Journal
INTERNATIONAL NANO LETTERS
Volume 7, Issue 4, Pages 257-265Publisher
SPRINGER INT PUBL AG
DOI: 10.1007/s40089-017-0216-0
Keywords
Transmittance; Aerogel; pH value; Structural properties; Optical properties
Categories
Funding
- National Science Foundation Nanostructured Materials for Energy Storage and Conversion (NESAC) IGERT program [1069138]
- National Science Foundation Nanostructured Materials for Energy Storage and Conversion (NESAC) IGERT [1069138]
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We have systematically studied the relationship between synthesis pH and morphological and optical properties of silica aerogels. We have determined through SEM and BET that there is a systematic correlation between the pH of the initial silica solution and the surface area, porosity, and pore size of the resulting aerogel. We find that optical transmittance, particularly its wavelength dependence (dispersion), is strongly governed by the microstructure and, therefore, synthesis pH. We have determined that the microstructure of the aerogels fall into three broad categories: monostructural, which is characterized by repeating elongated microstructural features; fractal, which shows a distinctive structure that is emulated on multiple length scales; and isotropic, which is characterized by having no distinct features in its microstructure. Simply by controlling the pH of the synthesis environment, we can tune the optical properties of silica aerogels through pH controlled the microstructural modification. We have found that pH = 1-5 gives high dispersion, pH = 6-7 results in low transmittance and low dispersion, pH = 8 shows the highest transmittance with the lowest dispersion, and pH = 9-10 transitions back to lower transmittance and higher dispersion.
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