Mesoporous Metal Fluoride Nanocomposite Films with Tunable Optical Properties Derived from Precursor Instability

The precisely tailored refractive index of optical materials is the key to utilizing and manipulating light during its propagation through the matrix, thereby improving their application performances. In this paper, mesoporous metal fluoride films with engineered composition (MgF2:LaF3) are demonstrated to achieve finely tunable refractive indices. These films are prepared using a precursor-derived one-step assembly approach via the simple mixing of precursor solutions (Mg(CF3OO)(2) and La(CF3OO)(3)); then pores are formed simultaneously during solidification owing to the inherent instability of La(CF3OO)(3). The mesoporous structures are realized through Mg(CF3OO)(2) and La(CF3OO)(3) ions, which interacted with each other based on their electrostatic forces, providing a wide range of refractive indices (from 1.37 to 1.16 at 633 nm). Furthermore, it is systematically several MgF2(1-x)-LaF3(x) layers with different compositions (x = 0.0, 0.3, and 0.5) to form the graded refractive index coating that is optically consecutive between the substrate and the air for broadband and omnidirectional antireflection. An average transmittance of approximate to 98.03% (400-1100 nm) is achieved with a peak transmittance of approximate to 99.04% (at 571 nm), and the average antireflectivity is maintained at approximate to 15.75% even at an incidence of light of 65 degrees (400-850 nm).

Automated summary

In this paper, mesoporous metal fluoride films with precisely tunable refractive indices are prepared using a precursor-derived one-step assembly approach. The films exhibit a wide range of refractive indices (from 1.37 to 1.16 at 633 nm) due to the mesoporous structures formed through the interaction of Mg(CF3OO)(2) and La(CF3OO)(3) ions. Additionally, the authors create a gradient refractive index coating using multiple MgF2(1-x)-LaF3(x) layers, achieving high transmittance and antireflection properties.