Control of Specular and Diffuse Reflection of Light Using Particle Self‐Assembly at the Polymer and Metal Interface

Abstract

We present a novel method of controlling the specular and diffuse reflection of light by the electrostatic deposition of a spherical particle monolayer followed by electroless plating. Charged polystyrene colloidal particles, ranging in size from 100 nm to 5 μm, were adsorbed from solution onto oppositely charged polyelectrolyte multilayers (PEM). The monodisperse particle monolayers were coated with nickel in a two‐step electroless plating process using palladium catalysts. These surfaces can be used as diffusive metal reflectors with a uniformly controlled surface roughness due to the uniform size of deposited particles. In addition, the self‐assembled particles at the polymer and metal interface deflected the internal stresses that build‐up at the interface while the metal was being deposited. This allowed a thicker metal film to be deposited before delamination occurred. A UV‐VIS spectrometer with movable fiber optic cables was employed to characterize the optical properties of the reflectors. The optical fibers permit versatile and precise measurements of specular and diffuse reflectance. By measuring the angular dependent reflectance, we demonstrate how to estimate the distribution of reflected light from the nickel coated surface and how to calculate the ratio of specular and diffuse reflection in the total reflected light. Optical measurements of our nickel samples showed that this approach could be used to control the portion of diffuse reflection from 8.25 to 59.97 %. Additionally, a quartz crystal microbalance was employed to study the electroless nickel plating rate on PEM. Our proposed method is simple, cost‐effective and convenient for mass production because the process consists of a series of simple immersion steps without vacuum technology or special equipment.

Measuring the influence of UV reflection from vertical metal surfaces on humans

“…Alternatively, smooth surfaces could produce either specular or diffuse reflection, depending on the surface type. Research on this idea has been carried out 32 in other fields of study, but is not sufficient at present, to be able to define the particular reflecting behaviour of these metal surfaces. This would be an interesting study to pursue to better understand reflection of UV from metal surfaces in urban environments.…”

Effect of crystallinity on surface morphology and light transmittance of poly(vinylidene fluoride‐co‐hexafluoropropylene) thin film

“…Although some electrostrictive and mechanical properties enhanced, 25 the optical transmittance is expected to be deteriorated as increasing crystallinity of polymer films. The reduction in transmission intensity is mainly the result of light scattering at the surface or the bulk of semicrystalline film.…”

Biomimetic non-iridescent structural color materials from polydopamine black particles that mimic melanin granules

“…This phenomenon was most likely caused by the arrangement of the particles on the outermost surface layer. 31,32 In contrast, the rough surfaces on the interior of the plates were obtained (Fig. 4b.…”

“…4b. 31,32 The aforementioned results indicate that the textures of the structural color materials were controlled by the balance between the specular and diffuse reectance from the arrangement of PDA black particles. 30 Previous studies have shown that at surfaces made of colloidal materials increase the specular reectance and produce a metallic texture.…”