Silver Mirror Reaction as an Approach to Construct Superhydrophobic Surfaces with High Reflectivity

Superhydrophobic surfaces with high reflectivity might provide a promising self-cleaning approach in a wide variety of optical applications ranging from traffic to solar energy industries. However, the contradiction between the hierarchical micronanostructure and the high reflectivity is a challenge for superhydrophobic materials with high reflectivity. Here we report a facile method to fabricate a superhydrophobic silver film with reflectivity as high as that of polished silicon by carefully controlling the seed-induced silver mirror reaction

Silver Mirror Reaction as an Approach to Construct Superhydrophobic Surfaces with High Reflectivity

Superhydrophobic surfaces with high reflectivity might provide a promising self-cleaning approach in a wide variety of optical applications ranging from traffic to solar energy industries. However, the contradiction between the hierarchical micronanostructure and the high reflectivity is a challenge for superhydrophobic materials with high reflectivity. Here we report a facile method to fabricate a superhydrophobic silver film with reflectivity as high as that of polished silicon by carefully controlling the seed-induced silver mirror reaction

Silver Mirror Reaction as an Approach to Construct Superhydrophobic Surfaces with High Reflectivity

Superhydrophobic surfaces with high reflectivity might provide a promising self-cleaning approach in a wide variety of optical applications ranging from traffic to solar energy industries. However, the contradiction between the hierarchical micronanostructure and the high reflectivity is a challenge for superhydrophobic materials with high reflectivity. Here we report a facile method to fabricate a superhydrophobic silver film with reflectivity as high as that of polished silicon by carefully controlling the seed-induced silver mirror reaction

Ion-Triggered Exfoliation of Layer-by-Layer Assembled Poly(acrylic acid)/Poly(allylamine hydrochloride) Films from Substrates: A Facile Way To Prepare Free-Standing Multilayer Films

A facile way to prepare sheet- and tubelike free-standing films of poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH) was developed by exfoliating PAA/PAH multilayer films from substrates in acid aqueous solution containing copper ions. The exfoliation of the PAA/PAH film from the substrate was achieved by breaking the electrostatic interaction of the PAA layer with the underlying substrate while keeping the integrity of the resultant films. Further study shows that thermally cross-linked free-standing PAA/PAH film can be prepared by treating the film in acid aqueous solution with a pH of 2.0. The ion-triggered exfoliation of PAA/PAH multilayer film provides a simple and flexible way to prepare layer-by-layer (LbL) assembled free-standing multilayer films

Patterning of Layer-by-Layer Assembled Organic−Inorganic Hybrid Films: Imprinting versus Lift-Off

Layer-by-layer (LbL) assembled organic−inorganic poly(acrylic acid) (PAA)/poly(allylamine hydrochloride) (PAH)/Au nanoparticle hybrid films are patterned by using Norland Optical Adhesive 63 (NOA 63) polymer molds. Depending on the rigidity of the hybrid films, their patterning can be realized by a room-temperature imprinting or lift-off process. For [(PAA/PAH)1-(Au nanoparticle/PAH)3]∗10 and [(PAA/PAH)3-(Au nanoparticle/PAH)3]∗5 films which have a low content of Au nanoparticles, the films can be imprinted at room temperature to form patterned films with large areas because of the compressibility and fluidity of the films under high pressure. The Au nanoparticle/PAH films, which have an extremely high content of Au nanoparticles and are fragile, can be patterned by a lift-off process during which the film contacted with the NOA 63 mold was peeled off because of the strong adhesion between the film and the mold and the fragility of the film. The complementary room-temperature imprinting and lift-off methods with polymer NOA 63 molds provide facile and general ways to pattern LbL assembled organic−inorganic films with various film compositions

Rings of Nanoparticle-Decorated Honeycomb-Structured Polymeric Film: The Combination of Pickering Emulsions and Capillary Flow in the Breath Figures Method

The self-assembly of nanoparticles at the fluid/fluid interface (Pickering emulsions) in the breath figures (BF) method have been explored to direct nanoparticles onto BF microarrays and adjust the BF assembly in microsize. Circular rings of nanoparticle-decorated honeycomb-structured polymeric film can be obtained by a one-step process. The combination of Pickering emulsions and capillary flow in the BF method may be responsible for the formation of this intriguing structure

Layer-by-Layer Deposition of Poly(diallyldimethylammonium chloride) and Sodium Silicate Multilayers on Silica-Sphere-Coated Substrate—Facile Method to Prepare a Superhydrophobic Surface

A facile method for preparing a superhydrophobic surface was developed by layer-by-layer (LbL) deposition of poly(diallyldimethylammonium chloride) (PDDA)/sodium silicate multilayer films on a silica-sphere-coated substrate followed with a fluorination treatment. First, a silica-sphere-coated substrate that contains loosely stacked silica spheres of 600 and 220 nm was prepared and cross-linked with SiCl4. PDDA was then alternately assembled with sodium silicate on the silica-sphere-coated surface to prepare a micro- and nanostructured hierarchical surface. Scanning electron microscopy (SEM) images verify that the deposition of a 5-bilayer PDDA/sodium silicate multilayer film leads to the formation of a micro- and nanostructured hierarchical surface. After chemical vapor deposition of a layer of fluoroalkylsilane, a superhydrophobic surface with a water contact angle of 157.1° and sliding angle of 3.1° was successfully fabricated. The easy availability of the materials and simplicity of this method might make the superhydrophobic surface potentially useful in a variety of applications

EMSA and Single-Molecule Force Spectroscopy Study of Interactions between <i>Bacillus subtilis</i> Single-Stranded DNA-Binding Protein and Single-Stranded DNA

In this article, interactions between Bacillus subtilis single-stranded DNA binding proteins (BsSSB) and single-stranded DNA (ssDNA) were systematically studied. The effect of different molar ratios between BsSSB and ssDNA on their binding modes was first investigated by electrophoretic mobility shift assays (EMSAs). It is found that a high molar ratio of BsSSB to ssDNA can produce BsSSB–ssDNA complexes formed in the mode of two proteins binding one 65-nt (nucleotide) ssDNA whereas a low molar ratio facilitates the formation of BsSSB–ssDNA complexes in the mode of one protein binding one 65-nt ssDNA. Furthermore, two binding modes are in dynamic equilibrium. The unbinding force of BsSSB–ssDNA complexes was measured quantitatively in solutions with different salt concentrations by using AFM-based single-molecule force spectroscopy (SMFS). Our results show that the unbinding force is about 10 pN higher at high salt concentration (0.5 M NaCl) than at low salt concentration (0.1 M NaCl) and the lifetime of BsSSB–ssDNA complexes at high salt concentration is twice as long as that at low salt concentration. These results indicate that more tightly packed BsSSB–ssDNA complexes can form at high salt (0.5 M NaCl) concentration. In addition, the results of EMSA show that ssDNA, which is bound to BsSSB, can dissociate from BsSSB in the presence of the cDNA strand, indicating the dynamic nature of BsSSB–ssDNA interactions

Mechanically Stable Antireflection and Antifogging Coatings Fabricated by the Layer-by-Layer Deposition Process and Postcalcination

Complexes of poly(diallyldimethylammonium chloride) (PDDA) and sodium silicate (PDDA−silicate) are alternately deposited with poly(acrylic acid) (PAA) to fabricate PAA/PDDA−silicate multilayer films. The removal of the organic components in the PAA/PDDA−silicate mulilayer films through calcination produces highly porous silica coatings with excellent mechanical stability and good adhesion to substrates. Quartz substrates covered with such porous silica coatings exhibit both antireflection and antifogging properties because of the reduced refractive index and superhydrophilicity of the resultant films. A maximum transmittance of 99.86% in the visible spectral range is achieved for the calcinated PAA/PDDA−silicate films deposited on quartz substrates. The wavelengths of maximum transmittance could be well tailored by simply changing the deposition cycles of multilayer films. The usage of PDDA−silicate complexes allows for the introduction of high porosity to the resultant silica coatings, which favors the fabrication of antireflection and antifogging coatings with enhanced performance. Meanwhile, PDDA−silicate complexes enable rapid fabrication of thick porous silica coatings after calcination because of the large dimensions of the complexes in solution. The easy availability of the materials and simplicity of this method for film fabrication might make the mechanically stable multifunctional antireflection and antifogging coatings potentially useful in a variety of applications

Metal Ionochromic Effects of Conjugated Polymers: Effects of the Rigidity of Molecular Recognition Sites on Metal Ion Sensing

The effects of the rigidity of molecular recognition sites in fluorene-based conjugated polymers P1 and P2 on metal ion sensing have been investigated. The structures of polymers P1 and P2 have twisted 2,2‘-bipyridine and planar 1,10-phenanthroline units, respectively, which alternate with one fluorene monomer unit. It is found that the absorption and emission bands of 1,10-phenanthroline-based polymer P2 exposed to metal ions can be red-shifted up to 30 nm, and emission intensity can be quenched up to 100%, depending on metal ions present, which is very similar to that of the 2,2‘-bipyridine-based analogue P1. However, polymer P2 shows much higher sensitivity to metal ions than P1. The origins of ionochromic effects of the 2,2‘-bipyridine-based conjugated polymer due to the metal ion chelation have been attributed to both conformational changes and electron density variations on the polymer chains caused by introducing positively charged metal ions (Chen et al. J. Phys. Chem., B 2000, 104, 1950−1960). On the basis of the comparison of P2 with P1, conformational changes are not required in the ion responsive process of the phen ion-recognition unit. We demonstrate that the electron density variations play more important roles in metal ion-induced red-shifts in absorption and fluorescence quenching in photoluminescence