Fabrication and characterization of superhydrophobic Sb(2)O(3) films

Engineering of physical properties of spray-deposited nanocrystalline Sb2O3 thin films by phase transformation

Nanostructured Sb₂O₃ thin films have been deposited onto glass substrates by using the chemical spray pyrolysis technique, and the effect of precursor solution volume on the physical properties was investigated for the first time. The prepared films were characterized in detail by using x-ray diffraction, field-emission scanning electron microscopy with energy dispersive x-ray analysis (FESEM-EDAX), UV-vis absorption and transmission spectroscopy, Raman spectroscopy analysis and electrical resistivity measurement. X-ray diffraction analysis shows that the senarmontite cubic phase is completely transferred to the valentinite orthorhombic phase as the precursor solution volume is increased. This phase transformation as a function of precursor volume is discussed in detail. The FESEM-EDAX analysis reconfirms the phase change showing well-defined nano-dimensional cubic hexagonal and orthorhombic octahedral morphologies with excellent stoichiometry. The optical property studies show that the bandgap energy of Sb₂O₃ varies from 3.43-3.98 eV as a function of precursor quantity. The as-grown Sb₂O₃ thin films are semiconducting in nature. The measured values of electrical resistivity and activation energy are found to be dependent on the spray solution volume. The electrical resistivity of deposited Sb₂O₃ thin films shows variation from 26.15 × 10²-34.27 × 10² Ω cm and the activation energy of the films is in the order of 0.763-0.773 eV.

Advanced Artificial Electronic Skin Based pH Sensing System for Heatstroke Detection

Heatstroke is a serious illness that can potentially damage many victims every year. Many intelligent physical sensors have been developed to prevent heatstroke fatalities. However, it remains a challenge to fabricate skin-adhesive, small, and low-cost sensors for in situ heatstroke detection to overcome the weaknesses of the physical sensors. As far as we know, this is the first breakthrough for exploiting a PDMS based freestanding nanosheet skin patch consisting of pH sensing elements (antimony/antimony oxide and silver/silver iodate) to achieve high pH sensitivity and repeatability. The sensing elements were investigated for structural and morphological properties. The easy to use and easy to fabricate nanosheet sensor exhibited a linear pH response of -43 mV/pH. Overall, the developed sensor showed high sensitivity, repeatability, and stability. Our initial results indicate that the developed sensor adhered well to a skin surface. It is expected that this proof of concept approach gives reliable fabrication and measurement unlike other physical sensors.

In situ assembly of raspberry- and mulberry-like silica nanospheres toward antireflective and antifogging coatings

Raspberry- and mulberry-like hierarchically structured silica particulate coatings were fabricated via facile in situ layer-by-layer assembly with monodisperse silica nanoparticles (NPs) of two different sizes followed by calcination. Raspberry-like and mulberry-like silica particulate coatings were achieved when the size ratio of two silica particles was 20/200 and 20/70 nm, respectively. The latter coating exhibited good antireflective property. Its maximum transmittance reached as high as 97%, whereas that of the glass substrate is only 91%. The morphologies of the coatings were observed by scanning electron microscopy and atom force microscopy. The surface properties of these coatings were investigated by measuring their water contact angles and the spreading time of water droplet. The results showed that such hierarchically structured coatings had superhydrophilic and antifogging properties.

Superhydrophobic gecko feet with high adhesive forces towards water and their bio-inspired materials

Functional integration is an inherent characteristic for multiscale structures of biological materials. In this contribution, we first investigate the liquid-solid adhesive forces between water droplets and superhydrophobic gecko feet using a high-sensitivity micro-electromechanical balance system. It was found, in addition to the well-known solid-solid adhesion, the gecko foot, with a multiscale structure, possesses both superhydrophobic functionality and a high adhesive force towards water. The origin of the high adhesive forces of gecko feet to water could be attributed to the high density nanopillars that contact the water. Inspired by this, polyimide films with gecko-like multiscale structures were constructed by using anodic aluminum oxide templates, exhibiting superhydrophobicity and a strong adhesive force towards water. The static water contact angle is larger than 150° and the adhesive force to water is about 66 μN. The resultant gecko-inspired polyimide film can be used as a "mechanical hand" to snatch micro-liter liquids. We expect this work will provide the inspiration to reveal the mechanism of the high-adhesive superhydrophobic of geckos and extend the practical applications of polyimide materials.