Elaborate Size‐Tuning of Silica Aerogel Building Blocks Enables Laser‐Driven Lighting

Abstract

Silica aerogels with accurate building‐block control are realized by adjusting the surfactant concentration during the synthesis process. The resulting silica‐aerogel monolith with spherical building blocks of ≈24–40 nm, together with a deliberately created hole along the incident light direction, shows an incredibly promising application in monochromatic laser‐driven lighting. The resulting coefficient of illuminance variation is as low as 8.1%, significantly outperforming commercially available ground‐glass diffusers (139.0%) and polymer diffusers (249.1%); the speckle contrast is lower, as well as better, than that can be recognized by the human eye (4%), and the illuminance uniformity in the range of 0.770–0.862 is much better (higher) than that indoor workplace lighting required by the International Organization for Standardization. Lighting with any color in the visible spectrum, including white, can be obtained by using three primary color lasers (450, 532, and 638 nm) with different powers simultaneously as the light source. The resulting silica aerogel, which has excellent thermal stability, high laser‐damage threshold, outstanding mechanical performance, and superhydrophobicity, can be further applied to long‐distance and noncontact laser‐driven lighting in rain or underwater without any additional encapsulation components.

Sonochemical Routes to Superhydrophobic Soft Matter Coatings: Comparing Silica and Copper Oxide Coatings on Polyester Fabric

“…68 No clear signals were obtained for silica samples, as is expected due to its low absorption of visible light. 92 For preformed CuO-NP, all sample peaks are asymmetric, indicating particle asymmetry which supports SEM image observations. A prominent peak at ∼210 nm is due to the characteristic direct optical absorption of cupric oxide while variations were explained by quantum confinement effects.…”

Bioinspired Multilayer Structures for Energy-Free Passive Heating and Thermal Regulation in Cold Environments

“…For example, (1) the transparency of the upper layer must be as high as possible to receive sunlight, while the thermal conductivity should be low to prohibit the heat loss to the cold environment by conduction and convection; (2) the photothermal conversion capacity of the PTCM is requested to be high; and (3) high latent heat of the PCM and comfortable temperature (20–60 °C) range of the phase change temperature is required. Interestingly, the highly transparent silica aerogels with ultralow thermal conductivity can be ideal candidates for the upper layer, which can be synthesized by the sol–gel method, where methyltrimethoxysilane (MTMS) was used as the precursor. − The photo images of the samples, including the transparent wet gel, solvent exchange, and the final sample, are shown in Figure S1A–C (Supporting Information); Figure E shows the photo image of the transparent silica aerogel, and the buildings behind the aerogel can be clearly seen. Due to Rayleigh scattering, the silica aerogel appears yellow in the backlight and blue in the front light (Figure S2, Supporting Information). , The aerogel was used as the upper layer to mimic the transparent, hydrophobic, and thermal insulation hair.…”

“…The silica aerogel monoliths were synthesized according to the literature. − First, MTMS, urea, and CTAB were mixed with an aqueous solution of acetic acid (5 mmol/L) in a molar ratio of 1:4:0.1 by stirring. After stirring at room temperature for 1 h, the homogeneous mixture was poured into molds, sealed, and left to stand in an oven at 60 °C for 3 days to complete the gelation and aging.…”

Preparation and Properties of Highly Transparent SiO2 Aerogels for Thermal Insulation

“…According to the Rayleigh-Gans theory, the smaller the size of the SiO 2 aerogels structural unit, the smaller the extinction coefficient and the higher the transmittance [ 41 ]. Therefore, the optical transparency of SiO 2 aerogels was related to the gel structure construction [ 41 , 42 ]. The optimization of composition and microstructure control are effective strategies to improve the high performance and multi-performance of SiO 2 aerogels [ 1 ].…”