Polymer nanocomposites with “ultralow” refractive index

Abstract

Nanocomposites of gelatine and gold were prepared by reduction of AuC1,H in a gelatine solution, followeu' by a spin coating process and a brief washing. The thickness of the films thus obtained was typically 200-400 nm. The surface of the nanocomposites was investigated by scanning electron microscopy (SEM) and surface profilometry. The size of the gold particles is in the range of ca. 2-10 nm, as elucidated by transmission electron microscopy (TEM). Refractive indices were measured by ellips o m e t y at wavelengths of 632.8 and 1300 nm. The refractive index depends linearly on the volume fraction of gold, at least at 1300 nm. The lowest refractive indices measured are 1.008_+0.060 at 1300 nm and 0.963 f 0.062 at 632.8 nm (limits are 95% confidence interval). These values are, to our best knowledge, the lowest reported for a polymer or polymer composite.

High Refractive Index Materials of Iron Sulfides and Poly(ethylene oxide)

“…Most samples were not suitable for refractive index measurements at 632.8 nm, probably because the lower wavelength is more sensitive to surface roughness. 7 For some samples, however, a refractive index could be obtained at 632.8 nm, the values also being around 2.0.…”

“…It may be expected that the refractive index increases with increasing fraction of inorganic filler, 5,7,28,29 and that it is, therefore, favorable to prepare composites with low polymer content, i.e., a polymer content just sufficient to obtain a "soft" material. However, the results do not show the expected refractive index dependence (within the experimental precision).…”

“…Nanocomposites with extremely high or low refractive index have been prepared recently by coprecipitation or spin-coating from aqueous solutions. [4][5][6][7] The high refractive index nanocomposites consist of colloidal lead sulfide embedded in a polymer matrix. Due to the high refractive index of PbS, that of the composites is up to 3, over a broad wavelength range, and to our knowledge by far the highest reported for a polymer composite.…”

Use of Lead (II) Sulfide Nanoparticles as Stabilizer for PMMA Exposed to Gamma Irradiation

“…Optical applications of polymers are often limited due to the relatively narrow range of the refractive index (RI) for high RI polymer nanocomposites, where the RI found is above 1.5. The RI values of most commercial polymers are typically around 1.3, while inorganic materials as PbS can possess RI above 3 11 . The RI found for PMMA-control and PMMA/PbS-NP films are shown in Figure 6.…”

“…This material can have specialized properties that cannot be found in their respective single phase and enhanced electrical, mechanical and optical properties have been reported. For example, the PbS nanoparticles can be embedded in polymer matrix to form high refractive index nanocomposite 11 . In this study, the refractive index of PbSgelation system increases from 1.5 to 2.5 with increasing PbS ratio.…”