Hydrophilic and Hydrophobic: Modified GeO₂ Aerogels by Ambient Pressure Drying

An ever-increasing number of applications of oxide aerogels places a high demand on wettability-tuning techniques. This work explores the possibility to cheaply prepare GeO₂ aerogels with controlled wettability by an ambient pressure drying (APD) method. GeO₂ aerogels are prepared via two synthetic routes. Surface modification is carried out by soaking the gels in a silylating agent solution; type and concentration of the modifier are optimized to achieve a large surface area. The aerogels have been characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, nitrogen adsorption and contact angle measurements. The effect of surface modification on the phase composition and particle size of the aerogels is described. In summary, the work provides a new cheap production method for the preparation of both hydrophobic and hydrophilic GeO₂ aerogels with contact angle varying from 30° to 141° and with surface area of 90-140 m²/g, which facilitates the expansion of their diverse applications. GeO₂ aerogel synthesis by APD is reported for the first time.