridescence originating from hexagonally arranged columns that are predominantly aligned perpendicularly to the cell walls. Small angle X-ray scattering and polarization microscopy indicate the presence of orientational fluctuations in the hexagonal columnar liquid crystal phase.

Sol-gel transitions and liquid crystal phase transitions in concentrated aqueous suspensions of colloidal gibbsite platelets.

In this paper, we present a comprehensive study of the sol-gel transitions and liquid crystal phase transitions in aqueous suspensions of positively charged colloidal gibbsite platelets at pH 4-5 over a wide range of particle concentrations (50-600 g/L) and salt concentrations (10(-4)-10(-1) M NaCl). A detailed sol-gel diagram was established by oscillatory rheological experiments. These demonstrate the presence of kinetically arrested states both at high and at low salt concentrations, enclosing a sol region.

Formation of nematic liquid crystals of sterically stabilized layered double hydroxide platelets.

Colloidal platelets of hydrotalcite, a layered double hydroxide, have been prepared by coprecipitation at pH 11-12 of magnesium nitrate and aluminum nitrate at two different magnesium to aluminum ratios. Changing the temperature and ionic strength during hydrothermal treatment, the platelets were tailored to different sizes and aspect ratios. Amino-modified polyisobutylene molecules were grafted onto the platelets following a convenient new route involving freeze-drying.

Synthesis and characterization of large surface hexagonal polyoxometalate platelets.

The polyoxometalates, or POMs (clusters comprising at least two metal and many oxygen atoms), have recently gained significant interest, owing to their versatile architecture and especially catalytic activities. Due to their high catalytic activity but low surface area, there is always a demand for making high-surface-area POMs, particularly high-surface-area Keggins. Our present work demonstrates the 'gluing' of the anionic phosphomolybdate Keggin on gibbsite nanoplatelets with a residual positive charge to form large-surface-area composites.

Shape-induced frustration of hexagonal order in polyhedral colloids.

The effect of a nonspherical particle shape and shape polydispersity on the structure of densely packed hard colloidal particles was studied in real space by confocal microscopy. We show that the first layer at the wall of concentrated size-monodisperse but shape-polydisperse polyhedral colloids exhibits significant deviations from a hexagonal lattice. These deviations are identified as bond-orientational fluctuations which lead to percolating "mismatch lines.