We report preparation of highly transparent, flexible, and thermally stable superhydrophobic organically modified silica (ORMOSIL) aerogel thin films from colloidal dispersions at ambient conditions. The prepared dispersions are suitable for large area processing with ease of coating and being directly applicable without requiring any pre- or post-treatment on a variety of surfaces including glass, wood, and plastics. ORMOSIL films exhibit and retain superhydrophobic behavior up to 500 °C and even on bent flexible substrates. The surface of the films can be converted from superhydrophobic (contact angle of 179.9°) to superhydrophilic (contact angle of <5°) by calcination at high temperatures. The wettability of the coatings can be changed by tuning the calcination temperature and duration. The prepared films also exhibit low refractive index and high porosity making them suitable as multifunctional coatings for many application fields including solar cells, flexible electronics, and lab on papers.

A large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160°and 10°, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60°) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications.

In this paper, we present a facile, template-free sol-gel method to produce fluorescent and highly mesoporous organically modified silica (ORMOSIL) thin films for vapor phase sensing of TNT. An alkyltrifunctional, methyltrimethoxysilane MTMS precursor was used to impart hydrophobic behavior to gel network in order to form the spring back effect. In this way, porous films (up to 74% porosity) are obtained at ambient conditions. Fluorescent molecules are physically encapsulated in the ORMOSIL network during gelation. Fluorescence of the films was found to be stable even after 3 months, proving the successful fixing of the dye into the ORMOSIL network. The functional ORMOSIL thin films exhibited high fluorescence quenching upon exposition to TNT and DNT vapor. Fluorescence quenching responses of the films are thickness-dependent and higher fluorescence quenching efficiency was observed for the thinnest film (8.6% in 10 s). The prepared mesoporous ORMOSIL thin films have great potential in new sensor and catalysis applications.

We report the preparation of flexible and mechanically stable antireflective organically modified silica (ormosil) coatings at ambient conditions. Thin films are obtained from colloidal suspensions of ormosil gels which are prepared using methyltrimethoxysilane (MTMS) and tetraethyl orthosilicate (TEOS) monomers. The ormosil suspensions are directly applicable and suitable for the large-area deposition of nanoporous ormosil thin films. The nanoporosity of the films can be tuned by changing the monomer ratio of the starting solution. Thin films on flexible substrates retain their antireflective properties even after 100 cycles of excessive bending without a significant change in transmission. Furthermore, the films remained intact after water dripping and adhesive tape tests. In addition, thin films on glass substrates are found to exhibit antifogging properties after annealing at 600 °C for 30 min. The ease of fabrication and multifunctionality of these films make them ideal coatings for flexible electronic and optoelectronic devices, sensors, and solar cells. © 2012 The Royal Society of Chemistry

A ny surface with water contact angle larger than 150°and sliding angle lower than 5°is generally referred as a superhydrophobic surface. 1 Such extremely water repellent surfaces are attracting a great deal of interest because of their potential applications, including self-cleaning materials, waterproof textiles, and prevention of ice accumulation.2 To obtain a superhydrophobic surface, two conditions must be met; micrometerand/or nanometer-sized roughness and low surface energy. 3Lithographic methods, 4À6 chemical etching, 7À9 or deposition of micrometer-and/or nanometer-sized particles 10À14 have been usually applied for roughening the surfaces, followed by surface modification with low-surface-energy molecules such as hydrocarbons or fluorinated hydrocarbons. However, such multiplestep fabrication of superhydrophobic surface requires sophisticated equipments and is labor-intensive, which make them impractical for large-area fabrication.On the other hand, simple single-step coating from solutions where roughness and low-energy surfaces are obtained simultaneously can be more desirable. For example, phase separation in polymers, 15 electrospinning, 16,17 solÀgel methods, 18,19 and hybrid micro-and nano-particles prepared via co-condensation reactions 20,21 are promising for large-area fabrication of superhydrophobic surfaces. With this insight, we developed a facile single-step method to prepare superhydrophobic surfaces directly applying dispersions of fluorocarbon containing mesoporous silica nanoparticles. Previously, Wang et al. 20 also reported superhydrophobic surfaces from fluorinated silica particles. They prepared the particles via a modified St€ ober method 22 resulting in a nonporous structure. However, mesoporosity of particles can provide extra functionality to the coatings such as antireflection due to low effective refractive indices. Therefore, we used a surfactant template method 23 to obtain mesoporous particles.We prepared the fluorinated mesoporous silica nanoparticles (FMSNs) by respective condensation of tetraethyl orthosilicate (TEOS) and perfluorooctyltriethoxysilane (PFOTS) monomers in a one-pot reaction. Surfactant molecules form self-assembled templates, and silica monomers polymerize around these templates. First, TEOS was polymerized forming mesoporous silica nanoparticles (MSNs). Then, PFOTS molecules were added to form a fluorinated layer around these MSNs; thus enabling selective deposition of PFOTS molecules on the surface of MSNs. As-prepared FMSNs were found to be hydrophobic and formed liquid marbles, which are water droplets enwrapped with hydrophobic particles. 24À26 To prepare a superhydrophobic surface with FMSNs, we dispersed the particles in an organo-modified silica sol (OSS) (prepared by using methyltrimethoxy silane as precursor) which act as a binder and provide mechanical stability. 27 The dispersions of FMSNs and OSS were spin coated on glass substrates and heat treated to cure. The coatings have static water contact angles around 160°and water droplets easil...