Low‐Temperature and Water‐Based Biotemplating of Nanostructured Foam‐Like Titania Films Using ß‐Lactoglobulin

Given the broad use of nanostructured crystalline titania films, an environmentally friendly and more sustainable synthesis route is highly desirable. Here, a water‐based, low‐temperature route is presented to synthesize nanostructured foam‐like crystalline titania films. A pearl necklace‐like nanostructure is introduced as tailored titania morphology via biotemplating with the use of the major bovine whey protein ß‐lactoglobulin (ß‐lg). It is shown that titania crystallization in a brookite‐anatase mixed phase is promoted via spray deposition at a comparatively low temperature of 120 °C. The obtained crystallites have an average grain size of (4.2 ± 0.3) nm. In situ grazing incidence small‐angle and wide‐angle X‐ray scattering (GISAXS/GIWAXS) are simultaneously performed to understand the kinetics of film formation and the templating role of ß‐lg during spray coating. In the ß‐lg:titania biohybrid composites, the crystal growth in semicrystalline titania clusters is sterically directed by the condensing ß‐lg biomatrix. Due to using spray coating, the green chemistry approach to titania‐based functional films can be scaled up on a large scale, which can potentially be used in photocatalytic processes or systems related to energy application. In situ GISAXS/GIWAXS performed during spray deposition of ß‐lactoglobulin:titania biohybrid composite films reveal that crystal growth in semicrystalline titania clusters is sterically directed by the condensing biomatrix. After UV treatment, foam‐like nanostructured titania films are realized at low temperatures from water.